David Kipping: Alien Civilizations and Habitable Worlds

00:00:00.000 | I think it's actually not that hard to imagine we are the only civilization in the galaxy

00:00:03.880 | right now.

00:00:04.880 | Yeah, that's current extent.

00:00:07.720 | But there may be very many extinct civilizations.

00:00:10.680 | If each civilization has a typical lifetime comparable to, let's say AI is the demise

00:00:14.820 | of our own, that's only a few hundred years of technological development, or maybe 10,000

00:00:19.360 | years if you go back to the Neolithic Revolution, the dawn of agriculture.

00:00:24.280 | Hardly anything in cosmic time span.

00:00:27.400 | That's nothing.

00:00:28.400 | That's the blink of an eye.

00:00:29.400 | And so it's not surprising at all that we would happen not to coexist with anyone else.

00:00:34.480 | But that doesn't mean nobody else was ever here.

00:00:38.040 | And if other civilizations come to that same conclusion and realization, maybe they scour

00:00:43.800 | the galaxy around them, don't find any evidence for intelligence, then they have two options.

00:00:48.760 | They can either give up on communication and just say, "Well, it's never going to happen.

00:00:53.200 | We just may as well just worry about what's happening here on our own planet."

00:00:57.800 | Or they could attempt communication, but communication through time.

00:01:03.280 | The following is a conversation with David Kipping, an astronomer and astrophysicist

00:01:08.120 | at Columbia University, director of the Cool Worlds Lab.

00:01:12.440 | And he's an amazing educator about the most fascinating scientific phenomena in our universe.

00:01:19.120 | I highly recommend you check out his videos on the Cool Worlds YouTube channel.

00:01:24.800 | David quickly became one of my favorite human beings.

00:01:27.440 | I hope to talk to him many more times in the future.

00:01:31.480 | This is the Lex Riedman Podcast.

00:01:33.080 | To support it, please check out our sponsors in the description.

00:01:36.880 | And now, dear friends, here's David Kipping.

00:01:41.480 | Your research at Columbia is in part focused on what you call cool worlds, or worlds outside

00:01:47.160 | our solar system where temperature is sufficiently cool to allow for moons, rings, and life to

00:01:52.400 | form and for us humans to observe it.

00:01:55.080 | So can you tell me more about this idea, this place of cool worlds?

00:02:00.120 | Yeah.

00:02:01.120 | The history of discovering planets outside our solar system was really dominated by these

00:02:05.680 | hot planets.

00:02:06.680 | And that's just because of the fact they're easier to find.

00:02:09.840 | When the very first methods came online, these were primarily the Doppler spectroscopy method,

00:02:15.160 | looking for wobbling stars, and also the transit method.

00:02:18.960 | And these two both have a really strong bias towards finding these hot planets.

00:02:23.920 | Now hot planets are interesting.

00:02:26.160 | The chemistry in their atmosphere is fascinating.

00:02:28.280 | It's very alien.

00:02:30.280 | An example of one that's particularly close to my heart is TrES-2b, whose atmosphere is

00:02:35.560 | so dark it's less reflective than coal.

00:02:38.360 | And so they have really bizarre photometric properties, yet at the same time they resemble

00:02:44.480 | nothing like our own home.

00:02:46.820 | And so it's said there's two types of astrophysicists.

00:02:49.640 | The astrophysicists who care about how the universe works.

00:02:52.500 | They want to understand the mechanics of the machinery of this universe.

00:02:56.560 | Why did the Big Bang happen?

00:02:57.560 | Why is the universe expanding?

00:02:59.080 | How are galaxies formed?

00:03:00.640 | And there's another type of astrophysicist which perhaps speaks to me a little bit more.

00:03:06.100 | It whispers into your ear, and that is, "Why are we here?

00:03:10.160 | Are we alone?

00:03:11.160 | Are there others out there?"

00:03:12.880 | And ultimately along this journey, the hot planets aren't going to get us there.

00:03:17.120 | When we're looking for life in the universe, it seems to make perfect sense that there

00:03:20.560 | should be planets like our own out there.

00:03:23.360 | Maybe even moons like our own planet around gas giants that could be habitable.

00:03:28.120 | And so my research has been driven by trying to find these more tricolours globes that

00:03:32.700 | might resemble our own planet.

00:03:34.600 | - So they're the ones that lurk more in the shadows in terms of how difficult it is to

00:03:39.560 | detect.

00:03:40.560 | - They're much harder.

00:03:41.560 | They're harder for several reasons.

00:03:42.560 | The method we primarily use is the transit method, so this is really eclipses.

00:03:46.760 | As the planet passes in front of the star, it blocks out some starlight.

00:03:50.320 | The problem with that is that not all planets pass in front of their star.

00:03:53.260 | They have to be aligned correctly from your line of sight.

00:03:56.960 | And so the further away the planet is from the star, the cooler it is, the less likely

00:04:01.120 | it is that you're going to get that geometric alignment.

00:04:04.280 | So whereas a hot Jupiter, about 1% of hot Jupiters will transit in front of their star,

00:04:09.120 | only about 0.5%, maybe even a quarter of a percent of Earth-like planets will have the

00:04:14.440 | right geometry to transit.

00:04:16.760 | And so that makes it much, much harder for us.

00:04:18.800 | - What's the connection between temperature of the planet and geometric alignment, the

00:04:22.880 | probability of geometric alignment?

00:04:23.880 | - There's not a direct connection, but they're connected via an intermediate parameter, which

00:04:27.480 | is their separation from the star.

00:04:29.480 | So the planet will be cooler if it's further away from the star, which in turn means that

00:04:33.840 | the probability of getting that alignment correct is going to be less.

00:04:37.720 | On top of that, they also transit their star less frequently.

00:04:41.720 | So if you go to the telescope and you want to discover a hot Jupiter, you could probably

00:04:45.520 | do it in a week or so, because the orbital period is of order of one, two, three days.

00:04:49.360 | So you can actually get the full orbit two or three times over.

00:04:52.200 | Whereas if you want to detect an Earth-like planet, you have to observe that star for

00:04:56.160 | three, four years.

00:04:58.080 | And that's actually one of the problems with Kepler.

00:05:00.680 | Kepler was this very successful mission that NASA launched over a decade ago now, I think.

00:05:06.760 | And it discovered thousands of planets.

00:05:09.080 | It's still the dominant source of exoplanets that we know about.

00:05:12.680 | But unfortunately, it didn't last as long as we would have liked it to.

00:05:16.640 | It died after about 4.35 years, I think it was.

00:05:20.040 | And so for an Earth-like planet, that's just enough to catch four transits.

00:05:24.480 | Four transits was kind of seen as the minimum.

00:05:26.080 | But of course, the more transits you see, the easier it is to detect it, because you

00:05:30.320 | build up signal to noise.

00:05:31.640 | If you see the same thing, tick, tick, tick, tick, tick, the more ticks you get, the easier

00:05:35.560 | it is to find it.

00:05:36.600 | And so it was really a shame that Kepler was just at the limit of where we were expecting

00:05:41.600 | it to start to see Earth-like planets.

00:05:43.960 | And in fact, it really found zero.

00:05:46.840 | Zero planets that are around stars like the Sun, that orbit similar to the Earth around

00:05:51.360 | the Sun, and could potentially be similar to our own planet in terms of its composition.

00:05:56.480 | And so it's a great shame, but that's why it gives astronomers more to do in the future.

00:06:01.920 | - Just to clarify, the transit method is our primary way of detecting these things.

00:06:10.040 | And what it is, is when the object passes, occludes the source of light just a tiny bit,

00:06:18.240 | a few pixels, and from that we can infer something about its mass and size and distance and geometry

00:06:23.440 | and all of that.

00:06:25.080 | That's like trying to tell what, at a party, you can't see anything about a person, but

00:06:33.880 | you can just see by the way they occlude others.

00:06:36.920 | So this is the method.

00:06:37.920 | But is this super far away?

00:06:40.640 | How many pixels of information do we have?

00:06:44.160 | Basically how high resolution is the signal that we can get about these occlusions?

00:06:50.560 | - You're right in your description.

00:06:51.640 | I think just to build upon that a little bit more, it might be almost like your vision

00:06:55.720 | is completely blurry.

00:06:56.720 | Like you have an extreme eye prescription, and so you can't resolve anything.

00:07:01.920 | Everything's just blurs.

00:07:03.440 | But you can tell that something was there because it just got fainter for a short amount

00:07:07.120 | of time.

00:07:08.120 | Someone passed in front of a light.

00:07:09.520 | And so that light in your eyes would just dim for a short moment.

00:07:12.880 | Now the reason we have that problem with blowness or resolution is just because the stars are

00:07:17.360 | so far away.

00:07:18.360 | I mean, the closest stars are four light years away, but most of the stars Kepler looked

00:07:22.160 | at were thousands of light years away.

00:07:24.560 | And so there's absolutely no chance that the telescope can physically resolve the star,

00:07:30.120 | or even the separation between the planet and the star is too small, especially for

00:07:35.120 | a telescope like Kepler.

00:07:36.120 | It's only a meter across.

00:07:37.760 | In principle, you can make those detections, but you need a different kind of telescope.

00:07:43.480 | We call that direct imaging.

00:07:44.720 | And direct imaging is a very exciting, distinct way of detecting planets.

00:07:49.920 | But it, as you can imagine, is going to be far easier to detect planets which are really

00:07:54.040 | far away from their star to do that, because that's going to make that separation really

00:07:57.120 | big.

00:07:58.120 | And then you also want the star to be really close to us, so the nearest stars.

00:08:01.360 | Not only that, but you would prefer that planet to be really hot, because the hotter it is,

00:08:06.080 | the brighter it is.

00:08:07.840 | And so that tends to bias direct imaging towards planets which are in the process of forming.

00:08:12.120 | So things which have just formed, the planet's still got all of its primordial heat embedded

00:08:16.440 | within it, and it's glowing.

00:08:18.380 | We can see those quite easily.

00:08:20.020 | But for the planets more like the Earth, of course they've cooled down, and so we can't

00:08:23.360 | see that.

00:08:24.360 | The light is pitiful compared to a newly formed planet.

00:08:26.980 | We would like to get there with direct imaging.

00:08:29.240 | That's the dream, is to have the pale blue dot, an actual photograph of it, maybe even

00:08:33.640 | just a one pixel photograph of it.

00:08:35.760 | But for now, the entire solar system is one pixel, certainly with the transit method and

00:08:40.040 | most other telescopes.

00:08:41.440 | And so all you can do is see where that one pixel, which contains potentially dozens of

00:08:46.520 | planets, and the star, maybe even multiple stars, dims for a short amount of time.

00:08:51.120 | >> KOREY: It dims just a little bit, and from that you can infer something.

00:08:54.360 | >> ALISTAIR: Yeah, I mean it's like being a detective in the scene.

00:08:58.720 | It's indirect clues of the existence of the planet.

00:09:01.440 | >> KOREY: It's amazing that humans can do that.

00:09:03.320 | >> ALISTAIR: We're just looking out in these immense distances, and looking, you know,

00:09:08.640 | if there's alien civilizations out there, like let's say one exactly like our own, we're

00:09:14.520 | like, would we even be able to see an Earth that passes in the way of its sun and slightly

00:09:21.640 | dims?

00:09:22.640 | And that's the only sign we have of that alien human-like civilization out there, is it's

00:09:28.240 | just a little bit of a dimming.

00:09:29.480 | >> KOREY: Yeah.

00:09:30.640 | I mean, it depends on the type of star we're talking about.

00:09:32.520 | If it is a star truly like the sun, the dip that causes is 84 parts per million.

00:09:37.920 | I mean, it's like the same as a firefly flying in front of a giant floodlight at a stadium

00:09:44.760 | or something.

00:09:45.760 | That's kind of the brightness contrast that you're trying to compare to.

00:09:48.760 | So it's extremely difficult detection, and in the very, very best cases we can get down

00:09:54.520 | to that.

00:09:55.520 | But as I said, we don't really have any true Earth analogues that have been in the exoplanet

00:09:59.360 | candidate yet.

00:10:00.880 | Unless you relax that definition, you say it's not just, doesn't have to be a star just

00:10:05.040 | like the sun.

00:10:06.040 | It could be a star that's smaller than the sun.

00:10:07.440 | It could be these orange dwarfs or even the red dwarf stars.

00:10:11.240 | And the fact those stars are smaller means that for the same size planet passing in front

00:10:15.260 | of it, more light is blocked out.

00:10:17.360 | And so a very exciting system, for example, is TRAPPIST-1, which has seven planets which

00:10:23.020 | are smaller than the Earth.

00:10:25.560 | And those are quite easily detectable, not with a space-based telescope, but even from

00:10:29.640 | the ground.

00:10:30.640 | And that's just because the star is so much smaller that the relative increase in or decrease

00:10:34.840 | in brightness is enhanced significantly because of that smaller size.

00:10:38.440 | So TRAPPIST-1e, it's a planet which is in the right distance for liquid water.

00:10:42.840 | It has a slightly smaller size than the Earth.

00:10:45.040 | It's about 90% the size of the Earth, about 80% the mass.

00:10:48.760 | And it's one of the top targets right now for potentially having life.

00:10:53.720 | And yet it raises many questions about what would that environment be like?

00:10:59.480 | This is a star which is one-eighth the mass of the Sun.

00:11:04.720 | Stars like that take a long time to come off their adolescence.

00:11:09.040 | When stars first form, like the Sun, it takes them maybe 10, 100 million years to sort of

00:11:12.680 | settle into that main sequence lifetime.

00:11:15.480 | But for stars like these late M dwarfs, as we call them, they can take up to a billion

00:11:20.040 | years or more to calm down.

00:11:23.760 | And during that period, they're producing huge amounts of x-rays, ultraviolet radiation

00:11:28.360 | that could potentially rip off the entire atmosphere.

00:11:31.360 | It may desiccate the planets in the system.

00:11:34.280 | And so even if water arrived by comets or something, it may have lost all that water

00:11:38.840 | due to this prolonged period of high activity.

00:11:41.960 | So we have lots of open-ended questions about these M dwarf planets, but they are the most

00:11:47.600 | accessible.

00:11:48.600 | And so in the near term, if we detect anything in terms of biosignatures, it's going to be

00:11:54.760 | for one of these red dwarf stars, it's not going to be a true Earth twin, as we would

00:11:59.360 | recognize it as having a yellow star.

00:12:01.040 | LB: Well, let me ask you, I mean, there's a million ways to ask this question, I'm sure

00:12:05.000 | I'll ask it, about habitable worlds.

00:12:09.280 | Let's just go to our own solar system.

00:12:11.160 | What can we learn about the planets and moons in our solar system that might contain life?

00:12:18.560 | Whether it's Mars or some of the moons of Jupiter and Saturn, what kind of characteristics,

00:12:25.440 | because you said it might not need to be Earth-like, what kind of characteristics might we be looking

00:12:30.760 | for?

00:12:31.760 | CB: When we look for life, it's hard to define even what life is, but we can maybe do a better

00:12:37.240 | job in defining the sorts of things that life does.

00:12:40.720 | And that provides some aspects to some avenue for looking for them.

00:12:46.720 | Certainly classically, conventionally, I think we thought the way to look for life was to

00:12:50.560 | look for oxygen.

00:12:52.520 | Oxygen is a by-product of photosynthesis on this planet.

00:12:55.440 | We didn't always have it.

00:12:56.440 | Certainly if you go back to the Archean period, you have this period called the Great Oxidation

00:13:02.280 | Event where the Earth floats with oxygen for the first time and starts to saturate the

00:13:05.760 | oceans and then the atmosphere.

00:13:08.240 | And so that oxygen, if we detect it on another planet, whether it be Mars, Venus or an exoplanet,

00:13:13.320 | whatever it is, that was long thought to be evidence for something doing photosynthesis.

00:13:19.360 | Because if you took away all the plant life on the Earth, the oxygen wouldn't just hang

00:13:23.520 | around here as a highly reactive molecule.

00:13:26.600 | It would oxidize things, and so within about a million years you'd probably lose all the

00:13:30.480 | oxygen on planet Earth.

00:13:32.760 | So that was conventionally how we thought we could look for life.

00:13:35.960 | And then we started to realize that it's not so simple because a) there might be other

00:13:39.280 | things that life does apart from photosynthesis.

00:13:42.720 | Certainly the vast majority of the Earth's history had no oxygen, and yet there was living

00:13:46.080 | things on it, so that doesn't seem like a complete test.

00:13:50.200 | And secondly, could there be other things that produce oxygen besides from life?

00:13:55.000 | A growing concern has been these false positives in biosignature work.

00:14:00.000 | And so one example of that would be photolysis that happens in the atmosphere.

00:14:04.160 | An ultraviolet light hits the upper atmosphere, it can break up water vapor, the hydrogen

00:14:09.600 | splits off to the oxygen.

00:14:11.120 | The hydrogen is a much lighter atomic species, and so it can actually escape certainly planets

00:14:15.320 | like the Earth's gravity.

00:14:16.920 | That's why we don't have any hydrogen or very little helium.

00:14:19.960 | And so that leaves you with the oxygen, which then oxidizes the surface.

00:14:23.880 | And so there could be a residual oxygen signature just due to this photosynthesis process.

00:14:29.280 | So we've been trying to generalize, and certainly in recent years there's been other suggestions

00:14:34.520 | of things we could look for in the solar system beyond.

00:14:37.280 | Nitrous oxide, basically laughing gas, is a product of microbes.

00:14:42.280 | That's something that we're starting to get more interest in looking for.

00:14:45.520 | Methane gas in combination with other gases can be an important biosignature.

00:14:51.280 | Phosphine as well, and phosphine is particularly relevant to the solar system because there

00:14:55.080 | was a lot of interest for Venus recently.

00:14:59.000 | You may have heard that there was a claim of a biosignature in Venus's atmosphere, I

00:15:03.680 | think it was like two years ago now.

00:15:06.680 | And the judge and jury is still out on that.

00:15:09.760 | There was a very provocative claim and signature of a phosphine-like spectral absorption, but

00:15:18.240 | it could have also have been some other molecule in particular, sulfur dioxide, which is not

00:15:22.800 | a biosignature.

00:15:23.800 | LB: So this is a detection of a gas in the atmosphere, Venus.

00:15:28.600 | And it might be controversial in several dimensions.

00:15:33.120 | So one, how to interpret that?

00:15:35.640 | Two, is this the right gas?

00:15:37.040 | And three, is this even the right detection?

00:15:39.120 | Is there an error in the detection?

00:15:41.000 | CB: Yeah.

00:15:42.000 | I mean, how much do we believe the detection in the first place?

00:15:44.620 | If you do believe it, does that necessarily mean there's life there?

00:15:48.560 | And what gives?

00:15:50.120 | How can you have life in Venus's atmosphere in the first place?

00:15:52.840 | Because that's been seen as like a hellhole place for imagining life.

00:15:56.880 | But I guess the counter to that has been that, okay, yes, the surface is a horrendous place

00:16:01.880 | to imagine life thriving.

00:16:04.880 | But as you go up in altitude, the very dense atmosphere means that there is a cloud layer

00:16:09.560 | where the temperature and the pressure become actually fairly similar to the surface of

00:16:14.080 | the Earth.

00:16:15.080 | So maybe there are microbes stirring around in the clouds which are producing phosphine.

00:16:20.840 | At the moment, this is fascinating.

00:16:22.240 | It's got a lot of us reinvigorated about the prospects of going back to Venus and doing

00:16:28.640 | another mission there.

00:16:29.640 | In fact, there's now two NASA missions, Veritas and Da Vinci, which are going to be going

00:16:33.920 | back before 2030, or the 2030s.

00:16:37.940 | And then we have a European mission, I think, that's slated now.

00:16:40.160 | And even a Chinese mission might be coming along the way as well.

00:16:43.120 | So we might have multiple missions going to Venus, which has long been overlooked.

00:16:46.880 | I mean, apart from the Soviets, there really has been very little in the way of exploration

00:16:51.600 | of Venus.

00:16:52.600 | Certainly as compared to Mars.

00:16:54.240 | Mars has enjoyed most of the activity from NASA's rovers and surveys.

00:16:59.880 | And Mars is certainly fascinating.

00:17:01.480 | There's this signature of methane that has been seen there before.

00:17:06.360 | Again there, the discussion is whether that methane is a product of biology, which is

00:17:11.680 | possible, something that happens on the Earth, or whether it's some geological process that

00:17:16.640 | we are yet to fully understand.

00:17:19.080 | It could be, for example, a reservoir of methane that's trapped under the surface and is leaking

00:17:23.640 | out seasonally.

00:17:24.640 | - So the nice thing about Venus is if there's a giant living civilization there, it'll be

00:17:29.720 | airborne, so you can just fly through and collect samples.

00:17:34.520 | With Mars and moons of Saturn and Jupiter, you're going to have to dig under to find

00:17:41.360 | the civilizations, dead or living.

00:17:43.640 | - Right.

00:17:44.640 | And so maybe it's easier then for Venus, because certainly you can imagine just a balloon floating

00:17:48.240 | through the atmosphere, or a drone or something that would have the capability of just scooping

00:17:54.080 | up and sampling.

00:17:56.840 | To dig under the surface of Mars is maybe feasible-ish, especially with something like

00:18:02.920 | Starship that could launch a huge digger basically to the surface, and you could just excavate

00:18:08.760 | away at the surface.

00:18:10.360 | But for something like Europa, we really are still unclear about how thick the ice layer

00:18:16.200 | is, how you would melt through that huge thick layer to get to the ocean, and then potentially

00:18:22.960 | also discussions about contamination.

00:18:25.560 | The problem with looking for life in the solar system, which is different from looking for

00:18:29.040 | life with exoplanets, is that you always run the risk of, especially if you visit there,

00:18:34.080 | of introducing the life yourself.

00:18:36.400 | It's very difficult to completely exterminate every single microbe and spore on the surface

00:18:42.920 | of your rover or the surface of your lander, and so there's always a risk of introducing

00:18:48.520 | something.

00:18:49.520 | I mean, to some extent there is continuous exchange of material between these planets,

00:18:54.480 | naturally, on top of that as well, and now we're sort of accelerating that process to

00:18:57.840 | some degree.

00:18:58.840 | And so if you dig into Europa's surface, which probably is completely pristine, it's very

00:19:04.360 | unlikely there has been much exchange with the outside world for its subsurface ocean,

00:19:10.160 | you are for the first time potentially introducing bacterial spores into that environment that

00:19:15.560 | may compete or may introduce spurious signatures for the life you're looking for.

00:19:19.840 | And so it's almost an ethical question as to how to proceed with looking for life on

00:19:26.720 | those subsurface oceans, and I don't think we really have a good resolution for it at

00:19:32.520 | this point.

00:19:33.520 | - Ethical.

00:19:34.520 | So you mean ethical in terms of concern for preserving life elsewhere, not to murder it,

00:19:41.800 | as opposed to a scientific one?

00:19:43.040 | - I mean, we always worry about a space virus coming here or some kind of external source,

00:19:48.120 | and we would be the source of that potential contamination.

00:19:51.080 | - Or the other direction.

00:19:52.640 | - I mean, whatever survives in such harsh conditions might be pretty good at surviving

00:20:01.320 | in all conditions.

00:20:02.320 | It might be a little bit more resilient and robust, so it might actually take a ride on

00:20:06.280 | us back home.

00:20:08.120 | - Possibly.

00:20:09.120 | I mean, I'm sure that some people would be concerned about that.

00:20:11.760 | I think we would hopefully have some containment procedures if we did sample return, or you

00:20:18.000 | mean you don't even really need a sample return.

00:20:19.560 | These days you can pretty much send a little micro laboratory to the planet to do all the

00:20:23.800 | experiments in situ, and then just send them back to your planet, the data.

00:20:28.480 | And so I don't think it's necessary, especially for a case like that where you might have

00:20:33.120 | contamination concerns, that you have to bring samples back.

00:20:36.360 | Although, probably if you brought back European sushi, it would probably sell for quite a

00:20:41.280 | bit with the billionaires in New York City.

00:20:45.000 | - Sushi, yeah.

00:20:46.480 | I would love from an engineering perspective just to see all the different candidates and

00:20:51.520 | designs for the scooper, for Venus and the scooper for Europa and Mars.

00:20:57.320 | I haven't really looked deeply into how the actual engineering of collecting the samples,

00:21:03.040 | because the engineering of that is probably essential for not either destroying life or

00:21:10.480 | polluting it with our own microbes and so on.

00:21:13.480 | So that's an interesting engineering challenge.

00:21:16.000 | I usually for rovers and stuff focus on the sort of the mobility aspect of it, on the

00:21:22.040 | robotics, the perception, and the movement and the planning and the control.

00:21:26.040 | But there's probably the scooper is probably where the action is, the microscopic sample

00:21:31.040 | collection.

00:21:32.040 | So basically you have to first clean your vehicle, make sure it doesn't have any earth

00:21:37.240 | like things on it, and then you have to put it into some kind of thing that's perfectly

00:21:42.800 | sealed from the environment.

00:21:43.800 | So if we bring it back or we analyze it, it's not going to bring anything else externally.

00:21:49.760 | Yeah, I don't know.

00:21:51.440 | That would be an interesting engineering design there.

00:21:53.720 | - Yeah, I mean Curiosity has been leaving these little pods on the surface quite recently.

00:21:59.520 | There's some neat photos you can find online and they kind of look like lightsaber hilts.

00:22:05.200 | So yeah, to me, I think I tweeted something like, you know, this weapon is your life.

00:22:11.000 | Like don't lose it Curiosity, because it's just dumping these little vials everywhere.

00:22:14.760 | And it's yeah, it is scooping up these things.

00:22:16.960 | And the intention is that in the future there will be a sample return mission that will

00:22:21.120 | come and pick these up.

00:22:23.640 | But I mean, the engineering behind those things is so impressive.

00:22:25.960 | The thing that blows me away the most has been the landings.

00:22:30.600 | Especially I'm trained to be a pilot at the moment.

00:22:32.080 | So that's the sort of, you know, watching landings has become like my pet hobby on YouTube

00:22:35.440 | at the moment and how not to do it, how to do it with different levels of conditions

00:22:40.440 | and things.

00:22:41.440 | But when you think about landing on Mars, just the light travel time effect means that

00:22:46.760 | there's no possibility of a human controlling that descent.

00:22:51.280 | And so you have to put all of your faith and your trust in the computer code or the AI

00:22:56.880 | or whatever it is that you've put on board that thing to make the correct descent.

00:23:01.760 | And so there's this famous period called seven minutes of hell, where you're basically waiting

00:23:07.120 | for that light travel time to come back to know whether your vehicle successfully landed

00:23:11.000 | on the surface or not.

00:23:12.520 | And during that period, you know in your mind simultaneously that it is doing these multi

00:23:17.080 | stages of deploying its parachute, deploying the crane, activating its jets to come down

00:23:23.760 | and controlling its descent to the surface.

00:23:26.640 | And then the crane has to fly away so it doesn't accidentally hit the rover.

00:23:29.940 | And so there's a series of multi stage points where any of them go wrong, you know, the

00:23:35.600 | whole mission could go awry.

00:23:38.560 | And so the fact that we are fairly consistently able to build these machines that can do this

00:23:44.920 | autonomously is to me one of the most impressive acts of engineering that NASA have achieved.

00:23:51.080 | - Yes, the unfortunate fact about physics is the takeoff is easier than the landing.

00:23:57.280 | And you mentioned Starship, one of the incredible engineering feats that you get to see is the

00:24:03.040 | reusable rockets that take off but they land and they land using control and they do so

00:24:09.200 | perfectly and sometimes when it's synchronous, it's just it's beautiful to see.

00:24:13.320 | And then with Starship, you see the chopsticks that catch the ship.

00:24:16.480 | I mean, there's so much incredible engineering, but you mentioned Starships is somehow helpful

00:24:22.400 | here.

00:24:23.400 | So what's your hope with Starship?

00:24:24.760 | What kind of science might it enable possibly?

00:24:29.360 | - There's two things.

00:24:30.360 | The launch cost itself, which is hopefully going to mean per kilogram, it's going to

00:24:33.520 | dramatically reduce the cost of it.

00:24:36.200 | Even if it's a factor of 10 higher than what Elon originally promised, this is going to

00:24:39.880 | be a revolution for the cost to launch.

00:24:42.760 | That means you could do all sorts of things.

00:24:44.080 | You could launch large telescopes, which could be basically like JWST, but you don't even

00:24:50.320 | have to fold them up.

00:24:51.320 | JWST had this whole issue with its design that it's six and a half meters across.

00:24:55.920 | And so you have to, there's no fuselage, which is that large at the time, the Ares 4 wasn't

00:25:00.120 | large enough for that.

00:25:01.120 | And so they had to fold it up into this kind of complicated origami.

00:25:04.760 | And so a large part of the cost was figuring out how to fold it up, testing that it unfolded

00:25:10.400 | correctly, repeated testing.

00:25:12.640 | And there was something like 130 fail points or something during this unfolding mechanism.

00:25:17.800 | And so all of us were holding our breath during that process.

00:25:20.480 | But if you have the ability to just launch arbitrarily large masses, at least comparatively

00:25:26.080 | compared to JWST, and very large mirrors into space, you can more or less repurpose ground-based

00:25:31.680 | mirrors.

00:25:32.680 | The Hubble Space Telescope mirror and the JWST mirrors are designed to be extremely

00:25:37.600 | lightweight and that increased their cost significantly.

00:25:41.760 | They have this kind of honeycomb design on the back to try and minimize the weight.

00:25:46.360 | If you don't really care about weight because it's so cheap, then you could just literally

00:25:51.600 | grab many of the existing ground-based mirrors across the world - 4-metre, 5-metre mirrors

00:25:57.320 | - and just pretty much attach them to a chassis and have your own space-based telescope.

00:26:02.960 | I think the Breakthrough Foundation, for instance, is an entity that has been interested in doing

00:26:08.920 | this sort of thing.

00:26:10.520 | And so that raises the prospects of having not just one JWST, that just - you know, JWST

00:26:15.760 | is a fantastic resource, but it's split between all of us.

00:26:19.160 | Astronologists, star formation astronomers, those of us studying exoplanets, those of

00:26:24.520 | us wanting to study the ultra-deep fields and the origin of the first galaxies, the

00:26:29.280 | expansion of the universe - everyone has to share this resource.

00:26:32.920 | But we could potentially each have one JWST each that is maybe just studying a handful

00:26:39.760 | of the brightest exoplanet stars and measuring their atmospheres.

00:26:44.160 | This is important because if you - we talked about this planet Trappist-1e earlier - that

00:26:50.200 | planet, if JWST stared at it and tried to look for biosignatures - by which I mean oxygen,

00:26:56.080 | nitrous oxide, methane - it would take it of order of 200 transits to get even a very

00:27:04.680 | marginal - what we'd call two and a half sigma detection - of those, which basically nobody

00:27:08.840 | would believe with that.

00:27:11.040 | And 100 transits - I mean this thing transits once every six days, so you're talking about

00:27:14.920 | four years of staring at the same star with one telescope.

00:27:17.880 | There'd be some breaks, but it'd be hard to schedule much else because you'd have to continuously

00:27:22.640 | catch each one of these transits to build up your signal-to-noise.

00:27:26.920 | And so JWST's never going to do that.

00:27:28.600 | In principle, technically, JWST could technically have the capability of just about detecting

00:27:34.080 | a biosignature on an Earth-like planet around a non-Sun-like star, but still, impressively,

00:27:40.480 | we have basically the technology to do that.

00:27:42.720 | But we simply cannot dedicate all of its time, practically, to that one resource.

00:27:47.200 | And so Starship opens up opportunities like that of mass-producing these kinds of telescopes,

00:27:53.320 | which will allow us to survey for life in the universe, which of course is one of the

00:27:57.480 | grand goals of astronomy.

00:27:58.720 | - I wonder if you can speak to the bureaucracy, the political battles, the scientific battles

00:28:06.040 | for time on the James Webb telescope.

00:28:09.840 | There must be a fascinating process of scheduling that.

00:28:14.880 | All scientists, they're trying to collaborate, figure out what the most important problems

00:28:18.040 | are, and there's an interesting network of interfering scientific experiments, probably,

00:28:24.400 | they have to somehow optimize over.

00:28:27.360 | - It's a really difficult process.

00:28:28.680 | I don't envy the TAC that are going to have to make this decision.

00:28:31.520 | We call it the TAC, the Time Allocation Committee, that make this decision.

00:28:36.480 | And I've served on these before, and it's very difficult.

00:28:38.480 | I mean, typically for Hubble, we were seeing at least 10, sometimes 20 times the number

00:28:43.560 | of proposals for telescope time versus available telescope time.

00:28:47.960 | For GDST, there has been one call already that has gone out.

00:28:52.340 | We call it Cycle 1, and that was oversubscribed by, I think, something like 6 to 1, 7 to 1.

00:28:58.200 | And the Cycle 2, which has just been announced fairly recently, and the deadline is actually

00:29:03.600 | the end of this month, so my team are totally laser-focused on writing our proposals right

00:29:08.040 | now.

00:29:09.760 | That is expected to be much more competitive, probably more comparable to what Hubble saw.

00:29:14.280 | And so, it's hard.

00:29:16.360 | - More competitive than the Cycle 1, you said, already?

00:29:18.320 | Because that's already super competitive.

00:29:19.320 | - More competitive than the first cycle.

00:29:20.480 | So I said the first cycle of James Webb was about 6 to 1, and this will probably be more

00:29:24.920 | like 20 to 1, I would expect.

00:29:26.800 | - So these are all proposals by scientists and so on, and it's not like you can schedule

00:29:31.440 | at any time, because if you're looking for transit times...

00:29:34.200 | - Yeah, you have a time-critical element.

00:29:36.640 | - Yes, time-critical element.

00:29:37.640 | - And they're conflicting in non-obvious ways, because the frequency is different, the duration

00:29:43.480 | is different, there's probably computational needs that are different, there's the type

00:29:48.960 | of sensors, the direction pointing, all that.

00:29:51.560 | - Yeah, it's hard.

00:29:52.560 | And there are certain programs like doing a deep field study, where you just more or

00:29:57.080 | less point the telescope, and that's pretty open.

00:29:59.280 | I mean, you're just accumulating photons.

00:30:01.160 | You can just point at that patch of the sky whenever the telescope's not doing anything

00:30:05.200 | else, and just get to your month, let's say a month of integration time is your goal over

00:30:09.280 | the lifetime of JWST.

00:30:10.480 | So that's maybe a little bit easier to schedule.

00:30:13.160 | It's harder, especially for us looking at cool worlds, because as I said earlier, these

00:30:18.360 | planets transit very infrequently.

00:30:21.720 | So we have to wait.

00:30:22.720 | If you're looking at the Earth transiting the Sun, an alien watching us, they would

00:30:26.520 | only get one opportunity per year to do that observation.

00:30:29.640 | The transit lasts for about 12 hours.

00:30:33.040 | And so if they don't get that time, it's hard.

00:30:37.000 | That's it.

00:30:38.000 | If it conflicted with another proposal that wants to use another time critical element.

00:30:42.440 | It's much easier for planets like these hot planets or these close in planets, because

00:30:47.760 | they transit so frequently, there's maybe 100 opportunities.

00:30:51.460 | And so then the TAT can say, okay, they want 10 transits, there's 100 opportunities here,

00:30:56.440 | it's easier for us to give them time.

00:30:59.680 | We're almost in the worst case scenario.

00:31:01.080 | We're proposing to look for exoplanets around two cool planets.

00:31:04.780 | And so we really only have one bite of the cherry for each one.

00:31:09.520 | And so our sales pitch has been that these are extremely precious events.

00:31:14.360 | And more importantly, JWST is the only telescope, the only machine humanity has ever constructed,

00:31:22.120 | which is capable of finding moons akin to the moons in our solar system.

00:31:26.240 | Kepler can't do it, even Hubble can't do it.

00:31:28.320 | JWST is the first one.

00:31:30.180 | And so there is a new window to the universe, because we know these moons exist.

00:31:35.280 | They're all over the place in the solar system.

00:31:37.120 | You have the Moon, you have Io, Callisto, Europa, Ganymede, Titan.

00:31:42.080 | Lots of moons of fairly similar size, sort of 30% the size of the Earth.

00:31:45.840 | And this telescope is the first one that can find them.

00:31:49.920 | And so we're very excited about the profound implications of ultimately solving this journey

00:31:54.800 | we're on in astronomy, which is to understand our uniqueness.

00:31:57.480 | We want to understand how common is the solar system.

00:32:00.080 | Are we the way, are we the architecture that frequently emerges naturally?

00:32:06.200 | Or is there something special about what happened here?

00:32:09.120 | - I think this is not the worst case, it's the best case.

00:32:11.400 | It's obvious, it's super rare.

00:32:13.160 | So you have to like, I would, so I love scheduling from a computer science perspective, that's

00:32:17.240 | my background.

00:32:18.400 | So algorithmically, to solve a schedule problem, I will schedule the rarest things first.

00:32:22.960 | And obviously this is, the JWST is the first thing that can actually detect a cool world.

00:32:28.200 | So this is a big new thing, you can show off that new thing.

00:32:31.520 | Happens rarely, schedule it first, it's perfect.

00:32:33.840 | - You should be in the talk, this is perfect.

00:32:35.520 | - I will, I'll file my application after we're done with this.

00:32:39.800 | This part of me is the OCD, part of me is the computational aspect, I love scheduling

00:32:43.680 | competing devices, 'cause you have that kind of scheduling on supercomputers, that scheduling

00:32:50.360 | problem is fascinating.

00:32:51.360 | How do you prioritize computation, how do you prioritize science, data collection, sample

00:32:56.920 | collection, all that kind of stuff.

00:32:57.920 | It's actually kind of fascinating, because data, in ways you expect and don't expect,

00:33:03.520 | will unlock a lot of solutions to some fascinating mysteries.

00:33:09.240 | And so collecting the data and doing so in a way that maximizes the possibility of discovery

00:33:14.400 | is really interesting, from a computational perspective.

00:33:17.120 | - I agree, there's a real satisfaction in extracting the maximum science per unit time

00:33:21.640 | out of your telescope.

00:33:23.960 | That's the TAC's job.

00:33:26.240 | But the TAC are not machines, they're not a piece of computer code.

00:33:31.200 | They will make their selections based off human judgment.

00:33:34.640 | And a lot of the telescope, certainly within the field of exoplanets, 'cause there's different

00:33:39.080 | fields of astronomy, but within the field of exoplanets, I think a good expectation

00:33:42.840 | is that most of the telescope time that JWST have will go towards atmospheric retrieval,

00:33:49.080 | which is sort of alluded to earlier, like detecting molecules in the atmospheres, not

00:33:53.960 | biosignatures, 'cause as I said, it's really not designed to do that, it's pushing JWST

00:33:58.720 | probably too far to expect it to do that.

00:34:00.960 | But it could detect, for example, a carbon dioxide rich atmosphere on TRAPPIST-1e.

00:34:05.920 | That's not a biosignature, but you could prove it's like a Venus in that case, or maybe like

00:34:09.800 | a Mars in that case, both those have carbon dioxide rich atmospheres.

00:34:13.440 | Doesn't prove or disprove the existence of life either way, but it is our first characterization

00:34:19.000 | of the nature of those atmospheres.

00:34:21.200 | Maybe we can even tell the pressure level and the temperature of those atmospheres.

00:34:24.240 | So that's very exciting.

00:34:28.280 | We are competing with that, and I think that science is completely mind-blowing and fantastic.

00:34:33.200 | We have a completely different objective, which is in our case to try and look for the

00:34:36.840 | first evidence of these small moons around these planets.

00:34:41.160 | Potentially even moons which could be habitable, of course, so I think it's a very exciting

00:34:44.840 | goal.

00:34:46.040 | But ATT&CK has to make a human judgment, essentially, about which science are they most excited

00:34:52.840 | by, which one has the highest promise of return, the highest chance of return.

00:34:58.200 | And so that's hard because if you look at a planetary atmosphere, well you know most

00:35:03.360 | of the time the planet has an atmosphere already, and so there's almost a guaranteed success

00:35:07.880 | that you're going to learn something about the atmosphere by pointing judiciously at

00:35:10.640 | it.

00:35:11.640 | Whereas in our case, there's a harder sell.

00:35:15.060 | We are looking for something that we do not know for sure exists yet or not.

00:35:19.860 | And so we are pushing the telescope to do something which is inherently more risky.

00:35:25.360 | - Yeah, but the existence, if shown, already gives a deep lesson about what's out there

00:35:33.840 | in the universe.

00:35:34.840 | That means that other stars have similar types of variety as we have in our solar system.

00:35:40.020 | They have an Io, they have a Europa, and so on.

00:35:43.560 | Which means there's a lot of possibility for icy planets, for water, for planets and moons.

00:35:51.920 | That's super exciting because that means everywhere through our galaxy and beyond, there is just

00:36:00.240 | innumerable possibility for weird creatures.

00:36:03.680 | - I agree.

00:36:04.680 | - Life forms.

00:36:05.680 | - You don't have to convince me.

00:36:06.680 | I mean, NASA has been on this quest for a long time and it's sometimes called Eater

00:36:11.840 | Earth.

00:36:12.840 | It's the frequency of Earth-like, usually they say planets, in the universe.

00:36:18.080 | How common are planets similar to our Earth?

00:36:20.880 | In terms of, ultimately we'd like to know everything about these planets in terms of

00:36:24.760 | the amount of water they have, how much atmosphere they have.

00:36:27.560 | But for now it's kind of focused just on the size and the distance from the star, essentially.

00:36:32.380 | How often do you get similar conditions to that?

00:36:35.440 | That was Kepler's primary mission and it really just kind of flirted with the answer.

00:36:39.960 | It didn't quite get to a definitive answer.

00:36:43.000 | But I always say, look, if that's our primary goal, to look for Earth-like, I would say,

00:36:50.160 | then moons has to be a part of that.

00:36:53.160 | Because we know that Earth-like, from the Kepler data, the preliminary result is that

00:36:57.880 | Earth-like planets around Sun-like stars is not an inevitable outcome.

00:37:01.520 | It seems to be something like a 1-10% outcome.

00:37:04.560 | So it's not particularly inevitable that that happens.

00:37:07.840 | But we do often see about half of all Sun-like stars have either a mini-Neptune, a Neptune

00:37:13.720 | or a Jupiter in the habitable zone of their stars.

00:37:16.680 | That's a very, very common occurrence that we see.

00:37:19.640 | Yet we have no idea how often they have moons around them, which could also be habitable.

00:37:24.520 | And so there may very well be, if even one in five of them has an Earth-like moon or

00:37:31.160 | even a Mars-like moon around them, then there would be more habitable real estate in terms

00:37:35.720 | of exo-moons than exoplanets in the universe.

00:37:39.560 | Essentially 2x, 3x, 5x, maybe 10x the number of habitable worlds out there in the universe.

00:37:47.080 | Our current estimate, like the Drake equation.

00:37:49.480 | So this is one way to increase the confidence and increase the value of that parameter.

00:37:57.280 | And just know where to look.

00:37:59.600 | We would like to know where should we listen for technosignatures, where should we be looking

00:38:03.560 | for biosignatures.

00:38:04.560 | And not only that, but what role does the Moon have in terms of its influence on the

00:38:10.400 | planet?

00:38:11.840 | We talked about these directly imaged telescopes earlier, these missions that want to take

00:38:15.640 | a photo to quote Carl Sagan, "the pale blue dot of our planet, but the pale blue dot of

00:38:20.720 | an exoplanet".

00:38:22.440 | And that's the dream, to one day capture that.

00:38:24.760 | But as impressive as the resolution is that we are planning and conspiring to design for

00:38:29.800 | the future generation telescopes to achieve that, even those telescopes will not have

00:38:34.200 | the capability of resolving the Earth and the Moon within that.

00:38:37.080 | It'll be a pale blue dot pixel, but the Moon's grayness will be intermixed with that pixel.

00:38:45.440 | And so this is a big problem, because one of the ways that we are claiming to look for

00:38:48.600 | life in the universe is a chemical disequilibrium.

00:38:53.000 | So you see two molecules that just shouldn't be there, they normally react with each other.

00:38:58.020 | Or even one molecule that's just too reactive to be hanging around the atmosphere by itself.

00:39:01.800 | So if you had oxygen and methane hanging out together, those would normally react fairly

00:39:07.080 | easily.

00:39:08.220 | And so if you detected those two molecules in your pale blue dot spectra, you'd be like,

00:39:12.840 | "OK, we have evidence for life.

00:39:14.280 | Something's metabolizing on this planet."

00:39:16.680 | However, the challenge here is, what if that Moon was Titan?

00:39:21.480 | Titan has a methane-rich atmosphere.

00:39:23.120 | And what if the pale blue dot was in fact a planet devoid of life, but it had oxygen

00:39:28.840 | because of water undergoing this photolysis reaction, splitting into oxygen and hydrogen

00:39:33.800 | separately?

00:39:34.800 | So then you have all of the hallmarks of what we would claim to be life, but all along you

00:39:40.200 | were tricked.

00:39:41.200 | It was just a Moon that was deceiving you.

00:39:43.920 | And so we're never going to, I would claim, really understand or complete this quest of

00:39:51.900 | looking for life by signatures in the universe, unless we have a deep knowledge of the prevalence

00:39:58.340 | and role that Moons have.

00:40:00.380 | They may even affect the habitability of the planets themselves.

00:40:02.680 | Of course, our own Moon is freakishly large.

00:40:05.520 | By mass ratio, it's the largest Moon in the solar system.

00:40:07.960 | It's a 1% mass Moon.

00:40:08.960 | If you look at Jupiter's Moons, they're like 10 to the power of minus 4, much smaller.

00:40:13.360 | And so our own Moon seems to stabilize the obliquity of our planet.

00:40:17.040 | It gives rise to tides, especially early on when the Moon was closer, those tides would

00:40:20.880 | have covered entire continents.

00:40:22.840 | And those rock pools that would have been scattered across the entire plateau may have

00:40:27.600 | been the origin of life on our planet.

00:40:30.280 | The Moon-forming impact may have stripped a significant fraction of lithosphere off

00:40:34.400 | the Earth, which without it, plate tectonics may not have been possible.

00:40:37.800 | We'd have had a stagnant lid because there was just too much lithosphere stuck on the

00:40:41.520 | top of the planet.

00:40:43.120 | And so there are speculative reasons, but intriguing reasons as to why a large Moon

00:40:50.400 | may be not just important, but central to the question of having the conditions necessary

00:40:57.080 | for life.

00:40:58.080 | So Moons can be habitable in their own right, but they can also play a significant influence

00:41:04.480 | on the habitability of the planets they orbit.

00:41:07.200 | And further, they will surely interfere with our attempts to detect life remotely from

00:41:13.600 | afar.

00:41:14.600 | LB: So taking a tangent upon a tangent, you've written about binary planets, and that they're

00:41:23.840 | surprisingly common, or they might be surprisingly common.

00:41:30.040 | What's the difference between a large Moon and binary planets?

00:41:32.760 | What are binary planets?

00:41:35.200 | What's interesting to say here about giant rocks flying through space and orbiting each

00:41:39.560 | other?

00:41:40.560 | CB: The thing that's interesting about binary objects is that they're very common in the

00:41:43.520 | universe.

00:41:44.840 | Binary stars are everywhere.

00:41:46.080 | In fact, the majority of stars seem to live in binary systems.

00:41:51.520 | When we look at the outer edges of the solar system, we see binary Kuiper Belt objects

00:41:56.120 | all the time, asteroids basically bound to one another.

00:41:58.920 | Pluto-Charon is kind of an example of that.

00:42:01.400 | It's a 10% mass ratio system.

00:42:03.600 | It almost is by many definitions a binary planet, but now it's a dwarf planet.

00:42:08.240 | So I don't know what you'd call that now.

00:42:11.160 | But we know that the universe likes to make things in pairs.

00:42:15.200 | LB: So you're saying our Sun is an incel.

00:42:21.160 | So most things are dating, they're in relationships, and ours is alone.

00:42:25.000 | CB: It's not a complete freak of the universe to be alone, but it's more common for something

00:42:32.040 | like stars.

00:42:33.040 | If you count up all the Sun-like stars in the universe, about half of the Sun-like star

00:42:35.560 | systems are in binary or trinary systems, and the other half are single.

00:42:39.880 | But because those binaries are two or three stars, then cumulatively maybe a third of

00:42:44.920 | all Sun-like stars are single.

00:42:46.520 | LB: I'm trying hard to not anthropomorphize the relationship that stars have with each

00:42:52.000 | other.

00:42:53.000 | CB: The triplets game.

00:42:54.000 | LB: Yeah, I've met those folks also.

00:42:58.080 | So is there something interesting to learn about the habitability, how that affects the

00:43:02.400 | probability of habitable worlds when they kind of couple up like that in those different

00:43:07.920 | ways?

00:43:08.920 | CB: It depends which way the stars of the planet.

00:43:10.840 | Certainly if stars couple up, that has a big influence on the habitability.

00:43:16.280 | Of course this is very famous from Star Wars, Tatooine in Star Wars is a binary star system,

00:43:20.480 | and you have Luke Skywalker looking at the Sunset and seeing two stars come down.

00:43:24.720 | And for years we thought that was purely a product of George Lucas's incredibly creative

00:43:30.160 | mind, and we didn't think that planets would exist around binary star systems.

00:43:35.880 | It seems like too tumultuous an environment for a quiescent planetary disc, a circumstellar

00:43:42.240 | disc to form planets from.

00:43:44.680 | And yet one of the astounding discoveries from Kepler was that these appear to be quite

00:43:50.520 | common.

00:43:51.520 | In fact, as far as we can tell, they're just as common around binary stars as single stars.

00:43:56.000 | The only caveat to that is that you don't get planets close into binary stars.

00:44:00.680 | They have a clearance region on the inside where planets maybe they form there, but they

00:44:06.120 | don't last.

00:44:07.120 | They are dynamically unstable in that zone.

00:44:10.800 | But once you get out to about the distance that the Earth orbits the Sun, or even a little

00:44:14.080 | bit closer in, you start to find planets emerging.

00:44:18.280 | And so that's the right distance for liquid water, the right distance for potentially

00:44:21.760 | life on those planets.

00:44:23.100 | And so there may very well be plenty of habitable planets around the binary stars.

00:44:27.260 | Binary planets is a little bit different.

00:44:28.940 | Binary planets, I don't think we have any serious connection of planet banality to habitability.

00:44:37.060 | Certainly when we investigated it, that wasn't our drive that this is somehow the solution

00:44:41.540 | to life in the universe or anything.

00:44:43.700 | It was really just a, like all good science questions, a curiosity-driven question.

00:44:47.540 | LB: What's the dynamic?

00:44:48.540 | Are they legit orbiting each other as they orbit the star?

00:44:53.220 | CB: So the formation mechanism proposed here, because it is very difficult to form two proto-planets

00:44:59.860 | close to each other like this.

00:45:00.860 | They would generally merge within the disk, and so that's why you normally get single

00:45:04.380 | planets.

00:45:05.380 | But you could have something like Jupiter and Saturn form at separate distances.

00:45:09.100 | They could dynamically be scattered in towards one another, and basically not quite collide,

00:45:14.320 | but have a very close-on encounter.

00:45:16.820 | Now because tidal forces increase dramatically as the distance decreases between two objects,

00:45:23.180 | the tides can actually dissipate the kinetic energy and bring them bound into one another.

00:45:28.660 | So that seems, when you first hear that, you think that seems fairly contrived, that you'd

00:45:34.420 | have the conditions just right to get these tides to cause a capture.

00:45:38.220 | But numerical simulations have shown that about 10% of planet-planet encounters are

00:45:43.020 | shown to produce something like binary planets, which is a startling prediction.

00:45:48.900 | And so that seems at odds with, naively, the exoplanet catalogue for which we know of,

00:45:53.840 | so far, no binary planets.

00:45:56.060 | And we propose one of the resolutions to this might be that the binary planets are just

00:45:59.100 | incredibly difficult to detect, which is also counterintuitive.

00:46:03.660 | Because remember how they form is through this tidal mechanism, and so they form extremely

00:46:07.800 | close to each other.

00:46:08.800 | So the distance that Io is away from Jupiter, just a few planetary radii, they're almost

00:46:12.980 | touching one another, and they're just tidally locked, facing each other for eternity.

00:46:18.180 | And so in that configuration, as it transits across the star, it kind of looks like you

00:46:23.020 | can't really resolve those two planets.

00:46:24.700 | It just looks like one planet to you that's going across the star.

00:46:27.740 | The temporal resolution of the data is rarely good enough to distinguish that.

00:46:31.540 | And so you'd see one transit, but in fact it's two planets very close together, which

00:46:36.300 | are transiting at once.

00:46:37.900 | And so, yeah, we wrote a paper just recently where we developed some techniques to try

00:46:42.580 | and get around this problem, and hopefully provide a tool where we could finally look

00:46:47.340 | for these planets.

00:46:48.340 | The problem of detection of these planets when they're so close together.

00:46:50.620 | That was our focus, was how do you get around this merging problem.

00:46:55.460 | So whether they're out there or not, we don't know.

00:47:00.060 | We're planning to do a search for them, but it remains an open question.

00:47:04.580 | And I think just one of those fun astrophysics curiosities questions, whether binary planets

00:47:09.660 | exist in the universe.

00:47:10.660 | Because then you have binary Earths, you could have binary Neptune, all sorts of wild stuff

00:47:15.060 | that would float the sci-fi imagination.

00:47:17.940 | - I wonder what the physics on a binary planet feels like.

00:47:22.140 | It might be trivial.

00:47:23.340 | I have to think about that.

00:47:25.180 | I wonder if there's some interesting dynamics.

00:47:26.980 | Like, if you have multiple, or would gravity feel different on different parts of the surface

00:47:31.940 | of the sphere when there's another large sphere?

00:47:34.380 | - Yeah, I would think that the force would be fairly similar, because the shape of the

00:47:39.980 | object would deform to a flat geopotential, essentially a uniform geopotential.

00:47:45.500 | But it would lead to a distorted shape for the two objects.

00:47:48.940 | I think they'd become ellipsoids facing one another.

00:47:52.420 | So it would be pretty wild when people like flat Earth or spherical Earth, you fly from

00:47:57.620 | space and you see a football-shaped Earth.

00:47:59.620 | - Finally, there's proof.

00:48:02.420 | And I wonder how difficult it would be to travel from one to the other, because you

00:48:06.100 | have to overcome the one.

00:48:08.300 | No, it might be kind of easy.

00:48:11.700 | - Yeah, I mean, they're so close to each other, that helps.

00:48:15.180 | And I think the most critical factor would be how massive is the planet.

00:48:17.980 | That's always, I mean, one of the challenges with escaping planets, there was a fun paper

00:48:21.860 | one of my colleagues wrote that suggested that super-Earth planets may be inescapable.

00:48:26.860 | If you're a civilization that were born on a super-Earth, the surface gravity is so high

00:48:31.620 | that the chemical potential energy of hydrogen or methane, whatever fuel you're using, simply

00:48:39.700 | is at odds with the gravity of the planet itself.

00:48:43.060 | And so you would, you know, our current rockets, I'm not sure of the fraction, but maybe like

00:48:47.140 | 90% of the rocket is fuel or something by mass.

00:48:49.760 | These things would have to be like the size of the Giza pyramids of fuel with just a tiny

00:48:55.660 | tip on the top in order just to escape that planetary atmosphere.

00:48:59.380 | And so it has been argued that if you live on a super-Earth, you may be forced to live

00:49:04.580 | there forever.

00:49:05.580 | There may be no escape unless you invent a space elevator or something, but then how

00:49:09.100 | do you even build the infrastructure and space to do something like that in the absence of

00:49:13.820 | a successful rocket program?

00:49:16.260 | And so the more and more we look at our Earth and think about the sorts of problems we're

00:49:21.820 | facing, the more you see things about the Earth which make it ideally suited in so many

00:49:27.300 | regards.

00:49:28.300 | It's so spooky, right, that we not only live on a planet which has the right conditions

00:49:32.420 | for life, for intelligent life, for sustained fossil fuel industry, just happens to be in

00:49:37.140 | the ground.

00:49:38.140 | We have plenty of fossil fuels to get our industrial revolution going.

00:49:41.820 | But also the chemical energy contained within those fossil fuels and hydrogen and other

00:49:47.260 | fuels is sufficient that we have the ability to escape our planetary atmosphere and planetary

00:49:52.020 | gravity to have a space program.

00:49:54.540 | And we also happen to have a celestial body which is just within reach, the Moon, which

00:50:00.060 | doesn't also necessarily have to be true.

00:50:02.100 | Were the Moon not there, what effect would that have had on our aspirations of a space

00:50:07.440 | program in the 1960s?

00:50:09.380 | Would there have ever been a space race to Mars or to Venus?

00:50:12.700 | It's a much harder...

00:50:13.700 | Certainly for a human program, that seems almost impossible with 1960s technology to

00:50:17.260 | imagine ever come to fruition.

00:50:18.620 | It's almost as if somebody constructed a set of challenging obstacles before us, challenging

00:50:25.020 | problems to solve.

00:50:26.780 | They're challenging, but they're doable.

00:50:29.260 | And there's a sequence of them.

00:50:30.900 | Gravity is very difficult to overcome, but we have, given the size of Earth, it's not

00:50:35.780 | so bad that we could still actually construct propulsion systems that can escape it.

00:50:40.100 | Yeah.

00:50:41.100 | And the same with climate change, perhaps.

00:50:42.100 | I mean, climate change is the next major problem facing our civilization.

00:50:46.580 | But we know it is technically surmountable.

00:50:50.020 | It does seem sometimes like there has been a series of challenges laid out to progress

00:50:57.800 | us towards a mature civilization that can one day perhaps expand to the stars.

00:51:02.460 | I'm a little more concerned about nuclear weapons, AI, and natural or artificial pandemics.

00:51:09.580 | But yes, climate change is...

00:51:10.580 | Well, there you go.

00:51:11.580 | I mean, plenty of milestones that we need to cross.

00:51:14.860 | And we can argue about the severity of each of them, but there is no doubt that we live

00:51:18.940 | in a world that has serious challenges that are pushing our intellects and our will to

00:51:25.180 | the limit of whether we're really ready to progress to the next stage of our development.

00:51:31.420 | So thank you for taking the tangent, and there'll be a million more.

00:51:34.540 | But can we step back to Kepler-1625b?

00:51:38.500 | What is it?

00:51:39.500 | And you've talked about this kind of journey, this effort to discover exomoons, so moons

00:51:48.140 | out there, or small, cool objects out there.

00:51:52.900 | Where does that effort stand, and what is Kepler-1625b?

00:51:55.180 | Yeah, I mean, I've been searching for exomoons for most of my professional career.

00:52:00.380 | And I think a lot of my colleagues think I'm kind of crazy to still be doing it.

00:52:08.820 | After five years of not finding anything, I think most people would probably try doing

00:52:12.180 | something else.

00:52:13.180 | I even had people say that to me.

00:52:14.180 | They said, you know, professors.

00:52:15.180 | I remember at a cocktail party, took me to the side, an MIT professor, and he said, "You

00:52:21.340 | know, you should just look for hot Jupiters.

00:52:23.260 | They're everywhere.

00:52:24.260 | You can write papers.

00:52:25.260 | They're so easy to find."

00:52:26.260 | And I was like, "Yeah, but hot Jupiters, they're not interesting to me.

00:52:32.140 | I want to do something that I feel intellectually pushes me to the edge, and is maybe a contribution

00:52:38.700 | that not no one else could do, but maybe is not certainly the thing that anybody could

00:52:44.420 | do.

00:52:45.420 | I don't want to just be the first to something for the sake of being first.

00:52:47.660 | I want to do something that feels like a meaningful intellectual contribution to our society."

00:52:53.300 | And so, this exomoon problem has been haunting me for years to try and solve this.

00:52:58.420 | Now as I said, we looked for years and years using Kepler, and the closest we ever got

00:53:03.020 | was just a hint for this one star.

00:53:05.620 | Kepler-1625 has a Jupiter-like planet in orbit of it, and that Jupiter-like planet is on

00:53:11.220 | a 287-day period, so it's almost the same distance as the Earth around the Sun, but

00:53:16.700 | for a Jupiter.

00:53:19.140 | So that was already unusual.

00:53:20.700 | I don't think people realize that Jupiter-like planets are quite rare in the universe.

00:53:25.260 | Certainly mini-Neptunes and Neptunes are extremely common, but Jupiters, only about 10% of Sun-like

00:53:30.780 | stars have Jupiters around them, as far as we can tell.

00:53:33.380 | - When you say Jupiter, which aspect of Jupiter?

00:53:36.140 | - In terms of its mass and its semi-major axis.

00:53:39.380 | So anything beyond about half an AU, so half the distance of the Earth and the Sun, and

00:53:44.500 | something of order of a tenth of a Jupiter mass, that's the mass of Saturn, up to say

00:53:49.460 | ten Jupiter masses, which is basically where you start to get to brown dwarfs.

00:53:53.580 | Those types of objects appear to be somewhat unusual.

00:53:56.620 | Most solar systems do not have Jupiters, which is really interesting, because Jupiter, again,

00:54:02.620 | like the Moon, seems to have been a pivotal character in the story of the development

00:54:07.420 | of our solar system, perhaps especially having a large influence on the development of the

00:54:12.580 | late heavy bombardment and the rate of asteroid impacts that we receive and things like this.

00:54:16.580 | Anyway, to come back to 1625, this Jupiter-like planet had a hint of something in the data.

00:54:23.700 | What I mean by that is when we looked at the transit, we got the familiar decrease in light

00:54:28.580 | that we always see when a planet tries to come in front of the star.

00:54:31.060 | But we saw something extra; just on the edges we saw some extra dips around the outside.

00:54:37.140 | It was right at the hairy edge of detectability.

00:54:39.760 | We didn't believe it, because I think one of the challenges of looking for something

00:54:45.620 | for ten years is that you become your own greatest skeptic.

00:54:49.460 | And no matter what you're shown, you're always thinking, "I've been falling in love so many

00:54:54.600 | times and it's not working out."

00:54:58.220 | You convince yourself it's never going to happen.

00:55:01.580 | Not for me.

00:55:02.580 | This just isn't going to happen.

00:55:03.940 | I saw that and I didn't really believe it, because I didn't dare let myself believe it.

00:55:10.020 | But being a good scientist, we knew we had an obligation to publish it, to talk about

00:55:15.420 | the result, and to follow it up and to try and resolve what was going on.

00:55:19.660 | So we asked for Hubble Space Telescope time, which was awarded in that case.

00:55:24.540 | We were one of those lucky 20 that got telescope time.

00:55:27.860 | We stared at it for about 40 hours continuously.

00:55:32.220 | And to provide some context, the dip that we saw in the Kepa data corresponded to a

00:55:37.260 | Neptune-sized Moon around a Jupiter-sized planet, which was another reason why I was

00:55:41.940 | skeptical.

00:55:42.940 | We don't have that in the solar system; that seems so strange.

00:55:46.980 | And then when we got the Hubble data, it seemed to confirm exactly that.

00:55:51.420 | There were two really striking pieces of evidence in the data that suggested this Moon was there.

00:55:57.740 | Another was a fairly clear second dip in light, pretty clearly resolved by Hubble.

00:56:02.340 | It was about a five sigma detection.

00:56:04.980 | And on top of that, we could see the planet didn't transit when it should have done.

00:56:09.580 | It actually transited earlier than we expected it to, by about 20 minutes or so.

00:56:13.900 | And so that's a hallmark of a gravitational interaction between the planet and the Moon.

00:56:17.560 | We actually expected that.

00:56:18.980 | You can also expect that if the Moon transits after the planet, then the planet should come

00:56:23.620 | in earlier than expected, because the barycenter, the center of mass, lives between the two

00:56:28.660 | of them, kind of like on a balancing arm between them.

00:56:32.500 | And so we saw that as well.

00:56:33.580 | So the phase signature matched up.

00:56:35.620 | The mass of the Moon was measured to be Neptune mass, and the size of the Moon was measured

00:56:40.540 | to be Neptune radius.

00:56:41.900 | And so everything just really lined up.

00:56:46.220 | And we spent months and months trying to kill it.

00:56:50.100 | This is my strategy for anything interesting.

00:56:53.180 | We just try to throw the kitchen sink at it and say, "We must be tricked by something."

00:56:57.380 | And so we tried looking at the centroid motion of the telescope, the different wavelength

00:57:02.980 | channels that have been observed, the pixel level information.

00:57:06.420 | And no matter what we did, we just couldn't get rid of it.

00:57:08.980 | And so we submitted it to Science.

00:57:11.740 | And I think at the time, Science, which is one of the top journals, said to us, "Would

00:57:15.500 | you mind calling your paper 'Discovery of an Exomoon'?"

00:57:19.140 | And I had to push back, and we said, "No, we're not calling it that.

00:57:23.040 | I don't- even despite everything we've done, we're not calling it a discovery.

00:57:26.620 | We're calling it evidence for an exomoon."

00:57:29.700 | Because for me, I'd want to see this repeat two times, three times, four times before

00:57:34.540 | I really would bet my house that this is the real deal.

00:57:38.380 | And I do worry, as I said, that perhaps that's my own self-skepticism going too far.

00:57:44.660 | But I think it was the right decision.

00:57:47.460 | And since that paper came out, there has been continuous interest in this subject.

00:57:52.860 | The team independently analysed that star and recovered actually pretty much exactly

00:57:57.500 | the same results as us, the same dip, the same wobble of the planet.

00:58:02.500 | And a third team looked at it, and they actually got something different.

00:58:05.060 | They saw the dip was diminished compared to what we saw.

00:58:07.820 | They saw a little hint of a dip, but not as pronounced as what we saw.

00:58:11.520 | And they saw the wobble as well.

00:58:13.760 | So there's been a little bit of tension about analysing the reduction of the Hubble data.

00:58:21.960 | And so the only way in my mind to resolve this is just to look again.

00:58:26.160 | We actually did propose to Hubble straight after that.

00:58:29.140 | And we said, "Look, if our model is right, if the Moon is there, it came in late last

00:58:35.060 | time.

00:58:36.060 | It transited after the planet.

00:58:37.960 | Because of the orbit, we can calculate that it should transit before the planet next time.

00:58:43.140 | If it's not there, if it doesn't transit before, and even if we see a dip afterwards, we know

00:58:46.680 | that's not our Moon.

00:58:48.140 | It's obviously some instrumental effect with the data."

00:58:50.700 | We had a causal prediction as to where the Moon should be.

00:58:53.840 | And so I was really excited about that, but we didn't get the telescope time.

00:58:58.180 | And unfortunately, if you go further into the future, we no longer have the predictive

00:59:02.100 | capability.

00:59:03.160 | Because it's like predicting the weather.

00:59:04.340 | You might be able to predict the weather next week to some level of accuracy, but predicting

00:59:08.020 | the weather next year becomes incredibly hard.

00:59:10.620 | The uncertainties just grow and compound as you go forward into the future more and more.

00:59:15.020 | LB: How were you able to know where the Moon would be positioned?

00:59:18.460 | So you're able to tell the orbiting geometry and frequency?

00:59:25.460 | CB: Yeah, so basically from the wobbles of the planet itself, that tells us the orbital

00:59:32.580 | motion of the Moon.

00:59:34.260 | It's the reflex motion of the Moon on the planet.

00:59:35.980 | LB: But isn't it just an estimate where...

00:59:39.940 | Like I'm concerned about you making a strong prediction here.

00:59:42.620 | Because if you don't get the Moon where the Moon leads on the next time around, if you

00:59:48.660 | did get Hubble time, couldn't that mean something else if you didn't see that?

00:59:53.060 | Because you said it would be an instrumental...

00:59:55.580 | I feel the strong urge to disprove your own, which is a really good imperative.

01:00:03.340 | It's a good way to do science.

01:00:05.420 | But this is such a noisy signal, right?

01:00:09.100 | Or blurry signal, maybe.

01:00:11.380 | Or resolution signal, maybe.

01:00:12.860 | CB: Yeah, I mean it's a five sigma signal, so that's at the slightly uncomfortable edge.

01:00:17.420 | I mean, it's often said that for any detection of a first new phenomena, you really want

01:00:21.900 | like a 20, 25 sigma detection.

01:00:24.220 | Then there's just no doubt that what you're seeing is real.

01:00:27.900 | This was at that edge.

01:00:28.900 | I mean, I guess it's comparable to the Higgs boson, but the Higgs boson was slightly different

01:00:31.900 | because there was so much theoretical impetus as to expect a signal at that precise location.

01:00:38.220 | A Neptune-sized Moon was not predicted by anyone.

01:00:40.580 | There was no papers you can find that expect Neptune-sized Moons around Jupiter-sized planets.

01:00:45.100 | So I think we were inherently sceptical about its reality for that reason.

01:00:50.300 | But this is science in action.

01:00:51.540 | And when we fit the wobbles, we fit the dips, and we have this 3G geometric model for the

01:00:57.980 | motion of the orbit, and projecting that forward, we found that about 80% of our projections

01:01:04.140 | led to the Moon to be before.

01:01:05.780 | So it's not 100%.

01:01:07.140 | There was maybe 20% of the cases it was over here.

01:01:10.460 | But to me, that was a hard enough projection that we felt confident that we could refute

01:01:17.980 | the exit, which was what I really wanted.

01:01:19.420 | I wanted a refutable, that's the basis of science, a falsifiable hypothesis.

01:01:23.900 | How can you make progress in science if you don't have a falsifiable testable hypothesis?

01:01:27.580 | And so that was the beauty of this particular case.

01:01:31.020 | So there's a numerical simulation with the Moon that fits the data that we observed,

01:01:35.540 | and then you can now make predictions based on that simulation.

01:01:40.100 | That's so cool.

01:01:41.100 | Okay.

01:01:42.100 | It's fun.

01:01:43.100 | These are like little solar systems that we can simulate on the computer and imagine their

01:01:47.860 | motions.

01:01:49.260 | But we are pushing things to the very limits of what's possible, and that's double-edged

01:01:54.140 | sword.

01:01:55.140 | It's both incredibly exciting intellectually, but you're always risking, to some degree,

01:02:01.820 | the pushing too far.

01:02:03.580 | So I'd like to ask you about the recent paper you co-authored, an exomoon survey of 70 cool

01:02:09.780 | giant exoplanets and the new candidate Kepler 1708 Bi.

01:02:15.300 | I would say there's like three or four candidates at this point, of which we have published

01:02:19.300 | two of them.

01:02:20.300 | And to me, two are quite compelling and deserve follow-up observations.

01:02:27.660 | And so to get a confirmed detection, at least in our case, we would need to see it repeat,

01:02:32.580 | for sure.

01:02:33.580 | One of the problems with some of the other methods that have been proposed is that you

01:02:36.420 | don't get that repeatability.

01:02:38.380 | So for instance, an example of a technique that would lack that would be gravitational

01:02:41.860 | microlensing.

01:02:43.180 | So it's possible with a new telescope coming up in the future called the Roman Space Telescope,

01:02:48.260 | which is basically a repurposed spy satellite that's the size of the Hubble mirror going

01:02:53.300 | up into space.

01:02:55.100 | It will stare at millions of stars simultaneously, and it will look to see - instead of whether

01:03:00.220 | any of those stars get dimmer for a short amount of time, which would be a transit,

01:03:05.460 | it'll look for the opposite.

01:03:06.460 | It'll look to see if anything can get brighter.

01:03:08.620 | And that brightness increase is caused by another planetary system passing in front

01:03:13.140 | and then gravitationally lensing light around it to cause a brightening.

01:03:17.780 | So this is a method of discovering an entire solar system, but only for a glimpse.

01:03:25.220 | You just get a short glimpse of it passing like a ship sailing through the night, just

01:03:29.460 | that one photo of it.

01:03:31.340 | Now the problem with that is that it's very difficult.

01:03:35.540 | The physics of gravitational lensing are not surprisingly quite complicated.

01:03:40.220 | And so there's many, many possible solutions.

01:03:42.260 | So you might have a solution which is this could be a red dwarf star with a Jupiter-like

01:03:48.620 | planet around it.

01:03:49.620 | That's one solution.

01:03:50.700 | But another solution is that it's a free-floating planet, a rogue planet like Jupiter, with

01:03:55.540 | an Earth-like moon around it.

01:03:57.240 | And those two solutions are almost indistinguishable.

01:04:00.160 | Now ideally, we would be able to repeat the observation.

01:04:03.660 | We'd be able to go back and see, well, if the moon really is there, then we could predict

01:04:06.660 | its mass, its predicted motion, and expect it to be maybe over here next time or something.

01:04:11.240 | With microlensing, it's a one snapshot event.

01:04:14.700 | And so for me, it's intriguing as a way of revealing something about the exomoon population.

01:04:20.580 | But I always come back to transits because it's the only method we really have that's

01:04:24.900 | absolutely repeatable, that we'll be able to come back and prove to everyone that, look,

01:04:30.700 | on the 17th of October, the moon will be over here, and the moon will look like this, and

01:04:34.620 | we can actually capture that image.

01:04:36.180 | And that's what we see with, of course, many exoplanets.

01:04:37.840 | So we want to get to that same point of full confidence, full confirmation, the slam-dunk

01:04:42.340 | detection of these exomoons.

01:04:44.540 | But yeah, it's been a hell of a journey to try and push the field into that direction.

01:04:53.140 | Is there some resistance to the transit method?

01:04:56.820 | Not to the transit method, I just say to exomoons.

01:04:58.660 | So the transit method is by far the most popular method for looking for exoplanets.

01:05:03.700 | But yeah, as I've alluded to, exomoons is kind of a niche topic within the discipline

01:05:10.060 | of exoplanets.

01:05:11.380 | And that's largely because there are people, I think, are waiting for those slam-dunks.

01:05:17.260 | And it was like, if you go back to the first exoplanet discovery that was made in 1995

01:05:22.420 | by Misha Mayor and Didier Queloz, I think it's true at the time that they were seen

01:05:27.860 | as mavericks.

01:05:29.340 | The idea of looking for planets around stars was considered fringe science.

01:05:33.780 | And I'm sure many colleagues told them, "Why don't you do something more safe, like study

01:05:38.040 | eclipsing stars?"

01:05:39.420 | Two binary star systems, we know those exist, so why are you wasting your time looking for

01:05:43.380 | planets?

01:05:44.380 | You're going to get this alien moniker or something, and you'll be seen as a fringe

01:05:48.700 | maverick scientist.

01:05:50.180 | And so I think it was quite difficult for those early planet hunters to get legitimacy

01:05:55.140 | and be taken seriously.

01:05:56.140 | And so very few people risked their careers to do it, except for those that were either

01:06:00.340 | emboldened to try or had maybe the career, maybe like a tenure or something, so they

01:06:06.780 | didn't have to necessarily worry about the implications of failure.

01:06:10.060 | And so once that happened, once they made the first discoveries, overnight everyone

01:06:16.440 | and their dog was getting into exoplanets.

01:06:18.500 | And all of a sudden the whole astronomy community shifted, and huge numbers of people that were

01:06:23.820 | once upon a time studying eclipsing binaries changed to becoming exoplanet scientists.

01:06:28.860 | And so that was the first wave of exoplanet scientists.

01:06:31.380 | We're now in a kind of a second wave, or even a third wave, where people like me to some

01:06:36.560 | degree kind of grew up with the idea of exoplanets as being normal.

01:06:40.060 | I was 11 years old, I guess, when the first exoplanet was discovered.

01:06:43.620 | And so to me it was a fairly normal idea to grow up with.

01:06:48.760 | And so we've been trained in exoplanets from the very beginning.

01:06:53.780 | And so that brings a different perspective to those who have maybe transitioned from

01:06:59.460 | a different career path.

01:07:01.960 | And so I suspect with exomoons and probably technosignatures, astrobiology, many of the

01:07:09.340 | topics which are seen at the fringes of what's possible, they will all open up into becoming

01:07:16.060 | mainstream one day.

01:07:17.680 | But there's a lot of people who are just waiting, waiting for that assuredness that there is

01:07:23.940 | a secure career net ahead of them before they commit.

01:07:28.380 | - Yeah, it does seem to me that exomoons open wider or open for the first time the door

01:07:35.220 | to aliens.

01:07:37.060 | Just more seriously, academically studying, all right, let's look at alien worlds.

01:07:42.620 | So I think it's still pretty fringe to talk about alien life, even on Mars and the moons

01:07:48.020 | and so on.

01:07:49.020 | You're kind of like, it would be nice, but imagine the first time to discover a living

01:07:53.780 | organism.

01:07:54.780 | That's gonna change, then everybody will look like an idiot for not focusing everything

01:08:00.380 | on this.

01:08:01.380 | 'Cause the possibility of the things, it's possible it might be super boring.

01:08:06.220 | It might be very boring bacteria, but even the existence of life elsewhere, I mean, that

01:08:11.940 | changes everything.

01:08:12.940 | That means life is everywhere.

01:08:14.660 | - If you knew now that in five years, 10 years, the first life would be discovered elsewhere,

01:08:19.800 | you knew that in advance, it would surely affect the way you approach your entire career.

01:08:25.460 | Especially someone junior in astronomy, you would surely be like, well, this is clearly

01:08:28.580 | gonna be the direction I have to dedicate my classes and my training and my education

01:08:32.980 | towards that direction.

01:08:33.980 | - All the new textbooks, all the--

01:08:35.900 | - Right.

01:08:36.900 | - You have to be written.

01:08:38.660 | And I think there's a lot of value to hedging, like allocating some of the time to that possibility.

01:08:45.780 | Because the kind of discoveries we might get in the next few decades, it feels like we're

01:08:52.700 | on the verge of getting a lot of really good data and having better and better tools that

01:08:59.420 | can process that data.

01:09:00.420 | So there's just going to be a continuous increase of the kind of discoveries that will open.

01:09:05.380 | But a slam dunk, that's hard to come by.

01:09:08.540 | - Yeah, I think a lot of us are anticipating, I mean, we're already seeing it to some degree

01:09:12.860 | with Venus and the phosphine incident.

01:09:15.620 | But we've seen it before with Bill Clinton's in the White House lawn announcing life from

01:09:19.460 | Mars and there are inevitably gonna be spurious claims, or at least claims which are ambiguous

01:09:26.500 | to some degree.

01:09:27.940 | There will be for sure a high profile journal like Nature or Science that will one day publish

01:09:34.080 | a paper saying, "Biosignature discovered" or something like that on TRAPPIST-1 or some

01:09:39.100 | other planet.

01:09:40.300 | And then there will be years of back and forth in the literature.

01:09:44.660 | And that might seem frustrating, but that's how science works.

01:09:47.740 | That's the mechanism of science at play, of people scrutinizing the results to intense

01:09:52.980 | skepticism.

01:09:54.420 | And it's like a crucible, you know, you burn away all irrelevances until whatever is left

01:09:59.740 | is the truth.

01:10:00.900 | And so you're left with this product which is that, okay, we either believe or don't

01:10:05.700 | believe that biosignatures are there.

01:10:07.180 | So there's inevitably going to be a lot of controversy and debate and argument about

01:10:11.540 | it.

01:10:12.540 | We just have to anticipate that.

01:10:13.540 | And so I think you have to basically have a thick skin to some degree, academically,

01:10:18.320 | to dive into that world.

01:10:20.200 | And you're seeing that with phosphine.

01:10:25.880 | It's been uncomfortable to watch from the outside, the kind of dialogue that some of

01:10:31.400 | the scientists have been having with each other about that.

01:10:34.200 | Because...

01:10:35.200 | >>They get a little aggressive.

01:10:37.200 | >>Yeah, and you can understand why, because...

01:10:41.200 | >>Jealousy?

01:10:42.200 | I don't know.

01:10:43.200 | That's me saying, not you.

01:10:44.960 | That's me talking.

01:10:46.800 | I'm sure there's some envy and jealousy involved on the behalf of those who are not part of

01:10:55.080 | the original discovery.

01:10:56.760 | But there's also, in any case, just leave the particular people involved in Venus alone,

01:11:01.640 | in any case of making a claim of that magnitude, especially life, because life is pretty much

01:11:09.120 | one of the biggest discoveries of all time, you can imagine, scientifically.

01:11:14.100 | You can see, and I'm so conscious of this in myself when I get close to, as I said,

01:11:18.940 | even the much smaller goal of setting an exomoon, the ego creeping.

01:11:24.040 | And so as a scientist, we have to be so guarded against our own egos.

01:11:28.080 | You see the lights in your eyes of a Nobel Prize, or the fame and fortune and being remembered

01:11:36.160 | in the history books.

01:11:37.160 | And we all grew up in our training learning about Newton and Einstein, these giants of

01:11:41.840 | the field, Feynman and Maxwell.

01:11:44.320 | And you get the idea of these individual contributions which get immortalized for all time, and that's

01:11:51.280 | seductive.

01:11:52.280 | It's why many of us with the skill set to go into maybe banking instead decided, actually,

01:11:57.360 | there's something about the idea of being immortalized and contributing towards society

01:12:01.480 | in a permanent way that is more attractive than the financial reward of applying my skills

01:12:06.880 | elsewhere.

01:12:07.880 | And to some degree, that ego can be a benefit because it brings in skillful people into

01:12:12.520 | our field who might otherwise be tempted by money elsewhere.

01:12:16.200 | But on the other hand, the closer you get towards when you start flirting with that

01:12:23.420 | Nobel Prize in your eyes, or you think you're on the verge of seeing something, you can

01:12:27.880 | lose objectivity.

01:12:29.640 | A very famous example of this is Barnard's Star.

01:12:33.400 | There was a planet claimed there by Peter van der Kamp, I think it was in 1968, 69.

01:12:39.320 | And at the time, it would have been the first ever exoplanet ever claimed.

01:12:43.160 | And he felt assured that this planet was there.

01:12:47.400 | He was actually using the wobbling star method, but using the positions of the stars to see

01:12:50.800 | them, to claim this exoplanet.

01:12:53.800 | It turned out that this planet was not there.

01:12:57.760 | Subsequent analyses by both dynamicists and theorists and those looking at the instrumental

01:13:01.680 | data established fairly unanimously that there was no way this planet was really there.

01:13:09.080 | But Peter van der Kamp insisted it was there, despite overwhelming evidence that was accruing

01:13:14.080 | against him.

01:13:16.320 | And even to the day he died, which was I think in the early 90s, he was still insisting this

01:13:22.200 | planet was there, even when we were starting to make the first genuine exoplanet discoveries.

01:13:26.980 | And even at that point, I think Hubble had even looked at that star and had totally ruled

01:13:31.860 | out any possibility of what he was talking about.

01:13:35.060 | And so that's a problem.

01:13:36.340 | How do you get to a point as a scientist where you just can't accept anything that comes

01:13:41.520 | otherwise?

01:13:42.520 | Because it starts out with the dream of fame, and then it ends in a stubborn refusal to

01:13:49.740 | ever back down.

01:13:50.740 | Of course, the flip side of that is sometimes you need that to have the strength to carry

01:13:57.500 | a belief against the entire scientific community that resists your beliefs.

01:14:02.980 | And so it's a double-edged sword.

01:14:05.180 | - That can happen, but I guess the distinction here is evidence.

01:14:09.500 | So in this case, the evidence was so overwhelming, it wasn't really a matter of interpretation.

01:14:17.340 | You had observed this star with the same star, but with maybe 10, even 100 times greater

01:14:23.340 | precision for much longer periods of time.

01:14:26.900 | And there was just no doubt at this point this planet was a mirage.

01:14:31.540 | And so that's why you have to be very careful.

01:14:32.540 | I always say, don't ever name my wife and my daughter, like, "Name this planet after

01:14:37.020 | me that you discover."

01:14:38.020 | I can't ever name a planet after you, because I won't be objective anymore.

01:14:44.660 | How could I ever turn around to you and say that planet wasn't real that I named after

01:14:48.780 | you?

01:14:49.780 | - So you're somebody that talks about, and it's clear in your eyes and in your way of

01:14:53.380 | being that you love the process of discovery, that joy, the magic of just seeing something,

01:15:02.260 | a new observation, a new idea.

01:15:05.700 | But I guess the point is when you have that great feeling is to then switch on the skepticism,

01:15:13.540 | to start testing what does this actually mean?

01:15:17.660 | Is this real?

01:15:18.660 | What are the possible different interpretations that could make this a lot less grand than

01:15:23.380 | I first imagined?

01:15:25.340 | So both have the wonder and the skepticism all in one brain.

01:15:28.900 | - Yeah, I think generally the more I want something to be true, the more I inherently

01:15:34.500 | doubt it.

01:15:35.500 | And I think that just comes from, you know, I grew up with a religious family and was

01:15:41.900 | just sort of indoctrinated to some degree, like many children are, that, okay, this is

01:15:45.660 | normal, that there's a God and this is the way the world is.

01:15:49.300 | God created the Earth.

01:15:50.300 | And then as I became more well-read and illiterate of what was happening in the world scientifically,

01:15:56.980 | I started to doubt.

01:15:58.500 | And it really just struck me that the hardest thing to let go of when you do decide not

01:16:03.820 | to be religious anymore, and it's not really like a light bulb moment, but it just kind

01:16:07.980 | of happens over sort of 11 to 13, I think for me it was happening.

01:16:12.380 | But it's that sadness of letting go of this beautiful dream which you had in your mind

01:16:18.060 | of eternal life for behaving yourself on Earth.

01:16:22.260 | You would have this beautiful heaven that you could go to and live forever.

01:16:25.900 | And that's very attractive.

01:16:27.780 | And for me personally, that was one of the things that pulled me against it.

01:16:34.740 | It's like it's too good to be true, and it's very convenient that this could be so.

01:16:41.820 | And I have no evidence directly in terms of a scientific sense to support this hypothesis.

01:16:47.260 | And it just became really difficult to reconcile my growth as a scientist.

01:16:53.340 | And I know some people find that reconciliation.

01:16:56.620 | I have not.

01:16:58.380 | Maybe I will one day.

01:17:00.980 | But as a general guiding principle, which I think I obtained from that experience, was

01:17:07.780 | that I have to be extremely guarded about what I want to be true, because it's going

01:17:12.580 | to sway me to say things which are not true if I'm not careful.

01:17:18.320 | And that's not what we're trying to do as scientists.

01:17:21.420 | So you felt from a religious perspective that there was a little bit of a gravitational

01:17:26.700 | field in terms of your opinions, like it was affecting how you could be as a scientist.

01:17:31.860 | Like as a scientific thinker, obviously, you were young.

01:17:35.300 | Yeah, I think that's true.

01:17:39.500 | Whenever there's something you want to be true, it's the ultimate seduction, intellectually.

01:17:48.060 | And I worry about this a lot with UFOs.

01:17:53.500 | It's true already with things like Venus, phosphine, and searching for astrobiological

01:17:58.540 | signals.

01:18:00.120 | We have to guard against this all the way through, from however we're looking for life,

01:18:04.380 | however we're looking for whatever this big question is.

01:18:06.780 | There is a part of us, I think I would love there to be life in the universe.

01:18:11.800 | I hope there is life in the universe, but I've been on record several times as being

01:18:19.220 | fairly firm about trying to remain consciously agnostic about that question.

01:18:25.060 | I don't want to make up my mind about what the answer is before I've collected evidence

01:18:30.500 | to inform that decision.

01:18:31.860 | That's how science should work.

01:18:33.300 | If I already know what the answer is, then what am I doing?

01:18:37.540 | That's not a scientific experiment anymore.

01:18:39.260 | You've already decided, so what are you trying to learn?

01:18:41.740 | What's the point of doing the experiment if you already know what the answer is?

01:18:44.380 | There's no point.

01:18:45.380 | It's so complicated, so if I'm being honest with myself, when I imagine the universe,

01:18:52.300 | so first thing I imagine about our world is that we humans, and me certainly as one particular

01:19:00.140 | human, know very, my first assumption is I know almost nothing about how anything works.

01:19:10.140 | So first of all, that actually applies for things that humans do know, like quantum mechanics,

01:19:17.060 | all the things that there's different expertises that I just have not dedicated to, so even

01:19:21.340 | that's starting point.

01:19:22.340 | But if we take all of knowledge as human civilization, we know almost nothing.

01:19:26.460 | That's kind of an assumption I have, because it seems like we keep discovering mysteries,

01:19:31.220 | and it seems like history, human history, is defined by moments when we said, okay,

01:19:36.820 | we pretty much figured it all out, and then you realize a century later, when you said

01:19:41.900 | that you didn't figure out anything.

01:19:43.460 | Okay, so that's like a starting point.

01:19:45.860 | The second thing I have is I feel like the entirety of the universe is just filled with

01:19:52.820 | alien civilizations.

01:19:57.140 | Statistically, the important thing that enables that belief for me is that they don't have

01:20:05.140 | to be human-like, they can be anything.

01:20:08.500 | And it's just the fact that life exists, and just seeing the way life is on Earth, that

01:20:13.700 | it just finds a way.

01:20:15.580 | It finds a way in so many different complicated environments.

01:20:19.180 | It finds a way.

01:20:20.500 | Whatever that force is, that same force has to find a way elsewhere also.

01:20:26.260 | But then if I'm also being honest, I don't know how many hours in a day I spend seriously

01:20:32.540 | considering the possibility that we're alone.

01:20:35.940 | I don't know when my heart is in mind or filled with wonder, I think about all the different

01:20:42.900 | life that's out there.

01:20:44.920 | But to really imagine that we're alone, like really imagine all the vastness that's out

01:20:49.980 | there, we're alone, not even bacteria.

01:20:53.820 | I would say you don't have to believe that we are alone, but you have to admit it's a

01:20:59.820 | possibility of our ignorance of the universe so far.

01:21:05.260 | You can have a belief about something in the absence of evidence, and Carl Sagan famously

01:21:10.700 | described that as the definition of faith.

01:21:12.620 | If you believe something when there's no evidence, you have faith that there's life in the universe.

01:21:17.740 | But you can't demonstrate, you can't prove it mathematically, you can't show me evidence

01:21:22.560 | of that.

01:21:23.560 | - But is there some, so mathematically math is a funny thing, is there, I mean the way

01:21:28.640 | physicists think, like intuition, so basic reasoning, is there some value to that?

01:21:35.560 | - Well, I'd say we're always, there's certainly, you can certainly make a very good argument,

01:21:40.080 | I think you've kind of already made one, just the vastness of the universe is the default

01:21:45.120 | argument people often turn to, that surely there should be others out there, it's hard

01:21:49.560 | to imagine.

01:21:50.560 | There are of order of 10 to the 22 stars in our observable universe, and so really the

01:21:57.080 | question comes down to what is the probability of one of those 10 to the 22 planets, let's

01:22:02.040 | say, Earth-like planets, if they all have Earth-like planets, going on to form life,

01:22:07.760 | spontaneously.

01:22:08.760 | That's the process of abiogenesis, the spontaneous emergence of life.

01:22:14.200 | - Also the word spontaneous is a funny one.

01:22:16.080 | - Yeah, okay, maybe we won't use spontaneous, but not being, let's say, seeded by some other

01:22:24.960 | civilization or something like that, it naturally emerges.

01:22:27.440 | - 'Cause even the word spontaneous makes it seem less likely, like there's just this chemistry

01:22:33.680 | and an extremely random process.

01:22:34.840 | - Right, it could be a very gradual process, over millions of years of growing complexity

01:22:38.440 | in chemical networks.

01:22:40.240 | - Maybe there's a force in the universe that pushes it towards interesting complexity,

01:22:44.520 | pockets of complexity, that ultimately creates something like life which we can't possibly

01:22:49.480 | define yet.

01:22:50.680 | And sometimes it manifests itself into something that looks like humans, but it could be a

01:22:54.800 | totally different kind of computational information processing system that we're too dumb to even

01:22:59.440 | visualize.

01:23:00.440 | - Yeah, I mean, certainly, it's kind of weird that complexity develops at all, right?

01:23:04.560 | Because it seems like the opposite to our physical intuition, if you're training in

01:23:09.960 | physics, of entropy, that things should, you know, complexity's hard to spontaneously,

01:23:13.640 | or I shouldn't say spontaneously, but hard to emerge in general.

01:23:18.240 | And so that's an interesting problem.

01:23:20.040 | I think there's been, certainly from an evolutionary perspective, you do see growing complexity.

01:23:25.200 | And there's a nice argument, I think it's by Gould, who shows that if you have a certain

01:23:29.960 | amount of complexity, it can either become less complex or more complex through random

01:23:35.080 | mutation.

01:23:36.440 | And the less complex things are stripping away something, something that was necessary

01:23:40.360 | potentially to their survival.

01:23:42.360 | And so in general, that's going to be not particularly useful in its survival, and so

01:23:46.680 | it's going to be detrimental to strip away a significant amount of its useful traits.

01:23:51.240 | Whereas if you add something, the most typical thing that you add is probably not useful

01:23:56.440 | at all.

01:23:57.440 | It probably just doesn't really affect its survival negatively, but neither does it provide

01:24:01.880 | any significant benefit.

01:24:04.380 | But sometimes, on rare occasions, of course, it will be of benefit.

01:24:07.340 | And so if you have a certain level of complexity, it's hard to go back in complexity, but it's

01:24:12.100 | fairly easy to go forward with enough bites at the cherry.

01:24:16.120 | You will eventually build up in complexity.

01:24:17.920 | And that tends to be why we see complexity grow, certainly in an evolutionary sense,

01:24:24.000 | but also perhaps it's operating in chemical networks that led to the emergence of life.

01:24:28.400 | I guess the real problem I have with the numbers game, just to come back to that, is that we

01:24:34.560 | are talking about a certain probability of that occurring.

01:24:38.000 | It may be to go from the primordial soup, however you want to call it, the ingredients

01:24:43.000 | that the Earth started with, the organic molecules, the probability of going from that initial

01:24:47.860 | condition to something that was capable of Darwinian natural selection that maybe we

01:24:53.020 | could define as life.

01:24:55.260 | The probability of that is maybe 1%, 1% of the time that happens, in which case you're

01:24:59.340 | right, the universe will be absolutely teeming with life.

01:25:02.200 | But it could also be 10 to the power of minus 10, in which case it's 1 per galaxy, or 10

01:25:07.060 | to the power of minus 100, in which case the vast majority of universes even do not have

01:25:12.340 | life within it.

01:25:13.340 | - Or 90%.

01:25:14.340 | - Or 90%.

01:25:15.340 | - You said 1%, but it could be 90% if the conditions, the chemical conditions of a planet

01:25:21.620 | are correct, or a moon are correct.

01:25:23.460 | - I admit that.

01:25:24.460 | It could be any of those numbers.

01:25:26.140 | And the challenge is we just have no rigorous reason to expect why 90% is any...

01:25:34.020 | Because we're talking about a probability for probability.

01:25:38.060 | Is 90% more a priori likely than 10 to the power of minus 20?

01:25:43.300 | - Well, the thing is we do have an observation, N of one, of Earth.

01:25:48.940 | And it's difficult to know what to do with that, what kind of intuition you build on

01:25:54.020 | top of that, because on Earth, it seems like life finds a way.

01:25:59.620 | In all kinds of conditions, in all kinds of crazy conditions.

01:26:03.940 | And it's able to build up from the basic chemistry.

01:26:07.340 | You could say, okay, maybe it takes a little bit of time to develop some complicated technology

01:26:13.340 | like mitochondria, I don't know, like photosynthesis.

01:26:15.700 | Fine, but it seems to figure it out and do it extremely well.

01:26:21.500 | - Yeah, but I would say you're describing a different process.

01:26:25.660 | Maybe I'm at fault for separating these two processes, but to me, you're describing basically

01:26:30.740 | natural selection evolution at that point.

01:26:33.340 | Whereas I'm really describing abiogenesis, which is to me a separate distinct process.

01:26:37.900 | - To you limited to human scientists, yes, but why would it be a separate process?

01:26:43.420 | Why is the birth of life a separate process from the process of life?

01:26:48.220 | Why is the...

01:26:49.220 | I mean, we're uncomfortable with the Big Bang.

01:26:54.180 | We're uncomfortable with the first thing, I think.

01:26:56.260 | Like, where did this come from?

01:26:57.620 | - Right, so I think I would say, I just twist that question around and say, you're saying

01:27:01.180 | why is it a different process?

01:27:04.700 | And I would say, why shouldn't it be a different process?

01:27:06.700 | Which isn't really a good defense, except to say that we have knowledge of how natural

01:27:13.100 | selection evolution works.

01:27:14.220 | We think we understand that process.

01:27:16.620 | We have almost no information about the earliest stages of how life emerged on our planet.

01:27:21.980 | It may be that you're right, and it is a part of a continuum.

01:27:25.740 | It may be that it is also a distinct, improbable set of circumstances that led to the emergence

01:27:32.440 | of life.

01:27:33.440 | As a scientist, I'm just trying to be open-minded to both possibilities.

01:27:38.600 | If I assert that life must be everywhere, to me, you run the risk of experimenter's

01:27:44.380 | bias.

01:27:45.820 | If you think you know what the answer is, if you look at an Earth-like planet and you

01:27:50.020 | are preconditioned to think there's a 90% chance of life on this planet, it's going

01:27:55.020 | to, at some level, affect your interpretation of that data.

01:28:00.140 | Whereas if I, however critical you might be of the agnosticism that I impose upon myself,

01:28:07.740 | remain open to both possibilities, then I trust in myself to make a fair assessment

01:28:13.140 | as to the reality of that evidence for life.

01:28:16.620 | - Yeah, but I wonder, sort of scientifically, and that's really beautiful to hear, and inspiring

01:28:23.660 | to hear, I wonder scientifically how many firsts we truly know of, and that we don't

01:28:33.500 | eventually explain as actually a step number one million in a long process.

01:28:42.540 | So I think that's a really interesting thing if there's truly firsts in this universe.

01:28:48.460 | For us, whatever happened at the Big Bang is a kind of first, the origin of stuff.

01:28:53.660 | But it just, again, it seems like history shows that we'll figure out that it's actually

01:28:59.660 | a continuation of something.

01:29:00.860 | But then physicists say that time is emergent, and that our causality in time is a very human

01:29:06.260 | kind of construct, that it's very possible that all of this, so there could be really

01:29:09.940 | firsts of a thing to which we attach a name.

01:29:14.740 | So whatever we call life, maybe there is an origin of it.

01:29:18.580 | - Yeah, and I would also say I'm open to the idea of it being part of a continuation, but

01:29:23.260 | the continuation maybe is more broader, and it's a continuation of chemical systems and

01:29:27.220 | chemical networks.

01:29:28.540 | And what we call this one particular type of chemistry in this behavior of chemistry

01:29:33.620 | is life, but it is just one manifestation of all the trillions of possible permutations

01:29:40.460 | in which chemical reactions can occur.

01:29:42.940 | And we assert specialness to it because that's what we are.

01:29:47.820 | And so it's also true of intelligence, you could extend the same thing and say, you know,

01:29:51.500 | we're looking for intelligent life in the universe, and then you sort of, where do you

01:29:56.420 | define intelligence?

01:29:57.940 | Where's that continuum of something that's really like us?

01:30:00.900 | Are we alone?

01:30:02.220 | There may be a continuum of chemical systems, a continuum of intelligences out there, and

01:30:09.300 | we have to be careful of our own arrogance, of assuming specialness about what we are,

01:30:14.900 | that we are some distinct category of phenomena.

01:30:19.940 | Whereas the universe doesn't really care about what category we are, it's just doing what

01:30:24.140 | it's doing, and doing everything in infinite diversity and infinite combinations, essentially

01:30:29.780 | what it's doing.

01:30:30.780 | And so we are taking this one slice and saying, no, this has to be treated separately.

01:30:37.020 | And I'm open to the idea that it could be a truly separate phenomenon, but it may just

01:30:42.700 | be like a snowflake, every snowflake's different.

01:30:46.860 | It may just be that this one particular iteration is another variant of the vast continuum.

01:30:53.300 | - And maybe the algorithm of natural selection itself is an invention of Earth.

01:30:58.540 | I kind of also tend to suspect that this, whatever the algorithm is, it kind of operates

01:31:04.660 | at all levels throughout the universe.

01:31:07.620 | But maybe this is a very kind of peculiar thing, that where there's a bunch of chemical

01:31:15.880 | systems that compete against each other somehow for survival under limited resources, and

01:31:22.420 | that's a very Earth-like thing.

01:31:24.500 | You have a nice balance of, there's a large number of resources, enough to have a bunch

01:31:29.980 | of different kinds of systems competing, but not so many that they get lazy.

01:31:36.980 | And maybe that's why bacteria were very lazy for a long time, maybe they didn't have much

01:31:41.140 | competition.

01:31:42.140 | - Quite possibly.

01:31:43.140 | I mean, I try to, as fun as it is to get into the speculation about the definitions of life

01:31:51.260 | and what life does, and this gross network of possibilities, honestly for me, the strongest

01:31:58.380 | argument for remaining agnostic is to avoid that bias in assessing data.

01:32:05.620 | I mean, we've seen it.

01:32:06.620 | I mean, Percival Lowell I talked about on my channel, maybe last year or two years ago,

01:32:12.180 | you know, he's a very famous astronomer who in the 19th century was claiming the evidence

01:32:16.340 | of canals on Mars.

01:32:19.260 | And from him, from his perspective, and even at the time, culturally, it was widely accepted

01:32:24.500 | that Mars would of course have life.

01:32:26.300 | I mean, I think it seems silly to us, but it was kind of similar arguments to what we're

01:32:29.820 | using now about exoplanets.

01:32:30.820 | That, well, of course there must be life in the universe, how could it just be here?

01:32:35.020 | And so it seemed obvious to people that when you looked at Mars with its polar caps, even

01:32:38.820 | its atmosphere, had seasons, it seemed obvious to them that that too would be a place where

01:32:45.100 | life not only was present, but had emerged to a civilization which actually was fairly

01:32:49.300 | comparable in technology to our own, because it was building canal systems.

01:32:53.060 | Of course, the canal system seems a bizarre technosignature to us, but it was a product

01:32:58.140 | of their time.

01:32:59.180 | To them, that was the cutting edge in technology.

01:33:02.180 | It should be a warning shot, actually, a little bit for us that if we think, you know, solar

01:33:06.300 | panels or building star links or whatever, space mining is like an inevitable technosignature,

01:33:12.500 | that may be laughably antiquated compared to what other civilizations far more advanced

01:33:17.940 | than us may be doing.

01:33:18.940 | And so anyway, Percival Lowell, I think, was a product of his time that he thought life

01:33:23.500 | was there.

01:33:24.500 | Inevitably, he even wrote about it extensively.

01:33:26.460 | And so when he saw these lines, these lineae on the surface of Mars, to him it was just

01:33:31.540 | obvious they were canals.

01:33:33.400 | And that was experimenters' bias playing out.

01:33:36.260 | He was told, for one, that he had basically the greatest eyesight out of any of his peers.

01:33:40.740 | An ophthalmologist had told him that in Boston, that his eyesight was absolutely spectacular.

01:33:45.220 | So he was convinced everything he saw was real.

01:33:49.420 | And secondly, he was convinced there was life there.

01:33:51.860 | And so to him, it just added up.

01:33:53.980 | And then that kind of wasted decades of research, of treating the idea of Mars being inhabited

01:34:01.100 | by this canal civilization.

01:34:03.980 | But on the other hand, it's maybe not a waste because it is a lesson in history of how we

01:34:07.860 | should be always on guard against our own preconceptions and biases about whether life

01:34:13.580 | is out there.

01:34:14.580 | And furthermore, what types of things life might do if it is there.

01:34:18.300 | - If I were running this simulation, which we'll also talk about because you make the

01:34:22.120 | case against it, but if I were running a simulation, I would definitely put you in a room with an

01:34:26.060 | alien just to see you mentally freak out for hours at a time.

01:34:30.660 | You for sure would have thought, you will be convinced that you've lost your mind.

01:34:36.060 | - I mean, no, not that, but I mean, if we discover life, we discover interesting new

01:34:41.540 | physical phenomena, I think the right approach is definitely to be extremely skeptical and

01:34:45.620 | be very, very careful about things you want to be true.

01:34:49.100 | That's really- - Yeah, I would say, I'm not like some extreme

01:34:51.620 | denialist of evidence.

01:34:53.900 | If there was compelling evidence for life on another planet, I would be the first one

01:34:58.340 | to be celebrating that and be shaking hands with the alien on the White House lawn or

01:35:02.340 | whatever.

01:35:03.340 | I grew up with Star Trek and that was my fantasy was to be Captain Kirk and fly across the

01:35:08.940 | stars meeting other civilizations.

01:35:10.420 | So there's nothing more I'd want to be true, as I've said, but we just have to guard against

01:35:17.060 | it when we're assessing data.

01:35:20.140 | But I have to say, I'm very skeptical that we will ever have that Star Trek moment.

01:35:27.100 | Even if there are other civilizations out there, they're never going to be at a point

01:35:32.900 | which is in technological lockstep with us, similar level of development.

01:35:37.260 | Even intellectually, the idea that they could have a conversation with us, even through

01:35:43.660 | a translator.

01:35:44.660 | I mean, we can't communicate with humpback whales, we can't communicate with dolphins

01:35:48.540 | in a meaningful way, we can sort of bark orders at them, but we can't have abstract conversations

01:35:54.340 | with them about things.

01:35:56.460 | And so the idea that we will ever have that fulfilling conversation, I'm deeply skeptical

01:36:02.820 | of.

01:36:03.820 | And I think a lot of us are drawn to that.

01:36:04.980 | It is maybe a replacement for God to some degree, that Father-Figure civilization that

01:36:09.700 | might step in, teach us the air of our ways, and bestow wisdom upon our civilization.

01:36:15.700 | But they could equally be a giant fungus that doesn't even understand the idea of socialization,

01:36:22.220 | because it's the only entity on its planet.

01:36:24.180 | It just swells over the entire surface.

01:36:28.060 | And it's incredibly intelligent, because maybe each node communicates with each other to

01:36:32.500 | create essentially a giant neural net.

01:36:35.060 | But it has no sense of what communication even is.

01:36:38.500 | And so alien life is out there, surely can be extremely diverse.

01:36:42.540 | I'm pretty skeptical that we'll ever get that fantasy moment I always had as a kid, of having

01:36:48.700 | a dialogue within the civilization.

01:36:50.980 | - So dialogue, yes.

01:36:52.900 | What about noticing them?

01:36:54.020 | What about noticing signals?

01:36:55.900 | Do you hope...

01:36:57.280 | So one thing we've been talking about is getting signatures, biosignatures, technosignatures

01:37:01.300 | about other planets.

01:37:03.100 | Maybe if we're extremely lucky in our lifetime to be able to meet life forms, get evidence

01:37:10.260 | of living or dead life forms on Mars, or the moons of Jupiter and Saturn.

01:37:14.820 | What about getting signals from outer space, interstellar signals?

01:37:18.540 | What would those signals potentially look like?

01:37:22.660 | - That's a hard question to answer, because we are essentially engaging in xenopsychology

01:37:26.580 | to some degree.

01:37:27.580 | We're looking at the activities of another civilization.

01:37:31.220 | A lot of that is inevitable.

01:37:32.220 | - What does the word xenopsychology, I apologize to interrupt, mean?

01:37:35.860 | - Maybe I'm just fabricating that word, really.

01:37:37.580 | But trying to guess at the machinations and motivations of another intelligent being that

01:37:45.420 | was completely evolutionary divorced from us.

01:37:48.460 | - So it's like you said, exo-moons, it's exopsychology, extrasolar psychology.

01:37:53.300 | - Yeah.

01:37:54.500 | - Xenopsychology is another way of maybe making it more grounded.

01:38:00.140 | We can't really guess at their motivations too well, but we can look at the sorts of

01:38:04.180 | behaviors we engage in, and at least look for them.

01:38:08.260 | We're always guilty that when we look for biosignatures, we're really looking for, and

01:38:11.980 | even when we look for planets, we're looking for templates of Earth.

01:38:14.860 | When we look for biosignatures, we're looking for templates of Earth-based life.

01:38:18.220 | When we look for technosignatures, we tend to be looking for templates of our own behaviors

01:38:22.060 | or extrapolations of our behaviors.

01:38:25.060 | So there's a very long list of technosignatures that people have suggested we could look for.

01:38:30.940 | The earliest ones were, of course, radio beacons.

01:38:34.460 | That was sort of Project Osma that Frank Drake was involved in, trying to look for radiosignatures,

01:38:40.060 | which could either be just like blurting out high-power radiosignals saying, "Hey, we're

01:38:46.180 | here," or could even have encoded within them galactic encyclopedias for us to unlock, which

01:38:51.020 | has always been the allure of the radio technique.

01:38:55.140 | But there could also be unintentional signatures.

01:38:58.780 | For example, you could have something like the satellite system that we've produced around

01:39:02.100 | the Earth, the artificial satellite system, Starlink-type systems we mentioned.

01:39:06.360 | You could detect the glint of light across those satellites as they orbit around the

01:39:10.940 | planet.

01:39:12.540 | You could detect a geostationary satellite belt which would block out some light as the

01:39:16.460 | planet transited across the star.

01:39:18.840 | You could detect solar panels, potentially spectrally, on the surface of the planet.

01:39:23.360 | Heat island effects.

01:39:24.360 | New York is hotter than New York State by a couple of degrees because of the heat island

01:39:27.940 | effect of the city.

01:39:28.940 | And so you could thermally map different planets and detect these.

01:39:32.400 | So there's a large array of things that we do that we can go out and hypothesize we could

01:39:39.880 | look for.

01:39:41.000 | And then on the furthest end of the scale, you have things which go far beyond our capabilities,

01:39:45.880 | such as warp drive signatures which have been proposed.

01:39:49.440 | These bright flashes of light or even gravitational wave detections from LIGO could be detected.

01:39:55.260 | You could have Dyson spheres.

01:39:57.160 | The idea of covering a star is completely covered by some kind of structure which collects

01:40:02.200 | all the light from the star to power the civilization.

01:40:05.860 | And that would be pretty easily detectable to some degree because you're transferring

01:40:10.940 | all of the visible light thermodynamically.

01:40:13.880 | It has to be re-emitted to come out as infrared light.

01:40:17.200 | So you'd have an incredibly bright infrared star, yet one that was visibly not present

01:40:23.120 | at all.

01:40:24.120 | And so that would be a pretty intriguing signature to look for.

01:40:27.320 | CB: Is there efforts to look for something like that for Dyson spheres out there, for

01:40:32.200 | the strong infrared signal?

01:40:33.360 | CB: There has been.

01:40:34.360 | Yeah, there has been.

01:40:35.360 | And I think in the literature there was one with the IRAS satellite, which is an infrared

01:40:38.920 | satellite.

01:40:40.000 | They targeted I think of order of 100,000 stars, nearby stars, and found no convincing

01:40:46.600 | examples of what looked like a Dyson sphere star.

01:40:49.320 | And then Jason Wright and his team extended this I think using WISE, which is another

01:40:54.120 | infrared satellite, to look around galaxies.

01:40:57.200 | So could an entire galaxy have been converted into Dyson spheres or a significant fraction

01:41:02.800 | of the galaxy?

01:41:03.800 | Which is basically the Kardashev type 3, right?

01:41:06.720 | This is when you've basically mastered the entire galactic pool of resources.

01:41:12.000 | And again, out of 100,000 nearby galaxies, there appears to be no compelling examples

01:41:17.620 | of what looks like a Dyson galaxy, if you want to call it that.

01:41:21.320 | So that by no means proves that they don't exist or don't happen, but it seems like it's

01:41:28.340 | an unusual behavior for a civilization to get to that stage of development and start

01:41:33.480 | harvesting the entire stellar output.

01:41:36.600 | - Unusually, yes.

01:41:37.600 | And I mean, LIGO is super interesting with gravitational waves, if that kind of experiment

01:41:43.440 | could start seeing some weirdness, some weird signals, that compare to the power of cosmic

01:41:51.720 | phenomena.

01:41:52.720 | - Yeah, yeah.

01:41:53.720 | I mean, it's a whole new window to the universe, not just in terms of astrophysics, but potentially

01:41:57.920 | for technosciences as well.

01:41:59.400 | I have to say with the warp drives, I am skeptical that warp drives are possible, because you

01:42:05.840 | have kind of fundamental problem relativity.

01:42:07.400 | You can either really have relativity, faster than light travel, or causality.

01:42:11.880 | You can only choose two of those three things.

01:42:13.920 | You really can't have all three in a coherent universe.

01:42:17.120 | If you have all three, you basically end up with the possibility of these kind of temporal

01:42:20.520 | paradoxes and time loops and grandfather paradoxes.

01:42:23.000 | - Well, can't there be pockets of causality?

01:42:25.520 | Something like that?

01:42:26.520 | Like where there's pockets of consistent causality?

01:42:30.000 | - You could design it in that way.

01:42:31.400 | You could be, if you had a warp drive or a time machine, essentially, you could be very

01:42:37.040 | conscious and careful of the way you use it, so as to not cause paradoxes or just do it

01:42:42.640 | in a local area or something.

01:42:44.760 | But the real fundamental problem is, you always have the ability to do it.

01:42:49.720 | And so in a vast cosmic universe, if time machines were all over the place, there's

01:42:56.080 | too much risk of someone doing it, right?

01:42:58.200 | Of somebody having the option of essentially breaking the universe with it.

01:43:02.880 | So this is a fundamental problem.

01:43:05.080 | Hawking has this chronology protection conjecture where he said that essentially, this just

01:43:11.240 | can't be allowed, because it breaks all our laws of physics if time travel is possible.

01:43:16.040 | - Current laws of physics, yes.

01:43:17.880 | - Correct, yeah.

01:43:18.880 | And so we'd need to rip up relativity.

01:43:20.760 | I mean, that's the point, is the current laws of physics.

01:43:22.520 | So you'd have to rip up our current law of relativity to make sense of how FTL could

01:43:27.000 | live in that universe, because you can't have relativity, FTL, and causality sit nicely

01:43:31.720 | and play nicely together.

01:43:34.600 | - But we currently don't have quantum mechanics and relativity playing nice together anyway,

01:43:39.080 | so it's not like everything is all a nice little fabric.

01:43:41.440 | - It's certainly not the full picture.

01:43:42.720 | There must be more to go.

01:43:44.760 | - So it's already ripped up, so might as well rip it up a little more.

01:43:50.760 | In the process, actually try to connect the two things.

01:43:53.160 | Because maybe in the unification of the standard model and general relativity, maybe there

01:43:59.720 | lies some kind of new wisdom about warp drives.

01:44:05.160 | So by the way, warp drives is somehow messing with the fabric of the universe to be able

01:44:10.840 | to travel faster than the speed of light?

01:44:12.600 | - Yeah, you're basically bending space-time.

01:44:15.320 | You could also do it with a wormhole, or some other hypothetical FTL.

01:44:20.800 | So this doesn't have to necessarily be the Alcubierre drive, the warp drive.

01:44:24.240 | It could be any faster-than-light system.

01:44:26.080 | As long as it travels superluminally, it will violate causality and relativity.

01:44:30.560 | - And presumably that will be observable with LIGO?

01:44:33.360 | - Potentially, yeah, potentially.

01:44:35.360 | It depends on, I think, the properties of whatever the spacecraft is.

01:44:40.520 | One problem with warp drives is - there's all sorts of problems with warp drives - but

01:44:44.360 | when it -

01:44:45.360 | - Like the start of that sentence, "One problem, the warp drive."

01:44:48.600 | - There's just this one minor problem that we have to get around.

01:44:52.000 | But when it arrives at its destination, it basically collects this vast - it has an event

01:44:58.720 | horizon almost at the front of it - and so it collects all this radiation at the front

01:45:02.440 | as it goes.

01:45:03.680 | And when it arrives, all that radiation gets dumped on its destination, and would basically

01:45:07.680 | completely exterminate the planet it arrives at.

01:45:12.040 | That radiation is also incident within the shell itself.

01:45:14.920 | There's Hawking radiation occurring within the shell, which is pretty dangerous.

01:45:19.720 | And then it also raises all sorts of exacerbations of the Fermi Paradox, of course, as well.

01:45:24.720 | So you might be able to explain why we don't see a galactic empire - even here it's hard.

01:45:31.720 | You might be able to explain why we don't see a galactic empire if everybody's limited

01:45:34.600 | to Voyager 2 rocket speeds of like 20 kilometers per second or something.

01:45:39.760 | But it's a lot harder to explain why we don't see the stars populated by galactic empires

01:45:47.320 | when warp drive is eminently possible.

01:45:49.680 | Because it makes expansion so much more trivial, it makes our life harder.

01:45:56.360 | There's some wonderful simulation work being done out of Rochester where they actually

01:46:00.160 | simulate all the stars in the galaxy - or a fraction of them - and they spawn a civilization

01:46:06.400 | in one of them, and they let it spread out at sub-light speeds.

01:46:10.520 | And actually the very mixing of the stars themselves - because the stars are not static,

01:46:14.560 | they're in orbit of the galactic center and they have crossing paths with each other - if

01:46:19.080 | you just have a range of even like five light years, and your speed is of order of a few

01:46:23.960 | percent the speed of light is the maximum you can muster, you can populate the entire

01:46:28.080 | galaxy within something like a hundred thousand to about a million years or so.

01:46:32.900 | So in other words, a fraction of the lifetime of the galaxy itself.

01:46:36.880 | And so this raises some fairly serious problems, because if any civilization in the entire

01:46:43.880 | history of the galaxy decided to do that, then either we shouldn't be here or we happen

01:46:49.840 | to live in this kind of rare pocket where they chose not to populate to.

01:46:54.680 | And so this is sometimes called 'Fact A' - Hart's Fact A. The Fact A is that a civilization

01:47:01.920 | is not here now, an alien civilization is not in present occupation of the Earth.

01:47:07.640 | And that's difficult to resolve with the apparent ease at which even a small extrapolation of

01:47:15.160 | our own technology could potentially populate a galaxy in far faster than galactic history.

01:47:22.160 | So, to me, by the way, yeah, the Fermi Paradox is truly a paradox for me.

01:47:28.800 | But I suspect that if aliens visit Earth, I suspect if they do, if they are everywhere,

01:47:38.240 | I think they're already here, and we're too dumb to see it.

01:47:42.040 | But leaving that aside, I think we should be able to, in that case, have very strong

01:47:50.040 | obvious signals when we look up at the stars, at the emanation of energy required.

01:47:56.080 | We would see some weirdness, where these are these kinds of stars, and these are these

01:48:03.160 | kinds of stars that are being messed with, like leveraging the nuclear fusion of stars

01:48:08.000 | to do something useful.

01:48:09.800 | The fact that we don't really see that, maybe you can correct me, wouldn't we be able to,

01:48:14.580 | if there is alien civilizations running galaxies, wouldn't we see weirdnesses from an astronomy

01:48:20.140 | perspective with the way the stars are behaving?

01:48:23.020 | CB: Yeah, I mean, it depends exactly what they're doing.

01:48:25.340 | But the Dyson Sphere example is one that we already discussed, where a survey of 100,000

01:48:30.100 | nearby galaxies find that they have all been transformed into Dyson Sphere collectors.

01:48:36.460 | You could also imagine them doing things like, we wrote a paper about this recently, of star

01:48:39.940 | lifting, where you can extend the life of your star by scooping mass off the star.

01:48:43.860 | So you'd be doing stellar engineering, essentially.

01:48:48.580 | If you're doing a huge amount of asteroid mining, you would have a spectral signature,

01:48:53.020 | because you're basically filling the solar system with dust.

01:48:55.780 | By doing that, there'd be debris from that activity.

01:48:58.580 | And so there are some limits on this.

01:49:03.820 | Certainly we don't see bright flashes, which would be one of the consequences of warp drives,

01:49:09.780 | as I said, is as they decelerate, they produce these bright flashes of light.

01:49:13.680 | We don't seem to see evidence of those kinds of things.

01:49:17.700 | We don't see anything obvious around the nearby stars or the stars that we've surveyed in

01:49:21.860 | detail beyond that, that indicate any kind of artificial civilization.

01:49:27.620 | The closest maybe we had was Boyajian's star, that there was a lot of interest in.

01:49:31.300 | There was a star that was just very peculiarly dipping in and out its brightness.

01:49:37.780 | And it was hypothesized for a time that that may indeed be some kind of Dyson-like structure,

01:49:45.020 | so maybe a Dyson sphere that's half-built.

01:49:48.060 | And so as it comes in and out, it's blocking out huge swaths of the star.

01:49:51.780 | It was very difficult to explain, really, with any kind of planet model at the time.

01:49:58.500 | But an easier hypothesis that was proposed was it could just be a large number of comets

01:50:02.780 | or dust or something, or maybe a planet that had broken apart, and as its fragments orbit

01:50:08.020 | around it blocks out starlight.

01:50:10.660 | And it turned out, with subsequent observations of that star, which especially the amateur

01:50:15.660 | astronomy community made a big contribution to as well, that the dips were chromatic,

01:50:22.140 | which was a real important clue that that probably wasn't a solid structure then that

01:50:27.100 | was going around it.

01:50:28.260 | It was more likely to be dust.

01:50:29.860 | Dust is chromatic.

01:50:30.860 | By chromatic I mean it looks different in different colours, so it blocks out more red

01:50:35.300 | light than blue light.

01:50:36.300 | If it was a solid structure, it shouldn't do that.

01:50:41.100 | It should be opaque, a solid metal structure or something.

01:50:44.180 | So that was one of the clear indications.

01:50:45.740 | And the behaviour of and the way the light changed, or the dips changed across wavelength,

01:50:51.140 | was fully consistent with the expectations of what small particulates would do.

01:50:56.620 | And so that's very hard.

01:50:58.060 | The real problem with alien hunting...

01:51:02.700 | The technical term.

01:51:04.900 | This is the real problem.

01:51:05.900 | The one problem.

01:51:06.900 | The one problem with the warp drive and the one problem with alien hunting.

01:51:09.420 | Yes.

01:51:10.420 | Actually, I'd say there's three big problems for me with any search for life, which includes

01:51:14.420 | UFOs, all the way to fossils on Mars, is that aliens have three unique properties as a hypothesis.

01:51:23.020 | One is they have essentially unbounded explanatory capability.

01:51:26.820 | So there's almost no phenomena I can show you that you couldn't explain with aliens,

01:51:31.420 | to some degree.

01:51:32.420 | You could say, well, the aliens just have some super high-tech way of creating that

01:51:36.100 | illusion.

01:51:38.020 | The second one would be unbounded avoidance capacity.

01:51:42.260 | So I might see a UFO tomorrow, and then the next day, and then the next day, and then

01:51:46.700 | predict I should see it on Thursday at the end of the week.

01:51:50.180 | But then I don't see it, but I could always get out of that and say, well, that's just

01:51:54.140 | because they chose not to come here.

01:51:55.700 | You know, they can always avoid future observations fairly easily.

01:52:02.460 | If you survey an exoplanet for biosignatures and you don't see oxygen, you don't see methane,

01:52:07.420 | that doesn't mean there's no one living there.

01:52:09.340 | They could always be either tricking their atmosphere, engineering it - we actually wrote

01:52:13.420 | a paper about that, how you can use lasers to hide your biosignatures as advanced civilization.

01:52:20.860 | Or you could just be living underground or underwater or something where there's no biosignatures.

01:52:24.860 | So you can never really disprove there's life on another planet or on another star.

01:52:30.460 | It has infinite avoidance.

01:52:32.580 | And then finally, the third one is that we have incomplete physical understanding of

01:52:36.620 | the universe.

01:52:37.940 | So if I see a new phenomena - Voyager and Star were a good example of that - we saw

01:52:41.900 | this new phenomena of these strange dips we'd never seen before, it was hypothesized immediately

01:52:46.900 | this could be aliens, like a god of the gaps, but it turned out to be incomplete physical

01:52:51.100 | understanding.

01:52:52.100 | And so that happens all the time.

01:52:54.060 | In the first pulsar that was discovered, same story.

01:52:58.180 | Jocelyn Bell, somewhat tongue-in-cheek, called it 'Little Green Man 1' because it looked

01:53:03.860 | a lot like the radio signature that was expected from an alien civilization.

01:53:08.940 | But of course it turned out to be a completely new type of star that we had never seen before,

01:53:12.900 | which was a neutron star with these two jets coming out the top of it.

01:53:16.980 | And so that's a challenge.

01:53:20.180 | Those three things are really, really difficult in terms of experimental design for a scientist

01:53:26.700 | to work around.

01:53:27.740 | Something that can explain anything, can avoid anything, so it's almost unfalsifiable.

01:53:33.060 | And could always just be, to some degree as you said, we have this very limited knowledge

01:53:37.380 | of the infinite possibilities of physical law, and we're probably only scratching the

01:53:41.780 | surface.

01:53:43.220 | Each time, and we've seen it so often in history, we may just be detecting some new phenomena.

01:53:49.500 | Well that last one, I think I'm a little more okay with making mistakes on.

01:53:55.100 | Yeah, because it's exciting still.

01:53:57.540 | Because no matter what, so you might exaggerate the importance of the discovery, but the whole

01:54:01.540 | point is to try to find stuff in this world that's weird, and try to characterize that

01:54:07.380 | weirdness.

01:54:08.380 | Sure you can throw a little green man as a label on it, but eventually it's as mysterious

01:54:15.140 | and as beautiful, as interesting as little green man.

01:54:18.500 | We tend to think that there's some kind of threshold, but there's all kinds of weird

01:54:22.980 | organisms on this earth that operate very differently than humans that are super interesting.

01:54:27.940 | The human mind is super interesting.

01:54:31.220 | Weirdness and complexity is as interesting in any of its forms as what we might think

01:54:39.140 | from Hollywood what aliens are.

01:54:41.460 | So that's okay, looking for weirdnesses on Mars.

01:54:45.820 | That's one of the best sales pitches to do technosignature work, is that we always have

01:54:49.860 | that as our fallback.

01:54:50.860 | That we're going to look for alien signatures, if we fail we're going to discover some awesome

01:54:56.460 | new physics along the way.

01:54:57.860 | And so any kind of signature that we detect is always going to be interesting.

01:55:04.900 | And so that compels us to have not only the question of looking for life in the universe,

01:55:11.460 | but it gives us a strong scientific grounding as to why this sort of research should be

01:55:16.460 | funded and should be executed, because it always pushes the frontiers of knowledge.

01:55:19.860 | - I wonder if we'll be able to discover and be open enough to a broad definition of aliens,

01:55:26.100 | where we see some kind of technosignature, basically like a Turing test, like this thing

01:55:31.060 | is intelligent.

01:55:33.420 | It's processing information in a very interesting way.

01:55:36.100 | But you could say that about chemistry, you could say that about physics.

01:55:40.740 | Maybe not physics, chemistry.

01:55:41.740 | Like interesting, complex chemistry, you could say that this is processing, this is storing

01:55:47.380 | information, this is propagating information over time.

01:55:51.260 | So I mean, it's a gray area between a living organism that we would call an alien, and

01:55:58.580 | I think that's super interesting, it's able to carry some kind of intelligence.

01:56:01.940 | - Yeah, information is a really useful way to frame what we're looking for though, because

01:56:08.740 | then you're divorced from making assumptions about even a civilization necessarily, or

01:56:14.460 | anything like that.

01:56:15.460 | So any kind of information-rich signature, indeed, you can take things like the light

01:56:20.340 | curve from Boyajian's star and ask, "What is the minimum number of free parameters,

01:56:24.860 | or the minimum information content that must be encoded within this light curve?"

01:56:29.380 | And the hope is that maybe from, a good example would be from a radio signature, you detect

01:56:34.020 | something that has a thousand megabytes of parameters essentially contained within it.

01:56:41.700 | That's pretty clearly at that point not the product of a natural process, or at least

01:56:45.620 | any natural process that we could possibly imagine with our current understanding of

01:56:48.900 | the universe.

01:56:49.980 | And so, thinking that even if we can't decode, which actually I'm skeptical we'd be able

01:56:54.620 | to ever decode in our lifetimes, it would probably take decades to fully ever figure

01:56:59.080 | out what they're trying to tell us.

01:57:00.820 | But if there was a message there, we could at least know that there is high information

01:57:05.020 | content and there is complexity, and that this is an attempt at communication and information

01:57:11.660 | transfer, and leave it to our subsequent generations to figure out what exactly it is they're trying

01:57:17.100 | to say.

01:57:18.100 | - What, again, a wild question, and thank you for...

01:57:21.780 | - Entertaining them.

01:57:22.780 | - Entertaining them, I really, really appreciate that.

01:57:27.460 | But what kind of signal in our lifetime, what kind of thing do you think might happen, could

01:57:32.820 | possibly happen, where the scientific community would be convinced that there's alien civilizations

01:57:40.140 | out there?

01:57:41.140 | Like what, so you already said maybe a strong infrared signature for something like a Dyson

01:57:46.060 | sphere.

01:57:47.060 | - Yeah, that's possibly, that's also to some degree a little bit ambiguous, because...

01:57:51.820 | That's the challenge, sorry to interrupt, is where your brain would be, like you as

01:57:57.980 | a scientist would be like, I know it's ambiguous, but this is really weird.

01:58:03.620 | - I think if you had something, I can imagine something like a prime number sequence, or

01:58:08.580 | a mathematical sequence, like the Fibonacci series, something being broadcasted.

01:58:12.180 | - Mathematically provable that this is not a physical phenomenon.

01:58:15.300 | - Right, I mean, yeah, prime numbers is a pretty good case, because there's no natural

01:58:18.940 | phenomena that produces prime number sequences, it seems to be a purely abstract mathematical

01:58:22.860 | concept as far as I'm aware.

01:58:24.700 | And so if we detected a series of radio blips that were following that sequence, it would

01:58:30.900 | be pretty clear to me, or it could even be Carl Sagan suggested that pi could be encoded

01:58:36.380 | in that, or you might use the hydrogen line, but multiply it by pi, like some very specific

01:58:41.340 | frequency of the universe, like a hydrogen line, but multiply it by an abstract mathematical

01:58:46.680 | constant that would imply strongly that there was someone behind the scenes operating that.

01:58:52.180 | - Sorry, stored in which phenomena though?

01:58:55.180 | - In that case, a radio wave.

01:58:57.380 | But the information, I mean, we kind of toyed with this idea in a video I did about hypothetical

01:59:03.060 | civilization on my channel, but one kind of fun way, I do want to bring this conversation

01:59:09.300 | towards time a little bit, and thinking about not just looking for life and intelligence

01:59:15.260 | around us right now, but looking into the past and even into the future to some degree,

01:59:19.740 | or communicating with the future.

01:59:21.700 | And so we had this fun experiment of imagining a civilization that was born at the beginning

01:59:26.060 | of the history of the galaxy, and being the first, and what it would be like for them.

01:59:29.940 | And they were desperately searching for evidence of life, but couldn't find it.

01:59:33.940 | And so they decided to try and leave something behind for future civilizations to discover,

01:59:38.980 | to tell them about themselves.

01:59:39.980 | But of course, a radio signature's not going to work there, because it has to have a power

01:59:44.420 | source, and that's a piece of machinery, it's going to eventually break down, it's going

01:59:47.460 | to be hard to maintain that for billions of years' timescale.

01:59:51.500 | And so you wanted something that was kind of passive, that doesn't require an energy

01:59:55.060 | source but can somehow transmit information.

01:59:58.580 | Which is hard to think about something that satisfies those criteria.

02:00:02.380 | But there was a proposal by one of my colleagues, Luke Arnold, which inspired a lot of us in

02:00:07.700 | technosignatures, and he suggested that you could build artificial transitors.

02:00:12.540 | So you could build sheets of material that transit in front of the star.

02:00:17.020 | Maybe one thin sheet passes across first, then two, then three, then five, then seven,

02:00:22.500 | so you could follow the prime number sequence of these.

02:00:24.860 | And so there'd be a clear indication that someone had manufactured those.

02:00:28.700 | But they don't require any energy source, because they're just sheets of material in

02:00:32.700 | orbit of the star.

02:00:33.700 | They would eventually degrade from micrometeorites, and maybe they'd always become destabilized.

02:00:37.540 | But they should have lifetimes far exceeding the lifetime of any battery or mechanical

02:00:43.460 | electronic system that we could, at least with our technology, conceive of building.

02:00:47.540 | And so you could imagine extending that.

02:00:49.180 | And how could you encode not just a prime number sequence, but maybe in the spatial

02:00:53.020 | pattern of this very complex light curve we see?

02:00:57.020 | You could encode more and more information through 2D shapes and the way those occultations

02:01:02.700 | happen.

02:01:03.700 | Maybe you could even encode messages and in-depth information.

02:01:10.300 | You could even imagine it being like a lower layer of information, which is just the prime

02:01:14.700 | number sequence.

02:01:15.700 | But then you look closely and you see the smaller divots embedded within those that

02:01:20.200 | have a deeper layer of information to extract.

02:01:24.520 | And so to me, something like that would be pretty compelling, that there was somebody

02:01:28.740 | who had manufactured it.

02:01:29.740 | It's just a very impressive hoax.

02:01:33.180 | That would be pretty compelling evidence in this civilization.

02:01:35.460 | LB: And actually, the methods of astronomy right now are kind of marching towards being

02:01:43.620 | able to better and better detect a signal like that.

02:01:46.100 | CB: Yeah.

02:01:47.100 | I mean, to some degree it's just building bigger aperture in space.

02:01:50.380 | The bigger the telescope, the finer ability to detect those minute signals.

02:01:55.020 | LB: Do you think the current scientific community - another weird question - but just the observations

02:01:59.660 | that are happening now, do you think they're ready for a prime number sequence?

02:02:07.100 | If we're using the current method, the transit timing variation method, do you think you're

02:02:14.340 | ready?

02:02:15.340 | Do you have the tools to detect the prime number sequence?

02:02:18.260 | CB: Yeah, for sure.

02:02:19.980 | I mean, there's 200,000 stars that Kepler monitored, and it monitored them all the time.

02:02:25.020 | It took a photo of each one of them every 30 minutes, measured their brightness, and

02:02:29.780 | it did that for four and a half years.

02:02:32.340 | And so you have already - and Tess is doing it right now, another mission - and so you

02:02:36.020 | have already an existing catalogue.

02:02:38.300 | And people are genuinely scouring through each of those light curves with automated

02:02:43.580 | machine learning techniques.

02:02:44.580 | We even developed some in our own team that can look for weird behavior.

02:02:48.760 | We wrote a code called the weird detector, for instance.

02:02:52.660 | It was just the most generic thing possible.

02:02:55.860 | Don't assume anything about the signal shape, just look for anything that repeats.

02:02:59.500 | The signal shape can be anything, and we kind of learn the template of the signal from the

02:03:03.540 | data itself.

02:03:04.660 | And then it's like a template matching filter to see if that repeats many, many times in

02:03:08.460 | the data.

02:03:09.460 | And so we actually applied that and found a bunch of interesting stuff, but we didn't

02:03:13.260 | see anything that was the prime number sequence, at least on the Kepler data.

02:03:17.980 | That's 200,000 stars, which sounds like a lot, but compared to 200 billion stars in

02:03:23.340 | the Milky Way, it's really just scratching the surface.

02:03:26.700 | - So one, because there could be something much more generalizable than the prime number

02:03:29.940 | sequence, it's ultimately the question of a signal that's very difficult to compress

02:03:35.540 | in the general sense of what compress means.

02:03:38.180 | So maybe as we get better and better machine learning methods that automatically figure

02:03:42.460 | out, analyze the data to understand how to compress it, you'll be able to discover data

02:03:47.960 | that's for some reason not compressible.

02:03:50.840 | But then, you know, compression really is a bottomless pit, because that's really what

02:03:56.060 | intelligence is, is being able to compress information.

02:03:58.700 | - Yeah, and to some degree, the more you...

02:04:01.220 | I would imagine, I don't work in compression algorithms, but I would imagine the more you

02:04:04.180 | compress your signal, the more assumptions that kind of go on behalf of the decoder,

02:04:11.700 | the more skilled they really have to be.

02:04:14.180 | You know, a prime number sequence is completely unencoded information, essentially.

02:04:20.380 | But if you look at the Arecibo message, they were fairly careful with their pixelation

02:04:26.000 | of this simple image they sent, to try and make it as interpretable as possible, to be

02:04:33.960 | that even a dumb alien would be able to figure out what we're trying to show them here.

02:04:38.920 | Because there's all sorts of conventions and rules that are built in that we tend to presume

02:04:44.560 | when we design our messages.

02:04:46.620 | And so if your message is assuming they know how to do an MP3 decoder, a particular compression

02:04:53.980 | algorithm, I'm sure they could eventually reverse engineer it and figure it out.

02:04:58.380 | But you're making it harder for them to get to that point.

02:05:03.260 | So maybe, I always think, you know, you probably would have a two-tier system, right?

02:05:06.020 | You'd probably have some lower-tier key system, and then maybe beneath that you'd have a deeper

02:05:10.840 | compressed layer of more in-depth information.

02:05:14.120 | - What about maybe observing actual physical objects?

02:05:19.040 | So first let me go to your tweet as a source of inspiration.

02:05:22.600 | You tweeted that it's interesting to ponder that if Oort clouds are ever mined by the

02:05:29.080 | systems of alien civilizations, mining equipment from billions of years ago could be in our

02:05:33.640 | Oort cloud, since the Oort clouds extend really, really, really, really far outside the actual

02:05:41.880 | star.

02:05:42.880 | So, you know, mining equipment, just basic boring mining equipment out there.

02:05:47.880 | I don't know if there's something interesting to say about Oort clouds themselves that are

02:05:51.280 | interesting to you, and about possible non-shiny light-emitting mining equipment from alien

02:05:58.800 | civilizations.

02:05:59.800 | - I mean, that's kind of the beauty of the field of technosignatures and looking for

02:06:04.680 | life, is you can find inspiration and intellectual joy in just the smallest little thing that

02:06:12.200 | starts a whole thread of building upon it and wondering about the implications.

02:06:17.800 | And so in this case, I was just really struck by, we kind of mentioned this a little bit

02:06:23.120 | earlier, the idea that stars are not static.

02:06:25.900 | We tend to think of the galaxy as having stars in a certain location from the center of the

02:06:30.880 | galaxy, and they kind of live there.

02:06:32.760 | But in truth, the stars are not only orbiting around the center of the galaxy, but those

02:06:38.660 | orbits are themselves changing over time.

02:06:41.200 | They're processing.

02:06:42.480 | And so in fact, the orbits look more like a spirograph.

02:06:45.040 | If you've ever done those as a kid, they kind of whirl around and trace out all sorts of

02:06:49.480 | strange patterns.

02:06:50.940 | And so the stars intersect with one another.

02:06:54.100 | And so the current closest star to us is Proxima Centauri, which is about 4.2 light years away.

02:07:00.200 | But it will not always be the closest star.

02:07:02.080 | Over millions of years, it will be supplanted by other stars.

02:07:06.160 | In fact, stars that will come even closer than Proxima within just a couple of light

02:07:09.560 | years.

02:07:10.560 | And that's been happening, not just we can project that will happen over the next few

02:07:14.000 | million years, but that's been happening presumably throughout the entire history of the galaxy

02:07:18.820 | for billions of years.

02:07:20.500 | And so if you went back in time, there would have been all sorts of different nearest stars

02:07:24.400 | throughout different stages of the Earth's history.

02:07:26.960 | And those stars are so close that their Oort clouds do intermix with one another.

02:07:32.640 | So the Oort cloud can extend out to even a light year or two around the Earth.

02:07:36.120 | There's some debate about exactly where it ends.

02:07:39.120 | It probably doesn't really have a definitive end, but it kind of more just kind of peters

02:07:42.280 | out more and more and more as you go further away.

02:07:44.880 | LBW - For people who don't know, an Oort cloud, I don't know what the technical definition

02:07:48.200 | is, but a bunch of rocks that kind of, no, objects that orbit the star.

02:07:55.040 | And they can extend really, really far because of gravity.

02:07:56.840 | CB - Correct.

02:07:57.840 | These are objects that probably are mostly icy rich.

02:08:00.720 | They were probably formed fairly similar distances to Jupiter and Saturn, but were scattered

02:08:06.180 | out through the interactions of those giant planets.

02:08:10.520 | We see a circular disk of objects around us, which kind of looks like the asteroid belt,

02:08:14.920 | but just further away called the Kuiper belt.

02:08:16.800 | And then further beyond that, you get the Oort cloud.

02:08:19.400 | And the Oort cloud is not on a disk, it's just a sphere.

02:08:21.960 | It kind of surrounds us in all directions.

02:08:24.480 | So these are objects that were scattered out three-dimensionally in all different directions.

02:08:30.520 | And so those objects are potentially resources for us, especially if you were planning to

02:08:36.760 | do an interstellar mission one day, you might want to mine the water that's embedded within

02:08:41.600 | those and use that as either oxygen or fuel for your rocket.

02:08:45.420 | And so it's quite possible.

02:08:46.920 | There's also some rare earth metals and things like that as well.

02:08:49.760 | But it's quite possible that a civilization might use Oort cloud objects as a jumping

02:08:53.040 | off point.

02:08:56.280 | Or in the Kuiper belt you have things like Planet Nine even.

02:08:58.560 | There might even be objects beyond in the Oort cloud which are actually planet-like

02:09:02.600 | that we just cannot detect.

02:09:03.600 | These objects are very, very faint, so that's why they're so hard to see.

02:09:06.960 | Even Planet Nine is hypothesized to exist, but we've not been able to confirm its existence

02:09:12.160 | because it's at something like a thousand AU away from us, a thousand times the distance

02:09:16.460 | of the Earth from the Sun.

02:09:17.800 | And so even though it's probably larger than the Earth, the amount of light it reflects

02:09:21.620 | from the Sun - the Sun just looks like a star at that point, so far away from it - that

02:09:25.980 | it barely reflects anything back.

02:09:27.660 | It's extremely difficult to detect.

02:09:29.780 | So there's all sorts of wonders that may be lurking out in the outer solar system.

02:09:34.340 | And so this leads you to wonder, you know, in the Oort cloud, that Oort cloud must have

02:09:40.920 | intermixed with other Oort clouds in the past.

02:09:43.900 | And so what fraction of the Oort cloud truly belongs to us, belongs to what was scattered

02:09:51.060 | from Jupiter and Saturn?

02:09:52.940 | What fraction of it could in fact be interstellar visitors?

02:09:56.780 | And of course we got excited about this recently because of 'Oumuamua, this interstellar asteroid,

02:10:02.740 | which seemed to be at the time the first evidence of an interstellar object.

02:10:07.220 | But when you think about the Oort cloud intermixing, it may be that a large fraction of comets

02:10:12.620 | are seeded from the Oort cloud that eventually come in.

02:10:16.860 | Some of those comets may indeed have been interstellar in the first place, that we just

02:10:20.700 | didn't know about through this process.

02:10:24.220 | There even is an example - I can't remember the name - there's an example of a comet that

02:10:26.820 | has a very peculiar spectral signature that has been hypothesized to have actually been

02:10:31.540 | an interstellar visitor, but one that was essentially sourced through this Oort cloud

02:10:36.300 | mixing.

02:10:37.660 | And so this is kind of intriguing.

02:10:41.100 | It also, you know, the outer solar system is just such a, it's like the bottom of the

02:10:44.780 | ocean.

02:10:45.780 | We know so little about what's on the bottom of our own planet's ocean, and we know next

02:10:50.300 | to nothing about what's on the outskirts of our own solar system.

02:10:53.260 | - It's all darkness.

02:10:54.260 | - Yeah.

02:10:55.260 | - And so like, that's one of the things is, to understand the phenomena, we need light.

02:11:01.740 | And we need to see how light interacts with it, or what light emanates from it.

02:11:07.300 | But most of our universe is darkness.

02:11:08.960 | So it's, there could be a lot of interesting stuff.

02:11:11.420 | I mean, this is where your interest is with the cool worlds, and the interesting stuff

02:11:16.020 | lurks in the darkness, right?

02:11:17.820 | - Basically all of us, you know, 400 years of astronomy, our only window into the universe

02:11:22.060 | has been light.

02:11:23.540 | And that has only changed quite recently with the discovery of gravitational waves.

02:11:27.900 | That's now a new window.

02:11:30.380 | And hopefully, well to some degree, I guess, solar neutrinos we've been detecting for a

02:11:34.340 | while, but they come from the sun, not interstellar space.

02:11:36.300 | But we may be able to soon detect neutrino messages, as has even been hypothesized as

02:11:40.180 | a way of communicating between civilizations as well, or just do neutrino telescopes to

02:11:44.420 | study the universe.

02:11:46.620 | And so there's a growing interest in what we'd call multi-messenger astronomy now.

02:11:50.980 | So not just messages from light, but messages from these other physical packets of information

02:11:58.540 | that are coming our way.

02:12:00.500 | But when it comes to the outer solar system, light really is our only window.

02:12:04.660 | There's two ways of doing that.

02:12:06.700 | One is you detect the light from the Oort cloud object itself, which as I just said,

02:12:10.100 | is very, very difficult.

02:12:11.700 | There's another trick, which we do in the Kuiper belt especially, and that's called

02:12:16.340 | inoculation.

02:12:18.020 | And so sometimes those objects will just pass in front of a distant star just coincidentally.

02:12:24.060 | These are very, very brief moments.

02:12:25.740 | They last for less than a second.

02:12:26.740 | And so you have to have a very fast camera to detect them, which conventionally astronomers

02:12:31.820 | don't usually build fast cameras.

02:12:33.660 | Most of the phenomena we observe occurs on hours, minutes, days even.

02:12:37.460 | But now we're developing cameras which can take thousands of images per second, and yet

02:12:42.420 | do it at the kind of astronomical fidelity that we need for this kind of precise measurement.

02:12:47.460 | And so you can see these very fast dips.

02:12:50.660 | You even get these kind of diffraction patterns that come around, which are really cool to

02:12:54.500 | look at.

02:12:55.620 | And I kind of love it because it's almost like passive radar.

02:12:59.780 | You have these pinpricks of light.

02:13:01.540 | Imagine that you live in a giant black sphere, but there's these little pinholes that have

02:13:06.740 | been poked, and through those pinholes almost laser light is shining through.

02:13:11.620 | And inside this black sphere, there are unknown things wandering around, drifting around that

02:13:17.260 | we are trying to discover.

02:13:18.740 | And sometimes they will pass in front of those little pencil-thin laser beams, block something

02:13:23.500 | out, and so we can tell that it's there.

02:13:25.660 | And it's not an active radar, because we didn't actually beam anything out and get a reflection

02:13:29.740 | off, which is what the Sun does.

02:13:31.340 | The Sun's light comes off and then comes back.

02:13:32.980 | That's more like an active radar system.

02:13:34.740 | It's more like a passive radar system where we are just listening very intently.

02:13:39.260 | And so I'm kind of so fascinated by that, the idea that we could map out the rich architecture

02:13:47.940 | of the outer solar system just by doing something that we could have done potentially for a

02:13:52.340 | long time, which is just listening in the right way, just tuning our instrumentation

02:13:57.540 | to the correct way of not listening, but viewing the universe to catch those objects.

02:14:03.620 | LB: Yeah, I mean, it's really fascinating.

02:14:05.940 | It seems almost obvious that your efforts, when projected out over like 100, 200 years,

02:14:12.540 | will have a really good map through even methods like basically transit timing, high-resolution

02:14:17.500 | transit timing, but basically the planetary and the planet satellite movements of all

02:14:24.860 | the different star systems out there.

02:14:27.300 | CB: Yeah, and it could revolutionize the way we think about the solar system.

02:14:30.020 | I mean, that revolution has happened several times in the past.

02:14:33.740 | When we discovered Vesta in the 19th century, that was I think the seventh planet for a

02:14:40.180 | while, or the eighth planet when it was first discovered.

02:14:42.340 | And then we discovered Ceres, and there was a bunch of asteroid objects, Janus.

02:14:46.860 | And so for a while, the textbooks had something like 13 planets in the solar system.

02:14:52.580 | And then that was just a new capability that was emerging to detect those small objects.

02:14:56.180 | And then we ripped that up and said, "No, no, we're going to change the definition of

02:14:59.260 | a planet."

02:15:00.260 | And then the same thing happened when we started looking at the outer skirts of the solar system.

02:15:03.820 | Again, we found Eris, we found Sedna, these objects which resembled Pluto.

02:15:09.380 | And more and more of them we found, make, make.

02:15:11.980 | And eventually, we again had to rethink the way we even contextualize what a planet is,

02:15:18.820 | and what the nature of the outer solar system is.

02:15:22.100 | So regardless as to what you think about the debate about whether Pluto should be devoted

02:15:25.740 | or not, which I know often evokes a lot of strong feelings, it is an incredible achievement

02:15:31.220 | that we were able to transform our view of the solar system in a matter of years just

02:15:38.380 | by basically charge-coupled devices, the things that's in cameras.

02:15:44.620 | The invention of that device allowed us to detect objects which were much further away,

02:15:48.900 | much fainter, and revealed all of this stuff that was there all along.

02:15:52.840 | And so that's the beauty of astronomy, there's just so much to discover, and even in our

02:15:59.260 | own backyard.

02:16:00.260 | - Do you ever think about this?

02:16:01.820 | Do you imagine, what are the things that will completely change astronomy over the next

02:16:05.900 | hundred years?

02:16:06.900 | Like if you transport yourself forward a hundred years, what are the things that will blow

02:16:11.540 | your mind when you look at, "Wait, what?"

02:16:14.540 | Would it be just a very high-resolution mapping of things?

02:16:18.140 | Like holy crap, one surprising thing might be, holy crap, there's Earth-like moons everywhere.

02:16:27.840 | Another one could be just totally different devices for sensing.

02:16:30.920 | - Yeah, I think usually astronomy moves forward dramatically, and science in general, when

02:16:36.960 | you have a new technological capability come online for the first time.

02:16:41.360 | And we kind of just gave examples of that there with the solar system.

02:16:44.940 | So what kind of new capabilities might emerge in the next 100 years?

02:16:49.220 | The capability I would love to see is not just, I mean, in the next 10, 20 years we're

02:16:54.280 | hoping to take these pale blue dot images we spoke about.

02:16:57.160 | So that requires building something like JWST, but on an even larger scale, and optimized

02:17:02.360 | for direct imaging.

02:17:03.360 | You'd have to have either a coronagraph or a star shade or something to block out the

02:17:06.600 | starlight and reveal those pale blue dots.

02:17:09.600 | So in the next sort of decades, I think that's the achievement that we can look forward to

02:17:14.860 | in our lifetimes, is to see photos of other Earths.

02:17:19.020 | Going beyond that, maybe in our lifetimes, towards the end of our lifetimes perhaps,

02:17:22.720 | I'd love it if we, I think it's technically possible as Breakthrough Starshot are giving

02:17:27.200 | us a lot of encouragement with, to maybe send a small probe to the nearest stars and start

02:17:32.440 | actually taking high resolution images of these objects.

02:17:35.520 | There's only so much you can do from far away if you want to have, and we can see it in

02:17:40.280 | the solar system.

02:17:41.280 | I mean, there's only so much you can learn about Europa by pointing a Hubble Space Telescope

02:17:44.320 | at it.

02:17:45.320 | But if you really want to understand that Moon, you're going to have to send something

02:17:48.180 | to orbit it to hopefully land on it and drill down to the surface.

02:17:52.360 | And so the idea of even taking a flyby and doing a snapshot photo that gets beamed back

02:17:58.280 | that could be, doesn't even have to be more than 100 pixels by 100 pixels, even that would

02:18:03.160 | be a completely game-changing capability to be able to truly image these objects.

02:18:09.040 | And maybe at home in our own solar system, we can certainly get to a point where we produce

02:18:16.280 | crude maps of exoplanets.

02:18:19.520 | One of the, kind of the ultimate limit of what a telescope could do is governed by its

02:18:24.280 | size.

02:18:25.340 | And so the largest telescope you could probably ever build would be one that was the size

02:18:28.400 | of the Sun.

02:18:29.400 | There's a clever trick for doing this without physically building a telescope that's the

02:18:33.360 | size of the Sun, and that's to use the Sun as a gravitational lens.

02:18:37.320 | This was proposed, I think, by Van Eschleman in like 1979, but it builds upon Einstein's

02:18:43.040 | theory of general relativity, of course, that there is a warping of light, a bending of

02:18:47.920 | light from the Sun's gravitational field.

02:18:50.360 | And so a distant starlight, it's like a magnifying glass, anything that bends light is basically

02:18:55.720 | can be used as a telescope.

02:18:57.440 | It's going to bend light to a point.

02:18:59.400 | Now it turns out the Sun's gravity is not strong enough to create a particularly great

02:19:04.080 | telescope here, because the focus point is really out in the Kuiper Belt.

02:19:08.360 | It's at 550 astronomical units away from the Earth, so 550 times further away from the

02:19:14.320 | Sun than we are.

02:19:15.320 | And that's beyond any of our spacecraft have ever gone.

02:19:17.920 | So you have to send a spacecraft to that distance, which would take 30, 40 years, even optimistically

02:19:24.760 | improving our chemical propulsion system significantly.

02:19:27.840 | You'd have to bound it into that orbit, but then you could use the entire Sun as your

02:19:32.560 | telescope, and with that kind of capability, you could image planets to kilometer-scale

02:19:38.880 | resolution from afar.

02:19:41.120 | And that really makes you wonder.

02:19:43.720 | If we can conceive, maybe we can't engineer it, but if we can conceive of such a device,

02:19:49.880 | what might other civilizations be currently observing about our own planet?

02:19:56.080 | And perhaps that is why nobody is visiting us, because there is so much you can do from

02:20:03.200 | afar that to them, that's enough.

02:20:06.800 | Maybe they can get to the point where they can detect our radio leakage, they can detect

02:20:10.200 | our terrestrial television signals, they can map out our surfaces, they can tell we have

02:20:17.160 | cities, they can even do infrared mapping of the heat island effect, all this kind of

02:20:20.560 | stuff.

02:20:21.560 | They can tell the chemical composition of our planet.

02:20:23.920 | And so that might be enough.

02:20:25.040 | Maybe they don't need to come down to the surface and do anthropology and see what our

02:20:30.120 | civilization is like.

02:20:32.360 | But there's certainly a huge amount you can do, which is significantly cheaper to some

02:20:36.600 | degree than flying there, just by exploiting cleverly the physics of the universe itself.

02:20:42.040 | - So your intuition is, and this very well might be true, that observation might be way

02:20:48.680 | easier than travel.

02:20:51.520 | From our perspective, from an alien perspective, we could get very high resolution imaging

02:20:57.960 | before we could ever get there.

02:20:59.560 | - It depends on what information you want.

02:21:01.920 | If you want to know the chemical composition, and you want to know kilometer-scale maps

02:21:07.720 | of the planet, then you could do that from afar with some version of these kind of gravitational

02:21:13.440 | lenses.

02:21:14.440 | If you want to do better than that, if you want to image a newspaper set on the porch

02:21:19.040 | of somebody's house, you're going to have to fly there.

02:21:21.640 | There's no way, unless you had a telescope the size of Sagittarius A* or something, you

02:21:26.440 | just simply cannot collect enough light to do that from many light-years away.

02:21:32.160 | So there is certainly reasons why visiting will always have its place, depending on what

02:21:39.720 | kind of information you want.

02:21:42.360 | We propose in my team actually that the Sun is the ultimate pinnacle of telescope design,

02:21:49.280 | but flying to a thousand AU is a real pain in the butt because it's just going to take

02:21:53.200 | so long.

02:21:54.200 | And so a more practical way of achieving this might be to use the Earth.

02:21:59.280 | Now the Earth doesn't have anywhere near enough gravity to create a substantial gravitational

02:22:04.160 | lens, but it has an atmosphere.

02:22:06.840 | And that atmosphere refracts light, it bends light.

02:22:10.920 | So whenever you see a sunset, just as the Sun is setting below the horizon, it's actually

02:22:16.360 | already beneath the horizon.

02:22:18.600 | It's just the light is bending through the atmosphere.

02:22:21.880 | It's actually already about half a degree down beneath, and what you're seeing is that

02:22:26.880 | curvature of the light path.

02:22:28.760 | And your brain interprets it, of course, to be following a straight line because your

02:22:32.080 | brain always thinks that.

02:22:34.520 | And so you can use that bending.

02:22:36.160 | Whenever you have bending, you have a telescope.

02:22:38.040 | And so we've proposed to my team that you could use this refraction to similarly create

02:22:42.960 | an Earth-sized telescope.

02:22:43.960 | - Called the Terrascope.

02:22:44.960 | - The Terrascope, yeah.

02:22:45.960 | - We have a great video on this.

02:22:46.960 | - Yeah.

02:22:47.960 | - Do you have a paper on the Terrascope?

02:22:50.960 | - I do, yeah.

02:22:51.960 | - Great.

02:22:52.960 | - Sometimes I get confused with this because I've heard of an Earth-sized telescope because

02:22:55.400 | of the, maybe you've heard of the Event Horizon Telescope, which took an image of, well it's

02:23:00.200 | taking an image right now of the center of our black hole.

02:23:03.040 | And it's very impressive, and it previously did Messier 87, a nearby supermassive black

02:23:07.780 | hole.

02:23:08.780 | And so those images were interferometric.

02:23:10.860 | So they were small telescopes scattered across the Earth, and they combined the light paths

02:23:16.060 | together interferometrically to create effectively an Earth-sized angular resolution.

02:23:23.400 | Telescopes always have two properties.

02:23:24.920 | There's the angular resolution, which is how small of a thing you can see on the surface,

02:23:29.200 | and then there's the magnification.

02:23:31.120 | How much brighter does that object get versus just your eye or some small object?

02:23:35.880 | Now what the Event Horizon Telescope did, it traded off amplification or magnification

02:23:45.000 | for the angular resolution.

02:23:46.240 | That's what it wanted.

02:23:47.240 | It wanted that high angular resolution, but it doesn't really have much photon collecting

02:23:50.400 | power because each telescope individually is very small.

02:23:53.600 | The Telescope is different because it is literally collecting light with a light bucket, which

02:23:59.520 | is essentially the size of the Earth.

02:24:01.560 | And so that gives you both benefits, potentially.

02:24:04.560 | Not only the high angular resolution that a large aperture promises you, but also actually

02:24:09.320 | physically collects all those photons.

02:24:10.840 | So you can detect light from very, very far away, the very outer edges of the universe.

02:24:16.480 | And so we propose this as a possible future technological way of achieving these extreme

02:24:25.440 | goals, ambitious goals we have in astronomy.

02:24:29.680 | But it's a very difficult system to test because you essentially have to fly out to these focus

02:24:34.720 | points, and these focus points lie beyond the Moon.

02:24:37.440 | So you have to have someone who is willing to fly beyond the Moon and hitchhike an experimental

02:24:44.120 | telescope onto it and do that cheaply.

02:24:46.880 | If it was something doing low Earth orbit, it'd be easy.

02:24:49.200 | You could just attach a CubeSat to the next Falcon 9 rocket or something and test it out.

02:24:53.640 | It'd probably only cost you a few tens of thousands of dollars, maybe a hundred thousand

02:24:57.040 | dollars.

02:24:58.040 | But there's basically no one who flies out that far, except for bespoke missions such

02:25:03.840 | as a mission that's going to Mars or something that would pass through that kind of space.

02:25:09.960 | And they typically don't have a lot of leeway and excess payload that they're willing to

02:25:14.840 | strap on for radical experiments.

02:25:17.240 | So that's been the problem with it.

02:25:18.920 | In theory it should work beautifully, but it's a very difficult idea to experimentally

02:25:23.520 | test.

02:25:24.520 | Can you elaborate why the focal point is that far away?

02:25:27.760 | So you get about half a degree bend from the Earth's atmosphere when you're looking at

02:25:32.760 | the Sun at the horizon, and you get that two times over if you're outside of the planet's

02:25:36.920 | atmosphere.

02:25:37.920 | Because the star is half a bend to you, still on the horizon, and half a degree back out

02:25:42.800 | either way.

02:25:43.800 | So you get about a one degree bend.

02:25:44.800 | You take the radius of the Earth, which is about 7,000 kilometers, and do your arctan

02:25:49.440 | function, you'll end up with a distance that's about...

02:25:52.080 | It's actually the inner focal point is about two thirds the distance of the Earth-Moon

02:25:55.800 | system.

02:25:56.800 | The problem with that inner focal point is not useful, because that light ray path had

02:26:01.400 | to basically scrape the surface of the Earth.

02:26:03.840 | So it passes through the clouds, it passes through all the thick atmosphere, it gets

02:26:06.960 | a lot of extinction along the way.

02:26:09.160 | If you go higher up in altitude, you get less extinction.

02:26:12.320 | In fact, you can even go above the clouds, and so that's even better, because the clouds

02:26:15.520 | obviously are going to be a pain in the neck for doing anything optical.

02:26:18.940 | But the problem with that is that the atmosphere, because it gets thinner at higher altitude,

02:26:22.660 | it bends light less.

02:26:24.500 | And so that pushes the focal point out.

02:26:26.900 | So the most useful focal point is actually about three or four times the distance of

02:26:31.140 | the Earth-Moon separation.

02:26:32.780 | And so that's what we call one of the Lagrange points, essentially.

02:26:36.060 | And so there there's a stable orbit, it's kind of the outermost stable orbit you could

02:26:39.300 | have around the Earth.

02:26:41.140 | So the atmosphere does bad things to the signal.

02:26:46.620 | Yeah, it's absorbing light.

02:26:49.220 | Is that possible to reconstruct, to remove the noise, whatever?

02:26:54.260 | So it's just strength, it's nothing else?

02:26:57.180 | It's possible to reconstruct.

02:26:58.180 | I mean, to some degree we do this as a technology called adaptive optics that can correct for

02:27:03.020 | what's called wavefront errors that happen through the Earth's atmosphere.

02:27:06.140 | The Earth's atmosphere is turbulent, it is not a single plane of air of the same density,

02:27:12.580 | there's all kind of wiggles and currents in the air.

02:27:15.540 | And so that each little layer is bending light in slightly different ways.

02:27:20.820 | And so the light actually kind of follows a wiggly path on its way down.

02:27:24.500 | What that means is that two light rays which are traveling at slightly different spatial

02:27:29.140 | separations from each other will arrive at the detector at different times, because one

02:27:33.820 | maybe goes on more or less a straight path and the one wiggles down a bit more before

02:27:37.140 | it arrives.

02:27:38.140 | And so you have an incoherent light source.

02:27:41.980 | And when you're trying to do imagery construction, you always want a coherent light source.

02:27:45.040 | So the way they correct for this is that if this path had to travel a little bit faster,

02:27:50.140 | the straight one goes faster and the wiggly one takes longer, the mirror is deformable.

02:27:53.980 | And so you actually bend the mirror on the straight one down a little bit to make it

02:27:58.940 | an equivalent light path distance.

02:28:01.140 | So the mirror itself has all these little actuators, it's actually made up of like thousands

02:28:05.980 | of little elements, almost looks like a liquid mirror, because they can manipulate it in

02:28:10.060 | kind of real time.

02:28:11.480 | And so they scan the atmosphere with a laser beam to tell what the deformations are in

02:28:15.100 | the atmosphere, and then make the corrections to the mirror to account for it.

02:28:19.060 | That's amazing.

02:28:20.060 | So you could, you could do something like this for the terrascope, but it would be...

02:28:24.980 | It's cheaper and easier to go above the atmosphere and just fly out.

02:28:28.580 | I think so.

02:28:29.580 | It would be very, it's a very, that's a very challenging thing to do.

02:28:32.220 | And normally when you do adaptive optics, as it's called, you're looking straight up.

02:28:35.780 | So you're, you know, or very close to straight up.

02:28:38.420 | If you look at the horizon, we basically never do astronomical observations on the horizon,

02:28:42.280 | because you're looking through more atmosphere.

02:28:44.560 | If you go straight up, you're looking at the thinnest portion of atmosphere possible.

02:28:47.040 | But as you go closer and closer towards the horizon, you're increasing what we call the

02:28:50.480 | air mass, the amount of air you have to travel through.

02:28:53.680 | So here it's kind of the worst case because you're going through the entire atmosphere

02:28:58.040 | in and out again with a terrascope.

02:29:00.640 | So you'd need a very impressive adaptive optics system to correct for that.

02:29:04.640 | So yeah, I would say it's probably simpler, at least for proof of principle, just to test

02:29:09.560 | it with having some satellite that was at a much wider orbit.

02:29:15.600 | - Now speaking of traveling out into deep space, you already mentioned this a little

02:29:19.640 | bit.

02:29:22.120 | You made a beautiful video called "The Journey to the End of the Universe".

02:29:26.240 | And sort of at the start of that, you're talking about Alpha Centauri.

02:29:30.880 | So what would it take for humans or for human-like creatures to travel out to Alpha Centauri?

02:29:37.960 | - There's a few different ways of doing it, I suppose.

02:29:42.700 | One is, it depends on how fast your ship is.

02:29:44.400 | That's always going to be the determining factor.

02:29:46.580 | If we devised some interstellar propulsion system that could travel a fraction of the

02:29:51.400 | speed of light, then we could do it in our lifetimes, which is I think what people normally

02:29:57.340 | dream of when they think about interstellar propulsion and travel.

02:30:01.360 | You could literally step onto the spacecraft, maybe a few years later you step off on Alpha

02:30:05.660 | Centauri B, you walk around the surface and come back and visit your family.

02:30:10.120 | There would be of course a lot of relativistic time dilation as a result of that trip.

02:30:14.740 | You would have aged a lot less than people back on Earth by traveling close to the speed

02:30:18.640 | of light for some fraction of time.

02:30:22.400 | The challenge of this of course is that we have no such propulsion system that can achieve

02:30:26.280 | this.

02:30:27.280 | - But do you think it's possible?

02:30:28.280 | You have a paper called the Halo Drive, fuel-free relativistic propulsion of large masses via

02:30:37.400 | recycled boomerang photons.

02:30:40.400 | So do you think, first of all, what is that?

02:30:43.640 | And second of all, how difficult are alternate propulsion systems?

02:30:49.000 | - Yeah, so before I took on the Halo Drive, there was an idea, because I think the Halo

02:30:55.640 | Drive is not gonna solve this problem.

02:30:58.760 | I'll talk about the Halo Drive in a moment, but the Halo Drive is useful for a civilization

02:31:02.480 | which is a bit more advanced than us, that has spread across the stars, and is looking

02:31:05.640 | for a cheap highway system to get across the galaxy.

02:31:09.760 | For that first step, just to context that, the Halo Drive requires a black hole.

02:31:16.580 | So that's why you're not gonna be able to do this on the Earth right now.

02:31:20.040 | But there are lots of black holes in the Milky Way, so that's the good news.

02:31:22.160 | So we'll come to that in a moment.

02:31:23.240 | But if you're trying to travel to Alpha Centauri without a black hole, then there are some

02:31:29.840 | ideas out there.

02:31:30.840 | There was a Project Daedalus and Project Icarus that were two projects that the British Interplanetary

02:31:36.560 | Society conjured up on a 20, 30-year timescale.

02:31:40.680 | And they asked themselves, if we took existing and speculatively but realistic attempts at

02:31:47.320 | future technology that are emerging over the next few decades, how far could we push into

02:31:51.560 | the stellar travel system?

02:31:54.760 | And they settled on fusion drives in that.

02:31:58.200 | So if we had the ability to essentially either detonate - you can always imagine nuclear

02:32:03.200 | fission or nuclear fusion bombs going off behind the spacecraft and propelling it that

02:32:07.680 | way, or having some kind of successful nuclear fusion reaction, which obviously we haven't

02:32:14.320 | really demonstrated yet as a propulsion system - then you could achieve something like 10%

02:32:18.760 | the speed of light in those systems.

02:32:20.520 | But these are huge spacecrafts.

02:32:22.680 | I think you need a huge spacecraft if you're going to take people along.

02:32:26.360 | The conversation recently has actually switched, and that idea seems a little bit antiquated

02:32:31.600 | now.

02:32:32.600 | And most of us have kind of given up on the idea of people physically, biologically, stepping

02:32:38.120 | on board the spacecraft.

02:32:40.240 | And maybe we'll be sending something that's more like a microprobe that maybe just weighs

02:32:43.760 | a gram or two, and that's much easier to accelerate.

02:32:47.360 | You could push that with a laser system to very high speed, get it to maybe 20% the speed

02:32:51.520 | of light.

02:32:52.520 | It has to survive the journey.

02:32:53.520 | Probably a large fraction of them won't survive the journey, but they're cheap enough that

02:32:56.560 | you could maybe manufacture millions of them.

02:32:59.080 | And some of them do arrive and are able to send back an image.

02:33:03.480 | Maybe even if you wanted to have a person there, we might have some way of doing a telepresence,

02:33:09.280 | or some kind of delayed telepresence, or some kind of reconstruction of the planet which

02:33:14.920 | is sent back, so you can digitally interact with that environment in a way which is not

02:33:20.680 | real-time, but representative of what that planet would be like to be on the surface.

02:33:25.280 | So we might be more like digital visitors to these planets.

02:33:28.720 | Certainly far easier, practically, to do that than physically forcing this wet chunk of

02:33:34.880 | meat to fly across space to do that.

02:33:39.640 | And so that's maybe something we can imagine down the road.

02:33:44.560 | The Halo Drive, as I said, is thinking even further ahead.

02:33:48.320 | And if you did want to launch large masses - large masses could even be planet-sized

02:33:54.440 | things, in the case of the Halo Drive - you can use black holes.

02:33:58.640 | So this is kind of a trick of physics.

02:34:02.080 | I often think of the universe as like a big computer game, and you're trying to find cheat

02:34:07.720 | codes, hacks, exploits that the universe didn't intend for you to use.

02:34:12.680 | But once you find them, you can address all sorts of interesting capabilities that you

02:34:17.000 | didn't previously have.

02:34:19.320 | And the Halo Drive does that with black holes.

02:34:21.720 | So if you have two black holes, which is a very common situation - a binary black hole

02:34:25.160 | - and they're in spiraling towards each other.

02:34:28.440 | LIGO has detected, I think, dozens of these things, maybe even over a hundred at this

02:34:31.560 | point.

02:34:32.560 | And these things, as they merge together, the pre-merger phase, they're orbiting each

02:34:38.120 | other very, very fast, even close to the speed of light.

02:34:41.180 | And so Freeman Dyson, before he passed away, I think in the 70s, had this provocative paper

02:34:46.260 | called Gravitational Machines, and he suggested that you could use neutron stars as an interstellar

02:34:51.080 | propulsion system.

02:34:53.560 | And neutron stars are sort of the lower mass version of a binary black hole system, essentially.

02:35:00.640 | In this case, he suggested just doing a gravitational slingshot.

02:35:04.280 | Just fly your spacecraft into this very compact and relativistic binary system.

02:35:13.100 | And you do need neutron stars because if there were two stars, they'd be physically touching

02:35:16.740 | each other.

02:35:17.840 | So the neutron stars are so small, like 10 kilometers across, they can get really close

02:35:21.380 | to each other and have these very, very fast orbits with respect to each other.

02:35:25.940 | You shoot your spacecraft through, right through the middle, like through the eye of a needle,

02:35:30.060 | and you do a slingshot around one of them.

02:35:32.220 | And you do it around the one that's coming sort of towards you.

02:35:35.340 | So one of them will be coming away, one will be coming towards you at any one point.

02:35:38.380 | And then you could basically steal some of the kinetic energy in the slingshot.

02:35:42.060 | In principle, you can set up to twice the speed.

02:35:45.380 | You can take your speed, and it becomes your speed plus twice the speed of the neutron

02:35:50.820 | star in this case.

02:35:51.820 | And that would be your new speed after the slingshot.

02:35:54.700 | This seems great because it's just free energy, basically.

02:35:57.780 | You're not doing any, you know, you're not generating to have a nuclear power reactor

02:36:01.180 | or anything to generate this, you're just stealing it.

02:36:03.140 | And indeed, you could get to relativistic speeds this way.

02:36:06.020 | So I loved that paper, but I had a criticism.

02:36:09.380 | And the criticism was that this is like trying to fly your ship into a blender, right?

02:36:13.820 | This is two neutron stars, which have huge tidal forces, and they're whipping around

02:36:20.380 | each other once every second or even less than a second.

02:36:23.860 | And you're trying to fly your spaceship and do this maneuver that is pretty precarious.

02:36:28.340 | And so it just didn't seem practical to me to do this.

02:36:30.860 | But I loved it.

02:36:32.220 | And so I took that idea, and this is how science is.

02:36:35.340 | It's iterative.

02:36:36.340 | It's, you take a previous great man's idea, and you just sort of maybe slightly tweak

02:36:40.700 | it and improve it.

02:36:41.700 | That's how I see the halo drive.

02:36:44.060 | And I just suggested, why not replace those out for black holes, which are certainly very

02:36:48.180 | common.

02:36:49.260 | And rather than flying your ship into that hellhole of a blender system, you just stand

02:36:55.300 | back and you fire a laser beam.

02:36:57.540 | Now because black holes have such intense gravitational fields, they can bend light

02:37:01.660 | into complete 180s.

02:37:02.660 | They can actually become mirrors.

02:37:04.900 | So the sun bends light by maybe a fraction of a degree through gravitational lensing.

02:37:10.620 | But a compact object like a black hole can do a full 180.

02:37:13.900 | In fact, obviously, if you went too close, if you put the laser beam too close, the black

02:37:18.100 | hole would just fall into it and never come back out.

02:37:20.380 | So you just kind of push it out, push it out, push it out until you get to a point where

02:37:23.500 | it's just skirting the event horizon.

02:37:26.140 | And then that laser beam skirts around and it comes back.

02:37:29.100 | Now the laser beam wants to do a gravitational, I mean it is doing a gravitational slingshot,

02:37:33.380 | but laser, I mean light photons, can't speed up, unlike the spaceship case.

02:37:38.860 | So instead of speeding up, the way they steal energy is they increase their frequency.

02:37:43.940 | So they become higher energy photon packets, essentially.

02:37:46.860 | They get blue shifted.

02:37:48.260 | So that you send maybe a red laser beam that comes back blue, it's got more energy in it.

02:37:52.820 | And because photons carry momentum, which is somewhat unintuitive in everyday experience,

02:37:58.180 | but they do, that's how solar sails work, they carry momentum, they push things.

02:38:02.340 | You can even use them as laser tweezers and things to pick things up.

02:38:07.020 | Because they push, it comes back with more momentum than it left.

02:38:11.540 | So you get an acceleration force from this.

02:38:15.080 | And again, you're just stealing energy from the black hole to do this.

02:38:17.940 | So you can get up to the same speed.

02:38:19.780 | It's basically the same idea as Freeman Dyson, but doing it from a safer distance.

02:38:24.240 | And there should be of order of a million or so, or 10 million black holes in the Milky

02:38:28.420 | Way galaxy.

02:38:30.420 | Some of them would be even as close as 10 to 20 light years when you do the occurrence

02:38:35.720 | rate statistics of how close you might expect, feasibly want to be.

02:38:39.100 | They're of course difficult to detect because they're black, and so they're inherently hard

02:38:42.380 | to see.

02:38:43.480 | But statistically there should be plenty out there in the Milky Way.

02:38:45.980 | And so these objects would be natural waypoint stations.

02:38:49.720 | You could use them to both accelerate away and to break and slow down.

02:38:55.700 | - And on top of all this, we've been talking about astronomy and cosmology.

02:39:00.420 | There's been a lot of exciting breakthroughs in detection and exploration of black holes.

02:39:08.460 | So the boomerang photons that you're talking about, there's been a lot of work on photon

02:39:15.260 | rings and just all the fun stuff going on outside the black holes.

02:39:20.800 | So all the garbage outside is actually might be the thing that holds a key to understanding

02:39:27.260 | what's going on inside.

02:39:28.520 | And there's the Hawking radiation, there's all kinds of fascinating stuff.

02:39:31.620 | I mean, there's trippy stuff about black holes that I can't even, well, most people don't

02:39:36.620 | understand.

02:39:37.620 | I mean, the holographic principle with the plate and the information being stored potentially

02:39:43.080 | outside of the black hole, I can't even comprehend how you can project a three-dimensional object

02:39:50.080 | onto 2D and somehow store information where it doesn't destroy it.

02:39:53.840 | And if it does destroy it, challenging all of physics.

02:39:56.840 | All of this is very interesting, especially for kind of more practical applications of

02:40:03.360 | how the black hole can be used for propulsion.

02:40:05.840 | - Yeah, I mean, it may be that black holes are used in all sorts of ways by advanced

02:40:10.840 | civilizations.

02:40:12.400 | I think, again, it's been a popular idea in science fiction or science fiction trope that

02:40:16.960 | Sagittarius A*, the supermassive black hole in the central galaxy, could be the best place

02:40:21.140 | to look for intelligent life in the universe because it is a giant engine in a way.

02:40:27.760 | You know, a unique capability of a black hole is you can basically throw matter into it

02:40:32.680 | and you can get these jets that come out, the accretion disks and the jets that fly

02:40:36.280 | out.

02:40:37.280 | And you can more or less use them to convert matter into energy via E=mc2.

02:40:42.480 | And there's pretty much nothing else except for annihilation with its own antiparticle

02:40:48.080 | as a way of doing that.

02:40:49.960 | So they have some unique properties.

02:40:51.140 | You could perhaps power a civilization by just throwing garbage into a black hole, right?

02:40:56.040 | Just throwing asteroids in and power your civilization with as much energy as you really

02:40:59.640 | would ever plausibly need.

02:41:01.780 | And you could also use them to accelerate away across the universe.

02:41:05.420 | And you can even imagine using small artificial black holes as thermal generators, right?

02:41:09.760 | So the Hawking radiation from them kind of exponentially increases as they get smaller

02:41:14.440 | and smaller in size.

02:41:16.160 | And so a very small black hole, one that you can almost imagine like holding in your hand,

02:41:21.200 | would be a fairly significant heat source.

02:41:24.520 | And so that raises all sorts of prospects about how you might use that in an engineering

02:41:29.660 | context to power your civilization as well.

02:41:34.040 | You have a video on becoming a Kardashev Type I civilization.

02:41:37.480 | What's our hope for doing that?

02:41:39.200 | We're a few orders of magnitude away from that.

02:41:41.520 | Yeah, it is surprising.

02:41:43.240 | I think people tend to think that we're close to this scale.

02:41:47.400 | The Kardashev Type I is defined as a civilization which is using as much energy as is essentially

02:41:53.680 | incident upon the planet from the star.

02:41:56.120 | So as of order, I think, for the Earth of something like 10^5 terawatts or 10^7 terawatts

02:42:01.520 | is a gigantic amount of energy.

02:42:04.120 | And we're using a tiny, tiny, tiny fraction of that right now.

02:42:07.640 | So if you became a Kardashev Type I civilization, which is seen not necessarily as a goal into

02:42:14.280 | itself, I think people think, "Well, why are we aspiring to become this energy-hungry civilization?

02:42:20.560 | Surely our energy needs might improve our efficiency or something as time goes on."

02:42:27.400 | But ultimately, the more energy you have access to, the greater your capabilities will be.

02:42:32.320 | If you want to lift Mount Everest into space, there is just a calculable amount of potential

02:42:38.280 | energy change that that's going to take in order to accomplish that.

02:42:41.720 | And the more energy you have access to as a civilization, then clearly the easier that

02:42:46.200 | energy achievement is going to be.

02:42:48.200 | So it depends on what your aspirations are as a civilization.

02:42:50.240 | It might not be something you want to ever do, but...

02:42:53.560 | - We should make clear that lifting heavy things isn't the only thing.

02:42:57.560 | It's just doing work.

02:42:58.880 | So it could be computation.

02:43:01.520 | It could be more and more and more and more sophisticated and larger and larger and larger

02:43:05.160 | computation, which is, it does seem where we're headed with the very fast increase in

02:43:13.920 | the scale and the quality of our computation outside the human brain, artificial computation.

02:43:19.680 | - Yeah.

02:43:20.800 | - Computation is a great example of, I mean, already I think some 10% of US power electricity

02:43:25.960 | use is going towards the supercomputing centers.

02:43:28.440 | So there's a vast amount of current energy needs which are already going towards computing,

02:43:33.080 | but surely only increase over time.

02:43:36.520 | If we start ever doing anything like mind uploading or creating simulated realities,

02:43:42.800 | that cost will surely become almost a dominant source of our energy requirements at that

02:43:46.600 | point if civilization completely moves over to this kind of post-humanism stage.

02:43:52.360 | And so it's not unreasonable that our energy needs would continue to grow.

02:43:56.680 | Certainly historically, they always have at about 2% per year.

02:44:00.520 | And so if that continues, there is going to be a certain point where you're running up

02:44:05.800 | against the amount of energy which you can harvest, because you're using every, even

02:44:10.000 | if you cover the entire planet in solar panels, there's no more energy to be had.

02:44:15.240 | And so there's a few ways of achieving this.

02:44:17.720 | I sort of talked about in the video how there were several renewable energy sources that

02:44:21.600 | we're excited about, like geothermal, wind power, waves, but pretty much all of those

02:44:27.400 | don't really scratch the surface or don't really scratch the itch of getting to a Kardashev

02:44:30.880 | type one civilization.

02:44:32.240 | That meaningful now, I would never tell anybody don't do wind power now because it's clearly

02:44:37.640 | useful at our current stage of civilization, but it's going to be a pretty negligible fraction

02:44:42.800 | of our energy requirements if we got to that stage of development.

02:44:45.960 | And so there has to be a breakthrough in either our ability to harvest solar energy, which

02:44:50.960 | would require maybe something like a space array of solar panels of beaming the energy

02:44:55.040 | back down, or some developments and innovations in nuclear fusion that would allow us to essentially

02:45:02.720 | reproduce the same process of what's producing the solar photons, but here on Earth.

02:45:08.640 | But even that comes with some consequences.

02:45:10.420 | If you're generating the energy here on Earth and you're doing work on it on Earth, then

02:45:14.220 | that work is going to produce waste heat, and that waste heat is going to increase the

02:45:17.360 | ambient temperature of the planet.

02:45:19.280 | And so even if this isn't really a greenhouse effect that you're increasing the temperature

02:45:24.960 | of the planet, this is just the amount of computers that are churning.

02:45:27.760 | You put your hand to a computer, you can feel the warmth coming off them.

02:45:30.920 | If you do that much work of literally the entire instant energy of the planet is doing

02:45:36.040 | that work, the planet's going to warm up significantly as a result of that.

02:45:41.320 | And so that clearly indicates that this is not a sustainable path.

02:45:47.800 | That civilizations as they approach Kailash-Eve type 1 are going to have to leave planet Earth,

02:45:52.040 | which is really the point of that video, to show that a Kailash-Eve type 1 civilization,

02:45:58.640 | even though it's defined as instant energy upon a planet, that is not a species that

02:46:03.440 | is going to still be living on their planet, at least in isolation.

02:46:07.800 | They will have to be harvesting energy from afar, they will have to be doing work on that

02:46:12.960 | energy outside of their planet, because otherwise you're going to dramatically change the environment

02:46:18.120 | in which you live.

02:46:19.120 | - Well, yeah, so the more energy you create, the more energy you use, the higher the imperative

02:46:26.240 | to expand out into the universe.

02:46:27.800 | But also not just the imperative, but the capabilities.

02:46:31.240 | I mean, you've kind of, as a side on your lab page, mentioned that you're sometimes

02:46:36.920 | interested in astroengineering.

02:46:39.720 | So what kind of space architectures do you think we can build to house humans or interesting

02:46:46.280 | things outside of Earth?

02:46:47.880 | - Yeah, I mean, there's a lot of fun ideas here.

02:46:51.840 | One of the classic ideas is an O'Neill cylinder, or a Stanford torus.

02:46:55.280 | These are like two rotating structures that were devised in space.

02:46:59.680 | They're basically using the centrifugal force as artificial gravity.

02:47:04.800 | And so these are structures which tend to be many kilometers across that you're building

02:47:08.520 | in space, but could potentially habitat millions of people in orbit of the Earth.

02:47:16.680 | Of course, you could imagine putting them, the Expanse does a pretty good job, I think,

02:47:21.240 | of exploring the idea of human exploration of the solar system and having many objects,

02:47:27.160 | many of the small near-Earth objects and asteroids inhabited by mining colonies.

02:47:33.280 | One of the ideas we've played around with our group is this technology called a quasite.

02:47:38.160 | A quasite is an extension, again, we always tend to extend previous ideas, ideas build

02:47:44.840 | upon ideas, but an extension idea called a statite.

02:47:48.440 | A statite was an idea proposed, I think, by Ron Forward in the 1970s.

02:47:52.920 | 1970s seem to have all sorts of wacky ideas.

02:47:55.720 | I don't know what was going on then.

02:47:58.000 | I think the Stanford torus, the O'Neill cylinder, statites, the gravitational lens.

02:48:04.520 | People were really having fun with dreaming about space in the 70s.

02:48:09.160 | The statite is basically a solar sail, but it's such an efficient solar sail that the

02:48:16.120 | outward force of radiation pressure equals the inward force of gravity from the Sun.

02:48:20.640 | And so it doesn't need to orbit.

02:48:22.840 | The Sun is pulling us right now through force of gravity, but we are not getting closer

02:48:29.280 | towards the Sun, even though we are falling towards the Sun because we're in orbit, which

02:48:33.240 | means our translational speed is just enough to keep us at the same altitude, essentially,

02:48:38.080 | from the Sun.

02:48:39.080 | And so you're in orbit, and that's how you maintain distance.

02:48:41.840 | A statite doesn't need to do that.

02:48:43.280 | It could be basically completely static in inertial space, but it's just balancing the

02:48:49.280 | two forces of radiation pressure and inward gravitational pressure.

02:48:53.440 | A quasite is the in-between of those two states.

02:48:56.880 | So it has some significant outward pressure, but not enough to resist fully falling into

02:49:03.280 | the star.

02:49:04.280 | And so it compensates for that by having some translational motion.

02:49:07.640 | So it's in between an orbit and a statite.

02:49:10.960 | And so what that allows you to do is maintain artificial orbits.

02:49:14.880 | So normally, if you want to calculate your orbital speed of something at, say, half an

02:49:19.200 | AU, you would use Kepler's third law and go through that.

02:49:22.080 | And you'd say, "Okay, if it's at half an AU, I can calculate the period by p squared as

02:49:26.120 | proportional to a cubed and go through that."

02:49:28.680 | But for a quasite, you can basically have any speed you want.

02:49:32.840 | It's just a matter of how much of the gravitational force are you balancing out.

02:49:38.240 | You effectively enter an orbit where you're making the mass of the star be less massive

02:49:42.340 | than it really is.

02:49:43.820 | So it's as if you're orbiting a 0.1 solar mass star or a 0.2 solar mass star, whatever

02:49:47.800 | you want.

02:49:48.800 | And so that means that Mercury orbits with a pretty fast orbital speed around the Sun

02:49:56.600 | because it's closer to the Sun than we are.

02:49:59.040 | But we could put something in Mercury's orbit that would have a slower speed, and so it

02:50:03.520 | would co-track with the Earth.

02:50:05.840 | And so we would always be aligned with them at all times.

02:50:09.460 | And so this could be useful if you wanted to have either a chain of colonies or something

02:50:16.800 | that were able to easily communicate and move between one another, between these different

02:50:23.520 | bases.

02:50:24.520 | You'd probably use something like this to maintain that easy transferability.

02:50:30.380 | Or you could even use it as a space weather monitoring system, which was actually proposed

02:50:35.100 | in the paper.

02:50:36.740 | We know that major events like the Carrington event that happened, it can knock out all

02:50:41.340 | of our electromagnetic systems quite easily.

02:50:43.060 | A major solar flare could do that, a geomagnetic storm.

02:50:46.980 | But if we had the ability to detect those higher elevated activity cycles in advance,

02:50:55.780 | the problem is they travel obviously pretty fast, and so it's hard to get ahead of them.

02:50:59.460 | But you could have a station which is basically sampling solar flares very close to the surface

02:51:03.220 | of the Earth, and as soon as it detects anything suspicious, magnetically, it could then send

02:51:08.380 | that information straight back at the speed of light to your Earth and give you maybe

02:51:11.860 | a half an hour warning or something, that something bad was coming.

02:51:16.060 | You should shut off all your systems or get in your Faraday cage now and protect yourself.

02:51:21.980 | And so these quasites are kind of a cool trick of again, kind of hacking the laws of physics.

02:51:27.620 | It's like another one of these exploits that the universe seems to allow us to do, to potentially

02:51:32.940 | manifest these artificial systems that would otherwise be difficult to produce.

02:51:38.220 | LBW So leveraging natural phenomena.

02:51:40.980 | CB Yeah.

02:51:42.940 | That's always the key, is to work, in my mind, is to work with nature.

02:51:47.060 | That's how I see astroengineering, rather than against it.

02:51:49.540 | You're not trying to force it to do something.

02:51:53.380 | That's why I always think solar energy is so powerful, because in the battle against

02:51:57.140 | nuclear fusion, nuclear fusion you're really fighting a battle where you're trying to confine

02:52:00.980 | plasma into this extremely tight space.

02:52:05.900 | The Sun does this for free; it has gravitation.

02:52:08.660 | And so that's in essence what a solar panel does.

02:52:12.780 | It is a nuclear fusion reactor-fuelled energy system, but it's just using gravitation for

02:52:19.540 | the confinement and having a huge standoff distance for its energy collection.

02:52:24.800 | And so there are tricks like that, it's a very naive, simple trick in that case, where

02:52:30.520 | we can, rather than having to reinvent the wheel, we can use the space infrastructure,

02:52:35.520 | if you like, the astrophysical infrastructure that's already there to our benefit.

02:52:38.760 | LBW Yeah, I think in the long arc of human history, probably natural phenomena is the

02:52:44.080 | right solution.

02:52:45.080 | That's the simple, that's the elegant solution, because all the power's already there.

02:52:48.640 | That's why a Dyson sphere in the long, sort of...

02:52:52.240 | Well, you don't know what a Dyson sphere would look like, but some kind of thing that leverages

02:52:57.640 | the power, the energy that's already in the Sun is better than creating artificial nuclear

02:53:03.920 | fusion reaction.

02:53:05.120 | But then again, that brings us to the topic of AI.

02:53:10.000 | How much of this, if we're traveling out there, interstellar travel, or doing some of the

02:53:19.240 | interesting things we've been talking about, how much of those ships would be occupied

02:53:24.360 | by AI systems, do you think?

02:53:31.880 | What would be the living organisms occupying those ships?

02:53:35.800 | CB: Yeah, it's depressing to think about AI in the search for life, because it has...

02:53:43.160 | I mean, I've been thinking about this a lot over the last few weeks with playing around

02:53:46.280 | with Chat GPT-3, like many of us, and being astonished with its capabilities.

02:53:50.760 | And you see that our society is undergoing a change that seems significant in terms of

02:53:59.400 | the development of artificial intelligence.

02:54:00.960 | We've been promised this revolution, this singularity, for a long time, but it really

02:54:06.240 | seems to be stepping up its pace of development at this point.

02:54:12.200 | And so that's interesting, because as someone who looks for alien life out there in the

02:54:18.080 | universe, it sort of implies that our current stage of development is highly transitional.

02:54:25.880 | And that you go back for the last four and a half billion years, the planet was dumb,

02:54:31.840 | essentially.

02:54:32.840 | If you go back the last few thousand years, there was a civilization, but it wasn't really

02:54:36.320 | producing any technosignatures.

02:54:38.360 | And then over the last maybe hundred years, there's been something that might be detectable

02:54:41.680 | from afar.

02:54:43.560 | But we're approaching this cusp where we might imagine it.

02:54:47.360 | I mean, we're thinking of maybe years and decades with AI development, typically when

02:54:52.000 | we talk about this.

02:54:53.440 | But as an astronomer, I have to think about much longer timescales of centuries, millennia,

02:54:58.440 | millions of years.

02:54:59.980 | And so if this wave continues over that timescale, which is still the blink of an eye on a cosmic

02:55:06.720 | timescale, that implies that everything will be AI, essentially, out there if this is a

02:55:12.880 | common behavior.

02:55:14.080 | And so that's intriguing, because it sort of implies that we are special in terms of

02:55:20.160 | our moment in time as a civilization.

02:55:23.320 | Which normally is something we're averse to as astronomers.

02:55:28.280 | We normally like this mediocrity principle.

02:55:30.480 | We're not special, we're a typical part of the universe, similar to the cosmological

02:55:33.880 | principle.

02:55:34.880 | But in a temporal sense, we may be in a unique location.

02:55:40.360 | And perhaps that is part of the solution to the Fermi paradox, in fact.

02:55:44.280 | That if it is true that planets tend to go through basically three phases, dumb life

02:55:50.060 | for the vast majority, a brief period of biological intelligence, and then an extended period

02:55:55.920 | of artificial intelligence that they transition to, then we would be in a unique and special

02:56:02.400 | moment in galactic history that would be of particular interest for any anthropologist

02:56:07.320 | out there in the galaxy.

02:56:09.160 | This would be the time that you would want to study a civilization very carefully.

02:56:14.280 | You wouldn't want to interfere with it, you would just want to see how it plays out.

02:56:18.760 | Kind of similar to the ancestor simulations, though sometimes talked over the simulation

02:56:22.320 | argument, that you are able to observe perhaps your own origins and study how the transformation

02:56:28.880 | happens.

02:56:29.880 | So yeah, that has for me recently been throwing the Fermi paradox a bit on its head.

02:56:33.880 | And this idea of the Zoo hypothesis that we may be monitored, which has for a long time

02:56:38.120 | been sort of seen as a fringe idea, even amongst the SETI community.

02:56:43.320 | But if we live in this truly transitional period, it adds a lot of impetus to that idea,

02:56:50.160 | I think.

02:56:51.160 | - I think even AI itself, by its very nature, would be observing us.

02:56:59.080 | It's like, there used to be this concept of human computation, which is actually exactly

02:57:05.080 | what's feeding the current language models, which is leveraging all the busy stuff we're

02:57:10.760 | doing to do the hard work of learning.

02:57:14.240 | So the language models are trained on human interaction and human language on the internet.

02:57:21.120 | And so AI feeds on the output of brain power from humans.

02:57:30.000 | And so it would be observing and observing, and it gets stronger as it observes.

02:57:35.200 | So it actually gets extremely good at observing humans.

02:57:38.440 | And one of the interesting philosophical questions that starts percolating is, what is the interesting

02:57:45.320 | thing that makes us human?

02:57:48.360 | We tend to think of it, and you said there's three phases.

02:57:52.240 | What's the thing that's hard to come by in phase three?

02:57:56.280 | Is it something like scarcity, which is limited resources?

02:57:59.760 | Is it something like consciousness?

02:58:01.600 | Is that the thing that's very, that emerged the evolutionary process in biological systems

02:58:10.040 | that are operating under constrained resources?

02:58:15.060 | This thing that feels, that it feels like something to experience the world, which we

02:58:19.000 | think of as consciousness, is that really difficult to replicate in artificial systems?

02:58:24.600 | Is that the thing that makes us fundamentally human?

02:58:27.620 | Or is it just a side effect that we attribute way too much importance to?

02:58:32.960 | Do you have a sense?

02:58:37.940 | If we look out into the future and AI systems are the ones that are traveling out there

02:58:42.760 | to Alpha Centauri and beyond, do you think they have to carry the flame of consciousness

02:58:49.080 | with them?

02:58:50.080 | >>JG: No, not necessarily.

02:58:53.520 | They may do, but it may not be necessarily...

02:58:56.840 | I mean, I guess we're talking about the difference here between sort of an AGI, artificial general

02:59:03.000 | intelligence, or consciousness, which are distinct ideas, and you can certainly have

02:59:08.680 | one without the other.

02:59:09.720 | So I could imagine...

02:59:10.720 | I would disagree with it certainly in that statement.

02:59:14.120 | I think it's very possible in order to have intelligence you have to have consciousness.

02:59:18.320 | >>Corey: Okay.

02:59:19.320 | Well, I mean, to a certain degree, GPT-3 has a level of intelligence already.

02:59:24.480 | It's not general intelligence, but it displays properties of intelligence with no consciousness.

02:59:30.520 | >>JG: Again, I would disagree.

02:59:33.320 | >>Corey: Okay, okay.

02:59:35.320 | Well, I don't know.

02:59:37.520 | >>JG: Because you said, it's very nice that you said, "It displays properties of intelligence."

02:59:43.360 | In the same way it displays properties of intelligence, I would say it's starting to

02:59:47.160 | display properties of consciousness.

02:59:49.360 | It certainly could fool you that it's conscious.

02:59:51.360 | >>Corey: Correct, yeah.

02:59:52.360 | So I guess there's like a Turing test problem, like if it's displaying all those properties,

02:59:59.240 | if it quacks like a parrot, looks like a parrot, or quacks like a duck, isn't it basically

03:00:04.040 | a duck at that point?

03:00:05.240 | So yeah, I can see that argument.

03:00:08.280 | It probably, I mean, certainly I try to think about it from the observer's point of view

03:00:15.200 | as an astronomer.

03:00:16.200 | What am I looking for?

03:00:18.280 | Whether that intelligence is conscious or not has little bearing, I think, as to what

03:00:25.640 | I should be looking for when I'm trying to detect evidence of them.

03:00:30.680 | It would maybe affect their behavior in ways that I can't predict.

03:00:38.240 | But that's again getting into the game of what I would call xenopsychology, of trying

03:00:42.040 | to make projections about the motivations of an alien species is incredibly difficult.

03:00:47.800 | And similarly for any kind of artificial intelligence, it's unfathomable what its intentions may

03:00:52.580 | be.

03:00:53.580 | I mean, I would sort of question whether it would even be interested in traveling between

03:00:58.640 | the stars at all if its primary goal is computation, computation for the sake of computation.

03:01:06.080 | Then it's probably going to have a different way of, you know, it's going to be engineering

03:01:11.520 | its solar system and the nearby material around it for a different goal if it's just simply

03:01:16.560 | trying to increase computer substrate across the universe.

03:01:21.080 | And that of course, if that is its principal intention, to just essentially convert dumb

03:01:25.240 | matter into smart matter as it goes, then I think that would come into conflict with

03:01:31.040 | our observations of the universe, right?

03:01:32.880 | Because the Earth shouldn't be here if that were true.

03:01:36.920 | The Earth should have been transformed into computer substrate by this point.

03:01:40.240 | There has been plenty of time in the history of the galaxy for that to have happened.

03:01:45.920 | So I'm skeptical that we can...I'm skeptical in the part that that's a behavior that AI

03:01:54.720 | or any civilization really engages in, but I also find it difficult to find a way out

03:01:59.200 | of it.

03:02:01.200 | To explain why that would never happen in the entire history of the galaxy amongst potentially

03:02:05.680 | if life is common, millions, maybe even billions of instant instantiations of AI could have

03:02:11.360 | occurred across the galaxy.

03:02:14.160 | And so that seems to be a knock against the idea that there is life else or intelligent

03:02:20.480 | life elsewhere in the galaxy.

03:02:22.880 | The fact that that hasn't occurred in our history is maybe the only solid data point

03:02:28.520 | we really have about the activities of other civilizations.

03:02:32.480 | LB: Of course, the scary one could be that we just at this stage, intelligent alien civilizations

03:02:40.040 | just start destroying themselves.

03:02:43.040 | It becomes too powerful.

03:02:44.640 | Everything's just too many weapons, too many nuclear weapons, too many nuclear weapon style

03:02:48.840 | systems that just from mistake to aggression to like the probability of self-destruction

03:02:56.200 | is too high relative to the challenge of avoiding the technological challenges of avoiding self-destruction.

03:03:03.120 | LB: You mean the AI destroys itself or we destroy ourselves prior to the advent of AI?

03:03:11.080 | As we get smarter and smarter, AI, either AI destroys us or other, there could be just

03:03:17.240 | a million.

03:03:18.240 | Like AI is correlated, the development of AI is correlated with all this other technological

03:03:22.240 | innovation.

03:03:23.240 | Genetic engineering, all kinds of engineering at the nano scale, mass manufacture of things

03:03:32.560 | that could destroy us or cracking physics enough to have very powerful weapons, nuclear

03:03:38.560 | weapons, all of it.

03:03:40.320 | Just too much physics enables way too many things that can destroy us before it enables

03:03:49.000 | the propulsion systems that allow us to fly far enough away before we destroy ourselves.

03:03:56.320 | So maybe that's what happens to the other alien civilizations.

03:03:58.640 | Is that your resolution?

03:03:59.640 | Because I mean, I think us in the technosignature community and astronomy community aren't thinking

03:04:04.680 | about this problem seriously enough, in my opinion.

03:04:07.560 | We should be thinking about what AI is doing to our society and the implications of what

03:04:13.640 | we're looking for.

03:04:14.920 | And so the only, I think, part of this thinking has to involve people like yourself who are

03:04:20.560 | more intimate with the machine learning and artificial intelligence world.

03:04:24.880 | How do you reconcile in your mind, you said earlier that you think you can't imagine a

03:04:30.000 | galaxy where life and intelligence is not all over the place.

03:04:35.000 | And if artificial intelligence is a natural progression for civilizations, how do you

03:04:39.760 | reconcile that with the absence of any information around us?

03:04:44.560 | So any clues or hints of artificial behavior, artificially engineered stars, or colonization,

03:04:51.520 | computer substrate transform planets, anything like that?

03:04:54.560 | It's extremely difficult for me.

03:04:58.200 | The Fermi paradox broadly defined is extremely difficult for me.

03:05:02.040 | And the terrifying thing is one thing I suspect is that we keep destroying ourselves.

03:05:07.640 | The probability of self-destruction with advanced technology is just extremely high.

03:05:12.760 | That's why we're not seeing it.

03:05:15.620 | But then again, my intuition about why we haven't blown ourselves up with nuclear weapons,

03:05:22.360 | it's very surprising to me from a scientific perspective.

03:05:26.560 | Given all the cruelty I've seen in the world, given the power that nuclear weapons place

03:05:34.000 | in the hands of a very small number of individuals, it's very surprising to me we destroy ourselves.

03:05:39.200 | And it seems to be a very low probability situation we have happening here.

03:05:45.960 | And then the other explanation is the zoo, is the observation that we're just being observed.

03:05:52.200 | That's the only other thing.

03:05:53.360 | It's just so difficult for me.

03:05:57.280 | Of course, all of science, everything is very humbling.

03:06:00.000 | It would be very humbling for me to learn that we're alone in the universe.

03:06:06.080 | It would change.

03:06:08.760 | You know what?

03:06:10.320 | Maybe I do want that to be true 'cause you want us to be special.

03:06:13.280 | That's why I'm resisting that thought maybe.

03:06:15.720 | There's no way we're that special.

03:06:17.840 | There's no way we're that special.

03:06:19.800 | That's where my resistance comes from.

03:06:21.400 | I would just say the specialness is something...

03:06:26.240 | Implicitly in that statement, there's kind of an assumption that we are something positive.

03:06:31.880 | We're a gift to this planet or something, and that makes us special.

03:06:34.640 | But it may be that intelligence is more of a...

03:06:39.000 | We're like rats or cockroaches.

03:06:40.600 | We're an infestation of this planet.

03:06:43.080 | We're not some benevolent property that a planet would ideally like to have, if you

03:06:49.520 | can even say such a thing.

03:06:50.840 | But we may be not only generally a negative force for a planet's biosphere and its own

03:06:57.280 | survivability, which I think you can make a strong argument about, but we may also be

03:07:01.880 | a very persistent infestation that may...

03:07:05.400 | Even in...

03:07:06.400 | Interesting thoughts.

03:07:07.400 | In the wake of a nuclear war, would that be an absolute eradication of every human being,

03:07:13.320 | which would be a fairly extreme event?

03:07:16.280 | Or would the Candela consciousness, as you might call it, the flame of consciousness,

03:07:20.440 | only with some small pockets, that would maybe in 10,000 years, 100,000 years, we'd see civilization

03:07:27.080 | re-emerge and play out the same thing over again?

03:07:30.120 | Yeah, certainly.

03:07:31.120 | But nuclear weapons aren't powerful enough yet.

03:07:33.920 | But yes, to sort of push back on the infestation, sure.

03:07:38.840 | But the word 'special' doesn't have to be positive.

03:07:42.560 | I just mean...

03:07:43.560 | I think it tends to imply...

03:07:45.160 | I take your point, yeah.

03:07:46.440 | That maybe... just maybe extremely rare might be.

03:07:50.760 | Yeah, and that to me, it's very strange for me to be cosmically unique.

03:08:00.760 | It's just very strange.

03:08:03.680 | I mean, that we're the only thing of this level of complexity in the galaxy just seems

03:08:11.600 | very strange to me.

03:08:13.640 | I would just... yeah, I do think it depends on this classification.

03:08:18.080 | I think there is sort of, again, it's kind of buried within there as a subtext, but there

03:08:22.160 | is a classification that we're doing here that what we are is a distinct category of

03:08:29.160 | life, let's say in this case.

03:08:30.680 | When we're talking about intelligence, we are something that can be separated.

03:08:35.040 | But of course, we see intelligence across the animal kingdom in dolphins, humpback whales,

03:08:41.400 | octopuses, crows, ravens.

03:08:43.760 | And so it's quite possible that these are all manifestations of the same thing.

03:08:51.320 | And we are not a particularly distinct class, except for the fact we make technology.

03:08:57.680 | That's really the only difference to our intelligence.

03:08:59.800 | And we classify that separately, but from a biological perspective, to some degree,

03:09:05.040 | it's really just all part of a continuum.

03:09:07.020 | And so that's why when we talk about unique, you are putting yourself in a box which is

03:09:13.140 | distinct and saying, "This is the only example of things that fall into this box."

03:09:17.300 | But the walls of that box may themselves be a construct of our own arrogance that we are

03:09:23.820 | something distinct.

03:09:27.100 | - But I was also speaking broadly for us, meaning all life on Earth.

03:09:33.740 | But then it's possible that there's all kinds of living ecosystems on other planets and

03:09:41.020 | other moons that just don't have interest in technological development.

03:09:47.460 | Maybe technological development is the parasitic thing that destroys the organism broadly.

03:09:53.660 | And then maybe that's actually one of the fundamental realities.

03:09:59.280 | Whatever broad way to categorize technological development, that's just the parasitic thing

03:10:04.000 | that just destroys itself.

03:10:05.000 | It's a cancer.

03:10:06.000 | - We're floating around, sorry to interrupt, but we're floating around this idea of the

03:10:09.600 | great filter a little bit here.

03:10:11.400 | So we're asking, "Does it lie ahead of us?"

03:10:15.120 | Nuclear war may be imminent, that would be a filter that's ahead of us.

03:10:18.280 | Or could it be behind us, and it's the advent of technology that is genuinely a rare occurrence

03:10:23.720 | in the universe, and that explains the Fermi paradox.

03:10:28.120 | And so that's something that obviously people have debated and argued about in SETI for

03:10:33.960 | decades and decades, but it remains a persistent--people argue whether it should be really called a

03:10:40.520 | paradox or not--but it remains a consistent apparent contradiction that you can make a

03:10:46.080 | very cogent argument as to why you expect life and intelligence to be common in the

03:10:50.000 | universe, and yet everything, everything we know about the universe is fully compatible

03:10:56.480 | with just us being here.

03:10:58.920 | And that's a haunting thought, but I have no preference or desire for that to be true.

03:11:07.400 | I'm not trying to impose that view on anyone, but I do ask that we remain open-minded until

03:11:14.120 | evidence has been collected either way.

03:11:16.440 | - The thing is, it's one of, if not the, probably I would argue it's the most important question

03:11:23.520 | facing human civilization, or the most interesting, I think, scientifically speaking.

03:11:29.920 | What question is more important than--somehow, there could be other ways to sneak up to it,

03:11:39.120 | but it gets to the essence of what we are, what these living organisms are.

03:11:45.920 | It's somehow seeing another kind helps us understand--

03:11:50.160 | - It speaks to the human condition, helps us understand what it is to be human to some

03:11:54.560 | degree.

03:11:57.200 | I think, you know, I have tried to remain very agnostic about the idea of life and intelligence.

03:12:03.640 | One thing I try to be more optimistic about, and I've been thinking a lot with our searches

03:12:09.080 | for life in the universe, is life in the past.

03:12:13.400 | I think it's actually not that hard to imagine we are the only civilization in the galaxy

03:12:17.240 | right now.

03:12:18.240 | - Living.

03:12:19.240 | - Living to this current extent.

03:12:21.080 | But there may be very many extinct civilizations.

03:12:24.080 | If each civilization has a typical lifetime comparable to, let's say, AI is the demise

03:12:28.160 | of our own, that's only a few hundred years of technological development, or maybe 10,000

03:12:32.360 | years if you go back to the Neolithic Revolution, the dawn of agriculture.

03:12:37.640 | Hardly anything in cosmic time span.

03:12:40.760 | That's nothing, that's the blink of an eye.

03:12:42.800 | And so it's not surprising at all that we would happen not to coexist with anyone else.

03:12:47.840 | But that doesn't mean nobody else was ever here.

03:12:51.400 | And if other civilizations come to that same conclusion and realization, maybe they scour

03:12:57.120 | the galaxy around them, don't find any evidence for intelligence, then they have two options.

03:13:02.080 | They can either give up on communication and just say, "Well, it's never going to happen.

03:13:06.560 | We just may as well just worry about what's happening here on our own planet."

03:13:11.160 | Or they could attempt communication, but communication through time.

03:13:15.160 | And that's almost the most selfless act of communication, because there's no hope of

03:13:22.320 | getting anything back.

03:13:24.040 | It's a philanthropic gift almost to that other civilization that maybe might just be nothing

03:13:30.360 | more than a monument, which the pyramids essentially are, a monument of their existence.

03:13:34.560 | That these are the things they achieved, the things they believed in, their language, their

03:13:41.160 | culture.

03:13:42.160 | It could be maybe something more than that.

03:13:45.000 | It could be lessons from what they learned in their own history.

03:13:47.920 | And so I've been thinking a lot recently about how would we send a message to other civilizations

03:13:57.360 | in the future?

03:13:59.240 | Because that act of thinking seriously about the engineering of how you would design it

03:14:04.080 | would inform us about what we should be looking for, and also perhaps be our best chance,

03:14:11.000 | quite frankly, of ever making contact.

03:14:13.560 | It may not be the contact we dream of, but it's still contact.

03:14:17.400 | There would still be a record of our existence, as pitiful as it might be compared to a two-way

03:14:23.320 | communication.

03:14:24.320 | - And I love the humility behind that project, the Universal Project.

03:14:30.640 | It's humble, and it humbles you to the vast temporal landscape of the universe.

03:14:42.720 | Just realizing our day-to-day lives, all of us will be forgotten.

03:14:47.380 | It's nice to think about something that sends a signal out to other, yeah.

03:14:52.800 | - It was almost like a humility of acceptance as well, of knowing that you have a terminal

03:14:59.120 | disease, but your impact on the Earth doesn't have to end with your death.

03:15:04.480 | It could go on beyond with what you leave behind for others to discover, with maybe

03:15:09.720 | the books you write or what you leave in the literature.

03:15:12.600 | - Do you think launching the Roadster vehicle out in space would have done panic?

03:15:18.160 | - Yeah, the Roadster.

03:15:19.160 | I'm not sure what someone would make of that if they found it.

03:15:23.160 | - Yeah, that's true.

03:15:24.160 | - I mean, there have been quasi-attempts at it beyond the Roadster.

03:15:28.000 | I mean, there's the Pioneer plaques, there's the Voyager 2 Golden Record.

03:15:35.120 | It's pretty unlikely anybody's going to discover those, because they're just adrift in space

03:15:40.240 | and they will eventually mechanically die and not produce any signal for anyone to spot.

03:15:45.320 | So you'd have to be extremely lucky to come across them.

03:15:48.040 | I've often said to my colleagues that I think the best place is the Moon.

03:15:51.800 | The Moon, unlike the Earth, has no significant weathering.

03:15:57.120 | How long will the Apollo descent stages, which are still still on the lunar surface, last

03:16:02.200 | for?

03:16:03.200 | The only real effect is micrometeorites, which are slowly like dust smashing against them

03:16:09.400 | pretty much.

03:16:10.400 | But that's going to take millions, potentially billions of years to erode that down.

03:16:16.080 | And so we have an opportunity, and that's on the surface.

03:16:18.600 | If you put something just a few meters beneath the surface, it would have even greater protection.

03:16:23.240 | And so it raises the prospect of that if we wanted to send something, a significant amount

03:16:28.760 | of information, to a future galactic-spanning civilization that maybe cracks the interstellar

03:16:33.560 | propulsion problem, the Moon's going to be there for five billion years.

03:16:38.520 | That's a long time for somebody to come by and detect maybe a strange pattern that we

03:16:44.560 | draw on the sand for them to, you know, big arrow, big cross, like, look under here.

03:16:50.240 | And we could have a tomb of knowledge of some record of our civilization.

03:16:54.440 | And so I think when you think like that, what that implies to us, well, OK, the galaxy's

03:17:00.840 | 13 billion years old, the Moon is already four billion years old.

03:17:04.320 | There may be places familiar to us, nearby to us, that we should be seriously considering

03:17:10.920 | as places we should look for life, and intelligent life, or evidence of relics that they might

03:17:15.960 | leave behind for us.

03:17:17.340 | - So thinking like that will help us find such relics, and it's like a beneficial cycle

03:17:25.040 | that happens.

03:17:26.040 | - Yes, yeah, exactly.

03:17:27.040 | - That enables the science of society better, like, of searching for bios and tech signatures

03:17:32.120 | and so on.

03:17:33.120 | - Yeah.

03:17:34.120 | - And it's inspiring.

03:17:35.720 | It's also inspiring in that we want to leave a legacy behind as an entire civilization,

03:17:44.520 | not just in the symbols, but broadly speaking.

03:17:47.560 | That's the last thing somehow.

03:17:48.800 | - Yeah, and I'm part of a team that's trying to repeat the Golden Record experiment.

03:17:56.320 | We're trying to create like an open source version of the Golden Record that future spacecraft

03:18:00.000 | are able to download, and basically put on a little hard drive that they can carry around

03:18:04.120 | with them, and get these distributed, hopefully, across the solar system eventually.

03:18:08.520 | - So it's gonna be called the Hitchhiker's Guide to the Galaxy, or?

03:18:12.080 | - It could be, that's a good name for it.

03:18:14.920 | We've been toying a little bit with the name, but I think it'll probably just be Golden

03:18:17.040 | Record at this point, or Golden Record version two or something.

03:18:19.560 | But I think another benefit that I see of this activity is that it forces us as a species

03:18:29.760 | to ask those questions about what it is that we want another civilization to know about

03:18:34.720 | us.

03:18:35.720 | The Golden Record was kind of funny because it had photos on it, and it had photos of

03:18:40.160 | people eating, for instance, but it had no photos of people defecating.

03:18:45.720 | And so I always thought that was kind of funny, because if I was an alien, or if I was studying

03:18:51.080 | an alien, if I saw images of an alien, I would, I'm not trying to be like a perv or anything,

03:18:56.040 | but I would want to see the full, I want to understand the biology of that alien.

03:18:59.640 | And so we always censor what we show, and--

03:19:05.240 | - We should show the whole actual natural process, and then also say, we humans tend

03:19:10.480 | to censor these things.

03:19:12.160 | We tend to not like to walk around naked, we tend to not to talk about some of the natural

03:19:18.040 | biological phenomena, and talk a lot about others, and actually just be very, like the

03:19:24.040 | way you would be to a therapist or something, very transparent about the way we actually

03:19:27.280 | operate in this world.

03:19:28.280 | - I mean, and Sagan had that with the Golden Record.

03:19:30.840 | I think he originally, there's a male and a female figure to pitch on the Golden Record,

03:19:37.120 | and the woman had a genitalia originally drawn, and there was a lot of pushback from, I think,

03:19:43.840 | a lot of Christian groups who were not happy about the idea of throwing this into space.

03:19:48.900 | And so eventually they had to remove that.

03:19:51.760 | And so it would be confusing biologically, if you're trying to study xenobiology of this

03:19:57.640 | alien that apparently has no genitalia, or the man does, but for some reason the woman

03:20:03.000 | doesn't.

03:20:04.000 | And that's our own societal and cultural imprint happening into that information.

03:20:11.560 | - To be fair, just even having two sexes, and predators and prey, just the whole, that

03:20:19.000 | could be just a very unique Earth-like thing, so they might be confused about why there's

03:20:22.800 | like pairs of things.

03:20:24.080 | Like why is there a man and a woman in general?

03:20:29.440 | Like they could be confused about a lot of things in general.

03:20:33.640 | - They don't even know which way to hold the picture.

03:20:38.280 | - Or there's the picture, they might have very different sensory devices to even interpret

03:20:43.280 | this.

03:20:44.280 | - Correct, yeah, if they only have sound as their only way of navigating the world, it's

03:20:48.000 | kind of lost.

03:20:49.000 | There's been a lot of conversation about sending video and pictures, and that's one of the

03:20:56.840 | things I've been a little bit resistant about in the team, that I've been thinking, well,

03:21:02.280 | they might not have eyes.

03:21:03.280 | And so if you lived on the Europa surface, having eyes wouldn't be very useful.

03:21:09.840 | If you lived on a very dark planet on the tidally locked night side of an exoplanet,

03:21:14.520 | having eyes wouldn't be particularly useful.

03:21:16.440 | So it's kind of a presumption of us to think that video is a useful form of communication.

03:21:22.200 | - Do you hope we become a multi-planetary species?

03:21:24.800 | So we're almost sneaking up to that, but the efforts of SpaceX, of Elon, maybe in general

03:21:30.880 | what your thoughts are about those efforts?

03:21:32.920 | So you already mentioned Starship will be very interesting for astronomy, for science

03:21:37.080 | in general, just getting stuff out into space.

03:21:40.960 | But what about the longer term goal of actually colonizing, of building civilizations on other

03:21:46.080 | surfaces, on moons, on planets?

03:21:49.120 | - It seems like a fairly obvious thing to do for our survival, right?

03:21:52.880 | There's a high risk if we are committed to trying to keep this human experiment going,

03:22:01.680 | putting all of our eggs in one basket is always going to be a risky strategy to pursue.

03:22:06.640 | - It's a nice basket though.

03:22:08.040 | - It is a beautiful basket.

03:22:09.600 | I wouldn't want to, I personally have no interest in living on Mars or the Moon.

03:22:13.560 | I would like to visit, but I would definitely not want to spend the rest of my life and

03:22:17.920 | die on Mars.

03:22:18.920 | I mean, it's a hellhole.

03:22:21.640 | Mars is a very, very difficult- I think the idea that this is going to happen in the next

03:22:26.160 | 10, 20 years seems to me very optimistic.

03:22:31.160 | Not that it's insurmountable, but the challenges are extreme to survive on a planet like Mars,

03:22:38.160 | which is like a dry, frozen desert with a high radiation environment.

03:22:45.080 | It's a challenge of a type we've never faced before.

03:22:48.480 | I'm sure human ingenuity can tackle it, but I'm skeptical that we'll have thousands of

03:22:53.640 | people living on Mars in my lifetime.

03:22:56.320 | But I would relish that opportunity to maybe one day visit such a settlement and do scientific

03:23:06.400 | experiments on Mars, or experience Mars, do astronomy from Mars, all sorts of cool stuff

03:23:10.880 | you could do.

03:23:13.200 | Sometimes you see these dreams of outer solar system exploration, and you can fly through

03:23:17.840 | the clouds of Venus, or you could just do these enormous jumps on these small moons

03:23:23.880 | where you can essentially jump as high as a skyscraper and traverse the Moon.

03:23:27.760 | So there's all sorts of wonderful ice skating on Europa might be fun.

03:23:31.600 | So don't get me wrong, I love the idea of us becoming interplanetary.

03:23:34.840 | I think it's just a question of time.

03:23:40.760 | Our own destructive tendencies, as you said earlier, are at odds with our emerging capability

03:23:49.400 | to become interplanetary.

03:23:51.280 | And the question is, will we get out of the nest before we burn it down?

03:23:55.480 | And I don't know.

03:23:56.480 | Obviously, I hope that we do, but I don't have any special insight.

03:24:02.880 | There is somewhat of an annoying intellectual itch I have with the so-called doomsday argument,

03:24:10.160 | which I try not to treat too seriously, but there is some element of it that bothers me.

03:24:16.680 | The doomsday argument basically suggests that you're typically the mediocrity principle

03:24:22.800 | - you're not special - that you're probably going to be born somewhere in the middle of

03:24:25.880 | all human beings who will ever be born.

03:24:28.160 | You're unlikely to be one of the first 1% of human beings that ever lived, and one of

03:24:32.160 | the last 1% - and similarly the last 1% of human beings that will ever live.

03:24:35.640 | Because you'd be very unique and special if that were true.

03:24:39.120 | And so by this logic, you can sort of calculate how many generations of humans you might expect.

03:24:44.280 | So if there's been, let's say, 100 billion human beings that have ever lived on this

03:24:48.000 | planet, then you could say to 95% confidence - so you divide by 5% - so 100 billion divided

03:24:55.560 | by 0.05 would give you 2 trillion human beings that would ever live, you'd expect by this

03:25:00.520 | argument.

03:25:01.520 | And so if each planet - in general the planet has a 10 billion population - so that would

03:25:10.000 | be 200 generations of humans we would expect ahead of us.

03:25:15.220 | And if each one has an average lifetime of say 100 years, then that would be about 20,000

03:25:19.400 | years.

03:25:20.400 | So there's 20,000 years left on the clock.

03:25:21.880 | That's like a typical doomsday argument type - that's how they typically lay it out.

03:25:28.520 | Now a lot of the criticisms of the doomsday argument come down to, well what are you really

03:25:33.880 | counting?

03:25:34.880 | You're counting humans there, but maybe you should be counting years.

03:25:37.720 | Or maybe you should be counting human hours.

03:25:41.080 | Because what you count makes a big difference to what you get out on the other end.

03:25:43.800 | So this is called the reference class.

03:25:46.120 | And so that's one of the big criticisms of the doomsday argument.

03:25:48.880 | But I do think it has a compelling point that it would be surprising if our future is to

03:25:54.480 | one day blossom and become a galactic spanning empire.

03:25:59.760 | Trillions upon trillions upon trillions of human beings will one day live across the

03:26:03.640 | stars for essentially as long as the galaxy exists and the stars burn.

03:26:09.440 | We would live at an incredibly special point in that story.

03:26:13.240 | We would be right at the very, very, very beginning.

03:26:17.120 | And that's not impossible, but it's just somewhat improbable.

03:26:21.100 | And so part of that sort of irks against me, but it also almost feels like a philosophical

03:26:26.840 | argument because you're sort of talking about souls being drawn from this cosmic pool.

03:26:33.900 | So it's not an argument that I lose sleep about for our fate of the doomsday, but it

03:26:38.940 | is somewhat intellectually annoying that there is a slight contradiction now it feels like

03:26:47.620 | with the idea of a galactic spanning empire.

03:26:52.020 | - But of course there's so many unknowns.

03:26:55.700 | I for one would love to visit even space, but Mars, just imagine standing on Mars and

03:27:01.700 | looking back at Earth.

03:27:04.100 | - Yeah.

03:27:05.540 | - I mean.

03:27:06.540 | - It'd be incredible sight.

03:27:09.100 | It would give you such a fresh perspective as to your entire existence and why you're

03:27:14.180 | meant to be human.

03:27:15.500 | And then come back to Earth, it would give you a heck of a perspective.

03:27:20.660 | Plus the sunset on Mars is supposed to be nice.

03:27:23.180 | - I loved what William Shatner said after his flight.

03:27:27.100 | His words really moved me when he came down.

03:27:29.520 | And I think it really captured the idea that we shouldn't really be sending engineers,

03:27:36.420 | our scientists into space.

03:27:37.860 | We should be sending our poets because those are the people when they come down who can

03:27:43.620 | truly make a difference when they describe their experiences in space.

03:27:47.460 | And I found it very moving reading what he said.

03:27:50.700 | - Yeah, when you talk to astronauts, when they describe what they see, it's like this,

03:27:58.260 | like they discovered a whole new thing that they can't possibly convert back into words.

03:28:02.100 | - Yeah.

03:28:03.100 | - Yeah, it's beautiful to see.

03:28:04.940 | Just as a quick, before I forget, I have to ask you, can you summarize your argument against

03:28:10.300 | the hypothesis that we live in a simulation?

03:28:13.720 | Is it similar to our discussion about the Doomsday Clock?

03:28:17.700 | - No, it's actually pretty more similar to my agnosticism about life in the universe.

03:28:24.260 | And it's just sort of remaining agnostic about all possibilities.

03:28:28.740 | The simulation argument, sometimes it gets mixed.

03:28:34.020 | There's kind of two distinct things that we need to consider.

03:28:37.780 | One is the probability that we live in so-called base reality, that we're not living in a simulated

03:28:42.740 | reality itself.

03:28:43.740 | And another probability we need to consider is the probability that that technology is

03:28:48.420 | viable, possible, and something we will ultimately choose to one day do.

03:28:53.020 | Those are two distinct things.

03:28:54.380 | They're probably quite similar numbers to each other, but they are distinct probabilities.

03:28:59.100 | So in my paper I wrote about this, I just tried to work through the problem.

03:29:04.460 | I teach astrostatistics, actually teach me this morning.

03:29:06.900 | And so it just seemed like a fun case study of working through a Bayesian calculation

03:29:11.620 | for it.

03:29:12.620 | Bayesian calculations work on conditionals.

03:29:15.420 | And so when you hear, what kind of inspired this project was when I heard Musk said, "There's

03:29:19.700 | like a billion to one chance that we don't live in a simulation."

03:29:25.300 | He's right if you add the Bayesian conditional, and the Bayesian conditional is conditioned

03:29:30.920 | upon the fact that we eventually develop that technology and choose to use it.

03:29:34.780 | Or it's chosen to be used by such species, by such civilizations.

03:29:39.660 | That's the conditional.

03:29:40.940 | And you have to add that in because that conditional isn't guaranteed.

03:29:44.780 | And so in a Bayesian framework you can kind of make that explicit.

03:29:49.140 | You see mathematically, explicitly that's a conditional in your equation.

03:29:53.380 | And the opposite side of the coin is basically in the trilemma that Bostrom originally put

03:29:58.060 | forward is options one and two.

03:30:00.340 | Option one is that you basically never develop the ability to do that.

03:30:04.140 | Option two is you never choose to execute that.

03:30:07.260 | So we kind of group those together as sort of the non-simulation scenario, let's call

03:30:14.060 | it.

03:30:15.060 | So you've got non-simulation scenario and simulation scenario.

03:30:17.860 | And agnostically we really have to give the, you know, how do you assess the model, the

03:30:23.660 | a priori model probability of those two scenarios?

03:30:27.940 | It's very difficult and we can, I think people would probably argue about how you assign

03:30:32.100 | those priors.

03:30:33.260 | In the paper we just assigned 50/50.

03:30:34.740 | We just said this hasn't been demonstrated yet.

03:30:37.900 | There's no evidence that this is actually technically possible, but nor is it that it's

03:30:43.260 | not technically possible.

03:30:44.500 | So we're just going to assign 50/50 probability to these two hypotheses.

03:30:47.940 | And then in the hypothesis where you have a simulated reality, you have a base reality

03:30:51.540 | sat at the top.

03:30:52.820 | So there is, even in the simulated hypothesis, there's a probability you still live in base

03:30:56.380 | reality and then there's a whole myriad of universes beneath that which are all simulated.

03:31:02.220 | And so you have a very slim probability of being in base reality if this is true.

03:31:07.260 | And you have a hundred percent probability of living in base reality on the other hand

03:31:11.380 | if it's not true and we never develop that ability or choose never to use it.

03:31:16.720 | And so then you apply this technique called Bayesian model averaging, which is where you

03:31:20.200 | propagate the uncertainty of your two models to get a final estimate.

03:31:23.980 | And because of that one base reality that lives in the simulated scenario, you end up

03:31:29.340 | counting this up and getting that it always has to be less than 50%.

03:31:32.980 | So the probability you live in a simulated reality versus a base reality has to be slightly

03:31:36.980 | less than 50%.

03:31:39.340 | Now that really comes down to that statement of giving it 50/50 odds to begin with.

03:31:44.980 | And on the one hand you might say, "Look David, I work in artificial intelligence, I'm very

03:31:49.260 | confident that this is going to happen, just of extrapolating of current trends."

03:31:53.900 | On the other hand, a statistician would say, "You're giving way too much weight to the

03:31:59.900 | simulation hypothesis because it's an intrinsically highly complicated model.

03:32:03.960 | You have a whole hierarchy of realities within realities within realities.

03:32:08.580 | It's like the Inception-style thing, right?"

03:32:11.080 | And so this requires hundreds, thousands, millions of parameterizations to describe.

03:32:16.520 | And by Occam's razor, we would always normally penalize inherently complicated models as

03:32:20.560 | being disfavoured.

03:32:22.160 | So I think you could argue I'm being too generous or too kind with that, but I sort of want

03:32:27.440 | to develop the rigorous mathematical tools to explore it.

03:32:31.680 | And ultimately it's up to you to decide what you think that 50/50 odds should be.

03:32:35.800 | But you can use my formula to plug in whatever you want and get the answer.

03:32:40.020 | And I use 50/50.

03:32:41.020 | - So, and, but when in that first pile, with the first two parts of the, the, the, the

03:32:48.040 | Boston talks about, it seems like connected to that is the question we've been talking

03:32:53.240 | about, which is the number of times at bat you get, which is the number of intelligent

03:32:57.960 | civilizations that are out there that can build such simulations.

03:33:02.800 | That's it seems like very closely connected.

03:33:05.680 | Because if we're the only ones that are here and it could build such things that changes

03:33:10.480 | things.

03:33:11.480 | - Yeah, yeah.

03:33:12.480 | I mean, yeah, the simulation hypothesis has all sorts of implications like that.

03:33:17.960 | I've always loved, Sean Carroll points out a really interesting contradiction apparently

03:33:21.760 | with the simulation hypothesis that I speak about a little bit in the paper.

03:33:26.000 | But he showed that, or pointed out that in this hierarchy of realities, which then develop

03:33:32.120 | their own AIs within the realities, and then they, or really ancestor simulations, I should

03:33:37.200 | say rather than AI, they develop their own capability to simulate realities.

03:33:40.680 | You get this hierarchy.

03:33:41.680 | And so eventually there'll be a bottom layer, which I often call the sewer of reality.

03:33:46.760 | It's like the worst layer where it's the most pixelated it could possibly be, right?

03:33:51.400 | Because each layer is necessarily going to have less computational power than the layer

03:33:54.640 | above it.

03:33:55.640 | Because not only are you simulating that entire planet, but also some of that's being used

03:33:59.000 | for the computers themselves, that those are simulated.

03:34:02.140 | And so that base reality, or sorry, the sewer of reality is a reality where they are simply

03:34:08.480 | unable to produce ancestor simulations because the fidelity of the simulation is not sufficient.

03:34:15.000 | And so from their point of view, it might not be obvious that the universe is pixelated,

03:34:17.680 | but they would just never be able to manifest that capability.

03:34:20.380 | - What if they're constantly simulating, 'cause in order to appreciate the limits of the fidelity,

03:34:28.440 | you have to have an observer.

03:34:29.960 | What if they're always simulating a dumber and dumber observer?

03:34:34.100 | What if the sewer has very dumb observers that can't, like scientists that are the dumbest

03:34:39.700 | possible scientists.

03:34:41.200 | So like it's very pixelated, but the scientists are too dumb to even see the pixelations.

03:34:47.760 | That's like built into the universe always has to be a limitation on the cognitive capabilities

03:34:53.280 | of the complex systems that are within it.

03:34:55.440 | - Yeah, so that sewer of reality, they would still presumably be able to have a very impressive

03:35:02.000 | computational capabilities.

03:35:03.000 | They'd probably be able to simulate galactic formation or this kind of impressive stuff,

03:35:07.040 | but they would be just short of the ability to, however you define it, create a truly

03:35:12.080 | sentient conscious experience in a computer.

03:35:15.080 | That would just be just beyond their capabilities.

03:35:18.580 | And so Carol pointed out that if you add up all the, you know, you count up how many realities

03:35:22.860 | there should be, probabilistically, if this is true, over here, the simulation hypothesis

03:35:29.560 | or scenario, then you're most likely to find yourself in the sewer, because there's just

03:35:34.000 | far more of them than there are of any of the higher levels.

03:35:38.960 | And so that sort of sets up a contradiction, because then you live in a reality which is

03:35:44.640 | inherently incapable of ever producing ancestor simulations.

03:35:50.000 | But the premise of the entire argument is that ancestor simulations are possible.

03:35:55.440 | So there's a contradiction that's been introduced.

03:35:58.200 | - There's that old quote, "We're all living in the sewer, but some of us are looking up

03:36:01.960 | at the stars."

03:36:02.960 | (laughing)

03:36:04.640 | This is maybe more true than we think.

03:36:08.040 | - To me, so there's of course physics and computational fascinating questions here,

03:36:11.800 | but to me, there's a practical psychological question, which is, you know, how do you create

03:36:18.480 | a virtual reality world that is as compelling, and not necessarily even as realistic, but

03:36:28.000 | almost as realistic, but as compelling or more compelling than physical reality?

03:36:33.960 | Because something tells me it's not very difficult, in the full history of human civilization.

03:36:44.120 | That is an interesting kind of simulation to me, because that feels like it's doable

03:36:49.920 | in the next hundred years, creating a world where we all prefer to live in the digital

03:36:55.480 | world, and not like a visit, but like it's like, your scene is insane.

03:37:03.440 | No, like you're required, it's unsafe to live outside of the virtual world.

03:37:10.600 | And it's interesting to me from an engineering perspective, how to build that, because I'm

03:37:15.160 | somebody that sort of loves video games, and it seems like you can create incredible worlds

03:37:20.520 | there and stay there.

03:37:22.480 | And it's a different question than creating an ultra high resolution, high fidelity simulation

03:37:31.320 | of physics.

03:37:32.800 | But if that world inside a video game is as consistent as the physics of our reality,

03:37:39.960 | you can have your own scientists in that world, trying to understand that physics world.

03:37:44.240 | It might look different.

03:37:45.240 | - I'm presuming that eventually, forget, you know, give it long enough, they might forget

03:37:49.760 | about their origins of being once biological, and assume this was their only reality.

03:37:54.880 | - Especially if you're now born, you know, well certainly if you're born, but even if

03:38:00.680 | you were eight years old or something when you first started wearing the headset.

03:38:04.920 | - Yeah, or you have a memory wipe when you go in.

03:38:07.520 | I mean, it also kind of maybe speaks to this issue of like Neuralink, and how do we keep

03:38:12.320 | up with AI in our world?

03:38:15.240 | If you want to augment your intelligence, perhaps one way of competing, and one of your

03:38:20.480 | impetuses for going into this digital reality would be to be competitive intellectually

03:38:26.240 | with artificial intelligences, that you could trivially augment your reality if your brain

03:38:31.560 | was itself artificial.

03:38:33.000 | But I mean, one skepticism I've always had about that is whether, it's more of a philosophical

03:38:38.600 | question, but how much is that really you if you do a mind upload?

03:38:42.100 | Is this just a duplicate of your memories that thinks it's you versus truly a transference

03:38:49.280 | of your conscious stream into that reality?

03:38:52.600 | And I think when you, it's almost like the teleportation device in Star Trek, but with

03:39:00.760 | teleportation, quantum teleportation, you can kind of rigorously show that as long as

03:39:07.140 | all of the quantum numbers are exactly duplicated as you transfer over, it truly is, from the

03:39:13.160 | universe's perspective, in every way indistinguishable from what was there before.

03:39:18.460 | It really is, in principle, you, and all the sense of being you, versus creating a duplicate

03:39:25.100 | clone and uploading memories to that human body or a computer that would surely be a

03:39:34.500 | discontinuation of that conscious experience by virtue of the fact you've multiplied it.

03:39:39.040 | And so I would be hesitant about uploading for that reason.

03:39:43.580 | I would see it mostly as my own killing myself and having some AI duplicate of me that persists

03:39:53.300 | in this world, but is not truly my experience.

03:39:56.780 | Typical 20th century human, with an attachment to this particular singular instantiation

03:40:04.940 | of brain and body.

03:40:08.060 | How silly humans used to be.

03:40:09.380 | Used to have rotary phones and other silly things.

03:40:19.380 | You're an incredible human being.

03:40:20.900 | You're an educator.

03:40:22.060 | You're a researcher.

03:40:24.780 | You have an amazing YouTube channel.

03:40:31.380 | Looking to young people, if you were to give them advice, how can they have a career that

03:40:37.900 | maybe is inspired by yours, inspired by wandering curiosity, a career they can be proud of,

03:40:44.220 | or a life they can be proud of?

03:40:46.660 | What advice would you give?

03:40:49.460 | I certainly think in terms of a career in science, one thing that I maybe discovered

03:40:55.220 | late but has been incredibly influential on me in terms of my own happiness and my own

03:41:02.780 | productivity has been this synergy of doing two passions at once.

03:41:08.980 | One passion is science communication, another passion research, and not surrendering either

03:41:14.420 | one.

03:41:15.420 | And I think that tends to be seen as something that's an either/or.

03:41:19.860 | You have to completely dedicate yourself to one thing to gain mastery in it.

03:41:24.620 | That's a conventional way of thinking about both science and other disciplines.

03:41:29.940 | And I have found that both have been elevated by practicing in each.

03:41:35.260 | And I think that's true in all assets of life.

03:41:38.420 | If you want to become the best researcher you possibly can, you're pushing your intellect

03:41:45.620 | and in a sense your body to a high level.

03:41:49.380 | And so to me, I've always wanted to couple that with training of my body, training of

03:41:54.860 | my mind in other ways besides from just what I'm doing when I'm in the lecture room or

03:41:59.220 | when I'm in my office calculating something.

03:42:04.540 | Working on your own development through whatever it is, meditation, for me it's often running,

03:42:11.220 | working out and pursuing multiple passions, provides this almost synergistic bliss of

03:42:19.020 | all of them together.

03:42:20.500 | So often I've had some of the best research ideas from making a YouTube video and trying

03:42:25.860 | to communicate an idea or interacting with my audience who've had a question that sparked

03:42:30.620 | a whole trail of thought that led down this wonderful intellectual rabbit hole or maybe

03:42:35.500 | to a new intellectual discovery.

03:42:36.980 | It can go either way sometimes with those things.

03:42:40.700 | And so thinking broadly, diversely, and always looking after yourself in this highly competitive

03:42:49.460 | and often extremely stressful world that we live in is the best advice I can offer anybody.

03:42:57.820 | And just try, if you can, it's very cheesy, but if you can follow your passions, you'll

03:43:02.780 | always be happy.

03:43:04.380 | Trying to sell out for the quick cash out, for the quick book out, can be tempting in

03:43:11.100 | the short term.

03:43:12.100 | Looking for exo-moons was never easy, but I made a career not out of discovering exo-moons,

03:43:18.740 | but out of learning how to communicate the difficult problem and discovering all sorts

03:43:22.940 | of things along the way.

03:43:23.940 | You know, we shot for the sky and we discovered all this stuff along the way.

03:43:27.460 | We discovered dozens of new planets using all sorts of new techniques.

03:43:31.620 | We pushed this instrumentation to new places.

03:43:34.620 | And I've had an extremely productive research career in this world.

03:43:39.260 | I've had all sorts of ideas, working on techno-signatures.

03:43:43.940 | Thinking innovatively pushes you into all sorts of exciting directions.

03:43:49.740 | So just try to, yeah, it's hard to find that passion, but you can sometimes remember when

03:43:56.140 | you were a kid what your passions were and what fascinated you as a child.

03:43:59.980 | For me, as soon as I picked up a space book when I was five years old, that was it.

03:44:04.300 | I was hooked on space.

03:44:05.580 | And I almost betrayed my passion at college.

03:44:08.580 | I studied physics, which I've always been fascinated by physics as well.

03:44:13.020 | But I came back to astronomy because it was my first love, and I was much happier doing

03:44:18.420 | research in astronomy than I was in physics because it spoke to that wonder I had as a

03:44:24.580 | child that first was the spark of curiosity for me in science.

03:44:29.460 | - So society will try to get you to look at hot Jupiters, and the advice is to look for

03:44:35.140 | the cool worlds instead.

03:44:36.140 | What do you think is the meaning of this whole thing?

03:44:38.660 | Have you ever asked yourself why?

03:44:41.780 | - It's just a ride.

03:44:44.100 | It's just a ride.

03:44:45.100 | We're on a roller coaster.

03:44:46.980 | And we have no purpose.

03:44:49.740 | It's an accident in my perspective.

03:44:52.580 | There's no meaning to my life.

03:44:54.220 | There's no objective deity who is overwatching what I'm doing, and I have some fate or destiny.

03:45:01.940 | It's all just riding on a roller coaster and trying to have a good time and contribute

03:45:09.860 | to other people's enjoyment of the ride.

03:45:12.660 | - Yeah, try to make it a happy accident.

03:45:15.540 | - Yeah, yeah.

03:45:16.540 | I see no fundamental providence in my life or in the nature of the universe.

03:45:24.700 | And you just see this universe as this beautiful cosmic accident of galaxies smashing together,

03:45:31.820 | stars forging here and there, and planets occasionally spawning maybe life across the

03:45:37.060 | universe.

03:45:38.740 | And we are just one of those instantiations, and we should just enjoy this very brief episode

03:45:44.900 | that we have.

03:45:47.100 | I think trying to look at it much deeper than that is, to me, it's not very soul satisfying.

03:45:55.700 | I just think enjoy what you've got and appreciate it.

03:45:59.020 | - It does seem noticing that beauty helps make the ride pretty fun.

03:46:05.340 | - Yeah, absolutely.

03:46:06.980 | - David, you're an incredible person.

03:46:08.660 | I haven't covered most of the things I wanted to talk to you about.

03:46:11.380 | This was an incredible conversation.

03:46:13.620 | I'm glad you exist.

03:46:14.620 | I'm glad you're doing everything you're doing.

03:46:17.460 | I'm a huge fan.

03:46:18.460 | Thank you so much for talking today.

03:46:19.460 | This was amazing.

03:46:20.460 | - Thank you so much, Lex.

03:46:21.460 | It's a real honor.

03:46:22.460 | Thank you.

03:46:23.460 | - Thanks for listening to this conversation with David Kipping.

03:46:25.380 | To support this podcast, please check out our sponsors in the description.

03:46:29.380 | And now, let me leave you with some words from Carl Sagan.

03:46:33.460 | Perhaps the aliens are here, but are hiding because of some Lex Galactica, some ethic

03:46:40.220 | of non-interference with emerging civilizations.

03:46:42.940 | We can imagine them, curious and dispassionate, observing us as we would watch a bacterial

03:46:50.140 | culture in a dish to determine whether this year, again, we manage to avoid self-destruction.

03:46:57.900 | Thank you for listening and hope to see you next time.

03:47:00.340 | Bye.

03:47:01.340 | - Bye.

03:47:01.420 | - Bye.

03:47:01.920 | - Bye.

03:47:02.420 | - Bye.

03:47:02.920 | - Bye.

03:47:03.420 | - Bye.

03:47:03.920 | - Bye.

03:47:04.420 | [BLANK_AUDIO]

David Kipping: Alien Civilizations and Habitable Worlds | Lex Fridman Podcast #355

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