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 Nobel Prize for physics. Outside of his groundbreaking research, he is a

great science communicator and is one of the most widely admired educators in the world.

I really enjoyed this conversation and am sure Alex will be back again in the future.

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description to get a discount and to support this podcast. As a side note, let me say that as we

talk about in this conversation, the objects that populate the universe are both awe inspiring

and terrifying in their capacity to create and 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.

Well, 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, I mean, 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 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 like the fundamental physics of dark energy? Is there any understanding

of what the heck it is? Or is this the kind of the God of the gaps or the field of the gaps?

So 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 K essence. There's even ideas that,

you know, this isn't something from within this dark energy, but rather there are a bunch of,

say, bubble universes surrounding our universe. And this whole idea of the multiverse is not

some crazy mad men type idea anymore. It's, you know, real card carrying physicists are

seriously considering this possibility of a multiverse. And some types of multiverses could

have, you know, a bunch of bubbles on the outside, which gravitationally act outward on our bubble

because gravity or gravitons, the quantum particle that is thought to carry gravity is

thought to traverse the bulk, the space between these different little bubble membranes and stuff.

And so it's conceivable that these other universes are pulling outward on us.

That's not a favored explanation right now. But really, nothing has been ruled out. No

class of models has been ruled out completely. Certain examples within classes of models have

been ruled out. But in general, I think we still have really a lot to learn about what's causing

this observed acceleration of the expansion of the universe, be it dark energy or some forces

from the outside, or perhaps, you know, I guess it's conceivable that, and sometimes I wake up

in the middle of the night screaming, the dark energy that which causes the acceleration and

dark matter that which causes galaxies and clusters of galaxies to be bound gravitationally,

even though there's not enough visible matter to do so. Maybe these are our 20th and 21st century

Ptolemyic epicycles. So 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.

Yes. 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. It's just that 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. So 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 1500 years. That's so fascinating to think that the philosophical predispositions

that you bring to the table are essential. So 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 as they're more ready for whatever the simpler answer is. Right.

Oh, that's kind of sad. It's sad from an individual descendant of a perspective because

then that means like 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. So then when Kepler in fact showed that the orbits are actually

in general ellipses, not circles, the reason that he needed to cobrar his really great data

to show that distinction was that a slightly off center circle is not much different from

a slightly eccentric ellipse. And so there wasn't much difference between Kepler's view

and Copernicus's view, and Kepler needed the better data to cobrar's data. And so that's

again a great example of science and observations and experiments working together with hypotheses,

and they kind of bounce off each other, 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 before 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, 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?

Yes. 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.

Yes. 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 there are 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.

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.

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 doughnut surrounding the solar system way out there

from which other comets come. And then there's the Oort cloud, WRT 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

nonzero probability, maybe a high probability that there would be a collision?

So 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. That actually

means that all you would need to do is slow it down so it arrives four minutes later or speed it

up so it arrives four minutes earlier and Earth will have moved through one radius in that time.

So it doesn't take much. But you can imagine if a thing is about to hit you, you have to deflect

it 90 degrees or more, right? And you don't have much time to do so. And you have to slow it down

or speed it up a lot 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

try to start an orderly evacuation, perhaps. But you know, that might cause just so much panic

that I'm, how would you do with New York City or Los Angeles or something like that, right?

I might have, I might have a different opinion a year ago. I'm a bit disheartened by, you know,

in the movies, there's always extreme competence from the government.

Competence, yeah. Right. But we expect extreme incompetence, if anything, right?

Yes, no. So I'm quite disappointed. But sort of from a medical perspective, I think

you're saying there, and 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 like

come up with totally new technologies. Like you can imagine actually sending out

like probes out there to be able to sort of almost have 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. A 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, you know,

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,

you know, 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. And fortunately, those are much rare that the

comets come in, you know, 1% of the collisions perhaps are with comets that come in without any

warning hardly. And so, so that might be more like, you know, a billion or two billion years

before one of those hits us. So maybe we have to worry about the sun getting brighter on that

time scale. I mean, there's the possibility that a star will explode near us in the next couple

of billion years. But over the course of the history of life on earth, the estimates are that

maybe only one of the mass extinctions was caused by a star blowing up in particular,

a special kind called a gamma ray burst. And I think it's the Ordovician,

Sulerian, Sulurian, Ordovician, Sulurian 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 or a giant solar flare

that shorts out the grid in all of North America, let's say now, you know, astronomers are monitoring

the sun 24 seven 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,

you know, 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, you know,

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. So it's terrifying to think that people would listen

to this conversation. It's like when you listen to Bill Gates talk about pandemics

in his TED talk a few years ago, 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 super volcano, right? 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, right? It's the nuclear

winter type disaster scenario that some people, including Carl Sagan, talked about decades ago.

But we can see in the history of volcanic eruptions, even more recently in the 19th century,

Tambora and other ones, you look at the record and you see rather large dips in temperature

associated with massive volcanic eruptions. Well, these supervolcanoes, one of which,

by the way, exists under Yellowstone in the central US. I mean, it's not just one or two

states. It's a gigantic region, and there's controversy as to whether it's likely to

blow any time in the next 100,000 years or so. But that would be perhaps not a mass extinction

because you really need to, or perhaps not a complete existential threat because you have to

get rid of 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. I mean,

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.

Recently, I recommend it. It's totally new to me, this kind of survivalist folks,

but there's a lot of shows of those, but I saw one on Netflix and I started watching them.

They make a lot of sense. They reveal to you how dependent we are on all aspects of this

beautiful systems we human have built and how fragile they are.

Incredibly fragile. 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.

You know, we're not cockroaches. We're not going to survive a nuclear war.

So we're kind of this beautiful dance between, we've been talking about astronomy, that astronomy,

the stars, like, inspires everybody. And at the same time, there's this pragmatic

aspect that we're talking about. And so I see space exploration as the same kind of way that it's

reaching out to other planets, reaching out to the stars, this really beautiful idea.

But if you listen to somebody like Elon Musk, he talks about space exploration as very pragmatic.

Like we have to, if we, we have to be, he has this ridiculous way of sounding like an engineer

about it, which is like, it's obvious we need to become a multiplanetary 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.

Sorry, sorry.

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, 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, that's an excuse to not take care of our planet that, well, we say

we're elsewhere, and so we don't have to take good care of our planet. No, you know, we should take

the best possible care of our planet. We should be cognizant of the potential impact of what we're

doing. Nevertheless, it's prudent to have us be elsewhere as well. So in that regard, I actually

agree with Elon. It'd be good to be on Mars. That would be yet another place for us to,

from which to, you know, explore a little further.

Would that be a good next step?

Well, that's the good, it's a good next step. I have to happen,

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, who are going out there and certainly

his success with, you know, the rocket that is reusable because it landed upright and all that.

I mean, you know, 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 time scale 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. You know, 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 know, 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 edge on 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 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, right, 1% is about the fraction of the stars that

have their planetary system oriented the right way. And that already back of the end of all

calculation tells you that of order, 50 to 100% of all stars have planets. 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. 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. So that means the light took

8.7 years to reach us. We're seeing it as it was about nine years ago. So then you ask,

how long would a rocket take to get there at Earth's escape speed, which is 11 kilometers per

second? And it turns out it's about a quarter of a million years. Now, that's 10,000 generations.

Let's say a generation of humans is 25 years, 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, you know, 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. But 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 bring will build machines that are cold inside or philosophers call them zombies.

That naturally the systems that will outcompete us on this earth will be cold and

non conscious, not capable of all the human emotions and empathy and compassion and love

and hate. The beautiful mix of what makes us human. But to me, intelligence requires all of that.

So in order to outcompete 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. Curiosity, inquisitiveness, you know, right?

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 scale short in your own frame of reference. And the amount of energy is just unfathomable,

right? We can do it at the Large Hadron Collider with protons. You know, 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, you know, 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, you know,

Yuri Milner and others are thinking about this, this star shot project where they'll

send a little tiny camera to Alpha Centauri 4.2 light years away. They'll zip past it,

take a picture of the exoplanets that we know orbit that three or more star system and

say hello real, 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 they're 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 you know, ideas of wormholes and ideas at the edge of black holes that reveal to us that

this fabric of space time is could be messed with. Yeah, perhaps is that at all an interesting thing

for you? I mean, in looking out at the universe and studying it as you have, is that also a

possible 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

suggest 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, you know, call me

not very imaginative, but based on today's knowledge of physics, which I realize, you know,

people have gone down that rabbit hole and, you know, 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 farfetched, if not impossible.

So travel through wormholes, for example, you know, it appears that

for a nonrotating 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. Okay. Now, for a rotating black hole, it turns out there is a way to pass

through the event horizon, the boundary of the black hole, and avoid the singularity and go out

the other side or even traverse the donut hole like singularity. In the case of a rotating

black hole, it's a ring singularity. So there's actually two theoretical ways you could get through

a rotating black hole or a charged black hole, not that we expect charged black holes to exist

in nature because they would quickly bring in the opposite charge so as to neutralize themselves.

But rotating black holes, definitely a reality. We now have good evidence for them.

Do they have traversable wormholes? Probably not because it's still the case that

when you go in, you go in with so much energy that it either squeezes the wormhole shut

or you encounter a whole bunch of incoming and outgoing energy that vaporizes you. It's called

the mass inflation instability, and it just sort of vaporizes you. Nevertheless, you know,

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, right? But then the thing that really

bothers me is that as soon as you have this possibility of traversal of a wormhole, you

have to come to grips with a fundamental problem, and that is that you could come back to your

universe at a time prior to your leaving, and you could essentially prevent your grandparents

from ever meeting. This is called the grandfather paradox, right? And if they never met, and if

your parents were never born, and if you were never born, how would you have made the journey

to prevent the history from allowing you to exist, right? 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 you've, 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.

Yeah, there's right. What have you done? It's not like you snap your fingers and say,

okay, let that space there be compressed and then I'll make it over to Alpha Centauri

in the next month. You can't snap your fingers and do that.

Yeah. And but yeah, 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. 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 would,

that's another trajectory that possibly... Well, right. If you could put us into some

sort of suspended animation, 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. 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 knot C squared divided by the square

root of one 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 one, that one over the square root of one 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, 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, I wouldn't, 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. You know, whales and dolphins appear to be reasonably intelligent,

but there's no evidence that they can think abstract thoughts that they're curious about

the world. They certainly can't build machines with which to study the world.

So that's one argument. Secondly, we came about as early hominids only four or five million years

ago and as 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. They're flash bulbs in the night. That brings me to the fourth issue,

and that is the Fermi paradox. If they're common, 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. 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. That's a tiny fraction

of the whole galaxy, a tiny fraction of these 100 billion plus stars. Nevertheless, if the galaxy

were teeming with life, especially intelligent life, you'd expect some of it to have been far

more advanced than ours. There's 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. There could

be civilizations that are billions of years ahead of ours. 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 1,000 or 10,000 years, let alone

a million or 10 million or a billion years. 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. Then you don't have to have tried to detect them beyond

100 or 1,000 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. What if trees? Right. 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. It's conceivable that we haven't detected it and that we're so primitive

compared to them that we're just not able to do so. Like if you look at dark energy, maybe we

call it as a field. It's just that my own feeling is that in science now through observations and

experiments, we've measured so many things and basically we understand a lot of stuff. Fabric

of reality. Yeah. The fabric of reality we understand quite well and there are a few

little things like dark matter and dark energy that may be some sign of some super intelligence,

but I doubt it. Why would some super intelligence be holding clusters of galaxies together?

Why would they be responsible for accelerating the expansion of the universe? 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. 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 observatory.

How the brain works. How did life arise? Yeah, 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. 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. You send a probe to a planet. It makes two copies. They go out.

They make two copies each and it's an exponential. 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. 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. If they bypassed that,

and that may be one of the great filters if there are more than one, then they may not be

a type of creature that feels the need to go and say, oh, there's a nice looking planet and there's

a bunch of ants on it. Let's go squish them and colonize it. No, it could even be the kind of

Star Trek like prime directive where you go and explore worlds, but you don't interfere in any

way, right? And also, we call it exploration as beautiful and everything, but there is underlying

this desire to explore 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 it, like 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 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 are 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 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 cell biologist. But it's the usual

argument. 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 more complex. 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 this 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 or be able to do that.

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 bacteria, you mean,

like defunct civilization of like primitive life.

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, right? 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, right? 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 1000 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 and 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 when 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

no ball 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 no ball prize for figuring out ball lightning.

That was like one of the first sort of sparks of the scientific mindset. Those mysteries,

they capture your imagination. I think when I speak to people that report UFOs,

that's that fire, that's what I see, that excitement.

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.

Yeah. And there's a bunch of them, but he's sort of one of the most legit pilots and people

I've ever met. Right.

The fact that he saw something weird. He doesn't know what the heck it is.

Yeah.

But he saw something weird. I mean, I don't know what to do with that. On the psychological side,

so 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.

So 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. Right.

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 ones. And so it may be that

someone else's 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.

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. And exactly, as you said,

avoid your type of spacecraft. I could see some kind of a dumb thing, almost like a

sensor that's statistically speaking, flying by, maybe lands, maybe there's some kind of robot

type of thingies that just move around and so on, in ways that we don't understand.

But I feel like, 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

an epistomist 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. I meant originally that I'm a pessimist,

I'm a pessimist in that I'm pessimistic about the possibility that there are many,

many of us out there.

Mathematically speaking, in the Drake equation.

Exactly, right. But it may mean a good thing for our ultimate survival. 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 another thing. And astronomers, 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. I get probably,

like, this year, I've probably gotten over, probably maybe, maybe over 1000 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 are always just these large write ups. The problem is, it's very difficult to we

threw a bunch of BS. Right. It's very possible that you had actually saw the UFO, but you have

to acknowledge that by UFO I mean an extraterrestrial life, you have to acknowledge 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. 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? So 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. Speed 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 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 than 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.

It's space itself is expanding. Can we talk about the Big Bang a little bit? Sure. The entirety

of it, the universe, was very small. Right. But it was not a point. It was not a point.

Because if we live in what's called a closed universe now, a sphere or the three dimensional

version of that would be a hypersphere. Then regardless of how far back in time you go,

it was always that topological shape. You can't turn a point suddenly into a shell. It always had

to be a shell. So when people say, well, the universe started out as a point, that's being

kind of flippant, kind of glib. It didn't really. It just started out at a very high density.

And we don't know, actually, whether it was finite or infinite. I think, personally,

that it was finite at the time, but it expanded very, very quickly. Indeed, if it

exponentiated and continued in some places to exponentiate, then it could in fact be infinite

right now. And most cosmologists think that it is infinite. Wait, sorry. What infinite,

which dimension, mass, size? Infinite in space. And 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. Yeah. 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, Alexi Starabinsky and others had similar sorts of ideas. But

in an exponentially expanding universe, if you actually try to make this measurement,

you send light out to try to see it curve back around and hit you in the back of the head,

if it's an exponentially expanding universe, 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

sort of 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 Godlike 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 Godlike 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, you know,

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, you know, that's not really science, because it's not directly testable.

But I would say it's sort of testable. But it's not completely testable. And so it's at the boundary.

But it's not like we're coming up with these crazy ideas, among them quantum fluctuations out of

nothing. And then inflating into a universe with, you might say, well, you created a giant amount

of energy. But in fact, this quantum fluctuation out of nothing, you know, in a quantum way violates

the conservation of energy. But you know, who cares, that was a classical law anyway. And then

an inflating universe maintains whatever energy it had, be it zero or some 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, you know.

But the point is that this is all based on reasonably well tested physics. And although

these extrapolations seem kind of outrageous at first, they're not completely outrageous. They're

within the realm of what we call science already. And maybe some young whippersnapper 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

whippersnappers, Roger Penrose. Yeah. So he kind of has an idea that there may be some

information that travels from whatever the heck happened before the Big Bang.

Yeah. Maybe. I kind of doubt it. So do you think it's possible to detect something, like actually

experimentally be able to detect some, I don't know what it is, radiation, some sort of. Yeah.

And the cosmic microwave background radiation, there may be ways of doing that. Right.

But is it philosophically or practically possible to detect signs that this was before the Big

Bang? Or is it what you said, which is like, everything we observe will, as we currently

understand, will have to be a creation of this particular observable 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. 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, 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. 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, right? 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 it, evidence for it in 1998 with supernovae with

exploding stars, it was great that there were two teams that lent some credibility to the discovery,

but it was not until other astrophysicists used not only that technique, but more importantly,

other independent techniques that had their own potential sources of systematic error or whatever,

but they all came to the same conclusion and that started giving a much more complete picture of

what was going on 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 an 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. 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 was 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, 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? With people. Even then, you'd

expect the universe to be slowing down with time. But we looked back through the history of the

universe by looking at progressively more distant galaxies. And by seeing the evolution

of this expansion rate is that in the first nine billion years, yeah, it was slowing down.

But in the last five billion years, it's been speeding up. So who asked for that, right?

You know, I think it's interesting to talk about a little bit of the human story of the

Nobel Prize, which is, I mean, it's a really, first of all, the prize itself. It's kind of

fascinating in the psychological level that prizes, 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

have accomplished. They do. It's the recognition, the funding, you know. And also inspiration for,

I mean, 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. Is it maxed at three? Yeah. 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 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 on 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, 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 we got to participate in Nobel week. And 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, the Alpha Beta Gamoff 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 one of these people who just 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.

Well, it's also very, so if I were to, it's possible that you're, I mean, I could make a very

good case for you're 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. Yeah. And like, they would, they would start doing like concepts

and almost like the black hole gets the Nobel Prize or, or the 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'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, uh, they recognize the larger team. Yeah, they, they recognize teams. And so in fact,

both teams in the accelerating universe were recognized with the breakthrough prize in 2015.

Nevertheless, the same three people, Reese, Pearl, Mutter and Schmidt 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 feel for them.

I mean, for the gravitational waves, it was a thousand people. What are they going to do?

Invite everyone for the Higgs particle. It was 68,000 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, uh, Anglère 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, um, 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 to separate those, like. Could have and should have. Perhaps he should have

perhaps gotten it with Hawking before Hawking's death, right? The problem was Hawking radiation

had not been detected, but you could argue that Hawking made enough other fundamental

contributions to the theoretical study of black holes and the observed data were already good

enough at the time of before Hawking's death. Okay. 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. But, 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, sunlike stars. But,

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 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. Yeah. And I was on both teams for reasons. I mean, you know, I the style of the first team,

the supernova cosmology project didn't match mine. They came largely from experimental high

energy particle physics, physics, where there's these hierarchical teams and stuff. And it's

hard for the little guy to 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, 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 who are members of the committee of the Swedish National Academy of Sciences.

You know, and I strategically kept, you know, offering them wine and stuff during this long

drawn out Nobel ceremony. Right. And I got them to be pretty talkative. And then in a 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, it's they're not even right. Part of the time. I mean, Jocelyn Bell discovered

pulsars with a radio antennas, a set of radio antennas that her advisor, Anthony Hewish,

conceived and built. So he deserves some credit. But, 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. 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.

You know, it'll conduct this survey large scale survey with the Rubin telescope. So she's been

recognized, but never with the Nobel Prize. And I would say that to her credit, she did not let

that consume her life either. And perhaps it was a bit easier because there had been no

Nobel given for the discovery of dark matter. Whereas in the case of pulsars in Jocelyn Bell,

there was a prize given for the discovery of the freaking pulsars. And she didn't get it.

Well, I mean, what a travesty of justice. So I also think as a fan of fiction, as a fan of stories,

that the the the travesty and the tragedy and the unfairness and the tension of it

is what makes the prize and similar prizes beautiful. The the decisions of other humans

that result in dreams being broken. And, you know, like, that's why we love the Olympics.

There's so many, you know, people, athletes give their whole life for this particular moment.

And then and then there's referee decisions and like little slips of here and there, like the

little misfortunes that destroy entire dreams. And that's it's weird to say, but it feels like

that makes the entirety of it even more special. Yeah, if it was perfect, it wouldn't be interesting.

Well, humans like competition and they like heroes. And unfortunately, it gives the impression to

youngsters today that science is still done by white men with gray beards wearing white lab coats.

And I'm very pleased to see that this year, you know, Andrea Gez, the fourth woman in the history

of the physics prize to have received it. 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, you know, most of the good authors like, you know, Dennis Overby of the New York

Times and others said that these were teams of people and they emphasize that. And, you know,

they all played a role. And, you know, maybe if some grad student hadn't soldered some circuit,

maybe the whole thing wouldn't have worked, you know. But still, you know, Ray Weiss,

Kip Thorne was the theoretical, you know, 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,

you know, the National Science Foundation was going to cut the funding from what I understand,

you know. So there's human drama involved in this whole thing. And the Olympics, yeah, you know,

a runner or a swimmer, a runner, you know, they slip just at the moment that they were taking

off from the first thing and that cost them some fraction of a second. And that's it. They didn't

win, you know. And in that case, I mean, the coaches, the families, which I 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, you know, credit assignment is a fascinating

thing. I mean, that's the full human story. We have, 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 yet another award,

the Turing Award, given for deep learning to three folks who are very much responsible for

the field, but so are a lot of others. And there's a few, there's a, there's a fellow by the name

of Schmidt Hooper, who sort of symbolizes the forgotten folks in the deep learning community.

But, you know, that's the unfortunate sad thing where you remember Isaac Newton,

but remember 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,

wrote many of the words or he's not as well known 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? But 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,

our own son. 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, you know, 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. So, okay, it's like

looking at if you'll let me just give this one analogy, you know, you judge the distance of an

oncoming car at night by looking at how bright its headlights appear to be, 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, you know, with cars, the headlights are all, there's some variation,

there's, 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 one a supernovae.

They come from a weird type of a star called a white dwarf. Our own son will turn into a white

dwarf in about seven billion years. It'll have about half its present mass compressed into a volume,

just the size of earth. So that's an inordinate density. Okay, it's incredibly dense. And the

matter is what's called by quantum physicists degenerate matter, not because it's morally

reprehensible or anything like that. But this is just the main judgments here quantum physicists

give to electrons that are squeezed into a very tight space, the electrons take on a motion

due to Heisenberg uncertain 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. Okay, then 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 Chandrasekhar's scientific work

at a conference in England. And most of us, if we had been Chandrasekhar, 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.

I can ignore your advisors.

Yeah, no matter what your advisor says, right? Or don't always pay attention to your advisor,

right? Don't lose hope if you really think you're onto something. That doesn't mean

never listen to your advisor. They may have sage advice as well. But anyway,

when a white dwarf grows to a certain mass, it becomes unstable. And one of the ways it

can end its life is to go through a thermonuclear runaway. So basically, the carbon nuclei inside

the white dwarf start fusing together to form heavier nuclei. And the energy that those fusion

reactions emit doesn't go into being dissipated out of the star or whatever, or expanding it the way

if you take a blowtorch through 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, you know, through gravity, and you need a big

mass to do that. So this uncontrolled fusion reaction blows up a star that's pretty much the

same in all cases. And you measure it to be almost the same in all cases. But the devil is in the

details. And in fact, we observe them to not be all the same. And theoretically, they might not

be all the same because the rate of the fusion reactions might depend on the amount of trace

heavier elements in the white dwarf. And that could depend on how old it is when it was,

you know, whether it was born billions of years ago, when there weren't 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

relatively... The 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

standardizable 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, and 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. And once you get 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. 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? 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. 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. And 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 this 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, right? Because if those heavy elements remained forever

trapped in the cores of stars, then they would not be available for the production of new stars,

planets, and ultimately life. So indeed, the supernova, my main area of interest, plays a

leading role in this whole story. I saw that you got a chance to call Richard Feynman a mentor of

yours when you were at Caltech. Do you have any fond memories of Feynman, 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 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. If I could just pause for a second. You said he had one of

the most intuitive understandings of nature. What if you could break apart what intuitive means?

Like, is it on the philosophical level? No, 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, you know, 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, he, you know, 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 know, you can figure out the, you can get the classical path, at least,

you know, for a baseball or something like that by using quantum physics if you want.

But, you know, in a sense, the baseball sniffs out all possible 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, 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

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 you 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, 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 seeing the beauty of something. So,

yeah, and the question is the ultimate form of curiosity. 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,

or 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.

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. This is what I was referring to, that it's a beautiful universe that allows us

to come into creation. 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. We do. 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. 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. Maybe that's a better form of intelligence, but at least in terms of our

ability to explore and make use of our minds. To me, it's this that gives me the potential

for meaning. 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. Needn't have been that way.

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. Wake me up when it's over. 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. 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. 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're in the rare

breed that's really quite darn interesting. 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.

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 caffeine boost. Better help, online therapy with

a licensed professional, masterclass, online courses that I enjoy from some of the most amazing

humans in history, and Cash App, the app I use to send money to friends. Please check out these

sponsors in the description to get a discount and to support this podcast. 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 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.