The following is a conversation with Alex Filipenko, an astrophysicist and professor of astronomy
from Berkeley. He was a member of both the supernova cosmology project and the high Z supernova
search team, which used observations of the extra galactic supernova to discover that the
universe is accelerating, and that this implies the existence of dark energy. This discovery
resulted in the 2011 NOBA prize for physics. Outside of his groundbreaking research, he is a great
science communicator and is one of the most widely admired educators in the world. I really enjoyed
this conversation and am sure Alex will be back again in the future. Quick mention of each sponsor
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let me say that, as we talk about in this conversation, the objects that populate the universe
are both awe-inspiring and terrifying in their capacity to create and to destroy us.
Solar flares and asteroids lurking in the darkness of space threaten our humble, fragile
existence here on Earth. In the chaos, tension, conflict, and social division of 2020, it's easy
to forget just how lucky we humans are to be here. And with a bit of hard work, maybe one day,
we'll venture out towards the stars. If you enjoy this thing, subscribe on YouTube,
review it with Five Stars on Apple Podcast, follow on Spotify, support on Patreon, or connect with
me on Twitter at Lex Freedman. And now, here's my conversation with Alex Filippenko. Let's start
by talking about the biggest possible thing, the universe. Will the universe expand forever or collapse
on itself? Well, you know, that's a great question. That's one of the big questions of cosmology.
And of course, we have evidence that the matter density is sufficiently low that the universe
will expand forever. But not only that, there's this weird repulsive effect. We call it dark energy
for want of a better term. And it appears to be accelerating the expansion of the universe.
So, if that continues, the universe will expand forever. But it need not necessarily continue.
It could reverse sign, in which case the universe could, in principle, collapse at some point in
the far, far future. So, in terms of investment advice, if you were to give me and then to bet
all my money on one or the other, where does your intuition currently lie? Well, right now,
I would say that it would expand forever, because I think that the dark energy is likely to be
just quantum fluctuations of the vacuum. The vacuum zero energy state is not a state of
zero energy. That is, the ground state is a state of some elevated energy, which has a
repulsive effect to it. And that will never go away, because it's not something that changes
with time. So, if the universe is accelerating now, it will forever continue to do so.
And yet, you're so effortlessly mentioned dark energy. Do we have any understanding of what
the heck that thing is? Well, not really. But we're getting progressively better
observational constraints. So, different theories of what it might be predict different sorts of
behavior for the evolution of the universe. And we've been measuring the evolution of the
universe now. And the data appear to agree with the predictions of a constant density
vacuum energy, a zero point energy. But one can't prove that that's what it is,
because one would have to show that the measured numbers agree with the predictions to an arbitrary
number of decimal places. And of course, even if you've got 8, 9, 10, 12 decimal places,
what if in the 13th one, the measurements significantly differ from the prediction?
Then the dark energy isn't this vacuum state, ground state energy of the vacuum. And so then it
could be some sort of a field, some sort of a new energy, a little bit like light, like electromagnetism,
but very different from light, that fills space. And that type of energy could in principle
change in the distant future. It could become gravitationally attractive for all we know.
There is a historical precedent to that, and that is that the inflation with which the universe
began when the universe was just a tiny blink of an eye old, a trillionth of a trillionth of a
trillionth of a second, the universe went whoosh, it exponentially expanded. That dark energy-like
substance, we call it the inflaton, that which inflated the universe, later decayed into more
or less normal, gravitationally attractive matter. So the exponential early expansion of the universe
did transition to a deceleration, which then dominated the universe for about nine billion years.
And now this small amount of dark energy started causing an acceleration about
five billion years ago. And whether that will continue or not is something that we'd like to
answer, but I don't know that we will anytime soon. So there could be this interesting field
that we don't yet understand that's morphing over time, that's changing the way the universe is
expanding. I mean, it's funny that you were thinking through this rigorously, like an
experimentalist. But what about the fundamental physics of dark energy? Is there any understanding
of what the heck it is? Or is this the kind of the God of the gaps or the field of the gaps?
There must be something there because of what we're observing.
I'm very much a person who believes that there's always a cause. There are no
miracles of a supernatural nature. So I mean, there are two broad categories. Either it's
the vacuum zero point energy, or it's some sort of a new energy field that pervades the universe.
The latter could change with time. The former, the vacuum energy cannot. So
if it turns out that it's one of these new fields, and there are many, many possibilities,
they go by the name of quintessence and things like that. But there are many categories of
those sorts of fields. We try with data to rule them out by comparing the actual measurements
with the predictions. And some have been ruled out, but many, many others remain to be tested.
And the data just have to become a lot better before we can rule out most of them and become
reasonably convinced that this is a vacuum energy.
So there is hypotheses for different fields with names and stuff like that?
Yeah, you know, generically quintessence like the Aristotelian Fifth Essence,
but there are many, many versions of quintessence. There's Kessence. There's even ideas that,
this isn't something from within this dark energy, but rather there are a bunch of, say,
bubble universes surrounding our universe. And this whole idea of the multiverse is not some crazy
madmen-type idea anymore. It's real card-carrying physicists are seriously considering this
possibility of a multiverse. And some types of multiverses could have a bunch of bubbles on the
outside, which gravitationally act outward on our bubble because gravity or gravitons,
the quantum particle that is thought to carry gravity, is thought to traverse the bulk,
the space between these different little bubble membranes and stuff. And so it's conceivable
that these other universes are pulling outward on us. That's not a favored explanation right now,
but really nothing has been ruled out. No class of models has been ruled out completely. Certain
examples within classes of models have been ruled out. But in general, I think we still have
really a lot to learn about what's causing this observed acceleration of the expansion of the
universe, be it dark energy or some forces from the outside. Or perhaps, I guess it's conceivable
that, and sometimes I wake up in the middle of the night screaming, dark energy, which causes
the acceleration and dark matter, which causes galaxies and clusters of galaxies to be bound
gravitationally, even though there's not enough visible matter to do so. Maybe these are our 20th
and 21st century Ptolemaic epicycles. Ptolemy had a geocentric and Aristotelian view of the world.
Everything goes around Earth. But in order to explain the backward motion of planets among
the stars that happens every year or two, or sometimes several times a year for Mercury and
Venus, you needed the planets to go around in little circles called epicycles, which themselves
then went around Earth. And in this part of the epicycle where the planet is going in the direction
opposite to the direction of the overall epicycle, it can appear in projection to be going backward
among the stars, so-called retrograde motion. And it was a brilliant mathematical scheme. In fact,
he could have added epicycles on top of epicycles and reproduced the observed positions of planets
to arbitrary accuracy. And this is really the beginning of what we now call Fourier analysis.
Any periodic function can be represented by a sum of sines and cosines of different periods,
amplitudes, and phases. So it could have worked arbitrarily well. But other data show that,
in fact, Earth is going around the sun. So our dark energy and dark matter, just these
band-aids that we now have to try to explain the data, but they're just completely wrong.
That's a possibility as well. And as a scientist, I have to be open to that possibility as an open
minded scientist. How do you put yourself in the mindset of somebody that, or a majority of the
scientific community, or a majority of people believe that the Earth, everything rotates around
Earth? How do you put yourself in that mindset and then take a leap to propose a model that the sun
is, in fact, at the center of the solar system? Sure. I mean, so that puts us back in the shoes
of Copernicus 500 years ago, where he had this philosophical preference for the sun being the
dominant body in what we now call the solar system. The observational evidence in terms of the measured
positions of planets was not better explained by the heliocentric sun-centered system. Copernicus
saw that the sun is the source of all our light and heat. He knew from other studies that it's
far away, so the fact that it appears as big as the moon means it's actually way, way bigger,
because even at that time, it was known that the sun is much farther away than the moon.
He just felt, wow, it's big, it's bright. What if it's the central thing? But the
observed positions of planets at the time in the early to mid-16th century under the heliocentric
system was not a better match, at least not a significantly better match than Ptolemy's system,
which was quite accurate and lasted 1,500 years. That's so fascinating to think that
the philosophical predispositions that you bring to the table are essential. You have to have a
young person come along that has a weird infatuation with the sun. That almost philosophically is,
however they're upbringing me, they're more ready for whatever the simpler answer is.
It's kind of sad. It's sad from an individual descendant of a perspective, because then that
means me, you as a scientist, you're stuck with whatever the heck philosophies you brought to
the table. You might be almost completely unable to think outside this particular box you've built.
Right. This is why I'm saying that as an objective scientist, one needs to have an open mind to
crazy sounding new ideas. Even Copernicus was very much a man of his time and dedicated his
work to the pope. He still used circular orbits. The sun was a little bit off-center, it turns out,
and a slightly off-center circle looks like a slightly eccentric elliptical orbit. Then when
Kepler, in fact, showed that the orbits are actually in general ellipses, not circles,
the reason that he needed to co-brah his really great data to show that distinction
was that a slightly off-center circle is not much different from a slightly eccentric ellipse.
So there wasn't much difference between Kepler's view and Copernicus's view, and Kepler needed
the better data to co-brah's data. Again, a great example of science and observations and
experiments working together with hypotheses, and they kind of bounce off each other. They play
off of each other, and you continually need more observations. And it wasn't until Galileo's work
around 1610 that actual evidence for the heliocentric hypothesis emerged. It came in the
form of Venus, the planet Venus, going through all of the possible phases from new to crescent,
to quarter, to gibbous, to full, to waning gibbous, third quarter waning crescent, and then new again.
It turns out in the Ptolemaic system, with Venus between Earth and the Sun, but always roughly
in the direction of the Sun, you could only get the new and crescent phases of Venus. But the
observations showed a full set of phases, and moreover, when Venus was gibbous or full, that
meant it was on the far side of the Sun, that meant it was farther from Earth than when it's
crescent, so it should appear smaller, and indeed it did. So that was the nail in the coffin, in
a sense. And then Galileo's other great observation was that Jupiter has moons going around it,
the four Galilean satellites. And even though Jupiter moves through space, so too do the moons go
with it. So first of all, Earth is not the only thing that has other things going around it.
And secondly, Earth could be moving, as Jupiter does, and things would move with it. We wouldn't
fly off the surface, and our moon wouldn't be left behind, and all this kind of stuff. So
that was a big breakthrough as well, but it wasn't as definitive, in my opinion, as the
phases of Venus. Perhaps I'm revealing my ignorance, but I didn't realize how much data
they were working with. So it wasn't Einstein or Freud thinking in theories. It was a lot of data,
and you're playing with it and seeing how to make sense of it. So it isn't just coming up with
completely abstract thought experiments. It's looking at the data of astronomy.
Sure, and you look at Newton's great work, right? The Principia, it was based in part on Galileo's
observations of balls rolling down inclined planes, supposedly falling off the Leaning
Tower of Pisa, but that's probably apocryphal. In any case, the Inquisition actually did,
or the Roman Catholic Church, did history a favor, not that I'm condoning them, but they placed
Galileo under house arrest, and that gave Galileo time to publish, to assemble and publish
the results of his experiments that he had done decades earlier. It's not clear he would have
had time to do that, had he not been under house arrest. And so Newton, of course, very much used
Galileo's observations. Let me ask the old Russian overly philosophical question about death.
So we're talking about the expanding universe. Sure. How do you think human civilization will
come to an end if we avoid the near term issues we're having? Will it be our sun burning out?
Will it be comets? Okay. Will it be, what is it? Do you think we have a shot at reaching the
heat death of the universe? Yeah. So we're going to leave out the anthropogenic
causes of our potential destruction, which I actually think are greater than the celestial
causes. So if we get lucky and intelligent, I don't know.
Yeah. So no way will we as humans reach the heat death of the universe. I mean, it's conceivable
that machines, which I think will be our evolutionary descendants might reach that,
although even they will have less and less energy with which to work as time progresses because
eventually even the lowest mass stars burn out, although it takes them trillions of years to do
so. So the point is, is that certainly on Earth, there are other celestial threats, existential
threats, comets, exploding stars, the sun burning out. So we will definitely need to move away
from our solar system to other solar systems. And then the question is, can they keep on
propagating to other planetary systems sufficiently long? In our own solar system,
the sun burning out is not the immediate existential threat. That'll happen in about
five billion years when it becomes a red giant. Although I should hasten to add that within the
next one or two billion years, the sun will have brightened enough that unless their
compensatory atmospheric changes, the oceans will evaporate away. And you need much less
carbon dioxide for the temperatures to be maintained roughly at their present temperature,
and plants wouldn't like that very much. So you can't lower the carbon dioxide content too much.
So within one or two billion years, probably the oceans will evaporate away.
Yeah. But on a sooner time scale than that, I would say an asteroid collision leading to a
potential mass extinction, or at least an extinction of complex beings such as ourselves,
that require quite special conditions, unlike cockroaches and amoebas to survive.
One of these civilization-changing asteroids is only one kilometer or so in diameter and bigger.
And a true mass extinction event is 10 kilometers or larger. Now, it's true that we can find and
track the orbits of asteroids that might be headed toward Earth. And if we find them 50 or 100
years before they impact us, then clever applied physicists and engineers can figure out ways to
deflect them. But at some point, some comet will come in from the deep freeze of the solar system.
And there, we have very little warning months to a year. What's the deep freeze?
Oh, the deep freeze is sort of out beyond Neptune. There's this thing called the Kuiper Belt.
And it consists of a bunch of dirty ice balls or icy dirt balls. It's the source of the comets
that occasionally come close to the sun. And then there's an even bigger area called the
scattered disk, which is sort of a big donut surrounding the solar system way out there
from which other comets come. And then there's the Oort cloud, W-O-R-T after Jan Oort, a Dutch
astrophysicist. And it's the better part of a light year away from the sun, so a good fraction
of the distance to the nearest star. But that's like a trillion or 10 trillion
comet-like objects that occasionally get disturbed by a passing star or whatever, and most of them
go flying out of the solar system, but some go toward the sun, and they come in with little
warning. By the time we can see them, they're only a year or two away from us. And moreover,
not only is it hard to determine their trajectories sufficiently accurately to know whether they'll
hit a tiny thing like Earth, but outgassing from the comet of gases when the ices sublimate,
that outgassing can change the trajectory just because of conservation of momentum, right?
It's the rocket effect. Gases go out in one direction, the object moves in the other direction.
And so since we can't predict how much outgassing there will be and in exactly what direction,
because these things are tumbling and rotating and stuff, it's hard to predict the trajectory
with sufficient accuracy to know that it will hit. And you certainly don't want to deflect a comet
that would have missed, but you thought it was going to hit and end up having it hit.
That would be like the ultimate Charlie Brown goat instead of trying to be the hero, right?
He ended up being the goat. What would you do if it seemed like in a matter of months
that there is some non-zero probability, maybe a high probability that there would be a collision
sort of from a scientific perspective, from an engineering perspective, I imagine you would
actually be in the room of people deciding what to do, philosophically too.
It's a tough one, right? Because if you only have a few months, that's not much time in which to
deflect it. Early detection and early action are key, because when it's far away, you only
have to deflect it by a tiny little angle. And then by a time it reaches us, the perpendicular
motion is big enough to miss Earth. All you need is one radius or one diameter of the Earth, right?
That actually means that all you would need to do is slow it down so it arrives four minutes
later or speed it up so it arrives four minutes earlier and Earth will have moved through one
radius in that time. So it doesn't take much. But you can imagine if a thing is about to hit you,
you have to deflect at 90 degrees or more, right? And you don't have much time to do so,
and you have to slow it down or speed it up a lot if that's what you're trying to do to it.
And so decades is sufficient time, but months is not sufficient time. So at that point, I would think
the name of the game would be to try to predict where it would hit.
And if it's in a heavily populated region, try to start an orderly evacuation,
perhaps. But that might cause just so much panic that I mean, how would you do it with New York
City or Los Angeles or something like that, right? I might have a different opinion a year ago. I'm
a bit disheartened by, in the movies, there's always extreme competence from the government.
Competence, yeah. Competence, yeah. Right. But we expect extreme incompetence,
if anything, right? Yes, no. So I'm quite disappointed. But from a medical perspective,
I think you're saying that in a scientific one, it's almost better to get better and better,
maybe telescopes and data collection to be able to predict the movement of these things or come up
with totally new technologies. You can imagine actually sending out probes out there to be able to
sort of almost have little finger sensors throughout our solar system to be able to detect stuff.
Well, that's right. Yeah, monitoring the asteroid belt is very important. 99% of the so-called
near-Earth objects ultimately come from the asteroid belt. And so there we can track the
trajectories. And even if there's a close encounter between two asteroids, which deflects one of them
toward Earth, it's unlikely to be on a collision course with Earth in the immediate future. It's
more like tens of years. So that gives us time. But we would need to improve our ability to detect
the objects that come in from a great distance. Unfortunately, those are much rarer. The comets
come in, 1% of the collisions perhaps are with comets that come in without any warning hardly.
And so that might be more like a billion or two billion years before one of those hits us.
So maybe we have to worry about the sun getting brighter on that time scale. I mean,
there's the possibility that a star will explode near us in the next couple of billion years. But
over the course of the history of life on Earth, the estimates are that maybe only one of the mass
was caused by a star blowing up, in particular, a special kind called a gamma ray burst. And
I think it's the Ordovician-Solarian extinction 420 or so, 440 million years ago,
that is speculated to have come from one of these particular types of exploding stars called gamma
ray bursts. But even there, the evidence is circumstantial. So those kinds of existential
threats are reasonably rare. The greater danger, I think, is civilization changing events where
it's a much smaller asteroid, which those are harder to detect, or a giant solar flare that
shorts out the grid in all of North America, let's say. Now, astronomers are monitoring the
sun 24-7 with various satellites. And we can tell when there's a flare or a coronal mass ejection.
And we can tell that in a day or two, a giant bundle of energetic particles will arrive and
twang the magnetic field of Earth and send all kinds of currents through long-distance power lines.
And that's what shorts out the transformers. And transformers are expensive and hard to replace
and hard to transport and all that kind of stuff. So if we can warn the power companies and they can
shut down the grid before the big bundle of particle hits, then we will have mitigated much
of this. Now, for a big enough bundle of particles, you can get short circuits even over small
distance scales. So not everything will be saved, but at least the whole grid might not go out.
So again, astronomers, I like to say, support your local astronomer, they may help someday
save humanity by telling the power companies to shut down the grid, finding the asteroid 50
or 100 years before it hits, then having clever physicists and engineers deflect it. So many
of these cosmic threats, cosmic existential threats, we can actually predict and do something
about or observe before they hit and do something about. It's terrifying to think that people would
listen to this conversation. It's like when you listen to Bill Gates talk about pandemics and
his TED talk a few years ago and realizing we should have supported our local astronomer more.
Well, I don't know whether it's more because, as I said, I actually think human-induced threats
or things that occur naturally on Earth, either a natural pandemic or perhaps a
bioengineering-type pandemic or something like a supervolcano. There was one event, Tobai,
I think it was 70 plus thousand years ago, that caused a gigantic decrease in temperatures on
Earth because it sent up so much soot that it blocked the sun. It's the nuclear winter-type
disaster scenario that some people, including Carl Sagan, talked about decades ago. But we can see
in the history of volcanic eruptions, even more recently in the 19th century, Tambora and other
ones, you look at the record and you see rather large dips in temperature associated with massive
volcanic eruptions. Well, these supervolcanoes, one of which, by the way, exists under Yellowstone
in the central U.S. It's not just one or two states. It's a gigantic region and there's
controversy as to whether it's likely to blow anytime in the next 100,000 years or so. But
that would be perhaps not a mass extinction because you really need to, or perhaps not a
complete existential threat because you have to get rid of the very last humans for that,
but at least getting rid of killing off so many humans, truly billions and billions of humans.
There have been ones tens of thousands of years ago, including this one Tobai, I think it's called,
where it's estimated that the human population was down to 10,000 or 5,000 individuals,
something like that. If you have a 15-degree drop in temperature over quite a short time,
it's not clear that even with today's advanced technology, we would be able to adequately respond,
at least for the vast majority of people. Maybe some would be in these underground caves where
you'd keep the president and a bunch of other important people, but the typical person is not
going to be protected when all of agriculture is cut off. It could be hundreds of millions or billions
of people starving to death. Exactly. That's right. They don't all die immediately, but they
use up their supplies or, again, this electrical grid. First of toilet paper. There you go,
dash that toilet paper. Or the electrical grid. Imagine North America without power for a year.
We've become so dependent. We're no longer the cave people. They would do just fine. What do
they care about the electrical grid? What do they care about agriculture? They're hunters and
gatherers, but we now have become so used to our way of life that the only real survivors would be
those rugged individualists who live somewhere out in the forest or in a cave somewhere completely
independent of anyone else. Yeah. Recently, I recommend it. It's totally new to me, this kind
of survivalist folks, but there's a lot of shows of those. I saw one on Netflix,
and I started watching them, and they make a lot of sense. They reveal to you how
dependent we are on all aspects of this beautiful system we human have built and how fragile they
are. Incredibly fragile. Yeah. This whole conversation is making me realize how lucky we are.
Oh, we're incredibly lucky, but we've set ourselves up to be very, very fragile. And
we are intrinsically complex biological creatures that, except for the fact that we have brains
and minds with which we can try to prevent some of these things or respond to them,
we, as a living organism, require quite a narrow set of conditions in order to survive.
We're not cockroaches. We're not going to survive a nuclear war.
So, we're kind of, this beautiful dance between, we've been talking about astronomy,
that astronomy, the stars, like, inspires everybody. And at the same time,
there's this pragmatic aspect that we're talking about. And so, I see space exploration as the
same kind of way that it's reaching out to other planets, reaching out to the stars. It's this
really beautiful idea. But if you listen to somebody like Elon Musk, he talks about space
exploration as very pragmatic. Like, we have to, if we, we have to be,
yes, this ridiculous way of sounding like an engineer about it, which is like,
it's obvious we need to become a multi-planetary species if we were to survive long term. So,
maybe both philosophically, in terms of beauty, and in terms of practical, what's your thoughts on
space exploration, on the challenges of it, on how much we should be investing in it. And on a
personal level, like, how excited you are by the possibility of going to Mars, colonizing Mars,
and maybe going outside the solar system. Yeah. You know, great question.
There's a lot to unpack there, of course. You know, humans are by their very nature
explorers, pioneers. They want to go out, climb the next mountain, see what's behind it,
explore the option depths, explore space. This is our destiny to go out there. And,
of course, from a pragmatic perspective, yes, we need to plant our seeds elsewhere,
really, because things could go wrong here on Earth. Now, some people say that's an excuse to
not take care of our planet that, well, we say we're elsewhere, and so we don't have to take
good care of our planet. No, we should take the best possible care of our planet. We should be
cognizant of the potential impact of what we're doing. Nevertheless, it's prudent to have us be
elsewhere as well. So in that regard, I actually agree with Elon. It'd be good to be on Mars. That
would be yet another place for us from which to explore a little further. Would that be a good
next step? Well, it's a good next step. I happen to disagree with him as to how quickly it will
happen, right? I mean, I think he's very optimistic. Now, you need visionary people like Elon to get
people going and to inspire them. I mean, look at the success he's had with multiple companies.
So maybe he gives this very optimistic timeline in order to be inspirational
to those who are going out there. And certainly, his success with the rocket that is reusable,
because it landed upright and all that. I mean, that's a game changer. It's sort of like every
time you flew from San Francisco to Los Angeles, you discard the airplane, right? I mean, that's
crazy, right? So that's a game changer. But nevertheless, the timescale over which he thinks
that there could be a real thriving colony on Mars, I think is far too optimistic.
What's the biggest challenges to you? One is just getting rockets, not rockets, but people out there,
and two is the colonization. Do you have thoughts about this, the challenges of this kind of prospect?
Yeah, I haven't thought about it in great detail other than recognizing that Mars is a
harsh environment. You don't have much of an atmosphere there. You've got less than a percent
of Earth's atmosphere. So you'd need to build some sort of a dome right away, right? And that
would take time. You need to melt the water that's in the permafrost or have canals dug from which
you transport it from the polar ice caps. I was reading recently in terms of what's the most
efficient source of nutrition for humans that were to live on Mars, and people should look
into this, but it turns out to be insects. Insects, yeah. So you want to build giant colonies of
insects and just be eating them. Insects have a lot of protein, right? Yeah, a lot of protein,
and they're easy to grow. You can think of them as farming. Right. But it's not going to be as easy
as growing a whole plot of potatoes like in the movie The Martian or something, right? It's not
going to be that easy. So there's this thin atmosphere. It's got the wrong composition.
It's mostly carbon dioxide. There are these violent dust storms. The temperatures are generally cold.
You'd need to do a lot of things. You need to terraform it basically in order to make it
nicely livable without some dome surrounding you. And if you insist on a dome, well, that's
not going to house that many people, right? So let's look briefly then. We're looking for a
new apartment to move into. So let's look outside the solar system. Do you think you've spoken about
exoplanets as well? Do you think there's possible homes out there for us outside of our solar system?
There are lots and lots of homes, possible homes. I mean, there's a planetary system around nearly
every star you see in the sky. And one in five of those is thought to have a roughly Earth-like
planet. And that's a relatively new discovery. I mean, that's the Kepler satellite, which was
flying around above Earth's atmosphere, was able to monitor the brightness of stars with exquisite
detail. And they could detect planets crossing the line of sight between us and the star, thereby
dimming its light for a short time, ever so slightly. And it's amazing. So there are now
thousands and thousands of these exoplanet candidates of which something like 90% are
probably genuine exoplanets. And you have to remember that only about 1% of stars have their
planetary system oriented adjunct to your line of sight, which is what you need for this transit
method to work, right? Some arbitrary angle won't work and certainly perpendicular to your line of
sight. That is, in the plane of the sky won't work because the planet is orbiting the star and
never crossing your line of sight. So the fact that, you know, they found planets orbiting about
1% of the stars that they looked at in this field of 150 plus thousand stars,
they found planets around 1%. You then multiply by the inverse of 1%, which is, you know, right?
1% is about how many what the fraction of the of the stars that have their planetary system
oriented the right way. And that already back of the envelope calculation tells you that
of order, 50 to 100% of all stars have planets, okay? And then they've been finding these
Earth-like planets, et cetera, et cetera. So there are many potential homes. The problem is
getting there, okay? So then a typical bright star, Sirius, the brightest star in the sky,
maybe not a typical bright star, but it's 8.7 light years away, okay? So that's,
that means the light took 8.7 years to reach us. We're seeing it as it was about nine years ago,
okay? So then, you know, you ask how long would a rocket take to get there at Earth's escape speed,
which is 11 kilometers per second, okay? And it turns out it's about a quarter of a million years,
okay? Now, that's 10,000 generations, okay? Let's say a generation of humans is 25 years,
right? So you'd need this colony of people that is able to sustain itself, all their food,
all their waste disposal, all their water, all their recycling of everything. For 10,000 generations,
they have to commit themselves to living on this vehicle, right? I just don't see it happening.
What I see potentially happening, if we avoid self-destruction intentional or unintentional
here on Earth, is that machines will do it, robots, that can essentially hibernate. They don't need
to do much of anything for a long, long time as they're traveling. And moreover, if some energetic
charged particles, some cosmic ray hits the circuitry, it fixes itself, right? Machines can do this.
I mean, it's a form of artificial intelligence. You just tell the thing, fix yourself, basically. And
then when you land on the planet, start producing copies of yourself. Initially, for materials
that were perhaps sent, or you just have a bunch of copies there, and then they set up
factories with which to do this. I mean, this is very, very futuristic. But
it's much more feasible, I think, than sending flesh and blood over interstellar distances,
a quarter of a million years to even the nearest stars. You're subject to all kinds of charged
particles and radiation. You have to shield yourself really well. That's, by the way,
one of the problems of going to Mars is that it's not a three-day journey like going to the moon.
You're out there for the better part of a year or two, and you're exposed to lots of radiation,
which typically doesn't do well with living tissue, right? Or living tissue doesn't do well
with the radiation. And the hope is that the robots, the AI systems might be able to carry the
fire of consciousness, whatever makes us humans like a little drop of whatever makes us humans
so special, not to be too poetic about it. No, but I like being poetic about it,
because it's an amazing question. Is there something beyond just the bits, the ones and
zeros to us? It's an interesting question. I like to think that there isn't anything,
and that how beautiful it is that our thoughts, our emotions, our feelings, our compassion
all come from these ones and zeros, right? That, to me, actually is a beautiful thought,
and the idea that machines, silicon-based life, effectively, could be our natural evolutionary
descendants, not from a DNA perspective, but they are our creations, and they then carry on.
That, to me, is a beautiful thought in some ways, but others find it to be a horrific
thought. So that's exciting to you. It is exciting to me as well, because to me, from a purely an
engineering perspective, I believe it's impossible to create whatever systems we create that take
over the world. It's impossible for me to imagine that those systems will not carry some aspect
of what makes humans beautiful. So a lot of people have these kind of paperclip ideas that
that will build machines that are cold inside, or philosophers call them zombies, that naturally
the systems that will out-compete us on this earth will be cold and non-conscious,
not capable of all the human emotions and empathy and compassion and love and hate
ever. The beautiful mix of what makes us human. But to me, intelligence requires all of that.
So in order to out-compete humans, you better be good at the full picture.
Right. So artificial general intelligence, in my view, encompasses a lot of these attributes
that you just talked about, like curiosity, inquisitiveness. It might look very different
than us humans, but it will have some of the magic. But it'll also be much more able to survive the
onslaught of existential threats that either we bring upon ourselves or don't anticipate here on earth,
or that occasionally come from beyond. And there's nothing much we can do about a supernova
explosion that just suddenly goes off. And really, if we want to move to other planets outside our
solar system, I think realistically, that's a much better option than thinking that humans will
actually make these gigantic journeys. And then I do this calculation for my class. Einstein's
special theory of relativity says that you can do it in a short amount of time in your own frame of
reference if you go close to the speed of light. But then you bring in E equals mc squared, and
you figure out how much energy it takes to get you accelerated to close enough to the speed of light
to make the time scales short in your own frame of reference. And the amount of energy is just
unfathomable. We can do it at the Large Hadron Collider with protons. We can accelerate them
to 99.999% of the speed of light, but that's just a proton. We're gazillions of protons.
Okay? And that doesn't even count the rocket that would carry us, the payload. And you would need
to either store the fuel in the rocket, which then requires even more mass for the rocket,
or collect fuel along the way, which is difficult. And so getting close to the speed of light, I
think, is not an option either, other than for a little tiny thing, like Yuri Milner and others
are thinking about this Starshot project where they'll send a little tiny camera to Alpha Centauri
4.2 light years away. They'll zip past it, take a picture of the exoplanets that we know orbit
that three or more star system, and say hello real quickly and then send the images back to us.
Okay? So that's a tiny little thing, right? Maybe you can accelerate that to
their hoping 20% of the speed of light with a whole bunch of high-powered lasers aimed at it.
It's not clear that other countries will allow us to do that, by the way. But that's a very
forward-looking thought. I mean, I very much support the idea. But there's a big difference
between sending a little tiny camera and sending a payload of people with equipment that could then
mine the resources on the exoplanet that they reach and then go forth and multiply, right?
Well, let's talk about the big galactic things and how we might be able to leverage them to
travel fast. I know this is a little bit science fiction, but ideas of wormholes and
ideas at the edge of black holes that reveal to us that this fabric of space-time
could be messed with. Yeah. Perhaps. Is that at all an interesting thing for you? I mean,
in looking out at the universe and studying it as you have, is that also a possible,
like a dream for you that we might be able to find clues how we can actually use it
to improve our transportation? It's an interesting thought. I'm certainly excited by
the potential physics that suggests this kind of faster-than-light travel effectively or cutting
the distance to make it very, very short through a wormhole or something like that.
Possible? No. Well, call me not very imaginative,
but based on today's knowledge of physics, which I realize, people have gone down that rabbit hole
and a century ago, Lord Kelvin, one of the greatest physicists of all time, said that
all of fundamental physics is done. The rest is just engineering. And guess what? Then came special
relativity, quantum physics, general relativity, how wrong he was. So let me not be another Lord
Kelvin. On the other hand, I think we know a lot more now about what we know and what we don't know
and what the physical limitations are. And to me, most of these schemes, if not all of them,
seem very far-fetched, if not impossible. So travel through wormholes, for example.
It appears that for a non-rotating black hole, that's just a complete no-go because the singularity
is a point-like singularity, and you have to reach it to traverse the wormhole and you get
squished by the singularity. Now, for a rotating black hole, it turns out there is a way to pass
through the event horizon, the boundary of the black hole, and avoid the singularity and go out
the other side, or even traverse the donut hole-like singularity. In the case of a rotating
black hole, it's a ring singularity. So there's actually two theoretical ways you could get through
a rotating black hole or a charged black hole, not that we expect charged black holes to exist
in nature because they would quickly bring in the opposite charge so as to neutralize themselves.
But rotating black holes, definitely a reality. We now have good evidence for them.
And do they have traversable wormholes? Probably not, because it's still the case that
when you go in, you go in with so much energy that it either squeezes the wormhole shut,
or you encounter a whole bunch of incoming and outgoing energy that vaporizes you. It's called
the mass inflation instability, and it just vaporizes you. Nevertheless, you could imagine,
well, you're in some vapor form, but if you make it through, maybe you could
reform or something. So it's still information. Yeah, it's still information. It's scrambled
information, but there's a way maybe of bringing it back. But then the thing that really bothers me
is that as soon as you have this possibility of traversal of a wormhole, you have to come to
grips with a fundamental problem. And that is that you could come back to your universe at a time
prior to your leaving, and you could essentially prevent your grandparents from ever meeting.
This is called the grandfather paradox. And if they never met, and if your parents were never
born, and if you were never born, how would you have made the journey to prevent the history
from allowing you to exist? It's a violation of causality, of cause and effect. Now,
physicists such as myself take causality violation very, very seriously. We've never seen it.
You took a stand. Yeah, I mean, you know, I mean, it's one of these right back to the future type
movies, right? And you have to work things out in such a way that you don't mess things up, right?
Some people say that, well, you come back to the universe, but you come back in such a way that you
cannot affect your journey. But then, I mean, that seems kind of contrived to me. Or some say
that you end up in a different universe. And this also goes into the many different types of the
multiverse hypothesis and the many worlds interpretation and all that. But again, then
it's not the universe from which you left, right? And you don't come back to the universe from which
you left. And so you're not really going back in time to the same universe. And you're not even
going forward in time necessarily then to the same universe, right? You're ending up in some other
universe. So what have you achieved, right? You've traveled. You've traveled. You ended up in a
different place than you started in more ways than one. Yeah. And then there's this idea,
the Alcubierre Drive, where you warp space-time in front of you so as to greatly reduce the
distance and you can expand the space-time behind you. So you're sort of riding a wave through
space-time. But the problem I see with that beyond the practical difficulties and the energy
requirements. And by the way, how do you get out of this bubble through which you're, you know,
riding this wave of space-time? And Miguel Alcubierre acknowledged all these things. He said,
this is purely theoretical, fanciful, and all that. But a fundamental problem I see is that
you'd have to get to those places in front of you so as to change the shape of space-time so as to
make the journey quickly. But to get there, you got there in the normal way at a speed considerably
less than that of light. So in a sense, you haven't saved any time, right? You might as well have
just taken that journey and gotten to where you were going. What have you done? It's not like
you snap your fingers and say, okay, let that space there be compressed, and then I'll make it over
to Alpha Centauri in the next month. You can't snap your fingers and do that. Yeah. And we're
sort of assuming that we can fix all the biological stuff that requires for humans to persist through
that whole process. Because ultimately, it might boil down to just extending the life of the human
in some form, whether it's through the robot, through the digital form, or actually just
figuring out genetically how to live forever. That's right. Because that journey that you mentioned,
the long journey, might be different if somehow our understanding of genetics,
of our understanding of our own biology, all that kind of stuff, that's another trajectory
that we could possibly do. Right. If you could put us into some sort of suspended animation,
you know, hibernation or something, and greatly increase the lifetime. And so these 10,000
generations I talked about, what do they care? It's just one generation, and they're asleep,
okay? Just a long nap. So then you can do it. It's still not easy, right? Because you've got some
big old huge colony, and that just through E equals MC squared, right? That's a lot of mass.
That's a lot of stuff to accelerate. The Newtonian kinetic energy is gigantic, right? So you're still
not home free, but at least you're not trying to do it in a short amount of clock time, right?
Which if you look at E equals MC squared, requires truly unfathomable amounts of energy,
because the energy is sort of, it's your rest mass, M not C squared divided by the square root of 1
minus V squared over C squared. And if your listeners want to just sort of stick into their
pocket calculator, as V over C approaches 1, that 1 over the square root of 1 minus V squared
over C squared approaches infinity. So if you wanted to do it in zero time, you'd need an
infinite amount of energy. That's basically why you can't reach, let alone exceed the speed of light
for a particle moving through a preexisting space. It's that it takes an infinite amount of energy
to do so. So that's talking about us going somewhere. What about one of the things that
inspires a lot of folks, including myself, is the possibility that there's other,
that this conversation is happening on another planet in different forms with intelligent life
forms? Well, first we could start, as a cosmologist, what's your intuition about whether there is or
isn't intelligent life out there outside of our own? Yeah, I would say I'm one of the pessimists
in that I don't necessarily think that we're the only ones in the observable universe, which goes
out roughly 14 billion years in light travel time and more like 46 billion years when you take
into account the expansion of space. So the diameter of our observable universe is something
like 90, 92 billion light years. That encompasses 100 billion to a trillion galaxies with 100
billion stars each. So now you're talking about something like 10 to the 22nd, 10 to the 23rd
power stars and roughly an equal number of Earth-like planets and so on. So there may well be
other intelligent life. But your sense is our galaxy is not teeming with life. Yeah, our galaxy,
our Milky Way galaxy with several hundred billion stars and potentially habitable planets is not
teeming with intelligent life. Intelligent. Yeah, well, I'll get to the primitive life,
the bacteria in a moment. But we may well be the only ones in our Milky Way galaxy,
at most a handful, I'd say, but I'd probably side with the school of thought that suggests
we're the only ones in our own galaxy just because I don't see human intelligence as being
a natural evolutionary path for life. I mean, there's a number of arguments. First of all,
there's been more than 10 billion species of life on Earth in its history. Nothing has approached
our level of intelligence and mechanical ability and curiosity. Whales and dolphins appear to be
reasonably intelligent, but there's no evidence that they can think abstract thoughts that they're
curious about the world. They certainly can't build machines with which to study the world. So
that's one argument. Secondly, we came about as early hominids only four or five million years ago
and as homo sapiens only about a quarter of a million years ago. So for the vast majority of
the history of life on Earth, an intelligent alien zipping by Earth would have said there's
nothing particularly intelligent or mechanically able on Earth. Thirdly, it's not clear that our
intelligence is a long-term evolutionary advantage. Now, it's clear that in the last 100 years, 200
years, we've improved the lives of millions, hundreds of millions of people, but at the risk of
potentially destroying ourselves either intentionally or unintentionally or through neglect,
as we discussed before. That's a really interesting point, which is it's possible that their
huge amount of intelligent civilizations have been born even through our galaxy,
but they live very briefly and they die. They're flashbulbs in the night.
That brings me to the fourth issue and that is the Fermi Paradox. If they're common,
then where the hell are they? Notwithstanding the various UFO reports in Roswell and all that,
they just don't meet the bar. They don't clear the bar of scientific evidence in my opinion.
So there's no clear evidence that they've ever visited us on Earth here.
SETI has been now the search for extraterrestrial intelligence has been scanning the skies. And
true, we've only looked a couple of hundred light years out and that's a tiny fraction of the whole
galaxy, a tiny fraction of these hundred billion plus stars. Nevertheless, if the galaxy were
teaming with life, especially intelligent life, you'd expect some of it to have been far more
advanced than ours. There's no special, nothing special about when the industrial revolution
started on Earth. The chemical evolution of our galaxy was such that billions of years ago,
nuclear processing and stars had built up clouds of gas after their explosion that were rich enough
in heavy elements to have formed Earth-like planets, even billions of years ago. So there could be
civilizations that are billions of years ahead of ours. And if you look at the exponential growth
of technology among Homo sapiens in the last couple of hundred years, and you just project that
forward, I mean, there's no telling what they could have achieved even in 1000 or 10,000 years,
let alone a million or 10 million or a billion years. And if they reach this capability of
interstellar travel and colonization, then you can show that within 10 million years,
or certainly 100 million years, you can populate the whole galaxy. So then you don't have to have
tried to detect them beyond 100 or 1000 light years, they would already be here.
Do you think as a thought experiment, do you think it's possible that they are already here,
but we humans are so human-centric that we're just not like our conception of what intelligent life
looks like? Yeah. We don't want to acknowledge it. Like what if trees? Right, right, right.
Okay, I guess in a form of a question, do you think we'll actually detect intelligent life
if it came to visit us? Yeah, I mean, it's like you're an ant crawling around on a sidewalk
somewhere and do you notice the humans wandering around and the Empire State building and rocket
ships flying to the moon and all that kind of stuff. Right. It's conceivable that we haven't
detected it and that we're so primitive compared to them that we're just not able to do so.
Like if you look at dark energy, maybe we call it as the field. It's just that my own feeling is
that in science now, through observations and experiments, we've measured so many things and
basically we understand a lot of stuff. Fabric of reality. Yeah, the fabric of
reality we understand quite well. And there are a few little things like dark matter and dark energy
that may be some sign of some superintelligence, but I doubt it. Okay, why would some superintelligence
be holding clusters of galaxies together? Why would they be responsible for accelerating the
expansion of the universe? So the point is that through science and applied science and engineering,
we understand so much now that I'm not saying we know everything, but we know a hell of a lot.
Okay. And so it's not like there are lots of mysteries flying around there that are completely
outside our level of exploration or understanding. I would say from the mystery perspective,
it seems like the mystery of our own cognition and consciousness is much grander than the degrees
of freedom of possible explanations of what the heck is going on is much greater there than in
the physics of the absolute way. How the brain works. How did life arise? Yeah. That's big,
big questions. But they to me don't indicate the existence of an alien or something. I mean,
unless we are the aliens, we could have been contamination from some rocket ship that hit
here a long, long time ago and all evidence of it has been destroyed. But again, that alien would
have started out somewhere. They're not here watching us right now, right? They're not among us.
And so though there are potential explanations for the Fermi paradox and one of them that I kind
of like is that the truly intelligent creatures are those that decided not to colonize the whole
galaxy because they'd quickly run out of room there because it's exponential, right? You send a probe
to a planet, it makes two copies, they go out, they make two copies each and it's an exponential,
right? They quickly colonize the whole galaxy. But then the distance to the next galaxy, the next
big one like Andromeda, that's two and a half million light years. That's a much grander scale
now, right? And so it also could be that the reason they survived this long is that they got over
this tendency that may well exist among sufficiently intelligent creatures, this tendency for aggression
and self-destruction, right? If they bypassed that and that may be one of the great filters,
if there are more than one, right? Then they may not be a type of creature that feels the need
to go and say, oh, there's a nice looking planet and there's a bunch of ants on it.
Let's go squish them and colonize it. No, it could even be the kind of Star Trek-like
prime directive where you go and explore worlds, but you don't interfere in any way, right?
And also, we call it exploration as beautiful and everything, but there is underlying this
desire to explore, is a desire to conquer. I mean, if we're just being really honest about...
Right now, for us, it is, right?
And you're saying it's possible to separate, but I would venture to say that you wouldn't...
that those are coupled. So I could imagine a civilization that lives on for billions of years
that just stays on its... figures out the minimal effort way of just peacefully existing. It's like
a monastery. Yeah, and it limits itself. Yeah, it limits itself.
You know, it's planted its seeds in a number of places, so it's not vulnerable to a single
point failure, right? Supernova going off near one of these stars or something, or an asteroid,
or a comet coming in from the Oort cloud equivalent of that planetary system and
without threshing them to bits. So they've got their seeds in a bunch of places,
but they chose not to colonize the galaxy, and they also choose not to interfere with this
incredibly primitive organism, Homo sapiens, right? Or this is like a TV show for them.
Yeah, it could be like a TV show, right? So they just tuned in.
Right. So those are possible explanations, yet I think that to me, the most likely explanation
for the Parami paradox is that they really are very, very rare. And you know, Carl Sagan
estimated 100,000 of them. If there's that many, some of them would have been way ahead of us,
and I think we would have seen them by now. If there were a handful, maybe they're there,
but at that point, you're right on this dividing line between being a pessimist and an optimist.
And what are the odds for that, right? If you look at all the things that had to go right for us,
and then, you know, getting back to something you said earlier, let's discuss primitive life,
that could be the thing that's difficult to achieve, just getting the random molecules together
to a point where they start self-replicating and evolving and becoming better and all that.
That's an inordinately difficult thing, I think, though I'm not some molecular or
cell biologist, but just it's the usual argument, you know, you're wandering around in the Sahara
desert and you stumble across a watch. Is your initial response, oh, you know, a bunch of
sand grains just came together randomly and formed this watch? No, you think that something
formed it, or it came from some simpler structure that then became, you know, more complex.
All right, it didn't just form. Well, even the simplest life is a very, very complex structure.
Even the simplest prokaryotic cells, not to mention eukaryotic cells, although that transition
may have been the so-called great filter as well. Maybe the cells without a nucleus are
relatively easy to form, and then the big next step is where you have a nucleus, which then provides
a lot of energy, which allows the cell to become much, much more complex and so on. Interestingly,
going from eukaryotic cells, single cells to multicellular organisms does not appear to be,
at least on Earth, one of these great filters, because there's evidence that it happened dozens
of times independently on Earth. So by a really great filter, something that happens very, very
rarely, I mean that we had to get through an obstacle that is just incredibly rare to get through.
And one of the really exciting scientific things is that that particular point
is something that we might be able to discover, even in our lifetimes, that find life elsewhere,
like Europa. Because that would be bad news, right? Because if we find lots of pretty advanced
life, that would suggest, and especially if we found some defunct, you know, fossilized
civilization or something somewhere else, that would be... Oh, bacteria, you mean,
defunct civilization of primitive life. Oh, no, I'm sorry, I switched gears there. If we found
some intelligent or even trilobites and stuff elsewhere, that would be bad news for us because
that would mean that the great filter is ahead of us. Because it would mean that lots of things
have gotten roughly to our level. But given the Fermi Paradox, if you accept that the Fermi
Paradox means that there's no one else out there, you don't necessarily have to accept that. But
if you accept that, it means that no one else is out there. And yet there are lots of things
we've found that are at or roughly at our level, that means that the great filter is ahead of us
and that bodes poorly for our long-term future. Yeah, it's funny you said you started by saying
you're a little bit on the pessimistic side. But it's funny, because we're doing this kind of dance
between pessimism and optimism, because I'm not sure if us being alone in the observable universe
as intelligent beings is pessimistic. Well, it's good news in a sense for us,
because it means that we made it through. Oh, right. See, if we're the only ones,
and there are such great filters, maybe more than one, formation of life might be one of them.
Formation of eukaryotic that is with the nucleus cells be another. Development of human-like
intelligence might be another. There might be several such filters, and we were the lucky ones.
And then people say, well, then that means you're putting yourself into a special
perspective. And every time we've done that, we've been wrong. And yeah, I know all those
arguments, but it still could be the case that there's one of us, at least per galaxy, or per 10,
or 100, or 1,000 galaxies, and we're sitting here having this conversation because we exist.
And so there's an observational selection effect there, right? Just because we're special doesn't
mean that we shouldn't have these conversations about whether or not we're special, right?
Yeah, so that's exciting. That's optimistic. So that's the optimistic part, that if we don't
find other intelligent life there, it might mean that we're the ones that made it.
And in general, outside the great filter and so on, it's not obvious that the Stephen Hawking
thing, which is it's not obvious that life out there is going to be kind to us.
Oh, yeah. So I knew Hawking, and I greatly respect his scientific work, and in particular,
the early work on the unification of general theory of relativity and quantum physics to
two great pillars of modern physics, Hawking radiation and all that. Fantastic work.
If you were alive, you should have been a recipient of this year's Physics Nobel Prize,
which was for the discovery of black holes and also by Roger Penrose for the theoretical work,
showing that given a star that's massive enough, you basically can't avoid having a black hole.
Anyway, Hawking, fantastic. I tip my hat to him. May he rest in peace.
That would have been a heck of a Nobel Prize for black holes. Yeah, yeah, yeah.
A heck of a good group. But going back to what he said, that we shouldn't be
broadcasting our presence to others, there I actually disagree with him respectfully, because
first of all, we've been unintentionally broadcasting our presence for 100 years since
the development of radio and TV. Secondly, any alien that has the capability of coming here
and squashing us either already knows about us and doesn't care because we're just like little ants.
And when they're ants in your kitchen, you tend to squash them. But if they're ants on the sidewalk
and you're walking by, do you feel some great conviction that you have to squash any of them?
No, you generally don't. We're irrelevant to them. All they need to do is keep an eye on us
to see whether we're approaching the kind of technological capability and know about them
and have intentions of attacking them. And then they can squash us. They could have done it long
ago. They'll do it if they want to, whether we advertise our presence or not is irrelevant.
So I really think that that's not a huge existential threat.
So this is a good place to bring up a difficult topic. You mentioned they might,
they would be paying attention to us to see if we come up with any crazy technology.
There's folks who have reported UFO sightings. There's actually, I've recently found out there's
websites that track this, the data of these reportings. And there's millions of them
in the past several decades, so seven decades and so on, that they've been recorded.
And the ufologists community, as they refer to themselves, one of the ideas that I find
compelling from an alien perspective, that they kind of started showing up
ever since we figured out how to build nuclear weapons that we should.
With a coincidence.
So I mean, if I was an alien, I would just start showing up then as well.
Well, why not just observe us from afar?
I know, right. I would figure out, but that's why I'm always keeping a distance and staying blurry.
Very pixelated.
Very pixelated. There is something in the human condition that,
a cognition that wants to see, wants to believe beautiful things and some are terrifying,
some are exciting, goats, bigfoot is a big fascination for folks. And UFO sightings,
I think, falls into that. There's people that look at lights in the night sky and
I mean, it's kind of a downer to think in a skeptical sense, to think that's just a light.
You want to feel like there's something magical there.
Sure.
I mean, I felt that first with my dad as a physicist, when he first told me about ball
lightning when I was like a little kid.
Very weird.
Weird physical phenomena. And he said, his intuition was, tell me this as a little kid,
like I really like math, his intuition was whoever figures out ball lightning will get a
Nobel Prize. I think that was a side comment he gave me. I decided there when I was like five
years old or whatever, I'm going to win a Nobel Prize for figuring out ball lightning.
That was like one of the first sparks of the scientific mindset. Those mysteries,
they capture your imagination. I think when I speak to people that report UFOs,
that's that fire, that's what I see, that excitement.
Yeah, I understand that.
But what do we do with that? Because there's hundreds of thousands, if not millions,
and then the scientific community, you're like the perfect person. You have an awesome
Einstein shirt. What do we do with those reports? Most of the scientific community
kind of rolls their eyes and dismisses it. Is it possible that a tiny percent of those folks
saw something that's worth deeply investigating?
Sure, we should investigate it. It's just one of these things where
they've not brought us a hunk of kryptonite or something like that. They haven't brought us
actual tangible physical evidence with which experiments can be done in laboratories.
It's anecdotal evidence. The photographs are, in some cases, in most cases,
I would say quite ambiguous.
I don't know what to think about. David Freyver is the first person.
He's a Navy pilot, commander, and there's a bunch of them, but he's sort of
one of the most legit pilots and people I've ever met. The fact that he saw something weird,
he doesn't know what the heck it is, but he saw something weird. I mean,
I don't know what to do with that. On the psychological side, I'm pretty confident he
saw what he says he saw, which he's saying is something weird.
Right. One of the interesting psychological things that worries me is that everybody
in the Navy, everybody in the US government, everybody in the scientific community,
just kind of pretended that nothing happened. That kind of instinct,
that's what makes me believe if aliens show up, we would all just ignore their presence.
That's what bothered me, that you don't investigate it more carefully and use this
opportunity to inspire the world. In terms of kryptonite, I think the conspiracy theory folks
say that whenever there is some good hard evidence that scientists would be excited about,
there's this kind of conspiracy that I don't like because it's ultimately negative,
that the US government will somehow hide the good evidence to protect it. Of course,
there's some legitimacy to it because you want to protect military secrets, all that kind of stuff,
but I don't know what to do with this beautiful mess because I think millions of people are
inspired by UFOs and it feels like an opportunity to inspire people about science.
So I would say, as Carl Sagan used to say, extraordinary claims require extraordinary
evidence. I've quoted him a number of times. We would welcome such evidence. On other hand,
a lot of the things that are seen or perhaps even hidden from us, you could imagine
for military purposes, surveillance purposes, the US government doesn't want us to know,
or maybe some of these pilots saw Soviet or Israeli or whatever satellites. A lot of the,
or some of the crashes that have occurred were later found to be weather balloons or whatever.
When there are more conventional explanations, science tends to stay away from the sensational
wantons, right? And so it may be that someone else is calling in life is to investigate these
phenomena. And I welcome that as a scientist. I don't categorically actually deny the possibility
that ships of some sort could have visited us because, as I said earlier, at slow speeds,
there's no problem in reaching other stars. In fact, our Voyager and Pioneer spacecraft
in a few million years are going to be in the vicinity of different stars. We can even calculate
which ones they're going to be in the vicinity of, right? So there's nothing that breaks any laws
of physics if you do it slowly. But that's different. Just having Voyager or Pioneer fly by
some star, that's different from having active aliens altering the trajectory of their vehicle
in real time spying on us and then either zipping back to their home planet or sending
signals that tell them about us because they are likely many years, many light years away,
and they're not going to have broken that barrier as well. So I just go ahead, study them.
Great. For some young kid who wants to do it, it might be their calling. And that's how they
might find meaning in their lives is to be the scientist who really explores these things. I
chose not to because at a very young age, I found the evidence to the degree that I investigated it
to be really quite unconvincing. And I had other things that I wanted to do. But I don't
categorically deny the possibility, and I think it should be investigated.
Yeah. I mean, this is one of those phenomena that 99.9% of people are almost definitely,
there's conventional explanations. And then there's like mysterious things that probably have
explanations that are a little bit more complicated. But there's not enough to work with. I tend to
believe that if aliens showed up, there will be plenty of evidence for scientists to study.
Yeah. And exactly, as you said, avoid your type of spacecraft. I could see some kind of a dumb
thing, almost like a sensor to like probing, statistically speaking, flying by, maybe lands,
maybe there's some kind of robot type of thingies that just like move around and so on,
like in ways that we don't understand. But I feel like, well,
well, I feel like there'll be plenty of hard, hard to dismiss evidence. And I also, especially this
year, believe that the US government is not sufficiently competent, given the huge amount
of evidence that will be revealed from this kind of thing to conceal all of it. At least in modern
times, you can say maybe decades ago, but in modern times. But the people I speak to and
the reason I bring it up is because so many people write to me, they're inspired by it.
By the way, I wanted to comment on something you said earlier. Yeah, I had said that I'm sort of a
pessimist in that I think there are very few other intelligent, mechanically able creatures out there.
But then I said, yes, in a sense, I'm an optimist, as you pointed out, because it means that we made
it through the great filter, right? I meant originally that I'm a pessimist in that I'm
pessimistic about the possibility that there are many, many of us out there.
You know, mathematically speaking, in the Drake equation.
Exactly, right, right. But it may mean a good thing for our ultimate survival, right? So I'm
glad you caught me on that. Yeah, I definitely agree with you. It is ultimately an optimistic
statement. But anyway, I think UFO research is interesting. And I guess one of the reasons
I've not been terribly convinced is that I think there are some scientists who are
investigating this and they've not found any clear evidence. Now, I must admit, I have not
looked through the literature to convince myself that there are many scientists doing
systematic studies of these various reports. I can't say for sure that there's a critical mass of
them. But it's just that you never get these reports from hardcore scientists. That's
other thing. And astronomers, you know, what do we do? We spend our time studying the heavens.
And you'd think we'd be the ones that are most likely, aside from pilots, perhaps,
at seeing weird things in the sky. And we just never do of the unexplained UFO type nature.
Yeah, I definitely, I try to keep an open mind. But for people who listen,
it's actually really difficult for scientists. Like, I get probably,
like this year, I've probably gotten over, probably, maybe,
maybe over 1,000 emails on the topic of AGI. It's very difficult to,
you know, people write to me is like, how can you ignore this in AGI side, like this model?
This is obviously the model that's going to achieve general intelligence. How can you
ignore it? I'm giving you the answer. Here's my document. And there's always just these large
write-ups. The problem is, it's very difficult to weave through a bunch of BS.
It's very possible that you had actually saw the UFO, but you have to acknowledge
by UFO I mean an extraterrestrial life, you have to acknowledge the hundreds of thousands of people
who are a little bit, if not a lot, full of BS. And from a scientist's perspective,
it just, it's really hard work. And it's, when there's amazing stuff out there, it's like,
why invest big foot when evolution in all of its richness is beautiful? Who cares about a monkey
that walks on two feet or eight or whatever? It's like there's a zillion decoys at observatories.
True fact, we get lots and lots of phone calls when Venus, the evening star, but just really a
bright planet, happens to be close to the crescent moon because it's such a striking pair. This happens
once in a while. So we get these phone calls, oh, there's a UFO next to the moon. And no,
it's Venus. And so they're just, and I'm not saying the best UFO reports are of that nature.
No, there's some much more convincing cases. And I've seen some of the footage and blah,
blah, blah, blah. But it's just, there's so many decoys, right? So much noise that you have to
filter out. And there's only so many scientists. So it's hard. There's only so much time as well.
And you have to choose what problems you work on. This might be a fun question to ask to kind of
explore the idea of the expanding universe. So the radius of the observable universe is 45.7
billion light years. And the age of the universe is 13.7 billion years. That's less than the radius
of the universe. How's that possible? That's a great question. So I meant to bring a little
prop I have with ping pong balls and a rubber hose, a rubber band. I use it in many of the
lectures that one can find of me online. But you have, in an expanding universe, the space itself
between galaxies or, more correctly, clusters of galaxies expanding. So imagine light going from
one cluster to another. It traverses some distance. And then while it's traversing the rest,
that part that it already traveled through continues to expand. Now, 13.7 billion years might have gone
by since the light that we are seeing from the early stages, the so-called cosmic microwave
background radiation, which is the afterglow of the Big Bang or the echo of the Big Bang. Yeah,
13.7 billion years have gone by. That's how long it's taken that light to reach us. But while it's
been traveling that distance, the parts that it already traveled continue to expand. So it's like
you're walking on at an airport on one of these walkways, and you're walking along because you're
trying to get to your terminal. But the walkway is continuing as well. You end up traveling a
greater distance or the same distance faster is another way of putting it, right? That's why you
get on one of these traveling walkways. So you get roughly a factor of pi, but it's more like
3.2, I think. But when you work it all out, you multiply the number of years the universe has been
in existence by three and a quarter or so, and that's how you get this 46 billion light-year
radius. But how is that? Let me ask some nice dumb questions. How is that not traveling faster than
the speed of light? Yeah, it's not traveling faster than the speed of light because locally,
at any point, if you were to measure the light, the photon zipping past, it would not be exceeding
the speed of light. The speed of light is a locally measured quantity. After light has traversed
some distance, if the rubber band keeps on stretching, then yes, it looks like the light
traveled a greater distance than it would have had the space not been expanding. But locally,
it never was exceeding the speed of light. It's just that the distance through which it already
traveled then went often expanded on its own some more. And if you give the light credit,
so to speak, for having traversed that distance, well, then it looks like it's going faster than
the speed of light. But that's not how speed works. Right, that's not how speed works. And in
relativity also, the other thing that is interesting is that if you take two ping-pong balls that are
sufficiently far apart, especially in an accelerating universe, you can easily have them moving apart
from one another faster than the speed of light. So take two ping-pong balls that were originally
400,000 kilometers from each other and let every centimeter in your rubber band expand to two in
one second. Then suddenly, this 400,000 kilometer distance is 800,000 kilometers. It went out by
400,000 kilometers in one second. That exceeds the 300,000 kilometer per second speed of light.
But that light limit, that particle limit in special relativity applies to objects moving
through a preexisting space. There's nothing in either special or general relativity that
prevents space itself from expanding faster in the speed of light. That's no problem. Einstein
wouldn't have had a problem with a universe as observed now by cosmologists.
Yeah, I'm not sure I'm yet ready to deal emotionally with expanding space. That, to me,
is one of the most awe-inspiring things starting from the Big Bang.
That's definitely abstract.
As space itself is expanding. Can we talk about the Big Bang a little bit?
Sure. The entirety of it, the universe, was very small.
It was not a point because if we live in what's called a closed universe now,
a sphere or the three-dimensional version of that would be a hypersphere.
Then, regardless of how far back in time you go, it was always that topological shape.
You can't turn a point suddenly into a shell. It always had to be a shell.
When people say, well, the universe started out as a point, that's being kind of flippant,
kind of glib. It didn't really. It just started out at a very high density. We don't know,
actually, whether it was finite or infinite. I think, personally, that it was finite at the time,
but it expanded very, very quickly. Indeed, if it expanded and continued in some places to
exponentiate, then it could, in fact, be infinite right now. Most cosmologists think that it is
infinite. Wait, what infinite, which dimension, mass size?
Infinite in space. By that, I mean that if you were trying to measure, use light to measure its
size, you'd never be able to measure its size because it would always be bigger than the distance
light can travel. That's what you get in a universe that's accelerating in its expansion.
Okay, but if a thing was a hypersphere, it's very small, not a point, how can that thing be infinite?
Well, it expands exponentially. That's what the inflation theory is all about. Indeed,
at your home institution, Alan Gooth is one of the originators of the whole inflationary
universe idea, along with Andre Linde at Stanford University here in the Bay Area,
and others, Alexei Strabinski and others had similar sorts of ideas. But in an exponentially
expanding universe, if you actually try to make this measurement, you send light out to try to
see it curve back around and hit you in the back of the head, if it's an exponentially
expanding universe, the amount of space remaining to be traversed is always a bigger and bigger
quantity. So you'll never get there from here. You'll never reach the back of your head. So
observationally or operationally, it can be thought of as being infinite.
That's one of the best definitions of infinity, by the way. That's one of the best physical
manifestations of infinity. Yeah, because you have to ask, how would you actually measure it?
Now, I sometimes say to my cosmology theoretical friends, well, if I took, if I were God, and I
were outside this whole thing, and I took a God-like slice in time, wouldn't it be finite,
no matter how big it is? And they object and they say, Alex, you can't be outside and take a
God-like slice of time, you know. Because there's nothing outside.
Well, I'm not, you know, or also, you know, what slice of time you're taking depends on your motion.
And that's true even in special relativity, that slices of time get tilted, in a sense,
if you're moving quickly, the axes, X and T, actually become tilted, not perpendicular to one
another. And, you know, you can look at Brian Green's books and lectures and other things,
where he imagines taking a loaf of bread and slicing it in units of time as you progress
forward. But then if you're zipping along relative to that loaf of bread, the slices of time actually
become tilted. And so it's not even clear what slices of time mean. But I'm an observational
astronomer. I know which end of the telescope to look through. And the way I understand the
infinity is, as I just told you, that operationally or observationally, there'd be no way of seeing
that it's a finite universe, of measuring a finite universe. And so in that sense,
it's infinite, even if it started out as a finite little dot. Well, not a dot, I'm sorry,
a finite little hypersphere. But it didn't really start out there. Because what happened before
that? Well, we don't know. So this is where it gets into a lot of speculation. And let's go,
I mean, let's go there. Okay, sure. So nobody can prove you wrong. The idea of what happened before
t equals zero and whether there are other universes out there. I like to say that these
are sort of on the boundaries of science. They're not just ideas that we wake up at three in the
morning to go to the bathroom and say, oh, well, let's think about what happened before the Big
Bang or let there be a multiplicity of universes. In other words, we have real testable physics
that we can use to draw certain conclusions that are plausibility arguments based on what
we know. Now, admittedly, there are not really direct tests of these hypotheses. That's why
I call them hypotheses. They're not really elevated to a theory because a theory in science is
really something that has a lot of experimental or observational support behind it. So they're
hypotheses. But they're not unreasonable hypotheses based on what we know about general relativity
and quantum physics. And they may have indirect tests in that if you adopt this hypothesis,
then there might be a bunch of things you expect of the universe. And lo and behold,
that's what we measure. But we're not actually measuring anything at t less than zero. Or we're
not actually measuring the presence of another universe in this multiverse. And yet there are
these indirect ideas that stem forth. So it's hard to prove uniqueness. And it's hard to completely
convince oneself that a certain hypothesis must be true. But the more and more tests you have that
it satisfies, let's say there are 50 predictions it makes. And 49 of them are things that you can
measure. And then the 50th one is the one where you want to measure the actual existence of that
other universe or what happened before t equals zero. And you can't do that. But you've satisfied
49 of the other testable predictions. And so that's science, right? Now, a conventional
condensed matter physicist or someone who deals with real data in the laboratory might say,
oh, you cosmologists, that's not really science, because it's not directly testable. But I would
say it's sort of testable. But it's not completely testable. And so it's at the boundary. But it's
not like we're coming up with these crazy ideas, among them quantum fluctuations out of nothing.
And then inflating into a universe with, you might say, well, you created a giant amount of
energy. But in fact, this quantum fluctuation out of nothing, in a quantum way, violates the
conservation of energy. But who cares? That was a classical law anyway. And then an inflating
universe maintains whatever energy it had, be it zero or some infinitesimal amount. In a sense,
the stuff of the universe has a positive energy, but there's a negative gravitational energy
associated with it. It's like I drop an apple. I got kinetic energy, energy of motion out of that.
But I did work on it to bring it to that height. So by going down and gaining energy of motion,
positive one, two, three, four, five units of kinetic energy, it's also gaining or losing,
depending on how you want to think of it, negative one, two, three, four, five units of
potential energy. So the total energy remains the same. An inflating universe can do that. Or
other physicists say that energy isn't conserved in general relativity. That's another way out of
creating a universe out of nothing. But the point is that this is all based on reasonably well
tested physics. And although these extrapolations seem outrageous at first, they're not completely
outrageous. They're within the realm of what we call science already. And maybe some young
whipper snapper will be able to figure out a way to directly test what happened before
T equals zero or to test for the presence of these other universes. But right now, we don't
have a way of doing that. So speaking of young whipper snappers, Roger Penrose.
So he has an idea that there may be some information that travels from whatever
the heck happened before the Big Bang. Yeah, maybe. I doubt it.
So do you think it's possible to detect something like actually experimentally be able to detect some?
I don't know what it is, radiation, some sort of cosmic microwave background radiation. There
may be ways of doing that. But is it is it philosophically or practically possible to
detect signs that this was before the Big Bang? Or is it or is it what you said, which is like
everything we observe will, as we currently understand, will have to be a creation of this
particular observable universe? Yeah, I mean, you know, if you it's very difficult to answer right
now, because we don't have a single verified, fully self consistent, experimentally tested
quantum theory of gravity. Right. And of course, the beginning of the universe
is a large amount of stuff in a very small space. Yeah. So you need both quantum mechanics and
general relativity. Same thing if our universe recollapses and then bounces back to another
Big Bang. You know, there's also ideas there that some of the information leaks through
or survives. I don't know that we can answer that question right now, because we don't have
a quantum theory of gravity that most physicists believe in and belief is perhaps the wrong word
that most physicists trust because the experimental evidence favors it. Yeah. Right.
Yeah, there are various forms of string theory. There's quantum loop gravity. There are various
ideas. But which if any will be the one that survives the test of time and more importantly,
within that the test of experiment and observation. Yeah. So my own feeling is probably these
things don't survive. I don't think we've seen any evidence in the cosmic microwave background
radiation of information leaking through. Similarly, the one way or one of the few ways
in which we might test for the presence of other universes is if they were to collide with ours,
that would leave a pattern, a temperature signature in the cosmic microwave background
radiation. Some astrophysicists claim to have found it. But in my opinion, it's not statistically
significant to the level that would be necessary to have such an amazing claim. It's just a 5%
chance that the microwave background had that distribution just by chance. 5% isn't very long
odds if you're claiming that instead that you're finding evidence from another universe. I mean,
it's like if the Large Hadron Collider people had claimed after gathering enough data to show
the Higgs particle when there was a 5% chance it could be just a statistical fluctuation
in their data. No, they required 5 sigma, 5 standard deviations, which is roughly
one chance in 2 million that this is a statistical fluctuation of no physical
greater significance. Extraordinary claims require extra.
There you go. It all boils down to that. And the greater your claim, the greater is the evidence
that is needed. And the more evidence you need from independent ways of measuring or of coming to
that deduction. A good example was the accelerating universe. When we found evidence for it in 1998
with supernovae, with exploding stars, it was great that there were two teams that
lent some credibility to the discovery. But it was not until other astrophysicists used
not only that technique, but more importantly, other independent techniques that had their own
potential sources of systematic error or whatever. But they all came to the same conclusion. And
that started giving a much more complete picture of what was going on and a picture in which
most astrophysicists quickly gained confidence. That's why that idea caught on so quickly,
is that there were other physicists and astronomers doing observations completely independent of
supernovae that seemed to indicate the same thing. Yeah. That period of your life that
work with an incredible team of people that won the Nobel Prize is just fascinating work.
Oh, gosh. Never in my wildest dreams as a kid did I think that I would be involved,
much less so heavily involved, in a discovery that's so revolutionary. I mean, as a kid,
as a scientist, if you're realistic, once you learn a little bit more about how science is done
and you're not going to win a Nobel Prize and be the next Newton or Einstein or whatever,
you just hope that you'll contribute something to humankind's understanding of
how nature works. And you'll be satisfied with that. But here, I was in the right place at
the right time, a lot of luck, a lot of hard work. And there it was. We discovered something
that was really amazing. And that was the greatest thrill, right? I couldn't have asked for anything
more than being involved in that discovery. So the couple of teams, the supernova cosmology
project and the high Z supernova search team. So what was the Nobel Prize given for?
It was given for the discovery of the accelerating expansion of the universe.
Not for the elucidation of what dark energy is or what causes that expansion,
that acceleration be it universes on the outside or whatever. It's just only for the observational
fact. So first of all, what is the accelerating universe? So the accelerating universe is simply
that if we look at the galaxies moving away from us right now, we would expect them to be moving
away more slowly than they were billions of years ago. And that's because galaxies have
visible matter, which is gravitationally attractive and dark matter of an unknown sort that holds
galaxies together and holds clusters of galaxies together. And of course, they then pull on one
another and they would tend to retard the expansion of the universe. Just as when I toss an apple up,
you know, even ignoring air resistance, the mutual gravitational attraction between earth
and the apple slows the apple down. And if that attraction is great enough, then the apple will
someday stop and even come back. The big crunch you could call it or the Gnabagib, which is big bang
backwards, right? That's what could have happened to the universe. But even if the universe's
original expansion energy was so great that it avoids the big crunch, that's like an apple thrown
at earth's escape speed. It's like the rockets that go to Mars someday, right? You know,
with people. Even then, you'd expect the universe to be slowing down with time. But we looked back
through the history of the universe by looking at progressively more distant galaxies.
And by seeing that the evolution of this expansion rate is that in the first nine billion years,
yeah, it was slowing down. But in the last five billion years, it's been speeding up. So who asked
for that, right? You know. I think it's interesting to talk about a little bit of the human story of
the Nobel Prize, which is fascinating. First of all, the prize itself. It's kind of fascinating
on the psychological level. I know we kind of think that prizes don't matter, but somehow they
kind of focus the mind about some of the most special things we've accomplished. They do. It's
the recognition, the funding, you know. And also inspiration for, like I said, when I was a little
kid, they gave me the Nobel Prize. It inspires millions of young scientists. At the same time,
there's a sadness to it a little bit that especially in the field, like depending on the
field, but experimental fields that involve teams of, I don't know, sometimes hundreds of brilliant
people. The Nobel Prize is only given to just a handful. That's right. Is it maxed at three?
Yeah. And it's not even written in Alfred Nobel's will, it turns out. One of our teammates looked
into it in a museum in Stockholm when we went there for Nobel week in 2011. The leaders who got
the prize formally knew that without the rest of us working hard in the trenches, the result would
not have been discovered. So they invited us to participate in Nobel week. And so one of the team
members looked in the will and it's not there. It's just tradition. That's interesting.
But it's archaic. That's the way science used to be done. And it's not the way a lot of science
is done now. And you look at gravitational wave discovery, which was recognized with the Nobel
Prize in 2017. Ray Weiss at MIT got it and Kip Thorne and Barry Bearish at Caltech. And Ron
Driever, one of the masterminds, had passed away earlier in the year. So again, one of the rules
of the Nobel is that it's not given posthumously. Or at least the one exception might be if they've
made their decision and they're busy making their press releases right before October,
the first week in October or whatever. And then the person passes away. I think they don't change
their minds then. But yeah, you know, it doesn't square with today's reality that a lot of science
is done by big teams. In that case, a team of 1,000 people. In our case, it was two teams
consisting of about 50 people. And we used techniques that were arguably developed in part by people
who, astrophysicists who weren't even on those two papers. I mean, some of them were, but
other papers were written by other people. And so it's like we're standing on the shoulders of
giants. And none of those people was officially recognized. And to me, it was okay. Again,
it was the thrill of doing the work. And ultimately, the work, the discovery was recognized with the
prize. And, you know, we got to participate in Nobel week. And, you know, it's okay with me.
I've known other physicists whose lives were ruined because they did not get the Nobel prize.
And they felt strongly that they should have. Ralph Alpha of the Alpha Beta Gamoff, you know,
paper predicting the microwave background radiation, he should have gotten it. His advisor Gamoff was
dead by that point. But, you know, Penzius and Wilson got it for the discovery. And Alpha,
apparently from colleagues who knew him while I've talked to them, his life was ruined by this.
He just, it just not at his innards so much. It's very possible that in a small handful of people,
even three, that you would be one of the Nobel, one of the winners of the Nobel prize.
That doesn't weigh heavy on you. Well, you know, there were the two team leaders,
Saul Perlmutter and Brian Schmidt. And usually there's the team leaders that are recognized.
And then Adam Reese was my postdoc. First author, I guess. Yeah, first author. I was
second author of that paper. Yeah. So I was his direct mentor at the time, although he was, you
know, one of these people who just, you know, runs with things. He was an MIT undergraduate,
by the way, Harvard graduate student, and then a postdoc as a so-called Miller Fellow
for basic research and science at Berkeley, something that I was back in 84 to 86. But
you're, you know, you're largely a free agent. But he worked quite closely with me. And he
came to Berkeley to work with me. And on Schmidt's team, he was charged with analyzing the data.
And he measured the brightnesses of these distant supernovae, showing that they're fainter and
thus more distant than anticipated. And that led to this conclusion that the universe had to have
accelerated in order to push them out to such great distances. And I was shocked when he showed me
the data, the results of his calculations and measurements. But it's very, you know, so he
deserved it. And on Saul's team, Gerson Goldhaber deserved it. But he died, I think, a year earlier
in 2010. But that would have been four. And so, and me, well, I was on both teams, but, you know,
was I number four, five, six, seven, I don't know. It's also very, so if I were to, it's possible
that you're, I mean, I could make a very good case for you in the three. And does that cycle,
you're kind, you know, but is that psychologically, I mean, listen, it weighs on me a little bit,
because I, I don't know what to do with that. It perhaps it should motivate
the rethinking like Time Magazine started doing like, you know, Person of the Year. And like,
they would start doing like concepts and almost like the black hole gets the Nobel Prize. Or
University gets the Nobel Prize and here's the list of people. So like, or like the Oscar
that you could say, yeah, because it, it's a team effort now. It's a team. It should be redone. And
the breakthrough prize in fundamental physics, which was started by Yuri Milner and Zuckerberg
is involved in others as well, you know, they recognize the larger team. Yeah, they recognize
teams. And so in fact, both teams in the accelerating universe were recognized with the breakthrough
prize in 2015. Nevertheless, the same three people, Rhys, Pearl, Mutter and Schmidt, got the red carpet
rolled out for them and were at the big ceremony and shared half of the prize money. And the rest
of us roughly 50 shared the other half and didn't get to go to the ceremony. So, but I, I feel for
them. I mean, for the gravitational waves, it was 1000 people. What are they going to do? Invite
everyone for the Higgs particle. It was 68000 physicists and engineers. In fact, because
of the whole issue of who gets it, experimentally, that discovery still has not been recognized,
right? The theoretical work by Peter Higgs and Anglaire got recognized. But there was a troika
of other people who perhaps wrote the most complete paper and they were, they were left out. And
another guy died, you know, and it's hard. It's all of its heartbreak. And some people argue that
the Nobel Prize has been deluded to because if you look at Roger Penrose, you can make an argument
that he should get the prize by himself. Like, it's just separate those like, could have and should
have perhaps he should have perhaps gotten it with Hawking before Hawking's death. Yeah. Right.
The problem was Hawking radiation had not been detected. But you could argue that Hawking made
enough other fundamental contributions to the theoretical study of black holes. And the observed
data were already good enough at the time of before Hawking's death. Okay. I mean, the latest
results by Reinhard Genzel's group is that they see the time dilation effect of a star that's
passing very close to the black hole in the middle of our galaxy. That's cool. And it adds
additional evidence. But hardly anyone doubted the existence of the supermassive black hole. And
Andrea Gez's group, I believe hadn't yet shown that relativistic effect. And yet she got part
of the prize as well. So clearly, it was given for the original evidence that was really good.
And that evidence is at least a decade old, you know. So one could make the case for Hawking.
One could make the case that in 2016, when Mayor and K. Lowe's won the Nobel Prize for
the discovery of the first exoplanet, 51B Pegasi, well, there was a fellow at Penn State, Alex
Walshahn, who in 1992, three years preceding 1995, found a planet orbiting a pulsar, a very weird
kind of star, a neutron star. And that wouldn't have been a normal planet, sure. And so the
Nobel committee, you know, they gave it for the discovery of planets around normal, sun-like stars.
But hell, you know, Walshahn found a planet. So they could have given it to him as the third
person instead of to Jim Peebles for the development of what's called physical cosmology.
He's at Princeton. He deserved it. But they could have given Nobel for the development of
physical cosmology to Peebles. And I would claim some other people were pretty important in that
development as well. You know, and they could have given it some other year. So there's a lot
of controversy. I try not to dwell on it. Was I number three? Probably not. You know,
Adam Reese did the work. You know, I helped bounce ideas off of him, but we wouldn't have had the
result without him. And I was on both teams for reasons. I mean, you know, the style of the first
team, the Supernova Cosmology Project didn't match mine. They came largely from experimental
high-energy particle physics, where there's these hierarchical teams and stuff. And it's hard for
the little guy to have a say. At least that's what I kind of thought. Whereas the team of
astronomers led by Brian Schmidt was, first of all, a bunch of my friends, and they grew up as
astronomers making contributions on little teams, and we decided to band together. But all of us
had our voices heard. So it was sort of a culture, a style that I preferred, really. But let me tell
you a story. At the Nobel banquet, okay, I'm sitting there between two physicists who are
members of the committee of the Swedish National Academy of Sciences. And I strategically kept
offering them wine and stuff during this long, drawn-out Nobel ceremony. And I got them to
be pretty talkative. And then in a polite diplomatic way, I started asking them pointed
questions. And basically, they admitted that if there are four or more people equally deserving,
they wait for one of them to die. Or they just don't give the prize at all when it's unclear
who the three are, at least unclear to them. But unclear to them, they're not even right
part of the time. I mean, Jocelyn Bell discovered pulsars with a radio antennas, a set of radio
antennas that her advisor, Anthony Hewish, conceived and built. So he deserves some credit.
But he didn't discover the pulsar. She did. And his initial reaction to the data that she showed
him was a condescending rubbish, my dear. Yeah, I'm not kidding. Now, I know Jocelyn Bell and she
did not let this destroy her life. She won every other prize under the sun, okay? Vera Rubin,
arguably one of the discoverers of Dark Matter. Although there, if you look at the history,
there were a number of people. That was the issue. I think there were a number of people,
four or more, who had similar data and similar ideas at about the same time. Rubin won every
prize under the sun. The new big large-scale survey telescope being built in Chile is being
renamed the Vera Rubin telescope, because she passed away in December of 2015, I think.
It'll conduct this large-scale survey with the Rubin telescope. So she's been recognized,
but never with the Nobel Prize. And I would say that to her credit, she did not let that consume
her life either. And perhaps it was a bit easier because there had been no Nobel given
for the discovery of Dark Matter. Whereas in the case of Pulsars and Jocelyn Bell,
there was a prize given for the discovery of the freaking Pulsars. And she didn't get it.
What a travesty of justice. So I also think, as a fan of fiction, as a fan of stories, that the
travesty and the tragedy and the unfairness and the tension of it is what makes the prize and
similar prize is beautiful. The decisions of other humans that result in dreams being broken.
That's why we love the Olympics, as so many people, athletes, give their whole life for this
particular moment. And then there's referee decisions and little slips of here and there,
like the little misfortunes that destroy entire dreams. And it's weird to say, but it feels like
that makes the entirety of it even more special. If it was perfect, it wouldn't be interesting.
Well, humans like competition and they like heroes. And unfortunately, it gives the impression
to youngsters today that science is still done by white men with gray beards wearing white lab
coats. And I'm very pleased to see that this year, Andrea Gez, the fourth woman in the history of
the physics prize, to have received it. And then two women, one at Berkeley, one elsewhere,
won the Nobel Prize in chemistry without any male co-recipient. And so that's sending a message,
I think, to girls that they can do science and they have role models. I think the breakthrough
prize and other such prizes show that teams get recognized as well. And if you pay attention to
the newspapers, most of the good authors like Dennis Overby of the New York Times and others
said that these were teams of people and they emphasize that. And they all played a role.
And maybe if some grad student hadn't soldered some circuit, maybe the whole thing wouldn't
have worked. But still, Ray Weiss, Kip Thorne was the theoretical impetus for the whole search
for gravitational waves. Barry Barish brought the MIT and Caltech teams together to get them
to cooperate at a time when the project was nearly dead from what I understand and contributed
greatly to the experimental setup as well. He's a great experimental physicist, but he was really
good at bringing these two teams together instead of having them duke it out and blows and leaving
both of them bleeding and dying. The National Science Foundation was going to cut the funding
from what I understand. So there's human drama involved in this whole thing. And the Olympics,
yeah, a runner or a swimmer, a runner, they slip just at the moment they were taking off
from the first thing and that costs them some fraction of a second and that's it. They didn't
win. And in that case, I mean, the coaches, the families, which I've met a lot of Olympic
athletes and the coaches and the families of the athletes are really the winners of the medals.
But they don't get the medal. And it's credit assignment is a fascinating thing. I mean,
that's the full human story. And outside of prizes, it's fascinating. I mean,
just to be in the middle of it for artificial intelligence, there's a field of deep learning
that's really exciting. And people have been there's a yet another award, the touring awards
given for deep learning to three folks who are very much responsible for the field. But so are a
lot of others. Yeah, that's right. And there's a few there's a there's a fellow by the name of
Schmidt Hooper, who sort of symbolizes the the forgotten folks in the deep learning community.
But you know, that's that's the unfortunate sad thing where you remember or remember Isaac Newton
or remember these these these special figures and the ones that flew close to them. We forget.
Well, that's right. And you know, often the breakthroughs are made based on the body of
knowledge that had been assimilated prior to that. But you know, again, people like to worship heroes
you mentioned the Oscars earlier. And, you know, you look at the direct, I mean, well, I mean,
okay, directors and stuff sometimes get awards and stuff. But you know, you look at even something
like, I don't know, songwriters, musicians, Elton John or something, right, Bernie Taupin, right,
right, wrote many of the words or he's not as well known or or the Beatles or something like
that. I was heartbroken to learn that Elvis didn't write most of the songs. Yeah, Elvis,
that's right. There you go. But he was the king, right? And he had such a personality. And he was
such a performer. Right. It's the unsung heroes in many cases. Yeah. So maybe taking a step back,
we talked about the Nobel Prize for the Accelerating Universe, but your work and the ideas around
supernova were important in detecting this Accelerating Universe. Can we go to the very basics
of what is this beautiful mysterious object of a supernova? Right. So a supernova is an exploding
star. Most stars die a relatively quiet death or our own Sun well, despite the fact that it'll
become a red giant and incinerate Earth, it'll do that reasonably slowly. But there's a small minority
of stars that end their lives in a titanic explosion. And that's not only exciting to watch
from afar, but it's critical to our existence because it is in these explosions that the heavy
elements synthesize through nuclear reactions during the normal course of the star's evolution
and during the explosion itself get ejected into the cosmos, making them available as raw material
for new stars, planets, and ultimately life. And that's just a great story, the best in some ways.
So we like to study these things and our origins, but it turns out these are incredibly useful
beacons as well. Because if you know how powerful an exploding star really is by measuring the
apparent brightness at its peak in galaxies whose distances we already know through having
made other measurements, and you can thus calibrate how powerful the thing really is,
and then you find ones that are much more distant, then you can use their observed brightness
compared with their true intrinsic power or luminosity to judge their distance and hence
the distance of the galaxy in which they're located. Let me just give this one analogy.
You judge the distance of an oncoming car at night by looking at how bright its headlights
appear to be, and you've calibrated how bright the headlights are of a car that's two or three
meters away of known distance. And you go, whoa, that's a faint headlight. And so that's
pretty far away. You also use the apparent angular separation between the two headlights
as a consistency check in your brain. But that's what your brain is doing. So we can do that for
cars, we can do that for stars. Nice, I like that. But with cars, the headlights are all,
there's some variation, but they're somewhat similar. So you can make those kinds of conclusions.
What, how much variation is there between supernova that you can, can you detect them?
Right. So first of all, there are several different ways that stars can explode,
and it depends on their mass and whether they're in a binary system and things like that.
And the ones that we used for these cosmological purposes, studying the expansion of the history
of the universe, are the so-called type Roman numeral one lowercase A, type 1A supernovae.
They come from a weird type of a star called a white dwarf. Our own sun will turn into a
white dwarf in about seven billion years. It'll have about half its present mass compressed
into a volume just the size of Earth. So that's an inordinate density. Okay, it's incredibly dense.
And the matter is what's called by quantum physicists degenerate matter,
not because it's morally reprehensible or anything like that. But this is just the
name that quantum physicists give to electrons that are squeezed into a very tight space.
The electrons take on a motion due to Heisenberg's uncertainty principle and also due to the
Pauli exclusion principle that electrons don't like to be in the same place. They like to
avoid each other. So those two things mean that a lot of electrons are moving very rapidly,
which gives the star an extra pressure far above the thermal pressure associated with
just the random motions of particles inside the star. So it's a weird type of star. But
normally it wouldn't explode and our sun won't explode, except that if such a white dwarf is
in a pair with another more or less normal star, it can steal material from that normal star until
it gets to an unstable limit, roughly one and a half times the mass of our sun, 1.4 or so.
This is known as the Chandrasekhar limit after Subramanyan Chandrasekhar, an Indian astrophysicist
who figured this out when he was about 20 years old on a voyage from India to England,
where he was to be educated. And then he did this. And then 50 years later, he won the Nobel Prize
in physics in 1984, largely for this work that he did as a youngster who was on his way to be
educated. Oh, and his advisor, the great Arthur Eddington in England, who had done a lot of
great things and was a great astrophysicist. Nevertheless, he too was human and had his
faults. He ridiculed Chandra's scientific work at a conference in England. And most of us,
if we had been Chandra, would have just given up astrophysics at that time when the great
Arthur Eddington ridicules our work. That's another inspirational story for the youngster.
Just keep going. Ignore your advisors. No matter what your advisor says.
So, or don't always pay attention to your advisor. Don't lose hope if you really think you're on
to something. That doesn't mean never listen to your advisor. They may have sage advice as well.
But anyway, when a white dwarf grows to a certain mass, it becomes unstable. And one of the ways
it can end its life is to go through a thermonuclear runaway. So basically, the carbon nuclei inside
the white dwarf start fusing together to form heavier nuclei. And the energy that those fusion
reactions emit doesn't go into being dissipated out of the star or whatever, or expanding it the
way. If you take a blow torch to the middle of the sun, you heat up its gases. The gases would
expand and cool. But this degenerate star can't expand and cool. And so the energy pumped in
through these fusion reactions goes into making the nuclei move faster. And that gets more of them
sufficiently close together that they can undergo nuclear fusion, thereby releasing more energy that
goes into speeding up more nuclei. And thus you have a runaway, a bomb, an uncontrolled fusion
reactor. Right. Instead of the controlled fusion, which is what our sun does. Okay. Our sun is a
marvelous controlled fusion reactor. This is what we need here on Earth, fusion energy to solve our
energy crisis, right? But the sun holds the stuff in through gravity, and you need a big mass to do
that. So this uncontrolled fusion reaction blows up a star that's pretty much the same in all cases.
And you measure it to be almost the same in all cases. But the devil is in the details,
and in fact, we observe them to not be all the same. And theoretically, they might not be all
the same because the rate of the fusion reactions might depend on the amount of trace heavier elements
in the white dwarf. And that could depend on how old it is when it was, you know, whether it was
born billions of years ago, when there weren't many heavier elements, or whether it's a relatively
young white dwarf and all kinds of other things. And part of my work was to show that indeed,
not all the type 1a's are the same, you have to be careful when you use them, you have to
calibrate them. They're not standard candles. The way it just, if all headlights or all candles were
the same lumens or whatever, you'd say they're standard, and then it would be relevant.
Standard candles is an awesome term. Okay. Standard candles is what astronomers like to say,
but I don't like that term because there aren't any standard candles, but there are standard
izable candles. And by looking at these type 1a, yeah, you calibrateable, standardizable,
calibrateable, you look at enough of them in nearby galaxies whose distances you know independently.
And what you can tell is that, you know, this is something that a colleague of mine, Mark Phillips,
did who was on Schmidt's team, and arguably one of the, was one of the people who deserved the
Nobel Prize, but he showed that the intrinsically more powerful type 1a's decline in brightness,
and it turns out rise in brightness as well, more slowly than the less luminous 1a's. And so,
if you calibrate this by measuring a whole bunch of nearby ones, and then you look at a distant one,
instead of saying, well, it's a 100 watt type 1a supernova, they're much more powerful than that,
by the way. Plus or minus 50, you can say, no, it's 112 plus or minus 15, or it's 84 plus or
minus 17. It tells you where it is in the power scale, and it greatly decreases the uncertainties.
And that's what makes these things cosmologically useful. I showed that if you spread the light
out into a spectrum, you can tell spectroscopically that these things are different as well. And
in 1991, I happened to study two of the extreme peculiar ones, the low luminosity ones and the
high luminosity ones, 1991 BG and 1991 T. This showed that not all the 1a's are the same. And
indeed, at the time of 1991, I was a little bit skeptical that we could use type 1a's because
of this diversity that I was observing. But in 1993, Mark Phillips wrote a paper that showed
this correlation between the light curve, the brightness versus time, and the peak luminosity.
Which gives you enough information to calibrate. Yeah, then they become calibratable. And that
was a game changer. How many type 1a's are out there to use for data? Now there are thousands
of them. But at the time, the high Z team had 16. And the Supernova Cosmology project had 40.
But the 16 were better measured than the 40. And so our statistical uncertainties were
comparable if you look at the two papers that were published.
How does that make you feel that there's these gigantic explosions just sprinkled out there?
Well, I certainly don't want one to be very nearby. And it would have to be within something like
10 light years to be an existential threat. So they can happen in our galaxy?
Oh, yeah, yeah. So they would be okay. In most cases, we'd be okay. Because our galaxy is 100,000
light years across. And you'd need one of these things to be within about 10 light years to be
an existential threat. And it gives birth to a bunch of other stars, I guess.
Yeah, it gives birth to expanding gases that are chemically enriched. And those expanding gases
mixed with other chemically enriched expanding gases or primordial clouds of hydrogen and helium.
I mean, this is, in a sense, the greatest story ever told, right? I teach this introductory
astronomy course at Berkeley. And I tell them there's only five or six things that I want them
to really understand and remember. And I'm going to come to their deathbed. And I'm going to ask
them about this. And if they get it wrong, I will retroactively fail. Their whole career will
have been shot that they don't know and observe a total solar eclipse. And yet they had the
opportunity to do so. I will retroactively fail them. But one of them is, you know,
where did we come from? Where did the elements in our DNA come from? The carbon in our cells,
the oxygen that we breathe, the calcium in our bones, the iron in our red blood cells,
those elements, the phosphorus in our DNA, they all came from stars, from nuclear reactions in
stars. And they were ejected into the cosmos. And in some cases, like iron made during the
explosions. And those gases drifted out, mixed with other clouds, made a new star or a star cluster,
some of whose members then evolved and exploded, thus enriching the gases in the galaxy progressively
more with time. Until finally, four and a half billion years ago, from one of these chemically
enriched clouds, our solar system formed with a rocky earth-like planet. And somewhere, somehow,
these self replicating, evolving molecules, bacteria formed and evolved through
paramecia and amoebas and slugs and apes and us. And here we are, sentient beings,
that can ask these questions about our very origins. And with our intellect, and with the
machines we make, come to a reasonable understanding of our origins. What a beautiful story. I mean,
if that does not put you, at least in awe, if not in love with science and its power
of deduction, I don't know what will, right? It's one of the greatest stories, if not the greatest
story. Obviously, that's personality dependent and all that. It's a subjective opinion, but
it's perhaps the greatest story ever told. I mean, you could link it to the Big Bang and go even
farther to make an even more complete story. But as a subset, that's even, in some ways,
a greater story than even the existence of the universe in some ways. Because you could end up,
you could just imagine some really boring universe that never leads to sentient creatures such as
ourselves. And is the supernova usually the introduction to that story? So are they usually
the thing that launches the... Is there other engines of creation? Well, the supernova is the
one... I mean, I touch upon the subject earlier in my course, in fact, right about now in my
lectures, because I talk about how our sun right now is fusing hydrogen to form helium nuclei.
And later, it'll form carbon and oxygen nuclei. But that's where the process will stop for our sun.
It's not massive enough. Some stars that are more massive can go somewhat beyond that.
So that's the beginning of this idea of the birth of the heavy elements, since they couldn't have
been born at the time of the Big Bang. Conditions of temperature and pressure weren't sufficient to
make any significant quantities of the heavier elements. And so that's the beginning. But then
you need some of these stars to explode. Because if those heavy elements remained forever trapped
in the cores of stars, then they would not be available for the production of new stars,
planets, and ultimately life. So indeed, the supernova, my main area of interest,
plays a leading role in this whole story. I saw that you got a chance to call Richard Feynman
a mentor of yours when you were at Caltech. Do you have any fond memories of Feynman,
any lessons that stick with you? Oh, yeah. He was quite a character
and one of the deepest thinkers of all time, probably. And at least in my life,
the physicist who had the single most intuitive understanding of how nature works, of anyone
I've met, I learned a number of things from him. He was not my thesis advisor. I worked with Wallace
Sargent at Caltech on what are called active galaxies, big black holes in the centers of
galaxies that are accreting or swallowing material, a little bit like the stuff of this
year's Nobel Prize in physics 2020. But Feynman I had for two courses. One was general theory of
relativity at the graduate level and one was applications of quantum physics to all kinds
of interesting things. And he had this very intuitive way of looking at things that he tried to
that he tried to bring to his students. And he felt that if you can't explain something in a
reasonably simple way to a non-scientist or at least someone who is versed a little bit with
science but is not a professional scientist, then you probably don't understand it very well yourself
very thoroughly. So that in me made a desire to be able to explain science to the general public.
And I've often found that in explaining things, yeah, there's a certain part that I didn't really
understand myself. That's one reason I like to teach the introductory courses to the lay public
is that I sometimes find that my explanations are lacking in my own mind. So he did that for me.
Is there, if I could just pause for a second. You said he had one of the most intuitive
understandings of nature. If you could break apart what intuitive means, is it on the philosophical
level? No, it's sort of physical. How do you draw a mental picture or a picture on paper of what's
going on? And he's perhaps most famous in this regard for his Feynman diagrams, which in what's
called quantum electrodynamics, a quantum field theory of electricity and magnetism,
what you have are actually an exchange of photons between charged particles. And they might even
be virtual photons if the particles are at rest relative to one another. And there are ways
of doing calculations that are brute force that take pages on pages and pages of calculations.
And Julian Schwinger developed some of the mathematics for that and won the Nobel prize
for it. But Feynman had these diagrams that he made and he had a set of rules of what to do at
the vertex. He'd have two particles coming together and then a particle going out and then
two particles coming out again. And he'd have these rules associated when there were vertices and
when there were particles splitting off from one another and all that. And it looked a little bit
like a bunch of a hodgepodge at first. But to those who learned the rules and understood them,
they saw that you could do these complex calculations in a much simpler way. And indeed,
in some ways, Freeman Dyson had an even better knack for explaining really what quantum electrodynamics
actually was. But I didn't know Freeman Dyson. I knew Feynman. Maybe he did have a more intuitive
view of the world than Feynman did. But of the people I knew Feynman was the most intuitive,
most sort of, is there a picture? Is there a simple way you can understand this? And
in the path that a particle follows even, you can figure out the, you can get the classical path,
at least for a baseball or something like that by using quantum physics if you want.
But in a sense, the baseball sniffs out all possible paths. It goes out to the Andromeda
galaxy and then goes to the to the batter. But the probability of doing that is very, very small,
because tiny little paths next door to any given path cancel out that path. And the ones that all
add together, they are the ones that are more likely to be followed. And this actually ties in
with Fermat's principle of least action and their ideas and optics that go into this as well. And
just sort of beautifully brings everything together. But the particle sniffs out all possible
paths. What a crazy idea. But if you do the mathematics associated with that, it ends up
being actually useful, a useful way of looking at the world.
So you're also, I mean, you're widely acknowledged as, I mean, outside of your science work as
being one of the greatest educators in the world. And Feynman is famous for being that. Is there
something about being a teacher that you well, it's it's very, very rewarding when you have students
who are really into it. And, you know, going back to Feynman at Caltech, I was taking these graduate
courses. And there were two of us, myself and Jeff Richmond, who's now a professor of physics at
University of California, Santa Barbara, who asked lots of questions. And a lot of the Caltech students
are nervous about asking questions. They want to save face. They seem to think that if they ask
a question, their peers might think it's a stupid question. Well, I didn't really care what people
thought and Jeff Richmond didn't either. And we ask all these questions. And in fact, in many cases,
they were quite good questions. And Feynman said, well, the rest of you should be having
questions like this. And I remember one time in particular, when he said, you know, he said to
the rest of the class, why is it always these two? Aren't the rest of you curious about what I'm
saying? Do you really understand it all that well? If so, why aren't you asking the next most logical
question? No, you guys are too scared to ask these questions that these two are asking. So he
actually invited us to lunch a couple of times where just the three of us sat and had lunch with
one of the greatest thinkers of 20th century physics. And so, yeah, he rubbed off on me.
And you encourage questions as well. I encourage questions, you know, and yeah, you know,
definitely. I mean, you know, I encourage questions. I like it when students ask questions,
I tell them that they shouldn't feel shy about asking a question. Probably half the students
in the class would have that same question if they even understood the material enough to
ask that question. Yeah, curiosity is the first step of absolutely of seeing the beauty of something.
So, yeah, and the question is the ultimate form of curiosity. Yeah. Let me ask, what is the meaning
of life? The meaning of life, you know, from a cosmologist's perspective or from a human perspective.
Or from my personal, you know, life is what you make of it really, right? Each of us has to have
our own meaning. And it doesn't have to be, well, I think that in many cases, meaning is to some
degree associated with goals. You set some goals or expectations for yourself, things you want to
accomplish, things you want to do, things you want to experience. And to the degree that you
experience those and do those things, it can give you meaning. You don't have to
change the world the way Newton or Michelangelo or da Vinci did. I mean, people often say,
you changed the world. But look, come on, there's seven and a half, close to eight billion of us
now. Most of us are not going to change the world. And does that mean that most of us are
leading meaningful lives? No, it just has to be something that gives you meaning, that gives you
satisfaction, that gives you a good feeling about what you did. And often, based on human nature,
which can be very good and also very bad, but often it's the things that help others that give us
meaning and a feeling of satisfaction. You taught someone to read. You cared for someone who was
terminally ill. You brought up a nice family. You brought up your kids. You did a good job. You
put your heart and soul into it. You read a lot of books, if that's what you wanted to do, had a
lot of perspectives on life. You traveled the world if that's what you wanted to do. But if some
of these things are not within reach, you're in a socioeconomic position where you can't travel the
world or whatever, you find other forms of meaning. It doesn't have to be some profound,
I'm going to change the world. I'm going to be the one who everyone remembers type thing, right?
Right? In the context of the greatest story ever told, the fact that we came from stars
and now we're two apes asking about the meaning of life, how does that fit together?
How does that make any sense? It does. And this is sort of what I was referring to,
that it's a beautiful universe that allows us to come into creation, right? It's a way that
the universe found of knowing, of understanding itself, because I don't think that inanimate
rocks and stars and black holes and things have any real capability of abstract thoughts and of
learning about the rest of the universe or even their origins. I mean, they're just a pile of
atoms that has no conscience, has no ability to think, has no ability to explore. And we do.
And I'm not saying we're the epitome of all life forever, but at least for life on earth,
so far, the evidence suggests that we are the epitome in terms of the richness of our thoughts,
the degree to which we can explore the universe, do experiments, build machines, understand our
origins. And I just hope that we use science for good, not evil, and that we don't end up
destroying ourselves. I mean, the whales and dolphins are plenty intelligent. They don't ask
abstract questions. They don't read books. But on the other hand, they're not in any
danger of destroying themselves and everything else as well. And so maybe that's a better form
of intelligence. But at least in terms of our ability to explore and make use of our minds,
I mean, to me, it's this. It's this that gives me the potential for meaning, right? The fact
that I can understand and explore. It's kind of fascinating to think that the universe created us
and eventually we've built telescopes to look back at it, to look back at its origins and to
wonder how the heck the thing works. It's magnificent. You didn't have been that way.
Right. And this is one of the multiverse sort of things. You can alter the laws of physics or
even the constants of nature, seemingly inconsequential things like the mass ratio of the proton and
the neutron. You know, wake me up when it's over, right? What could be more boring? But it turns
out you play with things a little bit like the ratio of the mass of the neutron to the proton.
And you generally get boring universes, only hydrogen or only helium or only iron. You don't
even get the rich periodic table, let alone bacteria, paramecia, slugs and humans. Okay.
I'm not even anthropocentrizing this to the degree that I could. Even a rich periodic table
wouldn't be possible if certain constants weren't this way. But they are. And that to me leads to
the idea of a multiverse that the dice were thrown many, many times. And there's this cosmic archipelago
where most of the universes are boring and some might be more interesting. But we are in the rare
breed that's really quite darn interesting. And if there were only one and maybe there is only one,
well, then that's truly amazing. We're lucky. We're lucky. But I actually think there are
lots and lots, just like there are lots of planets. Earth isn't special for any particular reason.
There are lots of planets in our solar system and especially around other stars. And occasionally,
there are going to be ones that are conducive to the development of complexity, culminating in life
as we know it. And that's a beautiful story. I don't think there's a better way to end it. Alex
is a huge honor. One of my favorite conversations I've had in this podcast. Well, thank you so
much for talking. It was fun. Thanks for the honor of having been asked to do this.
Thanks for listening to this conversation with Alex Filipenko. And thank you to our sponsors,
Neuro, the maker of functional sugar-free gum and mints that I used to give my brain a quick
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or connect with me on Twitter at Lex Friedman. And now, let me leave you with some words from
Carl Sagan. The nitrogen in our DNA, the calcium in our teeth, the iron in our blood,
the carbon in our apple pies were made in the interiors of collapsing stars. We are
made of star stuff. Thank you for listening and hope to see you next time.