Hunting for Exoplanets

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Hello, I'm Robin Ince, and I'm kind of the Eliza Doolittle of this particular science show on a journey of discovery.

And I'm Brian Cox, and that presumably makes me Henry Higgins, I suppose.

Yeah.

And this is the Invent Monkey Cage coming today from the California Institute of Technology, also known as Caltech in Pasadena.

As regular listeners know, Brian is a proper hard scientist.

He refuses to believe anything unless it has an equation to explain it.

So I am very happy about today's show because I was surprised and delighted when he suggested that we finally investigate poltergeists, despite the fact that he's obviously deeply worried that they break the second law of thermodynamics.

So, this is the first show we're going to do where we're actually going to have a seance.

We're going to have an all-dead panel of scientists.

Do you think it's good?

You've completely misunderstood today's show.

You said we're doing poltergeists.

Yeah, poltergeist, the alternative name of PSR B1257 plus 12C, the first extrasolar planet to be discovered around a pulsar around 30 years ago.

And it's a planet with ghosts on it.

Today, we are looking at the search for exoplanets and our rapidly developing understanding of solar systems around distant suns.

What current instruments, including the Kepler and TRAPPIST telescopes, have discovered, and what we hope to learn with the next generation of telescopes, including the James Webb telescope.

Right, so do I need the Ouija board at all?

Because it was held to get through customs.

Today, we are joined by an astrophysicist, a planetary scientist, a theoretical physicist, and a Rutland-based philosopher who reminded us that our galaxy itself contains 100 billion stars.

It's 100,000 light-years side to side.

It bulges in the middle, 16,000 light-years thick, but out by us, it's just 3,000 light-years wide.

We're 30,000 light-years from the galactic central point.

We go round every 200 million years, and our galaxy itself is one of millions of billions in this amazing, expanding universe.

And they are.

Hi, I'm Jesse Christensen.

I'm the lead scientist at NASA's Exoplanet Archive.

And I think the best thing to come out of Caltech is the men's basketball team.

They have the losingest record in American college sport.

They went 26 years from 1985 to 2011 without a single win.

So if you want a triumphant story over setbacks, throw away your Nobel Prizes, this basketball team played for 26 years without winning and they kept playing.

That is the best thing to come out of Caltech.

That is fantastic.

I love, you know, science is very much about delayed gratification, but I never thought the basketball was as much about delayed gratification.

This extreme example, yeah.

Hi, I'm Tiffany Kataria.

I'm an exoplanet atmospheric scientist based at NASA's Jet Propulsion Laboratory, and my favorite thing to come out of Caltech is actually JPL.

I'm Sean Carroll.

I'm a theoretical physicist and occasional philosopher.

My favorite thing to come out of Caltech is clearly antimatter.

If you lived here in the 1930s and were walking down that street, California Boulevard right there, at night you would hear these big bangs.

And it was an experiment going on the top of the building right there where Carl Anderson was explosively decompressing a cloud chamber to see tracks from cosmic rays.

And one of them looked exactly like an electron, except it moved the wrong way.

in an electromagnetic field.

And he had discovered the positron, the anti-electron.

And he he submitted it to the journal, and they said, clearly, you've just turned your picture upside down.

And he said, no, no, the cosmic rays are definitely coming from the sky.

That's where they come from.

And at one point in the 1930s, Carl Anderson, because he went on to discover the muon and the anti-muon, we only knew about the electron, proton, neutron, positron, muon, and anti-muon.

So he personally on the top of that building had discovered half of the known elementary particles for a little while.

I still think that claiming that antimatter came out of Caltech is a bit bit much.

I mean, it came out of the Big Bang, essentially, didn't it?

No, they don't

even know the same thing it appeared in the universe.

Way too pedantic.

Because basically, we don't have to make this series.

We've wasted 160 episodes when all the answer would have been and came out of the big bang.

Hi, I'm lucky enough to be Eric Idle.

And I'm very happy to be back on the Infinite Monkey Pox.

Caltech, for me, is most famous because it's the place Einstein came in 1931.

And I found this out and I was very intrigued in about 1981 and I began to write a musical called Einstein in Hollywood.

True story, and which one of the lyrics from that became the galaxy song from Monty Python's The Meaning of Life.

And I'd like to point out, Brian, that that lyric has survived far more successfully than your song, Things Can Only Get Better.

Anyway, this is our panel.

I love the fact, Sean, you said you were an occasional philosopher because a true philosopher I think would always define themselves as an occasional philosopher.

There you go, if I'm true as well as occasional.

Yeah, happy to be there.

Yes.

Tiffany, can we start off with a definition?

So, what is an exoplanet?

Sure.

So, simply, an exoplanet is a planet outside of the solar system.

So, not any of our

home cousins here on Mercury, Venus, Earth, Mars, et cetera, but outside of the solar system.

They can orbit other stars.

They can be free-floating just out there in space, and they come in different varieties.

That's interesting.

They can be free-floating.

Because we always think of planets as being attached to or orbiting around stars.

I prefer the other name for them, which is rogue planets.

Yes, they're just

through the galaxy, wherever they want.

They're just traversing out there.

We're trying to look for them.

So what is, so yeah, the rogue planet then, fill us in a little bit more on what a rogue planet is, right?

So a rogue planet, there's really two different ways we think we get rogue planets because most of the ways we think of how planets form are around stars.

So one is the planets when they're forming just get into a big sibling rivalry.

They fight with each other, they interact and one of them just gets kicked out.

out of the nest, you're done, you said something wrong, you're gone.

And so some of the, we actually think in our solar system, we started with five giant planets, and now we only have four.

So that one is probably rogue out there somewhere.

The other way that you can get rogue planets is if you have a quite small cloud of dust and gas that just collapses and just doesn't quite have enough to make a star.

It's a failed star, which is a really pejorative name for it.

But a much better name is a rogue planet.

So it doesn't have enough gravity in the center to start fusion.

So it's just a warm ball of gas.

It's like, well, I'm still here.

How do we know that...

Because it's interesting that you say there were probably five gas giants in our solar system.

So how can we make that statement?

Yeah, so if you look at the arrangement of the planets today, the orbits that they're in, Jupiter, Saturn, Uranus, and Neptune, they are very ordered.

And there was this whole Titus-Bode law about why they're ordered.

And so we think they're ordered because they exchanged energy and momentum

when the planetary system was forming.

And one of the ways you can exchange energy is with a third body.

So we think Saturn and Jupiter switched places.

And they really can only have done that if there was a third body to interact and take some of that energy and get kicked out.

I wanted to have they finished banging into each other.

So Jupiter right now still plays a really big role in shepherding comets and asteroids from the outer solar system to the inner solar system.

There's debate whether Jupiter actually helps us or harms us

on balance.

But yes, there's still a lot of activity.

There's still a lot of stuff flinging about out there.

So let's get back to, in terms of the actual the discovery of the first exoplanet, because this is quite a new science, isn't it?

We're talking about 30 years.

So what was the way that that first exoplanet, Poltergeist, was discovered?

Right.

So, we'd actually been thinking about exoplanets, planets outside our solar system, for thousands of years, and for the last few hundred years had been trying to find them, coming up with new ways and new techniques and new instruments.

So, people had been working really, really, really hard.

So, then it was quite surprising in 1992 when the first exoplanets were found by a bunch of astronomers who didn't care about exoplanets at all.

They were doing something else entirely.

They were measuring pulses from a pulsar.

So, a pulsar is a special kind of star that's rotating thousands of times a second and putting out pulses.

So they were measuring the pulses from this planet.

And what they noticed was sometimes the pulses were coming closer together and sometimes they were coming further apart.

And the only way this worked is if that pulsar was kind of coming towards you and going away from you on a regular basis.

And they realized that, you know, when they looked at the sine waves, there had to be two planets orbiting this pulsar.

So they were like, oh, cool, this is kind of junk, but whatever.

Here, have some exoplanets.

And all of the exoplanet hunters were like, oh, what?

Okay.

So that was 1992.

And so yes, there's now three planets around that pulsar.

They got more data and found a third.

And they are called terrible, terrible garbage names.

I'm really sorry.

PSR, B12, 57, plus 12, little B, little C, and little D.

So sorry.

You know, it's just an amazing, evocative idea of worlds orbiting other suns, and we give them these garbage names.

But there's just, there's more planets than words in the English language.

So this is where we start to run into trouble.

But we did come up with, the IAU, the International Astronomical Union a few years ago, was like, okay, we have to stop this.

These names are terrible.

Let's let the public come up with some names for some of the classic famous planets.

And this original discovery of the planets around this pulsar was, of course, a classic discovery.

So those three planets now have three other names, Drauger, Phobeter, and Poltergeist, which brings us back to this discovery at the start of the show that we are not talking about ghosts, we are talking about exoplanets.

Yeah, we really shouldn't have asked people to name it, should we?

Planety Mac Planet Face would have probably been the...

I'm really surprised I didn't have to put Planety Mac Planet Face in my archive.

Sean, can you give us a sense of the difficulty just to set the scale?

Because we're talking about finding very small objects in a very large galaxy.

Yeah, probably I cannot do much better than say, yeah, it's really hard to do.

These planets, we typically, when we first found them, the first ways of finding them, we didn't even see them, right?

You're either seeing that they're gently tugging on their parent star, so we're actually looking at the motions of the star, and then inferring that there's a planet, or we're seeing the planet go in front of the star and seeing its light diminish.

I was actually an undergraduate astronomy major, and I learned a little bit about the alchemy that goes into being an astronomer.

They get like five data points and they tell you a 3,000-word story about what they have discovered.

Because, oh, the only way to explain these data points is if this star is dribbling this mass onto this thing.

And usually they're right, but it's absolutely astonishing how much you can learn from a really meagre amount of data of faint change in a tiny star very, very far away.

And so, that radial velocity technique, the first one Sean was mentioning, the gravitational tug, that was how 51 Pegasi B, the first exoplanet detected around a sun-like star, was discovered.

It was using that technique.

And as Sean said, it is remarkable to me that we see graphical images of these planets and we say, well, that's going to be a gas giant or that may be a very a super earth a large rocky planet so um well for the first question would be can you give us a sense of that planetary zoo in terms of the different sorts of objects that we've discovered oh yeah so so at 51 pegacy b actually is a really weird one it was a jupiter mass planet orbiting a couple of days around its sun-like star.

So it was what has now been dubbed a hot Jupiter.

It's about ten times closer than Mercury is to our Sun.

And so that was definitely something that was not necessarily predicted by studies of planet occurrence.

I mean, that's a remarkable idea in itself.

So we're talking about something the mass of Jupiter.

But two days, that's the year.

Absolutely.

Yeah, exactly.

Exactly.

It's a two-day year.

Yeah.

And so at that distance, we actually can assume that this planet is what's called tidally locked.

And so it's synchronously rotating such that one side of the planet is constantly facing the star and one side of the planet is constantly facing away from the star.

And so that introduces a lot of interesting

climate and chemistry in that sort of environment.

We're really investigating the extremes with exoplanets.

But we don't observe that.

That's an inference.

Absolutely, yeah.

So models, theoretical models like the ones I use are really critical there for predicting, okay, given this environment, given this architecture,

what their atmosphere might be like, what the chemistry, the temperature, and so on.

Is it possible on a show like this, in a limited amount of time, to describe how we measure or estimate the mass of the planet?

So how fast the star is getting tugged by the planets is directly related to how massive it is.

A massive planet will pull the star more.

Our sun is actually being pulled around the center of our solar system by Jupiter.

Jupiter is about 1% the total mass of the solar system.

So, if you're an alien civilization looking at our sun, you're going to see this 12-year wobble as Jupiter pulls us around.

And the size of the wobble tells you something about the size of the planet.

It's still indirect, but it gives you a minimum mass for how big that must be to create that size wobble.

In terms of interest in distance, I was thinking, I was looking at that image, the most famous image I suppose that came from Voyager for for a lot of people, is pale blue dot.

And for instance, from that distance,

what would, if an alien species was observing us, what would they be able to tell about the planet Earth and what they would expect from it?

It would really depend on the technology they had.

If they had 2022 NASA technology, they would be able to take a transmission spectrum of the atmosphere.

And basically, all of the atoms and molecules in our atmosphere have fingerprints.

They absorb and emit light at different wavelengths.

So

if you looked at this pale blue dot in different wavelengths with a spectrograph, you could see where is it emitting and where is it absorbing.

And that directly relates to what molecules.

So you'd probably see, you know, Pepsi and methane and pollutants and nitrogen and oxygen and the other important things.

But one of the really interesting things is how do we decide when we look at other planets what's going to indicate life, right?

If we see methane on another planet, is it life or is it just geological activity?

Here, it's cow farts.

That's where most of the methane comes from.

It's cows.

But on other planets, there are other reasons that you could have methane.

So there's a really important discussion happening in astrobiology right now.

What would be the smoking gun biosignature?

What would you see in Earth's atmosphere besides methane that would indicate that there was life?

So it's a really big question right now.

So if you were that alien civilization looking at Carl Sagan's pale blue dot, maybe you would be able to see that there was life.

But maybe you wouldn't.

Eric, you were going to.

I was thinking that the search for cows in space was kind of an interesting thing.

I like that idea.

We should have a mission to send off to see if we can find any cows just to be sure that it isn't they're not the cause of the methane really.

I'll do it.

Give me the money.

We were talking about this the zoo planet so you mentioned that the first one to be discovered I suppose that's just because it's easy to discover big ones close to the star right so you see a super Jupiter hot.

Absolutely.

So yeah, I mean the the with the gravitational tug the more massive the planet the bigger the tug and with the transit technique that Sean was talking about earlier there you're monitoring the brightness of the star as a function of time.

So a bigger planet will block more light and a smaller planet will block out less light.

And so yeah, a lot of the first planets we scientists were discovering were

the bigger, the more massive things.

So at the other end of the scale,

in terms of the smallest planets, what are they?

Right.

Actually, one really interesting thing that I'm interested in for my own research is that a lot of the planets that we're finding that are most common, they have sizes between Earth and Neptune.

And so there's really no proxy for that in our own solar system.

So we're kind of like, you know, well, what the heck are these and what are they made of?

How diverse are they?

Those are actually really big questions that we're trying to answer right now and that the James Webb Space Telescope or JWST will hopefully help answer.

And are those planets closer to Neptune?

Are they gaseous planets or are they rocky planets?

They're both.

And so actually, a census of a lot of these planets has shown that they're actually these two distinct populations, what we've called both super-Earths and mini-Neptunes.

And so the super-Earths are probably slightly scaled up Earths that are still rocky.

The mini Neptunes are probably more gaseous like our own Neptune.

But kind of where that bridge happens, how the formation and evolution of these planets fold into those two populations is still very much an open question.

You know, are the super-Earths Neptunes that just lost all their atmosphere and now they're bare rocks, or are they something else?

And Sean, you mentioned that when you started as an undergraduate, we discovered no planets.

Zero planets.

It wasn't my fault.

There were other people who had not discovered planets, also, but yes.

Do you remember the discussions at the time?

Because clearly, when you've only got one observation, so one solar system,

I suppose

we assume that there's nothing special about it.

But in terms of the geography of our solar system, the way the planets are arranged and so on, do you remember how we characterized it in terms of thinking about it as special or common or garden?

Yeah, I think that

we human beings are just not that good at imagining two things.

Number one, things very different than what we're used to.

And number two, just accepting that we don't know, really.

So I think a lot of people thought that

planetary systems outside the solar system would kind of be like the solar system.

There were some people who thought that maybe there just weren't that many.

There was never any reason to think that.

Like, I sort of deny the people who say it was a big surprise when we found all these planets.

You know, we already knew that half the stars in the galaxy are binary stars, right?

They have other stars.

The only star that we were close to has plenty of planets.

It just makes perfect sense that there's plenty of planets.

But having Jupiters very close by was weird.

The very first planet we found was around a pulsar, which was a tiny little neutron star spinning very rapidly.

That was completely unexpected.

We found planets around double stars, like in Star Wars predicted it, and it turned out to, you know, more or less be right.

So I think that, yeah, it's over and over again a lesson that we should be very, very open-minded.

For me, I was interested in how do you do this?

How do you find them?

I mean,

you don't go looking.

These things are already photographed, right?

And you go through files of things that have been already mapped, right?

Is that how you find the exoplanets?

Well that there are nowadays there are a lot of surveys that are their dedicated purpose is to survey stars out in the galaxy.

But at the beginning you found these things, you must have found these things already shot, right?

They were filmed and then you presumably went looking for similar things.

Is that what happens?

Actually, it's very similar to that.

The first evidence for a planet that we know today was a planet is found in hundred-year-old photographic plates from Carnegie Observatory.

They had taken a spectrum of a white dwarf, which is what's going to happen to our Sun when it runs out of hydrogen and helium and puffs off all its outer layers.

The central core of carbon and oxygen will just be a white dwarf that cools forever.

And they had the spectrum on this little photographic plate at Carnegie Observatories.

And what they see in the spectrum is pollution by heavy elements.

And they shouldn't just sit on the surface of the white dwarf.

They should sink down.

So what they now know this is evidence of is that this white dwarf just ate a planet for lunch, just was like, yep, I'll have you, and then destroyed it and what we see is the remnants of this planet so the first planetary evidence is actually in a photographic plate that we came back to 100 years later and was like oh there it was the whole time solar indigestion yeah exactly that's quite the burp how many have we got how many have we found over 5 000 discovered exoplanets that was actually just the milestone we reached what about a month ago march yeah march or two months ago do you get to because obviously like in in in show business if there's a say someone who always storms it and seems to get all the good movies people get very bitter are there certain astrophysicists they go, that lucky bastard?

How come he's always noticing the exoplanets?

I mean, we're pretty hot field, I will say.

So, you know, there's lots of folks that want to get in our game.

But, you know, there's so much to do in exoplanet science now.

You know, it's not just looking for planets.

It's, you know, we've started to actually detect their atmospheres.

And so understanding, you know, what they're composed of, you know, looking at the variety of planets that are out there, and also now conducting surveys of those atmospheres themselves, not just looking for the 5,000 planets, but actually starting to say, okay, as a population,

what are mini-Neptunes like?

What are super-Earths like?

And so we're not just stamp collecting, as it's often called.

We're actually looking at exoplanets as a population and how that compares to our solar system planets.

So do you want to

whether you regret now, you said, you know, you started off in astronomy, as we've heard, you left that, it's actually the hot field now you're still mainly in a kind of quantum world aren't you you know do you have regrets no I'm pretty sure had I stayed in astronomy they would not have found any exoplanets by now so I think we can all agree it was the right choice but there's different techniques like in particle physics which I which I've done for a while back in the heyday of the 70s and 80s there was this famous particle physicist who his technique was he was very good at finding new particles but what he would do was basically spread the rumor that he had already detected whatever the particle they were expecting to detect next was And then he'd say, oh, yes, we're just writing up the results, cleaning up the data, and then he would go look for it.

And sometimes this worked, and he won the Nobel Prize.

I was going to say, Sean, what would be the golden discovery for you if you think, well, a very, very exciting observation in the atmosphere of an exoplanet?

What would be the top of your wish list?

Yeah, little aliens saying hi.

That would be great.

I mean, that would be the best.

But, you know, as Jesse already said.

But we're the only picture of that in the model.

We don't even know what we're looking for.

I mean,

if we were not humble enough when it came to imagining the different kinds of planets, we're nowhere near humble enough when imagining the kinds of life that might be out there.

I mean, planets are great.

Don't get me wrong.

Love planets, love stars, but life would be pretty awesome, right?

And we don't know what we're looking for.

One very, very simple idea is just that really, really long molecules don't get created by non-living processes in the universe.

So even without knowing what the molecules are, are, just looking for sufficiently complicated molecules is one thing to look for.

But that's one of many, many proposals on the table, and we just don't know.

What would be the best?

I love that little alien saying hi.

I love that idea that there's a bunch of scientists looking at all the spectroscopy and all that kind of thing.

They go, have you seen just behind that, there's just a little lizard-headed man going, hi, yeah,

there's a thing waving.

Yeah,

holding a sign.

We love Monty Python.

But this is actually an important point because we're puzzled as to why we haven't found other advanced civilizations yet.

And when you look at a lot of purported explanations for why that is, they're shy, they're trying to hide, they kind of don't hold up to me because I don't see why they wouldn't say hi.

And I hate to be a downer, but I think that probably the easiest explanation is that they don't exist.

Yeah.

Downer, yeah.

Well, they don't exist.

They don't exist close to us yet.

I mean, that's the point.

It doesn't mean they don't exist.

Well, don't forget our sun has only been round the Milky Way 22 times.

Yes, but

it's a entire lifetime.

Once every 22 years.

It's not that big.

Say what?

The Milky Way is actually not that big.

Now we say that.

100,000 side-side.

It's like after your date, you know, it wasn't that big.

Anyway.

Let me just check that figure with Eric's lyrics.

100,000 light years side to side, correct.

Carry on.

Is that correct?

I think you're right.

Is it correct?

Isn't the galaxy sun?

100,000 light years ago.

See, I'm just wondering, though, because the names of the exoplanets are very similar to the names of trolls on Twitter.

Because they're normally called...

So are they actually not bots after all?

They are sentient life from exoplanets.

And it just turns out they're just very rude.

You said that, though, the Milky Way is not that big.

Yeah, you have to compare space and time, right?

The Milky Way is big, you know, compared to, like, Los Angeles, it's big.

But in the lifetime of the galaxy, right, over 10 billion years, there's plenty of time for life to arise, flourish, discover technology, and travel back and forth across the galaxy many, many times.

And all it takes is one of those civilizations to realize we don't even need to travel.

Travel is boring.

We can send robots that will duplicate themselves and fill the galaxy.

And this could easily have happened a billion years ago, and it hasn't yet.

Yeah.

Jesse, in your study of exoplanetary systems, is there anything in there as we look at this zoo we've discovered of solar systems that might suggest that there is something unusual about ours, particularly with reference to the fact that a civilization exists in it.

Well, yes, we're the only one with a civilization, so it's pretty special so far.

So, you know, we've talked a little bit about the fact that before we knew about planets, we tried to think what they might look like.

And people came up with theories of planet formation that tried to recreate the solar system.

And if your theory didn't recreate the solar system, you threw it out because it was wrong, because we knew what the solar system looked like.

And now that we're discovering all of these planets, what we're finding is this incredible variety in the configurations and types of planets and how they are around their star.

So it's great for theorists, job security, throw that textbook out and write a new one.

But what it means for us is really interesting.

So for instance, I mentioned before, we don't know whether Jupiter is a net good or bad for Earth, for life on Earth.

So Jupiter played a role in shepherding many comets from the outer solar system to Earth in the early solar system, which delivered almost all of our water.

Our water was brought here by Jupiter.

And then Jupiter just started flinging things at us, which was bad, like the dinosaurs died.

So is Jupiter a good or bad?

Do we need Jupiter for life to arise on Earth?

Is the moon good or bad?

The fact that we have a moon, which is kind of an accident, we think something came along about Mars' size, hit the Earth, threw off a bunch of material, it coalesced together to become the moon.

Is the fact that we have a moon important for life?

Because we think that life might have started in tide pools, which are sometimes wet and sometimes dry.

So you have this chance to build these long molecules that Sean was talking about, which are soluble in water.

That's why you need cells to hold them together.

So do we need a moon for life?

How important is a moon for life?

It's a rabbit hole.

It's so hard to know how far down the rabbit hole of how special are we.

So when we look at other solar systems, you know, as Tiffany's saying, there's just so many different kinds of things we're seeing and Sean's talking about imagination.

It's so open.

It's such an open question.

There's so much in the galaxy and I hope there's life out there because otherwise, how boring would that be if this was the only time it ever happened?

Well, at least you've given us the title for the show now, because we've never either Jupiter, Good or Evil, or Are there rabbits on the moon it's one or the other both of those will be on the history channel about 10 p.m.

most nights

have we seen any solar systems that are even remotely close to ours in the arrangement of the planets and the star we haven't yet but that's more of a selection effect than we think a true natural phenomenon so these surveys that have been looking for exoplanets have been going for a while now but we've only just really started to get sensitive to the outer solar systems of these stars we've found all of the close in planets i shouldn't say all we found many of the close in planets out to something like the orbit of Earth.

And we have found some giant planets further out, but we're just not sensitive to our own solar system yet around other stars, just given the arrangement of things.

So it's partly due to our instruments that we found all these weird and wonderful things, because that's what we're sensitive to.

So we haven't found our solar system yet.

And in fact,

we think we might be less common because when you look at other stars, what you see are patterns, and patterns that we don't seem to have here.

So

planets of all the same same size, many stars just have all giants or all rocky planets or all super-Earths.

Or they have this like regular spacing, like even more regular and close than our solar system.

So there's a lot of questions now about the theory.

You know, how do you create these regular patterns of planets and why don't we have that?

What happened to us?

Can I just ask you a question?

Because I think the interesting thing is that

we assume that life, and then we define it and say there's intelligent life.

But I don't think there is a difference.

I think there's only life.

And it's like space-time.

We'll find out that that the same thing, that if you give enough time to enough shrimps or enough dinosaurs, they will evolve into intelligent people.

Not people, but they will into intelligent forms.

It seems to me.

Yeah, I think the idea is, you know, the amount of time it takes to get there from the little shrimps to the walking, talking people.

And so, you know, the thought is perhaps that there are a lot more of those shrimps out there than perhaps the walking-talking people.

My point is there's no

difference between life in the shrimp and life in the person who's lecturing us.

It's the same thing.

They come from the same background.

They're connected when life first appeared on the Earth, what, 4.5 billion years ago.

We're all connected in that moment to everything on this planet.

Yeah, it's definitely all connected, but I think it does shape the way you look for life out there.

You know, the little shrimps, the way in which you detect the little shrimps are maybe different than the detecting advanced intelligence.

We'll be very happy when we find them on some kind of Jupiter, you know, underneath the seas there.

We'll find life, won't we?

We know we're going to find life.

How could it not be?

If we've got life after 4.5.

Don't do that.

I'm allowed to do that.

I'm a writer.

I can lie.

I can tell lies.

Writer.

Well, and it's also what we hope to find.

Like little shrimps will be exciting, but we can't really talk to them or learn from them or exchange information.

We could eat them and, you know, make sure that.

And the French will be happy.

Yes.

There will be people with alien allergies.

They'll won't be able to go to the alien restaurants.

Yes.

So, you know,

one of the thoughts is that on Earth, almost as soon as the surface of Earth was able to support simple life, you see evidence of simple life.

Single-celled life seems to appear very quickly.

But then it's billions of years before that suddenly becomes multi-celled life, and then that explodes into this whole, all of these trees we see today.

So, you know, it's hard to do the statistics with one, but maybe the inference there is it's easy to make simple life, which is hard to find, and very hard to make complicated life, which might be more easy to find.

So we're kind of stuck in the middle of those two options.

Yeah, that might be the difference, mightn't it?

It's between single-celled and shrimp that the problem comes.

Shrimp to astronomer, not a big leaf.

Right.

Shrimp to astronomer is very, very close to it.

There's actually a philosophical point related to what Robin was saying, and also Eric, which is that we do start trying to be humble, right?

We say, like, oh yeah, you know, nothing special about us.

And then, but the problem is, when you say we are humble, we're typical, like, nothing especially weird about us in the universe.

Secretly, what you're saying is that everywhere else in the universe is just like us.

And that's not really humble at all.

The really humble thing is to say, we don't know.

Maybe there's no life anywhere.

Maybe there's a whole bunch of single-celled life everywhere.

Maybe there's a whole bunch of civilizations so advanced we don't even notice them.

I think that all those options need to be explored.

And that's having said all that, what's your guess?

If I was to force you to guess about the number of civilizations in a galaxy like the Milky Way, yeah, zero.

Yeah,

I agree, actually.

If we didn't have any data, I would say lots, but we have some data, and we haven't seen any, and that vastly lowers the number.

Tiffany,

what do we know about the stability of solar systems?

If I said to you, given that

we think most stars out there have planetary systems around them, but also if we said as Sean said the observation we have here is what three and a half to four billion years to go from the origin of life to a civilization what would be your feeling if I said that's the constraint so in order to look for civilizations we need planetary systems that have had stable planets in them and stable stars for something like four billion years

I mean that's actually what's I'd say typically done now.

You know, you try and look at old systems because you do try and make the assumption that, okay, all the, you know, crazy stuff already happened, and so we can kind of be confident that this planet is going to stay a planet in this orbital configuration.

But in terms of the search for life, one thing that Sean reminded me of is not only

so much of the paradigm for the search for life has been around sun-like stars.

We should look for Earth-sized planets around Sun-like stars, full stop.

And there are people that really ascribe to that idea, and that is their full stop.

Whereas I think we should be looking at all sorts of stars, all sorts of planets.

There are these M dwarf stars, these red dwarfs, as they might be called, and they're about half as cool as our sun, but they're very active.

Our sun has a lot of flaring, but M dwarfs is just these crazy, crazy activity that occurs.

And so the ongoing theory is that, okay, if an Earth-sized planet is in the habitable zone or Goldilocks zone of this star, that it's probably been stripped of its atmosphere.

probably doesn't have life there.

And so, you know, my counter is always, well, let's go look.

Let's answer that question confidently.

And so, that's a question I think that JWST will lend a lot of insight to.

Yeah, I wanted to talk about that actually, coming towards the end.

But the Webb telescope is going to be a shift, isn't it?

Oh, absolutely.

We're salivating, waiting for data to start coming down.

What is it able to do?

The James Webb Space Telescope, or JWST, is a telescope that was launched on Christmas Day after much delay, which is very much an understatement.

It's been a long time coming.

And so its role is really to provide sensitivity to detect, well, among many things, the thing I'm most interested about, exoplanet atmospheres, but at much longer wavelengths than we've been able to detect thus far.

So the Hubble Space Telescope, which is what I was talking about earlier,

we've discovered water in the atmospheres of, say, hot Jupiters, but our knowledge of what's in the atmosphere kind of stops there, and that's really a boundary of what wavelengths that the Hubble Space Telescope can can cover.

And so the James Webb Space Telescope covers much longer wavelengths than we've been able to probe since really the days of Spitzer, but a much higher sensitivity that we can start to access more molecules for exoplanet atmospheres, say.

And so that will give us even more information, more context about what these environments might be like.

And so in the case of these M dwarf planets that might be in their Goldilocks zones, we'll be able to say things like, okay, well, maybe there's evidence of clouds or maybe there's evidence of some other really exotic molecule that we didn't expect to see and that will tell us something more about you know whether or not life could exist there.

Are we on the edge, Jesse, of being able to really paint a detailed picture of any of these planets, particularly with the JWST data?

Is that going to really help us?

So you see these artists' impressions of the planets and you can see oceans on them and continents and things.

How close are we to being able to characterize them with that level of detail?

So there are some hot Jupiters where Hubble's done an excellent job.

So HD 189733 that Tiffany mentioned before, where we've been able to look at the winds, you know, I really love it because we know how fast the wind is moving and we know the molecules in the wind and we know the temperature of the wind.

And all of that put together means we know that on HD 189733B, it's raining liquid glass sideways constantly.

That's just what we know about it.

So that's been accessible for gas giants.

Now we can do it with web for rocky planets.

And that's why we're excited, right?

Because we haven't been able to do this for rocky planets before, to like start to map out surfaces and atmospheres and stuff.

So it really will, you know, it's ten times the collecting area at a really stable orbit quite far away from Earth, whereas Hubble's in this little low-Earth orbit.

So it's going to revolutionize exoplanet characterization the way Kepler revolutionized exoplanet discovery.

It's just going to be so much better data than we've ever seen before.

And I'm so excited by the questions we'll be able to answer with it.

I just wanted to give you the opportunity to talk about some of these worlds, because that picture, a planet with horizontal rainstorms of glass you know

is this one that rains diamonds where's that that's in our solar system

so there's um 55 Cancri E is a lava world around a star called 55 Cancri and it has this carbon to oxygen ratio that was measured where and it's under such pressure if you take carbon and you put it under a lot of pressure for the headlines were like move over Tiffany's diamond planet found that was a great one 55 it's a lava world so it's a super super-Earth.

It's a rocky planet that's so close to its star that it's thousands of degrees.

And it's just like a blob of magma floating around.

And so that's actually one planet that will be observed with JWST.

And so the hope there is that you can maybe start to detect signatures of rock that may say, okay, this really is a lot, you know, magma ocean planet.

I like the idea that if it were raining molten glass vertically, you'd be like, yeah, no big deal.

But if it's horizontal molten glass,

okay, I want to visit there.

It's just we live in, we it just, uh, what strikes me is we live in an astonishing universe.

And the moment you get a new instrument and make some new observations,

your idea of what a planet can be is transformed.

I mean, it's a lesson that scientists should always learn.

The space of possibilities is way bigger than the space of stuff we imagine.

And so turn on new instruments of the universe and we always get surprised.

Also, any universe is going to be astonishing if there's things in it which can be astonished by it.

If you see what I mean, from that moment.

That brings us back to the rarity of our civilization.

I wanted to ask what your ideal planet would would be.

I've been waiting to ask that for a while.

Yeah, I just wanted to ask you, you know, we've heard of these magical worlds.

What's the perfect planet other than Earth?

You can't say Earth.

I'd like it to rain tea.

A very British planet, don't you think?

Yeah.

People keep their socks on during sex and

watch a lot of cricket.

I think that's probably the planet I like.

I like playing cricket and getting rained on tea.

To be clear, hot tea or iced tea.

Depends what you know, depends summer or winter, really.

So So it rains tea, and yet conditions are okay to play cricket.

Not in the rain.

You can play cricket in the industry.

You could never get the covers on it.

Well, that's true.

You could have to play indoors, really, I suppose.

I think it's fair to say that America hasn't changed you that much, really.

We've asked our audience a question as well, and obviously because it's Caltech, that's a very, very high caliber of answer.

We asked our audience, what is the one thing that they would like to find on an exoplanet?

The meaning of life.

Because the life of Brian did not quite do the job.

The life of Brian wasn't trying to do the bloody job.

The meaning of life was trying to do the job.

Please pay attention.

Mine says the Spanish Inquisition.

That's from Kevin.

Thank you, Kevin.

That's what he wants to find on an exoplanet.

Well, we can't go looking for that because no one expects it.

So you just have to find it, somewhere surprised.

There you go.

This

from Scott, a print of the Holy Grail, because then I would know the inhabitants have good taste and a sense of humour.

Very good, yes.

I think we're finding out who the main drawer was for today's show.

Complete enlightenment or a soft serve ice cream machine.

We actually talked earlier about the Python zone in the Milky Way, which is Python's been transmitted out as radio waves for about 50 years.

And so, how many planets are in the Python zone that could have actually, in principle, given the restriction of the speed of light?

Give me like three seconds, 50 light years, which is about 15 parsecs, and there's a few hundred stars.

They probably all have planets, so like 500?

500 planets have heard Monty Python at this point.

Is that why the aliens aren't visiting?

Are you the reason?

Is it your fault, the Fermi paradox, Eric Heigel?

But I don't want to sit on that face

anyway.

Everybody's a critic.

Every bloody exoplanet immediately.

You're in LA.

Of course everyone's a critic if they're not an actor.

Thank you very much, everyone.

Thank you very much to our amazing panel who are Jesse Christensen, Tiffany Katara, Sean Carroll and Eric Idle.

And Eric.

I hope you've realised we might be the artists on the panel, but the one thing that brings artists and scientists together are puns.

I don't know if you notice the mouse mat.

Here we go, which has an Einstein equation, a Newton equation, and it has written on it, don't drink and derive.

Yeah, so the pun survives in whichever one of the cultures you're in.

So, thank you very much for joining us.

We'll see you again next time.

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