back to indexAlex Filippenko: Supernovae, Dark Energy, Aliens & the Expanding Universe | Lex Fridman Podcast #137
Chapters
0:0 Introduction
2:8 Universe expansion
3:32 Dark energy
11:0 Scientific revolutions
22:50 Asteroid hitting Earth
26:22 Giant solar flares and the power grid
33:22 Elon Musk and space exploration
38:13 Exoplanets
45:35 Traveling close to the speed of light
47:45 Traveling faster than the speed of light
56:11 Intelligent life in the universe
59:46 Fermi Paradox
69:24 Finding alien life would be bad news
74:20 UFO sightings
87:30 Universe expansion speed
92:14 The universe is infinite
96:30 What happened before the Big Bang?
100:46 Roger Penrose
104:20 Nobel Prize for the accelerating universe
125:55 Supernova
137:19 The greatest story ever told
141:16 Richard Feynman
148:9 Meaning of life
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 00:00:12.700 |
"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. 00:00:33.320 |
"and is one of the most widely admired educators 00:00:39.300 |
"and I'm sure Alex will be back again in the future. 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. 00:01:02.460 |
"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. 00:01:24.580 |
"in their capacity to create and to destroy us. 00:01:33.160 |
"threaten our humble, fragile existence here on Earth. 00:01:42.340 |
"it's easy to forget just how lucky we humans are 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, 00:02:03.740 |
And now, here's my conversation with Alex Filippenko. 00:02:07.640 |
Let's start by talking about the biggest possible thing, 00:02:13.140 |
- Will the universe expand forever or collapse on itself? 00:02:18.060 |
That's one of the big questions of cosmology. 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. 00:02:38.740 |
So if that continues, the universe will expand forever. 00:02:48.540 |
in principle, collapse at some point in the far, far future. 00:02:56.860 |
and then to bet all my money on one or the other, 00:03:01.420 |
- Well, right now I would say that it would expand forever, 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 00:03:23.740 |
because it's not something that changes with time. 00:03:36.060 |
Do we have any understanding of what the heck that thing is? 00:03:44.060 |
So, you know, different theories of what it might be 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. 00:04:08.260 |
because one would have to show that the numbers, 00:04:12.100 |
that the measured numbers agree with the predictions 00:04:17.180 |
And of course, even if you've got eight, nine, 10, 00:04:23.020 |
the measurements significantly differ from the prediction? 00:04:26.940 |
Then the dark energy isn't this vacuum state, 00:04:35.260 |
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, 00:04:47.340 |
And that type of energy could in principle change 00:04:52.580 |
It could become gravitationally attractive for all we know. 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, 00:05:12.260 |
That dark energy like substance, we call it the inflaton, 00:05:24.540 |
So the exponential early expansion of the universe 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. 00:06:03.260 |
through this rigorously like an experimentalist. 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? 00:06:31.580 |
there are no miracles of a supernatural nature. 00:06:55.860 |
So if it turns out that it's one of these new fields 00:07:04.380 |
But there are many categories of those sorts of fields. 00:07:12.140 |
by comparing the actual measurements with the predictions. 00:07:21.860 |
And the data just have to become a lot better 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? 00:07:39.900 |
but there are many, many versions of quintessence. 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 00:08:00.460 |
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, 00:08:10.540 |
which gravitationally act outward on our bubble 00:08:17.580 |
the quantum particle that is thought to carry gravity 00:08:23.700 |
the space between these different little bubble membranes 00:08:27.580 |
And so it's conceivable that these other universes 00:08:37.900 |
No class of models has been ruled out completely. 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 00:08:55.380 |
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 00:09:09.900 |
that which causes the acceleration and dark matter, 00:09:13.460 |
that which causes galaxies and clusters of galaxies 00:09:18.180 |
even though there's not enough visible matter to do so. 00:09:28.220 |
So Ptolemy had a geocentric and Aristotelian view of the world. 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. 00:09:54.980 |
where the planet is going in the direction opposite 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 00:10:27.740 |
by a sum of sines and cosines of different periods, 00:10:54.660 |
And as a scientist, I have to be open to that possibility 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, 00:11:07.140 |
that the Earth, everything rotates around Earth, 00:11:29.900 |
500 years ago, where he had this philosophical preference 00:11:44.100 |
in terms of the measured positions of planets, 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 00:12:09.340 |
it was known that the sun is much farther away than the moon. 00:12:18.580 |
But the observed positions of planets at the time, 00:12:26.540 |
under the heliocentric system, was not a better match, 00:12:32.360 |
than Ptolemy's system, which was quite accurate 00:12:45.900 |
So you have to have a young person come along 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 00:13:22.940 |
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. 00:13:43.100 |
The sun was a little bit off-center, it turns out, 00:13:48.700 |
looks like a slightly eccentric elliptical orbit. 00:13:54.500 |
showed that the orbits are actually, in general, 00:13:57.100 |
ellipses, not circles, the reason that, you know, 00:14:09.820 |
is not much different from a slightly eccentric ellipse. 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 00:14:40.700 |
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, 00:14:56.900 |
from new to crescent to quarter to gibbous to full 00:15:01.180 |
to waning gibbous, third quarter, waning crescent, 00:15:09.980 |
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 00:15:53.740 |
And secondly, Earth could be moving, as Jupiter does, 00:16:15.100 |
but I didn't realize how much data they were working with. 00:16:26.940 |
It was a lot of data and you're playing with it 00:16:33.420 |
with completely abstract thought experiments. 00:16:38.260 |
- Sure, and you look at Newton's great work, right? 00:16:41.780 |
It was based in part on Galileo's observations 00:16:48.540 |
supposedly falling off the Leaning Tower of Pisa, 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, 00:17:09.840 |
to assemble and publish the results of his experiments 00:17:15.520 |
It's not clear he would have had time to do that, you know, 00:17:27.460 |
- Let me ask the old Russian overly philosophical question 00:17:33.140 |
So we're talking about the expanding universe. 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? 00:17:58.780 |
- Yeah, so we're gonna leave out the anthropogenic- 00:18:26.780 |
which I think will be our evolutionary descendants, 00:18:32.140 |
will have less and less energy with which to work 00:18:40.140 |
although it takes them trillions of years to do so. 00:18:47.420 |
there are other celestial threats, existential threats, 00:18:52.180 |
comets, exploding stars, the sun burning out. 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? 00:19:31.260 |
that unless there are compensatory atmospheric changes, 00:19:41.580 |
for the temperatures to be maintained roughly 00:19:47.780 |
So you can't lower the carbon dioxide content too much. 00:20:06.660 |
such as ourselves that require quite special conditions, 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. 00:20:31.740 |
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, 00:20:48.460 |
And there we have very little warning, months to a year. 00:20:54.020 |
- Oh, the deep freeze is sort of out beyond Neptune. 00:20:59.140 |
and it consists of a bunch of dirty ice balls 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, 00:21:34.300 |
comet-like objects that occasionally get disturbed 00:21:39.980 |
And most of them go flying out of the solar system, 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, 00:22:12.260 |
just because of conservation of momentum, right? 00:22:18.980 |
And so since we can't predict how much outgassing 00:22:25.020 |
because these things are tumbling and rotating and stuff, 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 00:22:38.340 |
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? 00:22:58.900 |
maybe a high probability that there would be a collision? 00:23:26.700 |
you only have to deflect it by a tiny little angle. 00:23:31.940 |
the perpendicular motion is big enough to, you know, 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. 00:23:57.240 |
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 00:24:14.540 |
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. 00:24:31.560 |
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. 00:25:04.100 |
I think you're saying there in a scientific one, 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. 00:25:21.460 |
like probes out there to be able to sort of almost 00:25:25.100 |
have little finger sensors throughout our solar system 00:25:30.660 |
Yeah, monitoring the asteroid belt is very important. 00:25:41.180 |
And even if there's, you know, a close encounter 00:25:47.100 |
it's unlikely to be on a collision course with Earth 00:25:58.060 |
to detect the objects that come in from a great distance. 00:26:04.060 |
The comets come in, you know, 1% of the collisions 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 00:26:35.540 |
But over the course of the history of life on Earth, 00:26:50.180 |
was caused by a star blowing up in particular, 00:26:56.300 |
And I think it's the Ordovician-Sulurian extinction, 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. 00:27:31.740 |
Or a giant solar flare that shorts out the grid 00:27:40.300 |
Now, you know, astronomers are monitoring the sun 24/7 00:27:52.380 |
a giant bundle of energetic particles will arrive 00:28:23.980 |
you can get short circuits even over small distance scales. 00:28:30.380 |
but at least the whole grid might not go out. 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. 00:28:57.060 |
we can actually predict and do something about 00:29:01.500 |
or observe before they hit and do something about. 00:29:07.420 |
to think that people would listen to this conversation. 00:29:12.260 |
talk about pandemics in his TED Talk a few years ago 00:29:21.580 |
because as I said, I actually think human-induced threats 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? 00:29:41.700 |
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 00:29:57.100 |
But we can see in the history of volcanic eruptions, 00:30:13.860 |
one of which, by the way, exists under Yellowstone, 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 00:30:53.180 |
including this one, Toba I think it's called, 00:30:57.180 |
where it's estimated that the human population 00:31:10.380 |
it's not clear that even with today's advanced technology, 00:31:18.100 |
Maybe some would be in these underground caves 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 00:31:32.900 |
of millions or billions of people starving to death. 00:31:45.620 |
- There you go, dash that toilet paper, you know, 00:31:50.100 |
I mean, imagine North America without power for a year, 00:32:00.140 |
What do they care about the electrical grid, right? 00:32:05.900 |
but we now have become so used to our way of life 00:32:12.820 |
those rugged individualists who live somewhere 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, 00:32:48.220 |
- And this whole conversation is making me realize 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 00:33:22.240 |
- So we're kind of, there's this beautiful dance between, 00:33:28.900 |
that astronomy, the stars, inspires everybody. 00:33:33.900 |
And at the same time, there's this pragmatic aspect 00:33:38.900 |
And so I see space exploration as the same kind of way, 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, 00:34:05.300 |
it's obvious we need to become a multi-planetary species 00:34:10.440 |
So maybe both philosophically, in terms of beauty, 00:34:27.620 |
by the possibility of going to Mars, colonizing Mars, 00:34:40.860 |
- Humans are, by their very nature, explorers, pioneers. 00:34:46.940 |
see what's behind it, explore the ocean depths, 00:34:57.900 |
yes, we need to plant our seeds elsewhere, really, 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 00:35:21.940 |
Nevertheless, it's prudent to have us be elsewhere as well. 00:35:26.740 |
So in that regard, I actually agree with Elon. 00:35:52.740 |
I mean, look at the success he's had with multiple companies. 00:35:55.780 |
So maybe he gives this very optimistic timeline 00:36:04.220 |
And certainly his success with the rocket that is reusable, 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, 00:36:35.700 |
but people out there, and two is the colonization. 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. 00:36:53.300 |
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, 00:37:02.180 |
You need to melt the water that's in the permafrost 00:37:05.460 |
or have canals dug from which you transport it 00:37:11.820 |
- You know, I was reading recently in terms of like, 00:37:14.620 |
what's the most efficient source of nutrition 00:37:25.020 |
- So you wanna build giant colonies of insects 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. 00:37:41.300 |
like in the movie "The Martian," you know, or something. 00:38:08.460 |
well, that's not gonna house that many people, right? 00:38:14.820 |
We're looking for a new apartment to move into, 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 00:38:31.780 |
- There are lots and lots of homes, possible homes. 00:38:49.860 |
which was flying around above Earth's atmosphere, 00:38:57.060 |
and they could detect planets crossing the line of sight 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 00:39:27.300 |
which is what you need for this transit method to work. 00:39:33.420 |
and certainly perpendicular to your line of sight, 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 00:40:18.180 |
And then they've been finding these earth-like planets, 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? 00:40:52.300 |
at Earth's escape speed, which is 11 kilometers per second? 00:41:03.940 |
Let's say a generation of humans is 25 years, right? 00:41:10.860 |
that is able to sustain itself, all their food, 00:41:18.540 |
For 10,000 generations, they have to commit themselves 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? 00:41:52.740 |
I mean, it's a form of artificial intelligence. 00:41:57.900 |
You just tell the thing, fix yourself, basically. 00:42:04.900 |
initially from materials that were perhaps sent, 00:42:10.020 |
And then they set up factories with which to do this. 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 00:42:34.260 |
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, 00:42:46.780 |
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, 00:43:07.700 |
like a little drop of whatever makes us humans so special, 00:43:27.300 |
and that how beautiful it is that our thoughts, 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, 00:43:51.860 |
That, to me, is a beautiful thought in some ways, 00:43:54.180 |
but others find it to be a horrific thought, right? 00:44:00.260 |
because to me, from purely an engineering perspective, 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, 00:44:29.220 |
that naturally the systems that will out-compete us 00:44:35.940 |
on this earth will be cold and non-conscious, 00:44:44.980 |
and empathy and compassion and love and hate. 00:44:52.980 |
But to me, intelligence requires all of that. 00:45:02.020 |
- Right, so artificial general intelligence, in my view, 00:45:13.500 |
- It might look very different than us humans, 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, 00:45:45.460 |
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 00:46:08.620 |
to the speed of light to make the time scale short 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. 00:46:24.460 |
of the speed of light, but that's just a proton. 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, 00:46:44.820 |
And so getting close to the speed of light, I think, 00:47:02.300 |
take a picture of the exoplanets that we know orbit 00:47:08.380 |
- Say hello real quick. - Say hello real quickly, 00:47:19.540 |
with a whole bunch of high-powered lasers aimed at it. 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. 00:47:54.820 |
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 00:48:12.700 |
- Perhaps, is that at all an interesting thing for you? 00:48:21.980 |
is that also a possible, like a dream for you 00:48:28.100 |
how we can actually use it to improve our transportation? 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 00:48:44.060 |
to make it very, very short through a wormhole 00:48:53.940 |
which I realize people have gone down that rabbit hole. 00:49:01.540 |
said that all of fundamental physics is done. 00:49:07.140 |
Then came special relativity, quantum physics, 00:49:14.980 |
On the other hand, I think we know a lot more now 00:49:23.100 |
And to me, most of these schemes, if not all of them, 00:49:33.220 |
You know, it appears that for a non-rotating black hole, 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? 00:49:53.740 |
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. 00:50:12.940 |
not that we expect charged black holes to exist in nature 00:50:15.980 |
because they would quickly bring in the opposite charge 00:50:20.900 |
But rotating black holes, definitely a reality. 00:50:31.220 |
that when you go in, you go in with so much energy 00:51:01.620 |
but there's a way maybe of bringing it back, right? 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 00:51:23.500 |
and you could essentially prevent your grandparents 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 00:51:37.140 |
to prevent the history from allowing you to exist, right? 00:51:42.140 |
It's a violation of causality of cause and effect. 00:51:49.980 |
take causality violation very, very seriously. 00:52:01.460 |
And you have to work things out in such a way 00:52:06.500 |
Some people say that, well, you come back to the universe, 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 00:52:27.020 |
and the many worlds interpretation and all that. 00:52:33.820 |
And you don't come back to the universe from which you left. 00:52:44.300 |
necessarily, then, to the same universe, right? 00:52:55.900 |
- You ended up in a different place than you started. 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. 00:53:20.420 |
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. 00:53:34.220 |
is that you'd have to get to those places in front of you 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 00:54:06.340 |
"and then I'll make it over to Alpha Centauri 00:54:24.300 |
to just extending the life of the human in some form, 00:54:37.540 |
might be different if somehow our understanding of genetics, 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, 00:54:55.220 |
and so these 10,000 generations I talked about, 00:54:58.580 |
It's just one generation, and they're asleep, okay? 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? 00:55:28.420 |
requires truly unfathomable amounts of energy, 00:55:37.540 |
divided by the square root of one minus V squared 00:55:48.900 |
that one over the square root of one minus V squared 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. 00:56:16.340 |
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. 00:56:36.740 |
as a cosmologist, what's your intuition about 00:56:41.380 |
whether there is or isn't intelligent life out there, 00:56:45.900 |
- 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 00:56:54.660 |
roughly 14 billion years in light travel time 00:57:01.980 |
when you take into account the expansion of space. 00:57:06.660 |
is something like 90, 92 billion light years. 00:57:09.500 |
That encompasses 100 billion to a trillion galaxies 00:57:17.180 |
So now you're talking about something like 10 to the 22nd, 00:57:22.540 |
and roughly an equal number of Earth-like planets and so on. 00:57:32.140 |
- But your sense is our galaxy is not teeming with life. 00:57:44.940 |
- Yeah, I wouldn't, well, I'll get to the primitive life, 00:57:48.540 |
But we may well be the only ones in our Milky Way galaxy 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 00:58:08.540 |
as being a natural evolutionary path for life. 00:58:15.860 |
First of all, there's been more than 10 billion species 00:58:21.700 |
Nothing has approached our level of intelligence 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 00:58:52.020 |
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, 00:59:03.580 |
Thirdly, it's not clear that our intelligence 00:59:10.700 |
Now it's clear that in the last 100 years, 200 years, 00:59:17.300 |
but at the risk of potentially destroying ourselves, 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, 01:00:13.380 |
and true, we've only looked a couple of hundred 01:00:36.840 |
when the Industrial Revolution started on Earth, right? 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, 01:01:06.460 |
I mean, there's no telling what they could have achieved 01:01:11.380 |
let alone a million or 10 million or a billion years. 01:01:20.500 |
then you can show that within 10 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 01:01:38.140 |
do you think it's possible that they are already here, 01:01:59.860 |
do you think we'll actually detect intelligent life 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 01:02:12.900 |
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 01:02:27.340 |
- It's just that my own feeling is that in science now, 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 01:02:50.140 |
Okay, you know, why would some super intelligence 01:02:55.980 |
for accelerating the expansion of the universe? 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 01:03:22.300 |
- Yeah, I would say from the mystery perspective, 01:03:30.260 |
it seems like the mystery of our own cognition 01:03:36.700 |
like the degrees of freedom of possible explanations 01:03:39.460 |
for what the heck is going on is much greater there 01:03:50.380 |
But they, to me, don't indicate the existence 01:04:00.180 |
from some rocket ship that hit here a long, long time ago 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? 01:04:15.900 |
And so though there are potential explanations 01:04:26.380 |
are those that decided not to colonize the whole galaxy 01:04:33.740 |
You send a probe to a planet, it makes two copies. 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 01:05:04.660 |
this tendency for aggression and self-destruction, right? 01:05:11.860 |
of the great filters if there are more than one, right? 01:05:30.900 |
like prime directive where you go and explore worlds 01:05:42.140 |
but there is underlying this desire to explore 01:05:47.300 |
I mean, if we're just being really honest about- 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 01:06:16.500 |
- 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 01:06:35.140 |
So they've got their seeds in a bunch of places, 01:06:44.140 |
with this incredibly primitive organism, Homo sapiens, 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 01:07:12.540 |
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. 01:07:24.300 |
but at that point, you're right on this dividing line 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. 01:07:50.220 |
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, 01:08:10.820 |
a bunch of sand grains just came together randomly 01:08:45.020 |
And then the big next step is where you have a nucleus, 01:08:50.180 |
which allows the cell to become much, much more complex 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 01:09:16.540 |
an obstacle that is just incredibly rare to get through. 01:09:24.140 |
- And one of the really exciting scientific things 01:09:29.500 |
is something that we might be able to discover, 01:09:33.500 |
even in our lifetimes, that find life elsewhere, 01:09:42.740 |
'Cause if we find lots of pretty advanced life, 01:09:46.500 |
that would suggest, and especially if we found 01:09:57.180 |
- Defunct civilization of like primitive life forms. 01:10:01.220 |
If we found some intelligent or even trilobites, right, 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? 01:10:26.220 |
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 01:10:34.460 |
that means that the great filter is ahead of us 01:10:36.660 |
and that bodes poorly for our long-term future. 01:10:41.700 |
- Yeah, it's funny you said, you started by saying 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 01:11:09.260 |
and there are such great filters, maybe more than one, 01:11:14.660 |
formation of eukaryotic that is with the nucleus cells 01:11:18.260 |
be another, development of human-like intelligence 01:11:27.620 |
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. 01:11:36.300 |
but it still could be the case that there's one of us, 01:11:42.580 |
or a thousand galaxies, and we're sitting here 01:11:48.940 |
And so there's an observational selection effect there. 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 01:12:26.500 |
So, you know, I knew Hawking and I greatly respect 01:12:33.020 |
the early work on the unification of general theory 01:12:40.140 |
you know, Hawking radiation and all that, fantastic work. 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. 01:13:05.500 |
- That would have been a heck of a Nobel prize, 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 01:13:21.100 |
we've been unintentionally broadcasting our presence 01:13:23.780 |
for a hundred years since the development of radio and TV. 01:13:34.980 |
either already knows about us and, you know, doesn't care 01:13:42.860 |
But if there are ants on the sidewalk and you're walking by, 01:13:59.740 |
and know about them and have intentions of attacking them. 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. 01:14:44.060 |
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 01:15:09.460 |
ever since we figured out how to build nuclear weapons. 01:15:24.340 |
I would figure out, but that's why I'm always 01:15:34.460 |
You know, there is something in the human condition, 01:15:45.620 |
Goats, Bigfoot is a big fascination for folks. 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, 01:16:08.740 |
- You want to feel like there's something magical there. 01:16:30.500 |
His intuition was whoever figures out ball lightning 01:16:38.140 |
I decided there when I was like five years old or whatever 01:16:44.900 |
- That was like one of the first sort of sparks 01:16:48.980 |
Those mysteries, they capture your imagination. 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. 01:17:02.780 |
Because there's hundreds of thousands, if not millions, 01:17:17.620 |
Most of the scientific community kind of rolls their eyes 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? 01:17:38.300 |
They haven't brought us actual, tangible, physical evidence 01:17:42.540 |
with which experiments can be done in laboratories. 01:17:57.780 |
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 01:18:20.220 |
so I'm pretty confident he saw what he says he saw, 01:18:27.860 |
- One of the interesting psychological things 01:18:31.260 |
that worries me is that everybody in the Navy, 01:18:40.460 |
just kind of like pretended that nothing happened. 01:18:47.060 |
that's what makes me believe if aliens show up, 01:18:59.100 |
and use this opportunity to inspire the world. 01:19:10.180 |
say that whenever there is some good hard evidence 01:19:16.260 |
there's this kind of conspiracy that I don't like 01:19:20.220 |
that the US government will somehow hide the good evidence 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 01:19:50.500 |
"Extraordinary claims require extraordinary evidence." 01:20:02.060 |
On the other hand, a lot of the things that are seen 01:20:16.260 |
or maybe some of these pilots saw Soviet or Israeli 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 01:20:51.660 |
I don't categorically actually deny the possibility 01:20:55.620 |
that ships of some sort could have visited us 01:21:06.860 |
in a few million years are gonna be in the vicinity 01:21:10.940 |
We can even calculate which ones they're gonna be 01:21:15.140 |
So there's nothing that breaks any laws of physics 01:21:20.540 |
Just having Voyager or Pioneer fly by some star, 01:21:31.620 |
And then either zipping back to their home planet 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. 01:21:59.060 |
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. 01:22:09.180 |
I found the evidence to the degree that I investigated it 01:22:18.260 |
But I don't categorically deny the possibility 01:22:24.020 |
- Yeah, I mean, this is one of those phenomena 01:22:48.980 |
there'll be plenty of evidence for scientists to study. 01:23:00.500 |
I could see sort of some kind of a dumb thing, 01:23:11.460 |
maybe there's some kind of robot type of thingies 01:23:21.340 |
I feel like there'll be plenty of hard to dismiss evidence. 01:23:30.020 |
believe that the US government is not sufficiently competent 01:23:37.220 |
that will be revealed from this kind of thing 01:23:43.060 |
you can say maybe decades ago, but in modern times. 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, 01:24:06.020 |
But then I said, yes, in a sense, I'm an optimist, 01:24:09.980 |
because it means that we made it through the great filter. 01:24:16.100 |
in that I'm pessimistic about the possibility 01:24:25.860 |
But it may mean a good thing for our ultimate survival. 01:24:33.980 |
- But anyway, I think UFO research is interesting. 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. 01:25:02.780 |
- But it's just that you never get these reports 01:25:10.780 |
and you'd think we'd be the ones that are most likely, 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, 01:25:26.420 |
it's actually really difficult for scientists. 01:25:36.020 |
probably maybe over 1,000 emails on the topic of AGI. 01:25:45.580 |
people write to me, it's like, how can you ignore this, 01:25:51.860 |
that's going to achieve general intelligence. 01:25:56.740 |
And there's always just these large write-ups. 01:26:07.900 |
- It's very possible that you actually saw the UFO, 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. 01:26:36.540 |
when evolution in all of its richness is beautiful? 01:26:40.180 |
Who cares about a monkey that walks on two feet, 01:26:43.340 |
- In a sense, it's like there's a zillion decoys. 01:27:07.940 |
and I'm not saying the best UFO reports are of that nature. 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? 01:27:22.580 |
- And there's only so many scientists, so it's hard. 01:27:27.380 |
and you have to choose what problems you work on. 01:27:33.220 |
to kind of explore the idea of the expanding universe. 01:27:47.580 |
And the age of the universe is 13.7 billion years. 01:28:06.700 |
with ping pong balls and a rubber hose, a rubber band. 01:28:18.900 |
or more correctly, clusters of galaxies, expanding. 01:28:22.860 |
So, imagine light going from one cluster to another. 01:28:43.340 |
since the light that we are seeing from the early stages, 01:28:48.060 |
the so-called cosmic microwave background radiation, 01:28:57.220 |
That's how long it's taken that light to reach us. 01:29:03.300 |
the parts that it already traveled continue to expand. 01:29:14.140 |
'cause you're trying to get to your terminal, 01:29:25.140 |
That's why you get on one of these traveling walkways. 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 01:30:05.420 |
it would not be exceeding the speed of light. 01:30:07.980 |
The speed of light is a locally measured quantity. 01:30:25.140 |
But locally, it never was exceeding the speed of light. 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, 01:30:59.180 |
you can easily have them moving apart from one another 01:31:05.420 |
that were originally 400,000 kilometers from each other 01:31:14.220 |
Then suddenly this 400,000 kilometer distance 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 01:31:39.500 |
There's nothing in either special or general relativity 01:31:43.020 |
that prevents space itself from expanding faster 01:31:49.380 |
Einstein wouldn't have had a problem with a universe 01:31:56.300 |
- Yeah, I'm not sure I'm yet ready to deal emotionally 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. 01:32:15.180 |
- Could you, can we talk about the Big Bang a little bit? 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 01:32:39.900 |
Then regardless of how far back in time you go, 01:32:45.820 |
You can't turn a point suddenly into a shell, okay? 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. 01:33:02.060 |
And we don't know actually whether it was finite 01:33:05.720 |
I think personally that it was finite at the time, 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? 01:33:26.940 |
And by that I mean that if you were trying to measure, 01:33:53.860 |
That's what the inflation theory is all about. 01:34:02.860 |
along with Andre Linde at Stanford University 01:34:07.700 |
Alexei Starobinsky and others had similar sorts of ideas. 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 01:34:25.640 |
the amount of space remaining to be traversed 01:34:41.020 |
- That's one of the best definitions of infinity, 01:34:44.240 |
- That's one of the best sort of physical manifestations 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 01:35:03.320 |
wouldn't it be finite no matter how big it is? 01:35:07.760 |
you can't be outside and take a God-like slice of time. 01:35:19.320 |
what slice of time you're taking depends on your motion. 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. 01:35:57.360 |
And so it's not even clear what slices of time mean, 01:36:02.880 |
I know which end of the telescope to look through. 01:36:11.100 |
there'd be no way of seeing that it's a finite universe, 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. 01:36:38.620 |
So this is where it gets into a lot of speculation. 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. 01:36:55.100 |
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, 01:37:04.860 |
In other words, we have real testable physics 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 01:37:29.020 |
'cause a theory in science is really something 01:37:39.940 |
based on what we know about general relativity 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. 01:38:04.980 |
And yet there are these indirect ideas that stem forth. 01:38:17.860 |
But the more and more tests you have that it satisfies, 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 01:38:40.380 |
But you've satisfied 49 of the other testable predictions. 01:38:48.940 |
Now, a conventional condensed matter physicist 01:38:51.900 |
or someone who deals with real data in the laboratory 01:39:05.020 |
But it's not like we're coming up with these crazy ideas, 01:39:08.460 |
among them quantum fluctuations out of nothing, 01:39:14.180 |
you might say, "Well, you created a giant amount 01:39:16.060 |
of energy, but in fact, this quantum fluctuation 01:39:21.500 |
violates the conservation of energy, but who cares? 01:39:33.660 |
In a sense, the stuff of the universe has a positive energy, 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, 01:39:55.980 |
of kinetic energy, it's also gaining or losing, 01:40:03.300 |
of potential energy, so the total energy remains the same. 01:40:09.820 |
or other physicists say that energy isn't conserved 01:40:13.740 |
That's another way out of creating a universe 01:40:22.620 |
and although these extrapolations seem kind of outrageous 01:40:29.660 |
They're within the realm of what we call science already, 01:40:36.460 |
will be able to figure out a way to directly test 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. 01:40:58.380 |
from whatever the heck happened before the Big Bang. 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, 01:41:18.140 |
- But is it philosophically or practically possible 01:41:23.340 |
to detect signs that this was before the Big Bang, 01:41:29.100 |
everything we observe will, as we currently understand, 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. 01:42:02.860 |
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 01:42:19.140 |
because the experimental evidence favors it, right? 01:42:23.340 |
You know, there are various forms of string theory. 01:42:39.780 |
So my own feeling is probably these things don't survive. 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 01:42:59.500 |
That would leave a pattern, a temperature signature 01:43:03.100 |
in the cosmic microwave background radiation. 01:43:08.120 |
but in my opinion, it's not statistically significant 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 01:43:46.300 |
just a statistical fluctuation in their data. 01:43:50.060 |
No, they required five sigma, five standard deviations, 01:44:03.580 |
- Extraordinary claims require extraordinary evidence. 01:44:11.620 |
and the more evidence you need from independent ways 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 01:44:39.740 |
but more importantly, other independent techniques 01:44:49.780 |
and that started giving a much more complete picture 01:45:25.620 |
- Oh, gosh, you know, never in my wildest dreams as a kid 01:45:40.460 |
once you learn a little bit more about how science is done, 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, 01:45:53.960 |
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, 01:46:13.480 |
- So the couple of teams, the Supernova Cosmology Project 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, 01:46:36.780 |
- 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 01:46:52.700 |
and that's because galaxies have visible matter, 01:47:06.820 |
and they would tend to retard the expansion of the universe, 01:47:17.340 |
between Earth and the apple slows the apple down, 01:47:22.020 |
then the apple will someday stop and even come back, 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 01:47:37.300 |
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? 01:47:50.620 |
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 01:48:09.240 |
but in the last five billion years, it's been speeding up. 01:48:18.960 |
a little bit of the human story of the Nobel Prize. 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. 01:48:45.220 |
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, 01:48:52.620 |
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. 01:49:18.820 |
One of our teammates looked into it in a museum in Stockholm 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 01:49:47.580 |
- And it's not the way a lot of science is done now. 01:49:49.260 |
And you look at gravitational wave discovery, 01:50:19.220 |
right before October, the first week in October or whatever. 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 01:50:45.300 |
astrophysicists who weren't even on those two papers. 01:50:49.780 |
but other papers were written by other people, you know? 01:50:56.420 |
And none of those people was officially recognized. 01:51:01.700 |
You know, again, it was the thrill of doing the work 01:51:08.580 |
And, you know, we got to participate in Nobel week 01:51:13.980 |
I've known other physicists whose lives were ruined 01:51:21.020 |
and they felt strongly that they should have. 01:51:28.100 |
paper predicting the microwave background radiation. 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, 01:52:00.740 |
- Well, you know, there were the two team leaders, 01:52:04.940 |
and usually it's the team leaders that are recognized. 01:52:17.220 |
one of these people who just, you know, runs with things. 01:52:24.580 |
and then a postdoc as a so-called Miller Fellow 01:52:32.980 |
But you're, you know, you're largely a free agent, 01:52:43.660 |
and he measured the brightnesses of these distant supernovae 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. 01:53:10.300 |
but he died, I think, a year earlier in 2010, 01:53:19.180 |
but, you know, was I number four, five, six, seven? 01:53:27.700 |
I could make a very good case for you're in the three. 01:53:36.180 |
I mean, listen, it weighs on me a little bit, 01:53:46.740 |
the rethinking, like Time Magazine started doing, 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, 01:54:03.740 |
So like, or like the Oscar that you could say, 01:54:12.140 |
And the Breakthrough Prize in Fundamental Physics, 01:54:16.500 |
and Zuckerberg is involved in others as well, you know. 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. 01:54:45.700 |
shared the other half and didn't get to go to the ceremony. 01:54:50.140 |
I mean, for the gravitational waves, it was 1,000 people. 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, 01:55:06.620 |
The theoretical work by Peter Higgs and Englert 01:55:11.020 |
got recognized, but there was a troika of other people 01:55:37.020 |
Perhaps he should have perhaps gotten it with Hawking 01:55:41.700 |
The problem was Hawking radiation had not been detected, 01:55:51.940 |
And the observed data were already good enough 01:55:58.380 |
I mean, the latest results by Reinhard Genzel's group 01:56:03.380 |
of a star that's passing very close to the black hole 01:56:07.540 |
That's cool, and it adds additional evidence, 01:56:21.020 |
So clearly it was given for the original evidence 01:56:25.540 |
And that evidence is at least a decade old, you know? 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, 01:56:57.860 |
and that wouldn't have been a normal planet, sure. 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 01:57:22.100 |
for the development of physical cosmology to Peebles, 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. 01:57:43.300 |
but we wouldn't have had the result without him. 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. 01:57:59.740 |
where there's these hierarchical teams and stuff, 01:58:02.300 |
and it's hard for the little guy to have a say. 01:58:06.660 |
Whereas the team of astronomers led by Brian Schmidt 01:58:20.340 |
So it was sort of a culture, a style that I preferred, 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? 01:58:54.260 |
that if there are four or more people equally deserving, 01:59:22.900 |
conceived and built, so he deserves some credit. 01:59:31.260 |
And his initial reaction to the data that she showed him 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, 01:59:57.980 |
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, 02:00:16.900 |
'cause she passed away in December of 2015, I think. 02:00:19.700 |
It'll conduct this survey, large-scale survey, 02:00:26.580 |
So she's been recognized, but never with the Nobel Prize. 02:00:32.100 |
she did not let that consume her life either. 02:00:42.140 |
whereas in the case of pulsars and Jocelyn Bell, 02:00:57.980 |
as a fan of stories, that the travesty and the tragedy 02:01:06.100 |
is what makes the prize and similar prizes beautiful. 02:01:21.220 |
as so many people, athletes, give their whole life 02:01:32.100 |
like the little misfortunes that destroy entire dreams. 02:01:39.060 |
but it feels like that makes the entirety of it 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, 02:01:51.260 |
to youngsters today that science is still done 02:01:54.620 |
by white men with gray beards wearing white lab coats. 02:02:10.460 |
one elsewhere won the Nobel Prize in chemistry 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 02:02:39.820 |
that these were teams of people and they emphasize that. 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 02:03:12.100 |
and contributed greatly to the experimental setup as well. 02:03:17.540 |
but he was really good at bringing these two teams together 02:03:25.700 |
The National Science Foundation was gonna cut the funding 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 02:03:47.980 |
- And in that case, I mean, the coaches, the families, 02:03:54.020 |
and the coaches and the families of the athletes 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 02:04:59.820 |
and the ones that flew close to them, we forget. 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? 02:05:31.860 |
Wrote many of the words, or he's not as well-known, 02:05:51.180 |
But it's the unsung heroes in many cases, yeah. 02:06:05.220 |
were important in detecting this accelerating universe. 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. 02:06:25.420 |
that it'll become a red giant and incinerate Earth. 02:06:35.660 |
And that's not only exciting to watch from afar, 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, 02:07:17.780 |
by measuring the apparent brightness at its peak 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, 02:07:38.380 |
compared with their true intrinsic power or luminosity 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, 02:08:16.660 |
So we can do that for cars, we can do that for stars. 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, 02:08:31.180 |
What, how much variation is there between supernova 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, 02:09:00.500 |
They come from a weird type of a star called a white dwarf. 02:09:11.740 |
compressed into a volume just the size of Earth. 02:09:24.860 |
or anything like that, but this is just the name- 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. 02:09:44.620 |
So those two things mean that a lot of electrons 02:09:54.220 |
with just the random motions of particles inside the star. 02:10:04.540 |
except that if such a white dwarf is in a pair 02:10:17.140 |
roughly one and a half times the mass of our sun, 02:10:27.540 |
an Indian astrophysicist who figured this out 02:10:55.940 |
nevertheless, he too was human and had his faults. 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, 02:11:22.980 |
- Yeah, no matter what your advisor says, right? 02:11:25.060 |
So, or don't always pay attention to your advisor, right? 02:11:32.420 |
That doesn't mean never listen to your advisor, 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 02:12:05.820 |
being dissipated out of the star or, you know, whatever, 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 02:12:28.460 |
And that gets more of them sufficiently close together 02:12:41.860 |
an uncontrolled nuclear fusion reactor, right? 02:12:48.300 |
Our sun is a marvelous controlled fusion reactor. 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, 02:13:00.940 |
So this uncontrolled fusion reaction blows up a star 02:13:09.260 |
And you measure it to be almost the same in all cases, 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 02:13:23.460 |
might depend on the amount of trace heavier elements 02:13:35.060 |
or whether it's a relatively young white dwarf 02:13:51.540 |
the way it just, if all headlights or all candles 02:14:02.140 |
- Standard candles is what astronomers like to say, 02:14:12.620 |
- Yeah, you're calibratable, standardizable, calibratable. 02:14:15.100 |
You look at enough of them in nearby galaxies 02:14:23.660 |
and this is something that a colleague of mine, 02:14:25.060 |
Mark Phillips, did, who was on Schmidt's team, 02:14:33.500 |
more powerful type IAs decline in brightness, 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, 02:15:15.220 |
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, 02:15:32.180 |
the low-luminosity ones and the high-luminosity ones, 02:15:40.500 |
This showed that not all the IAs are the same, 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. 02:15:56.420 |
that showed this correlation between the light curve, 02:16:00.580 |
the brightness versus time, and the peak luminosity. 02:16:08.220 |
- How many type IAs are out there to use for data? 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. 02:16:53.820 |
'cause our galaxy is 100,000 light years across, 02:17:01.940 |
- And it gives birth to a bunch of other stars, I guess? 02:17:12.020 |
with other chemically enriched expanding gases, 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, 02:17:36.860 |
and if they get it wrong, I will retroactively fail them. 02:17:41.980 |
That, and if they don't know- - That's a student's 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, 02:18:04.060 |
they all came from stars, from nuclear reactions in stars, 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, 02:18:24.060 |
some of whose members then evolved and exploded, 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. 02:19:01.700 |
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. 02:19:16.580 |
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, 02:19:32.940 |
Obviously, that's personality dependent and all that. 02:19:37.500 |
but it's perhaps the greatest story ever told. 02:19:49.740 |
a greater story than even the existence of the universe, 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? 02:20:07.620 |
- So are they usually the thing that launches the, 02:20:14.200 |
I mean, I touch upon the subject earlier in my course, 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. 02:20:32.760 |
Some stars that are more massive can go somewhat beyond that. 02:20:39.020 |
this idea of the birth of the heavy elements, 02:20:47.260 |
weren't sufficient to make any significant quantities 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 02:21:08.820 |
So indeed, the supernova, my main area of interest, 02:21:17.460 |
- I saw that you got a chance to call Richard Feynman 02:21:31.660 |
and one of the deepest thinkers of all time, probably. 02:21:37.820 |
the physicist who had the single most intuitive understanding 02:22:09.220 |
One was general theory of relativity at the graduate level 02:22:17.820 |
And he had this very intuitive way of looking at things 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 02:22:44.700 |
then you probably don't understand it very well yourself, 02:22:58.300 |
And I've often found that in explaining things, 02:23:03.780 |
That's one reason I like to teach the introductory courses 02:23:08.980 |
that my explanations are lacking in my own mind. 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 02:23:20.220 |
If you could break apart what intuitive means, 02:23:28.460 |
How do you draw a mental picture or a picture on paper 02:23:37.660 |
which in what's called quantum electrodynamics, 02:23:40.460 |
a quantum field theory of electricity and magnetism, 02:23:45.620 |
an exchange of photons between charged particles. 02:23:50.980 |
if the particles are at rest relative to one another. 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 02:24:09.900 |
and he had a set of rules of what to do at the vertex. 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 02:24:41.580 |
for explaining really what quantum electrodynamics 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 02:24:58.820 |
Is there a simple way you can understand this? 02:25:00.900 |
And in the path that a particle follows even, 02:25:09.900 |
at least for a baseball or something like that, 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 02:25:35.820 |
they're the ones that are more likely to be followed. 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. 02:25:54.980 |
But if you do the mathematics associated with that, 02:26:02.700 |
- So you're also, I mean, you're widely acknowledged as, 02:26:07.460 |
as being one of the greatest educators in the world. 02:26:16.100 |
Is there something about being a teacher that you-- 02:26:21.000 |
when you have students who are really into it. 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, 02:26:43.900 |
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 02:26:53.980 |
And in fact, in many cases, they were quite good questions. 02:27:00.620 |
And I remember one time in particular when he said, 02:27:08.900 |
Aren't the rest of you curious about what I'm saying? 02:27:18.280 |
No, you guys are too scared to ask these questions 02:27:23.220 |
So he actually invited us to lunch a couple of times 02:27:29.820 |
with one of the greatest thinkers of 20th century physics. 02:28:04.500 |
So yeah, and the question is the ultimate form of curiosity. 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? 02:28:33.460 |
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, 02:28:47.240 |
and do those things, it can give you meaning. 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." 02:29:07.740 |
No, it just has to be something that gives you meaning, 02:29:15.040 |
that gives you a good feeling about what you did. 02:29:27.100 |
that give us meaning and a feeling of satisfaction. 02:29:33.580 |
You cared for someone who was terminally ill. 02:29:44.360 |
You read a lot of books, if that's what you wanted to do, 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, 02:30:00.380 |
where you can't travel the world or whatever, 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, 02:30:22.380 |
and now we're two apes asking about the meaning of life. 02:30:45.360 |
It's a way that the universe found of knowing, 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 02:31:04.220 |
about the rest of the universe or even their origins. 02:31:10.540 |
that has no conscience, has no ability to think, 02:31:20.300 |
And I'm not saying we're the epitome of all life forever, 02:31:29.500 |
the evidence suggests that we are the epitome 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 02:32:16.180 |
It's this that gives me the potential for meaning, right? 02:32:27.580 |
and eventually we've built telescopes to look back at it, 02:32:44.140 |
And this is one of the multiverse sort of things. 02:32:54.820 |
like the mass ratio of the proton and the neutron. 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, 02:33:14.700 |
let alone bacteria, paramecia, slugs, and humans, okay? 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 02:33:51.580 |
And if there were only one, and maybe there is only one, 02:33:57.860 |
- We're lucky, but I actually think there are lots and lots, 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, 02:34:11.300 |
that are conducive to the development of complexity 02:34:19.820 |
- I don't think there's a better way to end it, Alex. 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 02:34:27.460 |
- For the honor of having been asked to do this. 02:34:33.220 |
with Alex Filippenko, and thank you to our sponsors. 02:34:36.660 |
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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. 02:35:34.680 |
Thank you for listening, and hope to see you next time.