Transcript
00:00:00 The following is a conversation with Alex Filipenko, an astrophysicist and professor
00:00:04 of astronomy from Berkeley.
00:00:07 He was a member of both the Supernova Cosmology Project and the HiZ Supernova Search Team
00:00:12 which used observations of the extragalactic supernova to discover that the universe is
00:00:18 accelerating and that this implies the existence of dark energy.
00:00:23 This discovery resulted in the 2011 NOVA Prize for Physics.
00:00:28 Outside of his groundbreaking research, he is a great science communicator and is one
00:00:34 of the most widely admired educators in the world.
00:00:37 I really enjoyed this conversation and am sure Alex will be back again in the future.
00:00:43 Quick mention of each sponsor, followed by some thoughts related to the episode.
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00:01:14 As a side note, let me say that as we talk about in this conversation, the objects that
00:01:20 populate the universe are both awe inspiring and terrifying in their capacity to create
00:01:26 and to destroy us.
00:01:28 Solar flares and asteroids lurking in the darkness of space threaten our humble, fragile
00:01:34 existence here on Earth.
00:01:37 In the chaos, tension, conflict, and social division of 2020, it’s easy to forget just
00:01:44 how lucky we humans are to be here, and with a bit of hard work, maybe one day, we’ll
00:01:50 venture out towards the stars.
00:01:53 If you enjoy this thing, subscribe on YouTube, review it with Five Stars on Apple Podcast,
00:01:57 follow on Spotify, support on Patreon, or connect with me on Twitter at Lex Friedman.
00:02:03 And now, here’s my conversation with Alex Filipenko.
00:02:08 Let’s start by talking about the biggest possible thing, the universe.
00:02:12 Will the universe expand forever or collapse on itself?
00:02:16 Well, you know, that’s a great question.
00:02:18 It’s one of the big questions of cosmology, and of course, we have evidence that the matter
00:02:24 density is sufficiently low that the universe will expand forever.
00:02:28 But not only that, there’s this weird repulsive effect, we call it dark energy for want of
00:02:33 a better term, and it appears to be accelerating the expansion of the universe.
00:02:38 So if that continues, the universe will expand forever, but it need not necessarily continue.
00:02:44 It could reverse sign, in which case the universe could, in principle, collapse at some point
00:02:51 in the far, far future.
00:02:53 So in terms of investment advice, if you were to give me and then to bet all my money on
00:02:58 one or the other, where does your intuition currently lie?
00:03:01 Well, right now, I would say that it would expand forever because I think that the dark
00:03:05 energy is likely to be just quantum fluctuations of the vacuum.
00:03:11 The vacuum zero energy state is not a state of zero energy.
00:03:15 That is, the ground state is a state of some elevated energy which has a repulsive effect
00:03:21 to it.
00:03:22 And that will never go away because it’s not something that changes with time.
00:03:27 So if the universe is accelerating now, it will forever continue to do so.
00:03:31 And yet, I mean, you so effortlessly mentioned dark energy.
00:03:36 Do we have any understanding of what the heck that thing is?
00:03:39 Well, not really.
00:03:40 But we’re getting progressively better observational constraints.
00:03:44 So different theories of what it might be predict different sorts of behavior for the
00:03:50 evolution of the universe.
00:03:51 And we’ve been measuring the evolution of the universe now.
00:03:55 And the data appear to agree with the predictions of a constant density vacuum energy, a zero
00:04:02 point energy.
00:04:05 But one can’t prove that that’s what it is because one would have to show that the measured
00:04:12 numbers agree with the predictions to an arbitrary number of decimal places.
00:04:17 And of course, even if you’ve got 8, 9, 10, 12 decimal places, what if in the 13th one,
00:04:23 the measurements significantly differ from the prediction?
00:04:27 Then the dark energy isn’t this vacuum state, ground state energy of the vacuum.
00:04:35 And so then it could be some sort of a field, some sort of a new energy, a little bit like
00:04:40 light, like electromagnetism, but very different from light, that fills space.
00:04:47 And that type of energy could in principle change in the distant future.
00:04:52 It could become gravitationally attractive for all we know.
00:04:56 There is a historical precedent to that, and that is that the inflation with which the
00:05:00 universe began when the universe was just a tiny blink of an eye old, a trillionth of
00:05:07 a trillionth of a trillionth of a second, the universe went whoosh, it exponentially
00:05:11 expanded.
00:05:12 That dark energy like substance, we call it the inflaton, that which inflated the universe,
00:05:19 later decayed into more or less normal gravitationally attractive matter.
00:05:24 So the exponential early expansion of the universe did transition to a deceleration,
00:05:31 which then dominated the universe for about nine billion years.
00:05:35 And now this small amount of dark energy started causing an acceleration about five billion
00:05:42 years ago.
00:05:43 And whether that will continue or not is something that we’d like to answer, but I don’t know
00:05:48 that we will anytime soon.
00:05:50 So there could be this interesting field that we don’t yet understand that’s morphing over
00:05:56 time, that’s changing the way the universe is expanding.
00:05:59 I mean, it’s funny that you were thinking through this rigorously like an experimentalist.
00:06:06 But what about like the fundamental physics of dark energy?
00:06:11 Is there any understanding of what the heck it is, or is this the kind of the god of the
00:06:20 gaps or the field of the gaps?
00:06:22 So like there must be something there because of what we’re observing.
00:06:26 I’m very much a person who believes that there’s always a cause, you know, there are no miracles
00:06:35 of a supernatural nature, okay?
00:06:39 So I mean, there are two broad categories, either it’s the vacuum zero point energy,
00:06:45 or it’s some sort of a new energy field that pervades the universe.
00:06:50 The latter could change with time, the former, the vacuum energy cannot.
00:06:55 So if it turns out that it’s one of these new fields, and there are many, many possibilities,
00:07:00 they go by the name of quintessence and things like that, but there are many categories of
00:07:06 those sorts of fields, we try with data to rule them out by comparing the actual measurements
00:07:14 with the predictions.
00:07:16 And some have been ruled out, but many, many others remain to be tested.
00:07:22 And the data just have to become a lot better before we can rule out most of them and become
00:07:28 reasonably convinced that this is a vacuum energy.
00:07:31 So there is hypotheses for different fields, like with names and stuff like that?
00:07:35 Yeah, you know, generically quintessence, like the Aristotelian fifth essence, but there
00:07:40 are many, many versions of quintessence.
00:07:42 There’s K essence, there’s even ideas that, you know, this isn’t something from within
00:07:48 this dark energy, but rather, there are a bunch of, say, bubble universes surrounding
00:07:54 our universe, and this whole idea of the multiverse is not some crazy madman type idea anymore.
00:08:00 It’s, you know, real card carrying physicists are seriously considering this possibility
00:08:04 of a multiverse.
00:08:06 And some types of multiverses could have, you know, a bunch of bubbles on the outside,
00:08:10 which gravitationally act outward on our bubble because gravity or gravitons, the quantum
00:08:18 particle that is thought to carry gravity, is thought to traverse the bulk, the space
00:08:24 between these different little bubble membranes and stuff.
00:08:27 And so it’s conceivable that these other universes are pulling outward on us.
00:08:31 That’s not a favored explanation right now, but really, nothing has been ruled out.
00:08:38 No class of models has been ruled out completely.
00:08:41 Certain examples within classes of models have been ruled out.
00:08:46 But in general, I think we still have really a lot to learn about what’s causing this
00:08:52 observed acceleration of the expansion of the universe, be it dark energy or some forces
00:08:58 from the outside, or perhaps, you know, I guess it’s conceivable that, and sometimes
00:09:05 I wake up in the middle of the night screaming, that dark energy, that which causes the acceleration,
00:09:12 and dark matter, that which causes galaxies and clusters of galaxies to be bound gravitationally
00:09:18 even though there’s not enough visible matter to do so.
00:09:21 Maybe these are our 20th and 21st century Ptolemaic epicycles.
00:09:28 So Ptolemy had a geocentric and Aristotelian view of the world.
00:09:32 Everything goes around Earth.
00:09:34 But in order to explain the backward motion of planets among the stars that happens every
00:09:40 year or two, or sometimes several times a year for Mercury and Venus, you needed the
00:09:45 planets to go around in little circles called epicycles, which themselves then went around
00:09:51 Earth.
00:09:52 And in this part of the epicycle where the planet is going in the direction opposite
00:09:58 to the direction of the overall epicycle, it can appear in projection to be going backward
00:10:04 among the stars, so called retrograde motion.
00:10:08 And it was a brilliant mathematical scheme.
00:10:10 In fact, he could have added epicycles on top of epicycles and reproduced the observed
00:10:16 positions of planets to arbitrary accuracy.
00:10:19 And this is really the beginning of what we now call Fourier analysis, right?
00:10:24 Any periodic function can be represented by a sum of sines and cosines of different periods,
00:10:31 amplitudes, and phases.
00:10:33 So it could have worked arbitrarily well.
00:10:36 But other data show that, in fact, Earth is going around the sun.
00:10:42 So our dark energy and dark matter, just these band aids that we now have to try to explain
00:10:49 the data, but they’re just completely wrong.
00:10:53 That’s a possibility as well.
00:10:54 And as a scientist, I have to be open to that possibility as an open minded scientist.
00:11:00 How do you put yourself in the mindset of somebody that, or majority of the scientific
00:11:05 community or majority of people believe that the Earth, everything rotates around Earth?
00:11:10 How do you put yourself in that mindset and then take a leap to propose a model that the
00:11:21 sun is, in fact, at the center of the solar system?
00:11:25 Sure.
00:11:26 I mean, so that puts us back in the shoes of Copernicus, right, 500 years ago, where
00:11:32 he had this philosophical preference for the sun being the dominant body in what we now
00:11:39 call the solar system.
00:11:41 The observational evidence in terms of the measured positions of planets was not better
00:11:48 explained by the heliocentric, sun centered system.
00:11:53 It’s just that Copernicus saw that the sun is the source of all our light and heat, and
00:12:01 he knew from other studies that it’s far away.
00:12:03 So the fact that it appears as big as the moon means it’s actually way, way bigger because
00:12:08 even at that time, it was known that the sun is much farther away than the moon.
00:12:12 So he just felt, wow, it’s big, it’s bright.
00:12:16 What if it’s the central thing?
00:12:18 But the observed positions of planets at the time in the early to mid 16th century under
00:12:26 the heliocentric system was not a better match, at least not a significantly better match
00:12:32 than Ptolemy’s system, which was quite accurate and lasted 1500 years.
00:12:36 Yeah.
00:12:37 That’s so fascinating to think that the philosophical predispositions that you bring to the table
00:12:45 are essential.
00:12:46 So like you have to have a young person come along that has a weird infatuation with the
00:12:50 sun.
00:12:51 Yeah.
00:12:52 That like almost philosophically is like however their upbringing is, they’re more ready for
00:12:58 whatever the more the simpler answer is.
00:13:02 Right.
00:13:03 Oh, that’s kind of sad.
00:13:07 It’s a sad from an individual descendant of eight perspective because then that means
00:13:12 like me, you as a scientist, you’re stuck with whatever the heck philosophies you brought
00:13:19 to the table and you might be almost completely unable to think outside this particular box
00:13:25 you’ve built.
00:13:26 Right.
00:13:27 This is why I’m saying that, you know, as an objective scientist, one needs to have
00:13:29 an open mind to crazy sounding new ideas.
00:13:34 And even Copernicus was very much a man of his time and dedicated his work to the Pope.
00:13:40 He still used circular orbits.
00:13:43 The sun was a little bit off center, it turns out, and a slightly off center circle looks
00:13:48 like a slightly eccentric elliptical orbit.
00:13:52 So then when Kepler, in fact, showed that the orbits are actually in general ellipses,
00:13:58 not circles, the reason that he needed Tuco Brahe’s really great data to show that distinction
00:14:07 was that a slightly off center circle is not much different from a slightly eccentric ellipse.
00:14:13 And so there wasn’t much difference between Kepler’s view and Copernicus’s view and Kepler
00:14:20 needed the better data, Tuco Brahe’s data.
00:14:24 And so that’s, again, a great example of science and observations and experiments working together
00:14:33 with hypotheses and they kind of bounce off each other.
00:14:36 They play off of each other and you continually need more observations.
00:14:40 And it wasn’t until Galileo’s work around 1610 that actual evidence for the heliocentric
00:14:49 hypothesis emerged.
00:14:51 It came in the form of Venus, the planet Venus, going through all of the possible phases from
00:14:57 new to crescent to quarter to gibbous to full to waning gibbous, third quarter waning crescent,
00:15:03 and then new again.
00:15:05 It turns out in the Ptolemaic system with Venus between Earth and the sun, but always
00:15:10 roughly in the direction of the sun, you could only get the new and crescent phases of Venus.
00:15:17 But the observations showed a full set of phases.
00:15:21 And moreover, when Venus was gibbous or full, that meant it was on the far side of the sun.
00:15:26 That meant it was farther from Earth than when it’s crescent, so it should appear smaller
00:15:31 and indeed it did.
00:15:33 So that was the nail in the coffin in a sense.
00:15:36 And then Galileo’s other great observation was that Jupiter has moons going around it,
00:15:42 the four Galilean satellites.
00:15:44 And even though Jupiter moves through space, so too do the moons go with it.
00:15:49 So first of all, Earth is not the only thing that has other things going around it.
00:15:53 And secondly, Earth could be moving as Jupiter does and things would move with it.
00:16:01 We wouldn’t fly off the surface and our moon wouldn’t be left behind and all this kind
00:16:04 of stuff.
00:16:05 So that was a big breakthrough as well, but it wasn’t as definitive in my opinion as
00:16:11 the phases of Venus.
00:16:13 Sometimes I’m revealing my ignorance, but I didn’t realize how much data they were working
00:16:17 with.
00:16:20 So it wasn’t Einstein or Freud thinking in theories.
00:16:27 It was a lot of data and you’re playing with it and seeing how to make sense of it.
00:16:31 So it isn’t just coming up with completely abstract thought experiments.
00:16:36 It’s looking at the data.
00:16:37 Sure.
00:16:38 And you look at Newton’s great work, right?
00:16:40 The Principia, it was based in part on Galileo’s observations of balls rolling down inclined
00:16:47 planes, supposedly falling off the Leaning Tower of Pisa, but that’s probably apocryphal.
00:16:53 In any case, the Roman Catholic Church did history a favor, not that I’m condoning them,
00:17:04 but they placed Galileo under house arrest and that gave Galileo time to publish, to
00:17:10 assemble and publish the results of his experiments that he had done decades earlier.
00:17:15 It’s not clear he would have had time to do that, had he not been under house arrest.
00:17:21 And so Newton, of course, very much used Galileo’s observations.
00:17:27 Let me ask the old Russian overly philosophical question about death.
00:17:34 So we’re talking about the expanding universe.
00:17:36 Sure.
00:17:37 How do you think human civilization will come to an end if we avoid the near term issues
00:17:42 we’re having?
00:17:45 Will it be our sun burning out?
00:17:47 Will it be comets?
00:17:48 Oh, okay.
00:17:49 Will it be, what is it?
00:17:52 Do you think we have a shot at reaching the heat death of the universe?
00:17:58 Yeah.
00:17:59 So we’re going to leave out the anthropogenic causes of our potential destruction, which
00:18:07 I actually think are greater than the celestial causes.
00:18:14 So if we get lucky and intelligent, I don’t know.
00:18:18 So no way will we as humans reach the heat death of the universe.
00:18:23 It’s conceivable that machines, which I think will be our evolutionary descendants, might
00:18:30 reach that, although even they will have less and less energy with which to work as time
00:18:35 progresses because eventually even the lowest mass stars burn out, although it takes them
00:18:40 trillions of years to do so.
00:18:44 So the point is that certainly on Earth, there are other celestial threats, existential threats,
00:18:52 comets, exploding stars, the sun burning out.
00:18:57 So we will definitely need to move away from our solar system to other solar systems.
00:19:02 And then the question is, can they keep on propagating to other planetary systems sufficiently
00:19:10 long?
00:19:11 In our own solar system, the sun burning out is not the immediate existential threat.
00:19:20 That’ll happen in about five billion years when it becomes a red giant, although I should
00:19:25 hasten to add that within the next one or two billion years, the sun will have brightened
00:19:30 enough that unless there are compensatory atmospheric changes, the oceans will evaporate
00:19:38 away.
00:19:39 They’re going to need much less carbon dioxide for the temperatures to be maintained roughly
00:19:44 at their present temperature, and plants wouldn’t like that very much.
00:19:47 So you can’t lower the carbon dioxide content too much.
00:19:51 So within one or two billion years, probably the oceans will evaporate away.
00:19:56 But on a sooner time scale than that, I would say an asteroid collision leading to a potential
00:20:02 mass extinction, or at least an extinction of complex beings such as ourselves that require
00:20:08 quite special conditions unlike cockroaches and amoebas to survive, one of these civilization
00:20:19 changing asteroids is only one kilometer or so in diameter and bigger, and a true mass
00:20:25 extinction event is 10 kilometers or larger.
00:20:28 Now it’s true that we can find and track the orbits of asteroids that might be headed toward
00:20:34 Earth, and if we find them 50 or 100 years before they impact us, then clever applied
00:20:39 physicists and engineers can figure out ways to deflect them.
00:20:43 But at some point, some comet will come in from the deep freeze of the solar system,
00:20:48 and there we have very little warning, months to a year.
00:20:52 What’s the deep freeze, sorry to interrupt.
00:20:54 The deep freeze is sort of out beyond Neptune.
00:20:57 There’s this thing called the Kuiper Belt, and it consists of a bunch of dirty ice balls
00:21:03 or icy dirt balls.
00:21:04 It’s the source of the comets that occasionally come close to the Sun.
00:21:08 And then there’s an even bigger area called the Scattered Disk, which is sort of a big
00:21:13 doughnut surrounding the solar system way out there from which other comets come.
00:21:17 And then there’s the Oort Cloud, W O O R T after Jan Oort, a Dutch astrophysicist, and
00:21:25 it’s the better part of a light year away from the Sun, so a good fraction of the distance
00:21:31 to the nearest star, but that’s like a trillion or 10 trillion comet like objects that occasionally
00:21:37 get disturbed by a passing star or whatever, and most of them go flying out of the solar
00:21:41 system, but some go toward the Sun, and they come in with little warning.
00:21:46 By the time we can see them, they’re only a year or two away from us.
00:21:53 And moreover, not only is it hard to determine their trajectories sufficiently accurately
00:21:59 to know whether they’ll hit a tiny thing like Earth, but outgassing from the comet of gases
00:22:07 when the ices sublimate, that outgassing can change the trajectory just because of conservation
00:22:13 of momentum, right?
00:22:14 It’s the rocket effect.
00:22:15 Gases go out in one direction, the object moves in the other direction.
00:22:19 And so since we can’t predict how much outgassing there will be and in exactly what direction
00:22:25 because these things are tumbling and rotating and stuff, it’s hard to predict the trajectory
00:22:30 with sufficient accuracy to know that it will hit.
00:22:33 And you certainly don’t want to deflect a comet that would have missed but you thought
00:22:38 it was going to hit and end up having it hit.
00:22:41 That would be like the ultimate Charlie Brown goat instead of trying to be the hero, right?
00:22:47 He ended up being the goat.
00:22:50 What would you do if it seemed like in a matter of months that there is some nonzero probability,
00:22:58 maybe a high probability that there will be a collision?
00:23:02 So from a scientific perspective, from an engineering perspective, I imagine you would
00:23:06 actually be in the room of people deciding what to do.
00:23:10 What uh, philosophically too.
00:23:12 It’s a tough one, right?
00:23:13 Because if you only have a few months, that’s not much time in which to deflect it.
00:23:19 Early detection and early action are key because when it’s far away, you only have to deflect
00:23:27 it by a tiny little angle.
00:23:30 And then by the time it reaches us, the perpendicular motion is big enough to miss Earth.
00:23:37 All you need is one radius or one diameter of the Earth, right?
00:23:41 That actually means that all you would need to do is slow it down so it arrives four minutes
00:23:47 later or speed it up so it arrives four minutes earlier and Earth will have moved through
00:23:54 one radius in that time.
00:23:56 So it doesn’t take much.
00:23:57 But you can imagine if a thing is about to hit you, you have to deflect it 90 degrees
00:24:02 or more, right?
00:24:03 You know, and you don’t have much time to do so and you have to slow it down or speed
00:24:07 it up a lot if that’s what you’re trying to do to it.
00:24:09 And so decades is sufficient time, but months is not sufficient time.
00:24:14 So at that point, I would think the name of the game would be to try to predict where
00:24:20 it would hit.
00:24:22 And if it’s in a heavily populated region, try to start an orderly evacuation perhaps.
00:24:33 But you know, that might cause just so much panic that I’m, how would you do with New
00:24:37 York City or Los Angeles or something like that, right?
00:24:41 I might have a different opinion a year ago, I’m a bit disheartened by, you know, in the
00:24:48 movies, there’s always extreme competence from the government.
00:24:54 Competence, yeah.
00:24:55 Competence, yeah.
00:24:56 But we expect extreme incompetence, if anything, right?
00:24:59 Yes, no.
00:25:00 So I’m quite disappointed.
00:25:02 But sort of from a medical perspective, I think you’re saying there, and a scientific
00:25:07 one, it’s almost better to get better and better, maybe telescopes and data collection
00:25:13 to be able to predict the movement of these things, or like come up with totally new technologies
00:25:17 that you can imagine actually sending out, like probes out there to be able to sort of
00:25:24 almost have little finger sensors throughout our solar system to be able to detect stuff.
00:25:29 Well, that’s right.
00:25:30 Yeah, monitoring the asteroid belt is very important and 99% of the so called near earth
00:25:35 objects ultimately come from the asteroid belt.
00:25:39 And so there we can track the trajectories and even if there’s a close encounter between
00:25:43 two asteroids which deflects one of them toward earth, it’s unlikely to be on a collision
00:25:48 course with earth in the immediate future, it’s more like tens of years, so that gives
00:25:53 us time.
00:25:54 But we would need to improve our ability to detect the objects that come in from a great
00:26:00 distance.
00:26:01 And those are much rarer, the comets come in, 1% of the collisions perhaps are with
00:26:09 comets that come in without any warning hardly.
00:26:16 So that might be more like a billion or two billion years before one of those hits us.
00:26:23 So maybe we have to worry about the sun getting brighter on that time scale.
00:26:28 I mean, there’s the possibility that a star will explode near us in the next couple of
00:26:34 billion years.
00:26:35 But over the course of the history of life on earth, the estimates are that maybe only
00:26:46 one of the mass extinctions was caused by a star blowing up in particular, a special
00:26:54 kind called a gamma ray burst, and I think it’s the Ordovician–Silurian extinction
00:27:03 420 or so, 440 million years ago that is speculated to have come from one of these particular
00:27:09 types of exploding stars called gamma ray bursts.
00:27:12 But even there, the evidence is circumstantial.
00:27:15 So those kinds of existential threats are reasonably rare.
00:27:20 The greater danger I think is civilization changing events where it’s a much smaller
00:27:28 asteroid, which those are harder to detect, or a giant solar flare that shorts out the
00:27:37 grid in all of North America, let’s say.
00:27:40 Now, astronomers are monitoring the sun 24 seven with various satellites and we can tell
00:27:46 when there’s a flare or a coronal mass ejection and we can tell that in a day or two, a giant
00:27:52 bundle of energetic particles will arrive and twang the magnetic field of earth and
00:27:58 send all kinds of currents through long distance power lines and that’s what shorts out the
00:28:03 transformers and transformers are expensive and hard to replace and hard to transport
00:28:09 and all that kind of stuff.
00:28:10 So if we can warn the power companies and they can shut down the grid before the big
00:28:18 bundle of particle hits, then we will have mitigated much of this.
00:28:21 Now for a big enough bundle of particles, you can get short circuits even over small
00:28:27 distance scales, so not everything will be saved, but at least the whole grid might not
00:28:32 go out.
00:28:33 So again, astronomers, I like to say, support your local astronomer, they may help someday
00:28:40 save humanity by telling the power companies to shut down the grid, finding the asteroid
00:28:46 50 or 100 years before it hits, then having clever physicists and engineers deflect it.
00:28:52 So many of these cosmic threats, cosmic existential threats, we can actually predict and do something
00:29:00 about or observe before they hit and do something about.
00:29:05 So it’s terrifying to think that people would listen to this conversation.
00:29:10 It’s like when you listen to Bill Gates talk about pandemics in his Ted talk a few years
00:29:14 ago and realizing we should have supported our local astronomer more.
00:29:19 Well, I don’t know whether it’s more because as I said, I actually think human induced
00:29:24 threats or things that occur naturally on earth, either a natural pandemic or perhaps
00:29:29 a bioengineering type pandemic or something like a super volcano.
00:29:36 There was one event towed by I think it was 70 plus thousand years ago that caused a gigantic
00:29:44 decrease in temperatures on earth because it sent up so much soot that it blocked the
00:29:50 sun.
00:29:51 It’s the nuclear winter type disaster scenario that some people including Carl Sagan talked
00:29:55 about decades ago.
00:29:57 What we can see in the history of volcanic eruptions even more recently in the 19th century,
00:30:02 Tambora and other ones, you look at the record and you see rather large dips in temperature
00:30:08 associated with massive volcanic eruptions.
00:30:12 Well these super volcanoes, one of which by the way exists under Yellowstone in the central
00:30:18 US, it’s not just one or two states, it’s a gigantic region and there’s controversy
00:30:25 as to whether it’s likely to blow anytime in the next 100,000 years or so.
00:30:30 But that would be perhaps not a mass extinction or perhaps not a complete existential threat
00:30:37 because you have to get rid of the very last humans for that, but at least getting rid
00:30:43 of killing off so many humans, truly billions and billions of humans.
00:30:49 There have been ones tens of thousands of years ago including this one, Toba I think
00:30:55 it’s called, where it’s estimated that the human population was down to 10,000 or 5,000
00:31:02 individuals, something like that.
00:31:05 If you have a 15 degree drop in temperature over quite a short time, it’s not clear that
00:31:11 even with today’s advanced technology, we would be able to adequately respond at least
00:31:15 for the vast majority of people.
00:31:18 Maybe some would be in these underground caves where you’d keep the president and a bunch
00:31:21 of other important people, but the typical person is not going to be protected when all
00:31:28 of agriculture is cut off.
00:31:32 It could be hundreds of millions or billions of people starving to death.
00:31:36 Exactly.
00:31:37 That’s right.
00:31:38 They don’t all die immediately, but they use up their supplies or again, this electrical
00:31:44 grid.
00:31:45 First of toilet paper.
00:31:46 Dash that toilet paper or the electrical grid.
00:31:50 Imagine North America without power for a year.
00:31:55 We’ve become so dependent, we’re no longer the cave people.
00:31:58 They would do just fine.
00:32:00 What do they care about the electrical grid?
00:32:02 What do they care about agriculture, their hunters and gatherers?
00:32:06 But we now have become so used to our way of life that the only real survivors would
00:32:12 be those rugged individualists who live somewhere out in the forest or in a cave somewhere,
00:32:17 completely independent of anyone else.
00:32:20 Yeah.
00:32:21 Recently I recommended, it’s totally new to me, this kind of survivalist folks, but there’s
00:32:26 a few shows.
00:32:27 There’s a lot of shows of those, but I saw one on Netflix and I started watching them
00:32:32 and they make a lot of sense.
00:32:37 They reveal to you how dependent we are on all aspects of this beautiful systems we human
00:32:43 have built and how fragile they are.
00:32:47 Incredibly fragile.
00:32:48 And this whole conversation is making me realize how lucky we are.
00:32:53 Oh, we’re incredibly lucky, but we’ve set ourselves up to be very, very fragile and
00:32:59 we are intrinsically complex biological creatures that except for the fact that we have brains
00:33:05 and minds with which we can try to prevent some of these things or respond to them.
00:33:11 We as a living organism require quite a narrow set of conditions in order to survive.
00:33:18 We’re not cockroaches.
00:33:20 We’re not going to survive a nuclear war.
00:33:23 So we’re kind of this beautiful dance between, we’ve been talking about astronomy, that astronomy,
00:33:31 the stars like inspires everybody and at the same time, there’s this pragmatic aspect that
00:33:37 we’re talking about.
00:33:39 And so I see space exploration as the same kind of way that it’s reaching out to other
00:33:44 planets, reaching out to the stars, this really beautiful idea.
00:33:48 But if you listen to somebody like Elon Musk, he talks about space exploration as very pragmatic.
00:33:56 Like we have to be, he has this ridiculous way of sounding like an engineer about it,
00:34:03 which is like, it’s obvious we need to become a multi planetary species if we were to survive
00:34:09 long term.
00:34:10 So maybe both philosophically in terms of beauty and in terms of practical, what’s your
00:34:18 thoughts on space exploration, on the challenges of it, on how much we should be investing
00:34:24 in it and on a personal level, like how excited you are by the possibility of going to Mars,
00:34:30 colonizing Mars and maybe going outside the solar system.
00:34:34 Yeah.
00:34:35 You know, great question.
00:34:37 There’s a lot to unpack there of course.
00:34:41 Humans are by their very nature explorers, pioneers.
00:34:44 They want to go out, climb the next mountain, see what’s behind it, explore the option depths,
00:34:51 explore space.
00:34:52 This is our destiny to go out there.
00:34:55 And of course, from a pragmatic perspective, yes, we need to plant our seeds elsewhere
00:35:02 really because things could go wrong here on Earth.
00:35:05 Now some people say that’s an excuse to not take care of our planet.
00:35:11 Well, we say we’re elsewhere and so we don’t have to take good care of our planet.
00:35:14 No, we should take the best possible care of our planet.
00:35:18 We should be cognizant of the potential impact of what we’re doing.
00:35:22 Nevertheless, it’s prudent to have us be elsewhere as well.
00:35:26 So in that regard, I actually agree with Elon.
00:35:31 It’d be good to be on Mars.
00:35:32 That would be yet another place for us from which to explore further.
00:35:38 Would that be a good next step?
00:35:39 Well, it’s a good next step.
00:35:42 I happen to disagree with him as to how quickly it will happen.
00:35:46 I think he’s very optimistic.
00:35:48 Now you need visionary people like Elon to get people going and to inspire them.
00:35:52 I mean, look at the success he’s had with multiple companies.
00:35:57 So maybe he gives this very optimistic timeline in order to be inspirational to those who
00:36:03 are going out there.
00:36:04 And certainly his success with the rocket that is reusable because it landed upright
00:36:10 and all that.
00:36:11 I mean, that’s a game changer.
00:36:12 It’s sort of like every time you flew from San Francisco to Los Angeles, you discard
00:36:16 the airplane, right?
00:36:17 I mean, that’s crazy, right?
00:36:20 So that’s a game changer.
00:36:21 But nevertheless, the timescale over which he thinks that there could be a real thriving
00:36:27 colony on Mars, I think is far too optimistic.
00:36:30 What’s the biggest challenges to you?
00:36:33 One is just getting rockets, not rockets, but people out there and two is the colonization.
00:36:40 Do you have thoughts about this, the challenges of this kind of prospect?
00:36:44 Yeah, I haven’t thought about it in great detail other than recognizing that Mars is
00:36:50 a harsh environment.
00:36:51 Yeah.
00:36:52 You don’t have much of an atmosphere there.
00:36:53 You’ve got less than a percent of Earth’s atmosphere.
00:36:57 So you’d need to build some sort of a dome right away, right?
00:37:00 And that would take time.
00:37:02 You need to melt the water that’s in the permafrost or have canals dug from which you transport
00:37:09 it from the polar ice caps.
00:37:11 You know, I was reading recently in terms of like, what’s the most efficient source
00:37:17 of nutrition for humans that were to live on Mars?
00:37:20 And people should look into this, but it turns out to be insects.
00:37:23 Insects.
00:37:24 Yeah.
00:37:25 So you want, you want to build giant colonies of insects and just be eating them.
00:37:29 Yeah, insects have a lot of protein.
00:37:30 Yeah, a lot of protein.
00:37:32 And they’re easy to grow.
00:37:34 Like you can think of them as farming.
00:37:36 Right.
00:37:37 But it’s not going to be as easy as growing a whole plot of potatoes like in the movie
00:37:41 The Martian, you know, or something, right?
00:37:44 It’s not going to be that easy.
00:37:45 But you know, so there’s this thin atmosphere.
00:37:48 It’s got the wrong composition.
00:37:49 It’s mostly carbon dioxide.
00:37:51 There are these violent dust storms.
00:37:54 The temperatures are generally cold.
00:37:57 You know, you’d need to do a lot of things.
00:37:59 You need to terraform it basically in order to make it nicely livable without some dome
00:38:04 surrounding you.
00:38:05 And if you, and if you insist on a dome, well, that’s not going to house that many people,
00:38:10 right?
00:38:11 You know, so let’s look, let’s look briefly then, you know, we’re looking for a new apartment
00:38:17 to move into.
00:38:18 Right.
00:38:19 So let’s look outside the solar system.
00:38:20 Do you think you’ve, you’ve spoken about exoplanets as well?
00:38:25 Do you think there’s possible homes out there for us outside of our solar system?
00:38:31 There are lots and lots of homes.
00:38:33 Possible homes.
00:38:34 There are, there’s a planetary system around nearly every star you see in the sky.
00:38:40 And one in five of those is thought to have a roughly Earth like planet.
00:38:45 And that’s a relatively new discovery.
00:38:46 Yeah.
00:38:47 It’s a new discovery.
00:38:48 I mean, the Kepler satellite, which was flying around above Earth’s atmosphere was able to
00:38:53 monitor the brightness of stars with exquisite detail.
00:38:57 And they could detect planets crossing the line of sight between us and the star, thereby
00:39:03 dimming its light for a short time ever so slightly.
00:39:08 And it’s amazing.
00:39:09 So there are now thousands and thousands of these exoplanet candidates of which something
00:39:14 like 90% are probably genuine exoplanets.
00:39:17 And you have to remember that only about 1% of stars have their planetary system oriented
00:39:25 edge on to your line of sight, which is what you need for this transit method to work,
00:39:30 right?
00:39:31 Your planetary angle won’t work and certainly perpendicular to your line of sight.
00:39:36 That is in the plane of the sky won’t work because the planet is orbiting the star and
00:39:40 never crossing your line of sight.
00:39:43 So the fact that they found planets orbiting about 1% of the stars that they looked at
00:39:51 in this field of 150 plus thousand stars, they found planets around 1%.
00:39:57 You then multiply by the inverse of 1%, which is 1% is about what the fraction of the stars
00:40:06 that have their planetary system oriented the right way.
00:40:10 And that already back of the envelope calculation tells you that of order 50 to 100% of all
00:40:16 stars have planets.
00:40:18 And then they’ve been finding these Earth like planets, et cetera, et cetera.
00:40:21 So there are many potential homes.
00:40:23 The problem is getting there.
00:40:26 So then a typical bright star, Sirius, the brightest star in the sky, maybe not a typical
00:40:32 bright star, but it’s 8.7 light years away.
00:40:37 So that means the light took 8.7 years to reach us.
00:40:43 We’re seeing it as it was about nine years ago.
00:40:47 So then you ask how long would a rocket take to get there at Earth’s escape speed, which
00:40:54 is 11 kilometers per second.
00:40:57 And it turns out it’s about a quarter of a million years.
00:41:01 Now that’s 10,000 generations.
00:41:04 Let’s say a generation of humans is 25 years.
00:41:07 So you’d need this colony of people that is able to sustain itself, all their food, all
00:41:14 their waste disposal, all their water, all the recycling of everything.
00:41:18 For 10,000 generations, they have to commit themselves to living on this vehicle.
00:41:26 I just don’t see it happening.
00:41:28 What I see potentially happening, if we avoid self destruction, intentional or unintentional
00:41:34 here on Earth, is that machines will do it, robots that can essentially hibernate.
00:41:40 They don’t need to do much of anything for a long, long time as they’re traveling.
00:41:44 And moreover, if some energetic charged particle, some cosmic ray, hits the circuitry, it fixes
00:41:50 itself.
00:41:51 Machines can do this.
00:41:55 It’s a form of artificial intelligence.
00:41:57 You just tell the thing, fix yourself basically.
00:42:00 And then when you land on the planet, start producing copies of yourself, initially from
00:42:05 materials that were perhaps sent, or you just have a bunch of copies there.
00:42:10 And then they set up factories with which to do this.
00:42:13 This is very, very futuristic, but it’s much more feasible, I think, than sending flesh
00:42:20 and blood over interstellar distances, a quarter of a million years to even the nearest stars.
00:42:28 You’re subject to all kinds of charged particles and radiation.
00:42:32 You have to shield yourself really well.
00:42:34 That’s by the way, one of the problems of going to Mars is that it’s not a three day
00:42:38 journey like going to the moon.
00:42:40 You’re out there for the better part of a year or two, and you’re exposed to lots of
00:42:45 radiation, which typically doesn’t do well with living tissue, or living tissue doesn’t
00:42:52 do well with the radiation.
00:42:54 And the hope is that the robots, the AI systems might be able to carry the fire of consciousness,
00:43:05 whatever makes us humans, like a little drop of whatever makes us humans so special, not
00:43:11 to be too poetic about it.
00:43:12 No, but I like being poetic about it because it’s an amazing question.
00:43:17 Is there something beyond just the bits, the ones and zeros to us?
00:43:22 It’s an interesting question.
00:43:24 I like to think that there isn’t anything, and that how beautiful it is that our thoughts,
00:43:29 our emotions, our feelings, our compassion all come from these ones and zeros, right?
00:43:35 That to me actually is a beautiful thought.
00:43:38 And the idea that machines, silicon based life effectively, could be our natural evolutionary
00:43:45 descendants, not from a DNA perspective, but they are our creations and they then carry
00:43:51 on.
00:43:52 That to me is a beautiful thought in some ways, but others find it to be a horrific
00:43:55 thought.
00:43:56 So that’s exciting to you.
00:43:58 It is exciting to me as well because to me, from a purely an engineering perspective,
00:44:05 I believe it’s impossible to create, like whatever systems we create that take over
00:44:11 the world, it’s impossible for me to imagine that those systems will not carry some aspect
00:44:17 of what makes humans beautiful.
00:44:19 So like a lot of people have these kind of paperclip ideas that we’ll build machines
00:44:26 that are cold inside or philosophers call them zombies.
00:44:31 That naturally the systems that will out compete us on this earth will be cold and non conscious,
00:44:41 not capable of all the human emotions and empathy and compassion and love and hate,
00:44:48 the beautiful mix of what makes us human.
00:44:53 But to me, intelligence requires all of that.
00:44:56 So in order to out compete humans, you better be good at the full picture.
00:45:01 Right.
00:45:02 So artificial general intelligence, in my view, encompasses a lot of these attributes
00:45:08 that you just talked about, curiosity, inquisitiveness, you know, right?
00:45:13 It might look very different than us humans, but it will have some of the magic.
00:45:17 But it’ll also be much more able to survive the onslaught of existential threats that
00:45:24 either we bring upon ourselves or don’t anticipate here on earth, or that occasionally come from
00:45:30 beyond and there’s nothing much we can do about a supernova explosion that just suddenly
00:45:34 goes off.
00:45:36 And really, if we want to move to other planets outside our solar system, I think realistically
00:45:42 that’s a much better option than thinking that humans will actually make these gigantic
00:45:48 journeys.
00:45:49 And, you know, then I do this calculation for my class, you know, Einstein’s special
00:45:53 theory of relativity says that you can do it in a short amount of time in your own frame
00:45:57 of reference if you go close to the speed of light.
00:46:00 But then you bring in E equals MC squared and you figure out how much energy it takes
00:46:05 to get you accelerated to close enough to the speed of light to make the time scales
00:46:10 short in your own frame of reference.
00:46:13 And the amount of energy is just unfathomable, right?
00:46:17 We can do it at the Large Hadron Collider with protons, you know, we can accelerate
00:46:22 them to 99.9999% of the speed of light, but that’s just a proton.
00:46:27 We’re gazillions of protons, okay?
00:46:29 And that doesn’t even count the rocket that would carry us, the payload.
00:46:34 And you would need to either store the fuel in the rocket, which then requires even more
00:46:39 mass for the rocket or collect fuel along the way, which, you know, is difficult.
00:46:44 And so getting close to the speed of light, I think, is not an option either other than
00:46:49 for a little tiny thing like, you know, Yuri Milner and others are thinking about this,
00:46:54 the Starshot project where they’ll send a little tiny camera to Alpha Centauri 4.2 light
00:47:00 years away.
00:47:01 They’ll zip past it, take a picture of the exoplanets that we know, orbit that three
00:47:06 or more star system and say hello real quick.
00:47:09 Say hello real quickly and then send the images back to us, okay?
00:47:12 So that’s a tiny little thing, right?
00:47:15 Maybe you can accelerate that to, they’re hoping, 20% of the speed of light with a whole
00:47:19 bunch of high powered lasers aimed at it.
00:47:22 It’s not clear that other countries will allow us to do that, by the way, but that’s a very
00:47:26 forward looking thought.
00:47:27 I mean, I very much support the idea, but there’s a big difference between sending a
00:47:31 little tiny camera and sending a payload of people with equipment that could then mine
00:47:38 the resources on the exoplanet that they reach and then go forth and multiply, right?
00:47:46 Well, let’s talk about the big galactic things and how we might be able to leverage them
00:47:51 to travel fast.
00:47:52 I know this is a little bit science fiction, but, you know, ideas of wormholes and ideas
00:48:03 at the edge of black holes that reveal to us that this fabric of space time could be
00:48:10 messed with, perhaps.
00:48:13 Is that at all an interesting thing for you?
00:48:16 I mean, in looking out at the universe and studying it as you have, is that also a possible,
00:48:24 like a dream for you that we might be able to find clues how we can actually use it to
00:48:29 improve our transportation?
00:48:31 It’s an interesting thought.
00:48:32 I’m certainly excited by the potential physics that suggests this kind of faster than light
00:48:40 travel effectively or, you know, cutting the distance to make it very, very short through
00:48:45 a wormhole or something like that.
00:48:47 Possible?
00:48:48 No?
00:48:49 Well, you know, call me not very imaginative, but based on today’s knowledge of physics,
00:48:54 which I realize, you know, people have gone down that rabbit hole and, you know, a century
00:48:58 ago, Lord Kelvin, one of the greatest physicists of all time, said that all of fundamental
00:49:03 physics is done, the rest is just engineering, and guess what?
00:49:07 Then came special relativity, quantum physics, general relativity, how wrong he was.
00:49:12 So let me not be another Lord Kelvin.
00:49:15 On the other hand, I think we know a lot more now about what we know and what we don’t know
00:49:20 and what the physical limitations are.
00:49:23 And to me, most of these schemes, if not all of them, seem very farfetched, if not impossible.
00:49:30 So travel through wormholes, for example, you know, it appears that for a non rotating
00:49:36 black hole, that’s just a complete no go because the singularity is a point like singularity
00:49:42 and you have to reach it to traverse the wormhole and you get squished by the singularity, okay?
00:49:49 Now for a rotating black hole, it turns out there is a way to pass through the event horizon,
00:49:55 the boundary of the black hole, and avoid the singularity and go out the other side
00:49:59 or even traverse the donut hole like singularity.
00:50:04 In the case of a rotating black hole, it’s a ring singularity.
00:50:06 So there’s actually two theoretical ways you could get through a rotating black hole or
00:50:11 a charged black hole, not that we expect charged black holes to exist in nature because they
00:50:16 would quickly bring in the opposite charge so as to neutralize themselves.
00:50:21 But rotating black holes, definitely a reality.
00:50:23 We now have good evidence for them.
00:50:25 Do they have traversable wormholes?
00:50:29 Probably not because it’s still the case that when you go in, you go in with so much energy
00:50:34 that it either squeezes the wormhole shut or you encounter a whole bunch of incoming
00:50:42 and outgoing energy that vaporizes you.
00:50:46 It’s called the mass inflation instability, and it just sort of vaporizes you.
00:50:50 Nevertheless, you could imagine, well, you’re in some vapor form, but if you make it through,
00:50:55 maybe you could reform or something.
00:50:58 So it’s still information.
00:50:59 Yeah, it’s still information.
00:51:00 It’s scrambled information, but there’s a way maybe of bringing it back, right?
00:51:04 But then the thing that really bothers me is that as soon as you have this possibility
00:51:11 of traversal of a wormhole, you have to come to grips with a fundamental problem, and that
00:51:16 is that you could come back to your universe at a time prior to your leaving, and you could
00:51:24 essentially prevent your grandparents from ever meeting.
00:51:27 This is called the grandfather paradox, right?
00:51:29 And if they never met, and if your parents were never born, and if you were never born,
00:51:33 how would you have made the journey to prevent the history from allowing you to exist, right?
00:51:44 It’s a violation of causality, of cause and effect.
00:51:48 Now physicists such as myself take causality violation very, very seriously.
00:51:54 We’ve never seen it.
00:51:55 You took a stand.
00:51:56 Yeah, I mean, it’s one of these back to the future type movies, right?
00:52:01 And you have to work things out in such a way that you don’t mess things up, right?
00:52:06 Some people say that, well, you come back to the universe, but you come back in such
00:52:10 a way that you cannot affect your journey.
00:52:14 But then that seems kind of contrived to me.
00:52:19 Or some say that you end up in a different universe, and this also goes into the many
00:52:24 different types of the multiverse hypothesis and the many worlds interpretation and all
00:52:28 that.
00:52:29 And then it’s not the universe from which you left, right?
00:52:34 And you don’t come back to the universe from which you left.
00:52:37 And so you’re not really going back in time to the same universe, and you’re not even
00:52:42 going forward in time necessarily then to the same universe, right?
00:52:46 You’re ending up in some other universe.
00:52:50 So what have you achieved, right?
00:52:53 You’ve traveled.
00:52:56 You ended up in a different place than you started in more ways than one.
00:53:00 Yeah.
00:53:01 And then there’s this idea, the Alcubierre drive, where you warp space time in front
00:53:07 of you so as to greatly reduce the distance, and you can expand the space time behind you.
00:53:12 So you’re sort of riding a wave through space time.
00:53:16 But the problem I see with that, beyond the practical difficulties and the energy requirements,
00:53:20 and by the way, how do you get out of this bubble through which you’re riding this wave
00:53:25 of space time?
00:53:26 And Miguel Alcubierre acknowledged all these things.
00:53:29 He said this is purely theoretical, fanciful, and all that.
00:53:31 But a fundamental problem I see is that you’d have to get to those places in front of you
00:53:38 so as to change the shape of space time so as to make the journey quickly.
00:53:44 But to get there, you got there in the normal way at a speed considerably less than that
00:53:49 of light.
00:53:50 So in a sense, you haven’t saved any time, right?
00:53:53 You might as well have just taken that journey and gotten to where you were going, right?
00:54:00 What have you done?
00:54:01 It’s not like you snap your fingers and say, okay, let that space there be compressed,
00:54:06 and then I’ll make it over to Alpha Centauri in the next month.
00:54:10 You can’t snap your fingers and do that.
00:54:12 Yeah.
00:54:13 But yeah, we’re sort of assuming that we can fix all the biological stuff that requires
00:54:18 for humans to persist through that whole process, because ultimately, it might go down to just
00:54:24 extending the life of the human in some form, whether it’s through the robot, through the
00:54:29 digital form, or actually just figuring out genetically how to live forever, because that
00:54:35 journey that you mentioned, the long journey, might be different if somehow our understanding
00:54:41 of genetics, of our understanding of our own biology, all that kind of stuff, that’s another
00:54:47 trajectory that possibly…
00:54:48 Well, right.
00:54:49 If you could put us into some sort of suspended animation, hibernation or something, and greatly
00:54:54 increase the lifetime, and so these 10,000 generations I talked about, what do they care?
00:54:58 It’s just one generation, and they’re asleep, okay?
00:55:00 It’s a long nap.
00:55:02 So then you can do it.
00:55:04 It’s still not easy, right?
00:55:05 Because you’ve got some big old huge colony, and that just through E equals MC squared,
00:55:09 right?
00:55:10 That’s a lot of mass.
00:55:11 That’s a lot of stuff to accelerate.
00:55:13 The Newtonian kinetic energy is gigantic, right?
00:55:18 So you’re still not home free, but at least you’re not trying to do it in a short amount
00:55:23 of clock time, right?
00:55:26 Which if you look at E equals MC squared, requires truly unfathomable amounts of energy,
00:55:32 because the energy is your rest mass, M naught C squared, divided by the square root of one
00:55:39 minus V squared over C squared.
00:55:42 And if your listeners want to just sort of stick into their pocket calculator, as V over
00:55:46 C approaches one, that one over the square root of one minus V squared over C squared
00:55:52 approaches infinity.
00:55:54 So if you wanted to do it in zero time, you’d need an infinite amount of energy.
00:55:58 That’s basically why you can’t reach, let alone exceed the speed of light, for a particle
00:56:04 moving through a preexisting space.
00:56:07 It’s that it takes an infinite amount of energy to do so.
00:56:11 So that’s talking about us going somewhere.
00:56:15 What about, one of the things that inspires a lot of folks, including myself, is the possibility
00:56:22 that there’s other, that this conversation is happening on another planet in different
00:56:27 forms with intelligent life forms.
00:56:35 So first we could start, as a cosmologist, what’s your intuition about whether there
00:56:41 is or isn’t intelligent life out there?
00:56:45 Outside of our own?
00:56:46 Yeah, I would say I’m one of the pessimists in that I don’t necessarily think that we’re
00:56:51 the only ones in the observable universe, which goes out, you know, roughly 14 billion
00:56:57 years in light travel time and more like, you know, 46 billion years when you take into
00:57:02 account the expansion of space.
00:57:04 So the diameter of our observable universe is something like, you know, 90, 92 billion
00:57:08 light years.
00:57:09 That encompasses, you know, a hundred billion to a trillion galaxies with, you know, a hundred
00:57:16 billion stars each.
00:57:17 So now you’re talking about something like 10 to the 22nd, 10 to the 23rd power stars
00:57:22 and roughly an equal number of Earth like planets and so on.
00:57:27 So there may well be other intelligent life.
00:57:32 But your sense is our galaxy is not teeming with life.
00:57:35 Yeah, our galaxy, our Milky Way galaxy with several hundred billion stars and potentially
00:57:41 habitable planets is not teeming with intelligent life.
00:57:44 Intelligent.
00:57:45 Yeah, I wouldn’t, well, I’ll get to the primitive life, the bacteria in a moment, but, you know,
00:57:51 we may well be the only ones in our Milky Way galaxy, at most a handful, I’d say, but
00:57:56 I’d probably side with the school of thought that suggests we’re the only ones in our own
00:58:03 galaxy, just because I don’t see human intelligence as being a natural evolutionary path for life.
00:58:13 I mean, there’s a number of arguments.
00:58:16 First of all, there’s been more than 10 billion species of life on Earth in its history.
00:58:22 Everything has approached our level of intelligence and mechanical ability and curiosity.
00:58:27 You know, whales and dolphins appear to be reasonably intelligent, but there’s no evidence
00:58:31 that they can think abstract thoughts that they’re curious about the world.
00:58:35 They certainly can’t build machines with which to study the world.
00:58:39 So that’s one argument.
00:58:41 Secondly, we came about as early hominids only four or five million years ago and as
00:58:47 homo sapiens only about a quarter of a million years ago.
00:58:52 So for the vast majority of the history of life on Earth, an intelligent alien zipping
00:58:56 by Earth would have said there’s nothing particularly intelligent or mechanically able on Earth.
00:59:02 Okay.
00:59:03 Thirdly, it’s not clear that our intelligence is a long term evolutionary advantage.
00:59:10 Now it’s clear that in the last 100 years, 200 years, we’ve improved the lives of hundreds
00:59:15 of millions of people, but at the risk of potentially destroying ourselves either intentionally
00:59:21 or unintentionally or through neglect, as we discussed before.
00:59:26 That’s a really interesting point, which is it’s possible that they’re a huge amount of
00:59:32 intelligent civilizations have been born even through our galaxy, but they live very briefly
00:59:38 and they die.
00:59:39 Flash bulbs in the night.
00:59:42 That brings me to the fourth issue and that is the Fermi paradox.
00:59:47 If they’re common, where the hell are they?
00:59:52 Notwithstanding the various UFO reports in Roswell and all that, they just don’t meet
00:59:56 the bar.
00:59:57 They don’t clear the bar of scientific evidence in my opinion.
01:00:02 So there’s no clear evidence that they’ve ever visited us on Earth here.
01:00:08 And SETI has been now, the search for extraterrestrial intelligence has been scanning the skies and
01:00:13 true, we’ve only looked a couple of hundred light years out and that’s a tiny fraction
01:00:17 of the whole galaxy, a tiny fraction of these hundred billion plus stars.
01:00:22 Nevertheless, if the galaxy were teaming with life, especially intelligent life, you’d expect
01:00:30 some of it to have been far more advanced than ours.
01:00:34 There’s nothing special about when the industrial revolution started on Earth.
01:00:39 The chemical evolution of our galaxy was such that billions of years ago, nuclear processing
01:00:45 and stars had built up clouds of gas after their explosion that were rich enough in heavy
01:00:51 elements to have formed Earth like planets, even billions of years ago.
01:00:54 So there could be civilizations that are billions of years ahead of ours.
01:00:58 And if you look at the exponential growth of technology among Homo sapiens in the last
01:01:03 couple of hundred years and you just project that forward, I mean, there’s no telling what
01:01:07 they could have achieved even in 1000 or 10,000 years, let alone a million or 10 million or
01:01:13 a billion years.
01:01:15 And if they reach this capability of interstellar travel and colonization, then you can show
01:01:21 that within 10 million years or certainly a hundred million years, you can populate
01:01:25 the whole galaxy.
01:01:28 So then you don’t have to have tried to detect them beyond a hundred or a thousand light
01:01:33 years.
01:01:34 They would already be here.
01:01:35 Do you think as a thought experiment, do you think it’s possible that they are already
01:01:41 here, but we humans are so human centric that we’re just not like our conception of what
01:01:47 intelligent life looks like is, we don’t want to acknowledge it.
01:01:53 Like what if trees?
01:01:54 Right.
01:01:55 Right.
01:01:56 Right.
01:01:57 Okay, I guess the, in the form of a question, do you think we’ll actually detect intelligent
01:02:02 life if it came to visit us?
01:02:04 Yeah.
01:02:05 I mean, it’s like, you know, you’re an ant crawling around on a sidewalk somewhere and
01:02:08 do you notice the humans wandering around and the empire state building and you know,
01:02:13 rocket ships flying to the moon and all that kind of stuff, right?
01:02:16 It’s conceivable that we haven’t detected it and that we’re so primitive compared to
01:02:21 them that we’re just not able to do so.
01:02:23 Like if you look at dark energy, maybe we call it as a field.
01:02:27 It’s just that my own feeling is that in science now through observations and experiments,
01:02:33 we’ve measured so many things and basically we understand a lot of stuff.
01:02:40 Okay.
01:02:41 Fabric of reality.
01:02:42 Yeah.
01:02:43 The fabric of reality, we understand quite well.
01:02:44 And there are a few little things like dark matter and dark energy that may be some sign
01:02:47 of some super intelligence, but I doubt it.
01:02:50 Okay.
01:02:51 You know, why would some super intelligence be holding clusters of galaxies together?
01:02:54 Why would they be responsible for accelerating the expansion of the universe?
01:02:58 So the point is, is that through science and applied science and engineering, we understand
01:03:04 so much now that I’m not saying we know everything, but we know a hell of a lot.
01:03:09 Okay.
01:03:10 And so there’s, it’s not like there are lots of mysteries flying around there that are
01:03:14 completely outside our level of exploration or understanding.
01:03:23 Yeah.
01:03:24 From a, I would say from, from a mystery perspective, it seems like the mystery of our own like
01:03:32 cognition and consciousness is much grander than like the degrees of freedom of possible
01:03:38 explanations for what the heck is going on is much greater there than in the, in the
01:03:42 physics of the observed.
01:03:44 How the brain works.
01:03:46 How did life arise?
01:03:47 Yeah.
01:03:48 That’s big, big questions.
01:03:50 But they, to me, don’t indicate the existence of, of, of an alien or something.
01:03:57 I mean, unless we are the aliens, you know, we could have been contamination from some
01:04:00 rocket ship that, that hit here a long, long time ago and all evidence of it has been destroyed.
01:04:06 But again, that alien would have started out somewhere.
01:04:09 They’re not, they’re not here watching us right now, right?
01:04:14 They’re not among us.
01:04:16 And so though there are expert potential explanations for the Fermi paradox, and one of them that
01:04:22 I kind of like is that the truly intelligent creatures are those that decided not to colonize
01:04:29 the whole galaxy because they’d quickly run out of room there because it’s exponential,
01:04:33 right?
01:04:34 You send a probe to a planet, it makes two copies, they go out, they make two copies
01:04:39 each and it’s an exponential, right?
01:04:41 They quickly colonize the whole galaxy.
01:04:43 But then the distance to the next galaxy, the next big one like Andromeda, that’s two
01:04:47 and a half million light years.
01:04:50 That’s a much grander scale now, right?
01:04:52 And so it also could be that the reason they survived this long is that they got over this
01:04:59 tendency that may well exist among sufficiently intelligent creatures, this tendency for aggression
01:05:06 and self destruction, right?
01:05:09 If they bypass that, and that may be one of the great filters if there are more than one,
01:05:14 right?
01:05:15 Then they may not be a type of creature that feels the need to go and say, oh, there’s
01:05:21 a nice looking planet and there’s a bunch of ants on it, let’s go squish them and colonize
01:05:28 it.
01:05:29 No, it could even be the kind of Star Trek like prime directive where you go and explore
01:05:34 worlds, but you don’t interfere in any way, right?
01:05:38 And also we call it exploration is beautiful and everything, but there is underlying this
01:05:44 desire to explore is a desire to conquer.
01:05:47 Yeah.
01:05:48 I mean, if we’re just being really honest right now for us, it is right.
01:05:52 And you’re saying it’s possible to separate, but I would venture to say that you wouldn’t
01:05:58 that those are coupled.
01:06:00 So I could, I could imagine a civilization that lives on for billions of years that just
01:06:06 stays on, it’s like figures out the minimal effort way of just peacefully existing.
01:06:12 It’s like a monastery.
01:06:13 Yeah.
01:06:14 And it limits itself.
01:06:15 Yeah.
01:06:16 It limits itself.
01:06:17 You know, it’s, it’s planted its seeds in a number of places.
01:06:19 So it’s not vulnerable to a single point failure, right?
01:06:24 Supernova going off near one of these stars or something, or an asteroid or a comet coming
01:06:28 in from the Oort cloud equivalent of that planetary system and without warning, you
01:06:33 know, thrashing them to bits.
01:06:35 So they’ve got their seeds in a bunch of places, but they chose not to colonize, colonize the
01:06:40 galaxy.
01:06:41 And they also choose not to interfere with this incredibly prevalent, primitive organism
01:06:47 homo sapiens, right?
01:06:51 Or they, uh, this is like a, they enjoy, this is like a TV show for them.
01:06:57 Yeah.
01:06:58 It could be like a TV show.
01:06:59 Right.
01:07:00 So they just tuned in.
01:07:01 Right.
01:07:02 There are no other possible explanations yet.
01:07:05 I think that to me, the most likely explanation for the peri me paradox is that they really
01:07:10 are very, very rare.
01:07:12 And you know, Carl Sagan estimated a hundred thousand of them.
01:07:16 If there’s that many, some of them would have been way ahead of us and, and I think we would
01:07:20 have seen them by now.
01:07:22 If there are a handful, maybe they’re there.
01:07:24 But at that point, you’re right on this dividing line between being a pessimist and an optimist.
01:07:29 Yeah.
01:07:30 And what are the odds for that?
01:07:31 Right.
01:07:32 What are the things that had to go right for us?
01:07:35 Yeah.
01:07:36 And then, you know, getting back to something you said earlier, let’s discuss, you know,
01:07:39 primitive life.
01:07:40 Yeah.
01:07:41 That could be the thing that’s difficult to achieve.
01:07:44 Just getting the random molecules together to a point where they start self replicating
01:07:50 and evolving and becoming better and all that.
01:07:53 That’s an inordinately difficult thing, I think, though I’m not, you know, some molecular
01:07:58 or cell biologist, but just it’s, it’s, it’s the usual argument.
01:08:01 You know, you’re wandering around in the Sahara desert and you stumble across a watch.
01:08:06 Is your, is your initial response, oh, you know, a bunch of sand grains just came together
01:08:12 randomly and formed this watch.
01:08:14 No, you, you think that something formed it or it came from some simpler structure that
01:08:21 then became, you know, more complex.
01:08:23 All right.
01:08:24 It didn’t just form.
01:08:26 Well, even the simplest life is, is a very, very complex structure.
01:08:32 Even the, even the simplest prokaryotic cells, not to mention eukaryotic cells, although
01:08:36 that transition may have been the so called great filter as well.
01:08:40 Maybe the cells without a nucleus are relatively easy to form.
01:08:45 And then the big next step is where you have a nucleus, which then provides a lot of energy,
01:08:50 which allows the cell to become much, much more complex and so on.
01:08:54 Interestingly, going from eukaryotic cells, single cells to multicellular organisms does
01:09:01 not appear to be, at least on earth, one of these great filters because there’s evidence
01:09:05 that it happened dozens of times independently on earth.
01:09:08 So by, by a really great filter, something that happens very, very rarely, I mean that
01:09:14 we had to get through an obstacle that is just incredibly rare to get through.
01:09:25 And one of the really exciting scientific things is that that particular point is something
01:09:32 that we might be able to discover, even in our lifetimes that find life elsewhere like
01:09:37 Europa or be able to see that would be bad news, right?
01:09:42 Because if we find lots of pretty advanced life, yeah, that would suggest, and especially
01:09:49 if we found some, you know, defunct, you know, fossilized civilization or something somewhere
01:09:53 else that would be bacteria, you mean, defunct civilization of like, oh, I’m sorry, I switched
01:10:00 gears there.
01:10:01 If we, if we found some intelligent or even trilobites right and stuff, you know, elsewhere,
01:10:06 that would be bad news for us because that would mean that the great filter is ahead
01:10:09 of us, you know, right, because it would mean that lots of, lots of things have gotten roughly
01:10:16 to our level.
01:10:17 Yeah.
01:10:18 But, but given the Fermi paradox, if you accept that the Fermi paradox means that there’s
01:10:23 no one else out there, you don’t necessarily have to accept that, but if you accept that
01:10:27 it means that no one else is out there and yet there are lots of things we found that
01:10:31 are at or roughly at our level, that means that the great filter is ahead of us and that
01:10:36 bodes poorly for our longterm future, you know, it’s funny you said, uh, you started by saying
01:10:45 you’re a little bit on the pessimistic side, but it’s funny because we’re doing this kind
01:10:51 of dance between pessimism and optimism because I’m not sure if us being alone in the observable
01:10:56 universe as intelligent beings is pessimistic, well, it’s good news in a sense for us because
01:11:03 it means that we made it through, see, if we’re the only ones and there are such great
01:11:10 filters, maybe more than one formation of life might be one of them formation of eukaryotic
01:11:16 that is with the nucleus cells being another development of human like intelligence might
01:11:22 be another, right?
01:11:23 There might be several such filters and we were the lucky ones.
01:11:27 And you know, then people say, well then that means you’re putting yourself into a special
01:11:31 perspective and every time we’ve done that we’ve been wrong and yeah, yeah, I know all
01:11:35 those arguments, but it still could be the case that there’s one of us at least per galaxy
01:11:41 or pretend or a hundred or a thousand galaxies and we’re sitting here having this conversation
01:11:47 because we exist.
01:11:49 And so there’s a, there’s an observational selection effect there, right?
01:11:53 Just because we’re special doesn’t mean that we shouldn’t have these conversations about
01:11:57 whether or not we’re special, right?
01:11:59 Yeah, so that’s, that’s so exciting.
01:12:02 That’s optimistic.
01:12:03 So that’s the, that’s the optimistic part that if we don’t find other intelligent life
01:12:08 there, it might mean that we’re the ones that made it.
01:12:13 And in general, outside the great filter and so on, you know, it’s not obvious that the
01:12:19 Stephen Hawking thing, which is, it’s not obvious that life out there is going to be kind to
01:12:23 us.
01:12:24 Oh yeah.
01:12:25 So, you know, I knew Hawking and I greatly respect his, his scientific work and in particular
01:12:33 the early work on the unification of general theory of relativity and quantum physics to
01:12:38 two great pillars in modern physics, you know, Hawking radiation and all that fantastic work.
01:12:42 You know, if you were alive, you should have been a recipient of this year’s physics Nobel
01:12:47 prize, which was for the discovery of black holes and also by Roger Penrose for the theoretical
01:12:53 work showing that given a star that’s massive enough, you basically can’t avoid having a
01:13:00 black hole.
01:13:01 Anyway, Hawking, fantastic.
01:13:02 I, I tip my hat to him.
01:13:04 May he rest in peace.
01:13:05 That would have been a heck of a Nobel prize, black holes, heck of a good group.
01:13:10 But, but, but going back to what he said that we shouldn’t be broadcasting our presence
01:13:14 to others there, I actually disagree with him respectfully because first of all, we’ve
01:13:21 been unintentionally broadcasting our presence for a hundred years since the development
01:13:25 of radio and TV.
01:13:27 Okay.
01:13:28 Secondly, any alien that has the capability of coming here and squashing us either already
01:13:35 knows about us and you know, doesn’t care because we’re just like little ants.
01:13:39 And when there are ants in your kitchen, you tend to squash them.
01:13:42 But if there are ants on the sidewalk and you’re walking by, do you feel some great
01:13:47 conviction that you have to squash any of them?
01:13:49 No, you generally don’t, right?
01:13:51 We’re irrelevant to them.
01:13:53 All they need to do is keep an eye on us to see whether we’re approaching the kind of
01:13:57 technological capability and know about them and have intentions of attacking them.
01:14:04 And then they can squash us, right?
01:14:06 Um, you know, they, they could have done it long ago.
01:14:10 Yeah.
01:14:11 They’ll, they’ll do it if they want to, whether we advertise our presence or not is, is irrelevant.
01:14:17 So I really think that that’s not a huge existential threat.
01:14:21 So this is a good place to bring up a difficult topic.
01:14:25 You mentioned, um, they might, they would be paying attention to us to see if we come
01:14:31 up with any crazy technology.
01:14:34 There’s folks who have reported UFO sightings.
01:14:37 There’s actually, I’ve recently found out there’s a websites that track this, the data,
01:14:42 the data of these reportings, and there’s millions of them in the past, uh, several
01:14:48 decades.
01:14:49 So seven decades and so on that they’ve been recorded and the ufologist community, as they
01:14:58 refer to themselves, you know, one of the ideas that I find compelling from an alien
01:15:05 perspective that they kind of started showing up ever since we figured out how to build
01:15:11 nuclear weapons that we should, uh, so I mean, you know, if I was an LA and I would start
01:15:19 showing up then as well, just, well, why not just observe us from afar?
01:15:23 No, I know.
01:15:24 Right.
01:15:25 I would figure out, but that’s why I’m always, uh, keeping a distance and staying blurry,
01:15:30 but very pixelated, very pixelated, you know, that there is a something in the human condition
01:15:37 that a cognition that wants to see, wants to believe beautiful things and, uh, some
01:15:43 are terrifying, some are exciting, uh, goats, Bigfoot is a big fascination for folks.
01:15:51 Yeah.
01:15:52 And, uh, UFO sightings, I think falls into that.
01:15:54 There’s people that look at lights in the night sky and I mean, there’s, it’s kind of
01:16:02 a downer to think in a skeptical sense, to think that that’s just a light.
01:16:07 Yeah.
01:16:08 You want to feel like there’s something magical there.
01:16:11 Sure.
01:16:12 Uh, I mean, I felt that first when my dad, my dad’s a physicist, when he first told me
01:16:16 about ball lightning when I was like a little kid, very weird, very like weird physical
01:16:22 phenomenon.
01:16:23 And he said, his intuition was telling me this as a little kid, uh, like, I really like
01:16:29 math.
01:16:30 His intuition was whoever figures out ball lightning, we’ll get a Nobel prize.
01:16:34 Like he, I think that was a side comment he gave me and I decided there when I was like
01:16:40 five years old or whatever, I’m going to win a Nobel prize for figuring out ball lightning.
01:16:44 That was like one of the first sort of sparks of the scientific mindset.
01:16:49 Those mysteries, they capture your imagination.
01:16:51 I think when I speak to people that report UFOs, that’s that fire.
01:16:56 That’s what I see.
01:16:57 That excitement.
01:16:58 And I understand that.
01:16:59 But what, what do we do with that?
01:17:02 Because there’s hundreds of thousands, if not millions, and then the scientific community,
01:17:08 you’re like the perfect person.
01:17:09 You have an awesome Einstein shirt.
01:17:13 What, what do we do with those reports?
01:17:17 It’s a, most of the scientific community kind of rolls their eyes and dismisses it.
01:17:21 Is it possible that a tiny percent of those folks saw something that’s worth deeply investigating?
01:17:30 Sure.
01:17:31 We should investigate it.
01:17:32 It’s just one of these things where, you know, they’ve not brought us a hunk of kryptonite
01:17:37 or something like that, right?
01:17:38 They haven’t brought us actual tangible physical evidence with which experiments can be done
01:17:44 in laboratories.
01:17:45 Right.
01:17:46 It’s, it’s anecdotal evidence.
01:17:48 The photographs are, in some cases, in most cases, I would say quite ambiguous.
01:17:54 I don’t know what to think about.
01:17:55 So David Faber is the first person.
01:17:58 He’s a Navy pilot, commander, and there’s a bunch of them, but he’s sort of one of the
01:18:02 most legit pilots and people I’ve ever met.
01:18:08 The fact that he saw something weird, he doesn’t know what the heck it is, but he saw something
01:18:14 weird.
01:18:15 I mean, I don’t know what to do with that.
01:18:16 And one on the psychological side, so I’m pretty confident he saw what he says he saw,
01:18:24 which he’s not, he’s saying it’s something weird.
01:18:29 One of the interesting psychological things that worries me is that everybody in the Navy,
01:18:36 everybody in the US government, everybody in the scientific community, just kind of
01:18:40 like pretended that nothing happened.
01:18:45 That kind of instinct.
01:18:47 That’s what makes me believe if aliens show up, we would all like just ignore their presence.
01:18:53 That’s what bothered me that you don’t, you don’t investigate it more carefully and use
01:19:00 this opportunity to inspire the world.
01:19:03 So in terms of kryptonite, I think the conspiracy theory folks say that whenever there is some
01:19:12 good hard evidence that scientists would be excited about, there’s this kind of conspiracy
01:19:17 that I don’t like because it’s ultimately negative that the US government will somehow
01:19:21 hide the good evidence to protect it.
01:19:26 Of course, there’s some legitimacy to it because you want to protect military secrets, all
01:19:32 that kind of stuff.
01:19:33 But I don’t know what to do with this beautiful mess because I think millions of people are
01:19:41 inspired by UFOs and it feels like an opportunity to inspire people about science.
01:19:47 So I would say, as Carl Sagan used to say, extraordinary claims require extraordinary
01:19:53 evidence.
01:19:54 I’ve quoted him a number of times.
01:19:59 We would welcome such evidence.
01:20:03 On the other hand, a lot of the things that are seen or perhaps even hidden from us, you
01:20:08 could imagine for military purposes, surveillance purposes, the US government doesn’t want us
01:20:15 to know.
01:20:16 Or maybe some of these pilots saw Soviet or Israeli or whatever satellites or some of
01:20:24 the crashes that have occurred were later found to be weather balloons or whatever.
01:20:31 When there are more conventional explanations, science tends to stay away from the sensational
01:20:40 ones.
01:20:41 And so it may be that someone else’s calling in life is to investigate these phenomena.
01:20:49 And I welcome that as a scientist.
01:20:51 I don’t categorically actually deny the possibility that ships of some sort could have visited
01:20:58 us because, as I said earlier, at slow speeds, there’s no problem in reaching other stars.
01:21:04 In fact, our Voyager and Pioneer spacecraft in a few million years are going to be in
01:21:08 the vicinity of different stars.
01:21:10 We can even calculate which ones they’re going to be in the vicinity of, right?
01:21:15 So there’s nothing that breaks any laws of physics if you do it slowly.
01:21:19 But that’s different, just having Voyager or Pioneer fly by some star, that’s different
01:21:24 from having active aliens altering the trajectory of their vehicle in real time, spying on us,
01:21:31 and then either zipping back to their home planet or sending signals that tell them about
01:21:38 us because they are likely many light years away, and they’re not going to have broken
01:21:44 that barrier as well, okay?
01:21:48 So I just, you know, go ahead, study them.
01:21:54 For some young kid who wants to do it, it might be their calling, and that’s how they
01:22:00 might find meaning in their lives, is to be the scientist who really explores these things.
01:22:05 I chose not to because at a very young age, I found the evidence, to the degree that I
01:22:11 investigated it, to be really quite unconvincing, and I had other things that I wanted to do.
01:22:18 But I don’t categorically deny the possibility, and I think it should be investigated.
01:22:23 Yeah, I mean, this is one of those phenomena that 99.9% of people are almost definitely,
01:22:31 there’s conventional explanations, and then there’s like mysterious things that probably
01:22:38 have explanations that are a little bit more complicated, but there’s not enough to work
01:22:45 with.
01:22:46 I tend to believe that if aliens showed up, there will be plenty of evidence for scientists
01:22:52 to study.
01:22:53 Yeah.
01:22:54 And exactly as you said, avoid your type of spacecraft that could see sort of some kind
01:23:03 of, kind of a dumb thing, almost like a sensor that’s like probing, like statistically speaking.
01:23:09 Flying by.
01:23:10 Flying by, maybe lands, maybe there’s some kind of robot type of thingies that just like
01:23:13 move around and so on, like in ways that we don’t understand.
01:23:17 But I feel like, well, I feel like there’ll be plenty of hard, hard to dismiss evidence.
01:23:27 And I also, especially this year, believe that the US government is not sufficiently
01:23:33 competent given the huge amount of evidence that will be revealed from this kind of thing
01:23:39 to conceal all of it.
01:23:41 Right.
01:23:42 At least in modern times, you can say maybe decades ago, but in modern times.
01:23:46 Right, you know, the people I speak to and the reason I bring it up is because so many
01:23:51 people write to me, they’re inspired by it.
01:23:53 By the way, I wanted to comment on something you said earlier on, yeah, I had said that
01:23:57 I’m sort of a pessimist in that I think there are very few other intelligent, mechanically
01:24:03 able creatures out there.
01:24:06 But then I said, yes, in a sense, I’m an optimist, as you pointed out, because it means
01:24:10 that we made it through the great filter.
01:24:13 Right.
01:24:14 I meant originally that I’m a pessimist in that I’m pessimistic about the possibility
01:24:19 that there are many, many of us out there, you know, mathematically speaking in the Drake
01:24:23 equation.
01:24:24 Exactly.
01:24:25 Right.
01:24:26 Right.
01:24:27 But it may mean a good thing for our ultimate survival.
01:24:28 Right.
01:24:29 So I’m glad you caught me on that.
01:24:30 Yeah, I definitely agree with you.
01:24:32 It is ultimately an optimistic statement.
01:24:34 But anyway, I think, you know, UFO research is interesting.
01:24:38 And I guess one of the reasons I’ve not been terribly convinced is that I think there are
01:24:43 some scientists who are investigating this and they’ve not found any clear evidence.
01:24:49 Now, I must admit, I have not looked through the literature to convince myself that there
01:24:53 are many scientists doing systematic studies of these various reports.
01:24:58 I can’t say for sure that there’s a critical mass of them, but it’s just that you never
01:25:03 get these reports from hardcore scientists.
01:25:06 That’s another thing.
01:25:07 And astronomers, you know, what do we do?
01:25:08 We spend our time studying the heavens and you’d think we’d be the ones that are most
01:25:12 likely aside from pilots, perhaps, at seeing weird things in the sky.
01:25:17 And we just never do of the unexplained UFO type nature.
01:25:22 Yeah, I definitely, I try to keep an open mind, but for people who listen, it’s actually
01:25:28 really difficult for scientists.
01:25:30 Like I get probably like this year, I’ve probably gotten over probably maybe over a thousand
01:25:38 emails on the topic of AGI.
01:25:42 It’s very difficult to, you know, people write to me, it’s like, how can you ignore this
01:25:48 in AGI side?
01:25:49 Like this model, this is obviously the model that’s going to achieve general intelligence.
01:25:53 How can you ignore it?
01:25:54 I’m giving you the answer.
01:25:55 Here’s my document.
01:25:56 And they’re always just these large write ups.
01:26:00 The problem is it’s very difficult to weed through a bunch of BS.
01:26:07 It’s very possible that you had actually saw the UFO, but you have to acknowledge that
01:26:15 by UFO, I mean, an extraterrestrial life, you have to acknowledge the hundreds of thousands
01:26:20 of people who are a little bit, if not a lot full of BS.
01:26:26 And from a scientist perspective, it’s really hard work and it’s when there’s amazing stuff
01:26:33 out there, it’s like, why invest in Bigfoot when evolution in all of its richness is beautiful?
01:26:40 Who cares about a monkey that walks on two feet or eight or whatever?
01:26:43 Like there’s a zillion decoys at observatories.
01:26:47 True fact.
01:26:48 We get lots and lots of phone calls when Venus, the evening star, but just really a bright
01:26:55 planet happens to be close to the crescent moon because it’s such a striking pair.
01:27:00 This happens once in a while.
01:27:01 And we get these phone calls, oh, there’s a UFO next to the moon.
01:27:04 And no, it’s Venus.
01:27:06 And so they’re just and I’m not saying the best UFO reports are of that nature.
01:27:12 No, there are some much more convincing cases.
01:27:14 And I’ve seen some of the footage and blah, blah, blah.
01:27:17 But it’s just there’s so many decoys, right?
01:27:19 So much so much noise that you have to filter out.
01:27:22 And there’s only so many scientists.
01:27:23 So it’s hard.
01:27:24 There’s only so much.
01:27:25 There’s only so much time as well.
01:27:27 And you have to choose what problems you work on.
01:27:30 You know, this might be a fun question to ask to kind of explore the idea of the expanding
01:27:37 universe.
01:27:38 Yeah.
01:27:39 So the the radius of the observable universe is 45.7 billion light years.
01:27:46 Yeah.
01:27:47 And the age of the universe is 13.7 billion years.
01:27:56 That’s less than the radius of the universe.
01:28:00 How’s that possible?
01:28:01 So that’s a great question.
01:28:03 So I meant to bring a little a little prop I have with ping pong balls on a rubber hose,
01:28:08 a rubber band.
01:28:09 I use it in many of the lectures that one can find of me online.
01:28:14 But you have in an expanding universe, the space itself between galaxies or more correctly,
01:28:20 clusters of galaxies expanding.
01:28:23 So imagine light going from one cluster to another.
01:28:27 It traverses some distance and then while it’s traversing the rest, that part that it
01:28:33 already traveled through continues to expand.
01:28:38 Now 13.7 billion years might have gone by since the light that we are seeing from the
01:28:47 early stages, the so called cosmic microwave background radiation, which is the afterglow
01:28:52 of the Big Bang or the echo of the Big Bang.
01:28:54 Yeah, 13.7 billion years have gone by.
01:28:57 That’s how long it’s taken that light to reach us.
01:29:00 But while it’s been traveling that distance, the parts that it already traveled continue
01:29:06 to expand.
01:29:08 So it’s like you’re walking on at an airport, you know, on one of these walkways and you’re
01:29:13 walking along because you’re trying to get to your terminal.
01:29:16 But the walkway is continuing as well.
01:29:19 You end up traveling a greater distance or the same distance faster is another way of
01:29:24 putting it, right?
01:29:25 That’s why you get on one of these traveling walkways.
01:29:28 So you get roughly a factor of pi, you know, but it’s more like 3.2, I think.
01:29:33 But when you work it all out, you multiply the number of years the universe has been
01:29:38 in existence by, you know, three and a quarter or so.
01:29:42 And that’s how you get this 46 billion light year radius.
01:29:48 But how is that, let me ask some nice dumb questions, how is that not traveling faster
01:29:56 than the speed of light?
01:29:57 Yeah, it’s not traveling faster than the speed of light because locally at any point, if
01:30:01 you were to measure the light, the photons zipping past, it would not be exceeding the
01:30:06 speed of light.
01:30:08 The speed of light is a locally measured quantity.
01:30:11 After light has traversed some distance, if the rubber band keeps on stretching, then
01:30:16 yes, it looks like the light traveled a greater distance than it would have had the space
01:30:23 not been expanding.
01:30:25 But locally, it never was exceeding the speed of light.
01:30:28 It’s just that the distance through which it already traveled then went off and expanded
01:30:32 on its own some more.
01:30:35 And if you give the light credit, so to speak, for having traversed that distance, well,
01:30:40 then it looks like it’s going faster than the speed of light.
01:30:43 But that’s not how speed works.
01:30:47 And in relativity, also, the other thing that is interesting is that if you take two ping
01:30:54 pong balls that are sufficiently far apart, especially in an accelerating universe, you
01:30:59 can easily have them moving apart from one another faster than the speed of light.
01:31:03 So take two ping pong balls that were originally 400,000 kilometers from each other and let
01:31:09 every centimeter in your rubber band expand to two in one second.
01:31:14 Then suddenly, this 400,000 kilometer distance is 800,000 kilometers.
01:31:20 It went out by 400,000 kilometers in one second.
01:31:24 That exceeds the 300,000 kilometer per second speed of light.
01:31:29 But that light limit, that particle limit in special relativity, applies to objects
01:31:36 moving through a preexisting space.
01:31:39 There’s nothing in either special or general relativity that prevents space itself from
01:31:46 expanding faster than the speed of light.
01:31:48 That’s no problem.
01:31:49 Einstein wouldn’t have had a problem with a universe as observed now by cosmologists.
01:31:55 Yeah, I’m not sure I’m yet ready to deal emotionally with expanding space.
01:32:04 That to me is one of the most awe inspiring things, starting from the Big Bang.
01:32:09 It’s definitely abstract.
01:32:11 Space itself is expanding.
01:32:13 Right.
01:32:14 Could you, can we talk about the Big Bang a little bit?
01:32:18 Sure.
01:32:19 Yeah, yeah.
01:32:20 What, so like the entirety of it, the universe, was very small.
01:32:27 Right.
01:32:28 But it was not a point.
01:32:29 It was not a point.
01:32:31 Because if we live in what’s called a closed universe now, a sphere or the three dimensional
01:32:36 version of that would be a hypersphere, then regardless of how far back in time you go,
01:32:43 it was always that topological shape.
01:32:45 You can’t turn a point suddenly into a shell, okay?
01:32:49 It always had to be a shell.
01:32:52 So when people say, well, the universe started out as a point, that’s being kind of flippant,
01:32:57 kind of glib.
01:32:58 It didn’t really.
01:32:59 It just started out at a very high density.
01:33:02 And we don’t know actually whether it was finite or infinite, I think personally that
01:33:06 it was finite at the time, but it expanded very, very quickly.
01:33:10 Indeed, if it exponentiated and continued in some places to exponentiate, then it could
01:33:16 in fact be infinite right now.
01:33:18 And most cosmologists think that it is infinite.
01:33:20 Wait, wait, wait.
01:33:21 Yeah, sorry.
01:33:22 What infinite, which dimension, mass, size?
01:33:25 Infinite in space.
01:33:26 Infinite in space.
01:33:27 And by that I mean that if you were trying to measure.
01:33:29 There’s no boundary.
01:33:30 There’s no light to measure its size.
01:33:33 You’d never be able to measure its size because it would always be bigger than the distance
01:33:37 light can travel.
01:33:39 That’s what you get in a universe that’s accelerating in its expansion.
01:33:42 Okay.
01:33:43 But if a thing was a hypersphere, it’s very small, not a point, how can that thing be
01:33:50 infinite?
01:33:51 Well, it expands exponentially.
01:33:54 That’s what the inflation theory is all about.
01:33:56 Indeed, at your home institution, Alan Guth is one of the originators of the whole inflationary
01:34:01 universe idea, along with Andre Linde at Stanford University here in the Bay Area.
01:34:07 And others, Alexei Starobinsky and others had similar sorts of ideas.
01:34:11 But in an exponentially expanding universe, if you actually try to make this measurement,
01:34:17 you send light out to try to see it curve back around and hit you in the back of the
01:34:22 head.
01:34:23 But in an exponentially expanding universe, the amount of space remaining to be traversed
01:34:29 is always a bigger and bigger quantity.
01:34:32 So you’ll never get there from here.
01:34:34 You’ll never reach the back of your head.
01:34:35 So observationally or operationally, it can be thought of as being infinite.
01:34:41 That’s one of the best definitions of infinity, by the way.
01:34:43 What’s that?
01:34:44 That’s one of the best sort of physical manifestations of infinity.
01:34:49 Yeah, yeah.
01:34:50 Because you have to ask, how would you actually measure it?
01:34:53 Now, I sometimes say to my cosmology theoretical friends, well, if I were God and I were outside
01:34:58 this whole thing and I took a godlike slice in time, wouldn’t it be finite no matter how
01:35:05 big it is?
01:35:06 And they object and they say, Alex, you can’t be outside and take a godlike slice of time,
01:35:13 you know?
01:35:14 Because there’s nothing outside.
01:35:15 Well, I’m not, you know, or also, you know, what slice of time you’re taking depends on
01:35:22 your motion.
01:35:23 And that’s true even in special relativity that slices of time get tilted, in a sense,
01:35:28 if you’re moving quickly, the axes, x and t actually become tilted, not perpendicular
01:35:36 to one another.
01:35:37 And you can look at Brian Greene’s books and lectures and other things where he imagines
01:35:43 taking a loaf of bread and slicing it in units of time as you progress forward.
01:35:50 But then if you’re zipping along relative to that loaf of bread, the slices of time
01:35:55 actually become tilted.
01:35:57 And so it’s not even clear what slices of time mean.
01:36:00 But I’m an observational astronomer, I know which end of the telescope to look through.
01:36:05 And the way I understand the infinity is, as I just told you, that operationally or
01:36:09 observationally, there’d be no way of seeing that it’s a finite universe, of measuring
01:36:16 a finite universe.
01:36:17 And so in that sense, it’s infinite, even if it started out as a finite little dot.
01:36:25 Not a dot, I’m sorry, a finite little hypersphere.
01:36:29 But it didn’t really start out there because what happened before that?
01:36:37 Well, we don’t know.
01:36:38 So this is where it gets into a lot of speculation.
01:36:41 Let’s go, I mean…
01:36:42 Let’s go there.
01:36:43 Okay, sure.
01:36:44 So, you know…
01:36:45 The idea of what happened before t equals zero and whether there are other universes
01:36:50 out there, I like to say that these are sort of on the boundaries of science.
01:36:55 They’re not just ideas that we wake up at three in the morning to go to the bathroom
01:36:58 and say, oh, well, let’s think about what happened before the Big Bang or let there
01:37:02 be a multiplicity of universes.
01:37:04 In other words, we have real testable physics that we can use to draw certain conclusions
01:37:12 that are plausibility arguments based on what we know.
01:37:16 Now, admittedly, there are not really direct tests of these hypotheses.
01:37:24 That’s why I call them hypotheses.
01:37:26 They’re not really elevated to a theory because a theory in science is really something that
01:37:30 has a lot of experimental or observational support behind it.
01:37:34 So they’re hypotheses, but they’re not unreasonable hypotheses based on what we know about general
01:37:41 relativity and quantum physics.
01:37:44 And they may have indirect tests in that if you adopt this hypothesis, then there might
01:37:49 be a bunch of things you expect of the universe, and lo and behold, that’s what we measure.
01:37:54 But we’re not actually measuring anything at t less than zero, or we’re not actually
01:38:00 measuring the presence of another universe in this multiverse, and yet there are these
01:38:05 indirect ideas that stem forth.
01:38:09 So it’s hard to prove uniqueness, and it’s hard to completely convince oneself that a
01:38:15 certain hypothesis must be true.
01:38:19 But the more and more tests you have that it satisfies, let’s say there are 50 predictions
01:38:24 it makes, and 49 of them are things that you can measure.
01:38:30 And then the 50th one is the one where you want to measure the actual existence of that
01:38:35 other universe, or what happened before t equals zero, and you can’t do that.
01:38:41 But you’ve satisfied 49 of the other testable predictions, and so that’s science, right?
01:38:49 Now a conventional condensed matter physicist or someone who deals with real data in the
01:38:53 laboratory might say, oh, you cosmologists, that’s not really science because it’s not
01:38:58 directly testable, but I would say it’s sort of testable.
01:39:02 But it’s not completely testable, and so it’s at the boundary, but it’s not like we’re coming
01:39:06 up with these crazy ideas, among them quantum fluctuations out of nothing, and then inflating
01:39:11 into a universe with, you might say, well, you created a giant amount of energy.
01:39:16 But in fact, this quantum fluctuation out of nothing in a quantum way violates the conservation
01:39:22 of energy.
01:39:23 But who cares?
01:39:24 That was a classical law anyway.
01:39:26 And then an inflating universe maintains whatever energy it had, be it zero or some infinitesimal
01:39:32 amount.
01:39:33 In a sense, the stuff of the universe has a positive energy, but there’s a negative
01:39:38 gravitational energy associated with it.
01:39:41 It’s like I drop an apple.
01:39:43 I got kinetic energy, energy of motion out of that, but I did work on it to bring it
01:39:47 to that height.
01:39:49 So by going down and gaining energy of motion, positive one, two, three, four, five units
01:39:55 of kinetic energy, it’s also gaining or losing, depending on how you want to think of it,
01:40:01 negative one, two, three, four, five units of potential energy, so the total energy remains
01:40:06 the same.
01:40:07 An inflating universe can do that, or other physicists say that energy isn’t conserved
01:40:12 in general relativity.
01:40:13 That’s another way out of creating a universe out of nothing.
01:40:17 But the point is that this is all based on reasonably well tested physics, and although
01:40:22 these extrapolations seem kind of outrageous at first, they’re not completely outrageous.
01:40:30 They’re within the realm of what we call science already.
01:40:33 And maybe some young whippersnapper will be able to figure out a way to directly test
01:40:39 what happened before T equals zero or to test for the presence of these other universes,
01:40:44 but right now we don’t have a way of doing that.
01:40:46 So speaking of young whippersnappers, Roger Penrose.
01:40:52 So he kind of has a, you know, idea that we, there may be some information that travels
01:40:58 from whatever the heck happened before the Big Bang.
01:41:00 Yeah, maybe.
01:41:01 I kind of doubt it.
01:41:03 So do you think it’s possible to detect something, like actually experimentally be able to detect
01:41:09 some, I don’t know what it is, radiation, some sort of…
01:41:13 Yeah, and the cosmic microwave background radiation, there may be ways of doing that.
01:41:18 But is it, is it philosophically or practically possible to detect signs that this was before
01:41:25 the Big Bang or is it, or is it what you said, which is like everything we observe will,
01:41:32 as we currently understand, will have to be a creation of this particular observable universe?
01:41:36 Yeah.
01:41:37 I mean, you know, if you, it’s very difficult to answer right now because we don’t have
01:41:40 a single verified, fully self consistent, experimentally tested quantum theory of gravity.
01:41:48 Right.
01:41:49 And of course the beginning of the universe is a large amount of stuff in a very small
01:41:53 space.
01:41:54 Yeah.
01:41:55 So you need both quantum mechanics and general relativity.
01:41:57 Same thing if our universe re collapses and then bounces back to another Big Bang.
01:42:01 You know, there’s also ideas there that some of the information leaks through or survives.
01:42:06 I don’t know that we can answer that question right now because we don’t have a quantum
01:42:11 theory of gravity that most physicists believe in.
01:42:15 And belief is perhaps the wrong word that most physicists trust because the experimental
01:42:20 evidence favors it.
01:42:22 Yeah.
01:42:23 Right?
01:42:24 Yeah.
01:42:25 There are various forms of string theory.
01:42:26 There’s quantum loop gravity.
01:42:27 There are various ideas, but which, if any, will be the one that survives the test of
01:42:33 time and more importantly, within that, the test of experiment and observation.
01:42:38 Yeah.
01:42:39 So my own feeling is probably these things don’t survive.
01:42:43 I don’t think we’ve seen any evidence in the cosmic microwave background radiation
01:42:47 of information leaking through.
01:42:50 Similarly, the one way or one of the few ways in which we might test for the presence of
01:42:55 other universes is if they were to collide with ours, that would leave a pattern, a temperature
01:43:02 signature in the cosmic microwave background radiation.
01:43:05 Some astrophysicists claim to have found it, but in my opinion, it’s not statistically
01:43:10 significant to the level that would be necessary to have such an amazing claim, right?
01:43:17 It’s just a 5% chance that the microwave background had that distribution just by chance.
01:43:22 5% isn’t very long odds if you’re claiming that instead that you’re finding evidence
01:43:32 from another universe.
01:43:33 I mean, it’s like if the Large Hadron Collider people had claimed after gathering enough
01:43:39 data to show the Higgs particle when there was a 5% chance it could be just a statistical
01:43:47 fluctuation in their data.
01:43:50 No, they required 5 sigma, 5 standard deviations, which is roughly one chance in 2 million that
01:43:57 this is a statistical fluctuation of no physical greater significance.
01:44:04 Extraordinary claims require extraordinary evidence.
01:44:05 There you go.
01:44:06 It all boils down to that.
01:44:07 And the greater your claim, the greater is the evidence that is needed and the more evidence
01:44:12 you need from independent ways of measuring or of coming to that deduction.
01:44:20 A good example was the accelerating universe.
01:44:23 When we found evidence for it in 1998 with supernovae with exploding stars, it was great
01:44:29 that there were two teams that lent some credibility to the discovery.
01:44:34 But it was not until other astrophysicists used not only that technique, but more importantly,
01:44:41 other independent techniques that had their own potential sources of systematic error
01:44:46 or whatever.
01:44:47 But they all came to the same conclusion and that started giving a much more complete picture
01:44:52 of what was going on and a picture in which most astrophysicists quickly gained confidence.
01:44:59 That’s why that idea caught on so quickly is that there were other physicists and astronomers
01:45:06 doing observations completely independent of supernovae that seemed to indicate the
01:45:11 same thing.
01:45:12 Yeah.
01:45:13 That period of your life that work with an incredible team of people that won the Nobel
01:45:22 Prize is just fascinating work.
01:45:25 Oh gosh.
01:45:26 Never in my wildest dreams as a kid did I think that I would be involved, much less
01:45:33 so heavily involved, in a discovery that’s so revolutionary.
01:45:37 As a kid, as a scientist, if you’re realistic, once you learn a little bit more about how
01:45:41 science is done and you’re not going to win a Nobel Prize and be the next Newton or Einstein
01:45:45 or whatever, you just hope that you’ll contribute something to humankind’s understanding of
01:45:51 how nature works and you’ll be satisfied with that.
01:45:55 But here I was in the right place at the right time, a lot of luck, a lot of hard work, and
01:46:01 there it was.
01:46:02 We discovered something that was really amazing and that was the greatest thrill, right?
01:46:08 I couldn’t have asked for anything more than being involved in that discovery.
01:46:14 So the couple of teams, the Supernova Cosmology Project and the HiZ Supernova Search Team,
01:46:20 what was the Nobel Prize given for?
01:46:21 It was given for the discovery of the accelerating expansion of the universe, not for the elucidation
01:46:27 of what dark energy is or what causes that expansion, that acceleration, be it universes
01:46:33 on the outside or whatever, it was only for the observational fact.
01:46:36 So first of all, what is the accelerating universe?
01:46:39 So the accelerating universe is simply that if we look at the galaxies moving away from
01:46:45 us right now, we would expect them to be moving away more slowly than they were billions of
01:46:52 years ago.
01:46:53 That’s because galaxies have visible matter, which is gravitationally attractive, and dark
01:46:58 matter of an unknown sort that holds galaxies together and holds clusters of galaxies together.
01:47:04 And of course, they then pull on one another and they would tend to retard the expansion
01:47:09 of the universe.
01:47:10 Just as when I toss an apple up, even ignoring air resistance, the mutual gravitational attraction
01:47:17 between Earth and the apple slows the apple down.
01:47:20 If that attraction is great enough, then the apple will someday stop and even come back.
01:47:24 The Big Crunch, you could call it, or the Gnab Gibb, which is Big Bang backwards, right?
01:47:29 That’s what could have happened to the universe.
01:47:30 But even if the universe’s original expansion energy was so great that it avoids the Big
01:47:36 Crunch, that’s like an apple thrown at Earth’s escape speed.
01:47:39 It’s like the rockets that go to Mars someday, right, with people.
01:47:47 Even then, you’d expect the universe to be slowing down with time.
01:47:50 But we looked back through the history of the universe by looking at progressively more
01:47:55 distant galaxies and by seeing that the evolution of this expansion rate is that in the first
01:48:06 nine billion years, yeah, it was slowing down.
01:48:09 But in the last five billion years, it’s been speeding up.
01:48:13 So who asked for that, right, you know?
01:48:17 I think it’s interesting to talk about a little bit of the human story of the Nobel Prize,
01:48:22 which is, I mean, it’s fascinating.
01:48:24 It’s a really, first of all, the prize itself.
01:48:27 It’s kind of fascinating on the psychological level that prizes, I know we kind of think
01:48:34 that prizes don’t matter, but somehow they kind of focus the mind about some of the most
01:48:38 special things we’ve accomplished.
01:48:39 They do.
01:48:40 It’s the recognition, the funding, you know.
01:48:43 And also inspiration for, like I said, when I was a little kid, thinking about the Nobel
01:48:47 Prize, like I didn’t, you know, it inspires millions of young scientists.
01:48:53 At the same time, there’s a sadness to it a little bit that, especially in the field,
01:48:59 like depending on the field, but experimental fields that involve teams of, I don’t know,
01:49:04 sometimes hundreds of brilliant people, the Nobel Prize is only given to just a handful.
01:49:12 That’s right.
01:49:13 Is it maxed at three?
01:49:14 Yeah.
01:49:15 Yeah.
01:49:16 And it’s not even written in Alfred Nobel’s will, it turns out.
01:49:18 One of our teammates looked into it in a museum in Stockholm when we went there for Nobel
01:49:23 Week in 2011.
01:49:25 The leaders who got the prize formally knew that without the rest of us working hard in
01:49:30 the trenches, the result would not have been discovered.
01:49:35 So they invited us to participate in Nobel Week.
01:49:37 And so one of the team members looked in the will and it’s not there.
01:49:41 It’s just tradition.
01:49:42 That’s interesting.
01:49:43 But it’s archaic, you know, that’s the way science used to be done.
01:49:47 It’s not the way a lot of science is done now.
01:49:49 And you look at gravitational wave discovery, which was, you know, recognized with the Nobel
01:49:54 Prize in 2017, Ray Weiss at MIT got it and Kip Thorne and Barry Barish at Caltech.
01:50:03 And Ron Drever, one of the masterminds, had passed away earlier in the year.
01:50:07 So again, one of the rules of Nobel is that it’s not given posthumously, or at least the
01:50:13 one exception might be if they’ve made their decision and they’re busy making their press
01:50:17 releases right before October, the first week in October or whatever, and then the person
01:50:23 passes away.
01:50:24 I think they don’t change their minds then.
01:50:25 But yeah, you know, it doesn’t square with today’s reality that a lot of science is done
01:50:32 by big teams, in that case, a team of a thousand people.
01:50:35 In our case, it was two teams consisting of about 50 people.
01:50:40 And we used techniques that were arguably developed in part by people who, astrophysicists
01:50:46 who weren’t even on those two papers, I mean, some of them were, but other papers were written
01:50:51 by other people, you know, and so it’s like we’re standing on the shoulders of giants.
01:50:56 And none of those people was officially recognized.
01:50:59 And to me, it was okay.
01:51:01 You know, again, it was the thrill of doing the work and ultimately the work, the discovery
01:51:06 was recognized with the prize.
01:51:08 And you know, we got to participate in Nobel week and, you know, it’s okay with me.
01:51:14 I’ve known other physicists whose lives were ruined because they did not get the Nobel
01:51:20 prize and they felt strongly that they should have.
01:51:23 Ralph Alpher of the Alpher beta gamma paper predicting the microwave background radiation,
01:51:31 we should have gotten it.
01:51:33 His advisor Gamoff was dead by that point.
01:51:36 But you know, Penzias and Wilson got it for the discovery and an Alpher, apparently from
01:51:42 colleagues who knew him well, I’ve talked to them.
01:51:45 His life was ruined by this.
01:51:46 He just, it just not at his innards so much.
01:51:50 It’s very possible that in a small handful of people, even three, that you would be one
01:51:56 of the Nobel, one of the winners of the Nobel prize.
01:51:59 That doesn’t weigh heavy on you.
01:52:00 Well, you know, there were the two team leaders, Saul Perlmutter and Brian Schmidt.
01:52:05 And usually there’s the team leaders that are recognized.
01:52:07 And then Adam Rees was my postdoc.
01:52:10 First author, I guess.
01:52:11 Yeah.
01:52:12 First author.
01:52:13 I was second author of that paper.
01:52:14 Yeah.
01:52:15 So I was his direct mentor at the time.
01:52:16 Although he was, you know, one of these people who just, you know, runs with things.
01:52:19 He was an MIT undergraduate by the way, Harvard graduate student, and then a postdoc as a
01:52:26 so called Miller fellow for basic research and science at Berkeley, something that I
01:52:30 was back in 84 to 86.
01:52:33 But you’re, you know, you’re largely a free agent, but he worked quite closely with me
01:52:37 and he came to Berkeley to work with me and on Schmidt’s team, he was charged with analyzing
01:52:43 the data and he measured the brightnesses of these distant supernovae showing that they’re
01:52:48 fainter and thus more distant than anticipated.
01:52:51 And that led to this conclusion that the universe had to have accelerated in order to push them
01:52:56 out to such great distances.
01:52:58 And I was shocked when he showed me the data, the results of his calculations and measurements.
01:53:04 But it’s very, you know, so he deserved it.
01:53:07 And on Sol’s team, Gerson Goldhaber deserved it.
01:53:10 But he died, I think a year earlier in 2010, but that would have been four.
01:53:14 And so, and me, well, I was on both teams, but, you know, was I number four, five, six,
01:53:21 seven?
01:53:22 I don’t know.
01:53:23 It’s also very, so if I were to, it’s possible that you’re, I mean, I can make a very good
01:53:28 case for urine in the three.
01:53:31 And does that, is that psychologically, I mean, listen, it weighs on me a little bit
01:53:38 because I don’t know what to do with that.
01:53:44 Perhaps it should motivate the rethinking, like Time magazine started doing like, you
01:53:51 know, person of the year and like they would start doing like concepts and almost like
01:53:56 the black hole gets the Nobel prize or the universe gets the Nobel prize and here’s the
01:54:02 list of people.
01:54:03 So like, or like the Oscar that you could say, because it’s a team effort now and it
01:54:11 should be redone.
01:54:12 And the breakthrough prize in fundamental physics, which was started by Yuri Milner
01:54:16 and Zuckerberg is involved in others as well, you know, uh, they recognize the larger team.
01:54:22 Yeah, they, they recognize teams.
01:54:24 And so in fact, both teams in the accelerating universe were recognized with the breakthrough
01:54:28 prize in 2015.
01:54:31 Nevertheless, the same three people, Reese Perlmutter and Schmidt got the red carpet
01:54:37 rolled out for them and were at the big ceremony and shared half of the prize money.
01:54:43 And the rest of us, roughly 50 shared the other half and didn’t get to go to the ceremony.
01:54:48 So, but I, I feel for them, I mean, for the gravitational waves, it was a thousand people.
01:54:52 What are they going to do?
01:54:53 Invite everyone for the Higgs particle.
01:54:55 It was six to 8,000 physicists and engineers.
01:54:58 In fact, because of the whole issue of who gets it experimentally, that discovery still
01:55:04 has not been recognized, right?
01:55:06 The theoretical work by Peter Higgs and, uh, Anglaire got recognized, but there was a troika
01:55:13 of other people who perhaps wrote the most complete paper and they were, they were left
01:55:18 out and, um, another guy died, you know, and
01:55:22 it’s hard.
01:55:23 It’s all of his heartbreak.
01:55:24 And some people argue that the Nobel prize has been diluted too, because if you look
01:55:28 at Roger Penrose, you can make an argument that he should get the prize by himself.
01:55:33 Like it’s just separate those, like he could have and should have, perhaps he should have
01:55:37 perhaps gotten it with Hawking before Hawking’s death, right?
01:55:41 The problem was Hawking radiation had not been detected, but you could argue that Hawking
01:55:46 made enough other fundamental contributions to the theoretical study of black holes and
01:55:52 the observed data were already good enough at the time of before Hawking’s death.
01:55:57 Okay.
01:55:58 I mean, the latest results by Reinhard Genzel’s group is that they see the time dilation effect
01:56:03 of a star that’s passing very close to the black hole in the middle of our galaxy.
01:56:07 That’s cool, but, and it adds additional evidence, but hardly anyone doubted the existence of
01:56:13 the supermassive black hole and Andrea Gaz’s group, I believe hadn’t yet shown that relativistic
01:56:18 effect and yet she got part of the prize as well.
01:56:21 So clearly it was given for the, the original evidence that was really good.
01:56:25 And that evidence is at least a decade old, you know, so one could make the case for,
01:56:30 for Hawking, one could make the case that in 2016, when Mayor and Caloz won the Nobel
01:56:37 Prize for the discovery of the first exoplanet, 51B Pegasi, well, there was a fellow at Penn
01:56:45 State, Alex Wolszczan, who in 1992, three years preceding 1995, found a planet orbiting
01:56:55 a pulsar, a very weird kind of star, a neutron star, and that wouldn’t have been a normal
01:56:59 planet.
01:57:00 Sure.
01:57:01 And so the Nobel committee, you know, they gave it for the discovery of planets around
01:57:05 normal sun like stars, but, but hell, you know, Wolszczan found a planet so they could
01:57:11 have given it to him as the third person instead of to Jim Peebles for the development of what’s
01:57:16 called physical cosmology.
01:57:18 He’s at Princeton, he deserved it, but they could have given Nobel for the development
01:57:22 of physical cosmology to Peebles and I would claim some other people were pretty important
01:57:27 in that development as well.
01:57:29 You know, and they could have given it some other year.
01:57:32 So there’s, there’s a lot of controversy.
01:57:35 I try not to dwell on it.
01:57:36 Was I number three?
01:57:37 Probably not.
01:57:38 You know, Adam Riess did the work.
01:57:40 You know, I helped bounce ideas off of him, but we wouldn’t have had the result without
01:57:46 him.
01:57:47 Yeah.
01:57:48 And I was on both teams for reasons, I mean, you know, I, the style of the first team,
01:57:53 the supernova cosmology project didn’t match mine.
01:57:56 They came largely from experimental high energy particle physics, physics where there’s these
01:58:00 hierarchical teams and stuff and it’s hard for the little guy to have a say, at least
01:58:05 that’s what I kind of thought.
01:58:06 Whereas the team of astronomers led by Brian Schmidt was first of all, a bunch of my friends
01:58:12 and they grew up as astronomers making contributions on little teams and we decided to band together,
01:58:18 but all of us had our voices heard.
01:58:20 So it was sort of a culture, a style that I preferred really.
01:58:25 But let me tell you a story at the Nobel banquet, okay?
01:58:30 I’m sitting there between two physicists who are members of the committee of the Swedish
01:58:35 National Academy of Sciences, you know, and I strategically kept, you know, offering them
01:58:39 wine and stuff during this long drawn out Nobel ceremony, right?
01:58:45 And I got them to be pretty talkative and then in a polite diplomatic way, I started
01:58:50 asking them pointed questions and basically they admitted that if there are four or more
01:58:55 people equally deserving, they wait for one of them to die or they just don’t give the
01:59:01 prize at all when it’s unclear who the three are, at least unclear to them.
01:59:07 But unclear to them, they’re not even right part of the time.
01:59:12 I mean, Jocelyn Bell discovered pulsars with a radio antenna, a set of radio antennas that
01:59:20 her advisor Anthony Hewish conceived and built, so he deserves some credit, but he didn’t
01:59:28 discover the pulsar.
01:59:30 She did.
01:59:31 And his initial reaction to the data that she showed him was a condescending rubbish,
01:59:38 my dear.
01:59:39 Yeah, I’m not kidding.
01:59:41 Now, I know Jocelyn Bell and she did not let this destroy her life.
01:59:46 She won every other prize under the sun, okay?
01:59:51 Vera Rubin, arguably one of the discoverers of dark matter, although there, if you look
01:59:57 at the history, there were a number of people and that was the issue, I think there were
02:00:00 a number of people, four or more who had similar data and similar ideas at about the same time.
02:00:06 Rubin won every prize under the sun, the new big large scale survey telescope being built
02:00:12 in Chile is being renamed the Vera Rubin Telescope because she passed away in December of 2015,
02:00:19 I think.
02:00:21 You know, it’ll conduct this survey, large scale survey with the Rubin Telescope.
02:00:26 So she’s been recognized, but never with the Nobel Prize.
02:00:30 And I would say that to her credit, she did not let that consume her life either.
02:00:36 And perhaps it was a bit easier because there had been no Nobel given for the discovery
02:00:41 of dark matter, whereas in the case of pulsars and Jocelyn Bell, there was a prize given
02:00:46 for the discovery of the freaking pulsars and she didn’t get it.
02:00:50 Well, I mean, what a travesty of justice.
02:00:53 So I also think as a fan of fiction, as a fan of stories that the travesty and the tragedy
02:01:01 and the unfairness and the tension of it is what makes the prize and similar prizes beautiful.
02:01:11 The decisions of other humans that result in dreams being broken and, you know, like
02:01:19 that’s why we love the Olympics as so many, you know, people, athletes give their whole
02:01:24 life for this particular moment and then there’s referee decisions and like little slips of
02:01:31 here and there, like the little misfortunes that destroy entire dreams.
02:01:36 And that’s, it’s, it’s weird to say, but it feels like that makes the entirety of it even
02:01:42 more special.
02:01:43 Yeah.
02:01:44 If it was perfect, it wouldn’t be interesting.
02:01:46 Humans like competition and they like heroes and unfortunately it gives the impression
02:01:51 to youngsters today that science is still done by white men with gray beards wearing
02:01:57 white lab coats.
02:01:59 And I’m very pleased to see that this year, you know, Andrea Ghez, the fourth woman in
02:02:04 the history of the physics prize to have received it.
02:02:07 And then two women, one at Berkeley, one elsewhere won the Nobel prize in chemistry without any
02:02:14 male co recipient.
02:02:16 And so that’s sending a message I think to girls that they can do science and they have
02:02:21 role models.
02:02:23 I think the breakthrough prize and other such prizes show that teams get recognized as well.
02:02:31 And if you pay attention to the newspapers, you know, most of the good authors like, you
02:02:37 know, Dennis Overby of the New York Times and others said that these were teams of people
02:02:41 and they, they emphasize that and, you know, they all played a role.
02:02:46 And you know, maybe if some grad student hadn’t soldered some circuit, maybe the whole thing
02:02:49 wouldn’t have worked, you know.
02:02:52 But still, you know, Ray Weiss and Kip Thorne was the theoretical, you know, impetus for
02:02:59 the whole search for gravitational waves, Barry Barish brought the MIT and Caltech teams
02:03:05 together to get them to cooperate at a time when the project was nearly dead from what
02:03:11 I understand and contributed greatly to the experimental setup as well.
02:03:16 He’s a great experimental physicist, but he was really good at bringing these two teams
02:03:20 together instead of having them duke it out in blows and leaving both of them bleeding
02:03:24 and dying.
02:03:25 You know, the National Science Foundation was going to cut the funding from what I understand,
02:03:29 you know.
02:03:30 So, so there’s human drama involved in this whole thing.
02:03:33 And the Olympics, yeah, you know, a runner, a swimmer, a runner, runner, you know, they
02:03:38 slip just at the moment that they were taking off from the first thing and that costs them
02:03:43 some fraction of a second and that’s it.
02:03:46 They didn’t win, you know.
02:03:47 And in that case, I mean, the coaches, the families, which I met a lot of Olympic athletes
02:03:53 and the coaches and the families of the athletes are really the winners of the medals.
02:04:01 But they don’t get the medal and it’s, you know, credit assignment is a fascinating thing.
02:04:06 I mean, that’s the full human story we have.
02:04:10 And outside of prizes, it’s fascinating.
02:04:13 I mean, just to be in the middle of it for artificial intelligence, there’s a field of
02:04:18 deep learning.
02:04:19 That’s really exciting.
02:04:20 And people have been, there’s yet another award, the touring awards given for deep learning
02:04:26 to three folks who are very much responsible for the field, but so are a lot of others.
02:04:32 Yeah, that’s right.
02:04:33 And there’s a few, there’s a, there’s a fellow by the name of Schmidt Huber who sort of symbolizes
02:04:43 the, the forgotten folks in the deep learning community.
02:04:48 But you know, that’s, that’s the unfortunate sad thing where you remember, remember Isaac
02:04:55 Newton or remember these, these, these special figures and the ones that flew close to them,
02:05:04 we forget.
02:05:05 Well, that’s right.
02:05:06 And you know, often the breakthroughs are made based on the body of knowledge that had
02:05:10 been assimilated prior to that.
02:05:13 But you know, again, people like to worship heroes.
02:05:15 You mentioned the Oscars earlier and you know, you look at the direct, I mean, well, I mean,
02:05:21 okay, directors and stuff sometimes get awards and stuff, but you know, you look at even
02:05:26 something like, I don’t know, songwriters, musicians, Elton John or something, right?
02:05:30 Bernie Taupin, right?
02:05:32 Wrote many of the words or he’s not as well known or the Beatles or something like that.
02:05:39 I was heartbroken to learn that Elvis didn’t write most of the songs.
02:05:43 Yeah, Elvis.
02:05:44 That’s right.
02:05:45 There you go.
02:05:46 But he was the king, right?
02:05:47 And he had such a personality and it was such a performer, right?
02:05:50 But it’s the unsung heroes in many cases.
02:05:53 Yeah.
02:05:54 So maybe taking a step back, we talked about the Nobel prize of the accelerating universe,
02:06:00 but your work and the ideas around supernova were important in detecting this accelerating
02:06:11 universe.
02:06:12 Can we go to the very basics of what is this beautiful, mysterious object of a supernova?
02:06:17 Right.
02:06:18 So a supernova is an exploding star.
02:06:21 Most stars die a relatively quiet death, our own sun, well, despite the fact that it’ll
02:06:25 become a red giant and incinerate earth, it’ll do that reasonably slowly.
02:06:30 But there’s a small minority of stars that end their lives in a Titanic explosion.
02:06:35 And that’s not only exciting to watch from afar, but it’s critical to our existence because
02:06:40 it is in these explosions that the heavy elements synthesize through nuclear reactions during
02:06:46 the normal course of the star’s evolution and during the explosion itself, get injected
02:06:52 into the cosmos, making them available as raw material for new stars, planets, and ultimately
02:06:59 life.
02:07:00 And that’s just a great story, the best in some ways.
02:07:04 So we like to study these things and our origins, but it turns out these are incredibly useful
02:07:11 beacons as well, because if you know how powerful an exploding star really is by measuring the
02:07:19 apparent brightness at its peak in galaxies whose distances we already know through having
02:07:25 made other measurements, and you can thus calibrate how powerful the thing really is,
02:07:32 and then you find ones that are much more distant, then you can use their observed brightness
02:07:38 compared with their true intrinsic power or luminosity to judge their distance and hence
02:07:43 the distance of the galaxy in which they’re located.
02:07:49 Let me just give this one analogy.
02:07:51 You judge the distance of an oncoming car at night by looking at how bright its headlights
02:07:57 appear to be, and you’ve calibrated how bright the headlights are of a car that’s two or
02:08:02 three meters away of known distance, and you go, oh, that’s a faint headlight, and so that’s
02:08:07 pretty far away.
02:08:09 You also use the apparent angular separation between the two headlights as a consistency
02:08:14 check in your brain, but that’s what your brain is doing.
02:08:16 So we can do that for cars, we can do that for stars.
02:08:19 Nice, I like that.
02:08:21 But you know, with cars, the headlights are all, there’s some variation, but they’re somewhat
02:08:28 similar so you can make those kinds of conclusions.
02:08:32 How much variation is there between supernova that you can detect them?
02:08:38 Right, so first of all, there are several different ways that stars can explode, and
02:08:42 it depends on their mass and whether they’re in a binary system and things like that.
02:08:47 And the ones that we used for these cosmological purposes, studying the expansion of the history
02:08:52 of the universe, are the so called type Roman numeral I, lowercase a, type Ia supernovae.
02:09:00 They come from a weird type of a star called a white dwarf.
02:09:04 Our own sun will turn into a white dwarf in about seven billion years.
02:09:09 It’ll have about half its present mass compressed into a volume just the size of Earth.
02:09:14 So that’s an inordinate density, okay?
02:09:17 It’s incredibly dense.
02:09:18 And the matter is what’s called by quantum physicists degenerate matter, not because
02:09:23 it’s morally reprehensible or anything like that, but this is just the name that quantum
02:09:28 physicists give to electrons that are squeezed into a very tight space.
02:09:33 The electrons take on a motion due to Heisenberg’s uncertainty principle, and also due to the
02:09:39 Pauli exclusion principle that electrons don’t like to be in the same place, they like to
02:09:43 avoid each other.
02:09:44 And those two things mean that a lot of electrons are moving very rapidly, which gives the star
02:09:50 an extra pressure far above the thermal pressure associated with just the random motions of
02:09:56 particles inside the star.
02:09:57 So it’s a weird type of star, but normally it wouldn’t explode and our sun won’t explode,
02:10:04 except that if such a white dwarf is in a pair with another more or less normal star,
02:10:10 it can steal material from that normal star until it gets to an unstable limit, roughly
02:10:18 one and a half times the mass of our sun, 1.4 or so.
02:10:22 This is known as the Chandrasekhar limit after Subramanian Chandrasekhar, an Indian astrophysicist
02:10:29 who figured this out when he was about 20 years old on a voyage from India to England
02:10:34 where he was to be educated.
02:10:37 And then he did this and then 50 years later he won the Nobel Prize in physics in 1984
02:10:42 largely for this work that he did as a youngster who was on his way to be educated.
02:10:48 And his advisor, the great Arthur Eddington in England, who had done a lot of great things
02:10:54 and was a great astrophysicist, nevertheless, he too was human and had his faults.
02:10:59 He ridiculed Chandra’s scientific work at a conference in England and most of us, if
02:11:07 we had been Chandra, would have just given up astrophysics at that time when the great
02:11:12 Arthur Eddington ridicules our work.
02:11:16 That’s another inspirational story for the youngster.
02:11:19 Just keep going.
02:11:20 But anyway, no matter what your advisor says or don’t always pay attention to your advisor.
02:11:28 Don’t lose hope if you really think you’re onto something.
02:11:32 That doesn’t mean never listen to your advisor.
02:11:34 They may have sage advice as well.
02:11:36 But anyway, when a white dwarf grows to a certain mass, it becomes unstable.
02:11:43 And one of the ways it can end its life is to go through a thermonuclear runaway.
02:11:48 So basically, the carbon nuclei inside the white dwarf start fusing together to form
02:11:54 heavier nuclei.
02:11:56 And the energy that those fusion reactions emit doesn’t go into being dissipated out
02:12:06 of the star or expanding it the way if you take a blowtorch to the middle of the Sun,
02:12:14 you heat up its gases, the gases would expand and cool.
02:12:17 But this degenerate star can’t expand and cool.
02:12:21 And so the energy pumped in through these fusion reactions goes into making the nuclei
02:12:27 move faster.
02:12:28 And that gets more of them sufficiently close together that they can undergo nuclear fusion,
02:12:33 thereby releasing more energy that goes into speeding up more nuclei.
02:12:38 And thus you have a runaway, a bomb, an uncontrolled fusion reactor instead of the controlled fusion,
02:12:46 which is what our Sun does.
02:12:48 Our Sun is a marvelous controlled fusion reactor.
02:12:51 This is what we need here on Earth, fusion energy to solve our energy crisis, right?
02:12:56 But the Sun holds the stuff in through gravity and you need a big mass to do that.
02:13:01 So this uncontrolled fusion reaction blows up a star that’s pretty much the same in
02:13:07 all cases.
02:13:09 And you measure it to be almost the same in all cases.
02:13:13 But the devil is in the details, and in fact, we observe them to not be all the same.
02:13:18 And theoretically, they might not be all the same because the rate of the fusion reactions
02:13:23 might depend on the amount of trace heavier elements in the white dwarf.
02:13:28 And that could depend on how old it is, whether it was born billions of years ago when there
02:13:33 weren’t many heavier elements or whether it’s a relatively young white dwarf and all
02:13:38 kinds of other things.
02:13:40 And part of my work was to show that indeed, not all the Type Ia’s are the same.
02:13:44 You have to be careful when you use them.
02:13:47 You have to calibrate them.
02:13:49 They’re not standard candles the way it just, if all headlights or all candles were the
02:13:55 same lumens or whatever, you’d say they’re standard and then it would be relative.
02:13:59 Standard candles is an awesome term, okay.
02:14:01 Standard candles is what astronomers like to say, but I don’t like that term because
02:14:05 there aren’t any standard candles, but there are standardizable candles.
02:14:10 And by looking at these type Ia’s, you look at enough of them in nearby galaxies whose
02:14:17 distances you know independently.
02:14:20 And what you can tell is that, you know, this is something that a colleague of mine, Mark
02:14:25 Phillips did who was on Schmidt’s team and arguably was one of the people who deserved
02:14:30 the Nobel Prize.
02:14:31 He showed that the intrinsically more powerful Type Ia’s decline in brightness, and it turns
02:14:39 out rise in brightness as well, more slowly than the less luminous Ia’s.
02:14:45 And so if you calibrate this by measuring a whole bunch of nearby ones and then you
02:14:50 look at a distant one, instead of saying, well, it’s a 100 watt Type Ia supernova, they’re
02:14:56 much more powerful than that by the way, plus or minus 50, you can say, no, it’s a hundred
02:15:01 and 12 plus or minus 15, or it’s 84 plus or minus 17.
02:15:08 It tells you where it is in the power scale and it greatly decreases the uncertainties.
02:15:15 And that’s what makes these things cosmologically useful.
02:15:18 I showed that if you spread the light out into a spectrum, you can tell spectroscopically
02:15:24 that these things are different as well.
02:15:26 And in 1991, I happened to study two of the extreme peculiar ones, the low luminosity
02:15:33 ones and the high luminosity ones, 1991BG and 1991T.
02:15:40 This showed that not all the Ia’s are the same.
02:15:43 And indeed, at the time of 1991, I was a little bit skeptical that we could use Type Ia’s
02:15:50 because of this diversity that I was observing.
02:15:53 But in 1993, Mark Phillips wrote a paper that showed this correlation between the light
02:16:00 curve, the brightness versus time and the peak luminosity.
02:16:03 Which gives you enough information to calibrate.
02:16:05 Then they become calibratable and that was a game changer.
02:16:08 How many Type Ia’s are out there to use for data?
02:16:12 Now there are thousands of them, but at the time, the high Z team had 16 and the supernova
02:16:19 cosmology project had 40.
02:16:22 But the 16 were better measured than the 40.
02:16:25 And so our statistical uncertainties were comparable if you look at the two papers that
02:16:31 were published.
02:16:32 How does that make you feel that there’s these gigantic explosions just sprinkled out there?
02:16:38 Well, I certainly don’t want one to be very nearby and it would have to be within something
02:16:43 like 10 light years to be an existential threat.
02:16:46 So they can happen in our galaxy?
02:16:48 Oh yeah, yeah.
02:16:49 So they would be okay?
02:16:52 In most cases we’d be okay because our galaxy is 100,000 light years across.
02:16:57 And you’d need one of these things to be within about 10 light years to be an existential
02:17:01 threat.
02:17:02 And it gives birth to a bunch of other stars, I guess?
02:17:07 Yeah, it gives birth to expanding gases that are chemically enriched and those expanding
02:17:11 gases mixed with other chemically enriched expanding gases or primordial clouds of hydrogen
02:17:17 and helium.
02:17:18 I mean, this is in a sense the greatest story ever told, right?
02:17:24 I teach this introductory astronomy course at Berkeley and I tell them there’s only five
02:17:29 or six things that I want them to really understand and remember and I’m going to come to their
02:17:34 deathbed and I’m going to ask them about this and if they get it wrong, I will retroactively
02:17:39 fail and their whole career will have been shot.
02:17:42 That’s a student’s worst nightmare.
02:17:43 If they don’t know and observe a total solar eclipse and yet they had the opportunity to
02:17:46 do so, I will retroactively fail them.
02:17:49 But one of them is, where did we come from?
02:17:51 Where did the elements in our DNA come from?
02:17:54 The carbon in our cells, the oxygen that we breathe, the calcium in our bones, the iron
02:17:59 in our red blood cells.
02:18:01 Those elements, the phosphorus in our DNA, they all came from stars, from nuclear reactions
02:18:07 in stars and they were ejected into the cosmos and in some cases, like iron, made during
02:18:15 the explosions and those gases drifted out, mixed with other clouds, made a new star or
02:18:22 a star cluster, some of whose members then evolved and exploded, thus enriching the gases
02:18:30 in the galaxy progressively more with time until finally, four and a half billion years
02:18:35 ago from one of these chemically enriched clouds, our solar system formed with a rocky
02:18:41 earthlike planet and somewhere, somehow, these self replicating, evolving molecules, bacteria
02:18:49 formed and evolved through paramecia and amoebas and slugs and apes and us.
02:18:58 And here we are, sentient beings that can ask these questions about our very origins
02:19:05 and with our intellect and with the machines we make, come to a reasonable understanding
02:19:12 of our origins.
02:19:15 What a beautiful story.
02:19:16 I mean, if that does not put you at least in awe, if not in love with science and its
02:19:24 power of deduction, I don’t know what will, right?
02:19:30 It’s one of the greatest stories, if not the greatest story.
02:19:33 Obviously, that’s personality dependent and all that, it’s a subjective opinion, but it’s
02:19:38 perhaps the greatest story ever told.
02:19:41 I mean, you could link it to the Big Bang and go even farther, right, to make an even
02:19:45 more complete story, but as a subset, that’s even in some ways a greater story than even
02:19:51 the existence of the universe in some ways, because you could just imagine some really
02:19:56 boring universe that never leads to sentient creatures such as ourselves.
02:20:01 And is a supernova usually the introduction to that story?
02:20:06 So are they usually the thing that launches the, is there other engines of creation?
02:20:12 Well, the supernova is the one, I mean, I touch upon the subject earlier in my course,
02:20:18 in fact, right about now in my lectures, because I talk about how our sun right now is fusing
02:20:22 hydrogen to form helium nuclei and later it’ll form carbon and oxygen nuclei, but that’s
02:20:29 where the process will stop for our sun, it’s not massive enough, some stars that are more
02:20:34 massive can go somewhat beyond that.
02:20:37 So that’s the beginning of this idea of the birth of the heavy elements, since they couldn’t
02:20:42 have been born at the time of the Big Bang, conditions of temperature and pressure weren’t
02:20:47 sufficient to make any significant quantities of the heavier elements.
02:20:51 And so that’s the beginning, but then you need some of these stars to explode, right?
02:20:57 Because if those heavy elements remained forever trapped in the cores of stars, then they would
02:21:03 not be available for the production of new stars, planets, and ultimately life.
02:21:08 So indeed the supernova, my main area of interest, plays a leading role in this whole story.
02:21:17 I saw that you got a chance to call Richard Feynman a mentor of yours when you were at
02:21:22 Caltech.
02:21:23 Yeah.
02:21:24 Do you have any fond memories of Feynman, any lessons that stick with you?
02:21:28 Oh yeah, he was quite a character and one of the deepest thinkers of all time probably,
02:21:36 and at least in my life, the physicist who had the single most intuitive understanding
02:21:42 of how nature works of anyone I’ve met.
02:21:48 I learned a number of things from him, he was not my thesis advisor, I worked with Wallace
02:21:53 Sargent at Caltech on what are called active galaxies, big black holes in the centers of
02:21:58 galaxies that are accreting or swallowing material, a little bit like the stuff of this
02:22:03 year’s Nobel Prize in Physics 2020.
02:22:06 But Feynman I had for two courses, one was general theory of relativity at the graduate
02:22:12 level and one was applications of quantum physics to all kinds of interesting things.
02:22:18 And he had this very intuitive way of looking at things that he tried to bring to his students
02:22:28 and he felt that if you can’t explain something in a reasonably simple way to a non scientist
02:22:38 or at least someone who is versed a little bit with science but is not a professional
02:22:43 scientist then you probably don’t understand it very well yourself very thoroughly.
02:22:49 So that in me made a desire to be able to explain science to the general public and
02:22:58 I’ve often found that in explaining things, yeah, there’s a certain part that I didn’t
02:23:02 really understand myself, that’s one reason I like to teach the introductory courses to
02:23:06 the lay public is that I sometimes find that my explanations are lacking in my own mind.
02:23:12 So he did that for me.
02:23:14 Is there a, if I could just pause for a second, you said he had one of the most intuitive
02:23:18 understanding of nature.
02:23:20 What if you could break apart what intuitive means, like is that on the philosophical level?
02:23:26 No, sort of physical.
02:23:28 How do you draw a mental picture or a picture on paper of what’s going on?
02:23:33 And he’s perhaps most famous in this regard for his Feynman diagrams, which in what’s
02:23:39 called quantum electrodynamics, a quantum field theory of electricity and magnetism.
02:23:44 What you have are actually an exchange of photons between charged particles and they
02:23:48 might even be virtual photons if the particles are at rest relative to one another.
02:23:55 And there are ways of doing calculations that are brute force that take pages on pages and
02:24:00 pages of calculations.
02:24:02 And Julian Schwinger developed some of the mathematics for that and won the Nobel prize
02:24:06 for it.
02:24:07 But Feynman had these diagrams that he made and he had a set of rules of what to do at
02:24:12 the vertex.
02:24:13 You’d have two particles coming together and then a particle going out and then two particles
02:24:17 coming out again.
02:24:18 And he’d have these rules associated when there were vertices and when there were particles
02:24:22 splitting off from one another and all that.
02:24:24 And it looked a little bit like a bunch of a hodgepodge at first.
02:24:27 But to those who learned the rules and understood them, they saw that you could do these complex
02:24:34 calculations in a much simpler way.
02:24:37 And indeed, in some ways, Freeman Dyson had an even better knack for explaining really
02:24:42 what quantum electrodynamics actually was.
02:24:46 But I didn’t know Freeman Dyson.
02:24:48 I knew Feynman.
02:24:49 Maybe he did have a more intuitive view of the world than Feynman did.
02:24:52 But of the people I knew, Feynman was the most intuitive, most sort of, is there a picture?
02:24:58 Is there a simple way you can understand this?
02:25:01 In the path that a particle follows even, you can get the classical path, at least for
02:25:10 a baseball or something like that, by using quantum physics if you want.
02:25:14 But in a sense, the baseball sniffs out all possible paths.
02:25:19 It goes out to the Andromeda galaxy and then goes to the batter.
02:25:23 But the probability of doing that is very, very small because tiny little paths next
02:25:28 door to any given path cancel out that path.
02:25:32 And the ones that all add together, they’re the ones that are more likely to be followed.
02:25:38 And this actually ties in with Fermat’s principle of least action and there are ideas in optics
02:25:45 that go into this as well and just sort of beautifully brings everything together.
02:25:50 But the particle sniffs out all possible paths.
02:25:54 What a crazy idea.
02:25:55 But if you do the mathematics associated with that, it ends up being actually useful, a
02:26:00 useful way of looking at the world.
02:26:02 So you’re also, I mean, you’re widely acknowledged as, I mean, outside of your science work as
02:26:07 being one of the greatest educators in the world.
02:26:12 And Feynman is famous for being that.
02:26:16 Is there something about being a teacher that you…
02:26:19 Well, it’s very, very rewarding when you have students who are really into it.
02:26:23 You know, going back to Feynman, at Caltech, I was taking these graduate courses and there
02:26:29 were two of us, myself and Jeff Richmond, who’s now a professor of physics at University
02:26:34 of California, Santa Barbara, who asked lots of questions.
02:26:38 And a lot of the Caltech students are nervous about asking questions.
02:26:42 They want to save face.
02:26:43 They seem to think that if they ask a question, their peers might think it’s a stupid question.
02:26:49 Well, I didn’t really care what people thought and Jeff Richmond didn’t either.
02:26:52 We asked all these questions and in fact, in many cases, they were quite good questions
02:26:57 and Feynman said, well, the rest of you should be having questions like this.
02:27:00 And I remember one time in particular when he said to the rest of the class, why is it
02:27:07 always these two?
02:27:09 Aren’t the rest of you curious about what I’m saying?
02:27:12 Do you really understand it all that well?
02:27:14 If so, why aren’t you asking the next most logical question?
02:27:17 No, you guys are too scared to ask these questions that these two are asking.
02:27:23 So he actually invited us to lunch a couple of times where just the three of us sat and
02:27:28 had lunch with one of the greatest thinkers of 20th century physics.
02:27:33 And so, yeah, he rubbed off on me and, you know, you encourage questions as well, encourage
02:27:38 questions, you know, and yeah, you know, definitely, I mean, you know, I encourage questions.
02:27:45 I like it when students ask questions.
02:27:46 I tell them that they shouldn’t feel shy about asking a question.
02:27:51 Probably half the students in the class would have that same question if they even understood
02:27:55 the material enough to ask that question.
02:27:58 Yeah.
02:27:59 Curiosity is the first step of seeing the beauty of something.
02:28:04 So yeah, and the question is the ultimate form of curiosity.
02:28:10 Let me ask, what is the meaning of life?
02:28:14 The meaning of life, you know, from a cosmologist’s perspective or from a human perspective, personal,
02:28:19 you know, life is what you make of it, really, right?
02:28:23 It’s each of us has to have our own meaning and it doesn’t have to be.
02:28:31 Well, I think that in many cases, meaning is to some degree associated with goals.
02:28:36 You set some goals or expectations for yourself, things you want to accomplish, things you
02:28:41 want to do, things you want to experience, and to the degree that you experience those
02:28:47 and do those things, it can give you meaning.
02:28:50 You don’t have to change the world the way Newton or Michelangelo or da Vinci did.
02:28:56 I mean, people often say, you changed the world, but look, come on, there’s seven and
02:29:00 a half, close to eight billion of us now.
02:29:02 Most of us are not going to change the world and does that mean that most of us are leading
02:29:06 meaningful lives?
02:29:07 No, it just has to be something that gives you meaning, that gives you satisfaction,
02:29:15 that gives you a good feeling about what you did.
02:29:17 And often, based on human nature, which can be very good and also very bad, but often
02:29:24 it’s the things that help others that give us meaning and a feeling of satisfaction.
02:29:31 You taught someone to read, you cared for someone who was terminally ill, you brought
02:29:37 up a nice family, you brought up your kids, you did a good job, you put your heart and
02:29:43 soul into it, you read a lot of books if that’s what you wanted to do, had a lot of perspectives
02:29:49 on life, you traveled the world if that’s what you wanted to do.
02:29:54 But if some of these things are not within reach, you’re in a socioeconomic position
02:30:00 where you can’t travel the world or whatever, you find other forms of meaning.
02:30:06 It doesn’t have to be some profound, I’m going to change the world, I’m going to be
02:30:13 the one who everyone remembers type thing, right?
02:30:17 In the context of the greatest story ever told, like the fact that we came from stars
02:30:26 and now we’re two apes asking about the meaning of life, how does that fit together?
02:30:31 How does that make any sense?
02:30:34 It does, it does, and this is sort of what I was referring to, that it’s a beautiful
02:30:39 universe that allows us to come into creation, right?
02:30:46 It’s a way that the universe found of knowing, of understanding itself, because I don’t
02:30:52 think that inanimate rocks and stars and black holes and things have any real capability
02:31:00 of abstract thoughts and of learning about the rest of the universe or even their origins.
02:31:08 I mean, they’re just a pile of atoms that has no conscience, has no ability to think,
02:31:16 has no ability to explore, and we do.
02:31:20 And I’m not saying we’re the epitome of all life forever, but at least for life on Earth
02:31:27 so far the evidence suggests that we are the epitome in terms of the richness of our thoughts,
02:31:36 the degree to which we can explore the universe, do experiments, build machines, understand
02:31:42 our origins.
02:31:43 And I just hope that we use science for good, not evil, and that we don’t end up destroying
02:31:50 ourselves.
02:31:51 I mean, the whales and dolphins are plenty intelligent.
02:31:54 They don’t ask abstract questions, they don’t read books, but on the other hand, they’re
02:31:59 not in any danger of destroying themselves and everything else as well.
02:32:03 And so maybe that’s a better form of intelligence, but at least in terms of our ability to explore
02:32:10 and make use of our minds, I mean, to me, it’s this.
02:32:16 It’s this that gives me the potential for meaning, right?
02:32:21 The fact that I can understand and explore.
02:32:24 It’s kind of fascinating to think that the universe created us and eventually we’ve built
02:32:31 telescopes to look back at it, to look back at its origins and to wonder how the heck
02:32:38 the thing works.
02:32:39 It’s magnificent.
02:32:40 It needn’t have been that way, right?
02:32:44 And this is one of the, you know, the multiverse sort of things.
02:32:48 You know, you can alter the laws of physics or even the constants of nature, seemingly
02:32:53 inconsequential things like the mass ratio of the proton and the neutron, you know, wake
02:32:58 me up when it’s over, right?
02:32:59 What could be more boring?
02:33:00 But it turns out you play with things a little bit like the ratio of the mass of the neutron
02:33:04 to the proton and you generally get boring universes, only hydrogen or only helium or
02:33:11 only iron.
02:33:12 You can’t even get the rich periodic table, let alone bacteria, paramecia, slugs and humans,
02:33:19 okay?
02:33:20 I’m not even anthropocentrizing this to the degree that I could.
02:33:25 Even a rich periodic table wouldn’t be possible if certain constants weren’t this way, but
02:33:33 they are.
02:33:34 And that to me leads to the idea of a multiverse that, you know, the dice were thrown many,
02:33:39 many times and there’s this cosmic archipelago where most of the universes are boring and
02:33:44 some might be more interesting.
02:33:45 But we are in the rare breed that’s really quite darn interesting.
02:33:51 And if there were only one and maybe there is only one, well then that’s truly amazing.
02:33:57 We’re lucky.
02:33:58 We’re lucky.
02:33:59 But I actually think there are lots and lots, just like there are lots of planets.
02:34:03 Earth isn’t special for any particular reason.
02:34:05 There are lots of planets in our solar system and especially around other stars.
02:34:09 And occasionally there are going to be ones that are conducive to the development of complexity
02:34:14 culminating in life as we know it.
02:34:17 And that’s a beautiful story.
02:34:18 I don’t think there’s a better way to end it.
02:34:21 Alex, it’s a huge honor.
02:34:23 One of my favorite conversations I’ve had in this podcast.
02:34:25 Well, thank you so much for talking to us.
02:34:27 For the honor of having been asked to do this.
02:34:31 Thanks for listening to this conversation with Alex Filipenko, and thank you to our
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02:35:03 If you enjoy this thing, subscribe on YouTube, review it with 5 Stars and Apple Podcast,
02:35:09 follow on Spotify, support on Patreon, or connect with me on Twitter at Lex Friedman.
02:35:15 And now, let me leave you with some words from Carl Sagan.
02:35:19 The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in
02:35:26 our apple pies, were made in the interiors of collapsing stars.
02:35:32 We are made of star stuff.
02:35:36 Thank you for listening, and hope to see you next time.