Lex Fridman Podcast - #137 – Alex Filippenko: Supernovae, Dark Energy, Aliens & the Expanding Universe

Starting point is 00:00:00 The following is a conversation with Alex Filippenko, an astrophysicist and professor of astronomy from Berkeley. He was a member of both the Supernova Cosmology Project and the Hizzy Supernova Search Team, which used observations of the extra galactic supernova to discover that the universe is accelerating, and that this implies the existence of dark energy. This discovery resulted in the 2011 Nobel Prize for Physics. Outside of his groundbreaking research, he is a great science communicator and is one of the most widely admired educators in the world. I really enjoyed this conversation and I'm sure Alex will be back again in the future. Quick mention of each sponsor, followed by some thoughts related to the episode.

Starting point is 00:00:47 Nuro, the maker of functional, sugar-free gum, and mince that I used to give my brain a quick caffeine boost. Better help, an online therapy with a licensed professional. Masterclass, online courses that I enjoy from some of the most amazing humans in history and cash app. The app I use to send money to friends. Please check out these sponsors in the description to get a discount and to support this podcast. As a side note, let me say that as we talk about in this conversation, the objects that populate the universe are both awe-inspiring and terrifying in their capacity to create and

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Starting point is 00:06:50 we have evidence that the matter density is sufficiently low that the universe will expand forever, but not only that there's this weird repulsive effect we call it dark energy for a want of a better term and it appears to be accelerating the expansion of the universe. So if that continues, the universe will expand forever, but it need not necessarily continue. It could reverse sign, in which case the universe could, in principle, collapse at some point in the far, far future. So like, in terms of investment advice, if you were to give me and then to bet all my money on one or the other, where does your intuition currently lie? Well, right now I would say

Starting point is 00:07:30 that it would expand forever because I think that the dark energy is likely to be just quantum fluctuations of the vacuum. The vacuum zero energy state is not a state of zero energy, that is the ground state is a state of some elevated energy which has a repulsive effect to it. And that will never go away because it's not something that changes with time. So if the universe is accelerating now, it will forever continue to do so. And yet, I mean, you so effortlessly mentioned dark energy, do we have any understanding of what the heck that thing is? Well, not really, but we're getting progressively better observational constraints. So you know, different theories of what it might be, predict different sorts of behavior

Starting point is 00:08:17 for the evolution of the universe. And we've been measuring the evolution of the universe now. And the data appear to agree with the predictions of a constant density vacuum energy, a zero point energy. But one can't prove that that's what it is because one would have to show that the numbers, that the measured numbers agree with the predictions to an arbitrary number of decimal places. And of course, even if you've got 8, 9, 10, 12 decimal places, what if in the 13th one,

Starting point is 00:08:50 the measurements significantly differ from the prediction? Then the dark energy isn't this vacuum state, ground state energy of the vacuum. And so then it could be some sort of a field, some sort of a new energy, a little bit like light, like electromagnetism, but very different from light, that fills space. And that type of energy could, in principle, change in the distant future,

Starting point is 00:09:20 it could become gravitationally attractive for all we know. There is a historical precedent to that, and that is that the inflation with which the universe began when the universe was just a tiny blink of an eye old, a trillionth of a trillionth of a trillionth of a second, the universe went, whoosh, it exponentially expanded. That dark energy-like substance, we call it the inflaton, that which inflated the universe, later decayed into more or less normal, gravitationally attractive matter. So the exponential, early expansion of the universe did transition to a deceleration, which then dominated the universe for about nine billion years.

Starting point is 00:10:02 And now this small amount of dark energy started causing an acceleration about five billion years ago. And whether that will continue or not is something that we'd like to answer, but I don't know that we will anytime soon. So there could be this interesting field that we don't yet understand that's morphing over time, that's changing the way the universe is expanding. I mean, it's funny that you were thinking through this rigorously like an experimentalist. Yeah, but what about like the fundamental physics of dark energy? Is there any understanding of what the heck it is, or is this the kind of the god of the gaps or the field of the gaps?

Starting point is 00:10:50 So like, there must be something there because of what we're observing. I'm very much a person who believes that there's always a cause, you know, there are no miracles of a supernatural nature, okay? no miracles of a supernatural nature. Okay. So, I mean, there are two broad categories. Either it's the vacuum zero point energy

Starting point is 00:11:13 or it's some sort of a new energy field that pervades the universe. The latter could change with time. The former, the vacuum energy cannot. So if it turns out that it's one of these new fields, and there are many, many possibilities, they go by the name of, you know, quintessence and things like that, but there are many categories of those sorts of fields.

Starting point is 00:11:36 We try with data to rule them out by comparing the actual measurements with the predictions, and some have been ruled out, but many, many others remain to be tested. And the data just have to become a lot better before we can rule out most of them and become reasonably convinced that this is a vacuum energy. So there is hypotheses for different fields, like with names and stuff like that? Yeah, you know, generically quintessence like the Aristotelian fifth essence, but there are many, many versions of quintessence.

Starting point is 00:12:10 There's K essence. There's even ideas that, you know, this isn't something from within this dark energy, but rather there are a bunch of, say, bubble universes surrounding our universe. And this whole idea of the multiverse is not some crazy madmen type idea anymore. It's, you know, real card carrying physicists are seriously considering this possibility of a multiverse. And some types of multiverse could have, you know, a bunch of bubbles on the outside, which gravitationally act outward on our bubble because gravity or gravitons, the quantum particle that is thought

Starting point is 00:12:47 to carry gravity is thought to traverse the bulk, the space between these different little bubble membranes and stuff. And so it's conceivable that these other universes are pulling outward on us. That's not a favored explanation right now, but really nothing has been ruled out. No class of models has been ruled out completely. Certain examples within classes of models have been ruled out. But in general, I think we still have really a lot to learn about what's causing this observed acceleration of the expansion of the universe, be it dark energy or some forces from the outside or perhaps, you know, I guess it's conceivable that, and sometimes I wake

Starting point is 00:13:34 up in the middle of the night screaming, the dark energy that which causes the acceleration and dark matter, that which causes galaxies and clusters of galaxies to be bound, gravitationally, even though there's not enough visible matter to do. So maybe these are our 20th and 21st century, Tullamaic epicycles. So Tullamae had a geocentric and Aristotelian view of the world. Everything goes around Earth. But in order to explain the backward motion of planets

Starting point is 00:14:06 among the stars that happens every year or two, or sometimes several times a year for Mercury and Venus, you needed the planets to go around in little circles called epicycles, which themselves then went around Earth. And in this part of the epicycle where the planet is going in the direction opposite to the direction of the overall epicycle, it can appear in projection to be going backward among the stars, so-called retrograde motion. And it was a brilliant mathematical scheme. In fact, he could have added epicycles on top of epicycles, and reproduce the observed positions of planets to arbitrary accuracy. And this is really the beginning of what we now call Fourier analysis, right? Any periodic function can be represented by a sum of signs and cosines of different periods, amplitudes, and phases. So it could have worked arbitrarily well. But other data, you know, show that in fact,

Starting point is 00:15:08 Earth is going around the Sun. So our dark energy and dark matter, just these band-aids that we now have to try to explain the data, but they're just completely wrong. That's a possibility as well. And as a scientist, I have to be open to that possibility, as an open-minded scientist. How do you put yourself in the mindset of somebody that or majority of the scientific community or majority of people believe that the earth,

Starting point is 00:15:36 everything rotates around earth? How do you put yourself in that mindset and then take a leap that mindset and then take a leap to propose a model that the sun is, in fact, at the center of the solar system. Sure. I mean, so that puts us back in the shoes of Copernicus, right? 500 years ago, where he had this philosophical preference for the Sun being the dominant body in what we now call the solar system. The observational evidence in terms of the measured positions of planets was not better explained by the Heliosentric Sun-centered system. It's just that, you know, Copernicus saw that the sun is the source of all our light and heat. Oh, wow. And he had, you know, he knew from other studies that it's far away. So the fact that it appears as big as the moon means it's actually way, way bigger. Because even at that time, it was known that the sun is much farther away than the moon. So, you know, he just felt, wow,

Starting point is 00:16:42 it's big. It's bright. What if it's the central thing? But the observed positions of planets at the time in the early to mid-16th century under the Heliosentric system was not a better match, at least not a significantly better match than Tolemies system, which was quite accurate and lasted 1500 years. Yeah. Yeah. That's so fascinating to think that the philosophical

Starting point is 00:17:11 predispositions that you bring to the table are essential. So like you have to have a young person come along that has a weird infatuation with the sun. Yeah. That that almost philosophically is like, however they're're upbringing is they're more ready for whatever the more the simpler answer is. Right. Oh, that's kind of sad. It's sad from an individual the Senate of a perspective because then that means like me, the user scientist, you're stuck with whatever the Heg philosophies you brought to the table, you might be almost completely unable to think outside this particular

Starting point is 00:17:52 box you've built. Right. This is why I'm saying that, you know, as an objective scientist, one needs to have an open mind to crazy sounding new ideas. Exactly. And, you know, even Copernicus was very much a man of his time and dedicated his work to the Pope, he still used circular orbits.

Starting point is 00:18:11 The sun was a little bit off-centre, it turns out. And a slightly off-centre circle looks like a slightly eccentric elliptical orbit. So then when Kepler, in fact, showed that the orbits are actually in general ellipses, not circles, the reason that, you know, he needed to co-brahe his really great data to show that distinction was that a slightly off-center circle is not much different from a slightly eccentric ellipse. And so there wasn't much difference between Kepler's view and Copernicus's view and Kepler needed the better data to co-Brasd data. And so that's again a great example of science and observations and experiments working together with hypotheses and they kind of bounce off each other.

Starting point is 00:19:05 They play off of each other, and you continually need more observations. And it wasn't until Galileo's work, around 1610, that actual evidence for the Helios-centric hypothesis emerged. It came in the form of Venus, the planet Venus, going through all of the possible phases, from new to crescent to quarter to gibbous to full to waning gibbous third quarter waning crescent and then new again. It turns out in the Tallahmei system with Venus between earth and the sun, but always roughly in the direction of the sun, you could only get the new and crescent phases of Venus. But the observation showed a full set of phases. And moreover, when Venus was gibbous or full, that meant it was on the far

Starting point is 00:19:53 side of the sun, that meant it was farther from Earth than when it's crescent, so it should appear smaller, and indeed it did. So that was the nail and the coffin in a sense. And then Galileo's other great observation was that Jupiter has moons going around it, the four Galilean satellites, and even though Jupiter moves through space, so too do the moons go with it. So first of all, Earth is not the only thing that has other things going around it. And secondly, Earth could be moving as Jupiter does. And things would move with it. We wouldn't fly off the surface and our moon wouldn't be left behind

Starting point is 00:20:32 and all this kind of stuff. So that was a big breakthrough as well, but it wasn't as definitive in my opinion as the faces of Venus. Perhaps I'm revealing my ignorance, but I didn't realize how much data they were working with. So there's, so it wasn't Einstein or Freud thinking in theories. It was a lot of data and you're playing with it and seeing how to make sense of it. So it isn't just coming up with completely abstract thought experiments. Yeah. It's looking at the data.

Starting point is 00:21:06 Sure, and you're looking at the Newton's great work, right? The Principia, it was based in part on Galileo's observations of balls rolling down inclined planes, supposedly falling off the leaning tower of Pisa, but that's probably apocryphal. In any case, the inquisition actually did, or the Roman Catholic Church, did history a favor, not that I'm condoning them, but they placed Galileo under house arrest. And that gave Galileo time to publish,

Starting point is 00:21:37 to assemble and publish the results of his experiments that he had done decades earlier. It's not clear he would have had time to do that, you know, had he not been under house arrest. And so Newton of course very much used Galileo's observations. Let me ask the old Russian overly philosophical question about death. So we're talking about the expanding universe.

Starting point is 00:22:04 Sure. How do you think human civilization will come to an end if we avoid the, uh, the near term issues we're having? Uh, will it be our sun burning out? Will it be comets? Oh, okay. Will it be, uh, what is it? Yeah. Do you think we have a shot at reaching the heat death of the universe? Yeah. So we're going to leave out the anthropogenic

Starting point is 00:22:32 causes of our potential destruction, which I actually think are greater than the celestial causes. So if we get lucky, and intelligent, I don't know. Yeah. So no way will we as humans reach the heat death of the universe. I mean, it's conceivable that machines, which I think will be our evolutionary descendants, might reach that, although even they will have less and less energy with which to work as time progresses because eventually, even the lowest mass stars burn out, although it takes them trillions of years to do so. So, the point is that certainly on Earth, there are other celestial threats, existential threats, comets exploding stars, the sun burning out. So So we will definitely need to move away from our solar system to other solar systems.

Starting point is 00:23:30 And then, you know, the question is, can they keep on propagating to other planetary systems sufficiently long? In our own solar system, the sun burning out is not the immediate existential threat. That will happen in about, you know, five billion years when it becomes a red giant. Although I should hasten to add that within the next one or two billion years, the sun will have brightened enough that unless their compensatory atmospheric changes, the oceans will evaporate away. And you need much less carbon dioxide for the temperatures to be maintained roughly at their present temperature and plants wouldn't like that very much. So you can't lower the carbon dioxide content too much. So

Starting point is 00:24:19 so within one or two billion years, probably the oceans will evaporate away. But on a sooner time scale than that, I would say an asteroid collision leading to a potential mass extinction, or at least an extinction of complex beings, such as ourselves, that require quite special conditions, unlike cockroaches and amoebas, you know, to survive. You know, One of these civilization changing asteroids is only one kilometer or so in diameter and bigger. And a true mass extinction event is 10 kilometers or larger. Now it's true that we can find and track the orbits of asteroids that might be headed toward Earth. And if we find them 50 or 100 years before they impact us, then clever applied physicists and engineers can figure out ways to deflect them.

Starting point is 00:25:11 But at some point, you know, some comment will come in from the deep freeze of the solar system. And there we have very little warning months to a year. What's the deep freeze? Sorry to. Oh, the deep freeze is sort of out beyond Neptune. There's this thing called the Kuiper belt. And it consists of a bunch of, you know, dirty ice balls or icy dirt balls. It's the source of the comets that occasionally come close to the sun. And then there's a even bigger air called the scattered disc, which is sort of a big donut surrounding the solar system way out there from which other comets come. And then there's the Ork cloud, W-O-R-T after Jan Ork, a Dutch astrophysicist. And it's the better part of a light year away from the Sun, so a good fraction of the distance to the nearest

Starting point is 00:25:59 star. But that's like a trillion or 10 trillion Comment like objects that occasionally get disturbed by a passing star or whatever and most of them go flying out of the solar system but some go toward the Sun and They come in with little warning, you know by the time we can see them they're only a year or two away from us and more over Not only is it hard to Determine their trajectories, sufficiently accurately, to know whether they'll hit a tiny thing like Earth, but outgassing from the comet of gases, you know, when the ice is sublimated, that outgassing can change the trajectory

Starting point is 00:26:40 just because of conservation of momentum, right? It's the rocket effect. Gases go out in one direction, the object moves in the other direction. And so, since we can't predict how much outgassing there will be in an exactly what direction, because these things are tumbling and rotating and stuff, it's hard to predict the trajectory with sufficient accuracy to know that it will hit. And you certainly don't want to deflect a comment that would have missed, but you thought it was gonna hit, and end up having it hit.

Starting point is 00:27:09 That would be like the ultimate Charlie Brown, you know, goat instead of trying to be the hero, right? He ended up being the goat. What would you do if it seemed like in a matter of months that there is some non-zero probability, maybe a high probability that there will be a collision. From a scientific perspective, from an engineering perspective, I imagine you would actually be in the room of people deciding what to do.

Starting point is 00:27:38 What... Philosophically, too. It's a tough one, right? Because if you only have a few months, that's not much time in which to deflect it. Early detection and Early action or key because when it's far away, you only have to deflect it by a tiny little angle Yeah, and then by a time it reaches us the perpendicular motion is big enough to you know To miss earth.

Starting point is 00:28:05 All you need is one radius or one diameter of the earth, right? That actually means that all you would need to do is slow it down so it arrives four minutes later or speed it up so it arrives four minutes earlier and earth will have moved through one radius in that time. So it doesn't take much, but you can imagine if a thing is about to hit you, you have to deflect it 90 degrees or more, right? And you don't have much time to do so and you have to slow it down or speed it up a lot

Starting point is 00:28:35 if that's what you're trying to do to it. And so decades is sufficient time, but months is not sufficient time. So at that point, I would think the name of the game would be to try to predict where it would hit. And if it's in a heavily populated region, try to start an orderly evacuation perhaps. But you know, that might cause just so much panic that I'm, how would you do with, with New York City or Los Angeles or something like that, right? I might have, I might have a different opinion a year ago. I'm a bit, this heartened by, you know, in the movies, the, there's always extreme competence from the government. Competence, yeah. Competence, yeah. But we expect extreme incompetence.

Starting point is 00:29:26 If anything, right? Yes. Now, so I'm quite disappointed. But you're sort of from a medical perspective, I think you're saying they're an scientific one. It's almost better to get better and better, maybe telescopes and data collection to be able to predict the movement of these things. We're like, come up with totally new technologies. Like you can imagine actually sending out like probes out there to be able to sort of almost have a little finger sensors throughout our solar system to be able to detect stuff. Well, that's right.

Starting point is 00:29:58 Yeah, monitoring the asteroid belt is very important. And 99% of the so-called near-earth objects ultimately come from the asteroid belt. And so there we can track the trajectories. And even if there's a close encounter between two asteroids which deflects one of them toward Earth, it's unlikely to be on a collision course with Earth in the immediate future. It's more like tens of years. So that gives us time. But we would need to improve our ability to detect the objects that come in from a great distance. Unfortunately, those are much rare.

Starting point is 00:30:32 The comets come in, you know, 1% of the collisions perhaps are with comets that come in without any warning hardly. And so, so that might be more like, you know, a billion or two billion years before one of those hits us. So maybe we have to worry about the sun getting brighter on that time scale. I mean, there's the possibility that a star will explode near us in the next couple of billion years, but over the course of the history of life on earth the estimates are that

Starting point is 00:31:12 maybe only one of the mass extinctions You know, it was caused by a star blowing up in particular a Special kind called a gamma ray burst and the I think it's the Ordovician, Solarian, Solurian, Ordovician, Solurian extinction, 420 or so,

Starting point is 00:31:32 440 million years ago, that is speculated to have come from one of these particular types of exploding stars called gamma ray bursts. But even there, the evidence is circumstantial. So those kinds of existential threats are reasonably rare. The greater danger, I think, is civilization changing events, where it's a much smaller asteroid, which those are harder to detect, or a giant solar flare that shorts out the grid in all of North America. Let's say, now, astronomers are monitoring the Sun 24-7 with various satellites, and

Starting point is 00:32:14 we can tell when there's a flare or a coronal mass ejection. We can tell that in a day or two, a giant bundle of energetic particles will arrive and twang the magnetic field of Earth and send all kinds of currents through long distance power lines, and that's what shorts out the transformers and transformers are down the grid before the big bundle of particle hits, then we will have mitigated much of this. Now, for a big enough bundle of particles, you can get short circuits even over small distance scales, so not everything will be saved, but at least the whole grid might not go out. So, again, astronomers, I like to say, support your local astronomers, they may help someday save humanity by telling the power companies to shut down the grid, finding

Starting point is 00:33:13 the asteroid 50 or 100 years before it hits, then having clever physicists and engineers deflect it. So many of these cosmic threats, cosmic existential threats, we can actually predict and do something about or observe before they hit and do something about. So it's terrifying to think that people would listen to this conversation. It's like when you listen to Bill Gates talk about pandemics in his TED talk a few years ago Yeah, and realizing we should have supported our local astronomer more. Well, I don't know whether it's more because as I said, I actually think human-induced threats or things that occur naturally on Earth, either a natural pandemic or perhaps, you know, a bioengineering type pandemic, or, you know, something like a super volcano,

Starting point is 00:34:02 right? Yeah. Or something like a super volcano, right? There was one event, Tobii, I think it was 70 plus thousand years ago, that caused a gigantic decrease in temperatures on Earth because it sent up so much so that it blocked the Sun, right? It's the nuclear winter type disaster scenario that some people including Carl Sagan talked about decades ago. But we can see in the history of volcanic eruptions, even more recently in the 19th century, Tambora and other ones. You look at the record and you see rather large dips in temperature associated with massive

Starting point is 00:34:38 volcanic eruptions. Well, these super volcanoes, one of which, by the way, exists under Yellowstone, you know, in the central US. I mean, it's not just one or two states. It's a gigantic region. And there's controversy as to whether it's likely to blow any time in the next 100,000 years or so. But that would be perhaps not a mass extinction because you really need to, or perhaps not a complete existential threat because you have to get rid of sort of the very last humans for that. But at least getting rid of, you know, killing off so many humans, truly billions and billions of humans, the one that there have been ones tens of thousands of years ago, including

Starting point is 00:35:21 this one, Toby, I think it's called, where it's estimated that the human population was down to 10,000 or 5,000 individuals, something like that, right? If you have a 15 degree drop in temperature over quite a short time, it's not clear that even with today's advanced technology, we would be able to adequately respond, at least for the vast majority of people. Maybe some would be in these underground caves where you'd keep the president and a bunch of other important people, you know, but the typical person is not going to be protected when all of agriculture is cut off, right?

Starting point is 00:35:58 And it could be hundreds of millions or billions of people starving to death. Exactly. That's right. They don't all die immediately, but they use up their supplies or again, the electrical grid. First of toilet paper. There you go. Dash that toilet paper, you know, or the electrical grid. I mean, imagine North America without power for a year, right? I mean, we've become so dependent, we're no longer the cave people. They would do just fine, right? I mean, we've become so dependent. We're no longer the cave people. They would do just fine, right? What do they care about the electrical grid? Right? What do they care about agriculture? Their hunters and gatherers. But we now have become so used to our way of life

Starting point is 00:36:38 that the only real survivors would be those rugged individualists who live somewhere out in the forest or in a cave somewhere completely independent of anyone else. Yeah, I've recently I recommended it's totally new to me this kind of survivalist folks, but there's a few there's a lot of shows of those, but I've saw one on Netflix and I started watching them and there's they make a lot of sense. They reveal to you how dependent we are on all aspects of this beautiful systems we human have built. And how fragile they are. Incredibly fragile. And yeah, this whole conversation is making me realize how lucky we are. Oh, we're incredibly lucky, but we've set ourselves up to be very, very fragile, and we are intrinsically complex biological creatures that accept for the fact that we have brains

Starting point is 00:37:33 and minds with which we can, you know, try to prevent some of these things or respond to them. We as a living organism require quite an arrow set of conditions in order to survive. You know, we're not cockroaches. We're not going to survive a nuclear war. So we're kind of this beautiful dance between, we've been talking about astronomy that astronomy, the stars, like inspires everybody. And at the same time, there's this pragmatic aspect that we're talking about. And so I see space exploration as the same kind of way that it's reaching out to other planets,

Starting point is 00:38:13 reaching out to the stars. This really beautiful idea. But if you listen to somebody like Elon Musk, he talks about space exploration as very pragmatic. Like we have to, if we have to be, he has this ridiculous way of sounding like an engineer about it, which is like, it's obvious we need to become a multi planetary species if we were to survive long term. So maybe both philosophically in terms of beauty and in terms of practical. What's your thoughts on space exploration, on the challenges of it, on how much we should be investing in

Starting point is 00:38:52 it, and on a personal level, like how excited you are by the possibility of going to Mars, colonizing Mars, and maybe going outside the solar system. Yeah, great question. There's a lot to unpack there, of course. Humans are by their very nature, explorers, pioneers. They want to go out, climb the next mountain, see what's behind it, explore the option depths, explore space. This is our destiny to go out there. And of course, from a pragmatic perspective. Yes, we need to

Starting point is 00:39:28 Plant our seeds elsewhere really because things could go wrong here on earth now some people say That's that's an excuse to not take care of our planet that well we say we're elsewhere And so we don't have to take good care of our planet. No, you know, we should take the best possible care of our planet. We should be cognizant of the potential impact of what we're doing. Nevertheless, it's prudent to have us be elsewhere as well. So in that regard, I actually agree with Elon. It'd be good to be on Mars. That would be at another place for us to from which to, you know, explore. Would that be a good, would that be a good next step? Well, that's the good, it's a good next step.

Starting point is 00:40:09 I have to happen, I happen to disagree with them as to how quickly it will happen. Right. I mean, I think he's very optimistic. Now, you need visionary people like Elon to get people going and to inspire them. I mean, look at the success he's had with multiple companies. So maybe he gives this very optimistic timeline in order to be them. I mean, look at the success he's had with multiple companies. So maybe he gives this very optimistic timeline in order to be inspirational to those who are going out there. And certainly his success with, you know, the rocket that is reusable because it landed upright and all that. I mean, you know, what, that's a game changer. It's

Starting point is 00:40:40 sort of like every time you flew from San Francisco to Los Angeles, you discard the airplane, right? I mean, that's crazy, right? So that's a game changer. But nevertheless, the time scale over which he thinks that there could be a real thriving colony on Mars, I think, as far to optimistic. What's the biggest challenges to you? One is just getting rockets, not rockets, but people out there and two is the colonization. Do you have thoughts about this? The challenges of this kind of prospect? Yeah, I haven't thought about it in great detail other than recognizing that Mars is a harsh environment. You don't have much of an atmosphere there. You've got less than a percent of Earth's atmosphere. So you'd need to build some sort of a dome right away, right? And that would take time. You need to melt the water that's

Starting point is 00:41:32 in the permafrost or have canals dug from which you transport it from the polar ice caps. You know, I was reading recently in terms of like what's the most efficient source of nutrition for humans that were to live on Mars and People should look into this, but it turns out to be insects insects. Yeah, yeah So you want you want to build giant colonies of insects, right? And he's just be eating it. He's have a lot of protein a lot of protein and they're easy to Grow like you can think of him as farming right And they're easy to grow, like you can think of them as farming. Right.

Starting point is 00:42:05 But it's not going to be as easy as growing a whole plot of potatoes, like in the movie The Martian, you know, or something, right? It's not going to be that easy. But, you know, so there's this thin atmosphere. It's got the wrong composition. It's mostly carbon dioxide. They're these violent dust storms. The temperatures are generally cold.

Starting point is 00:42:26 You'd need to do a lot of things. You need to terraform it basically in order to make it nicely livable without some dome surrounding you. And if you insist on a dome, well, that's not gonna house that many people, right? Well, so let's look briefly then, we're looking for a new apartment to move into right so let's look outside the solar system Do you think you've you've spoken about exoplanets as well? Do you think there's

Starting point is 00:42:55 Possible homes out there for us outside of our solar system? There are lots and lots of homes possible homes. I mean there there's a Planetary system around nearly every star you see in the sky. And one in five of those is thought to have a roughly earth-like planet. And that's a relative to the new discovery. Yeah, it's a new discovery. I mean, that's the Kepler satellite, which was flying around above Earth's atmosphere, was able to monitor the brightness of stars with exquisite detail, and they could detect planets crossing the line of sight between us and the star thereby

Starting point is 00:43:31 dimming its light for a short time, ever so slightly. And it's amazing. So there are now thousands and thousands of these exoplanet candidates of which something like 90% are probably genuine exoplanets. And you have to remember that only about 1% of stars have their planetary system oriented adjon to your line of sight, which is what you need for this transit method to work, right? Some arbitrary angle won't work and certainly perpendicular to your line of sight. That is in the plane of the sky won't work because the planet is orbiting the star and never crossing your line of sight. So the

Starting point is 00:44:11 fact that you know they found planets orbiting about 1% of the stars that they looked at in this field of 150 plus thousand stars, they found planets around 1%. You then multiply by the inverse of 1%, which is, you know, 1% is about how many, what the fraction of the stars that have their planetary system oriented the right way. And that already, back of the envelope calculation, tells you that a border 50 to 100% of all stars have planets, okay, and then they've been finding these Earth-like planets, etc., etc. So there are many potential homes. The problem is getting there, okay? So then a typical bright star, serious, the brightest star in

Starting point is 00:44:59 the sky, maybe not a typical bright star, but it's 8.7 light years away. Okay, so that's, that means the light took 8.7 years to reach us. We're seeing it as it was about nine years ago. Okay. So then, you know, you ask how long would a rocket take to get there at Earth's escape speed, which is 11 kilometers per second. It turns out it's about a quarter of a million years. Now that's 10,000 generations. Let's say a generation of humans is 25 years.

Starting point is 00:45:35 You'd need this colony of people that is able to sustain itself, all their food, all their waste disposal, all their water, all the recycling of everything. For 10,000 generations, they have to commit themselves to living on this vehicle, right? I just don't see it happening. What I see potentially happening, if we avoid self-destruction, intentional or unintentionally here on earth, is that machines will do it. Robots that can essentially hibernate. They don't need to do much of anything for a long, long time as they're traveling. And moreover, if some energetic charge particles, some cosmic ray hits the circuitry, it fixes itself, right?

Starting point is 00:46:19 Machines can do this. I mean, it's a form of artificial intelligence. You just tell the thing, fix yourself, basically. And then when you land on the planet, start producing copies of yourself. Initially, from materials that perhaps center, you just have a bunch of copies there, and then they set up factories with which to do this. I mean, this is very, very futuristic, but it's much more feasible, I think, than sending flesh and blood over interstellar distances, a quarter of a million years to even the nearest stars. You're subject to all kinds of charge particles and radiation. You have to, you know, shield yourself really well. That's, by the way, one of the problems of going to Mars is that it's not a three day journey like going to the moon.

Starting point is 00:47:07 You're out there for the better part of a year or two and you're exposed to lots of radiation. Yeah, which typically doesn't do well with living tissue, right? Or living tissue doesn't do well with the radiation. And the hope is that the robots, the AI systems, might be able to carry the fire of consciousness or whatever makes us humans, like a little drop of whatever makes us humans so special, not to be too poetic about it. No, but I like being poetic about it because it's an amazing question. You know, is there something beyond just the bits, the ones and zeros to us? You know, it's an interesting question. I like to think that there isn't anything and that how beautiful it is that our thoughts,

Starting point is 00:47:57 our emotions, our feelings, our compassion all come from these ones and zeros, right? That to me actually is a beautiful thought and the idea that machines, silicon-based life effectively could be our natural evolutionary descendants not from a DNA perspective, but they are our creations and they then carry on. That to me is a beautiful thought in some ways, but others find it to be a horrific thought. So that's exciting to you. It is exciting to me is a beautiful thought in some ways, but others find it to be a horrific thought. So that's exciting to you.

Starting point is 00:48:26 It is exciting to me as well. Yeah, because to me, from a purely an engineering perspective, it's, I believe it's impossible to create like whatever systems we create that take over the world. It's impossible for me to imagine that those systems will not carry some aspect of what makes humans beautiful. So like that, a lot of people have these kind of paperclip ideas that will build machines

Starting point is 00:48:54 that are cold inside or philosophers call them zombies. That naturally, the systems that will outcompete us on this earth will be cold and non-conscious, not capable of all the human emotions and empathy and compassion and love and hate, the beautiful mix of what makes us human. To me, intelligence requires all of that. So in order to out compete humans, you better be good at the full picture. Right. So artificial general intelligence in my view encompasses a lot of these attributes that you just talked about. I tend to be like curiosity, inquisitiveness, you know, right? It might look very different than us humans, but it will also be much more able to survive

Starting point is 00:49:49 the onslaught of existential threats that either we bring upon ourselves or don't anticipate here on Earth, or that occasionally come from beyond. And there's nothing much we can do about a supernova explosion that just suddenly goes off. Really, if we want to move to other planets outside our solar system, I think realistically, that's a much better option than thinking that humans will actually make these gigantic journeys. Then I do this calculation from my class. Einstein's special theory of relativity says that you can do it in a short amount of

Starting point is 00:50:24 time in your own frame of reference if you go close to the speed of light. But then you bring in E equals MC squared and you figure out how much energy it takes to get you accelerated to close enough to the speed of light to make the timescale short in your own frame of reference. And the amount of energy is just unfathomable. We can do it at the large Hadron Collider with protons. We can accelerate them to 99.9999% of the speed of light. But that's just a proton. We're gazillions of protons. That doesn't even count the rocket that would carry us, the payload. You would need to either store the fuel in the rocket, which then

Starting point is 00:51:06 requires even more mass for the rocket, or collect fuel along the way, which is difficult. So getting close to the speed of light, I think, is not an option either other than for a little tiny thing like your email and others are thinking about this star shot project where they'll send a little tiny camera to Alpha Centauri 4.2 light years away. They'll zip past it, take a picture of the exoplanets that we know orbit that three or more star system and say hello real quick and then send the images back to us. Okay. So that's a tiny little thing, right? Maybe you can accelerate that to they're hoping 20% of the speed of light

Starting point is 00:51:47 with a whole bunch of high powered lasers aimed at it. It's not clear that other countries will allow us to do that, by the way. But that's a very forward looking thought. I mean, I very much support the idea, but there's a big difference between sending a little tiny camera and sending a payload of people with equipment that could then mine the resources

Starting point is 00:52:09 on the exoplanet that they reach and then go forth and multiply, right? Well, let's talk about the big galactic things and how we might be able to leverage them to travel fast. I know this is a little bit science fiction, but you know ideas of wormholes and the ideas at the edge of black holes that reveal to us that this fabric of space time is could be messed with. Yeah. Perhaps is that at all an interesting thing for you? I mean, in looking out at the universe and studying it as you have,

Starting point is 00:52:50 is that also a possible like a dream for you that we might be able to find clues how we can actually use it to improve our transportation? It's an interesting thought. I'm certainly excited by the potential physics that suggests this kind of faster than light travel effectively or cutting the down that rabbit hole in, you know, a century ago, Lord Kelvin, one of the greatest physicists of all time said that all of fundamental physics is done.

Starting point is 00:53:32 The rest is just engineering. And guess what? Then came special relativity, quantum physics, general relativity, how wrong he was. So let me not be another Lord Kelvin. On other hand, I think we know a lot more now about what we know and what we don't know and what the physical limitations are. And to me, most of these schemes, if not all of them, seem very far fetched, if not impossible. So travel through wormholes, for example, it appears that for a non-rotating black hole, that's just a complete no-go because the singularity is a point like singularity and you have to reach it to

Starting point is 00:54:12 traverse the wormhole and you get squished by the singularity. Okay. Now, for a rotating black hole, it turns out there is a way to pass through the event horizon, the boundary of the black hole, and avoid the singularity and go out the other side, or even traverse the donut hole like singularity. In the case of a rotating black hole, it's a ring singularity. So there's actually two theoretical ways you could get through a rotating black hole or a charged black hole, not that we expect charged black holes to exist in nature, because they would quickly bring in the opposite charge so as to neutralize themselves. But rotating black holes definitely reality. We now have good evidence for them.

Starting point is 00:54:53 Do they have traversable wormholes? Probably not because it's still the case that when you go in, you go in with so much energy that it either squeezes the wormhole shut, or you encounter a whole bunch of incoming and outgoing energy that vaporizes you. It's called the mass inflation instability, and it just sort of vaporizes you. Nevertheless, you could imagine, well, you're in some vapor form, but if you make it through, maybe you could reform or something. So it's still information.

Starting point is 00:55:27 Yeah, it's still information. It's scrambled information, but there's a way maybe of bringing it back, right? But then the thing that really bothers me is that as soon as you have this possibility of traversal of a wormhole, you have to come to grips with a fundamental problem. And that is that you could come back to your universe at a time prior to your leaving. And you could essentially prevent your grandparents from ever meeting. This is called the grandfather paradox, right? And if they never met and if your parents were never born and if you were never born, how would you have made the journey to prevent the history from allowing you to exist?

Starting point is 00:56:12 It's a causality of causality, of cause and effect. Now physicists such as myself take causality violation very, very seriously. We've never seen it. You took a stand. Yeah. I mean, you know, I mean, it's one of these right back to the future type movies, right? And you have to work things out in such a way that you don't mess things up, right? Some people say that, well, you come back to the universe, but you come back in such a way that you cannot affect your journey.

Starting point is 00:56:42 But then, I mean, that that seems kind of contrived to me. Or some say that you end up in a different universe, and this also goes into the many different types of the multiverse hypothesis and the many worlds interpretation and all that. But again, then it's not the universe from which you left, right? And you don't come back to the universe from which you left. And so you're not really going back in time to the same universe. And you're not even going forward in time, necessarily, then, to the same universe, right? You're ending up in some other universe. So,

Starting point is 00:57:18 so you, you, what have you achieved, right? You've traveled, you've traveled. You traveled. You ended up in a different place than you started in more ways than one. Yeah, and then there's this idea, the Alcubi air drive, where you warp space time in front of you so as to greatly reduce the distance and you can expand the space time behind you. So you're sort of riding away through space time. But the problem I see with that beyond the practical difficulties and the energy requirements. And by the way, how do you get out of this bubble through which you're, you know, riding this wave of space time in Miguel Alcubierre acknowledged all these things. He said, this is purely the theoretical fanciful and all that. But a fundamental problem I see is that you'd have

Starting point is 00:58:03 to get to those places in front of you so as to change the shape of space time, so as to make the journey quickly. But to get there, you got there in the normal way at a speed considerably less than that of light. So in a sense, you haven't saved any time, right? You might as well have just taken that journey and gotten to where you were going. Yeah, there's right. What have you done? It's not like you snap your fingers and say, okay, let that space there be compressed and then I'll make it over to Alpha Centauri in the

Starting point is 00:58:36 next month. You can't snap your fingers and do that. Yeah, and we're sort of assuming that we can fix all the biological stuff that requires for humans to persist persist through that whole process because ultimately it might blow down to just extending the life of the Of the human in some form whether it's through the robot or the digital form or through so or actually just Figuring out genetically how to live forever because that's right that you mentioned, the long journey, might be different if somehow our understanding of genetics, of our understanding of our biology, all that kind of stuff would,

Starting point is 00:59:14 that's another trajectory that possibly would be. If you could put us into some sort of suspended animation, you know, hibernation or something, and greatly increase the lifetime. And so these 10,000 generations I talked about, what do they care? It's just one generation and they're asleep, okay? It's their long nap.

Starting point is 00:59:30 So then you can do it. It's still not easy, right? Because you've got some big ol' huge colony and that just through E equals MC squared, right? That's a lot of mass. That's a lot of stuff to accelerate. The Newtonian kinetic energy is gigantic, right? So you're still not home free,

Starting point is 00:59:48 but at least you're not trying to do it in a short amount of clock time, right? Which, if you look at e equals mc squared, requires truly unfathomable amounts of energy because the energy is sort of, it's your rest mass, m not c squared squared divided by the square root of 1 minus V squared over C squared. If your listeners want to just stick into their pocket calculator as V over C approaches 1,

Starting point is 01:00:16 that 1 over the square root of 1 minus V squared over C squared approaches infinity. If you wanted to do it in zero time, you'd need an infinite amount of energy. That's basically why you can't reach, let alone exceed the speed of light for a particle moving through a pre-existing space. It's that it takes an infinite amount of energy to do so. So that's talking about us going somewhere. What about That's talking about us going somewhere. What about one of the things that inspires a lot of folks, including myself, is the possibility that there's other,

Starting point is 01:00:51 that this conversation is happening and another planet in different forms with intelligent life forms. Well, first we could start as a cosmologist, what's your intuition about whether there is or isn't intelligent life out there, outside of our own? Yeah. I would say I'm one of the pessimists in that I don't necessarily think that we're the only ones in the observable universe, which goes out roughly 14 billion years in light, travel time, and more like 46 billion years when you take into account the expansion of space.

Starting point is 01:01:32 So, the diameter of our observable universe is something like 90, 92 billion light years. That encompasses 100 billion to a trillion galaxies with 100 billion stars each. So, now you're talking about something like 10 to the 22nd, 10 to the trillion galaxies with, you know, 100 billion stars each. So now you're talking about something like 10 to the 22nd, 10 to the 23rd power stars and roughly an equal number of earth-like planets and so on. So there there may well be other intelligent life. But your sense is our galaxy is not teaming with life. Yeah, our galaxy, our Milky Way galaxy with several hundred billion stars and potentially habitable planets is not teaming with intelligent life. Intelligent. Yeah, I wouldn't. Well, I'll get to the primitive life, the bacteria in a moment, but um, you know, we we may well be the only ones in our Milky Way galaxy

Starting point is 01:02:22 at most a handful, I'd say, but I'd probably side with the school of thought that suggests we're the only ones in our own galaxy, just because I don't see human intelligence as being a natural evolutionary path for life. I mean, there's a number of arguments. First of all, there's been more than 10 billion species of life on Earth in its history. Nothing has approached our level of intelligence and mechanical ability and curiosity, you know, whales and dolphins appear to be reasonably intelligent. But there's no evidence that they can think abstract thoughts that they're curious about the world. They certainly can't build machines with which to study the world. So that's one argument. Secondly, we came about as early hominids only four or five million years ago and as hope homo sapiens only about a quarter of a

Starting point is 01:03:18 million years ago. So for the vast majority of the history of life on earth, an intelligent alien zipping by earth would have said there's nothing particularly intelligent or mechanically able on earth. Okay. Thirdly, it's not clear that our intelligence is a long-term evolutionary advantage. Now it's clear that in the last 100 years, 200 years, we've improved the lives of millions, hundreds of millions of people. 200 years, 200 years, we've improved the lives of millions, hundreds of millions of people, but at the risk of potentially destroying ourselves either intentionally or unintentionally or through neglect as we discussed before. That's a really interesting point, which is it's possible that there a huge amount of intelligent civilizations have been born even through our galaxy, but they live very briefly and they die. Flash bulbs in the light. That brings me to the fourth issue and that

Starting point is 01:04:13 is the, you know, the Fermi paradox. If they're common, where the hell are they? You know, notwithstanding the various UFO reports in Roswell and all that. They just don't meet the bar. They don't clear the bar of scientific evidence in my opinion, okay? So there's no clear evidence that they've ever visited us on Earth here. And you know, steady has been now the search for extraterrestrial intelligence has been scanning the skies. And true, we've only looked a couple hundred light years out. That's a tiny fraction of the whole galaxy, a tiny fraction of these hundred billion plus

Starting point is 01:04:48 stars. Nevertheless, you know, if the galaxy were teaming with life, especially intelligent life, you'd expect some of it to have been far more advanced than ours. Okay, there's no special, nothing special about when the industrial revolution started on Earth. The chemical evolution of our galaxy was such that billions of years ago, nuclear processing in stars had built up clouds of gas after their explosion that were rich enough in heavy elements to have formed Earth-like planets, even billions of years ago. There could be civilizations that are billions a year ahead of ours. And if you look at the exponential growth of technology among homo sapiens in the last

Starting point is 01:05:31 couple of hundred years, and you just project that forward, I mean, there's no telling what they could have achieved, even in 1,000 or 10,000 years, let alone a million or 10 million or a billion years. And if they reach this capability of interstellar travel and colonization, then you can show that within 10 million years or certainly 100 million years, you can populate the whole galaxy. And they, you know, so then you don't have to try to detect them beyond 100 or a thousand light years. They would already be here. Do you think as a thought experiment,

Starting point is 01:06:06 do you think it's possible that they are ready here, but we humans are so human-centric that we're just not, like, our conception of what intelligent life looks like. Yeah. Is, is, um, we don't want to acknowledge it. Like, what if trees? Right, right, right.

Starting point is 01:06:24 Yeah. Like, okay, I? Right, right, right. Yeah. Okay, I guess in a form of a question, do you think we'll actually detect intelligent life if it came to visit us? Yeah, I mean, it's like, you know, you're an ant crawling around on a sidewalk somewhere and GD noticed the humans wondering around them. Exactly.

Starting point is 01:06:39 And the Empire State Building and, you know, rocket ships flying to the moon and all that kind of stuff. Right, it's conceivable that we haven't detected it and that we're so primitive compared to them that we're just not able to do so. Like if you look at dark energy, maybe we call it as a field. It's just that my own feeling is that in science now, through observations and experiments, we've measured so many things and basically we understand a lot of stuff. Fabric of reality. Yeah, the fabric of reality we understand quite well. There are a few little things like dark matter and dark energy that may be some sign of some super intelligence,

Starting point is 01:07:17 but I doubt it. Okay, you know, why would some super intelligence be holding clusters of galaxies together? Why would they be responsible for accelerating the expansion of the universe? So the point is, is that through science and applied science and engineering, we understand so much now that I'm not saying we know everything, but we know a hell of a lot, okay? And so there's, it's not like there are lots of mysteries

Starting point is 01:07:41 flying around there that are completely outside our level of of exploration or understanding. Yeah, from a I would say from from the mystery perspective it seems like the mystery of our own like cognition and consciousness is much grander than than the degrees of freedom of possible explanations of what the heck is going on is much greater there than in the physics of the observed. How the brain works. How did life arise?

Starting point is 01:08:16 Yeah. That's big, big questions. But they, to me, don't indicate the existence of an alien or something. I mean, unless we are the aliens, you know, we could have been contamination from some rocket ship that hit here a long, long time ago and all evidence of it has been destroyed. But again, that alien would have started out somewhere.

Starting point is 01:08:37 They're not here watching us right now, right? They're not among us. And so though there are potential explanations for the Fermi paradox and one of them that I kind of like is that the truly intelligent creatures are those that decided not to colonize the whole galaxy because they had quickly run out of room there because it's exponential, right? You send a probe to a planet. It makes two copies. They go out. They make two copies each. And it's's exponential, right? You send a probe to a planet, it makes two copies. They go out, they make two copies each,

Starting point is 01:09:07 and it's an exponential, right? They quickly colonize the whole galaxy, but then the distance to the next galaxy, the next big one like Andromeda, that's two and a half million light years. That's a much grander scale now, right? And so it also could be that the reason they survived this long is that they got over this

Starting point is 01:09:27 tendency that may well exist among sufficiently intelligent creatures, this tendency for aggression and self-destruction. If they bypassed that, and that may be one of the great filters, if there are more than one, then they may not be a type of creature that feels the need to go and say, oh, there's a nice-looking planet. And there's a bunch of ants on it. Let's go squish them and colonize it. No, it could even be the kind of Star Trek-like prime directive where you go and explore worlds, but you don't interfere in any way, right? And also we call it exploration as beautiful and everything, but there is underlying this desire to explore,

Starting point is 01:10:13 is a desire to conquer. I mean, if we're just being really honest about it now for us it is. And you're saying it's possible to separate, but I would venture to say that you wouldn't that those are coupled so I Could I could imagine a civilization that lives on for billions of years that just stays on us Like figures out the minimal Effort way of just peacefully existing. It's like a monastery. Yeah limits itself. Yeah limits itself You know, it's it's planted at seeds in a number of places. So it's not vulnerable to a single point failure, right? Supernova going off near one of these stars or something or an asteroid,

Starting point is 01:10:55 sudden, or a comet coming in from the art cloud equivalent of that planetary system and without warning, you know, thrashing them to bits. So they've got their seeds in a bunch of places, but they chose not to colonize the galaxy. And they also choose not to interfere with this incredibly primitive organism, homo sapiens, right? Or they, this is like a, they enjoy, is like a TV show for them. Yeah, TV show, right? So they just tuned in. Right. So those are post-court nations. Yet I think that to me, the most likely explanation for the peri-me paradox is that

Starting point is 01:11:38 they really are very, very rare. And you know, Carl Sagan estimated a hundred thousand of them. If there's that many, some of them would have been way ahead of us And and I think we would have seen them by now if there were a handful Maybe they're there, but at that point you're right on this dividing line between being a pessimist and an optimist Yeah, and what are the odds for that right if you look at all the things that had to go right for us Yeah, and then you know getting back to something you said earlier, let's discuss primitive life,

Starting point is 01:12:09 that could be the thing that's difficult to achieve. Just getting the random molecules together to a point where they start self-replicating and evolving and becoming better and all that. That's an inordinately difficult thing, I think, though I'm not, you know, some molecular or cell biologists, but just it's the usual argument, you know, you're wandering around in the Sahara Desert and you stumble across a watch, is your initial

Starting point is 01:12:36 response, oh, you know, a bunch of sand grains just came together randomly and formed this watch. No, you think that something formed it or it came from some simpler structure that then became more complex, all right? It didn't just form. Well, even the simplest life is a very, very complex structure. Even the simplest pro-cariotic cells, not to mention eukaryotic cells,

Starting point is 01:13:04 although that transition may have been the so-called great filter as well. Maybe the cells without a nucleus are relatively easy to form. And then the big next step is where you have a nucleus, which then provides a lot of energy, which allows the cell to become much, much more complex and so on.

Starting point is 01:13:22 Interestingly, going from eukaryotic cells, single cells, to multicellular organisms does not appear to be at least on Earth, one of these great filters, because there's evidence that it happened dozens of times independently on Earth. So by a really great filter, something that happens very, very rarely, I mean that we have to get through an obstacle that is just incredibly rare to get through. And one of the really exciting scientific things is that that particular point is something that we might be able to discover, even in our lifetimes, that find life elsewhere,

Starting point is 01:14:05 like Europa or be able to discuss. That would be bad news, right? What? Because if we find lots of pretty advanced life, that would suggest, and especially if we found some defunct, you know, fossilized civilization or something somewhere else, that would be... Oh, that's true. You mean, over like defunct civilization of like somewhere else. That would be... Oh, bacteria, you mean, over like... What's that?

Starting point is 01:14:25 Defunct civilization of like pretty primitive life. Oh, no, I'm sorry. I switched gears there. If we found some intelligent or rather, you know, even trilobites, right and stuff, you know, elsewhere, that would be bad news for us because that would mean that the great filter is ahead of us, you know, right? Oh, interesting, yeah. Because it would mean that lots things are gotten roughly to our level. But given the Fermi paradox, if you accept that the Fermi paradox means that there's no one else out there,

Starting point is 01:14:52 you don't necessarily have to accept that, but if you accept that it means that no one else is out there, and yet there are lots of things we found that are at or roughly at our level, that means that the great filter is ahead of us and that bodes poorly for our long-term future. You know, it's funny, you said, you started by saying you're a little bit

Starting point is 01:15:14 on the pessimistic side, but it's funny because we're doing this kind of dance between pessimism and optimism because I'm not sure if us being alone in the observable universe as intelligent beings is pessimistic. Well, it's good news in a sense for us, because it means that we made it through. Oh, right.

Starting point is 01:15:34 See, if we're the only ones, and there are such great filters, maybe more than one, formation of life might be one of them. Formation of eukaryotic that is with the nucleus cells, be another development of human-like intelligence might be another, right? There might be several such filters, and we were the lucky ones. And then people say, well, then that means

Starting point is 01:15:57 you're putting yourself into a special perspective and every time we've done that, we've been wrong. And yeah, yeah, I know all those arguments, but it still could be the case that there's one of us, at least per galaxy, or per 10, or 100, or a thousand galaxies. And we're sitting here having this conversation because we exist. And so there's an observational selection effect there, right?

Starting point is 01:16:21 Just because we're special doesn't mean that we shouldn't have these conversations about whether or not we're special, right? Just because we're special doesn't mean that we shouldn't have these conversations about whether or not we're special, right? Yeah, so that's so exciting. That's optimistic. So that's the that's the optimistic part that if we don't find other intelligent life there, it might mean that we're the ones that made it. And in general, outside the great filter and so on, And in general, outside the great filter and so on, you know, it's not obvious that the Stephen Hawking thing, which is, it's not obvious that life at risk is going to be kind to us. Oh, yeah.

Starting point is 01:16:53 So, you know, I knew Hawking, and I greatly respect his scientific work, and in particular, the early work on the unification of general theory of relativity and quantum physics to two great pillars in modern physics, you know, Hawking radiation and all that. Fantastic work. If you were alive, you should have been a recipient of this year's physics Nobel Prize, which was for the discovery of black holes and also by Roger Penrose for the theoretical work showing that given a star that's massive enough, you basically can't avoid having a black hole.

Starting point is 01:17:29 Anyway, hocking fantastic. I tip my hat to him. May he rest in peace. That would have been a heck of a noble surprise to have black holes. Yeah, yeah, yeah. A heck of a good go. But going back to what he said that we shouldn't be broadcasting our presence to others, there I actually disagree with him respectfully,

Starting point is 01:17:47 because, first of all, we've been unintentionally broadcasting our presence for a hundred years since the development of radio and TV. Secondly, any alien that has the capability of coming here and squashing us, either already knows about us and, you know, doesn't care because we're just like little ants. And when there are ants in your kitchen, you tend to squash them. But if there are ants on the sidewalk

Starting point is 01:18:13 and you're walking by, do you feel some great conviction that you have to squash any of them? No, you generally don't, right? We're irrelevant to them. All they need to do is keep an eye on us to see whether we're approaching the kind of technological capability and know about them and have intentions of attacking them. And then they can squash us, right?

Starting point is 01:18:35 They could have done it long ago. They'll do it if they want to, whether we advertise our presence or not, is it relevant? So I really think that that's not a huge existential threat. So this is a good place to bring up a difficult topic. You mentioned they might, they would be paying attention to us to see if we come up with any crazy technology. There's folks who have reported UFO sightings. There's actually, every recently found out there's a website that track this, the data, the data

Starting point is 01:19:10 of these reporting and there's millions of them in the past several decades, so seven decades and so on, that they've been recorded. And the Eofologist community, as they refer to themselves, you know, one of the ideas that I find compelling from an alien perspective, that they kind of started showing up ever since we figured out how to build nuclear weapons. That we should. In a coincidence. Yeah. So, I mean, you know, if I was an alien, I would just start showing up then as well. Well, why not just observe us from afar? No, I know. Right. Yeah, I would figure out. But that's why I'm always keeping a distance and staying blurry.

Starting point is 01:19:57 Right. But very pixelated. Very pixelated. You know, there is something in the human condition condition that a cognition that wants to see wants to believe beautiful things in summer terrifying summer exciting goats Bigfoot is a big fascination for folks. Yeah, and your full sightings. I think falls into that There's people that look at lights in the night sky. And I mean, it's kind of a downer to think in a skeptical sense to think that's just the light.

Starting point is 01:20:36 Yeah. You want to feel like there's something magical there. Sure. I mean, I felt that first when my dad, my dad as a physicist, when he first told me about ball lightning, when I was like a little kid. Very weird. Very weird physical phenomenon.

Starting point is 01:20:51 And he said, his intuition was, tell me this is a little kid. Like I really like math. His intuition was, whoever figures out ball lightning will get a Nobel Prize. I think there was a side comment he gave me. And I decided there when I was like five years old or whatever, I'm gonna win a Nobel Prize

Starting point is 01:21:11 for figuring out a ball like. That was like one of the first sort of sparks of the scientific mindset. Those mysteries, they capture your imagination. I think when I speak to people that report UFOs, that's that fire, that's what I see, that excitement. And I understand that. But what do we do with that?

Starting point is 01:21:30 Because there's hundreds of thousands of not millions, and then the scientific community, you're like the perfect person. You have an awesome Einstein, sure. I mean, what do we do with those reports? It's most of the scientific community kind of rolls their eyes and dismisses it. Is it possible that a tiny percent of those folks

Starting point is 01:21:55 saw something that's worth deeply investigating? Sure, we should investigate it. It's just one of these things where, you know, they've not brought us a hunk of kryptonite or something like that, right? They haven't brought us actual tangible physical evidence with which experiments can be done in laboratories. Right. It's it's anecdotal evidence. The photographs are in some cases in most cases I would say quite ambiguous. I don't know what to think about. So David Fravers, the first person, he's a Navy pilot commander. And there's a bunch of them, but he's sort of one of the most legit pilots and people

Starting point is 01:22:34 have ever met. The fact that he saw something weird, he doesn't know what the heck it is, he saw something weird. I mean, I don't know what to do with that. And one on the psychological side, so I'm pretty confident he saw what he says he saw, which he's not providing. He's saying, it's something weird. Right. One of the interesting psychological things that worries me is that everybody in the Navy, everybody in the US government, everybody in the scientific community just kind of like pretended that nothing happened.

Starting point is 01:23:13 That kind of instinct, that's what makes me believe if aliens show up, we all like just ignore their presence. That's what bothered me that you don't You don't investigate it more carefully and use this opportunity to inspire the world. Mm-hmm. Like so in terms of kryptonite I think the conspiracy theory folks Say that whenever there is some good hard evidence that scientists will be excited about The you there's this kind of conspiracy that I don't like because it's ultimately negative.

Starting point is 01:23:48 That the US government will somehow hide the good evidence to protect it. Of course, there's some legitimacy to it because you want to protect military secrets, all that kind of stuff. But I don't know what to do with this beautiful mess because I think millions of people are inspired by UFOs. And it feels like an opportunity to inspire people about science.

Starting point is 01:24:15 So I would say, you know, as Carl Sagan used to say, extraordinary claims require extraordinary evidence, right? I've quoted him a number of times. We would welcome such evidence. On the other hand, you know, a lot of the things that are seen or perhaps even hidden from us, you could imagine for military purposes, surveillance purposes, the US government doesn't want us to know,

Starting point is 01:24:44 or maybe some of these pilots Soviet or Israeli or whatever satellites, right? A lot of the or some of the crashes that have occurred were later found to be, you know, whether balloons or whatever, you know, when there are more conventional explanations, science tends to stay away from the sensational wantons, right? And so it may be that someone else is calling in life is to investigate these phenomena. And I welcome that as a scientist. I don't categorically actually deny the possibility that ships of some sort could have visited us, because as I said earlier, at slow speeds, there's no problem in reaching other stars. In fact,

Starting point is 01:25:32 our Voyager and Pioneer spacecraft in a few million years are going to be in the vicinity of different stars. We can even calculate which ones they're going to be in the vicinity of, right? So there's nothing that breaks any laws of physics if you do it slowly. But that's different, you know, just having Voyager or Pioneer fly by some star, that's different from having active aliens altering the trajectory of their vehicle in real time, spying on us, and then either zipping back to their home planet or sending signals that tell them about us because they are likely many years, many light years away. And they're not gonna have broken that barrier as well, okay?

Starting point is 01:26:15 Right? So, I just, you know, go ahead, study them. Great, you know, for some young kid who wants to do it, it might be they're calling, and that's how they might find meaning in their lives is to be the scientist who really explores these things. I chose not to, because at a very young age, I found the evidence to the degree that I investigated it, to be really quite unconvincing, and I had other things that I wanted to do. But I don't categorically deny the possibility, and I think it should be investigated.

Starting point is 01:26:51 Yeah, I mean, this is one of those phenomena that 99.9% of people are almost definitely, there's conventional explanations, and then there's like mysterious things that probably have explanations that are a little bit more complicated. But there's not enough to work with. I tend to believe that if aliens showed up, there will be plenty of evidence for scientists to study. Exactly. As you said, avoid your type of spacecraft. I could see some kind of a dumb thing, almost like a sensor to like probing, like statistics speaking. Flying by. Maybe lands. Maybe there's some kind of robot type of thingies that just like move

Starting point is 01:27:42 around and so on. Like in ways that we don't understand, but I feel like, well, I feel like there would be plenty of hard, hard to dismiss evidence. And I also, especially this year, believe that the US government is not sufficiently competent, given the huge amount of evidence that will be revealed from this kind of thing to conceal all of it.

Starting point is 01:28:09 At least in modern times, you can say maybe decades ago, in modern times. But the people I speak to, and the reason I bring it up is because so many people write to me, they're inspired by it. By the way, I wanted to comment on something you said earlier. Yeah, I had said that I'm sort of an epistemist in that I think there are very few other intelligent mechanically able creatures out there. But then I said, yes, in a sense, I'm an optimist as you pointed out because it means that we made it through the great filter, right? I meant originally that I'm a pessimist in that I'm pessimistic about the possibility

Starting point is 01:28:47 that there are many, many of us out there. Mathematically speaking, in the Drake equation. Exactly, right, right. But it may mean a good thing for our ultimate survival, right, so I'm glad you caught me on that. Yeah, I definitely agree with you. It is ultimate and ultimate. But anyway, I think, you know, UFO research is interesting.

Starting point is 01:29:06 And I guess one of the reasons I've not been terribly convinced is that I think there are some scientists who are investigating this and they've not found any clear evidence. Now, I must admit, I have not looked through the literature to convince myself that there are many scientists doing systematic studies of these various reports. I can't say for sure that there's a critical mass of them.

Starting point is 01:29:29 Well, the world. But it's just that you never get these reports from hardcore scientists. That's other thing, and astronomers, you know, what do we do? We spend our time studying the heavens, and you think we'd be the ones that are most likely aside from pilots, perhaps, at seeing weird things in the sky, and we just never do, of the unexplained UFO-type nature. Yeah, I definitely, I try to keep an open mind, but for people who listen,

Starting point is 01:29:56 it's actually really difficult for scientists. Like, I get probably, like this year, I probably got over, probably maybe over 1, 1000 emails on the topic of AGI. It's very difficult to, you know, people write to me, it's like, how can you ignore this in AGI side, like this model? This is obviously the model that's going to achieve general intelligence. How can you ignore it? I'm giving you the answer.

Starting point is 01:30:23 Here's my document. And there are always just these large write-ups. The problem is it's very difficult to we through a bunch of BS. It's very possible that you had actually saw the UFO, but you have to acknowledge that by UFO, I mean an extraterrestrial life. You have to acknowledge that by you know for me in an extra stress or life, right? You have to acknowledge the hundreds of thousands of people who are A little bit if not a lot full of BS and from a scientist's perspective It's just it's really hard work and it's When there's amazing stuff out there. It's like why invest in bigfoot?

Starting point is 01:31:04 When evolution in all of its richness is beautiful Who cares about a monkey that walks on two feet or eight or whatever like there's a zillion decoys? At observatories. Yeah true fact we get lots and lots of phone calls When Venus the evening star, but just really a bright planet, happens to be close to the crescent moon, because it's such a striking pair. This happens once in a while. So we get these phone calls, oh, there's a UFO next to the moon. And no, it's Venus. And so they're just, and I'm not saying the best UFO reports are of that nature. Now, there's some much more convincing cases, and I've seen some of the footage and blah, blah,

Starting point is 01:31:50 but it's just there's so many decoys, right? So much noise that you have to filter out. Yeah, and there's only so many scientists. So it's hard. There's so much time as well and you have to choose what problems you work on, you know. This might be a fun question to ask to kind of explore the idea of the expanding universe. So the radius of the observable universe is 45.7 billion light years. And the age of the universe is 13.7 billion years. That's less than the radius of the universe. How's that possible? So that's a great question. So I meant to bring a little prop I have with ping pong balls on a rubber hose, a rubber band. I use it in many of the lectures that one can find of me online. But you have in an expanding universe, the space itself between galaxies, or more correctly clusters of galaxies, expanding. So imagine light going from one cluster to another. It traverses some distance. And then while it's traversing the rest, that part that it already traveled through continues to expand. Now, 13.7 billion years might have gone by

Starting point is 01:33:11 since the light that we are seeing from the early stage, the so-called cosmic microwave background radiation, which is the after glow of the big bang, or the echo of the big bang. Yeah, 13.7 billion years have gone by. That's how long it's taken that light to reach us. But while it's been traveling that distance, the parts that it already traveled continue to expand. So it's like you're walking on at an airport, you know, on one of these walkways, and you're walking along because you're trying to get to your terminal, but the walkway is continuing as well. You end up traveling a greater distance or the same distance faster is another way of putting it, right? That's why you get on one of these traveling

Starting point is 01:33:54 walkways. So you get a roughly a factor of pi, you know, but it's more like 3.2 I think, but when you work it all out, you multiply the number of years the universe has been in existence by three and a quarter or so, and that's how you get this 46 billion light year radius. But how is that, let me ask some nice dumb questions, how is that not traveling fast in the speed of light? Yeah, it's not traveling fast in the speed of light? Yeah, it's not traveling faster in the speed of light because locally at any point if you were to measure the light, the photon zipping past,

Starting point is 01:34:33 it would not be exceeding the speed of light. The speed of light is a locally measured quantity. After light has traversed some distance, if the rubber band keeps on stretching, then yes, it looks like the light traveled a greater distance than it would have had the space not been expanding. But locally, it never was exceeding the speed of light. It's just that the distance through which it already traveled then went off and expanded on its own some more.

Starting point is 01:35:03 And if you give the light credit, so to speak, for having traversed that distance, well, then it looks like it's going faster in the speed of light, but that's not how speed works. Right, that's not how speed works. Speed, and in relativity, also, the other thing that is interesting is that, you know, if you take two ping pong balls

Starting point is 01:35:23 that are sufficiently far apart, especially in an accelerating universe, you can easily have them moving apart from one another faster than the speed of light. So, you know, take two ping pong balls that were originally 400,000 kilometers from each other and let every centimeter in your rubber band expand to two in one second. Then suddenly, this 400,000 kilometer distance is 800,000 kilometers. It went out by 400,000 kilometers in one second that exceeds the 300,000 kilometer per second speed of light. But that light limit, that particle limit in special relativity applies to objects moving through a pre-existing space. There's nothing in either special or general relativity that prevents space itself from

Starting point is 01:36:14 expanding faster in the speed of light. That's no problem. Einstein wouldn't have had a problem with a universe as observed now by cosmologists. Yeah, I'm not sure I'm yet ready to deal emotionally with expanding space. That to me is one of the most awe-inspiring things, starting from the Big Bang. It's definitely abstract. It's space itself is expanding.

Starting point is 01:36:41 Right. Could you, can we talk about the Big Bang a little bit? Sure. Yeah, yeah. What, so like the entirety of it, the universe was very small. Right, but it was not a point. It was not a point. Because if we live in what's called a closed universe now, a sphere or the three-dimensional version of that would be a hypersphere. Then regardless of how far back in time you go, it was always that topological shape. You can't turn a point suddenly into a shell. It always had to be a shell.

Starting point is 01:37:21 When people say, well, the universe started out as a point, that's being kind of flippant, kind of glib. It didn't really. It just started out at a very high density. And we don't know actually whether it was finite or infinite, I think personally that it was finite at the time, but it expanded very, very quickly. Indeed, if it expanentiated and continued in some places to expanentiate, then it could in fact be infinite right now.

Starting point is 01:37:46 And most cosmologists think that it is infinite. Yes, I would infinite, which dimension mass a size space, infinite space. And by that, I mean that if you were trying to use light to measure its size, you'd never be able to measure its size because it would always be bigger than

Starting point is 01:38:04 the distance light can travel. That's what you get in a universe that's accelerating in its expansion. Okay, but if a thing was a hypersphere, it's very small, not a point. Yeah. How can that thing be infinite? Well, it expands exponentially. That's what the inflation theory is all about. Indeed, at your home

Starting point is 01:38:25 institution, Alan Gooth is one of the originators of the whole inflationary universe idea, along with André Linde at Stanford University here in the Bay Area, and others, Alexei Starabinsky, and others had similar sorts of ideas. But in an exponentially expanding universe, if you actually try to make this measurement, you send light out to try to see it curve back around and hit you in the back of the head. If it's an exponentially expanding universe, there are a amount of space remaining to be traversed

Starting point is 01:38:57 is always a bigger and bigger quantity. So you'll never get there from here. You'll never reach the back of your head. So observationally or operationally, it can be thought of as being in place That's one of the best definitions of infinity by the way, that's that that's one of them best sort of Physical manifestations of infinity. Yeah, yeah, because you have to ask how would you actually measure it? Yeah, now I sometimes say to my cosmology theoretical friends

Starting point is 01:39:24 Well, if I took if I were God and I were outside this whole thing and I took a God-like slice in time, wouldn't it be finite no matter how big it is? And they object and they say, Alex, you can't be outside and take a God-like slice of time, you know. Because there's nothing outside. Well, I'm not, you know, or also, you know, what slice of time you're taking depends on your emotion. And that's true, even in special relativity, that slices of time get tilted in a sense if you're moving quickly. The axes, X and T actually become tilted, not perpendicular to one another. And you know, you can look at Brian Green's books and lectures and other things where he imagines taking a loaf of bread

Starting point is 01:40:13 and slicing it in units of time as you progress forward. But then if you're zipping a long relative to that loaf of bread, the slices of time actually become tilted. And so it's not even clear what slices of time mean. But I'm an observational astronomer. I know which end of the telescope to look through. And the way I understand the infinity is, as I just told you, that operationally or observationally, there'd be no way of seeing that it's a finite universe, of measuring a finite universe. And so in that sense, it's infinite. Even if it started out as a finite little dot. Well, not a dot, I'm sorry, a finite little hypersphere.

Starting point is 01:40:57 But it didn't really start out there, because what happened before that? Well, we don't know. See, this is where it gets into a lot of speculation and let's go, I mean, let's go there. Okay, sure. So, you know, nobody can prove you wrong. The idea of what happened before T equals zero

Starting point is 01:41:17 and whether there are other universes out there, I like to say that these are sort of on the boundaries of science. They're not just ideas that we wake up at three in the morning to go to the bathroom and say, oh, well, let's think about what happened before the big bang or let there be a multiplicity of universes. In other words, we have real testable physics that we can use to draw certain conclusions that are plausibility arguments based on what we know. Now admittedly, there are not really direct tests

Starting point is 01:41:48 of these hypotheses. That's why I call them hypotheses. They're not really elevated to a theory because a theory in science is really something that has a lot of experimental or observational support behind it. So they're hypotheses, but they're not unreasonable hypotheses based on what you know about general relativity and quantum physics. And they may

Starting point is 01:42:12 have indirect tests in that if you adopt this hypothesis, then there might be a bunch of things you expect of the universe and lo and behold, that's what we measure. But we're not actually measuring anything at T less than zero, or we're not actually measuring the presence of another universe in this multiverse. And yet there are these indirect ideas that stem forth. So it's hard to prove uniqueness, and it's hard to completely convince oneself

Starting point is 01:42:42 that a certain hypothesis must be true. But, you know, the more and more tests you have that it satisfies, let's say there are 50 predictions it makes. And 49 of them are things that you can measure. And then the 50th one is the one where you want to measure the actual existence of that other universe or what happened before t equals zero. And you can't do that. But you've satisfied 49 of the other testable predictions. And so that's science, right? Now, a conventional condensed metaphysicist or someone who deals with real data in the laboratory might say, oh, you cosmologist, you know, that's not really science because it's not directly testable, but I would say it's sort of testable, but it's not completely testable. And so it's at the boundary, but it's not

Starting point is 01:43:33 like we're coming up with these crazy ideas among them quantum fluctuations out of nothing. And then inflating into a universe with, you might say, well, you created a giant amount of energy, but in fact, this quantum fluctuation out of nothing, you know, in a quantum way violates the conservation of energy, but, you know, who cares? That was a classical law anyway. And then an inflating universe maintains whatever energy it had, be it zero or some infinitesitable amount, in a sense, the stuff of the universe has a positive energy, but there's a negative gravitational energy associated with it. It's like I drop an apple.

Starting point is 01:44:11 I got kinetic energy, energy of motion out of that, but I did work on it to bring it to that height. So by going down and gaining energy of motion, positive one, two, three, four, five units of kinetic energy, it's also gaining or losing, depending on how you want to think of it, negative one, two, three, four, five units of potential energy. So the total energy remains the same. And inflating universe can do that. Or other physicists say that energy isn't conserved in general relativity. That's another way out of creating a universe out of nothing.

Starting point is 01:44:45 But the point is that this is all based on reasonably well-tested physics, and although these extrapolations seem kind of outrageous at first, they're not completely outrageous. They're within the realm of what we call science already. And maybe some young whipper snapper will be able to figure out a way to directly test what happened before T equals zero or to test for the presence of these other universes. But right now we don't have a way of doing that. So speaking of young whipper snappers, Roger Penrose. Yeah. So he kind of has a, you know, idea that we, there might be some information that travels from whatever the hype happened before the big bang.

Starting point is 01:45:28 Yeah. Yeah. Is that is that a doubt it? So do you think it's possible to detect something like actually experimentally be able to detect some? I don't know what it is, radiation, some sort of. Yeah. And the cosmic microwave background radiation, there may be ways

Starting point is 01:45:44 of doing that. Right. But is it philosophically or practically possible to detect signs that this was before the Big Bang, or is it what you said, which is like, everything we observe will, as we currently understand, will have to be a creation of this particular observable

Starting point is 01:46:03 universe. Yeah, I mean, you know, if you, it's very difficult to answer right now because we don't have a single verified, fully self-consistent, experimentally tested quantum theory of gravity. Right. And of course, the beginning of the universe

Starting point is 01:46:19 is a large amount of stuff in a very small space. Yeah. So you need both quantum mechanics and general relativity. Same thing if our universe recalapses and then bounces back to another big bang. You know, there's also ideas there that some of the information leaks through or survives. I don't know that we can answer that question right now because we don't have a quantum theory of gravity that most physicists believe in. and belief is perhaps the wrong word, that most physicists trust because the experimental evidence favors it.

Starting point is 01:46:50 Right? Yeah, there are various forms of string theory. There's quantum loop gravity. There are various ideas, but which, if any, will be the one that survives the test of time and, more importantly, within that, the test of time and more importantly, within that the test of experiment and observation. So my own feeling is probably these things don't survive. I don't think we've seen any evidence in the cosmic microwave background radiation

Starting point is 01:47:15 of information leaking through. Similarly, the one way or one of the few ways in which we might test for the presence of other universes is if they were to collide with ours, that would leave a pattern, a temperature, signature in the cosmic microwave background radiation. Some astrophysicists claim to have found it, but in my opinion, it's not statistically significant to the level that would be necessary to have such an amazing claim, right? You know, it's just a 5% chance that the microwave background had that distribution just by chance.

Starting point is 01:47:50 5% isn't very long odds if you're claiming that instead that you're finding evidence from another universe. I mean, it's like if the large Hadron collider people had claimed after gathering enough data to show the Higgs particle, when there was a 5% chance it could be just a statistical fluctuation in their data. No, they required 5 sigma, 5 standard deviations, which is roughly one chance in 2 million that this is a statistical fluctuation of no physical greater significance. Extraordinary claims require extra evidence. There you go. It all boils down to that. And the greater your claim, the greater is the evidence that is needed and the more evidence you need from independent ways of measuring or of coming to that

Starting point is 01:48:47 deduction. A good example was the accelerating universe. You know, when we found it evidence for it in 1998 with supernovae with exploding stars, it was great that there were two teams that lent some credibility to the discovery, but it was not until other astrophysicists used not only that technique, but more importantly, other independent techniques that had their own potential sources of systematic error or whatever, but they all came to the same conclusion, and that started giving a much more complete picture of what was going on in a picture in which most astrophysicists quickly gained confidence.

Starting point is 01:49:26 That's why that idea caught on so quickly is that there were other physicists and astronomers doing observations completely independent of supernovae that seem to indicate the same thing. Yeah. That period of your life that work with an incredible team of people that won the Nobel Prize is just fascinating work. Oh, you know, never in my wildest dreams as a kid, did I think that I would be involved, much less so heavily involved, in a discovery that's so revolutionary? I mean, you know, as a kid as a scientist, if you're realistic, once you learn a little bit more about how science is done and not going to win a Nobel Prize and be the next Newton or Einstein or whatever, you just hope that you'll contribute something to humankind's understanding of how nature

Starting point is 01:50:19 works, and you'll be satisfied with that. But here I was in the right place at the right time, a lot of luck, a lot of hard work. And there it was. We discovered something that was really amazing. And that was the greatest thrill. I couldn't have asked for anything more than being involved in that discovery. So the couple of teams are supernova cosmology projects

Starting point is 01:50:45 and the high Z supernova search team. So what was the Nova prize given for? It was given for the discovery of the accelerating universe. The excelebrating expansion of the universe. So maybe not for the elucidation of what dark energy is or what causes that expansion, that acceleration be it universes on the outside

Starting point is 01:51:02 or whatever. It's only for the observational fact. So first of all, what is the accelerating universe? So the accelerating universe is simply that if we look at the galaxies moving away from us right now, we would expect them to be moving away more slowly than they were billions of years ago. And that's because galaxies have visible matter, which is gravitationally attractive, and dark matter of an unknown sort that holds galaxies together and holds clusters of galaxies together. And of course, they then pull on one another and they would tend to retard the expansion of the universe just as when I toss an apple up, you know, even ignoring air resistance,

Starting point is 01:51:43 the mutual gravitational attraction between Earth and the apple slows the apple down. If that attraction is great enough, then the apple will someday stop and even come back. The big crunch you could call it, or the Gnabagib, which is big bang backwards, right? That's what could have happened to the universe. But even if the universe's original expansion energy was so great that it avoids the big crunch, that's like an apple thrown at Earth's escape speed. This is original expansion energy was so great that it avoids the big crunch. That's like an apple thrown at Earth's escape speed.

Starting point is 01:52:07 It's like the rockets that go to Mars someday, right? With people. Even then, you'd expect the universe to be slowing down with time. But we looked back through the history of the universe by looking at progressively more distant galaxies and by seeing the evolution of this expansion rate is that in the first nine billion years, yeah, it was slowing down, but in the last five billion years, it's been speeding up. So who asked for that, right? You know, um, I think it's interesting to talk about a little bit of the human story of the Nobel Prize, which is, I mean, it's fascinating. It's a really, first of all, the prize itself. It's kind of fascinating in the psychological level

Starting point is 01:52:58 that, uh, prizes, uh, I know we kind of think that prizes don't matter, but somehow they kind of focus the mind about some of the most special things we've accomplished. They do. The recognition, the funding, you know. But and also in inspiration for, I'm like I said, when I was a little kid, they could call it a Nobel Prize.

Starting point is 01:53:16 Like I didn't, you know, it inspires millions of young scientists. At the same time, there's a sadness to it a little bit that especially in the field, like depending on the field, but experimental fields that involve teams of, I don't know, sometimes hundreds of brilliant people, the NOBA prize is only given to just a handful. That's right. Is it maxed at three? Yeah. Yeah. And it's not even written in Alfred Nobel's will.

Starting point is 01:53:46 It turns out one of our teammates looked into it in a museum in Stockholm when we went there for Nobel a week in 2011. The leaders who got the prize formally knew that without the rest of us working hard in the trenches, the result would not have been discovered. So they invited us to participate in Nobel Week. And so one of the team members looked in the will and it's not there. It's just tradition. That's interesting. But it's archaic. That's the way science used to be done.

Starting point is 01:54:14 Yeah. It's not the way a lot of science is done now. And you look at gravitational wave discovery, which was, you know, recognized with a Nobel Prize in 2017, Ray Weiss set MIT, got it, and Kip Thorn, and Barry Barra, at Caltech. And Ron Dreever, one of the masterminds, had passed away earlier in the year. So again, one of the rules of Nobel is that it's not given posthamously, or at least the one exception might be if they've made their decision and they're busy making their press releases Right before October the first week in October or whatever and then the person passes away

Starting point is 01:54:52 I think they don't change their minds then but yeah, you know it it It doesn't square with today's reality that a lot of science is done by big teams in that case a team of a thousand people in our case It was two teams consisting of about 50 people. And we used techniques that were arguably developed in part by people who astrophysicists who weren't even on those two papers. I mean some of them were, but other papers were written by other people. And so it's like we're standing on the shoulders of giants. And none of those people was officially recognized. And to me, it was okay. You know, again, it was the thrill of doing the work and ultimately the work with the discovery was recognized with

Starting point is 01:55:35 the prize. And, you know, we got to participate in Nobel week. And, you know, it's okay with me. I've known other physicists whose lives were ruined because they did not get the Nobel Prize and they felt strongly that they should have. So it doesn't. Ralph Alfer of the Alfer beta gamma, you know, paper predicting the microwave background radiation. He should have gotten it. His advisor, Gammaf was dead by that point. But, you know, Penzeus and Wilson got it for the discovery and an alpha, apparently from colleagues who knew him while I've talked to them. His life was ruined by this. He just, it just nod at his innards so much.

Starting point is 01:56:18 It's very possible that in the small handful of people, even three, that you would be one of the noble, one of the winners of the Nobel Prize. That doesn't weigh heavy on you. Well, you know, there were the two team leaders, Saul Pearlmutter and Brian Schmitt, and you're just a team leader that are recognized. And then Adam Reese was my postdoc. First author, I guess. Yeah, first author. I was second author of that paper. Yeah. So I was his direct mentor at the time, although he was, you know, one of these people are just, you know, runs with things. He was an MIT undergraduate, by the way, Harvard graduate student and then a postdoc as a so-called

Starting point is 01:56:54 Miller fellow for basic research and science at Berkeley, something that I was back in 84 to 86. But you're, you know, you're largely a free agent, but he worked quite closely with me, and he came to Berkeley to work with me. And on Schmidt's team, he was charged with analyzing the data, and he measured the brightnesses of these distant supernovae, showing that they're fainter and thus more distant and anticipated, and that led to this conclusion that the universe had to have accelerated in order to push them out to such great distances. And I was shocked when he showed me the data, the results of his calculations and measurements. But it's very, you know, so he deserved it. And on Saul's, the girl's son, Gerson Gouldhober deserved it, but he died, I think, a year earlier in 2010.

Starting point is 01:57:41 But that would have been four. And so, and me, well, I was on both teams, but, you know, was I number four, five, six, seven, I don't know. Well, it's also very, so if I were to, it's possible that you're, I mean, I could make a very good case for you in the three. And the, does that cycle, you know, so. But it's that psychologically, I mean, listen, it weighs on me a little bit because I, I don't know what to do with that. Perhaps it should motivate the rethinking, like Time Magazine started doing like,

Starting point is 01:58:19 you know, personal the year. And like they would start doing like concepts and almost like the black hole gets the Nobel Prize or the universe gets the Nobel Prize and here's the list of people. So like, or like the Oscar that you could say because it's a team effort now. It's a team, oh, and it should be redone

Starting point is 01:58:40 and the breakthrough prize in fundamental physics which was started by Yuri Milner and Zuckerberg is involved in others as well. You know, uh, they recognize the larger team. Yeah, they, they recognize teams. And so in fact, both teams in the accelerating universe were recognized with the breakthrough prize in 2015. Nevertheless, the same three people, Reese Pearl, Mutter and Schmidt, us the same three people, Reese Pearl, Mudder and Schmidt got the red carpet rolled out for them and were at the big ceremony and shared half of the prize money and the rest of us roughly 50 shared the other half and didn't get to go to the ceremony.

Starting point is 01:59:16 But I feel for them, I mean, for the gravitational waves, it was a thousand people. What are they going to do and invite everyone? For the Higgs particle, it was six to eight thousand physicists and engineers. In fact, because of the whole issue of who gets it, experimentally, that discovery still has not been recognized. The theoretical work by Peter Higgs and Angler got recognized. But there was a trica of other people who wrote the most complete paper and they were left out. And another guy died. It's all of this heartbreaking.

Starting point is 01:59:52 Some people argue that the Nobel Prize has been diluted to because if you look at Roger Penrose, you can make an argument that he should get the prize by himself. It's just separate those... It could have been should have perhaps he should have perhaps gotten it with Hawking before Hawking's death, right? The problem was Hawking radiation had not been detected, but you could argue that Hawking made enough other fundamental contributions to the theoretical study of black holes. And the observed data were already good enough at the time of before Hawking's death, okay?

Starting point is 02:00:26 I mean, the latest results by Reinhard Gensel's group is that they see the time dilation effect of a star that's passing very close to the black hole in the middle of our galaxy. That's cool, and it adds additional evidence, but hardly anyone doubted the existence of the supermassive black hole. And Andrea Gazz's group, I believe, hadn't yet shown that relativistic effect, and yet she got part of the supermassive black hole and Andrea Gazz's group, I believe hadn't yet shown

Starting point is 02:00:45 that relativistic effect and yet she got part of the prize as well. So clearly it was given for the original evidence that was really good and that evidence is at least a decade old, you know. So one could make the case for for Hawking. One could make the case that in 2016 when mayor and K. Lowe's won the Nobel Prize for the discovery of the first exoplanet 51b Pegasi. Well, there was a fellow at Penn State Alex Wollshan who in 1992 three years preceding 1995 found a Planet orbiting a pulsar, a very weird kind of star, a neutron star, and that wouldn't have been a normal planet, sure. And so the Nobel committee, you know, they gave it for the discovery of planets around

Starting point is 02:01:33 normal, some like stars, but, but hell, you know, well, Sean found a planet, so they could have given it to him as the third person instead of to Jim Peables for the development of what's called physical cosmology. He's at Princeton, he deserved it, but they could have given Nobel for the development of physical cosmology to pebbles, and I would claim some other people were pretty important in that development as well. And they could have given it some other year. So there's a lot of controversy. I try not to dwell on it, was I number three, probably not. Adam Reese did the work.

Starting point is 02:02:08 I helped bounce ideas off of him, but we wouldn't have had the result without him. I was on both teams for reasons. I mean, the style of the first team, the Supernova Cosmology Project, didn't match mine. They came largely from experimental high-energy energy particle physics where there's these hierarchical teams and stuff, and it's hard for the little guy to have a say, at least that's what I kind of thought. Whereas the team of astronomers, led by Brian Schmidt, was, first of all, a bunch of my friends, and they grew up as astronomers making contributions on little teams and we decided to band together, but all of us had our voices heard. So it was sort of a culture, a style that I preferred, really.

Starting point is 02:02:52 But let me tell you a story at the Nobel banquet, okay? I'm sitting there between two physicists who are members of the committee of the Swedish National Academy of Sciences. You know, and I strategically kept, you know, offering them wine and stuff during this long drawn out Nobel ceremony, right? And I got them to be pretty talkative. And then in a polite diplomatic way, I started asking them pointed questions. And basically they admitted that if there are four or more

Starting point is 02:03:24 people equally deserving, they wait for one of them to die, or they just don't give the prize at all when it's unclear who the three are, at least unclear to them, but unclear to them, it's, they're not even right. Part of the time. I mean, Jocelyn Bell discovered pulsars with a radio antennas, a set of radio antennas that her advisor, Anthony Hewish, conceived and built. So he deserves some credit.

Starting point is 02:03:55 But he didn't discover the pulsar. She did. And his initial reaction to the data that she showed him was a condescending rubbish my dear. Yeah, I'm not kidding. I know, I know, Joseph and Bell, and she did not let this destroy her life. She won every other prize under the sun, okay? Vera Rubin, arguably one of the discoverers of dark matter, although there, if you look at the history, there were a number of people. That was the issue.

Starting point is 02:04:28 I think there were a number of people, four or more, who had similar data and similar ideas at about the same time. Ruben won every prize under the sun. The new big, large-scale survey telescope being built in Chile is being renamed the Vera Ruben telescope, because she passed away in December of 2015, I think. It'll conduct this survey, large scale survey with the Rubin telescope. So she's been recognized, but never with the Nobel Prize. And I would say that to her credit, she did not let that consume her life either. And perhaps it was a bit easier because there have been no bell given for the discovery of dark matter.

Starting point is 02:05:10 Whereas in the case of pulsars and Jocelyn Bell, there was a prize given for the discovery of the freaking pulsars. And she didn't get it. What a travesty of justice. So I also think as a fan of fiction, as a fan of stories that the the travesty and the tragedy and the unfairness and the tension of it is what makes the prize and some more prizes beautiful. The the decisions of other humans that result in dreams being broken. And, you know, like, that's why we love the Olympics. As so many, you know, people athletes give their whole life for this particular moment. And then, and then there's the referee decisions

Starting point is 02:05:57 and like little slips of here and there, like the little misfortunes that destroy entire dreams. And that's, it's weird to say, but it feels like that makes the entirety of it even more special. Yeah. If it was perfect, it wouldn't be interesting. Well, humans like competition and they like heroes. And unfortunately, it gives the impression to youngsters today that science is still done by white men with gray beards wearing white lab coats. And I'm very pleased to see that this year, you know, Andrea Gez, the fourth woman in the history of the physics prize, to have received it.

Starting point is 02:06:35 And then two women, one at Berkeley, one elsewhere, one the Nobel Prize in chemistry, without any male co-recipient. And so that's sending a message, I think, to girls that they can do science and they have role models. I think the breakthrough prize and other such prizes show that teams get recognized as well. And if you pay attention to the newspapers, most of the good authors like Dennis over by of the New

Starting point is 02:07:06 York Times and others said that these were teams of people and they emphasized that. They all played a role. Maybe if some grad student hadn't soldered some circuit, maybe the whole thing wouldn't have worked. But still, Ray Wise, Gip Thorne was the theoretical impetus for the whole search for gravitational waves. Barry Barish brought the MIT and Caltech teams together to get them to cooperate at a time when the project was nearly dead from what I understand and contributed greatly to the experimental setup as well. He's a great experimental physicist, but he was really good

Starting point is 02:07:46 at bringing these two teams together. Instead of having them duke it out and blows and leaving both of them bleeding and dying, the National Science Foundation was gonna cut the funding from what I understand. So there's human drama involved in this whole thing. In the Olympics, yeah, a runner, a swimmer, a runner, you know, they, they slip just at the moment they were taking off from the first thing. And that costs them some fraction of a second. And that's it. They didn't win,

Starting point is 02:08:15 you know. And in that case, I mean, the coaches, the families, which I've met a lot of Olympic athletes and the coaches and the families of the athletes are really the winners of the medals. I mean, but they don't get the medal. And it's, you know, credit assignment is a fascinating thing. I mean, that's the full human story we have. Oh, yeah. And outside of prizes, it's fascinating.

Starting point is 02:08:41 I mean, just to be in the middle of it for artificial intelligence, there's a field of deep learning that's really exciting and people have been, there's yet another award, the touring award given for deep learning to three folks who are very much responsible for the field, but so are a lot of others. Yeah, that's right. And there's a few, there's a fellow by the name of Schmidt Huber who sort of symbolizes the the forgotten folks in a deep learning community. But you know, that's the unfortunate sad thing. We remember, we remember Isaac Newton, remember these special figures and the ones that flew close to them, we forget. Well, that's right. Often the breakthroughs were made based on the body of knowledge that had been assimilated prior to that. But again, people like the worship heroes, you mentioned the Oscars earlier,

Starting point is 02:09:45 and, you know, you look at the direct, I mean, well, I mean, okay, directors and stuff, sometimes get awards and stuff, but, you know, you look at even something like, I don't know, songwriters, musicians, Elton John or something, right, Bernie Taupin, right, wrote many of the words, or he's not as well known, or the Beatles or something like that. I was hard-broken to learn that Elvis didn't write most of his songs. Yeah, Elvis, that's right. There you go. But he was the king, right? And he had such a personality and it was such a performer, right? But it's the unsung heroes in many cases.

Starting point is 02:10:21 Yeah. So maybe he's taking a step back. We talked about the Nobel Prize with the accelerating universe, but your work and the ideas around supernova were important in detecting this accelerating universe. Can we go to the very basics of what is this beautiful, mysterious object of a supernova? Right. So a supernova is an exploding star. Most stars die relatively quiet death, our own Sunwell, despite the fact that it'll become a red giant and incinerate earth.

Starting point is 02:10:56 It'll do that reasonably slowly. But there's a small minority of stars that end their lives in a Titanic explosion. And that's not only exciting to watch from afar, but it's critical to our existence because it is in these explosions that the heavy elements synthesize through nuclear reactions during the normal course of the stars evolution and during the explosion itself, get ejected into the cosmos, making them available as raw material for new stars, planets, and ultimately life.

Starting point is 02:11:28 And that's just a great story, the best in some ways. So we like to study these things and our origins, but it turns out these are incredibly useful beacons as well. Because if you know how powerful an exploding star really is by measuring the parent brightness at its peak in galaxies whose distance as we already know through having made other measurements, and you can thus calibrate how powerful the thing really is, and then you find ones that are much more distant, then you can use their observed brightness compared with their true intrinsic power or luminosity

Starting point is 02:12:10 to judge their distance and hence the distance of the galaxy in which they're located. So, okay. It's like looking at, if you'll, let me just give this one analogy, you know, you judge the distance of an oncoming car at night by looking at how bright its headlights appear to be

Starting point is 02:12:26 and you've calibrated how bright the headlights are of a car that's two or three meters away of known distance and you go, oh, that's a faint headlight and so that's pretty far away. You also use the parent angular separation between the two headlights as a consistency check in your brain, but that's what your brain is doing. So we can do that for cars, we can do that for stars.

Starting point is 02:12:47 Nice, I like that. But, you know, with cars, the headlights are all... There's some variation, but they're somewhat similar, so you can make those kinds of conclusions. What, how much variation is there between Supernova that you can? Yeah. Can you detect them? Right. So first of all, there are several different ways that stars can explode. And it depends on their mass and whether they're in a binary system and things like that. And the ones that we used for these cosmological purposes, studying the expansion of the history

Starting point is 02:13:20 of the universe, are the so-called type Roman numeral one lowercase a type one a supernovae. They come from a weird type of a star called a white dwarf. Our own son will turn into a white dwarf in about seven billion years. It'll have about half its present mass compressed into a volume just the size of Earth. So that's an inordinate density, okay? It's incredibly dense. And the matter is what's called by quantum physicists degenerate matter, not because it's morally reprehensible or anything like that,

Starting point is 02:13:54 but this is just the name that... No judgments here. Yeah, quantum physicists give to electrons that are squeezed into a very tight space. The electrons take on emotion due to Heisenberg's uncertainty principle, and also due to the power of the exclusion principle that electrons don't like to be in the same place. They like to avoid each other.

Starting point is 02:14:13 So those two things mean that a lot of electrons are moving very rapidly, which gives the star an extra pressure far above the thermal pressure associated with just the random motions of particles inside the star. So it's a weird type of star, but normally it wouldn't explode and our sun won't explode, except that if such a white dwarf is in a pair with another more or less normal star, it can steal material from that normal star until it gets to an unstable limit, roughly one and a half times the mass of our sun, 1.4 or so. This is known as the Chandra Seikhar limit

Starting point is 02:14:53 after Supermanyan Chandra Seikhar, an Indian astrophysicist, who figured this out when he was about 20 years old on a voyage from India to England, where he was to be educated. And then he did this. And then 50 years later, he won the Nobel Prize on a voyage from India to England where he was to be educated. And then he did this, and then 50 years later, he won the Nobel Prize in physics in 1984, largely for this work. Okay, then he did as a youngster who was on his way

Starting point is 02:15:14 to be educated, you know. Oh, and his advisor, the great Arthur Eddington in England, who had done a lot of great things, and was a great astrophysicist. Nevertheless, he too was human and had his faults. He ridiculed Chandra's scientific work at a conference in England. And most of us, if we had been Chandra, would have just given up astrophysics at that time, when the great Arthur Eddington ridicules our work. That's another inspirational story for the youngster. Just keep going. But anyway, you're advisors.

Starting point is 02:15:50 No matter what your advisor says, right? So, or don't always pay attention to your advisor. Don't lose hope if you really think you're onto something. That doesn't mean never listen to your advisor. They may have sage advice as well. But anyway, when a white dwarf grows to a certain mass, it becomes unstable. And one of the ways it can end its life is to go through a thermonuclear runaway. So basically, the carbon nuclei inside the white dwarf start fusing together to form heavier nuclei. And the energy that those fusion reactions emit, emits doesn't go into being dissipated out of the star or whatever or expanding it the way,

Starting point is 02:16:39 if you take a blowtorch to the middle of the sun, you heat up its gases, the gases would expand and cool. But this degenerate star can't expand and cool. And so the energy pumped in through these fusion reactions goes into making the nuclei move faster, and that gets more of them sufficiently close together that they can undergo nuclear fusion, thereby releasing more energy that goes into speeding up more nuclei, and thus you have a runaway, a bomb, an uncontrolled fusion reactor, right, instead of the controlled fusion, which is what our sun does. Our sun is a marvelous controlled fusion reactor.

Starting point is 02:17:19 This is what we need here on Earth, fusion energy to solve our energy crisis, right? But the sun holds the stuff in, you know, through gravity, and you need a big mass to do that. So this uncontrolled fusion reaction blows up a star that's pretty much the same in all cases. And you measure it to be almost the same in all cases, but the devil is in the details, and in fact we observe them to not be all the same. And theoretically, they might not be all the same because the rate of the fusion reactions might depend on the amount of trace heavier elements in the white dwarf, and that could depend on how old it is when it was, you know, whether it was born billions of years ago, when there weren't

Starting point is 02:18:01 many heavier elements, or whether it's a relatively young white dwarf and all kinds of other things. And part of my work was to show that indeed, not all the type 1a's are the same, you have to be careful when you use them, you have to calibrate them. They're not standard candles the way it just, if all headlights are all candles were the same lumens or whatever, you'd say they're standard and it would be a little candle is an awesome term Okay, standard candles is what astronomers like to say the night sky I don't like that term because there aren't any standard candles But there are standardizable candles and by looking at these Calibrating that's a yeah, you calibrateable standardizable calibrate. You look at enough of them in nearby galaxies whose distance is you know independently.

Starting point is 02:18:48 And what you can tell is that, you know, this is something that a colleague of mine, Mark Phillips did, who was on Schmitt's team, and arguably one of the, was one of the people who deserved the Nobel Prize. But he showed that the intrinsically more powerful type 1a's decline in brightness, and it turns out rise in brightness as well, more slowly than the less luminous 1a's. And so if you calibrate this by measuring a whole bunch of nearby ones, and then you look at a distant one, instead of saying, well, it's a 100 watt type 1a supernova, they're much more powerful than that, by the way, plus or minus 50, you can say, well, it's a 100 watt type 1A supernova. They're much more powerful than that, by the way.

Starting point is 02:19:25 Plus or minus 50, you can say, no, it's a 112 plus or minus 15, or it's 84 plus or minus 17. It tells you where it is in the power scale, and it greatly decreases the uncertainties. And that's what makes these things cosmologically useful. I showed that if you spread the light out into a spectrum, you can tell spectroscopically that these things are different as well. And in 1991, I happened to study two of the extreme peculiar ones,

Starting point is 02:20:00 the low luminosity ones and the high luminosity ones, 1991 BG and 1991 T. This showed that not all the one A's were the same, and indeed, at the time of 1991, I was a little bit skeptical that we could use type 1A's because of this diversity that I was observing. But in 1993, Mark Phillips wrote a paper that showed this correlation between the light curve, the brightness versus time and the peak luminosity and once you get to see enough information to calibrate. Yeah, then they become calibrateable and that was a game changer. How many type 1As are out there to use for data? Now there are thousands of them. Thousands. Well, the high Z team had 16 and the supernova cosmology project had 40, but the 16 were better measured than the 40. And so our statistical uncertainties were comparable. If you look

Starting point is 02:20:58 at the two papers that were published, doesn't make you feel that there's these gigantic explosions just sprinkled out there. Well, I certainly don't want one to be very nearby and it would have to be within something like 10 light years to be an existential threat. So they can happen in our galaxy. Oh yeah, yeah, you know, so they would be okay. In most cases, we'd be okay because our galaxy is 100,000 light years across. Okay. And you'd need one of these things to be within about 10 light years to be an existential threat. And it gives birth to a bunch of other stars, I guess. Yeah, it's birth to expanding gases that are chemically enriched and those expanding gases mixed with other chemically enriched expanding gases or primordial clouds of hydrogen and helium.

Starting point is 02:21:46 I mean, this is in a sense the greatest story ever told, right? I try to, I teach this introductory astronomy course at Berkeley and I tell them there's only five or six things that I want them to really understand and remember and I'm going to come to their deathbed and I'm going to ask them about, and if they get it wrong, I will retroactively fail. And their whole career will have been shot. That's the students' worst nightmare. Observe a total solar eclipse, yet they had the opportunity to do so. I will retroactively fail them.

Starting point is 02:22:16 But one of them is, you know, where did we come from? Where did the elements in our DNA come from? The carbon in our cells, the oxygen that we breathe, the calcium in our bones, the iron in our red blood cells. Those elements, the phosphorus in our DNA, they all came from stars, from nuclear reactions in stars, and they were ejected into the cosmos, and in some cases, like iron made during the explosions and those gases drifted out mixed with other clouds

Starting point is 02:22:48 Made a new star or a star cluster Some of whose members then evolved and exploded thus enriching the gases in the galaxy progressively more with time until finally Four and a half billion years ago from one of these chemically enriched clouds. Our solar system formed with a rocky earth-like planet and somewhere somehow these self-replicating evolving molecules, bacteria formed and evolved through paramecia, anamebos, and slugs, and apes, and us. And here we are, sentient beings that can ask these questions about our very origins, and with our intellect, and with the machines we make, come to a reasonable understanding

Starting point is 02:23:40 of our origins. What a beautiful story. I mean, if that does not put you at least in awe, if not in love with science, and it's power of deduction, I don't know what will, right? It's one of the greatest stories, if not the greatest story, obviously, that's, you know, personality, dependent on all that. It's a subjective opinion, but it's perhaps the greatest story, obviously that's personality dependent and all that. It's a subjective opinion, but it's perhaps the greatest story over ever told. I mean, you could link it to the big bang and go even farther, right, to make an even more complete story. But as a subset, that's even in some ways a greater story than even the existence of

Starting point is 02:24:20 the universe in some ways, because you could end up, you could just imagine some really boring universe that never leads to sentient creatures such as ourselves. And is this supernova? usually the the introduction to that story So yeah, are they usually the thing that launches the is there other engines of creation? Well, the supernova is the one. I mean, I touch upon the subject earlier in my course, in fact, right about now in my lectures, because I talk about how our sun right now is fusing hydrogen to form helium

Starting point is 02:24:52 nuclei. And later, it'll form carbon and oxygen nuclei. But that's where the process will stop for our sun. It's not massive enough. Some stars that are more massive can go somewhat beyond that. So that's the beginning of this idea of the birth of the heavy elements, since they couldn't have been born at the time of the Big Bang. Conditions of temperature and pressure weren't sufficient to make any significant quantities

Starting point is 02:25:18 of the heavier elements. So that's the beginning, but then you need some of these stars to explode, right? Because if those heavy elements remained forever trapped in the cores of stars, then they would not be available for the production of new stars, planets, and ultimately life. So indeed, the supernova, my main area of interest, plays a leading role in this whole story. I saw that you got a chance to call Richard Feynman a mentor of yours when you were at Caltech. Do you have any fond memories of Feynman and lessons that stick with you? Oh yeah. He was quite a character and one

Starting point is 02:26:00 of the deepest thinkers of all time probably. And at least in my life, the physicist who had the single most intuitive understanding of how nature works, of anyone I've met. I learned a number of things from him. He was not my thesis advisor. I worked with Wallace Sargent at Galtech on what are called active galaxies,

Starting point is 02:26:24 big black holes in the centers of galaxies that are Accreting or swallowing material a little bit like the stuff of of this year's Nobel Prize in physics 2020 But fine men I had for for two courses one was General Theory of Relativity at the graduate level and one was applications of quantum physics 12 kinds of interesting things. And he, you know, he had this very intuitive way of looking at things that he tried to, that he tried to bring to his students. And he felt that if you can't explain something in a reasonably simple way to a non-scientist, or at least someone who

Starting point is 02:27:08 is versed a little bit with science, but is not a professional scientist, then you probably don't understand it very well yourself very thoroughly. So that in me made a desire to be able to explain science to the general public. And I've often found that in explaining things, yeah, there's a certain part that I didn't really understand myself. That's one reason I like to teach the introductory courses to the lay public, is that I sometimes find that my explanations are lacking in my own mind. So he did that for me.

Starting point is 02:27:42 Is there a, if I could just pause for a second? Yeah. You said he had one of the most intuitive understanding of nature. Yeah. What, if you could break apart what intuitive means, like, is it on a philosophical level? No, sort of physical.

Starting point is 02:27:56 How do you draw a mental picture or a picture on paper of what's going on? And he's perhaps most famous in this regard for his Feynman diagrams, which in what's going on. And he's perhaps most famous in this regard for his Feynman diagrams, which in what's called quantum electrodynamics, a quantum field theory of electricity and magnetism. What you have are actually an exchange of photons between charge particles, and they might even

Starting point is 02:28:17 be virtual photons if the particles are at rest relative to one another. And there are ways of doing calculations that are brute force that take pages on pages and pages of calculations. And Julian Schwinger developed some of the mathematics for that and won the Nobel Prize for it. But Feynman had these diagrams that he made

Starting point is 02:28:38 and he had a set of rules of what to do at the vertex. You know, you'd have two particles coming together and then a particle going out and then two particles coming out again. And he'd have these rules associated when there were vertices and when there were particles splitting off from one another and all that. And it looked a little bit like a bunch of a hodgepodge at first, but to those who learned the rules and understood them, he, you know, they saw that you could do these complex calculations

Starting point is 02:29:03 in a much simpler way. And indeed, in some ways, Freeman Dyson had an even better knack for explaining really what quantum electrodynamics actually was. But I didn't know Freeman Dyson, I knew Feynman. Maybe he did have a more intuitive view of the world than Feynman did. But of the people I knew, Feynman was the most intuitive, most sort of, is there a picture? Is there a simple way you can understand this? And in the path that a particle follows, even, you can figure out the, you can get the classical path, at least, you know, for a baseball or something like that, by using quantum physics, if you want, but, you know, in a sense, the baseball sniffs out all possible

Starting point is 02:29:47 paths. It goes out to the Andromeda galaxy and then goes to the batter. But the probability of doing that is very, very small because tiny little paths next door to any given path cancel out that path. And the ones that all add together, they are the ones that are more likely to be followed. And this actually ties in with Fairmont's principle of least action. And there are ideas and optics that go into this as well. And it just sort of beautifully brings everything together. But the particles sniff out all possible paths. What a crazy idea.

Starting point is 02:30:23 But if you do the mathematics associated with that, it ends up being actually useful, a useful way of looking at the world. So you're also, I mean, you're widely acknowledged as, I mean, outside of your science work is being one of the greatest educators in the world and fine in this famous, yeah, for being that. Is there something about being a teacher that you've? Well you will it's very very rewarding when you have students were really into it and you know going back to find them at caltech i was taking these graduate courses and there were two of us myself and jeff richman who's now a professor of physics at University of California, Santa Barbara, who asked lots of questions. And a lot of the Cal Tech students are nervous about asking questions. They want to save face. They seem to think that if they ask a question, their peers might

Starting point is 02:31:15 think it's a stupid question. Well, I didn't really care what people thought. And Jeff Richmond didn't either. And we ask all these questions. And in fact, in many cases, they were quite good questions. And Feynman said, well, the rest of you should be having questions like this. And I remember one time in particular when he said, you know, he said to the rest of the class, why is it always these two? Aren't you the rest of you curious about what I'm saying? Do you really understand at all that? Well, if so, why aren't you asking the next most logical question? No, you guys are too scared to ask these questions that these two are asking.

Starting point is 02:31:51 So he actually invited us to lunch a couple of times where just the three of us sat and had lunch with one of the greatest thinkers of 20th century physics. And so he rubbed off on me. And you know, see you encourage questions as well. I invert courage questions, you know, and Yeah, definitely, I mean, you know, I Encourage questions. I like it when students ask questions. I tell them that They shouldn't feel shy about asking a question probably half the students in the class would have that same question if they even

Starting point is 02:32:23 Understood the material enough to ask that question. Yeah. Curiosities is the first step of seeing the beauty of something. So yeah, and the question is the ultimate form of curiosity. Yeah. Let me ask, what is the meaning of life? The meaning of life. From a cosmologist perspective or from a human perspective. Or from my personal, you know, life is what you make of it, really, right? It's, um, each of us has to have our own meaning. And it doesn't have to be,

Starting point is 02:32:58 well, I think that in many cases, meaning is, is to some degree associated with goals, you set some goals or expectations for yourself, things you want to accomplish, things you want to do, things you want to experience, and to the degree that you experience those and do those things, it can give you meaning. You don't have to change the world the way Newton or Michelangelo or DaVinci did. I mean, people often say, you change the world the way Newton or Michelangelo or Da Vinci did I mean people often say you changed the world But look come on there's seven and a half close to eight billion of us now Most of us are not gonna change the world and it's that mean that most of us are leading meaningful lives. No It just has to be something that gives you meaning that gives you satisfaction That gives you a good feeling about what you did. And often, based on human nature, which can be very good and also very bad, but often

Starting point is 02:33:52 it's the things that help others that give us meaning and a feeling of satisfaction. You taught someone to read. You cared for someone who was terminally ill. You brought up a nice family. You brought up your kids. You did a good job. You put your heart and soul into it. You read a lot of books if that's what you wanted to do.

Starting point is 02:34:16 Had a lot of perspectives on life. You traveled the world if that's what you wanted to do. But if some of these things are not within reach, you're in a socio-economic position where you can't travel the world or whatever, you find other forms of meaning. It doesn't have to be some profound, I'm going to change the world, I'm going to be the one who everyone remembers. Type thing, right? In the context of the greatest story ever told, like the fact that we came from stars.

Starting point is 02:34:53 And now or two apes asking about the meaning of life, how does that fit together? Well, that make any sense. You know, it does. It does. And this is sort of what I was referring to, that it's a beautiful universe that allows us to come into creation. Right?

Starting point is 02:35:14 It's a way that the universe found of knowing, of understanding itself. Because I don't think that inanimate rocks and stars and black holes and things have any real capability of abstract thoughts and of learning about the rest of the universe or even their origins. I mean, they're just a pile of atoms that has no conscience, has no ability to think, has no ability to explore. And we do.

Starting point is 02:35:48 And, you know, I'm not saying we're the epitome of all life forever, but at least for life on earth so far, the evidence suggests that we are the epitome in terms of the richness of our thoughts, the degree to which we can explore the universe, do experiments, build machines, understand our origins. And I just hope that we use science for good, not evil, and that we don't end up destroying ourselves. I mean, the whales and dolphins are plenty intelligent. They don't ask abstract questions,

Starting point is 02:36:25 they don't read books, but on the other hand, they're not in any danger of destroying themselves and everything else as well. And so maybe that's a better form of intelligence, but at least in terms of our ability to explore and make use of our minds, I mean, to me, it's this, it's this that gives me the potential for meaning, right? The fact that I can understand and explore.

Starting point is 02:36:52 It's kind of fascinating to think that the universe created us and eventually we've built telescopes to look back at its origins and to wonder how the heck the thing works. It's magnificent. Needn't have been that way. Right? And this is one of the, you know, the multiverse sort of things, you know, you can alter the laws of physics or even the constants of nature seemingly inconsequential things like the mass ratio of the proton and the neutron. Wake me up when it's over, right? What could be more boring? But it turns out you play with things a little bit like the ratio of the mass of the neutron

Starting point is 02:37:33 to the proton. And you generally get boring universes, only hydrogen or only helium or only iron. You don't even get the rich periodic table, let alone bacteria, paramecia, slugs, and humans. Okay? I'm not even anthropocentrizing this to the degree that I could. Even a rich periodic table wouldn't be possible if certain constants weren't this way, but they are. And that, to me, leads to the idea of a multiverse that, you know, that the dice were thrown many many times And there's this cosmic archipelago where most of the universes are are boring and some might be more interesting But we are in the rare breed that's really quite darn

Starting point is 02:38:18 Interesting and if there were only one and maybe there is only one Well, then that's that's truly amazing We're lucky. We're lucky. We're lucky, but I actually think there are lots in the loss, just like there are lots of planets. Earth isn't special for any particular reason. There are lots of planets in our solar system, and especially around other stars. And occasionally, there are going to be ones that are conducive to the development of complexity,

Starting point is 02:38:42 culminating in life as we know it. And that's a beautiful story. I don't think there's a better way to end it. Alex is a huge honor. One of my favorite conversations I've had in this podcast. Well, thank you so much for talking. It was fun. For the honor of having been asked to do this. Thanks for listening to this conversation with Alex for the PENCO. And thank you to our sponsors. Nuro, the maker of functional sugar-free gum and mince that I used to give my brain a quick caffeine boost. Better help, online therapy with a licensed professional, masterclass, online courses that I enjoy from some of the most amazing humans in history, and cash app.

Starting point is 02:39:23 They app I used to send money to friends. Please check out these sponsors in the description to get a discount and support this podcast. If you enjoyed this thing, subscribe on YouTube, review it with 5 stars and up a podcast, follow and spotify, support our Patreon, or connect with me on Twitter, at Lex Friedman. And now let me leave you with some words from Carl Sagan, the nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of star stuff. Thank you for listening and hope to see you next time.

Starting point is 02:40:20 you

Lex Fridman Podcast - #137 – Alex Filippenko: Supernovae, Dark Energy, Aliens & the Expanding Universe

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