Alex Filippenko: Supernovae, Dark Energy, Aliens & the Expanding Universe

00:00:00.000 | "The following is a conversation with Alex Filipenko,

00:00:03.100 | "an astrophysicist and professor of astronomy from Berkeley.

00:00:06.940 | "He was a member of both the Supernova Cosmology Project

00:00:10.540 | "and the Hi-Z Supernova Search Team,

00:00:12.700 | "which used observations of the extragalactic supernova

00:00:16.860 | "to discover that the universe is accelerating,

00:00:19.940 | "and that this implies the existence of dark energy.

00:00:23.620 | "This discovery resulted in the 2011 NOBA Prize for Physics.

00:00:28.700 | "Outside of his groundbreaking research,

00:00:30.860 | "he's a great science communicator

00:00:33.320 | "and is one of the most widely admired educators

00:00:36.260 | "in the world.

00:00:37.620 | "I really enjoyed this conversation

00:00:39.300 | "and I'm sure Alex will be back again in the future.

00:00:42.900 | "Quick mention of each sponsor,

00:00:44.580 | "followed by some thoughts related to the episode.

00:00:47.680 | "Nuro, the maker of functional sugar-free gum and mints

00:00:51.580 | "that I used to give my brain a quick caffeine boost.

00:00:55.260 | "BetterHelp, an online therapy with a licensed professional.

00:00:59.280 | "MasterClass, online courses that I enjoy

00:01:02.460 | "from some of the most amazing humans in history.

00:01:05.580 | "And Cash App, the app I use to send money to friends.

00:01:09.320 | "Please check out these sponsors in the description

00:01:11.380 | "to get a discount and to support this podcast.

00:01:14.680 | "As a side note, let me say that,

00:01:16.740 | "as we talk about in this conversation,

00:01:19.220 | "the objects that populate the universe

00:01:21.580 | "are both awe-inspiring and terrifying

00:01:24.580 | "in their capacity to create and to destroy us.

00:01:28.700 | "Solar flares and asteroids

00:01:30.900 | "lurking in the darkness of space

00:01:33.160 | "threaten our humble, fragile existence here on Earth.

00:01:37.300 | "In the chaos, tension, conflict,

00:01:39.740 | "and social division of 2020,

00:01:42.340 | "it's easy to forget just how lucky we humans are

00:01:45.540 | "to be here.

00:01:46.860 | "And with a bit of hard work,

00:01:48.540 | "maybe one day we'll venture out towards the stars."

00:01:53.460 | If you enjoy this thing, subscribe on YouTube,

00:01:55.500 | review it with Fat Stars on Apple Podcast,

00:01:57.620 | follow on Spotify, support on Patreon,

00:02:00.060 | or connect with me on Twitter @LexFriedman.

00:02:03.740 | And now, here's my conversation with Alex Filippenko.

00:02:07.640 | Let's start by talking about the biggest possible thing,

00:02:11.340 | the universe.

00:02:12.300 | - Sure.

00:02:13.140 | - Will the universe expand forever or collapse on itself?

00:02:16.580 | - Well, you know, that's a great question.

00:02:18.060 | That's one of the big questions of cosmology.

00:02:20.620 | And of course, we have evidence

00:02:23.660 | that the matter density is sufficiently low

00:02:25.980 | that the universe will expand forever.

00:02:28.020 | But not only that, there's this weird repulsive effect.

00:02:31.640 | We call it dark energy for want of a better term.

00:02:35.100 | And it appears to be accelerating

00:02:36.860 | the expansion of the universe.

00:02:38.740 | So if that continues, the universe will expand forever.

00:02:42.580 | But it need not necessarily continue.

00:02:44.840 | It could reverse sign,

00:02:46.700 | in which case the universe could,

00:02:48.540 | in principle, collapse at some point in the far, far future.

00:02:53.100 | - So like, in terms of investment advice,

00:02:55.860 | if you were to give me,

00:02:56.860 | and then to bet all my money on one or the other,

00:02:59.380 | where does your intuition currently lie?

00:03:01.420 | - Well, right now I would say that it would expand forever,

00:03:04.260 | because I think that the dark energy

00:03:06.380 | is likely to be just quantum fluctuations of the vacuum.

00:03:11.020 | The vacuum zero energy state is not a state of zero energy.

00:03:15.860 | That is, the ground state is a state of some elevated energy

00:03:19.380 | which has a repulsive effect to it.

00:03:22.060 | And that will never go away,

00:03:23.740 | because it's not something that changes with time.

00:03:26.980 | So if the universe is accelerating now,

00:03:28.900 | it will forever continue to do so.

00:03:31.740 | - And yet, I mean,

00:03:32.980 | you so effortlessly mentioned dark energy.

00:03:36.060 | Do we have any understanding of what the heck that thing is?

00:03:39.380 | - Well, not really.

00:03:40.200 | But we're getting progressively better

00:03:42.460 | observational constraints.

00:03:44.060 | So, you know, different theories of what it might be

00:03:47.540 | predict different sorts of behavior

00:03:49.940 | for the evolution of the universe.

00:03:51.660 | And we've been measuring the evolution of the universe now.

00:03:55.580 | And the data appear to agree with the predictions

00:03:59.100 | of a constant density vacuum energy, a zero point energy.

00:04:04.100 | But one can't prove that that's what it is,

00:04:08.260 | because one would have to show that the numbers,

00:04:12.100 | that the measured numbers agree with the predictions

00:04:14.460 | to an arbitrary number of decimal places.

00:04:17.180 | And of course, even if you've got eight, nine, 10,

00:04:19.580 | 12 decimal places, what if in the 13th one,

00:04:23.020 | the measurements significantly differ from the prediction?

00:04:26.940 | Then the dark energy isn't this vacuum state,

00:04:31.940 | ground state energy of the vacuum.

00:04:35.260 | And so then it could be some sort of a field,

00:04:38.380 | some sort of a new energy, a little bit like light,

00:04:41.380 | like electromagnetism, but very different from light,

00:04:44.860 | that fills space.

00:04:47.340 | And that type of energy could in principle change

00:04:51.300 | in the distant future.

00:04:52.580 | It could become gravitationally attractive for all we know.

00:04:56.340 | There is a historical precedent to that.

00:04:58.300 | And that is that the inflation

00:05:00.420 | with which the universe began

00:05:02.060 | when the universe was just a tiny blink of an eye old,

00:05:06.420 | a trillionth of a trillionth of a trillionth of a second,

00:05:08.660 | you know, the universe went whoosh,

00:05:10.100 | it exponentially expanded.

00:05:12.260 | That dark energy like substance, we call it the inflaton,

00:05:16.340 | that which inflated the universe,

00:05:18.700 | later decayed into more or less normal,

00:05:22.260 | gravitationally attractive matter.

00:05:24.540 | So the exponential early expansion of the universe

00:05:27.780 | did transition to a deceleration,

00:05:31.620 | which then dominated the universe

00:05:33.140 | for about 9 billion years.

00:05:34.940 | And now this small amount of dark energy

00:05:39.820 | started causing an acceleration

00:05:41.740 | about 5 billion years ago.

00:05:43.420 | And whether that will continue or not

00:05:45.860 | is something that we'd like to answer,

00:05:47.780 | but I don't know that we will anytime soon.

00:05:50.900 | - So there could be this interesting field

00:05:53.340 | that we don't yet understand that's morphing over time,

00:05:56.900 | that's changing the way the universe is expanding.

00:05:59.580 | I mean, it's funny that you were thinking

00:06:03.260 | through this rigorously like an experimentalist.

00:06:06.260 | - Yeah.

00:06:07.780 | - What about like the fundamental physics of dark energy?

00:06:11.180 | Is there any understanding of what the heck it is?

00:06:16.180 | Or is this the kind of the God of the gaps

00:06:21.140 | or the field of the gaps?

00:06:22.820 | So like there must be something there

00:06:25.420 | because of what we're observing.

00:06:26.900 | - I'm very much a person who believes

00:06:29.060 | that there's always a cause, you know,

00:06:31.580 | there are no miracles of a supernatural nature.

00:06:37.140 | Okay.

00:06:37.980 | So, I mean, there are two broad categories,

00:06:42.020 | either it's the vacuum zero point energy,

00:06:45.180 | or it's some sort of a new energy field

00:06:48.060 | that pervades the universe.

00:06:50.380 | The latter could change with time.

00:06:53.500 | The former, the vacuum energy cannot.

00:06:55.860 | So if it turns out that it's one of these new fields

00:06:59.220 | and there are many, many possibilities,

00:07:00.940 | they go by the name of, you know,

00:07:02.140 | quintessence and things like that.

00:07:04.380 | But there are many categories of those sorts of fields.

00:07:08.340 | We try with data to rule them out

00:07:12.140 | by comparing the actual measurements with the predictions.

00:07:16.300 | And some have been ruled out,

00:07:17.820 | but many, many others remain to be tested.

00:07:21.860 | And the data just have to become a lot better

00:07:24.340 | before we can rule out most of them

00:07:27.180 | and become reasonably convinced that this is a vacuum energy.

00:07:31.900 | - So there is hypotheses for different fields?

00:07:34.100 | - Oh yeah. - Like with names

00:07:35.140 | and stuff like that? - Yeah, yeah.

00:07:35.980 | You know, generically quintessence

00:07:37.620 | like the Aristotelian fifth essence,

00:07:39.900 | but there are many, many versions of quintessence.

00:07:42.700 | There's K-essence.

00:07:44.420 | There's even ideas that, you know,

00:07:47.020 | this isn't something from within this dark energy,

00:07:49.740 | but rather there are a bunch of, say, bubble universes

00:07:53.700 | surrounding our universe.

00:07:55.380 | And this whole idea of the multiverse

00:07:57.180 | is not some crazy madman type idea anymore.

00:08:00.460 | It's, you know, real card-carrying physicists

00:08:02.580 | are seriously considering this possibility of a multiverse.

00:08:06.060 | And some types of multiverses could have, you know,

00:08:08.660 | a bunch of bubbles on the outside,

00:08:10.540 | which gravitationally act outward on our bubble

00:08:15.100 | because gravity or gravitons,

00:08:17.580 | the quantum particle that is thought to carry gravity

00:08:20.540 | is thought to traverse the bulk,

00:08:23.700 | the space between these different little bubble membranes

00:08:26.740 | and stuff.

00:08:27.580 | And so it's conceivable that these other universes

00:08:29.820 | are pulling outward on us.

00:08:31.340 | That's not a favored explanation right now,

00:08:33.620 | but really nothing has been ruled out.

00:08:37.900 | No class of models has been ruled out completely.

00:08:41.300 | Certain examples within classes of models

00:08:44.460 | have been ruled out.

00:08:45.740 | But in general, I think we still have really a lot to learn

00:08:50.180 | about what's causing this observed acceleration

00:08:53.900 | of the expansion of the universe,

00:08:55.380 | be it dark energy or some forces from the outside

00:09:00.300 | or perhaps, you know, I guess it's conceivable that,

00:09:05.140 | and sometimes I wake up in the middle of the night

00:09:07.020 | screaming that dark energy,

00:09:09.900 | that which causes the acceleration and dark matter,

00:09:13.460 | that which causes galaxies and clusters of galaxies

00:09:16.300 | to be bound gravitationally,

00:09:18.180 | even though there's not enough visible matter to do so.

00:09:21.020 | Maybe these are our 20th and 21st century

00:09:26.020 | Ptolemaic epicycles.

00:09:28.220 | So Ptolemy had a geocentric and Aristotelian view of the world.

00:09:32.500 | Everything goes around Earth.

00:09:34.340 | But in order to explain the backward motion of planets

00:09:38.900 | among the stars that happens every year or two,

00:09:41.500 | or sometimes several times a year for Mercury and Venus,

00:09:44.940 | you needed the planets to go around in little circles

00:09:47.660 | called epicycles, which themselves then went around Earth.

00:09:52.100 | And in this part of the epicycle

00:09:54.980 | where the planet is going in the direction opposite

00:09:58.940 | to the direction of the overall epicycle,

00:10:01.340 | it can appear in projection

00:10:03.460 | to be going backward among the stars,

00:10:05.540 | so-called retrograde motion.

00:10:07.940 | And it was a brilliant mathematical scheme.

00:10:10.260 | In fact, he could have added epicycles on top of epicycles

00:10:14.460 | and reproduce the observed positions of planets

00:10:17.620 | to arbitrary accuracy.

00:10:19.620 | And this is really the beginning

00:10:21.140 | of what we now call Fourier analysis, right?

00:10:24.580 | Any periodic function can be represented

00:10:27.740 | by a sum of sines and cosines of different periods,

00:10:31.540 | amplitudes, and phases.

00:10:33.460 | So it could have worked arbitrarily well.

00:10:36.260 | But other data show that, in fact,

00:10:39.820 | Earth is going around the sun.

00:10:41.980 | So are dark energy and dark matter

00:10:45.780 | just these band-aids that we now have

00:10:48.460 | to try to explain the data,

00:10:50.740 | but they're just completely wrong?

00:10:52.980 | That's a possibility as well.

00:10:54.660 | And as a scientist, I have to be open to that possibility

00:10:58.060 | as an open-minded scientist.

00:10:59.740 | - How do you put yourself in the mindset of somebody

00:11:03.220 | that, or a majority of the scientific community,

00:11:05.780 | or a majority of people believe

00:11:07.140 | that the Earth, everything rotates around Earth,

00:11:09.620 | how do you put yourself in that mindset

00:11:13.500 | and then take a leap to propose a model

00:11:20.500 | that the sun is, in fact,

00:11:23.180 | at the center of the solar system?

00:11:25.940 | - Sure, I mean, so that puts us back

00:11:27.620 | in the shoes of Copernicus, right?

00:11:29.900 | 500 years ago, where he had this philosophical preference

00:11:34.900 | for the sun being the dominant body

00:11:38.980 | in what we now call the solar system.

00:11:41.300 | The observational evidence,

00:11:44.100 | in terms of the measured positions of planets,

00:11:47.380 | was not better explained

00:11:49.620 | by the heliocentric sun-centered system.

00:11:53.380 | It's just that Copernicus saw that the sun

00:11:55.820 | is the source of all our light and heat.

00:11:58.540 | - Oh, wow, interesting.

00:11:59.980 | - And he knew from other studies that it's far away,

00:12:03.820 | so the fact that it appears as big as the moon

00:12:06.300 | means it's actually way, way bigger,

00:12:08.220 | because even at that time,

00:12:09.340 | it was known that the sun is much farther away than the moon.

00:12:12.660 | So he just felt, wow, it's big, it's bright.

00:12:16.180 | What if it's the central thing?

00:12:18.580 | But the observed positions of planets at the time,

00:12:23.080 | in the early to mid 16th century,

00:12:26.540 | under the heliocentric system, was not a better match,

00:12:30.040 | at least not a significantly better match

00:12:32.360 | than Ptolemy's system, which was quite accurate

00:12:35.160 | and lasted 1,500 years.

00:12:37.260 | - Yeah. - Yeah.

00:12:38.460 | - That's so fascinating to think

00:12:41.100 | that the philosophical predispositions

00:12:44.060 | that you bring to the table are essential.

00:12:45.900 | So you have to have a young person come along

00:12:48.500 | that has a weird infatuation with the sun.

00:12:51.260 | - Yeah. (laughs)

00:12:52.700 | - Like almost philosophically is,

00:12:54.940 | like however their upbringing is,

00:12:57.340 | they're more ready for whatever the more,

00:13:00.660 | the simpler answer is. - Right.

00:13:02.680 | - Oh, that's kind of sad.

00:13:07.060 | It's sad from an individual descendant of ape perspective,

00:13:10.700 | because then that means, like me, you as a scientist,

00:13:16.100 | you're stuck with whatever the heck philosophies

00:13:19.100 | you brought to the table,

00:13:20.060 | and you might be almost completely unable

00:13:22.940 | to think outside this particular box you've built.

00:13:25.660 | - Right, this is why I'm saying that, you know,

00:13:27.500 | as an objective scientist, one needs to have an open mind

00:13:30.900 | to crazy-sounding new ideas. - Exactly, yeah.

00:13:34.060 | - And, you know, even Copernicus was very much a man

00:13:37.260 | of his time and dedicated his work to the pope.

00:13:40.140 | He still used circular orbits.

00:13:43.100 | The sun was a little bit off-center, it turns out,

00:13:46.140 | and a slightly off-center circle

00:13:48.700 | looks like a slightly eccentric elliptical orbit.

00:13:52.180 | So then when Kepler, in fact,

00:13:54.500 | showed that the orbits are actually, in general,

00:13:57.100 | ellipses, not circles, the reason that, you know,

00:14:01.620 | he needed Tuco Brahe's really great data

00:14:05.740 | to show that distinction

00:14:07.620 | was that a slightly off-center circle

00:14:09.820 | is not much different from a slightly eccentric ellipse.

00:14:13.500 | And so there wasn't much difference

00:14:15.620 | between Kepler's view and Copernicus's view,

00:14:19.740 | and Kepler needed the better data, Tuco Brahe's data.

00:14:24.580 | And so that's, again, a great example of science

00:14:29.580 | and observations and experiments

00:14:32.700 | working together with hypotheses,

00:14:34.660 | and they kind of bounce off each other.

00:14:36.940 | They play off of each other,

00:14:38.180 | and you continually need more observations.

00:14:40.700 | And it wasn't until Galileo's work around 1610

00:14:45.700 | that actual evidence for the heliocentric hypothesis emerged.

00:14:50.980 | It came in the form of Venus, the planet Venus,

00:14:54.020 | going through all of the possible phases,

00:14:56.900 | from new to crescent to quarter to gibbous to full

00:15:01.180 | to waning gibbous, third quarter, waning crescent,

00:15:03.700 | and then new again.

00:15:04.940 | It turns out in the Ptolemaic system,

00:15:07.180 | with Venus between Earth and the sun,

00:15:09.980 | but always roughly in the direction of the sun,

00:15:12.740 | you could only get the new and crescent phases of Venus.

00:15:17.460 | But the observations showed a full set of phases.

00:15:21.540 | And moreover, when Venus was gibbous or full,

00:15:24.660 | that meant it was on the far side of the sun.

00:15:26.580 | That meant it was farther from Earth than when it's crescent

00:15:29.740 | so it should appear smaller, and indeed it did.

00:15:32.940 | So that was the nail in the coffin, in a sense.

00:15:36.620 | And then, you know, Galileo's other great observation

00:15:39.140 | was that Jupiter has moons going around it,

00:15:42.460 | the four Galilean satellites.

00:15:44.300 | And even though Jupiter moves through space,

00:15:46.820 | so too do the moons go with it.

00:15:49.380 | So first of all, Earth is not the only thing

00:15:51.820 | that has other things going around it.

00:15:53.740 | And secondly, Earth could be moving, as Jupiter does,

00:15:58.220 | and, you know, things would move with it.

00:16:01.140 | We wouldn't fly off the surface

00:16:02.780 | and our moon wouldn't be left behind

00:16:04.260 | and all this kind of stuff.

00:16:05.220 | So that was a big breakthrough as well,

00:16:07.980 | but it wasn't as definitive, in my opinion,

00:16:10.700 | as the phases of Venus.

00:16:13.460 | - Perhaps I'm revealing my ignorance,

00:16:15.100 | but I didn't realize how much data they were working with.

00:16:18.260 | - Yeah.

00:16:19.100 | - So there's, so it wasn't Einstein

00:16:22.340 | or Freud thinking in theories.

00:16:26.940 | It was a lot of data and you're playing with it

00:16:29.740 | and seeing how to make sense of it.

00:16:31.380 | So it isn't just coming up

00:16:33.420 | with completely abstract thought experiments.

00:16:36.180 | - Yeah.

00:16:37.020 | - It's looking at the data.

00:16:38.260 | - Sure, and you look at Newton's great work, right?

00:16:40.380 | The Principia.

00:16:41.780 | It was based in part on Galileo's observations

00:16:45.620 | of balls rolling down inclined planes,

00:16:48.540 | supposedly falling off the Leaning Tower of Pisa,

00:16:51.100 | but that's probably apocryphal.

00:16:53.140 | In any case, you know, the Inquisition actually did,

00:16:58.540 | or the Roman Catholic Church did history a favor,

00:17:02.860 | not that I'm condoning them,

00:17:04.000 | but they placed Galileo under house arrest.

00:17:06.460 | - Yeah.

00:17:07.300 | - And that gave Galileo time to publish,

00:17:09.840 | to assemble and publish the results of his experiments

00:17:13.400 | that he had done decades earlier.

00:17:15.520 | It's not clear he would have had time to do that, you know,

00:17:18.540 | had he not been under house arrest.

00:17:21.300 | And so Newton, of course,

00:17:23.540 | very much used Galileo's observations.

00:17:27.460 | - Let me ask the old Russian overly philosophical question

00:17:31.940 | about death.

00:17:33.140 | So we're talking about the expanding universe.

00:17:36.420 | - Sure.

00:17:37.380 | - How do you think human civilization will come to an end

00:17:40.120 | if we avoid the near-term issues we're having?

00:17:43.520 | Will it be our sun burning out?

00:17:47.140 | Will it be comets?

00:17:48.420 | - Oh, okay.

00:17:49.260 | - Will it be, what is it?

00:17:52.500 | Do you think we have a shot at reaching

00:17:54.900 | the heat death of the universe?

00:17:58.780 | - Yeah, so we're gonna leave out the anthropogenic-

00:18:03.180 | - Nuclear war. - Causes of our

00:18:05.980 | potential destruction.

00:18:07.140 | - Yes.

00:18:07.980 | - Which I actually think are greater

00:18:09.740 | than the celestial causes.

00:18:14.340 | So-

00:18:15.180 | - So if we get lucky.

00:18:16.180 | - Yeah, if we get lucky.

00:18:17.020 | - And intelligent, I don't know.

00:18:18.220 | - Yeah, so no way will we as humans

00:18:21.180 | reach the heat death of the universe.

00:18:23.380 | I mean, it's conceivable that machines,

00:18:26.780 | which I think will be our evolutionary descendants,

00:18:29.820 | might reach that, although even they

00:18:32.140 | will have less and less energy with which to work

00:18:34.580 | as time progresses, because eventually

00:18:37.300 | even the lowest mass stars burn out,

00:18:40.140 | although it takes them trillions of years to do so.

00:18:42.780 | So the point is that certainly on Earth,

00:18:47.420 | there are other celestial threats, existential threats,

00:18:52.180 | comets, exploding stars, the sun burning out.

00:18:56.860 | So we will definitely need to move away

00:18:59.300 | from our solar system to other solar systems.

00:19:02.260 | And then the question is, can they keep on propagating

00:19:07.260 | to other planetary systems sufficiently long?

00:19:10.580 | In our own solar system, the sun burning out

00:19:15.380 | is not the immediate existential threat.

00:19:20.500 | That'll happen in about 5 billion years

00:19:22.940 | when it becomes a red giant.

00:19:24.420 | Although I should hasten to add

00:19:26.460 | that within the next 1 or 2 billion years,

00:19:29.060 | the sun will have brightened enough

00:19:31.260 | that unless there are compensatory atmospheric changes,

00:19:36.260 | the oceans will evaporate away.

00:19:39.140 | And you need much less carbon dioxide

00:19:41.580 | for the temperatures to be maintained roughly

00:19:44.340 | at their present temperature,

00:19:45.580 | and plants wouldn't like that very much.

00:19:47.780 | So you can't lower the carbon dioxide content too much.

00:19:50.540 | So within 1 or 2 billion years,

00:19:53.380 | probably the oceans will evaporate away.

00:19:56.140 | But on a sooner timescale than that,

00:19:59.420 | I would say an asteroid collision

00:20:01.700 | leading to a potential mass extinction,

00:20:04.180 | or at least an extinction of complex beings

00:20:06.660 | such as ourselves that require quite special conditions,

00:20:10.900 | unlike cockroaches and amoebas, to survive.

00:20:16.100 | One of these civilization-changing asteroids

00:20:20.260 | is only one kilometer or so in diameter and bigger,

00:20:23.900 | and a true mass extinction event is 10 kilometers or larger.

00:20:28.780 | Now, it's true that we can find and track

00:20:31.740 | the orbits of asteroids that might be headed toward Earth.

00:20:34.940 | And if we find them 50 or 100 years before they impact us,

00:20:38.580 | then clever applied physicists and engineers

00:20:41.140 | can figure out ways to deflect them.

00:20:43.380 | But at some point, some comet will come in

00:20:45.940 | from the deep freeze of the solar system.

00:20:48.460 | And there we have very little warning, months to a year.

00:20:52.700 | - What's a deep freeze, Sarge?

00:20:54.020 | - Oh, the deep freeze is sort of out beyond Neptune.

00:20:56.900 | There's this thing called the Kuiper Belt,

00:20:59.140 | and it consists of a bunch of dirty ice balls

00:21:03.580 | or icy dirt balls.

00:21:04.820 | It's the source of the comets

00:21:06.740 | that occasionally come close to the sun.

00:21:08.780 | And then there's a even bigger area

00:21:11.660 | called the scattered disk,

00:21:13.020 | which is sort of a big donut

00:21:14.540 | surrounding the solar system way out there

00:21:16.580 | from which other comets come.

00:21:17.780 | And then there's the Oort cloud,

00:21:19.460 | W-O-O-R-T after Jan Oort, a Dutch astrophysicist.

00:21:24.460 | And it's the better part of a light year away from the sun.

00:21:29.020 | So a good fraction of the distance to the nearest star,

00:21:31.980 | but that's like a trillion or 10 trillion

00:21:34.300 | comet-like objects that occasionally get disturbed

00:21:38.420 | by a passing star or whatever.

00:21:39.980 | And most of them go flying out of the solar system,

00:21:41.980 | but some go toward the sun.

00:21:44.380 | And they come in with little warning.

00:21:46.900 | By the time we can see them,

00:21:49.900 | they're only a year or two away from us.

00:21:53.060 | And moreover, not only is it hard

00:21:55.500 | to determine their trajectories sufficiently accurately

00:21:59.180 | to know whether they'll hit a tiny thing like Earth,

00:22:01.940 | but outgassing from the comet of gases,

00:22:06.940 | when the ices sublimate,

00:22:08.780 | that outgassing can change the trajectory

00:22:12.260 | just because of conservation of momentum, right?

00:22:14.420 | It's the rocket effect.

00:22:15.580 | Gases go out in one direction,

00:22:17.380 | the object moves in the other direction.

00:22:18.980 | And so since we can't predict how much outgassing

00:22:22.420 | there will be and in exactly what direction,

00:22:25.020 | because these things are tumbling and rotating and stuff,

00:22:28.020 | it's hard to predict the trajectory

00:22:30.500 | with sufficient accuracy to know that it will hit.

00:22:33.180 | And you certainly don't want to deflect a comet

00:22:36.680 | that would have missed,

00:22:38.340 | but you thought it was gonna hit and end up having it hit.

00:22:41.900 | That would be like the ultimate Charlie Brown, you know,

00:22:44.940 | goat instead of trying to be the hero, right?

00:22:47.180 | He ended up being the goat.

00:22:49.380 | - What would you do if,

00:22:52.260 | it seemed like in a matter of months

00:22:56.000 | that there is some non-zero probability,

00:22:58.900 | maybe a high probability that there would be a collision?

00:23:02.340 | So from a scientific perspective,

00:23:04.260 | from an engineering perspective,

00:23:05.820 | I imagine you would actually be in the room

00:23:08.020 | of people deciding what to do.

00:23:10.340 | What, philosophically too.

00:23:12.620 | - It's a tough one, right?

00:23:13.540 | Because if you only have a few months,

00:23:15.980 | that's not much time in which to deflect it.

00:23:19.240 | Early detection and early action are key

00:23:24.240 | 'cause when it's far away,

00:23:26.700 | you only have to deflect it by a tiny little angle.

00:23:30.220 | And then by the time it reaches us,

00:23:31.940 | the perpendicular motion is big enough to, you know,

00:23:36.100 | to miss Earth.

00:23:37.060 | All you need is one radius

00:23:38.340 | or one diameter of the Earth, right?

00:23:40.260 | That actually means that all you would need to do

00:23:43.380 | is slow it down so it arrives four minutes later

00:23:48.180 | or speed it up so it arrives four minutes earlier

00:23:50.940 | and Earth will have moved through one radius in that time.

00:23:55.940 | So it doesn't take much,

00:23:57.240 | but you can imagine if a thing is about to hit you,

00:24:00.300 | you have to deflect it 90 degrees or more, right?

00:24:03.460 | You know, and you don't have much time to do so

00:24:05.020 | and you have to slow it down or speed it up a lot

00:24:07.820 | if that's what you're trying to do to it.

00:24:09.140 | And so decades is sufficient time,

00:24:12.300 | but months is not sufficient time.

00:24:14.540 | So at that point, I would think the name of the game

00:24:18.780 | would be to try to predict where it would hit.

00:24:21.240 | And if it's in a heavily populated region,

00:24:25.120 | try to start an orderly evacuation perhaps.

00:24:31.560 | But you know, that might cause just so much panic

00:24:35.940 | that I'm, how would you do it with New York City

00:24:38.860 | or Los Angeles or something like that, right?

00:24:41.380 | - I might have a different opinion a year ago.

00:24:43.940 | I'm a bit disheartened by, you know, in the movies,

00:24:48.940 | there's always extreme competence from the government.

00:24:53.120 | - Competence, yeah.

00:24:55.420 | - Competence, yeah.

00:24:56.260 | - Right, but we expect extreme incompetence,

00:24:58.900 | if anything, right?

00:24:59.740 | - Yes, now, so I'm quite disappointed.

00:25:02.100 | But sort of from a medical perspective,

00:25:04.100 | I think you're saying there in a scientific one,

00:25:07.580 | it's almost better to get better and better,

00:25:10.940 | maybe telescopes and data collection

00:25:13.140 | to be able to predict the movement of these things

00:25:15.500 | or like come up with totally new technologies.

00:25:17.980 | Like you can imagine actually sending out

00:25:21.460 | like probes out there to be able to sort of almost

00:25:25.100 | have little finger sensors throughout our solar system

00:25:28.260 | to be able to detect stuff.

00:25:29.820 | - Well, that's right.

00:25:30.660 | Yeah, monitoring the asteroid belt is very important.

00:25:33.020 | 99% of the so-called near-Earth objects

00:25:37.420 | ultimately come from the asteroid belt.

00:25:39.220 | And so there we can track the trajectories.

00:25:41.180 | And even if there's, you know, a close encounter

00:25:43.380 | between two asteroids,

00:25:44.420 | which deflects one of them toward Earth,

00:25:47.100 | it's unlikely to be on a collision course with Earth

00:25:49.660 | in the immediate future.

00:25:50.980 | It's more like, you know, tens of years.

00:25:53.280 | So that gives us time.

00:25:54.780 | But we would need to improve our ability

00:25:58.060 | to detect the objects that come in from a great distance.

00:26:01.020 | Unfortunately, those are much rarer.

00:26:04.060 | The comets come in, you know, 1% of the collisions

00:26:07.700 | perhaps are with comets that come in

00:26:11.260 | without any warning, Harvey.

00:26:14.220 | And so that might be more like, you know,

00:26:18.780 | a billion or 2 billion years before one of those hits us.

00:26:21.840 | So maybe we have to worry about the sun getting brighter

00:26:26.900 | on that time scale.

00:26:28.340 | I mean, there's the possibility

00:26:29.940 | that a star will explode near us

00:26:33.380 | in the next couple of billion years.

00:26:35.540 | But over the course of the history of life on Earth,

00:26:40.540 | the estimates are that maybe only one

00:26:45.900 | of the mass extinctions, you know,

00:26:50.180 | was caused by a star blowing up in particular,

00:26:54.020 | a special kind called a gamma ray burst.

00:26:56.300 | And I think it's the Ordovician-Sulurian extinction,

00:27:01.300 | 420 or so, 440 million years ago,

00:27:06.260 | that is speculated to have come from one of these

00:27:08.820 | particular types of exploding stars called gamma ray bursts.

00:27:12.140 | But even there, the evidence is circumstantial.

00:27:15.500 | So those kinds of existential threats are reasonably rare.

00:27:20.500 | The greater danger I think is civilization changing events.

00:27:26.460 | Where it's a much smaller asteroid,

00:27:29.620 | which those are harder to detect.

00:27:31.740 | Or a giant solar flare that shorts out the grid

00:27:36.740 | in all of North America, let's say.

00:27:40.300 | Now, you know, astronomers are monitoring the sun 24/7

00:27:44.100 | with various satellites.

00:27:45.300 | And we can tell when there's a flare

00:27:48.180 | or a coronal mass ejection.

00:27:50.460 | And we can tell that in a day or two,

00:27:52.380 | a giant bundle of energetic particles will arrive

00:27:55.940 | and twang the magnetic field of earth

00:27:58.020 | and send all kinds of currents

00:27:59.300 | through long distance power lines.

00:28:01.220 | And that's what shorts out the transformers.

00:28:04.380 | And transformers are, you know, expensive

00:28:07.460 | and hard to replace and hard to transport

00:28:09.900 | and all that kind of stuff.

00:28:10.740 | So if we can warn the power companies

00:28:14.780 | and they can shut down the grid

00:28:16.500 | before the big bundle of particle hits,

00:28:19.580 | then we will have mitigated much of this.

00:28:21.300 | Now for a big enough bundle of particles,

00:28:23.980 | you can get short circuits even over small distance scales.

00:28:28.100 | So not everything will be saved,

00:28:30.380 | but at least the whole grid might not go out.

00:28:33.540 | So again, you know, astronomers,

00:28:35.500 | I like to say support your local astronomer.

00:28:38.740 | They may help someday save humanity

00:28:41.380 | by telling the power companies to shut down the grid,

00:28:45.100 | finding the asteroid 50 or a hundred years before it hits,

00:28:49.020 | then having clever physicists and engineers deflect it.

00:28:52.180 | So many of these cosmic threats,

00:28:55.580 | cosmic existential threats,

00:28:57.060 | we can actually predict and do something about

00:29:01.500 | or observe before they hit and do something about.

00:29:05.220 | So, you know. - It's terrifying

00:29:07.420 | to think that people would listen to this conversation.

00:29:10.820 | It's like when you listen to Bill Gates

00:29:12.260 | talk about pandemics in his TED Talk a few years ago

00:29:15.660 | and realizing we should have supported

00:29:17.780 | our local astronomer more.

00:29:20.180 | - Well, I don't know whether it's more,

00:29:21.580 | because as I said, I actually think human-induced threats

00:29:25.260 | or things that occur naturally on Earth,

00:29:27.300 | either a natural pandemic

00:29:28.940 | or perhaps, you know, a bioengineering type pandemic

00:29:32.100 | or, you know, something like a super volcano, right?

00:29:34.980 | There was one event, Toba,

00:29:37.860 | I think it was 70 plus thousand years ago

00:29:41.700 | that caused a gigantic decrease in temperatures on Earth

00:29:46.020 | because it sent up so much soot that it blocked the sun, right?

00:29:51.020 | It's the nuclear winter type disaster scenario

00:29:53.620 | that some people, including Carl Sagan,

00:29:55.260 | talked about decades ago.

00:29:57.100 | But we can see in the history of volcanic eruptions,

00:30:00.340 | even more recently in the 19th century,

00:30:02.180 | Tambora and other ones,

00:30:03.700 | you look at the record

00:30:05.260 | and you see rather large dips in temperature

00:30:08.900 | associated with massive volcanic eruptions.

00:30:12.060 | Well, these super volcanoes,

00:30:13.860 | one of which, by the way, exists under Yellowstone,

00:30:16.860 | you know, in the central US.

00:30:19.060 | I mean, it's not just one or two states,

00:30:21.500 | it's a gigantic region.

00:30:23.540 | And there's controversy as to whether it's likely to blow

00:30:27.780 | anytime in the next hundred thousand years or so.

00:30:30.780 | But that would be perhaps not a mass extinction

00:30:33.460 | 'cause you really need to,

00:30:34.860 | or perhaps not a complete existential threat

00:30:37.180 | because you have to get rid of

00:30:38.700 | sort of the very last humans for that.

00:30:41.460 | But at least getting rid of,

00:30:44.460 | you know, killing off so many humans,

00:30:45.940 | truly billions and billions of humans.

00:30:48.300 | The one, there have been ones

00:30:50.420 | tens of thousands of years ago,

00:30:53.180 | including this one, Toba I think it's called,

00:30:57.180 | where it's estimated that the human population

00:30:59.940 | was down to 10,000 or 5,000 individuals,

00:31:03.700 | something like that, right?

00:31:05.060 | If you have a 15 degree drop in temperature

00:31:08.220 | over quite a short time,

00:31:10.380 | it's not clear that even with today's advanced technology,

00:31:13.780 | we would be able to adequately respond,

00:31:15.740 | at least for the vast majority of people.

00:31:18.100 | Maybe some would be in these underground caves

00:31:20.500 | where you'd keep the president

00:31:21.620 | and a bunch of other important people, you know,

00:31:24.020 | but the typical person is not gonna be protected

00:31:27.380 | when all of agriculture is cut off, right?

00:31:31.420 | And when- - It could be hundreds

00:31:32.900 | of millions or billions of people starving to death.

00:31:36.820 | - Exactly, that's right.

00:31:38.100 | They don't all die immediately,

00:31:40.420 | but they use up their supplies,

00:31:42.620 | or again, this electrical grid.

00:31:44.180 | - First of toilet paper.

00:31:45.620 | - There you go, dash that toilet paper, you know,

00:31:49.060 | or the electrical grid.

00:31:50.100 | I mean, imagine North America without power for a year,

00:31:54.260 | right, I mean, we've become so dependent.

00:31:56.460 | We're no longer the cave people.

00:31:58.180 | They would do just fine, right?

00:32:00.140 | What do they care about the electrical grid, right?

00:32:02.420 | What do they care about agriculture?

00:32:04.140 | They're hunters and gatherers,

00:32:05.900 | but we now have become so used to our way of life

00:32:10.540 | that the only real survivors would be

00:32:12.820 | those rugged individualists who live somewhere

00:32:14.940 | out in the forest or in a cave somewhere,

00:32:17.140 | completely independent of anyone else.

00:32:20.380 | - Yeah, I've recently, I recommend it.

00:32:22.380 | It's totally new to me, this kind of survivalist folks,

00:32:25.780 | but there's a few shows, there's a lot of shows of those,

00:32:28.900 | but I saw one on Netflix and I started watching them,

00:32:32.780 | and they make a lot of sense.

00:32:36.660 | They reveal to you how dependent we are

00:32:40.620 | on all aspects of this beautiful systems

00:32:42.820 | we human have built.

00:32:44.060 | - Right.

00:32:44.900 | - And how fragile they are.

00:32:46.780 | - Incredibly fragile.

00:32:48.220 | - And this whole conversation is making me realize

00:32:51.980 | how lucky we are.

00:32:53.140 | - Oh, we're incredibly lucky,

00:32:54.580 | but we've set ourselves up to be very, very fragile,

00:32:58.300 | and we are intrinsically complex biological creatures

00:33:03.020 | that, except for the fact that we have brains and minds

00:33:06.420 | with which we can try to prevent some of these things

00:33:09.980 | or respond to them, we as a living organism

00:33:14.300 | require quite a narrow set of conditions

00:33:17.500 | in order to survive.

00:33:18.660 | We're not cockroaches.

00:33:20.220 | We're not gonna survive a nuclear war.

00:33:22.240 | - So we're kind of, there's this beautiful dance between,

00:33:26.780 | we've been talking about astronomy,

00:33:28.900 | that astronomy, the stars, inspires everybody.

00:33:33.900 | And at the same time, there's this pragmatic aspect

00:33:37.820 | that we're talking about.

00:33:38.900 | And so I see space exploration as the same kind of way,

00:33:42.900 | that it's reaching out to other planets,

00:33:45.420 | reaching out to the stars, this really beautiful idea.

00:33:48.580 | But if you listen to somebody like Elon Musk,

00:33:51.900 | he talks about space exploration as very pragmatic,

00:33:56.700 | like we have to be, (laughs)

00:34:01.180 | he has this ridiculous way of sounding

00:34:02.700 | like an engineer about it, which is like,

00:34:05.300 | it's obvious we need to become a multi-planetary species

00:34:08.340 | if we were to survive long-term.

00:34:10.440 | So maybe both philosophically, in terms of beauty,

00:34:15.440 | and in terms of practical,

00:34:17.260 | what's your thoughts on space exploration,

00:34:21.180 | on the challenges of it,

00:34:22.420 | on how much we should be investing in it,

00:34:24.820 | and on a personal level, how excited you are

00:34:27.620 | by the possibility of going to Mars, colonizing Mars,

00:34:32.060 | and maybe going outside the solar system?

00:34:34.660 | - Yeah, great question.

00:34:36.480 | There's a lot to unpack there, of course.

00:34:39.340 | - Sorry, sorry. (laughs)

00:34:40.860 | - Humans are, by their very nature, explorers, pioneers.

00:34:44.440 | They wanna go out, climb the next mountain,

00:34:46.940 | see what's behind it, explore the ocean depths,

00:34:51.060 | explore space.

00:34:52.400 | This is our destiny, to go out there,

00:34:54.220 | and of course, from a pragmatic perspective,

00:34:57.900 | yes, we need to plant our seeds elsewhere, really,

00:35:02.780 | because things could go wrong here on Earth.

00:35:05.460 | Now, some people say that's an excuse

00:35:09.320 | to not take care of our planet.

00:35:11.220 | Well, we say we're elsewhere,

00:35:12.380 | and so we don't have to take good care of our planet.

00:35:14.260 | No, we should take the best possible care of our planet.

00:35:18.140 | We should be cognizant of the potential impact

00:35:20.820 | of what we're doing.

00:35:21.940 | Nevertheless, it's prudent to have us be elsewhere as well.

00:35:26.740 | So in that regard, I actually agree with Elon.

00:35:29.780 | It'd be good to be on Mars.

00:35:32.380 | That would be yet another place for us to,

00:35:35.060 | from which to explore still further.

00:35:38.100 | - Would that be a good next step?

00:35:39.580 | - Well, it's a good next step.

00:35:41.300 | I happen to disagree with him

00:35:43.500 | as to how quickly it will happen.

00:35:45.860 | Right, I mean, I think he's very optimistic.

00:35:48.060 | Now, you need visionary people like Elon

00:35:50.660 | to get people going and to inspire them.

00:35:52.740 | I mean, look at the success he's had with multiple companies.

00:35:55.780 | So maybe he gives this very optimistic timeline

00:36:00.180 | in order to be inspirational to those

00:36:02.580 | who are going out there.

00:36:04.220 | And certainly his success with the rocket that is reusable,

00:36:08.740 | 'cause it landed upright and all that.

00:36:10.460 | I mean, that's a game changer.

00:36:12.700 | It's sort of like every time you flew

00:36:14.260 | from San Francisco to Los Angeles,

00:36:16.300 | you discard the airplane, right?

00:36:18.020 | I mean, that's crazy, right?

00:36:20.140 | So that's a game changer.

00:36:21.700 | But nevertheless, the timescale over which he thinks

00:36:25.060 | that there could be a real thriving colony on Mars,

00:36:28.140 | I think is far too optimistic.

00:36:30.540 | - What's the biggest challenges to you?

00:36:32.860 | One is just getting rockets, not rockets,

00:36:35.700 | but people out there, and two is the colonization.

00:36:39.180 | - Yeah.

00:36:40.260 | - Do you have thoughts about this,

00:36:42.620 | the challenges of this kind of prospect?

00:36:44.540 | - Yeah, I haven't thought about it in great detail

00:36:47.540 | other than recognizing that Mars is a harsh environment.

00:36:51.540 | You don't have much of an atmosphere there.

00:36:53.300 | You've got less than a percent of Earth's atmosphere.

00:36:56.020 | So you'd need to build some sort of a dome right away,

00:36:59.700 | right, and that would take time.

00:37:02.180 | You need to melt the water that's in the permafrost

00:37:05.460 | or have canals dug from which you transport it

00:37:09.500 | from the polar ice caps.

00:37:11.820 | - You know, I was reading recently in terms of like,

00:37:14.620 | what's the most efficient source of nutrition

00:37:18.220 | for humans that were to live on Mars,

00:37:20.180 | and people should look into this,

00:37:21.660 | but it turns out to be insects.

00:37:23.540 | - Insects, yeah.

00:37:25.020 | - So you wanna build giant colonies of insects

00:37:28.740 | and just be eating them.

00:37:29.580 | - Yeah, insects have a lot of protein, right?

00:37:30.940 | - Yeah, a lot of protein, and they're easy to grow.

00:37:34.140 | Like, you can think of them as farming.

00:37:36.180 | - Right, but it's not gonna be as easy

00:37:39.180 | as growing a whole plot of potatoes

00:37:41.300 | like in the movie "The Martian," you know, or something.

00:37:44.100 | - It's not gonna be that easy, but you know,

00:37:46.260 | so there's this thin atmosphere.

00:37:48.340 | It's got the wrong composition.

00:37:49.580 | It's mostly carbon dioxide.

00:37:51.700 | There are these violent dust storms.

00:37:54.740 | The temperatures are generally cold.

00:37:57.700 | You know, you'd need to do a lot of things.

00:37:59.340 | You need to terraform it, basically,

00:38:01.180 | in order to make it nicely livable

00:38:03.300 | without some dome surrounding you,

00:38:05.820 | and if you insist on a dome,

00:38:08.460 | well, that's not gonna house that many people, right?

00:38:12.380 | - So let's look briefly, then.

00:38:14.820 | We're looking for a new apartment to move into,

00:38:18.540 | so let's look outside the solar system.

00:38:20.620 | Do you think, you've spoken about exoplanets as well.

00:38:25.180 | Do you think there's possible homes out there for us

00:38:29.740 | outside of our solar system?

00:38:31.780 | - There are lots and lots of homes, possible homes.

00:38:34.580 | I mean, there's a planetary system

00:38:37.540 | around nearly every star you see in the sky,

00:38:40.300 | and one in five of those is thought to have

00:38:42.860 | a roughly Earth-like planet.

00:38:45.820 | - And that's a relatively new--

00:38:47.380 | - Yeah, it's a new discovery.

00:38:48.300 | I mean, the Kepler satellite,

00:38:49.860 | which was flying around above Earth's atmosphere,

00:38:52.940 | was able to monitor the brightness of stars

00:38:55.260 | with exquisite detail,

00:38:57.060 | and they could detect planets crossing the line of sight

00:39:01.420 | between us and the star,

00:39:03.580 | thereby dimming its light for a short time,

00:39:06.500 | ever so slightly, and it's amazing.

00:39:09.220 | So there are now thousands and thousands

00:39:11.260 | of these exoplanet candidates,

00:39:13.180 | of which something like 90% are probably genuine exoplanets.

00:39:17.140 | And you have to remember that only about 1% of stars

00:39:22.140 | have their planetary system oriented

00:39:25.140 | edge-on to your line of sight,

00:39:27.300 | which is what you need for this transit method to work.

00:39:31.260 | Some arbitrary angle won't work,

00:39:33.420 | and certainly perpendicular to your line of sight,

00:39:36.100 | that is in the plane of the sky won't work

00:39:38.020 | because the planet is orbiting the star

00:39:40.860 | and never crossing your line of sight.

00:39:43.580 | So the fact that they found planets orbiting

00:39:48.220 | about 1% of the stars that they looked at

00:39:51.260 | in this field of 150-plus thousand stars,

00:39:54.740 | they found planets around 1%,

00:39:57.620 | you then multiply by the inverse of 1%,

00:40:00.940 | which is, you know, right?

00:40:02.620 | 1% is about how many, what, the fraction of the stars

00:40:06.900 | that have their planetary system oriented the right way.

00:40:10.580 | And that already, back of the envelope calculation,

00:40:13.380 | tells you that of order, 50 to 100% of all stars

00:40:17.300 | have planets, okay?

00:40:18.180 | And then they've been finding these earth-like planets,

00:40:20.620 | et cetera, et cetera.

00:40:21.660 | So there are many potential homes.

00:40:23.740 | The problem is getting there, okay?

00:40:26.540 | So then a typical bright star, Sirius,

00:40:30.300 | the brightest star in the sky,

00:40:31.900 | maybe not a typical bright star,

00:40:33.260 | but it's 8.7 light years away, okay?

00:40:37.460 | So that means the light took 8.7 years to reach us.

00:40:42.460 | We're seeing it as it was about nine years ago, okay?

00:40:47.340 | So then, you know, you ask,

00:40:49.300 | how long would a rocket take to get there

00:40:52.300 | at Earth's escape speed, which is 11 kilometers per second?

00:40:56.860 | Okay, and it turns out it's about a quarter

00:40:59.580 | of a million years, okay?

00:41:01.420 | Now that's 10,000 generations, okay?

00:41:03.940 | Let's say a generation of humans is 25 years, right?

00:41:07.260 | So you'd need this colony of people

00:41:10.860 | that is able to sustain itself, all their food,

00:41:14.540 | all their waste disposal, all their water,

00:41:16.860 | all their recycling of everything.

00:41:18.540 | For 10,000 generations, they have to commit themselves

00:41:22.220 | to living on this vehicle, right?

00:41:25.780 | I just don't see it happening.

00:41:28.740 | What I see potentially happening,

00:41:31.100 | if we avoid self-destruction,

00:41:33.020 | intentional or unintentional here on Earth,

00:41:36.100 | is that machines will do it,

00:41:37.860 | robots that can essentially hibernate.

00:41:40.900 | They don't need to do much of anything

00:41:42.660 | for a long, long time as they're traveling.

00:41:44.580 | And moreover, if some energetic charged particle,

00:41:47.460 | some cosmic ray hits the circuitry, it fixes itself, right?

00:41:51.500 | Machines can do this.

00:41:52.740 | I mean, it's a form of artificial intelligence.

00:41:57.900 | You just tell the thing, fix yourself, basically.

00:42:00.020 | And then when you land on the planet,

00:42:02.660 | start producing copies of yourself,

00:42:04.900 | initially from materials that were perhaps sent,

00:42:07.980 | or you just have a bunch of copies there.

00:42:10.020 | And then they set up factories with which to do this.

00:42:13.460 | I mean, this is very, very futuristic,

00:42:15.060 | but it's much more feasible, I think,

00:42:19.380 | than sending flesh and blood over interstellar distances,

00:42:24.380 | a quarter of a million years to even the nearest stars.

00:42:28.340 | You're subject to all kinds of charged particles

00:42:30.980 | and radiation.

00:42:32.100 | You have to shield yourself really well.

00:42:34.260 | That's, by the way, one of the problems of going to Mars

00:42:36.620 | is that it's not a three-day journey like going to the moon.

00:42:39.900 | You're out there for the better part of a year or two,

00:42:43.220 | and you're exposed to lots of radiation,

00:42:46.780 | which typically doesn't do well with living tissue, right?

00:42:51.420 | Or living tissue doesn't do well with the radiation, okay?

00:42:54.420 | - And the hope is that the robots, the AI systems

00:42:58.540 | might be able to carry the fire of consciousness,

00:43:03.540 | whatever makes us humans,

00:43:07.700 | like a little drop of whatever makes us humans so special,

00:43:10.980 | not to be too poetic about it.

00:43:12.700 | - No, but I like being poetic about it,

00:43:14.580 | because it's an amazing question.

00:43:16.420 | Is there something beyond just the bits,

00:43:20.420 | the ones and zeros to us?

00:43:22.300 | It's an interesting question.

00:43:24.740 | I like to think that there isn't anything,

00:43:27.300 | and that how beautiful it is that our thoughts,

00:43:29.460 | our emotions, our feelings, our compassion

00:43:31.780 | all come from these ones and zeros, right?

00:43:35.700 | That, to me, actually is a beautiful thought.

00:43:38.580 | And the idea that machines, silicon-based life, effectively,

00:43:43.300 | could be our natural evolutionary descendants,

00:43:46.380 | not from a DNA perspective, but they are our creations,

00:43:49.820 | and they then carry on.

00:43:51.860 | That, to me, is a beautiful thought in some ways,

00:43:54.180 | but others find it to be a horrific thought, right?

00:43:56.700 | - So that's exciting to you.

00:43:58.380 | It is exciting to me as well,

00:44:00.260 | because to me, from purely an engineering perspective,

00:44:04.380 | I believe it's impossible to create,

00:44:07.900 | like whatever systems we create that take over the world,

00:44:12.700 | it's impossible for me to imagine that those systems

00:44:15.460 | will not carry some aspect of what makes humans beautiful.

00:44:19.740 | So a lot of people have these kind of paperclip ideas

00:44:23.500 | that we'll build machines that are cold inside,

00:44:27.180 | or philosophers call them zombies,

00:44:29.220 | that naturally the systems that will out-compete us

00:44:35.940 | on this earth will be cold and non-conscious,

00:44:40.940 | not capable of all the human emotions

00:44:44.980 | and empathy and compassion and love and hate.

00:44:48.660 | The beautiful mix of what makes us human.

00:44:52.980 | But to me, intelligence requires all of that.

00:44:56.460 | So in order to out-compete humans,

00:44:59.020 | you better be good at the full picture.

00:45:02.020 | - Right, so artificial general intelligence, in my view,

00:45:05.420 | encompasses a lot of these attributes

00:45:08.420 | that you just talked about.

00:45:09.740 | - Yeah, I tend to-- - Like curiosity,

00:45:11.740 | inquisitiveness, you know, right?

00:45:13.500 | - It might look very different than us humans,

00:45:15.700 | but it will have some of the magic.

00:45:17.740 | But it'll also be much more able to survive

00:45:21.460 | the onslaught of existential threats

00:45:23.980 | that either we bring upon ourselves

00:45:26.180 | or don't anticipate here on earth,

00:45:28.180 | or that occasionally come from beyond.

00:45:30.660 | And there's nothing much we can do

00:45:31.740 | about a supernova explosion that just suddenly goes off.

00:45:35.020 | And really, if we wanna move to other planets

00:45:38.460 | outside our solar system, I think realistically,

00:45:42.460 | that's a much better option than thinking

00:45:45.460 | that humans will actually make these gigantic journeys.

00:45:48.460 | And, you know, then I do this calculation for my class.

00:45:51.740 | You know, Einstein's special theory of relativity

00:45:54.180 | says that you can do it in a short amount of time

00:45:56.740 | in your own frame of reference

00:45:58.220 | if you go close to the speed of light.

00:46:00.460 | But then you bring in E equals mc squared,

00:46:02.980 | and you figure out how much energy it takes

00:46:05.660 | to get you accelerated to close enough

00:46:08.620 | to the speed of light to make the time scale short

00:46:11.780 | in your own frame of reference.

00:46:13.780 | And the amount of energy is just unfathomable, right?

00:46:17.300 | We can do it at the Large Hadron Collider with protons.

00:46:21.180 | You know, we can accelerate them to 99.9999%

00:46:24.460 | of the speed of light, but that's just a proton.

00:46:27.420 | We're gazillions of protons, okay?

00:46:29.660 | And that doesn't even count the rocket

00:46:31.580 | that would carry us the payload.

00:46:33.780 | And you would need to either store the fuel in the rocket,

00:46:37.580 | which then requires even more mass for the rocket,

00:46:41.380 | or collect fuel along the way,

00:46:43.500 | which is difficult.

00:46:44.820 | And so getting close to the speed of light, I think,

00:46:47.820 | is not an option either,

00:46:49.460 | other than for a little tiny thing like,

00:46:52.140 | Yuri Milner and others are thinking about

00:46:54.100 | this star shot project

00:46:56.180 | where they'll send a little tiny camera

00:46:58.220 | to Alpha Centauri 4.2 light years away.

00:47:00.940 | They'll zip past it,

00:47:02.300 | take a picture of the exoplanets that we know orbit

00:47:05.540 | that three or more star system, and-

00:47:08.380 | - Say hello real quick. - Say hello real quickly,

00:47:10.220 | and then send the images back to us, okay?

00:47:12.620 | So that's a tiny little thing, right?

00:47:14.700 | Maybe you can accelerate that to,

00:47:16.980 | they're hoping 20% of the speed of light

00:47:19.540 | with a whole bunch of high-powered lasers aimed at it.

00:47:22.620 | It's not clear that other countries

00:47:23.980 | will allow us to do that, by the way.

00:47:25.940 | But that's a very forward-looking thought.

00:47:27.460 | I mean, I very much support the idea,

00:47:29.860 | but there's a big difference

00:47:30.980 | between sending a little tiny camera

00:47:33.140 | and sending a payload of people with equipment

00:47:36.580 | that could then mine the resources on the exoplanet

00:47:42.580 | that they reach and then go forth and multiply, right?

00:47:46.260 | - Well, let's talk about the big galactic things

00:47:49.460 | and how we might be able to leverage them to travel fast.

00:47:52.900 | I know this is a little bit science fiction,

00:47:54.820 | but ideas of wormholes and ideas at the edge of black holes

00:47:59.820 | that reveal to us that this fabric of space-time

00:48:08.140 | could be messed with.

00:48:11.860 | - Yeah.

00:48:12.700 | - Perhaps, is that at all an interesting thing for you?

00:48:16.900 | I mean, in looking out at the universe

00:48:20.060 | and studying it as you have,

00:48:21.980 | is that also a possible, like a dream for you

00:48:26.580 | that we might be able to find clues

00:48:28.100 | how we can actually use it to improve our transportation?

00:48:31.420 | - It's an interesting thought.

00:48:32.540 | I'm certainly excited by the potential physics

00:48:36.820 | that suggests this kind of faster-than-light travel

00:48:40.860 | effectively or cutting the distance

00:48:44.060 | to make it very, very short through a wormhole

00:48:45.900 | or something like that.

00:48:47.860 | - Possible? No?

00:48:48.780 | - Well, call me not very imaginative,

00:48:51.100 | but based on today's knowledge of physics,

00:48:53.940 | which I realize people have gone down that rabbit hole.

00:48:56.780 | And a century ago, Lord Kelvin,

00:48:59.620 | one of the greatest physicists of all time,

00:49:01.540 | said that all of fundamental physics is done.

00:49:04.740 | The rest is just engineering.

00:49:06.140 | And guess what?

00:49:07.140 | Then came special relativity, quantum physics,

00:49:09.820 | general relativity, how wrong he was.

00:49:12.260 | So let me not be another Lord Kelvin.

00:49:14.980 | On the other hand, I think we know a lot more now

00:49:18.420 | about what we know and what we don't know

00:49:20.540 | and what the physical limitations are.

00:49:23.100 | And to me, most of these schemes, if not all of them,

00:49:26.620 | seem very far-fetched, if not impossible.

00:49:30.140 | So travel through wormholes, for example.

00:49:33.220 | You know, it appears that for a non-rotating black hole,

00:49:37.420 | that's just a complete no-go

00:49:39.620 | because the singularity is a point-like singularity

00:49:42.620 | and you have to reach it to traverse the wormhole

00:49:46.060 | and you get squished by the singularity, okay?

00:49:49.540 | Now, for a rotating black hole,

00:49:51.300 | it turns out there is a way to pass through

00:49:53.740 | the event horizon, the boundary of the black hole,

00:49:56.780 | and avoid the singularity and go out the other side

00:50:00.020 | or even traverse the donut hole-like singularity.

00:50:04.140 | In the case of a rotating black hole,

00:50:05.500 | it's a ring singularity.

00:50:06.780 | So there's actually two theoretical ways

00:50:08.860 | you could get through a rotating black hole

00:50:11.260 | or a charged black hole,

00:50:12.940 | not that we expect charged black holes to exist in nature

00:50:15.980 | because they would quickly bring in the opposite charge

00:50:19.060 | so as to neutralize themselves.

00:50:20.900 | But rotating black holes, definitely a reality.

00:50:23.340 | We now have good evidence for them.

00:50:25.580 | Do they have traversable wormholes?

00:50:28.620 | Probably not because it's still the case

00:50:31.220 | that when you go in, you go in with so much energy

00:50:34.860 | that it either squeezes the wormhole shut

00:50:39.460 | or you encounter a whole bunch of incoming

00:50:42.460 | and outgoing energy that vaporizes you.

00:50:46.020 | It's called the mass inflation instability

00:50:48.420 | and it just sort of vaporizes you.

00:50:50.780 | Nevertheless, you could imagine,

00:50:52.300 | well, you're in some vapor form,

00:50:53.740 | but if you make it through,

00:50:54.860 | maybe you could reform or something.

00:50:58.180 | - So it's still information.

00:50:59.380 | - Yeah, it's still information.

00:51:00.420 | It's scrambled information,

00:51:01.620 | but there's a way maybe of bringing it back, right?

00:51:04.420 | But then the thing that really bothers me

00:51:07.620 | is that as soon as you have this possibility

00:51:11.820 | of traversal of a wormhole,

00:51:13.780 | you have to come to grips with a fundamental problem.

00:51:16.500 | And that is that you could come back to your universe

00:51:20.300 | at a time prior to your leaving

00:51:23.500 | and you could essentially prevent your grandparents

00:51:26.260 | from ever meeting.

00:51:27.420 | This is called the grandfather paradox, right?

00:51:29.380 | And if they never met and if your parents were never born

00:51:31.940 | and if you were never born,

00:51:33.780 | how would you have made the journey

00:51:37.140 | to prevent the history from allowing you to exist, right?

00:51:42.140 | It's a violation of causality of cause and effect.

00:51:48.100 | Now, physicists such as myself

00:51:49.980 | take causality violation very, very seriously.

00:51:54.620 | We've never seen it.

00:51:55.620 | - You took a stand.

00:51:56.660 | - Yeah, I mean, it's one of these, right,

00:51:59.460 | back to the future type movies, right?

00:52:01.460 | And you have to work things out in such a way

00:52:04.020 | that you don't mess things up, right?

00:52:06.500 | Some people say that, well, you come back to the universe,

00:52:09.020 | but you come back in such a way

00:52:10.900 | that you cannot affect your journey.

00:52:13.980 | But then, I mean, that seems kind of contrived to me.

00:52:19.140 | Or some say that you end up in a different universe.

00:52:21.900 | And this also goes into the many different types

00:52:25.420 | of the multiverse hypothesis

00:52:27.020 | and the many worlds interpretation and all that.

00:52:29.220 | But again, then it's not the universe

00:52:31.500 | from which you left, right?

00:52:33.820 | And you don't come back to the universe from which you left.

00:52:36.980 | And so you're not really going back in time

00:52:40.420 | to the same universe.

00:52:42.060 | And you're not even going forward in time,

00:52:44.300 | necessarily, then, to the same universe, right?

00:52:46.580 | You're ending up in some other universe.

00:52:48.780 | So what have you achieved, right?

00:52:52.620 | - You've traveled. - You've traveled.

00:52:55.900 | - You ended up in a different place than you started.

00:52:59.180 | - Well- - In more ways than one.

00:53:00.780 | - Yeah, and then there's this idea,

00:53:03.100 | the Alcubierre drive,

00:53:04.500 | where you warp space-time in front of you

00:53:08.260 | so as to greatly reduce the distance

00:53:10.340 | and you can expand the space-time behind you.

00:53:12.700 | So you're sort of riding a wave through space-time.

00:53:15.980 | But the problem I see with that,

00:53:17.540 | beyond the practical difficulties

00:53:19.180 | and the energy requirements,

00:53:20.420 | and by the way, how do you get out of this bubble

00:53:23.380 | through which you're riding this wave of space-time?

00:53:26.540 | And Miguel Alcubierre acknowledged all these things.

00:53:29.140 | He said, "This is purely theoretical,

00:53:30.780 | "fanciful, and all that."

00:53:31.780 | But a fundamental problem I see

00:53:34.220 | is that you'd have to get to those places in front of you

00:53:38.300 | so as to change the shape of space-time

00:53:41.500 | so as to make the journey quickly.

00:53:43.620 | But to get there, you got there in the normal way

00:53:47.620 | at a speed considerably less than that of light.

00:53:50.620 | So in a sense, you haven't saved any time, right?

00:53:53.580 | You might as well have just taken that journey

00:53:56.340 | and gotten to where you were going.

00:53:59.300 | - Yeah, there's-- - Right?

00:54:00.540 | What have you done?

00:54:01.620 | It's not like you snap your fingers and say,

00:54:03.780 | "Okay, let that space there be compressed,

00:54:06.340 | "and then I'll make it over to Alpha Centauri

00:54:08.620 | "in the next month."

00:54:09.900 | You can't snap your fingers and do that.

00:54:12.420 | - Yeah, but we're sort of assuming

00:54:15.700 | that we can fix all the biological stuff

00:54:17.500 | that requires for humans to persist

00:54:19.580 | through that whole process,

00:54:22.180 | because ultimately, it might boil down

00:54:24.300 | to just extending the life of the human in some form,

00:54:27.980 | whether it's through the robot,

00:54:29.180 | through the digital form,

00:54:30.900 | or actually just figuring out genetically

00:54:33.300 | how to live forever.

00:54:34.460 | - That's right. - 'Cause that journey

00:54:35.700 | that you mentioned, the long journey,

00:54:37.540 | might be different if somehow our understanding of genetics,

00:54:42.540 | of our understanding of our own biology,

00:54:44.740 | all that kind of stuff would,

00:54:46.860 | that's another trajectory that would possibly--

00:54:48.700 | - If you could put us into some sort of suspended animation,

00:54:51.500 | you know, hibernation or something,

00:54:52.860 | and greatly increase the lifetime,

00:54:55.220 | and so these 10,000 generations I talked about,

00:54:57.740 | what do they care?

00:54:58.580 | It's just one generation, and they're asleep, okay?

00:55:01.700 | - Long nap. - So then you can do it.

00:55:04.340 | It's still not easy, right?

00:55:05.500 | 'Cause you've got some big old huge colony,

00:55:06.940 | and that just through E equals MC squared, right?

00:55:09.500 | That's a lot of mass, that's a lot of stuff to accelerate.

00:55:13.380 | The Newtonian kinetic energy is gigantic, right?

00:55:18.020 | So you're still not home free,

00:55:20.140 | but at least you're not trying to do it

00:55:22.100 | in a short amount of clock time, right?

00:55:26.060 | Which if you look at E equals MC squared,

00:55:28.420 | requires truly unfathomable amounts of energy,

00:55:32.220 | because the energy is sort of,

00:55:34.420 | it's your rest mass, M naught C squared,

00:55:37.540 | divided by the square root of one minus V squared

00:55:40.740 | over C squared.

00:55:41.980 | And if your listeners wanna just sort of

00:55:43.740 | stick into their pocket calculator,

00:55:45.700 | as V over C approaches one,

00:55:48.900 | that one over the square root of one minus V squared

00:55:51.500 | over C squared approaches infinity.

00:55:54.060 | So if you wanted to do it in zero time,

00:55:56.580 | you'd need an infinite amount of energy.

00:55:58.340 | That's basically why you can't reach,

00:56:01.140 | let alone exceed the speed of light

00:56:03.460 | for a particle moving through a preexisting space.

00:56:07.780 | It's that it takes an infinite amount of energy to do so.

00:56:11.540 | - So that's talking about us going somewhere.

00:56:14.900 | What about,

00:56:16.340 | one of the things that inspires a lot of folks,

00:56:20.580 | including myself, is the possibility that there's other,

00:56:23.980 | that this conversation is happening on another planet

00:56:27.460 | in different forms with intelligent life forms.

00:56:31.380 | Well, first we could start,

00:56:36.740 | as a cosmologist, what's your intuition about

00:56:41.380 | whether there is or isn't intelligent life out there,

00:56:44.820 | outside of our own?

00:56:45.900 | - Yeah, I would say I'm one of the pessimists

00:56:49.180 | in that I don't necessarily think that we're the only ones

00:56:52.180 | in the observable universe, which goes out

00:56:54.660 | roughly 14 billion years in light travel time

00:56:59.740 | and more like 46 billion years

00:57:01.980 | when you take into account the expansion of space.

00:57:04.180 | So the diameter of our observable universe

00:57:06.660 | is something like 90, 92 billion light years.

00:57:09.500 | That encompasses 100 billion to a trillion galaxies

00:57:14.500 | with 100 billion stars each.

00:57:17.180 | So now you're talking about something like 10 to the 22nd,

00:57:20.020 | 10 to the 23rd power stars

00:57:22.540 | and roughly an equal number of Earth-like planets and so on.

00:57:26.420 | So there may well be other intelligent life.

00:57:32.140 | - But your sense is our galaxy is not teeming with life.

00:57:35.140 | - Yeah, our galaxy, our Milky Way galaxy

00:57:37.180 | with several hundred billion stars

00:57:40.140 | and potentially habitable planets

00:57:42.020 | is not teeming with intelligent life.

00:57:44.100 | - Intelligent.

00:57:44.940 | - Yeah, I wouldn't, well, I'll get to the primitive life,

00:57:47.300 | the bacteria in a moment.

00:57:48.540 | But we may well be the only ones in our Milky Way galaxy

00:57:53.540 | at most a handful I'd say,

00:57:56.820 | but I'd probably side with the school of thought

00:58:00.940 | that suggests we're the only ones in our own galaxy

00:58:04.100 | just because I don't see human intelligence

00:58:08.540 | as being a natural evolutionary path for life.

00:58:13.540 | I mean, there's a number of arguments.

00:58:15.860 | First of all, there's been more than 10 billion species

00:58:18.660 | of life on Earth in its history.

00:58:21.700 | Nothing has approached our level of intelligence

00:58:25.140 | and mechanical ability and curiosity.

00:58:27.820 | Whales and dolphins appear to be reasonably intelligent,

00:58:30.700 | but there's no evidence that they can think abstract thoughts

00:58:34.060 | that they're curious about the world.

00:58:35.340 | They certainly can't build machines

00:58:37.260 | with which to study the world.

00:58:38.760 | So that's one argument.

00:58:40.900 | Secondly, we came about as early hominids

00:58:45.220 | only four or 5 million years ago,

00:58:47.340 | and as Homo sapiens only about a quarter

00:58:50.300 | of a million years ago.

00:58:52.020 | So for the vast majority of the history of life on Earth,

00:58:55.460 | an intelligent alien zipping by Earth would have said,

00:58:58.380 | there's nothing particularly intelligent

00:59:00.200 | or mechanically able on Earth, okay?

00:59:03.580 | Thirdly, it's not clear that our intelligence

00:59:07.520 | is a long-term evolutionary advantage.

00:59:10.700 | Now it's clear that in the last 100 years, 200 years,

00:59:13.460 | we've improved the lives of millions,

00:59:15.420 | hundreds of millions of people,

00:59:17.300 | but at the risk of potentially destroying ourselves,

00:59:20.940 | either intentionally or unintentionally

00:59:22.840 | or through neglect, as we discussed before.

00:59:26.100 | - That's a really interesting point,

00:59:28.560 | which is it's possible that there,

00:59:31.300 | a huge amount of intelligent civilizations

00:59:33.860 | have been born even through our galaxy,

00:59:36.180 | but they live very briefly and they die.

00:59:38.860 | - There are flash bulbs in the night.

00:59:40.700 | (laughing)

00:59:42.060 | - That brings me to the fourth issue,

00:59:45.540 | and that is the Fermi paradox.

00:59:47.860 | If they're common, where the hell are they?

00:59:50.560 | Notwithstanding the various UFO reports

00:59:54.540 | in Roswell and all that, they just don't meet the bar.

00:59:57.660 | They don't clear the bar of scientific evidence,

01:00:00.900 | in my opinion, okay?

01:00:02.560 | So there's no clear evidence

01:00:04.700 | that they've ever visited us on Earth here.

01:00:07.340 | So, and SETI has been now,

01:00:10.100 | the Search for Extraterrestrial Intelligence

01:00:12.140 | has been scanning the skies,

01:00:13.380 | and true, we've only looked a couple of hundred

01:00:15.340 | light years out, and that's a tiny fraction

01:00:17.380 | of the whole galaxy, a tiny fraction

01:00:19.520 | of these hundred billion plus stars.

01:00:21.940 | Nevertheless, you know,

01:00:23.620 | if the galaxy were teeming with life,

01:00:28.900 | especially intelligent life,

01:00:30.100 | you'd expect some of it to have been

01:00:32.420 | far more advanced than ours, okay?

01:00:34.680 | There's nothing special about

01:00:36.840 | when the Industrial Revolution started on Earth, right?

01:00:39.840 | The chemical evolution of our galaxy

01:00:41.700 | was such that billions of years ago,

01:00:44.500 | nuclear processing and stars had built up

01:00:47.560 | clouds of gas after their explosion

01:00:49.980 | that were rich enough in heavy elements

01:00:51.800 | to have formed Earth-like planets,

01:00:53.240 | even billions of years ago.

01:00:55.000 | So there could be civilizations

01:00:56.300 | that are billions of years ahead of ours.

01:00:58.860 | And if you look at the exponential growth of technology

01:01:01.980 | among Homo sapiens in the last couple of hundred years,

01:01:04.660 | and you just project that forward,

01:01:06.460 | I mean, there's no telling what they could have achieved

01:01:08.660 | even in 1,000 or 10,000 years,

01:01:11.380 | let alone a million or 10 million or a billion years.

01:01:15.060 | And if they reach this capability

01:01:17.900 | of interstellar travel and colonization,

01:01:20.500 | then you can show that within 10 million years

01:01:23.300 | or certainly a hundred million years,

01:01:25.140 | you can populate the whole galaxy, all right?

01:01:28.100 | And they, you know, so then you don't have to have

01:01:31.040 | tried to detect them beyond a hundred or a thousand

01:01:33.420 | light years, they would already be here.

01:01:35.420 | - Do you think, as a thought experiment,

01:01:38.140 | do you think it's possible that they are already here,

01:01:42.180 | but we humans are so human-centric

01:01:45.260 | that we're just not, like, our conception

01:01:47.500 | of what intelligent life looks like

01:01:49.300 | we don't want to acknowledge it.

01:01:53.620 | Like, what if trees?

01:01:55.340 | - Right, right, right, yeah.

01:01:57.900 | - Okay, I guess in the form of a question,

01:01:59.860 | do you think we'll actually detect intelligent life

01:02:03.020 | if it came to visit us?

01:02:04.500 | - Yeah, I mean, it's like, you know,

01:02:05.900 | you're an ant crawling around on a sidewalk somewhere

01:02:08.180 | and do you notice the humans wandering around

01:02:10.220 | and the Empire State Building and, you know,

01:02:12.900 | rocket ships flying to the moon and all that kind of stuff.

01:02:15.700 | Right, it's conceivable that we haven't detected it

01:02:19.740 | and that we're so primitive compared to them

01:02:21.740 | that we're just not able to do so.

01:02:23.460 | - Like if you look at dark energy, maybe,

01:02:26.020 | we call it as a field.

01:02:27.340 | - It's just that my own feeling is that in science now,

01:02:30.660 | through observations and experiments,

01:02:32.540 | we've measured so many things

01:02:35.420 | and basically we understand a lot of stuff.

01:02:40.020 | - The fabric of reality.

01:02:41.220 | - Yeah, the fabric of reality we understand quite well.

01:02:43.540 | And there are a few little things like dark matter

01:02:45.220 | and dark energy that may be some sign

01:02:47.580 | of some super intelligence, but I doubt it.

01:02:50.140 | Okay, you know, why would some super intelligence

01:02:51.940 | be holding clusters of galaxies together?

01:02:54.380 | Why would they be responsible

01:02:55.980 | for accelerating the expansion of the universe?

01:02:58.180 | So the point is that through science

01:03:01.540 | and applied science and engineering,

01:03:03.380 | we understand so much now

01:03:06.140 | that I'm not saying we know everything,

01:03:07.980 | but we know a hell of a lot, okay?

01:03:10.260 | And so it's not like there are lots of mysteries

01:03:13.820 | flying around there that are completely outside

01:03:17.300 | our level of exploration or understanding.

01:03:22.300 | - Yeah, I would say from the mystery perspective,

01:03:30.260 | it seems like the mystery of our own cognition

01:03:33.580 | and consciousness is much grander than,

01:03:36.700 | like the degrees of freedom of possible explanations

01:03:39.460 | for what the heck is going on is much greater there

01:03:41.500 | than in the physics of the observable.

01:03:44.420 | - How the brain works, how did life arise?

01:03:48.300 | Yeah, big, big questions.

01:03:50.380 | But they, to me, don't indicate the existence

01:03:54.460 | of an alien or something.

01:03:57.020 | I mean, unless we are the aliens,

01:03:58.540 | you know, we could have been contamination

01:04:00.180 | from some rocket ship that hit here a long, long time ago

01:04:03.980 | and all evidence of it has been destroyed.

01:04:06.020 | But again, that alien would have started out somewhere.

01:04:09.460 | They're not here watching us right now, right?

01:04:14.180 | They're not among us.

01:04:15.900 | And so though there are potential explanations

01:04:20.660 | for the Fermi paradox,

01:04:21.820 | and one of them that I kind of like

01:04:23.340 | is that the truly intelligent creatures

01:04:26.380 | are those that decided not to colonize the whole galaxy

01:04:30.060 | 'cause they'd quickly run out of room there

01:04:32.420 | 'cause it's exponential, right?

01:04:33.740 | You send a probe to a planet, it makes two copies.

01:04:37.300 | They go out, they make two copies each

01:04:39.820 | and it's an exponential, right?

01:04:41.300 | They quickly colonize the whole galaxy.

01:04:43.100 | But then the distance to the next galaxy,

01:04:45.500 | the next big one like Andromeda,

01:04:47.300 | that's two and a half million light years.

01:04:49.940 | That's a much grander scale now, right?

01:04:52.340 | And so it also could be that the reason they survived

01:04:56.100 | this long is that they got over this tendency

01:05:00.460 | that may well exist among sufficiently

01:05:03.260 | intelligent creatures,

01:05:04.660 | this tendency for aggression and self-destruction, right?

01:05:09.140 | If they bypass that, and that may be one

01:05:11.860 | of the great filters if there are more than one, right?

01:05:15.180 | Then they may not be a type of creature

01:05:18.700 | that feels the need to go and say,

01:05:21.540 | "Oh, there's a nice looking planet

01:05:23.900 | and there's a bunch of ants on it.

01:05:26.300 | Let's go squish 'em and colonize it."

01:05:28.860 | No, it could even be the kind of Star Trek

01:05:30.900 | like prime directive where you go and explore worlds

01:05:34.460 | but you don't interfere in any way, right?

01:05:37.860 | - And also we call it exploration,

01:05:40.820 | it's beautiful and everything,

01:05:42.140 | but there is underlying this desire to explore

01:05:45.700 | is a desire to conquer.

01:05:47.300 | I mean, if we're just being really honest about-

01:05:50.620 | - Right now for us it is, right?

01:05:52.620 | And you're saying it's possible to separate,

01:05:54.540 | but I would venture to say that those are coupled.

01:05:59.540 | So I could imagine a civilization that lives on

01:06:04.340 | for billions of years that just stays on,

01:06:07.460 | like figures out the minimal effort way

01:06:10.780 | of just peacefully existing.

01:06:12.380 | It's like a monastery.

01:06:13.860 | - Yeah, and it limits itself.

01:06:15.340 | - Yeah, it limits itself.

01:06:16.500 | - You know, it's planted its seeds in a number of places,

01:06:19.420 | so it's not vulnerable to a single point failure, right?

01:06:23.820 | Supernova going off near one of these stars or something

01:06:26.380 | or an asteroid or a comet coming in from the Oort cloud

01:06:30.260 | equivalent of that planetary system

01:06:32.100 | and without warning, thrashing them to bits.

01:06:35.140 | So they've got their seeds in a bunch of places,

01:06:37.100 | but they chose not to colonize the galaxy.

01:06:40.980 | And they also choose not to interfere

01:06:44.140 | with this incredibly primitive organism, Homo sapiens,

01:06:49.860 | right?

01:06:51.140 | - Or this is like a, they enjoy,

01:06:55.700 | this is like a TV show for them.

01:06:57.900 | - Yeah, it could be like a TV show, right?

01:07:00.420 | - So they just tuned in.

01:07:01.700 | - Right, so those are possible explanations.

01:07:04.020 | Yet, I think that to me, the most likely explanation

01:07:08.380 | for the Perimee paradox is that they really are

01:07:11.020 | very, very rare.

01:07:12.540 | And you know, Carl Sagan estimated 100,000 of them.

01:07:16.020 | If there's that many, some of them would have been

01:07:17.980 | way ahead of us and I think we would have seen them by now.

01:07:22.020 | If there are a handful, maybe they're there,

01:07:24.300 | but at that point, you're right on this dividing line

01:07:27.260 | between being a pessimist and an optimist.

01:07:29.980 | And what are the odds for that, right?

01:07:31.980 | If you look at all the things that had to go right for us.

01:07:35.420 | And then, you know, getting back to something

01:07:37.540 | you said earlier, let's discuss, you know, primitive life.

01:07:40.900 | That could be the thing that's difficult to achieve.

01:07:44.340 | Just getting the random molecules together

01:07:47.220 | to a point where they start self-replicating

01:07:50.220 | and evolving and becoming better and all that.

01:07:53.460 | That's an inordinately difficult thing, I think,

01:07:56.500 | though I'm not, you know, some molecular or cell biologist,

01:07:59.300 | but just, it's the usual argument, you know,

01:08:02.140 | you're wandering around in the Sahara Desert

01:08:04.300 | and you stumble across a watch.

01:08:06.540 | Is your initial response, oh, you know,

01:08:10.820 | a bunch of sand grains just came together randomly

01:08:13.420 | and formed this watch.

01:08:14.500 | No, you think that something formed it

01:08:17.380 | or it came from some simpler structure

01:08:21.100 | that then became, you know, more complex.

01:08:23.940 | All right, it didn't just form.

01:08:26.020 | Well, even the simplest life

01:08:28.940 | is a very, very complex structure.

01:08:31.860 | Even the simplest prokaryotic cells,

01:08:34.820 | not to mention eukaryotic cells,

01:08:36.500 | although that transition may have been

01:08:38.580 | the so-called great filter as well.

01:08:40.340 | Maybe the cells without a nucleus

01:08:42.860 | are relatively easy to form.

01:08:45.020 | And then the big next step is where you have a nucleus,

01:08:48.420 | which then provides a lot of energy,

01:08:50.180 | which allows the cell to become much, much more complex

01:08:53.060 | and so on.

01:08:54.140 | Interestingly, going from eukaryotic cells, single cells,

01:08:58.740 | to multicellular organisms does not appear to be,

01:09:02.740 | at least on earth, one of these great filters

01:09:04.500 | because there's evidence that it happened dozens of times

01:09:07.460 | independently on earth.

01:09:08.900 | So by a really great filter,

01:09:11.940 | something that happens very, very rarely,

01:09:13.860 | I mean that we had to get through

01:09:16.540 | an obstacle that is just incredibly rare to get through.

01:09:24.140 | - And one of the really exciting scientific things

01:09:27.660 | is that that particular point

01:09:29.500 | is something that we might be able to discover,

01:09:33.500 | even in our lifetimes, that find life elsewhere,

01:09:36.940 | like Europa or be able to--

01:09:39.460 | - See, that would be bad news, right?

01:09:41.780 | (laughing)

01:09:42.740 | 'Cause if we find lots of pretty advanced life,

01:09:46.500 | that would suggest, and especially if we found

01:09:50.220 | some defunct fossilized civilization

01:09:52.860 | or something somewhere else, that would be--

01:09:54.940 | - Oh, bacteria, you mean.

01:09:56.340 | - What's that?

01:09:57.180 | - Defunct civilization of like primitive life forms.

01:09:59.980 | - Oh, no, I'm sorry, I switched gears there.

01:10:01.220 | If we found some intelligent or even trilobites, right,

01:10:05.220 | and stuff, you know, elsewhere,

01:10:06.740 | that would be bad news for us because that would mean

01:10:08.740 | that the great filter is ahead of us, you know, right?

01:10:11.620 | - Oh, interesting, yeah.

01:10:12.460 | - Because it would mean that lots of things

01:10:15.580 | have gotten roughly to our level.

01:10:17.460 | - Yeah.

01:10:18.300 | - But given the Fermi paradox,

01:10:20.460 | if you accept that the Fermi paradox means

01:10:23.140 | that there's no one else out there,

01:10:24.580 | you don't necessarily have to accept that,

01:10:26.220 | but if you accept that it means that no one else

01:10:28.940 | is out there, and yet there are lots of things we've found

01:10:31.900 | that are at or roughly at our level,

01:10:34.460 | that means that the great filter is ahead of us

01:10:36.660 | and that bodes poorly for our long-term future.

01:10:40.860 | You know, but--

01:10:41.700 | - Yeah, it's funny you said, you started by saying

01:10:45.700 | you're a little bit on the pessimistic side,

01:10:48.020 | but it's funny because we're doing this kind of dance

01:10:51.420 | between pessimism and optimism because I'm not sure

01:10:54.360 | if us being alone in the observable universe

01:10:57.340 | as intelligent beings is pessimistic.

01:11:00.020 | - Well, it's good news in a sense for us

01:11:02.760 | because it means that we made it through.

01:11:06.020 | - Oh, right.

01:11:06.860 | - See, if we're the only ones,

01:11:09.260 | and there are such great filters, maybe more than one,

01:11:12.540 | formation of life might be one of them,

01:11:14.660 | formation of eukaryotic that is with the nucleus cells

01:11:18.260 | be another, development of human-like intelligence

01:11:21.860 | might be another, right?

01:11:22.980 | There might be several such filters

01:11:25.700 | and we were the lucky ones.

01:11:27.620 | And, you know, then people say, well, then that means

01:11:29.700 | you're putting yourself into a special perspective

01:11:32.260 | and every time we've done that, we've been wrong.

01:11:34.540 | And yeah, yeah, I know all those arguments,

01:11:36.300 | but it still could be the case that there's one of us,

01:11:40.380 | at least per galaxy or per 10 or a hundred

01:11:42.580 | or a thousand galaxies, and we're sitting here

01:11:46.060 | having this conversation because we exist.

01:11:48.940 | And so there's an observational selection effect there.

01:11:52.980 | Just because we're special doesn't mean

01:11:54.560 | that we shouldn't have these conversations

01:11:56.740 | about whether or not we're special, right?

01:11:59.280 | - Yeah, so that's exciting.

01:12:01.940 | That's optimistic.

01:12:03.260 | - So that's the optimistic part

01:12:05.700 | that if we don't find other intelligent life there,

01:12:08.780 | it might mean that we're the ones that made it.

01:12:12.040 | - And in general, outside the great filter and so on,

01:12:16.380 | you know, it's not obvious that the Stephen Hawking thing,

01:12:20.060 | which is, it's not obvious that life out there

01:12:22.700 | is gonna be kind to us.

01:12:24.380 | - Oh yeah.

01:12:26.500 | So, you know, I knew Hawking and I greatly respect

01:12:29.740 | his scientific work and in particular,

01:12:33.020 | the early work on the unification of general theory

01:12:36.580 | of relativity and quantum physics,

01:12:38.380 | two great pillars in modern physics,

01:12:40.140 | you know, Hawking radiation and all that, fantastic work.

01:12:42.740 | You know, if you were alive,

01:12:44.580 | you should have been a recipient

01:12:45.860 | of this year's physics Nobel prize,

01:12:47.740 | which was for the discovery of black holes

01:12:49.980 | and also by Roger Penrose for the theoretical work

01:12:53.700 | showing that given a star that's massive enough,

01:12:58.180 | you basically can't avoid having a black hole.

01:13:00.700 | Anyway, Hawking, fantastic.

01:13:02.940 | I tip my hat to him.

01:13:04.380 | May he rest in peace.

01:13:05.500 | - That would have been a heck of a Nobel prize,

01:13:07.660 | black holes.

01:13:08.500 | - Yeah, yeah, yeah.

01:13:09.340 | - Heck of a good group.

01:13:10.820 | - But going back to what he said,

01:13:12.220 | that we shouldn't be broadcasting our presence to others,

01:13:16.340 | there I actually disagree with him respectfully

01:13:18.780 | because first of all,

01:13:21.100 | we've been unintentionally broadcasting our presence

01:13:23.780 | for a hundred years since the development of radio and TV.

01:13:28.260 | Secondly, any alien that has the capability

01:13:32.100 | of coming here and squashing us,

01:13:34.980 | either already knows about us and, you know, doesn't care

01:13:38.300 | 'cause we're just like little ants.

01:13:39.820 | And when there are ants in your kitchen,

01:13:41.820 | you tend to squash them.

01:13:42.860 | But if there are ants on the sidewalk and you're walking by,

01:13:45.980 | do you feel some great conviction

01:13:48.060 | that you have to squash any of them?

01:13:49.820 | No, you generally don't, right?

01:13:51.420 | We're irrelevant to them.

01:13:52.940 | All they need to do is keep an eye on us

01:13:55.860 | to see whether we're approaching

01:13:57.500 | the kind of technological capability

01:13:59.740 | and know about them and have intentions of attacking them.

01:14:04.700 | And then they can squash us, right?

01:14:06.780 | You know, they could have done it long ago.

01:14:11.460 | They'll do it if they want to.

01:14:13.300 | Whether we advertise our presence or not is irrelevant.

01:14:17.100 | So I really think that that's not a huge existential threat.

01:14:21.620 | - So this is a good place to bring up a difficult topic.

01:14:24.940 | You mentioned they would be paying attention to us

01:14:29.940 | to see if we come up with any crazy technology.

01:14:32.980 | There's folks who have reported UFO sightings.

01:14:37.740 | There's actually, I've recently found out

01:14:39.380 | there's websites that track this,

01:14:42.060 | the data of these reportings.

01:14:44.060 | And there's millions of them in the past several decades,

01:14:49.060 | so seven decades and so on, that they've been recorded.

01:14:54.300 | And the UFOlogist community, as they refer to themselves,

01:14:59.300 | you know, one of the ideas that I find compelling

01:15:04.500 | from an alien perspective,

01:15:06.260 | that they kind of started showing up

01:15:09.460 | ever since we figured out how to build nuclear weapons.

01:15:12.680 | That was sure. (laughs)

01:15:14.660 | - What a coincidence.

01:15:15.700 | - Yeah.

01:15:17.100 | So I mean, you know, if I was an alien,

01:15:19.060 | I would start showing up then as well.

01:15:21.660 | - Well, why not just observe us from afar?

01:15:23.340 | - No, I know, right.

01:15:24.340 | I would figure out, but that's why I'm always

01:15:27.860 | keeping a distance and staying blurry.

01:15:29.820 | - Right. (laughs)

01:15:32.460 | Very pixelated.

01:15:33.340 | - Very pixelated.

01:15:34.460 | You know, there is something in the human condition,

01:15:37.500 | a cognition that wants to see,

01:15:40.540 | wants to believe beautiful things.

01:15:42.340 | And some are terrifying, some are exciting.

01:15:45.620 | Goats, Bigfoot is a big fascination for folks.

01:15:51.460 | And UFO sightings, I think, falls into that.

01:15:53.940 | There's people that look at lights in the night sky.

01:15:57.140 | I mean, it's kind of a downer to think in a skeptical sense,

01:16:04.620 | to think that's just a light.

01:16:07.900 | - Yeah.

01:16:08.740 | - You want to feel like there's something magical there.

01:16:10.940 | - Sure.

01:16:11.820 | - I mean, I felt that first when my dad,

01:16:13.700 | my dad's a physicist,

01:16:15.260 | when he first told me about ball lightning

01:16:18.420 | when I was like a little kid.

01:16:19.260 | - Very weird.

01:16:20.100 | - Very, like--

01:16:20.940 | - Yeah.

01:16:21.780 | - Weird physical phenomena.

01:16:22.620 | - Yeah.

01:16:23.460 | - And he said, his intuition was,

01:16:26.420 | tell me this as a little kid,

01:16:28.060 | like I really like math.

01:16:30.500 | His intuition was whoever figures out ball lightning

01:16:33.300 | will get a Nobel Prize.

01:16:34.660 | I think that was a side comment he gave me.

01:16:38.140 | I decided there when I was like five years old or whatever

01:16:41.220 | that I'm going to win a Nobel Prize

01:16:43.220 | for figuring out ball lightning.

01:16:44.060 | - Figuring out ball lightning.

01:16:44.900 | - That was like one of the first sort of sparks

01:16:47.060 | of the scientific mindset.

01:16:48.980 | Those mysteries, they capture your imagination.

01:16:51.340 | - Yeah.

01:16:52.180 | - I think when I speak to people that report UFOs,

01:16:54.980 | that's that fire, that's what I see, that excitement.

01:16:58.460 | - Sure, and I understand that.

01:16:59.940 | - But what do we do with that?

01:17:02.780 | Because there's hundreds of thousands, if not millions,

01:17:06.260 | and then the scientific community,

01:17:08.020 | you're like the perfect person.

01:17:09.380 | You have an awesome Einstein shirt.

01:17:12.940 | What do we do with those reports?

01:17:17.620 | Most of the scientific community kind of rolls their eyes

01:17:20.140 | and dismisses it.

01:17:21.340 | Is it possible that a tiny percent of those folks

01:17:26.340 | saw something that's worth deeply investigating?

01:17:30.620 | - Sure, we should investigate it.

01:17:32.460 | It's just one of these things where,

01:17:34.780 | they've not brought us a hunk of kryptonite

01:17:37.020 | or something like that, right?

01:17:38.300 | They haven't brought us actual, tangible, physical evidence

01:17:42.540 | with which experiments can be done in laboratories.

01:17:45.500 | - Right.

01:17:46.540 | - It's anecdotal evidence.

01:17:48.060 | The photographs are, in some cases,

01:17:51.380 | in most cases, I would say, quite ambiguous.

01:17:54.340 | - I don't know what to think about.

01:17:55.820 | So David Fravor is the first person.

01:17:57.780 | He's a Navy pilot, commander, and there's a bunch of them,

01:18:01.060 | but he's sort of one of the most legit pilots

01:18:04.980 | and people I've ever met.

01:18:08.180 | - Right.

01:18:09.020 | - The fact that he saw something weird,

01:18:11.100 | he doesn't know what the heck it is,

01:18:13.540 | but he saw something weird.

01:18:14.660 | I mean, I don't know what to do with that.

01:18:16.780 | And on the psychological side,

01:18:20.220 | so I'm pretty confident he saw what he says he saw,

01:18:23.940 | which he's saying is something weird.

01:18:27.020 | - Right.

01:18:27.860 | - One of the interesting psychological things

01:18:31.260 | that worries me is that everybody in the Navy,

01:18:36.260 | everybody in the US government,

01:18:38.020 | everybody in the scientific community

01:18:40.460 | just kind of like pretended that nothing happened.

01:18:44.700 | That kind of instinct,

01:18:47.060 | that's what makes me believe if aliens show up,

01:18:49.060 | we would all just ignore their presence.

01:18:52.780 | That's what bothered me,

01:18:54.100 | that you don't investigate it more carefully

01:18:59.100 | and use this opportunity to inspire the world.

01:19:02.260 | So in terms of kryptonite,

01:19:06.780 | I think the conspiracy theory folks

01:19:10.180 | say that whenever there is some good hard evidence

01:19:13.620 | that scientists would be excited about,

01:19:16.260 | there's this kind of conspiracy that I don't like

01:19:18.540 | 'cause it's ultimately negative,

01:19:20.220 | that the US government will somehow hide the good evidence

01:19:23.660 | to protect it.

01:19:26.260 | Of course, there's some legitimacy to it

01:19:28.100 | 'cause you wanna protect military secrets,

01:19:32.100 | all that kind of stuff,

01:19:32.940 | but I don't know what to do with this beautiful mess

01:19:38.300 | because I think millions of people are inspired by UFOs

01:19:43.300 | and it feels like an opportunity

01:19:46.260 | to inspire people about science.

01:19:47.740 | - So I would say, as Carl Sagan used to say,

01:19:50.500 | "Extraordinary claims require extraordinary evidence."

01:19:54.220 | I've quoted him a number of times.

01:19:56.540 | We would welcome such evidence.

01:20:02.060 | On the other hand, a lot of the things that are seen

01:20:06.300 | or perhaps even hidden from us,

01:20:08.820 | you could imagine for military purposes,

01:20:12.060 | surveillance purposes,

01:20:13.860 | the US government doesn't want us to know,

01:20:16.260 | or maybe some of these pilots saw Soviet or Israeli

01:20:19.940 | or whatever satellites, right?

01:20:22.980 | A lot of the, or some of the crashes that have occurred

01:20:26.260 | were later found to be weather balloons or whatever.

01:20:30.020 | When there are more conventional explanations,

01:20:34.220 | science tends to stay away from the sensational ones, right?

01:20:39.220 | And so it may be that someone else's calling in life

01:20:46.340 | is to investigate these phenomena.

01:20:48.820 | And I welcome that as a scientist.

01:20:51.660 | I don't categorically actually deny the possibility

01:20:55.620 | that ships of some sort could have visited us

01:20:58.620 | because as I said earlier, at slow speeds,

01:21:01.980 | there's no problem in reaching other stars.

01:21:04.220 | In fact, our Voyager and Pioneer spacecraft

01:21:06.860 | in a few million years are gonna be in the vicinity

01:21:10.020 | of different stars.

01:21:10.940 | We can even calculate which ones they're gonna be

01:21:12.980 | in the vicinity of, right?

01:21:15.140 | So there's nothing that breaks any laws of physics

01:21:17.940 | if you do it slowly, but that's different.

01:21:20.540 | Just having Voyager or Pioneer fly by some star,

01:21:23.780 | that's different from having active aliens

01:21:26.500 | altering the trajectory of their vehicle

01:21:29.540 | in real time spying on us.

01:21:31.620 | And then either zipping back to their home planet

01:21:35.020 | or sending signals that tell them about us

01:21:38.620 | because they are likely many light years away

01:21:43.180 | and they're not gonna have broken that barrier as well.

01:21:47.020 | Okay, right?

01:21:48.060 | So I just, you know, go ahead, study them.

01:21:53.060 | Great.

01:21:55.300 | For some young kid who wants to do it,

01:21:57.660 | it might be their calling

01:21:59.060 | and that's how they might find meaning in their lives

01:22:02.140 | is to be the scientist who really explores these things.

01:22:06.060 | I chose not to because at a very young age,

01:22:09.180 | I found the evidence to the degree that I investigated it

01:22:12.820 | to be really quite unconvincing

01:22:14.980 | and I had other things that I wanted to do.

01:22:18.260 | But I don't categorically deny the possibility

01:22:21.380 | and I think it should be investigated.

01:22:24.020 | - Yeah, I mean, this is one of those phenomena

01:22:26.940 | that 99.9% of people are almost definitely,

01:22:31.660 | there's conventional explanations

01:22:34.260 | and then there's like mysterious things

01:22:36.220 | that probably have explanations

01:22:40.500 | that are a little bit more complicated.

01:22:42.460 | - Yeah.

01:22:43.300 | - But there's not enough to work with.

01:22:45.500 | I tend to believe that if aliens showed up,

01:22:48.980 | there'll be plenty of evidence for scientists to study.

01:22:53.260 | - Yeah.

01:22:54.180 | And exactly as you said,

01:22:57.620 | avoid your type of spacecraft.

01:23:00.500 | I could see sort of some kind of a dumb thing,

01:23:05.500 | almost like a sensor that's like probing,

01:23:08.020 | like statistically speaking. - Flying by.

01:23:09.500 | - Flying by, maybe lands,

01:23:11.460 | maybe there's some kind of robot type of thingies

01:23:13.420 | that just like move around and so on.

01:23:15.060 | - Yeah.

01:23:15.900 | - Like in ways that we don't understand.

01:23:17.700 | But I feel like, well,

01:23:21.340 | I feel like there'll be plenty of hard to dismiss evidence.

01:23:26.340 | And I also, especially this year,

01:23:30.020 | believe that the US government is not sufficiently competent

01:23:35.020 | given the huge amount of evidence

01:23:37.220 | that will be revealed from this kind of thing

01:23:39.500 | to conceal all of it.

01:23:41.220 | - Right.

01:23:42.060 | - At least in modern times,

01:23:43.060 | you can say maybe decades ago, but in modern times.

01:23:46.580 | But the people I speak to,

01:23:49.180 | and the reason I bring it up

01:23:50.340 | is because so many people write to me,

01:23:52.220 | they're inspired by it.

01:23:53.540 | - By the way, I wanted to comment

01:23:54.660 | on something you said earlier.

01:23:56.380 | Yeah, I had said that I'm sort of a pessimist

01:23:59.340 | in that I think there are very few other intelligent,

01:24:03.140 | mechanically able creatures out there.

01:24:06.020 | But then I said, yes, in a sense, I'm an optimist,

01:24:09.140 | as you pointed out,

01:24:09.980 | because it means that we made it through the great filter.

01:24:13.020 | Right.

01:24:13.860 | I meant originally that I'm a pessimist

01:24:16.100 | in that I'm pessimistic about the possibility

01:24:19.580 | that there are many, many of us out there.

01:24:21.860 | - You know, mathematically speaking,

01:24:23.420 | in the Drake equation.

01:24:24.540 | - Exactly, right, right.

01:24:25.860 | But it may mean a good thing for our ultimate survival.

01:24:29.220 | Right, so I'm glad you caught me on that.

01:24:30.660 | - Yeah, I definitely agree with you.

01:24:32.380 | It is ultimately an optimist statement.

01:24:33.980 | - But anyway, I think UFO research is interesting.

01:24:38.020 | And I guess one of the reasons

01:24:40.460 | I've not been terribly convinced

01:24:42.340 | is that I think there are some scientists

01:24:44.460 | who are investigating this,

01:24:46.100 | and they've not found any clear evidence.

01:24:48.940 | Now, I must admit, I have not looked through the literature

01:24:52.660 | to convince myself that there are many scientists

01:24:55.060 | doing systematic studies of these various reports.

01:24:58.020 | I can't say for sure that there's a critical mass of them.

01:25:01.940 | - Well, the one-

01:25:02.780 | - But it's just that you never get these reports

01:25:04.700 | from hardcore scientists.

01:25:06.460 | That's the other thing.

01:25:07.300 | And astronomers, you know, what do we do?

01:25:08.660 | We spend our time studying the heavens,

01:25:10.780 | and you'd think we'd be the ones that are most likely,

01:25:13.700 | aside from pilots, perhaps,

01:25:15.380 | at seeing weird things in the sky.

01:25:17.300 | And we just never do, of the unexplained UFO-type nature.

01:25:22.300 | - Yeah, I definitely, I try to keep an open mind,

01:25:25.020 | but for people who listen,

01:25:26.420 | it's actually really difficult for scientists.

01:25:30.620 | Like, I get probably, like this year,

01:25:34.060 | I've probably gotten over,

01:25:36.020 | probably maybe over 1,000 emails on the topic of AGI.

01:25:41.020 | It's very difficult to, you know,

01:25:45.580 | people write to me, it's like, how can you ignore this,

01:25:48.780 | in AGI side, like this model?

01:25:50.540 | This is obviously the model

01:25:51.860 | that's going to achieve general intelligence.

01:25:53.780 | How can you ignore it?

01:25:54.700 | I'm giving you the answer.

01:25:55.740 | Here's my document.

01:25:56.740 | And there's always just these large write-ups.

01:26:00.500 | The problem is, it's very difficult

01:26:03.460 | to weed through a bunch of BS.

01:26:07.060 | - Right.

01:26:07.900 | - It's very possible that you actually saw the UFO,

01:26:12.420 | but you have to acknowledge that,

01:26:14.980 | by UFO, I mean an extraterrestrial life,

01:26:17.540 | you have to acknowledge the hundreds of thousands of people

01:26:21.820 | who are a little bit, if not a lot, full of BS.

01:26:26.420 | And from a scientist's perspective,

01:26:28.780 | it's really hard work.

01:26:30.820 | And when there's amazing stuff out there,

01:26:34.020 | it's like, why invest in Bigfoot

01:26:36.540 | when evolution in all of its richness is beautiful?

01:26:40.180 | Who cares about a monkey that walks on two feet,

01:26:42.500 | or eight, or whatever?

01:26:43.340 | - In a sense, it's like there's a zillion decoys.

01:26:44.900 | - Yeah.

01:26:45.740 | - At observatories, true fact,

01:26:48.820 | we get lots and lots of phone calls

01:26:51.740 | when Venus, the evening star,

01:26:54.020 | but just really a bright planet,

01:26:55.980 | happens to be close to the crescent moon,

01:26:58.380 | because it's such a striking pair.

01:27:00.300 | This happens once in a while.

01:27:01.340 | So we get these phone calls,

01:27:02.260 | oh, there's a UFO next to the moon.

01:27:04.540 | And no, it's Venus.

01:27:06.260 | And so, they're just,

01:27:07.940 | and I'm not saying the best UFO reports are of that nature.

01:27:12.500 | No, there's some much more convincing cases,

01:27:14.380 | and I've seen some of the footage, and blah, blah, blah.

01:27:17.100 | But it's just, there's so many decoys, right?

01:27:19.500 | So much noise that you have to filter out.

01:27:22.580 | - And there's only so many scientists, so it's hard.

01:27:24.420 | - There's only so much time as well,

01:27:27.380 | and you have to choose what problems you work on.

01:27:30.060 | - This might be a fun question to ask,

01:27:33.220 | to kind of explore the idea of the expanding universe.

01:27:38.220 | So, the radius of the observable universe

01:27:42.860 | is 45.7 billion light years.

01:27:47.580 | And the age of the universe is 13.7 billion years.

01:27:52.580 | That's less than the radius of the universe.

01:27:59.700 | How's that possible?

01:28:01.580 | - So, that's a great question.

01:28:03.420 | So, I meant to bring a little prop I have

01:28:06.700 | with ping pong balls and a rubber hose, a rubber band.

01:28:09.420 | I use it in many of the lectures

01:28:11.780 | that one can find of me online.

01:28:14.460 | But you have, in an expanding universe,

01:28:16.540 | the space itself between galaxies,

01:28:18.900 | or more correctly, clusters of galaxies, expanding.

01:28:22.860 | So, imagine light going from one cluster to another.

01:28:26.980 | It traverses some distance,

01:28:29.180 | and then while it's traversing the rest,

01:28:32.300 | that part that it already traveled through

01:28:36.060 | continues to expand.

01:28:38.340 | Now, 13.7 billion years might have gone by

01:28:43.340 | since the light that we are seeing from the early stages,

01:28:48.060 | the so-called cosmic microwave background radiation,

01:28:50.620 | which is the afterglow of the Big Bang,

01:28:53.260 | or the echo of the Big Bang.

01:28:54.660 | Yeah, 13.7 billion years have gone by.

01:28:57.220 | That's how long it's taken that light to reach us.

01:29:00.700 | But while it's been traveling that distance,

01:29:03.300 | the parts that it already traveled continue to expand.

01:29:07.900 | So, it's like you're walking at an airport

01:29:11.300 | on one of these walkways,

01:29:13.060 | and you're walking along

01:29:14.140 | 'cause you're trying to get to your terminal,

01:29:16.100 | but the walkway is continuing as well.

01:29:19.140 | You end up traveling a greater distance,

01:29:21.740 | or the same distance faster

01:29:23.260 | is another way of putting it, right?

01:29:25.140 | That's why you get on one of these traveling walkways.

01:29:28.340 | So, you get roughly a factor of pi,

01:29:31.820 | but it's more like 3.2, I think.

01:29:33.460 | But when you work it all out,

01:29:35.620 | you multiply the number of years

01:29:37.980 | the universe has been in existence

01:29:40.060 | by three and a quarter or so,

01:29:42.420 | and that's how you get this 46 billion light year radius.

01:29:47.380 | - But how is that, let me ask some nice dumb questions.

01:29:53.220 | How is that not traveling faster than the speed of light?

01:29:57.140 | - Yeah, it's not traveling faster than the speed of light

01:29:59.060 | because locally, at any point,

01:30:01.140 | if you were to measure the light,

01:30:03.340 | the photon zipping past,

01:30:05.420 | it would not be exceeding the speed of light.

01:30:07.980 | The speed of light is a locally measured quantity.

01:30:10.980 | After light has traversed some distance,

01:30:13.300 | if the rubber band keeps on stretching,

01:30:16.100 | then yes, it looks like the light traveled

01:30:19.380 | a greater distance than it would have

01:30:21.980 | had the space not been expanding.

01:30:25.140 | But locally, it never was exceeding the speed of light.

01:30:28.180 | It's just that the distance

01:30:29.300 | through which it already traveled

01:30:31.020 | then went off and expanded on its own some more.

01:30:35.180 | And if you give the light credit, so to speak,

01:30:38.820 | for having traversed that distance,

01:30:40.740 | well, then it looks like it's going faster

01:30:42.780 | than the speed of light.

01:30:43.620 | - But that's not how speed works.

01:30:46.220 | - Right, that's not how speed works.

01:30:47.420 | Speed, and in relativity also,

01:30:49.860 | the other thing that is interesting is that,

01:30:53.380 | you know, if you take two ping pong balls

01:30:55.300 | that are sufficiently far apart,

01:30:56.620 | especially in an accelerating universe,

01:30:59.180 | you can easily have them moving apart from one another

01:31:01.540 | faster than the speed of light.

01:31:03.300 | So, you know, take two ping pong balls

01:31:05.420 | that were originally 400,000 kilometers from each other

01:31:09.180 | and let every centimeter in your rubber band

01:31:11.660 | expand to two in one second.

01:31:14.220 | Then suddenly this 400,000 kilometer distance

01:31:17.580 | is 800,000 kilometers.

01:31:19.780 | It went out by 400,000 kilometers in one second,

01:31:24.340 | that exceeds the 300,000 kilometer per second

01:31:28.100 | speed of light.

01:31:29.540 | But that light limit, that particle limit

01:31:32.860 | in special relativity applies to objects

01:31:36.340 | moving through a preexisting space.

01:31:39.500 | There's nothing in either special or general relativity

01:31:43.020 | that prevents space itself from expanding faster

01:31:47.260 | than the speed of light.

01:31:48.540 | That's no problem.

01:31:49.380 | Einstein wouldn't have had a problem with a universe

01:31:53.740 | as observed now by cosmologists.

01:31:56.300 | - Yeah, I'm not sure I'm yet ready to deal emotionally

01:32:00.700 | with expanding space.

01:32:02.980 | - Ha ha.

01:32:03.820 | - It's like, that to me is one of the most awe-inspiring

01:32:06.360 | things, you know, starting from the Big Bang.

01:32:09.460 | - It's definitely abstract.

01:32:10.860 | - It's space itself is expanding.

01:32:13.580 | - Right.

01:32:15.180 | - Could you, can we talk about the Big Bang a little bit?

01:32:18.340 | - Sure, yeah, yeah.

01:32:19.660 | - So like, the entirety of it,

01:32:24.740 | the universe was very small.

01:32:27.660 | - Right, but it was not a point.

01:32:29.660 | - It was not a point.

01:32:30.860 | - Because if we live in what's called a closed universe now,

01:32:34.300 | a sphere or the three-dimensional version of that

01:32:36.780 | would be a hypersphere, you know.

01:32:39.900 | Then regardless of how far back in time you go,

01:32:43.060 | it was always that topological shape.

01:32:45.820 | You can't turn a point suddenly into a shell, okay?

01:32:49.260 | It always had to be a shell.

01:32:51.780 | So when people say, well, the universe started out

01:32:54.860 | as a point, that's being kind of flippant, kind of glib.

01:32:57.940 | It didn't really, it just started out

01:33:00.060 | at a very high density.

01:33:02.060 | And we don't know actually whether it was finite

01:33:04.660 | or infinite.

01:33:05.720 | I think personally that it was finite at the time,

01:33:08.380 | but it expanded very, very quickly.

01:33:10.280 | Indeed, if it exponentiated and continued in some places

01:33:14.500 | to exponentiate, then it could in fact be infinite

01:33:17.540 | right now, and most cosmologists think that it is infinite.

01:33:20.540 | - Wait, yeah, sorry, what infinite, which dimension, mass?

01:33:24.740 | - Infinite in space, infinite in space.

01:33:26.940 | And by that I mean that if you were trying to measure,

01:33:30.220 | use light to measure its size,

01:33:32.760 | you'd never be able to measure its size

01:33:35.000 | 'cause it would always be bigger

01:33:36.700 | than the distance light can travel.

01:33:39.060 | That's what you get in a universe

01:33:40.660 | that's accelerating in its expansion.

01:33:43.060 | - Okay, but if a thing was a hypersphere,

01:33:46.780 | it's very small, not a point.

01:33:49.220 | How can that thing be infinite?

01:33:51.060 | - Well, it expands exponentially.

01:33:53.860 | That's what the inflation theory is all about.

01:33:56.140 | Indeed, at your home institution,

01:33:57.820 | Alan Guth is one of the originators

01:34:00.320 | of the whole inflationary universe idea,

01:34:02.860 | along with Andre Linde at Stanford University

01:34:05.740 | here in the Bay Area, and others,

01:34:07.700 | Alexei Starobinsky and others had similar sorts of ideas.

01:34:11.140 | But in an exponentially expanding universe,

01:34:14.580 | if you actually try to make this measurement,

01:34:17.160 | you send light out to try to see it curve back around

01:34:21.140 | and hit you in the back of the head.

01:34:23.100 | If it's an exponentially expanding universe,

01:34:25.640 | the amount of space remaining to be traversed

01:34:29.400 | is always a bigger and bigger quantity.

01:34:32.280 | So you'll never get there from here.

01:34:33.640 | You'll never reach the back of your head.

01:34:35.840 | So observationally or operationally,

01:34:38.480 | it can be thought of as being infinite.

01:34:41.020 | - That's one of the best definitions of infinity,

01:34:43.040 | by the way. - What's that?

01:34:44.240 | - That's one of the best sort of physical manifestations

01:34:49.000 | of infinity.

01:34:50.120 | - Yeah, yeah, because you have to ask,

01:34:51.480 | how would you actually measure it?

01:34:53.320 | Now, I sometimes say to my cosmology theoretical friends,

01:34:56.280 | well, if I were God and I were outside this whole thing

01:34:59.880 | and I took a God-like slice in time,

01:35:03.320 | wouldn't it be finite no matter how big it is?

01:35:05.840 | And they object and they say, Alex,

01:35:07.760 | you can't be outside and take a God-like slice of time.

01:35:13.600 | - Because there's nothing outside.

01:35:14.880 | - Well, I'm not, you know, or also,

01:35:19.320 | what slice of time you're taking depends on your motion.

01:35:22.800 | And that's true even in special relativity

01:35:24.740 | that slices of time get tilted in a sense

01:35:28.560 | if you're moving quickly.

01:35:30.080 | The axes, X and T, actually become tilted,

01:35:34.340 | not perpendicular to one another.

01:35:37.680 | And you can look at Brian Greene's books and lectures

01:35:41.080 | and other things where he imagines taking a loaf of bread

01:35:45.680 | and slicing it in units of time as you progress forward.

01:35:50.040 | But then if you're zipping along relative

01:35:52.040 | to that loaf of bread,

01:35:54.160 | the slices of time actually become tilted.

01:35:57.360 | And so it's not even clear what slices of time mean,

01:36:00.560 | but I'm an observational astronomer.

01:36:02.880 | I know which end of the telescope to look through.

01:36:04.920 | And the way I understand the infinity is,

01:36:06.940 | as I just told you,

01:36:07.780 | that operationally or observationally,

01:36:11.100 | there'd be no way of seeing that it's a finite universe,

01:36:15.700 | of measuring a finite universe.

01:36:17.380 | And so in that sense, it's infinite,

01:36:20.380 | even if it started out as a finite little dot.

01:36:24.860 | Well, not a dot, I'm sorry, a finite little hypersphere.

01:36:29.420 | - But it didn't really start out there

01:36:33.780 | 'cause what happened before that?

01:36:37.740 | - Well, we don't know.

01:36:38.620 | So this is where it gets into a lot of speculation.

01:36:41.340 | - Let's go, I mean.

01:36:42.260 | - Let's go there, okay, sure.

01:36:43.260 | So, you know.

01:36:45.420 | - Nobody can prove you wrong.

01:36:46.260 | - The idea of what happened before T equals zero

01:36:49.300 | and whether there are other universes out there.

01:36:51.740 | I like to say that these are sort of

01:36:53.140 | on the boundaries of science.

01:36:55.100 | They're not just ideas that we wake up at three

01:36:57.580 | in the morning to go to the bathroom and say,

01:36:59.300 | oh, well, let's think about what happened

01:37:00.900 | before the big bang,

01:37:01.820 | or let there be a multiplicity of universes.

01:37:04.860 | In other words, we have real testable physics

01:37:08.220 | that we can use to draw certain conclusions

01:37:12.380 | that are plausibility arguments based on what we know.

01:37:16.620 | Now, admittedly, there are not really direct tests

01:37:20.540 | of these hypotheses.

01:37:24.060 | That's why I call them hypotheses.

01:37:25.540 | They're not really elevated to a theory

01:37:29.020 | 'cause a theory in science is really something

01:37:30.980 | that has a lot of experimental

01:37:33.100 | or observational support behind it.

01:37:34.860 | So, they're hypotheses,

01:37:37.300 | but they're not unreasonable hypotheses

01:37:39.940 | based on what we know about general relativity

01:37:42.100 | and quantum physics, okay?

01:37:44.140 | And they may have indirect tests

01:37:46.300 | in that if you adopt this hypothesis,

01:37:49.260 | then there might be a bunch of things you expect

01:37:51.620 | of the universe, and lo and behold, that's what we measure.

01:37:54.500 | But we're not actually measuring anything

01:37:57.660 | at T less than zero,

01:37:59.860 | or we're not actually measuring the presence

01:38:02.660 | of another universe in this multiverse.

01:38:04.980 | And yet there are these indirect ideas that stem forth.

01:38:09.100 | So, it's hard to prove uniqueness,

01:38:12.100 | and it's hard to completely convince oneself

01:38:14.620 | that a certain hypothesis must be true.

01:38:17.860 | But the more and more tests you have that it satisfies,

01:38:22.980 | let's say there are 50 predictions it makes,

01:38:25.060 | and 49 of them are things that you can measure.

01:38:30.300 | And then the 50th one is the one where you wanna measure

01:38:33.940 | the actual existence of that other universe,

01:38:36.500 | or what happened before T equals zero,

01:38:39.140 | and you can't do that.

01:38:40.380 | But you've satisfied 49 of the other testable predictions.

01:38:46.100 | And so, that's science, right?

01:38:48.940 | Now, a conventional condensed matter physicist

01:38:51.900 | or someone who deals with real data in the laboratory

01:38:54.340 | might say, "Oh, you cosmologists,

01:38:55.700 | that's not really science,

01:38:57.300 | 'cause it's not directly testable."

01:38:59.500 | But I would say it's sort of testable.

01:39:02.180 | But it's not completely testable,

01:39:03.780 | and so it's at the boundary.

01:39:05.020 | But it's not like we're coming up with these crazy ideas,

01:39:08.460 | among them quantum fluctuations out of nothing,

01:39:11.100 | and then inflating into a universe with,

01:39:14.180 | you might say, "Well, you created a giant amount

01:39:16.060 | of energy, but in fact, this quantum fluctuation

01:39:19.220 | out of nothing, in a quantum way,

01:39:21.500 | violates the conservation of energy, but who cares?

01:39:24.180 | That was a classical law anyway."

01:39:26.500 | And then an inflating universe maintains

01:39:29.180 | whatever energy it had, be it zero

01:39:31.620 | or some infinitesimal amount.

01:39:33.660 | In a sense, the stuff of the universe has a positive energy,

01:39:37.940 | but there's a negative gravitational energy

01:39:40.140 | associated with it.

01:39:41.460 | It's like I drop an apple.

01:39:43.020 | I got kinetic energy, energy of motion out of that,

01:39:45.540 | but I did work on it to bring it to that height.

01:39:49.700 | So, by going down and gaining energy of motion,

01:39:54.220 | positive one, two, three, four, five units

01:39:55.980 | of kinetic energy, it's also gaining or losing,

01:39:58.900 | depending on how you want to think of it,

01:40:01.020 | negative one, two, three, four, five units

01:40:03.300 | of potential energy, so the total energy remains the same.

01:40:07.140 | An inflating universe can do that,

01:40:09.820 | or other physicists say that energy isn't conserved

01:40:12.340 | in general relativity.

01:40:13.740 | That's another way out of creating a universe

01:40:16.340 | out of nothing, you know?

01:40:17.460 | But the point is that this is all based

01:40:20.180 | on reasonably well-tested physics,

01:40:22.620 | and although these extrapolations seem kind of outrageous

01:40:27.100 | at first, they're not completely outrageous.

01:40:29.660 | They're within the realm of what we call science already,

01:40:33.420 | and maybe some young whippersnapper

01:40:36.460 | will be able to figure out a way to directly test

01:40:39.180 | what happened before T equals zero,

01:40:41.100 | or to test for the presence of these other universes,

01:40:43.960 | but right now, we don't have a way of doing that.

01:40:46.380 | - So, speaking of young whippersnappers, Roger Penrose.

01:40:50.260 | - Yeah, yeah.

01:40:51.940 | - So, he kind of has a, you know, idea

01:40:55.300 | there may be some information that travels

01:40:58.380 | from whatever the heck happened before the Big Bang.

01:41:00.660 | - Yeah, maybe.

01:41:01.980 | I kind of doubt it.

01:41:03.220 | - So, do you think it's possible to detect something,

01:41:06.820 | like actually experimentally be able to detect some,

01:41:09.920 | I don't know what it is, radiation, some sort of--

01:41:13.820 | - Yeah, in the cosmic microwave background radiation,

01:41:15.820 | there may be ways of doing that.

01:41:18.140 | - But is it philosophically or practically possible

01:41:23.340 | to detect signs that this was before the Big Bang,

01:41:26.480 | or is it what you said, which is like,

01:41:29.100 | everything we observe will, as we currently understand,

01:41:32.940 | will have to be a creation

01:41:34.180 | of this particular observable universe?

01:41:36.340 | - Yeah, I mean, you know, if you,

01:41:38.180 | it's very difficult to answer right now,

01:41:39.780 | because we don't have a single, verified,

01:41:43.200 | fully self-consistent, experimentally tested

01:41:46.820 | quantum theory of gravity.

01:41:48.900 | And of course, the beginning of the universe

01:41:51.220 | is a large amount of stuff in a very small space.

01:41:54.180 | So you need both quantum mechanics and general relativity.

01:41:56.900 | Same thing if our universe re-collapses

01:41:58.980 | and then bounces back to another Big Bang.

01:42:01.380 | You know, there's also ideas there

01:42:02.860 | that some of the information leaks through or survives.

01:42:06.380 | I don't know that we can answer that question right now,

01:42:08.840 | because we don't have a quantum theory of gravity

01:42:12.540 | that most physicists believe in,

01:42:15.500 | and belief is perhaps the wrong word,

01:42:17.420 | that most physicists trust,

01:42:19.140 | because the experimental evidence favors it, right?

01:42:23.340 | You know, there are various forms of string theory.

01:42:25.340 | There's quantum loop gravity.

01:42:26.860 | There are various ideas,

01:42:28.620 | but which, if any, will be the one

01:42:31.800 | that survives the test of time,

01:42:33.780 | and more importantly, within that,

01:42:36.420 | the test of experiment and observation.

01:42:39.780 | So my own feeling is probably these things don't survive.

01:42:43.380 | I don't think we've seen any evidence

01:42:45.140 | in the cosmic microwave background radiation

01:42:47.540 | of information leaking through.

01:42:50.140 | Similarly, the one way, or one of the few ways

01:42:54.220 | in which we might test for the presence of other universes

01:42:56.860 | is if they were to collide with ours.

01:42:59.500 | That would leave a pattern, a temperature signature

01:43:03.100 | in the cosmic microwave background radiation.

01:43:05.700 | Some astrophysicists claim to have found it,

01:43:08.120 | but in my opinion, it's not statistically significant

01:43:11.420 | to the level that would be necessary

01:43:13.400 | to have such an amazing claim, right?

01:43:16.900 | You know, it's just a 5% chance

01:43:18.900 | that the microwave background

01:43:20.140 | had that distribution just by chance.

01:43:22.900 | 5% isn't very long odds if you're claiming that instead,

01:43:27.900 | that you're finding evidence from another universe.

01:43:34.000 | I mean, it's like if the Large Hadron Collider people

01:43:36.880 | had claimed, after gathering enough data

01:43:40.980 | to show the Higgs particle,

01:43:42.840 | when there was a 5% chance it could be

01:43:46.300 | just a statistical fluctuation in their data.

01:43:50.060 | No, they required five sigma, five standard deviations,

01:43:53.940 | which is roughly one chance in two million

01:43:57.020 | that this is a statistical fluctuation

01:43:59.780 | of no physical greater significance.

01:44:03.580 | - Extraordinary claims require extraordinary evidence.

01:44:05.500 | - There you go, it all boils down to that.

01:44:07.460 | And the greater your claim,

01:44:09.540 | the greater is the evidence that is needed,

01:44:11.620 | and the more evidence you need from independent ways

01:44:16.460 | of measuring or of coming to that deduction.

01:44:20.700 | A good example was the accelerating universe,

01:44:23.300 | you know, when we found evidence for it in 1998

01:44:26.420 | with supernovae, with exploding stars,

01:44:29.380 | it was great that there were two teams

01:44:30.980 | that lent some credibility to the discovery,

01:44:34.140 | but it was not until other astrophysicists

01:44:37.140 | used not only that technique,

01:44:39.740 | but more importantly, other independent techniques

01:44:42.820 | that had their own potential sources

01:44:45.660 | of systematic error or whatever,

01:44:47.860 | but they all came to the same conclusion,

01:44:49.780 | and that started giving a much more complete picture

01:44:52.900 | of what was going on,

01:44:53.780 | and a picture in which most astrophysicists

01:44:56.620 | quickly gained confidence.

01:44:59.080 | That's why that idea caught on so quickly,

01:45:01.760 | is that there were other physicists

01:45:05.100 | and astronomers doing observations,

01:45:08.160 | completely independent of supernovae,

01:45:10.640 | that seemed to indicate the same thing.

01:45:12.580 | - Yeah, that period of your life,

01:45:16.780 | that work with an incredible team of people

01:45:20.380 | that won the Nobel Prize,

01:45:23.520 | it's just fascinating work.

01:45:25.620 | - Oh, gosh, you know, never in my wildest dreams as a kid

01:45:29.380 | did I think that I would be involved,

01:45:32.940 | much less so heavily involved,

01:45:35.260 | in a discovery that's so revolutionary.

01:45:37.160 | I mean, you know, as a kid, as a scientist,

01:45:39.020 | if you're realistic,

01:45:40.460 | once you learn a little bit more about how science is done,

01:45:42.700 | and you're not gonna win a Nobel Prize

01:45:44.220 | and be the next Newton or Einstein or whatever,

01:45:46.980 | you just hope that you'll contribute something

01:45:49.340 | to humankind's understanding of how nature works,

01:45:52.260 | and you'll be satisfied with that.

01:45:53.960 | But here, I was in the right place at the right time,

01:45:57.780 | lot of luck, lot of hard work, and there it was.

01:46:02.140 | We discovered something that was really amazing,

01:46:05.540 | and that was the greatest thrill, right?

01:46:08.440 | I couldn't have asked for anything more

01:46:10.360 | than being involved in that discovery.

01:46:13.480 | - So the couple of teams, the Supernova Cosmology Project

01:46:17.440 | and the High-Z Supernova Search Team,

01:46:19.480 | so what was the Nobel Prize given for?

01:46:21.920 | - It was given for the discovery

01:46:23.600 | of the accelerating expansion of the universe.

01:46:25.680 | Not for the elucidation of what dark energy is

01:46:28.960 | or what causes that expansion, that acceleration,

01:46:32.280 | be it universes on the outside or whatever.

01:46:34.560 | It was only for the observational fact.

01:46:36.780 | - So first of all, what is the accelerating universe?

01:46:39.140 | - So the accelerating universe is simply that

01:46:42.140 | if we look at the galaxies moving away from us right now,

01:46:46.980 | we would expect them to be moving away more slowly

01:46:50.500 | than they were billions of years ago,

01:46:52.700 | and that's because galaxies have visible matter,

01:46:55.360 | which is gravitationally attractive,

01:46:57.580 | and dark matter of an unknown sort

01:46:59.660 | that holds galaxies together

01:47:01.740 | and holds clusters of galaxies together,

01:47:04.500 | and of course, they then pull on one another

01:47:06.820 | and they would tend to retard the expansion of the universe,

01:47:10.020 | just as when I toss an apple up,

01:47:12.920 | even ignoring air resistance,

01:47:15.600 | the mutual gravitational attraction

01:47:17.340 | between Earth and the apple slows the apple down,

01:47:19.840 | and if that attraction is great enough,

01:47:22.020 | then the apple will someday stop and even come back,

01:47:24.700 | the big crunch, you could call it,

01:47:26.100 | or the gnab-gib, which is big bang backwards, right?

01:47:28.940 | That's what could have happened to the universe,

01:47:30.400 | but even if the universe's original expansion energy

01:47:33.680 | was so great that it avoids the big crunch,

01:47:37.300 | that's like an apple thrown at Earth's escape speed,

01:47:39.740 | it's like the rockets that go to Mars someday, right?

01:47:43.940 | You know, with people.

01:47:45.860 | Even then, you'd expect the universe

01:47:48.420 | to be slowing down with time,

01:47:50.620 | but we looked back through the history of the universe

01:47:54.140 | by looking at progressively more distant galaxies,

01:47:57.660 | and by seeing that the evolution of this expansion rate

01:48:03.640 | is that in the first nine billion years,

01:48:07.080 | yeah, it was slowing down,

01:48:09.240 | but in the last five billion years, it's been speeding up.

01:48:13.560 | So who asked for that, right?

01:48:15.320 | - I think it's interesting to talk about

01:48:18.960 | a little bit of the human story of the Nobel Prize.

01:48:21.600 | - Sure.

01:48:22.440 | - Which is, I mean--

01:48:24.120 | - It's fascinating.

01:48:24.960 | - It's a really, first of all, the prize itself.

01:48:27.600 | It's kind of fascinating on the psychological level

01:48:30.400 | that prizes, I know we kind of think that prizes

01:48:34.620 | don't matter, but somehow they kind of focus the mind

01:48:37.460 | about some of the most special things we've accomplished.

01:48:40.300 | - The recognition, the funding, you know.

01:48:43.100 | - But, and also inspiration for,

01:48:45.220 | I mean, like I said, when I was a little kid,

01:48:46.700 | thinking about the Nobel Prize, like I didn't, you know,

01:48:49.600 | it inspires millions of young scientists.

01:48:52.620 | At the same time, there's a sadness to it a little bit

01:48:56.540 | that especially in the field, like depending on the field,

01:49:00.340 | but experimental fields that involve teams of,

01:49:03.680 | I don't know, sometimes hundreds of brilliant people.

01:49:08.440 | The Nobel Prize is only given to just a handful.

01:49:11.460 | I--

01:49:12.300 | - That's right.

01:49:13.120 | - Is it maxed at three?

01:49:14.800 | - Yeah, yeah, and it's not even written

01:49:16.620 | in Alfred Nobel's will, it turns out.

01:49:18.820 | One of our teammates looked into it in a museum in Stockholm

01:49:22.660 | when we went there for Nobel week in 2011.

01:49:25.780 | The leaders who got the prize formally knew

01:49:28.820 | that without the rest of us working hard in the trenches,

01:49:31.620 | the result would not have, you know, been discovered.

01:49:34.960 | So they invited us to participate in Nobel week.

01:49:37.500 | And so one of the team members looked in the will

01:49:39.720 | and it's not there, it's just tradition.

01:49:42.580 | - That's interesting.

01:49:43.420 | - It's archaic, you know,

01:49:44.420 | that's the way science used to be done.

01:49:46.740 | - Yeah.

01:49:47.580 | - And it's not the way a lot of science is done now.

01:49:49.260 | And you look at gravitational wave discovery,

01:49:51.860 | which was, you know,

01:49:53.780 | recognized with the Nobel Prize in 2017,

01:49:56.740 | Ray Weiss at MIT got it and Kip Thorne

01:49:59.860 | and Barry Barish at Caltech.

01:50:03.580 | And Ron Drever, one of the masterminds

01:50:05.780 | had passed away earlier in the year.

01:50:07.460 | So again, one of the rules of Nobel

01:50:10.540 | is that it's not given posthumously.

01:50:12.380 | - Yeah.

01:50:13.220 | - Or at least the one exception might be

01:50:14.860 | if they've made their decision

01:50:16.140 | and they're busy making their press releases

01:50:19.220 | right before October, the first week in October or whatever.

01:50:22.540 | And then the person passes away.

01:50:24.100 | I think they don't change their minds then.

01:50:25.820 | But yeah, you know,

01:50:27.140 | it doesn't square with today's reality

01:50:31.180 | that a lot of science is done by big teams.

01:50:33.540 | In that case, a team of a thousand people.

01:50:35.660 | In our case, it was two teams consisting of about 50 people.

01:50:40.020 | And we used techniques that were arguably developed

01:50:43.420 | in part by people who,

01:50:45.300 | astrophysicists who weren't even on those two papers.

01:50:48.820 | I mean, some of them were,

01:50:49.780 | but other papers were written by other people, you know?

01:50:52.780 | And so it's like,

01:50:54.020 | we're standing on the shoulders of giants.

01:50:56.420 | And none of those people was officially recognized.

01:50:59.380 | And to me, it was okay.

01:51:01.700 | You know, again, it was the thrill of doing the work

01:51:04.140 | and ultimately the work,

01:51:05.940 | the discovery was recognized with the prize.

01:51:08.580 | And, you know, we got to participate in Nobel week

01:51:10.980 | and, you know, it's okay with me.

01:51:13.980 | I've known other physicists whose lives were ruined

01:51:17.940 | because they did not get the Nobel prize

01:51:21.020 | and they felt strongly that they should have.

01:51:23.900 | - So it doesn't- - Ralph Alpher,

01:51:25.820 | of the Alpher beta Gamow, you know,

01:51:28.100 | paper predicting the microwave background radiation.

01:51:31.460 | He should have gotten it.

01:51:33.300 | His advisor Gamow was dead by that point,

01:51:36.340 | but, you know, Penzias and Wilson got it for the discovery.

01:51:39.620 | And Alpher, apparently from colleagues who knew him well,

01:51:43.660 | I've talked to them, his life was ruined by this.

01:51:46.740 | He just, it just gnawed at his innards so much.

01:51:50.620 | - It's very possible that in a small handful of people,

01:51:54.660 | even three, that you would be one of the Nobel,

01:51:57.340 | one of the winners of the Nobel prize.

01:51:59.300 | That doesn't weigh heavy on you?

01:52:00.740 | - Well, you know, there were the two team leaders,

01:52:03.020 | Saul Perlmutter and Brian Schmidt,

01:52:04.940 | and usually it's the team leaders that are recognized.

01:52:07.500 | And then Adam Rees was my postdoc.

01:52:10.220 | - First author, I guess.

01:52:11.620 | - Yeah, first author.

01:52:12.460 | I was second author of that paper.

01:52:13.780 | Yeah.

01:52:14.620 | So I was his direct mentor at the time,

01:52:16.380 | although he was, you know,

01:52:17.220 | one of these people who just, you know, runs with things.

01:52:19.860 | He was an MIT undergraduate, by the way,

01:52:22.020 | Harvard graduate student,

01:52:24.580 | and then a postdoc as a so-called Miller Fellow

01:52:27.820 | for basic research in science at Berkeley,

01:52:30.140 | something that I was back in '84 to '86.

01:52:32.980 | But you're, you know, you're largely a free agent,

01:52:35.940 | but he worked quite closely with me,

01:52:37.780 | and he came to Berkeley to work with me.

01:52:39.500 | And on Schmidt's team,

01:52:41.460 | he was charged with analyzing the data,

01:52:43.660 | and he measured the brightnesses of these distant supernovae

01:52:47.780 | showing that they're fainter

01:52:49.100 | and thus more distant than anticipated.

01:52:51.300 | And that led to this conclusion

01:52:53.380 | that the universe had to have accelerated

01:52:55.380 | in order to push them out to such great distances.

01:52:58.340 | And I was shocked when he showed me the data,

01:53:01.380 | the results of his calculations and measurements.

01:53:03.860 | - But it's very-

01:53:05.540 | - So he deserved it.

01:53:06.700 | And on Saul's team,

01:53:07.860 | Gerson Goldhaber deserved it,

01:53:10.300 | but he died, I think, a year earlier in 2010,

01:53:12.940 | but that would have been four.

01:53:14.660 | And so,

01:53:17.020 | and me, well, I was on both teams,

01:53:19.180 | but, you know, was I number four, five, six, seven?

01:53:22.260 | I don't know.

01:53:23.100 | - It's also very, so if I were to,

01:53:25.900 | it's possible that you're, I mean,

01:53:27.700 | I could make a very good case for you're in the three.

01:53:31.020 | And does that-

01:53:33.140 | - You're kind, you know, so-

01:53:34.460 | - But is that psychologically,

01:53:36.180 | I mean, listen, it weighs on me a little bit,

01:53:38.460 | because I,

01:53:39.300 | I don't know what to do with that.

01:53:43.220 | Perhaps it should motivate

01:53:46.740 | the rethinking, like Time Magazine started doing,

01:53:50.580 | like, you know, Person of the Year.

01:53:52.660 | - Yeah.

01:53:53.500 | - And like, they would start doing like concepts

01:53:55.500 | and almost like the black hole gets the Nobel Prize,

01:53:58.540 | or the Xcelerator universe gets the Nobel Prize,

01:54:01.900 | and here's the list of people.

01:54:03.740 | So like, or like the Oscar that you could say,

01:54:08.140 | because it-

01:54:09.100 | - It's a team effort now.

01:54:10.300 | - It's a team.

01:54:11.140 | - And it should be redone.

01:54:12.140 | And the Breakthrough Prize in Fundamental Physics,

01:54:15.020 | which was started by Yuri Milner,

01:54:16.500 | and Zuckerberg is involved in others as well, you know.

01:54:20.060 | - They recognize the larger team.

01:54:21.980 | - Yeah, they recognize teams.

01:54:24.300 | And so in fact, both teams in the Xcelerating universe

01:54:27.420 | were recognized with the Breakthrough Prize in 2015.

01:54:31.100 | Nevertheless, the same three people,

01:54:34.620 | Reese, Perlmutter, and Schmidt,

01:54:36.700 | got the red carpet rolled out for them

01:54:38.700 | and were at the big ceremony

01:54:40.820 | and shared half of the prize money.

01:54:43.420 | And the rest of us, roughly 50,

01:54:45.700 | shared the other half and didn't get to go to the ceremony.

01:54:48.820 | But I feel for them.

01:54:50.140 | I mean, for the gravitational waves, it was 1,000 people.

01:54:52.860 | What are they gonna do, invite everyone?

01:54:54.620 | For the Higgs particle,

01:54:55.980 | it was 6,000 to 8,000 physicists and engineers.

01:54:58.700 | In fact, because of the whole issue of who gets it,

01:55:02.180 | experimentally that discovery

01:55:04.260 | still has not been recognized, right?

01:55:06.620 | The theoretical work by Peter Higgs and Englert

01:55:11.020 | got recognized, but there was a troika of other people

01:55:14.020 | who perhaps wrote the most complete paper

01:55:16.820 | and they were left out.

01:55:19.060 | And another guy died, you know?

01:55:22.620 | - It's all of this heartbreaking.

01:55:24.180 | Some people argue that the Nobel Prize

01:55:26.420 | has been diluted too,

01:55:27.420 | because if you look at Roger Penrose,

01:55:29.940 | you can make an argument

01:55:31.100 | that he should get the prize by himself.

01:55:33.500 | Like, so separate those-

01:55:36.060 | - Could have and should have.

01:55:37.020 | Perhaps he should have perhaps gotten it with Hawking

01:55:39.540 | before Hawking's death, right?

01:55:41.700 | The problem was Hawking radiation had not been detected,

01:55:45.140 | but you could argue that Hawking made enough

01:55:47.020 | other fundamental contributions

01:55:49.580 | to the theoretical study of black holes.

01:55:51.940 | And the observed data were already good enough

01:55:55.420 | at the time of before Hawking's death, okay?

01:55:58.380 | I mean, the latest results by Reinhard Genzel's group

01:56:00.620 | is that they see the time dilation effect

01:56:03.380 | of a star that's passing very close to the black hole

01:56:06.460 | in the middle of our galaxy.

01:56:07.540 | That's cool, and it adds additional evidence,

01:56:10.300 | but hardly anyone doubted the existence

01:56:13.220 | of the supermassive black hole.

01:56:14.820 | And Andrea Ghez's group, I believe,

01:56:16.940 | hadn't yet shown that relativistic effect,

01:56:19.340 | and yet she got part of the prize as well.

01:56:21.020 | So clearly it was given for the original evidence

01:56:24.700 | that was really good.

01:56:25.540 | And that evidence is at least a decade old, you know?

01:56:28.500 | So one could make the case for Hawking.

01:56:31.180 | One could make the case that in 2016,

01:56:34.860 | when Mayor and K. Lowe's won the Nobel Prize

01:56:37.980 | for the discovery of the first exoplanet, 51B Pegasi,

01:56:42.980 | well, there was a fellow at Penn State, Alex Wolshon,

01:56:47.420 | who in 1992, three years preceding 1995,

01:56:52.340 | found a planet orbiting a pulsar,

01:56:55.900 | a very weird kind of star, a neutron star,

01:56:57.860 | and that wouldn't have been a normal planet, sure.

01:57:01.140 | And so the Nobel Committee, you know,

01:57:03.180 | they gave it for the discovery of planets

01:57:05.540 | around normal sun-like stars,

01:57:07.820 | but hell, you know, Wolshon found a planet,

01:57:10.820 | so they could have given it to him as the third person

01:57:13.460 | instead of to Jim Peebles for the development

01:57:16.340 | of what's called physical cosmology.

01:57:18.180 | He's at Princeton, he deserved it,

01:57:19.900 | but they could have given the Nobel

01:57:22.100 | for the development of physical cosmology to Peebles,

01:57:25.700 | and I would claim some other people

01:57:27.140 | were pretty important in that development as well, you know?

01:57:29.140 | And they could have given it some other year.

01:57:32.460 | So there's a lot of controversy.

01:57:35.060 | I try not to dwell on it.

01:57:36.460 | Was I number three?

01:57:37.460 | Probably not.

01:57:38.300 | You know, Adam Ries did the work.

01:57:40.620 | You know, I helped bounce ideas off of him,

01:57:43.300 | but we wouldn't have had the result without him.

01:57:46.940 | And I was on both teams for reasons.

01:57:50.300 | I mean, you know, the style of the first team,

01:57:53.340 | the Supernova Cosmology Project, didn't match mine.

01:57:56.260 | They came largely from experimental

01:57:57.980 | high-energy particle physics,

01:57:59.740 | where there's these hierarchical teams and stuff,

01:58:02.300 | and it's hard for the little guy to have a say.

01:58:05.060 | At least that's what I kind of thought.

01:58:06.660 | Whereas the team of astronomers led by Brian Schmidt

01:58:10.500 | was, first of all, a bunch of my friends,

01:58:12.300 | and they grew up as astronomers

01:58:15.060 | making contributions on little teams,

01:58:16.820 | and we decided to band together,

01:58:18.220 | but all of us had our voices heard.

01:58:20.340 | So it was sort of a culture, a style that I preferred,

01:58:24.220 | really, but let me tell you a story.

01:58:27.180 | At the Nobel banquet, okay,

01:58:30.260 | I'm sitting there between two physicists

01:58:32.700 | who are members of the committee

01:58:34.540 | of the Swedish National Academy of Sciences,

01:58:37.380 | you know, and I strategically kept offering them wine

01:58:40.500 | and stuff during this long, drawn-out Nobel ceremony, right?

01:58:44.900 | And I got them to be pretty talkative,

01:58:47.180 | and then in a polite, diplomatic way,

01:58:49.540 | I started asking them pointed questions.

01:58:52.740 | And basically, they admitted

01:58:54.260 | that if there are four or more people equally deserving,

01:58:58.460 | they wait for one of them to die,

01:59:00.780 | or they just don't give the prize at all

01:59:02.740 | when it's unclear who the three are,

01:59:05.380 | at least unclear to them.

01:59:06.900 | But unclear to them,

01:59:08.580 | they're not even right part of the time.

01:59:12.220 | I mean, Jocelyn Bell discovered pulsars

01:59:16.580 | with a set of radio antennas

01:59:20.420 | that her advisor, Anthony Hewish,

01:59:22.900 | conceived and built, so he deserves some credit.

01:59:27.700 | But he didn't discover the pulsar, she did.

01:59:31.260 | And his initial reaction to the data that she showed him

01:59:35.820 | was a condescending, "Rubbish, my dear."

01:59:39.820 | Yeah, I'm not kidding.

01:59:41.940 | Now, I know Jocelyn Bell,

01:59:43.420 | and she did not let this destroy her life.

01:59:46.820 | She won every other prize under the sun, okay?

01:59:50.180 | Vera Rubin, arguably one of the discoverers of dark matter,

01:59:56.260 | although there, if you look at the history,

01:59:57.980 | there were a number of people, and that was the issue.

02:00:00.180 | I think there were a number of people, four or more,

02:00:02.460 | who had similar data and similar ideas

02:00:04.580 | at about the same time.

02:00:06.380 | Rubin won every prize under the sun.

02:00:09.100 | The new big, large-scale survey telescope

02:00:12.060 | being built in Chile is being renamed

02:00:14.620 | the Vera Rubin Telescope,

02:00:16.900 | 'cause she passed away in December of 2015, I think.

02:00:19.700 | It'll conduct this survey, large-scale survey,

02:00:25.340 | with the Rubin Telescope.

02:00:26.580 | So she's been recognized, but never with the Nobel Prize.

02:00:30.100 | And I would say that, to her credit,

02:00:32.100 | she did not let that consume her life either.

02:00:35.940 | And perhaps it was a bit easier

02:00:37.340 | because there had been no Nobel given

02:00:40.500 | for the discovery of dark matter,

02:00:42.140 | whereas in the case of pulsars and Jocelyn Bell,

02:00:45.500 | there was a prize given

02:00:46.940 | for the discovery of the freaking pulsars,

02:00:49.580 | and she didn't get it.

02:00:50.820 | I mean, what a travesty of justice.

02:00:52.980 | - So I also think, as a fan of fiction,

02:00:57.980 | as a fan of stories, that the travesty and the tragedy

02:01:02.100 | and the unfairness and the tension of it

02:01:06.100 | is what makes the prize and similar prizes beautiful.

02:01:09.900 | The decisions of other humans that result

02:01:14.540 | in dreams being broken.

02:01:17.180 | That's why we love the Olympics,

02:01:21.220 | as so many people, athletes, give their whole life

02:01:25.220 | for this particular moment.

02:01:26.580 | - Yeah, that's cool.

02:01:27.540 | - And then there's referee decisions

02:01:29.460 | and little slips of here and there,

02:01:32.100 | like the little misfortunes that destroy entire dreams.

02:01:36.260 | And that's, it's weird to say,

02:01:39.060 | but it feels like that makes the entirety of it

02:01:42.220 | even more special.

02:01:43.540 | - Yeah.

02:01:44.380 | - If it was perfect, it wouldn't be interesting.

02:01:46.380 | - Well, humans like competition and they like heroes,

02:01:49.340 | and unfortunately it gives the impression

02:01:51.260 | to youngsters today that science is still done

02:01:54.620 | by white men with gray beards wearing white lab coats.

02:01:58.940 | And I'm very pleased to see that this year,

02:02:02.100 | Andrea Ghez, the fourth woman in the history

02:02:04.500 | of the physics prize to have received it.

02:02:07.340 | And then two women, one at Berkeley,

02:02:10.460 | one elsewhere won the Nobel Prize in chemistry

02:02:13.220 | without any male co-recipient.

02:02:15.940 | And so that's sending a message, I think, to girls

02:02:18.900 | that they can do science and they have role models.

02:02:23.620 | I think the Breakthrough Prize and other such prizes

02:02:26.860 | show that teams get recognized as well.

02:02:30.380 | And if you pay attention to the newspapers,

02:02:33.820 | most of the good authors like Dennis Overby

02:02:38.020 | of the New York Times and others said

02:02:39.820 | that these were teams of people and they emphasize that.

02:02:42.980 | And they all played a role.

02:02:45.860 | And maybe if some grad student hadn't soldered

02:02:48.180 | some circuit, maybe the whole thing wouldn't have worked.

02:02:51.140 | But still, Ray Weiss, Kip Thorne was the theoretical impetus

02:02:57.060 | for the whole search for gravitational waves.

02:03:02.420 | Barry Barish brought the MIT and Caltech teams together

02:03:06.620 | to get them to cooperate at a time when the project

02:03:09.860 | was nearly dead from what I understand

02:03:12.100 | and contributed greatly to the experimental setup as well.

02:03:16.140 | He's a great experimental physicist,

02:03:17.540 | but he was really good at bringing these two teams together

02:03:21.300 | instead of having them duke it out in blows

02:03:23.220 | and leaving both of them bleeding and dying.

02:03:25.700 | The National Science Foundation was gonna cut the funding

02:03:28.500 | from what I understand.

02:03:29.740 | So there's human drama involved in this whole thing.

02:03:33.820 | And the Olympics, yeah, a runner, a swimmer, a runner,

02:03:37.460 | they slip just at the moment that they were taking off

02:03:42.020 | from the first thing and that costs them

02:03:43.860 | some fraction of a second and that's it.

02:03:46.220 | They didn't win.

02:03:47.980 | - And in that case, I mean, the coaches, the families,

02:03:51.900 | which I met a lot of Olympic athletes,

02:03:54.020 | and the coaches and the families of the athletes

02:03:56.380 | are really the winners of the medals.

02:03:59.300 | But they don't get the medal.

02:04:02.580 | Credit assignment is a fascinating thing.

02:04:06.940 | That's the full human story.

02:04:08.380 | And outside of prizes, it's fascinating.

02:04:14.580 | Just to be in the middle of it,

02:04:15.620 | for artificial intelligence,

02:04:16.900 | there's a field of deep learning that's really exciting.

02:04:19.660 | And people have been, there's yet another award,

02:04:24.140 | the Turing Award given for deep learning to three folks

02:04:28.540 | who are very much responsible for the field,

02:04:31.060 | but so are a lot of others.

02:04:32.580 | - Yeah, that's right.

02:04:33.780 | - And there's a few, there's a fellow

02:04:36.780 | by the name of Schmidt-Huber,

02:04:41.340 | who sort of symbolizes the forgotten folks

02:04:46.340 | in the deep learning community.

02:04:48.740 | But that's the unfortunate, sad thing,

02:04:51.940 | where you remember Isaac Newton,

02:04:55.660 | or remember these special figures

02:04:59.820 | and the ones that flew close to them, we forget.

02:05:04.820 | - Well, that's right.

02:05:05.700 | And often the breakthroughs were made

02:05:07.700 | based on the body of knowledge

02:05:09.580 | that had been assimilated prior to that.

02:05:13.060 | But again, people like to worship heroes.

02:05:15.780 | You mentioned the Oscars earlier,

02:05:17.500 | and you look at the direct, I mean, well, I mean, okay,

02:05:22.140 | directors and stuff sometimes get awards and stuff,

02:05:24.620 | but you look at even something like, I don't know,

02:05:27.980 | songwriters, musicians, Elton John or something, right?

02:05:30.340 | Bernie Taupin, right?

02:05:31.860 | Wrote many of the words, or he's not as well-known,

02:05:36.620 | or the Beatles or something like that.

02:05:39.820 | - I was heartbroken to learn

02:05:41.140 | that Elvis didn't write most of his songs.

02:05:43.300 | - Yeah, Elvis, that's right, there you go.

02:05:45.420 | But he was the king, right?

02:05:47.140 | And he had such a personality,

02:05:48.580 | and it was such a performer, right?

02:05:51.180 | But it's the unsung heroes in many cases, yeah.

02:05:54.180 | - So maybe taking a step back,

02:05:56.580 | we talked about the Nobel Prize

02:05:59.060 | for the accelerating universe,

02:06:00.300 | but your work and the ideas around supernova

02:06:05.220 | were important in detecting this accelerating universe.

02:06:10.220 | Can we go to the very basics

02:06:14.060 | of what is this beautiful, mysterious object of a supernova?

02:06:17.620 | - Right, so a supernova is an exploding star.

02:06:20.860 | Most stars die a relatively quiet death,

02:06:23.460 | our own sun will, despite the fact

02:06:25.420 | that it'll become a red giant and incinerate Earth.

02:06:28.180 | It'll do that reasonably slowly,

02:06:30.220 | but there's a small minority of stars

02:06:32.500 | that end their lives in a titanic explosion.

02:06:35.660 | And that's not only exciting to watch from afar,

02:06:38.700 | but it's critical to our existence

02:06:40.500 | because it is in these explosions

02:06:42.820 | that the heavy elements synthesize

02:06:45.340 | through nuclear reactions during the normal course

02:06:48.020 | of the star's evolution, and during the explosion itself,

02:06:51.940 | get ejected into the cosmos,

02:06:53.860 | making them available as raw material

02:06:56.660 | for new stars, planets, and ultimately life,

02:07:00.020 | and that's just a great story.

02:07:02.260 | The best in some ways.

02:07:04.620 | So, you know, we like to study these things

02:07:06.900 | and our origins, but it turns out

02:07:09.260 | these are incredibly useful beacons as well,

02:07:12.420 | because if you know how powerful

02:07:14.740 | an exploding star really is

02:07:17.780 | by measuring the apparent brightness at its peak

02:07:22.260 | in galaxies whose distances we already know

02:07:24.940 | through having made other measurements,

02:07:27.500 | and you can thus calibrate how powerful the thing really is,

02:07:31.900 | and then you find ones that are much more distant,

02:07:35.340 | then you can use their observed brightness

02:07:38.380 | compared with their true intrinsic power or luminosity

02:07:42.100 | to judge their distance,

02:07:43.500 | and hence the distance of the galaxy

02:07:45.300 | in which they're located.

02:07:46.820 | - So- - Okay, it's like looking at,

02:07:48.380 | if you'll, let me just give this one analogy.

02:07:51.580 | You know, you judge the distance of an oncoming car at night

02:07:55.300 | by looking at how bright its headlights appear to be,

02:07:58.260 | and you've calibrated how bright the headlights are

02:08:01.580 | of a car that's two or three meters away of known distance,

02:08:04.780 | and you go, "Whoa, that's a faint headlight,

02:08:06.820 | "and so that's pretty far away."

02:08:09.060 | You also use the apparent angular separation

02:08:12.180 | between the two headlights

02:08:13.340 | as a consistency check in your brain,

02:08:15.140 | but that's what your brain is doing.

02:08:16.660 | So we can do that for cars, we can do that for stars.

02:08:20.500 | - Nice, I like that.

02:08:21.540 | But, you know, with cars, the headlights are all,

02:08:24.860 | there's some variation, but they're somewhat similar,

02:08:29.100 | so you can make those kinds of conclusions.

02:08:31.180 | What, how much variation is there between supernova

02:08:35.620 | that you can- - Yeah.

02:08:37.300 | - And can you detect them?

02:08:38.860 | - Right, so first of all, there are several different ways

02:08:41.420 | that stars can explode, and it depends on their mass

02:08:44.020 | and whether they're in a binary system and things like that.

02:08:47.340 | And the ones that we used for these cosmological purposes,

02:08:50.780 | studying the expansion of the history of the universe,

02:08:54.020 | are the so-called type Roman numeral one, lowercase a,

02:08:58.540 | type 1a supernovae.

02:09:00.500 | They come from a weird type of a star called a white dwarf.

02:09:04.220 | Our own sun will turn into a white dwarf

02:09:06.940 | in about 7 billion years.

02:09:08.940 | It'll have about half its present mass

02:09:11.740 | compressed into a volume just the size of Earth.

02:09:14.820 | So that's an inordinate density, okay?

02:09:17.020 | It's incredibly dense.

02:09:18.740 | And the matter is what's called,

02:09:20.620 | by quantum physicists, degenerate matter,

02:09:23.000 | not because it's morally reprehensible

02:09:24.860 | or anything like that, but this is just the name-

02:09:26.900 | - No judgments here.

02:09:27.740 | - Yeah, quantum physicists give to electrons

02:09:30.460 | that are squeezed into a very tight space.

02:09:32.940 | The electrons take on a motion

02:09:34.940 | due to Heisenberg's uncertainty principle,

02:09:38.420 | and also due to the Pauli exclusion principle

02:09:40.980 | that electrons don't like to be in the same place.

02:09:43.540 | They like to avoid each other.

02:09:44.620 | So those two things mean that a lot of electrons

02:09:47.620 | are moving very rapidly,

02:09:49.180 | which gives the star an extra pressure

02:09:51.860 | far above the thermal pressure associated

02:09:54.220 | with just the random motions of particles inside the star.

02:09:57.860 | So it's a weird type of star,

02:09:59.580 | but normally it wouldn't explode,

02:10:02.220 | and our sun won't explode,

02:10:04.540 | except that if such a white dwarf is in a pair

02:10:07.860 | with another more or less normal star,

02:10:10.160 | it can steal material from that normal star

02:10:14.340 | until it gets to an unstable limit,

02:10:17.140 | roughly one and a half times the mass of our sun,

02:10:20.860 | 1.4 or so.

02:10:22.340 | This is known as the Chandrasekhar limit,

02:10:25.460 | after Subrahmanyan Chandrasekhar,

02:10:27.540 | an Indian astrophysicist who figured this out

02:10:30.260 | when he was about 20 years old

02:10:32.260 | on a voyage from India to England

02:10:35.020 | where he was to be educated.

02:10:36.860 | And then he did this,

02:10:38.020 | and then 50 years later,

02:10:39.220 | he won the Nobel Prize in physics in 1984,

02:10:42.260 | largely for this work, okay,

02:10:44.100 | that he did as a youngster

02:10:45.260 | who was on his way to be educated, you know?

02:10:48.060 | Oh, and his advisor,

02:10:50.500 | the great Arthur Eddington in England,

02:10:53.140 | who had done a lot of great things

02:10:54.540 | and was a great astrophysicist,

02:10:55.940 | nevertheless, he too was human and had his faults.

02:10:59.500 | He ridiculed Chandra's scientific work

02:11:03.900 | at a conference in England.

02:11:05.380 | And most of us, if we had been Chandra,

02:11:08.180 | would have just given up astrophysics at that time,

02:11:12.100 | when the great Arthur Eddington ridicules our work.

02:11:16.380 | And that's another inspirational story for the youngster,

02:11:19.580 | just keep going, you know?

02:11:21.320 | But anyway, John-

02:11:22.160 | - Ignore your advisor.

02:11:22.980 | - Yeah, no matter what your advisor says, right?

02:11:25.060 | So, or don't always pay attention to your advisor, right?

02:11:28.020 | Don't be, don't lose hope

02:11:30.380 | if you really think you're onto something.

02:11:32.420 | That doesn't mean never listen to your advisor,

02:11:34.300 | they may have sage advice as well.

02:11:36.580 | But anyway, you know,

02:11:38.500 | when a white dwarf grows to a certain mass,

02:11:41.780 | it becomes unstable.

02:11:43.420 | And one of the ways it can end its life

02:11:45.300 | is to go through a thermonuclear runaway.

02:11:48.820 | So basically, the carbon nuclei inside the white dwarf

02:11:52.660 | starts start fusing together to form heavier nuclei.

02:11:56.740 | And the energy that those fusion reactions emits

02:11:59.860 | doesn't go into, you know,

02:12:05.820 | being dissipated out of the star or, you know, whatever,

02:12:09.140 | or expanding it the way, you know,

02:12:11.700 | if you take a blowtorch to the middle of the sun,

02:12:14.060 | you heat up its gases, the gases would expand and cool.

02:12:17.580 | But this degenerate star can't expand and cool.

02:12:21.220 | And so the energy pumped in through these fusion reactions

02:12:25.420 | goes into making the nuclei move faster.

02:12:28.460 | And that gets more of them sufficiently close together

02:12:31.620 | that they can undergo nuclear fusion,

02:12:33.740 | thereby releasing more energy

02:12:35.740 | that goes into speeding up more nuclei.

02:12:38.780 | And thus you have a runaway, a bomb,

02:12:41.860 | an uncontrolled nuclear fusion reactor, right?

02:12:45.060 | Instead of the controlled fusion,

02:12:46.420 | which is what our sun does, okay?

02:12:48.300 | Our sun is a marvelous controlled fusion reactor.

02:12:51.340 | This is what we need here on earth,

02:12:52.940 | fusion energy to solve our energy crisis, right?

02:12:56.020 | But the sun holds the stuff in, you know, through gravity,

02:12:58.860 | and you need a big mass to do that.

02:13:00.940 | So this uncontrolled fusion reaction blows up a star

02:13:05.500 | that's pretty much the same in all cases.

02:13:09.260 | And you measure it to be almost the same in all cases,

02:13:12.860 | but the devil's in the details.

02:13:14.900 | And in fact, we observe them to not be all the same.

02:13:18.660 | And theoretically, they might not be all the same

02:13:21.100 | because the rate of the fusion reactions

02:13:23.460 | might depend on the amount of trace heavier elements

02:13:27.620 | in the white dwarf.

02:13:28.540 | And that could depend on how old it is,

02:13:30.300 | when it was, you know,

02:13:31.460 | whether it was born billions of years ago

02:13:33.220 | when there weren't many heavier elements,

02:13:35.060 | or whether it's a relatively young white dwarf

02:13:37.820 | and all kinds of other things.

02:13:39.900 | And part of my work was to show that indeed,

02:13:42.460 | not all the type IAs are the same.

02:13:44.860 | You have to be careful when you use them.

02:13:47.420 | You have to calibrate them.

02:13:49.060 | They're not standard candles,

02:13:51.540 | the way it just, if all headlights or all candles

02:13:55.300 | were the same lumens or whatever,

02:13:57.780 | you'd say they're standard,

02:13:58.940 | and then it would be relevant.

02:13:59.780 | - Standard candles is an awesome term.

02:14:01.300 | Okay. (laughs)

02:14:02.140 | - Standard candles is what astronomers like to say,

02:14:03.740 | but I don't like that term

02:14:05.580 | 'cause there aren't any standard candles,

02:14:07.300 | but there are standardizable candles.

02:14:10.060 | And by looking at these type IA--

02:14:11.220 | - Oh, calibrate them, that's what you mean.

02:14:12.620 | - Yeah, you're calibratable, standardizable, calibratable.

02:14:15.100 | You look at enough of them in nearby galaxies

02:14:17.660 | whose distances you know independently.

02:14:20.300 | And what you can tell is that, you know,

02:14:23.660 | and this is something that a colleague of mine,

02:14:25.060 | Mark Phillips, did, who was on Schmidt's team,

02:14:28.020 | and arguably was one of the people

02:14:30.100 | who deserved the Nobel Prize,

02:14:31.340 | but he showed that the intrinsically

02:14:33.500 | more powerful type IAs decline in brightness,

02:14:39.180 | and it turns out rise in brightness as well,

02:14:41.740 | more slowly than the less luminous IAs.

02:14:45.020 | And so if you calibrate this

02:14:47.100 | by measuring a whole bunch of nearby ones,

02:14:49.900 | and then you look at a distant one,

02:14:52.060 | instead of saying, well, it's a 100-watt type IA supernova,

02:14:56.060 | they're much more powerful than that, by the way,

02:14:57.980 | plus or minus 50, you can say,

02:15:00.100 | no, it's 112 plus or minus 15,

02:15:04.460 | or it's 84 plus or minus 17.

02:15:08.860 | It tells you where it is in the power scale,

02:15:12.460 | and it greatly decreases the uncertainties,

02:15:15.220 | and that's what makes these things cosmologically useful.

02:15:18.860 | I showed that if you spread the light out into a spectrum,

02:15:22.460 | you can tell spectroscopically

02:15:24.180 | that these things are different as well.

02:15:26.460 | And in 1991, I happened to study

02:15:29.380 | two of the extreme peculiar ones,

02:15:32.180 | the low-luminosity ones and the high-luminosity ones,

02:15:35.940 | 1991 BG and 1991 T.

02:15:40.500 | This showed that not all the IAs are the same,

02:15:43.500 | and indeed, at the time of 1991,

02:15:46.500 | I was a little bit skeptical that we could use type IAs

02:15:50.340 | because of this diversity that I was observing.

02:15:53.060 | But in 1993, Mark Phillips wrote a paper

02:15:56.420 | that showed this correlation between the light curve,

02:16:00.580 | the brightness versus time, and the peak luminosity.

02:16:03.740 | And once you- - Which gives you

02:16:04.580 | enough information to calibrate.

02:16:05.780 | - Yeah, then they become calibratable,

02:16:07.060 | and that was a game changer.

02:16:08.220 | - How many type IAs are out there to use for data?

02:16:12.340 | - Now there are thousands of them.

02:16:13.780 | - Thousands, wow. - But at the time,

02:16:15.420 | the high Z team had 16,

02:16:18.300 | and the Supernova Cosmology Project had 40,

02:16:22.420 | but the 16 were better measured than the 40,

02:16:25.820 | and so our statistical uncertainties were comparable

02:16:29.860 | if you look at the two papers that were published.

02:16:31.940 | - How does that make you feel

02:16:34.060 | that there's these gigantic explosions

02:16:36.820 | just sprinkled out there?

02:16:38.700 | Is that- - Well, I certainly don't want one

02:16:40.220 | to be very nearby, and it would have to be

02:16:42.500 | within something like 10 light years

02:16:44.660 | to be an existential threat.

02:16:46.340 | - So they can happen in our galaxy?

02:16:49.020 | - Oh, yeah, yeah, yeah.

02:16:49.940 | So they can happen- - We would be okay?

02:16:52.380 | - In most cases, we'd be okay,

02:16:53.820 | 'cause our galaxy is 100,000 light years across,

02:16:56.980 | and you'd need one of these things

02:16:58.540 | to be within about 10 light years

02:17:00.420 | to be an existential threat.

02:17:01.940 | - And it gives birth to a bunch of other stars, I guess?

02:17:06.940 | - Yeah, it gives birth to expanding gases

02:17:09.140 | that are chemically enriched,

02:17:10.300 | and those expanding gases mix

02:17:12.020 | with other chemically enriched expanding gases,

02:17:15.340 | or primordial clouds of hydrogen and helium.

02:17:18.740 | I mean, this is, in a sense,

02:17:21.300 | the greatest story ever told, right?

02:17:23.840 | I teach this introductory astronomy course at Berkeley,

02:17:28.100 | and I tell 'em there's only five or six things

02:17:30.660 | that I want them to really understand and remember,

02:17:33.700 | and I'm gonna come to their deathbed,

02:17:35.260 | and I'm gonna ask them about this,

02:17:36.860 | and if they get it wrong, I will retroactively fail them.

02:17:40.100 | Their whole career will have been shot.

02:17:41.980 | That, and if they don't know- - That's a student's

02:17:43.060 | worst nightmare.

02:17:43.900 | - And observe a total solar eclipse,

02:17:45.500 | and yet they had the opportunity to do so,

02:17:47.460 | I will retroactively fail them.

02:17:48.940 | But one of them is, where did we come from?

02:17:51.660 | Where did the elements in our DNA come from?

02:17:54.500 | The carbon in our cells, the oxygen that we breathe,

02:17:57.520 | the calcium in our bones, the iron in our red blood cells,

02:18:01.540 | those elements, the phosphorus in our DNA,

02:18:04.060 | they all came from stars, from nuclear reactions in stars,

02:18:08.780 | and they were ejected into the cosmos,

02:18:12.380 | and in some cases, like iron, made during the explosions.

02:18:16.980 | And those gases drifted out, mixed with other clouds,

02:18:20.960 | made a new star or a star cluster,

02:18:24.060 | some of whose members then evolved and exploded,

02:18:27.780 | thus enriching the gases in the galaxy

02:18:31.060 | progressively more with time,

02:18:32.580 | until finally, 4 1/2 billion years ago,

02:18:35.900 | from one of these chemically enriched clouds,

02:18:38.900 | our solar system formed with a rocky Earth-like planet,

02:18:43.180 | and somewhere, somehow, these self-replicating,

02:18:46.440 | evolving molecules, bacteria, formed and evolved

02:18:51.620 | through paramecia and amoebas and slugs and apes and us.

02:18:56.620 | And here we are, sentient beings

02:19:01.700 | that can ask these questions about our very origins,

02:19:05.140 | and with our intellect and with the machines we make,

02:19:09.120 | come to a reasonable understanding of our origins.

02:19:13.960 | What a beautiful story.

02:19:16.580 | I mean, if that does not put you at least in awe,

02:19:20.860 | if not in love with science and its power of deduction,

02:19:25.860 | I don't know what will, right?

02:19:29.380 | It's one of the greatest stories,

02:19:31.420 | if not the greatest story.

02:19:32.940 | Obviously, that's personality dependent and all that.

02:19:36.100 | It's a subjective opinion,

02:19:37.500 | but it's perhaps the greatest story ever told.

02:19:40.400 | I mean, you could link it to the Big Bang

02:19:43.020 | and go even farther, right,

02:19:44.260 | to make an even more complete story,

02:19:46.060 | but as a subset, that's even, in some ways,

02:19:49.740 | a greater story than even the existence of the universe,

02:19:53.220 | in some ways, 'cause you could end up,

02:19:54.940 | you could just imagine some really boring universe

02:19:57.240 | that never leads to sentient creatures such as ourselves.

02:20:01.220 | - And is a supernova usually the introduction to that story?

02:20:06.220 | - Yeah.

02:20:07.620 | - So are they usually the thing that launches the,

02:20:10.220 | is there other engines of creation?

02:20:12.360 | - Well, the supernova is the one,

02:20:14.200 | I mean, I touch upon the subject earlier in my course,

02:20:18.380 | in fact, right about now in my lectures,

02:20:19.860 | because I talk about how our sun right now

02:20:22.420 | is fusing hydrogen to form helium nuclei,

02:20:25.140 | and later it'll form carbon and oxygen nuclei,

02:20:29.060 | but that's where the process will stop for our sun.

02:20:31.820 | It's not massive enough.

02:20:32.760 | Some stars that are more massive can go somewhat beyond that.

02:20:36.960 | So that's the beginning of, right,

02:20:39.020 | this idea of the birth of the heavy elements,

02:20:41.740 | since they couldn't have been born

02:20:43.980 | at the time of the Big Bang.

02:20:45.140 | Conditions of temperature and pressure

02:20:47.260 | weren't sufficient to make any significant quantities

02:20:50.220 | of the heavier elements.

02:20:51.780 | And so that's the beginning,

02:20:53.540 | but then you need some of these stars to explode, right?

02:20:57.260 | Because if those heavy elements remained forever trapped

02:21:00.540 | in the cores of stars,

02:21:02.500 | then they would not be available

02:21:05.040 | for the production of new stars, planets,

02:21:07.700 | and ultimately life.

02:21:08.820 | So indeed, the supernova, my main area of interest,

02:21:13.360 | plays a leading role in this whole story.

02:21:17.460 | - I saw that you got a chance to call Richard Feynman

02:21:21.380 | a mentor of yours when you were at Caltech.

02:21:24.260 | Do you have any fond memories of Feynman,

02:21:27.220 | any lessons that stick with you?

02:21:28.740 | - Oh yeah, he was quite a character

02:21:31.660 | and one of the deepest thinkers of all time, probably.

02:21:35.940 | And at least in my life,

02:21:37.820 | the physicist who had the single most intuitive understanding

02:21:42.820 | of how nature works of anyone I've met.

02:21:46.780 | He, I learned a number of things from him.

02:21:50.740 | He was not my thesis advisor.

02:21:52.380 | I worked with Wallace Sargent at Caltech

02:21:54.500 | on what are called active galaxies,

02:21:56.740 | big black holes in the centers of galaxies

02:21:58.820 | that are accreting or swallowing material,

02:22:01.500 | a little bit like the stuff

02:22:02.500 | of this year's Nobel Prize in physics 2020.

02:22:05.500 | But Feynman I had for two courses.

02:22:09.220 | One was general theory of relativity at the graduate level

02:22:12.620 | and one was applications of quantum physics

02:22:15.380 | to all kinds of interesting things.

02:22:17.820 | And he had this very intuitive way of looking at things

02:22:22.820 | that he tried to bring to his students.

02:22:28.820 | And he felt that if you can't explain something

02:22:33.080 | in a reasonably simple way to a non-scientist,

02:22:38.080 | or at least someone who is versed a little bit with science

02:22:42.340 | but is not a professional scientist,

02:22:44.700 | then you probably don't understand it very well yourself,

02:22:48.140 | very thoroughly.

02:22:49.320 | So that in me,

02:22:51.000 | made a desire to be able to explain science

02:22:57.040 | to the general public.

02:22:58.300 | And I've often found that in explaining things,

02:23:00.660 | yeah, there's a certain part

02:23:02.100 | that I didn't really understand myself.

02:23:03.780 | That's one reason I like to teach the introductory courses

02:23:06.620 | to the lay public is that I sometimes find

02:23:08.980 | that my explanations are lacking in my own mind.

02:23:12.580 | So he did that for me.

02:23:14.100 | - Is there, if I could just pause for a second.

02:23:16.580 | You said he had one of the most intuitive understanding

02:23:18.980 | of nature.

02:23:20.220 | If you could break apart what intuitive means,

02:23:23.980 | is it on a philosophical level?

02:23:26.860 | - No, sort of physical.

02:23:28.460 | How do you draw a mental picture or a picture on paper

02:23:32.680 | of what's going on?

02:23:33.580 | And he's perhaps most famous in this regard

02:23:36.100 | for his Feynman diagrams,

02:23:37.660 | which in what's called quantum electrodynamics,

02:23:40.460 | a quantum field theory of electricity and magnetism,

02:23:43.940 | what you have are actually, you know,

02:23:45.620 | an exchange of photons between charged particles.

02:23:48.660 | And they might even be virtual photons

02:23:50.980 | if the particles are at rest relative to one another.

02:23:55.340 | And there are ways of doing calculations

02:23:57.380 | that are brute force,

02:23:58.660 | that take pages on pages and pages of calculations.

02:24:02.140 | And Julian Schwinger developed some of the mathematics

02:24:05.540 | for that and won the Nobel prize for it.

02:24:07.580 | But Feynman had these diagrams that he made

02:24:09.900 | and he had a set of rules of what to do at the vertex.

02:24:13.140 | And he'd have two particles coming together

02:24:14.660 | and then a particle going out

02:24:15.940 | and then two particles coming out again.

02:24:17.800 | And he'd have these rules associated

02:24:19.900 | when there were vertices

02:24:21.000 | and when there were particles splitting off

02:24:22.780 | from one another and all that.

02:24:24.100 | And it looked a little bit

02:24:25.780 | like a bunch of a hodgepodge at first,

02:24:27.820 | but to those who learned the rules and understood them,

02:24:31.340 | they saw that you could do these complex calculations

02:24:35.080 | in a much simpler way.

02:24:37.100 | And indeed, in some ways,

02:24:38.660 | Freeman Dyson had an even better knack

02:24:41.580 | for explaining really what quantum electrodynamics

02:24:44.460 | actually was.

02:24:46.060 | But I didn't know Freeman Dyson, I knew Feynman.

02:24:49.060 | Maybe he did have a more intuitive view of the world

02:24:51.740 | than Feynman did.

02:24:52.820 | But of the people I knew,

02:24:54.500 | Feynman was the most intuitive,

02:24:56.940 | most sort of, is there a picture?

02:24:58.820 | Is there a simple way you can understand this?

02:25:00.900 | And in the path that a particle follows even,

02:25:05.700 | you can figure out the,

02:25:07.600 | you can get the classical path,

02:25:09.900 | at least for a baseball or something like that,

02:25:12.140 | by using quantum physics if you want.

02:25:14.420 | But in a sense,

02:25:16.500 | the baseball sniffs out all possible paths.

02:25:19.740 | It goes out to the Andromeda galaxy

02:25:21.340 | and then goes to the batter.

02:25:22.940 | But the probability of doing that is very, very small

02:25:26.380 | because tiny little paths next door to any given path

02:25:30.380 | cancel out that path.

02:25:32.280 | And the ones that all add together,

02:25:35.820 | they're the ones that are more likely to be followed.

02:25:38.860 | And this actually ties in with Fermat's

02:25:42.020 | principle of least action.

02:25:43.700 | And there are ideas in optics that go into this as well.

02:25:47.380 | And it just sort of beautifully brings everything together.

02:25:50.500 | But the particle sniffs out all possible paths.

02:25:53.960 | What a crazy idea.

02:25:54.980 | But if you do the mathematics associated with that,

02:25:57.720 | it ends up being actually useful,

02:26:00.780 | a useful way of looking at the world.

02:26:02.700 | - So you're also, I mean, you're widely acknowledged as,

02:26:06.100 | I mean, outside of your science work

02:26:07.460 | as being one of the greatest educators in the world.

02:26:12.100 | And Feynman is famous for being that.

02:26:16.100 | Is there something about being a teacher that you--

02:26:19.060 | - Well, it's very, very rewarding

02:26:21.000 | when you have students who are really into it.

02:26:23.040 | And going back to Feynman,

02:26:25.900 | at Caltech I was taking these graduate courses

02:26:28.260 | and there were two of us, myself and Jeff Richman,

02:26:32.000 | who's now a professor of physics

02:26:33.460 | at University of California, Santa Barbara,

02:26:36.020 | who asked lots of questions.

02:26:37.900 | And a lot of the Caltech students

02:26:40.240 | are nervous about asking questions.

02:26:42.380 | They wanna save face.

02:26:43.900 | They seem to think that if they ask a question,

02:26:46.380 | their peers might think it's a stupid question.

02:26:49.440 | Well, I didn't really care what people thought

02:26:51.420 | and Jeff Richman didn't either.

02:26:52.540 | And we'd ask all these questions.

02:26:53.980 | And in fact, in many cases, they were quite good questions.

02:26:57.420 | And Feynman said, well, the rest of you

02:26:58.980 | should be having questions like this.

02:27:00.620 | And I remember one time in particular when he said,

02:27:05.940 | he said to the rest of the class,

02:27:06.940 | why is it always these two?

02:27:08.900 | Aren't the rest of you curious about what I'm saying?

02:27:11.980 | Do you really understand it all that well?

02:27:14.520 | If so, why aren't you asking

02:27:16.020 | the next most logical question?

02:27:18.280 | No, you guys are too scared to ask these questions

02:27:21.580 | that these two are asking.

02:27:23.220 | So he actually invited us to lunch a couple of times

02:27:26.380 | where just the three of us sat and had lunch

02:27:29.820 | with one of the greatest thinkers of 20th century physics.

02:27:33.540 | And so, yeah, he rubbed off on me

02:27:35.780 | and-- - So you encourage questions

02:27:37.460 | as well? - I encourage questions.

02:27:39.060 | (laughing)

02:27:40.540 | Yeah, definitely.

02:27:42.060 | I mean, I encourage questions.

02:27:44.860 | I like it when students ask questions.

02:27:47.060 | I tell them that they shouldn't feel shy

02:27:49.420 | about asking a question.

02:27:51.060 | Probably half the students in the class

02:27:53.140 | would have that same question

02:27:54.340 | if they even understood the material enough

02:27:56.620 | to ask that question, yeah.

02:27:59.180 | - Curiosity is the first step of--

02:28:02.140 | - Absolutely. - Of seeing

02:28:03.500 | the beauty of something.

02:28:04.500 | So yeah, and the question is the ultimate form of curiosity.

02:28:08.900 | - Yeah.

02:28:09.980 | - Let me ask, what is the meaning of life?

02:28:13.040 | - The meaning of life, you know--

02:28:16.020 | - From a cosmologist's perspective

02:28:17.580 | or from a human perspective? - Or from my personal,

02:28:19.820 | you know, life is what you make of it, really, right?

02:28:23.260 | Each of us has to have our own meaning.

02:28:27.380 | And it doesn't have to be,

02:28:31.500 | well, I think that in many cases,

02:28:33.460 | meaning is to some degree associated with goals.

02:28:36.180 | You set some goals or expectations for yourself,

02:28:38.980 | things you want to accomplish, things you wanna do,

02:28:42.800 | things you wanna experience.

02:28:44.260 | And to the degree that you experience those

02:28:47.240 | and do those things, it can give you meaning.

02:28:50.700 | You don't have to change the world

02:28:53.420 | the way Newton or Michelangelo or da Vinci did.

02:28:56.580 | I mean, people often say, "You changed the world."

02:28:58.620 | But look, come on, there's seven and a half,

02:29:00.780 | close to eight billion of us now.

02:29:02.500 | Most of us are not gonna change the world.

02:29:04.380 | And does that mean that most of us

02:29:05.980 | are leading meaningful lives?

02:29:07.740 | No, it just has to be something that gives you meaning,

02:29:12.460 | that gives you satisfaction,

02:29:15.040 | that gives you a good feeling about what you did.

02:29:17.420 | And often, based on human nature,

02:29:20.780 | which can be very good and also very bad,

02:29:23.900 | but often it's the things that help others

02:29:27.100 | that give us meaning and a feeling of satisfaction.

02:29:31.580 | You taught someone to read.

02:29:33.580 | You cared for someone who was terminally ill.

02:29:36.580 | You brought up a nice family.

02:29:38.660 | You brought up your kids.

02:29:40.860 | You did a good job.

02:29:42.100 | You put your heart and soul into it.

02:29:44.360 | You read a lot of books, if that's what you wanted to do,

02:29:48.080 | had a lot of perspectives on life.

02:29:50.700 | You traveled the world, if that's what you wanted to do.

02:29:53.900 | But if some of these things are not within reach,

02:29:57.620 | you're in a socioeconomic position

02:30:00.380 | where you can't travel the world or whatever,

02:30:02.820 | you find other forms of meaning.

02:30:05.500 | It doesn't have to be some profound,

02:30:10.940 | I'm gonna change the world,

02:30:13.220 | I'm gonna be the one who everyone remembers type thing.

02:30:17.020 | - In the context of the greatest story ever told,

02:30:20.020 | like the fact that we came from stars

02:30:22.380 | and now we're two apes asking about the meaning of life.

02:30:30.060 | How does that fit together?

02:30:31.460 | How does that make any sense?

02:30:34.660 | - It does, it does.

02:30:35.860 | And this is sort of what I was referring to,

02:30:38.220 | that it's a beautiful universe

02:30:41.260 | that allows us to come into creation.

02:30:45.360 | It's a way that the universe found of knowing,

02:30:50.460 | of understanding itself.

02:30:51.880 | Because I don't think that inanimate rocks and stars

02:30:56.060 | and black holes and things have any real capability

02:30:59.620 | of abstract thoughts and of learning

02:31:04.220 | about the rest of the universe or even their origins.

02:31:08.540 | I mean, they're just a pile of atoms

02:31:10.540 | that has no conscience, has no ability to think,

02:31:15.540 | has no ability to explore.

02:31:18.140 | And we do.

02:31:20.300 | And I'm not saying we're the epitome of all life forever,

02:31:25.300 | but at least for life on earth so far,

02:31:29.500 | the evidence suggests that we are the epitome

02:31:32.340 | in terms of the richness of our thoughts,

02:31:35.940 | the degree to which we can explore the universe,

02:31:38.900 | do experiments, build machines, understand our origins.

02:31:43.060 | And I just hope that we use science for good, not evil,

02:31:48.060 | and that we don't end up destroying ourselves.

02:31:50.660 | I mean, the whales and dolphins are plenty intelligent.

02:31:53.980 | They don't ask abstract questions, they don't read books,

02:31:58.140 | but on the other hand, they're not in any danger

02:32:00.660 | of destroying themselves and everything else as well.

02:32:03.340 | And so maybe that's a better form of intelligence,

02:32:06.040 | but at least in terms of our ability to explore

02:32:10.160 | and make use of our minds.

02:32:13.060 | I mean, to me, it's this.

02:32:16.180 | It's this that gives me the potential for meaning, right?

02:32:21.180 | The fact that I can understand and explore.

02:32:24.460 | - It's kind of fascinating to think

02:32:25.860 | that the universe created us,

02:32:27.580 | and eventually we've built telescopes to look back at it,

02:32:33.980 | to look back at its origins

02:32:35.620 | and to wonder how the heck the thing works.

02:32:39.620 | - It's magnificent.

02:32:41.380 | Needn't have been that way, right?

02:32:44.140 | And this is one of the multiverse sort of things.

02:32:47.700 | You can alter the laws of physics

02:32:50.420 | or even the constants of nature,

02:32:52.580 | seemingly inconsequential things

02:32:54.820 | like the mass ratio of the proton and the neutron.

02:32:57.900 | Wake me up when it's over, right?

02:32:59.660 | What could be more boring?

02:33:00.980 | But it turns out you play with things a little bit

02:33:03.300 | like the ratio of the mass of the neutron to the proton,

02:33:06.580 | and you generally get boring universes,

02:33:09.780 | only hydrogen or only helium or only iron.

02:33:12.460 | You don't even get the rich periodic table,

02:33:14.700 | let alone bacteria, paramecia, slugs, and humans, okay?

02:33:19.700 | I'm not even anthropocentralizing this

02:33:23.900 | to the degree that I could.

02:33:25.220 | Even a rich periodic table wouldn't be possible

02:33:29.300 | if certain constants weren't this way, but they are.

02:33:33.700 | And that to me leads to the idea of a multiverse

02:33:37.660 | that the dice were thrown many, many times,

02:33:39.980 | and there's this cosmic archipelago

02:33:41.900 | where most of the universes are boring,

02:33:43.980 | and some might be more interesting,

02:33:45.580 | but we are in the rare breed

02:33:48.180 | that's really quite darn interesting.

02:33:51.580 | And if there were only one, and maybe there is only one,

02:33:54.500 | well, then that's truly amazing.

02:33:56.940 | - We're lucky.

02:33:57.860 | - We're lucky, but I actually think there are lots and lots,

02:34:00.420 | just like there are lots of planets,

02:34:02.860 | Earth isn't special for any particular reason,

02:34:05.740 | there are lots of planets in our solar system,

02:34:07.740 | and especially around other stars,

02:34:09.660 | and occasionally there are gonna be ones

02:34:11.300 | that are conducive to the development of complexity

02:34:14.700 | culminating in life as we know it.

02:34:16.900 | And that's a beautiful story.

02:34:19.820 | - I don't think there's a better way to end it, Alex.

02:34:21.740 | It's a huge honor.

02:34:22.940 | One of my favorite conversations I've had in this podcast.

02:34:25.260 | - Well, thank you so much. - Thank you so much

02:34:26.260 | for talking, it was fun.

02:34:27.460 | - For the honor of having been asked to do this.

02:34:30.780 | - Thanks for listening to this conversation

02:34:33.220 | with Alex Filippenko, and thank you to our sponsors.

02:34:36.660 | Neuro, the maker of functional sugar-free gum and mints

02:34:40.820 | that I use to give my brain a quick caffeine boost.

02:34:43.820 | BetterHelp, online therapy with a licensed professional.

02:34:47.460 | MasterClass, online courses that I enjoy

02:34:50.900 | from some of the most amazing humans in history.

02:34:53.980 | And Cash App, the app I use to send money to friends.

02:34:58.300 | Please check out these sponsors in the description

02:35:00.540 | to get a discount and to support this podcast.

02:35:04.140 | If you enjoy this thing, subscribe on YouTube,

02:35:06.540 | review it with Five Stars on Apple Podcast,

02:35:08.900 | follow on Spotify, support on Patreon,

02:35:11.580 | or connect with me on Twitter @lexfriedman.

02:35:15.420 | And now, let me leave you with some words from Carl Sagan.

02:35:19.500 | The nitrogen in our DNA, the calcium in our teeth,

02:35:23.980 | the iron in our blood, the carbon in our apple pies

02:35:28.420 | were made in the interiors of collapsing stars.

02:35:32.220 | We are made of star stuff.

02:35:34.680 | Thank you for listening, and hope to see you next time.

02:35:38.820 | (upbeat music)

02:35:41.400 | (upbeat music)

02:35:43.980 | [BLANK_AUDIO]

Alex Filippenko: Supernovae, Dark Energy, Aliens & the Expanding Universe | Lex Fridman Podcast #137

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