Speaker 1: Hey, Daniel, what do you think will happen the day
Speaker 1: we discover alien life? Oh? I'm imagining like a huge
Speaker 1: worldwide celebration. Oh yeah, and you think it'll be good news. Yeah,
Speaker 1: I think we'll learn something very deep and important about
Speaker 1: the nature of life and the universe and everything. But
Speaker 1: what if it's not good news? What do you considered
Speaker 1: darker possibilities about alien life? Like if they're not friendly
Speaker 1: to humans they show up in space and zappaus, Well,
Speaker 1: they could be friendly to humans. You know, they might
Speaker 1: find us delicious. I guess that depends on which kind
Speaker 1: of humans they find delicious. We probably all taste the same,
Speaker 1: you know, like chicken. Maybe chickens taste like humans. I'm
Speaker 1: sure there are people in this world who know the
Speaker 1: answer to that question. What if we find out about
Speaker 1: aliens because of some giant space battle they're having with themselves.
Speaker 1: Oh well, that sounds pretty exciting. In that case, I'd
Speaker 1: like to reserve a front row seat. Well really, Oh
Speaker 1: you do that, I'll be running away in the other direction,
Speaker 1: and I'll be popping the popcorn. Hi, am Orham and
Speaker 1: cartoonists and the creator of PhD comments. Hi, I'm Daniel
Speaker 1: I'm a particle physicist and a professor at UC Irvine,
Speaker 1: and I don't wish any aliens to die, but I
Speaker 1: do want to see a giant alien space battle. Wait,
Speaker 1: so how would they have a battle but without any
Speaker 1: even dying. Isn't just like a virtual battle or they're
Speaker 1: like plane laser tag? What are you talking about here?
Speaker 1: I mean it's like a wortal battle. Are they having
Speaker 1: a wortal battle? Maybe they've evolved to a higher plane
Speaker 1: of combat exactly. No, it's tension within me. As much
Speaker 1: as I would like to see alien space battles, I
Speaker 1: also don't want any aliens out there to die. But
Speaker 1: you know some of our favorite stories are about alien
Speaker 1: space battles. Isn't that what Star Wars is all about.
Speaker 1: Star Wars is about aliens. That's what you told me.
Speaker 1: It's in another galaxy, far far away, right, they're all aliens.
Speaker 1: Maybe we're the aliens in the Star Wars universe. Well,
Speaker 1: we're not capable of putting on giant space battles yet. Also,
Speaker 1: people don't die in Star Wars. They just come back
Speaker 1: as ghosts, Jedi ghosts more powerful than you could even imagine,
Speaker 1: Or do you the Emperor did they just keep bringing
Speaker 1: you back for all the movies. Don't the Stormtrooper die though,
Speaker 1: or do they also come back as Jedi ghosts. I
Speaker 1: guess it's not clear. You know, they get zapped with
Speaker 1: their little armor and they just fall down. Maybe they're
Speaker 1: just taking a nap. There you go. I'd like a
Speaker 1: giant alien space battle where the losers just take a nap. Yeah,
Speaker 1: I want to see that movie. Star naps were Welcome
Speaker 1: to our podcast Daniel and Jorge Explain the Universe, a
Speaker 1: production of iHeartRadio, in which we try to zap your
Speaker 1: brain with all sorts of incredible information about the universe.
Speaker 1: We know that everything out there is amazing and mysterious
Speaker 1: and confusing, but we hope to help you understand what
Speaker 1: little of it human entity has managed to decode. And
Speaker 1: we hope that one day aliens come and give us
Speaker 1: a little bit more information about what's going on out
Speaker 1: there in the universe, if indeed they do exist. That's right,
Speaker 1: because it is a pretty incredible universe, and we do
Speaker 1: battle every day here with the mysteries of it, and
Speaker 1: we go to war with our ignorance about how it
Speaker 1: works and what's going on in the universe. We're trying
Speaker 1: to drop a knowledge bomb on everybody's ignorance. That's right.
Speaker 1: You can think of us as a laser gun of
Speaker 1: amazing facts zapping people's brains. There's that warm, fuzzy feeling
Speaker 1: you get when you understand something about the universe. But
Speaker 1: there's also lots of things that we still don't understand
Speaker 1: about the universe, things that give you that gnawing feeling
Speaker 1: of desperate curiosity, that desire to just know what's going
Speaker 1: on out there. There's some of the deepest questions in
Speaker 1: human existence which have answers, which are facts about the
Speaker 1: universe which maybe one day people will know. How frustrating
Speaker 1: is it to live in the era of dark to
Speaker 1: not know the answers to basic questions like are we
Speaker 1: alone in the universe? Yeah? What bigger question can there
Speaker 1: be about the existence of humans than the question of
Speaker 1: whether we are the only living thing or intelligent thing
Speaker 1: living and existing in this universe? And we wonder about it,
Speaker 1: we speculate about it, but we have a very very
Speaker 1: deep lack of information about it. The universe is vast,
Speaker 1: and from our tiny little rock we have done a
Speaker 1: pretty good job of exploring a tiny, little corner of it.
Speaker 1: We have telescopes to tell us about nearby star systems
Speaker 1: and compeer further and deeper into the universe, but we've
Speaker 1: only begun recently to identify other planets and other places
Speaker 1: in the universe where life might spring independently from Earth. Yeah,
Speaker 1: we know that here in our Solar systems there aren't
Speaker 1: on at the signs of life, and so we know
Speaker 1: that if there is alien life out there, it has
Speaker 1: to be kind of far away. Right, how close is
Speaker 1: the nearest planet to us light years away? The nearest
Speaker 1: planet to me is about zero meters away. It's right
Speaker 1: here under my feet. There are other places in the
Speaker 1: Solar System people think there might be life, like under
Speaker 1: the frozen crust of Europa. So there are still exciting
Speaker 1: places in our backyard. But you're right, other Solar systems
Speaker 1: are frustratingly far away, several light years. The closest identified
Speaker 1: exoplanets around Proxima Centauri, which happens to be their closest star,
Speaker 1: just under four light years away. And what that tells
Speaker 1: us is that there are planets everywhere in the galaxy
Speaker 1: and in the universe. We now think that almost every
Speaker 1: star out there has planets around it, and a huge
Speaker 1: fraction of them have even earthlike planets, maybe around this size,
Speaker 1: maybe around this kind of surface temperature, maybe even with
Speaker 1: liquid water on their surface. And so with so many
Speaker 1: places that life could be out there in the universe,
Speaker 1: sometimes we wonder, why haven't we found it already. Yeah,
Speaker 1: it's a very big question, one that would kind of
Speaker 1: determine our place in the universe. Because if the answer
Speaker 1: is that there isn't life out there, that is that
Speaker 1: humans are pretty special right in the entire universe. Imagine
Speaker 1: what it'd be like to know that we're the only
Speaker 1: intelligence species in such a big place. Yeah, it would
Speaker 1: make you feel special. It'll also make you feel kind
Speaker 1: of lonely being the only intelligent life in the entire universe.
Speaker 1: It's kind of a lot of responsibility also, like we're
Speaker 1: the only ones out there doing anythinking. We're the only
Speaker 1: ones trying to figure out this huge puzzle about the
Speaker 1: nature of the universe, trying to crack the cosmic mystery
Speaker 1: of how all these quantum particles weave themselves together into
Speaker 1: this experience. I prefer to imagine that there's lots of
Speaker 1: other civilizations out there, and maybe they've even solved some
Speaker 1: of these questions and have the answers waiting for us.
Speaker 1: But we don't know. And we've been looking out in
Speaker 1: the cosmos and listening for signals from aliens, hoping that
Speaker 1: they are as excited as we are to meet their neighbors,
Speaker 1: and sending us messages which we might capture in radio
Speaker 1: waves or other electromagnetic signals. Of course, so far we've
Speaker 1: heard nothing conclusive. Wait, so you want aliens to exist
Speaker 1: just to take some of the pressure off of your job.
Speaker 1: Is that kind of what you're you're talking about? You know,
Speaker 1: I'm very strongly believe in funding basic research and expanding science,
Speaker 1: and that goes beyond the limits of our species. I
Speaker 1: think science should be funded here on Earth and everywhere
Speaker 1: in the universe, and I hope that budget aliens out
Speaker 1: there are, you know, giving a healthy dose of funding
Speaker 1: to those science aliens out there struggling to understand the
Speaker 1: nature of the universe, burned by the same curiosity that
Speaker 1: we have. Or maybe they don't. Maybe they just don't
Speaker 1: care about the nature of the universe and they're not
Speaker 1: even doing science. I feel like you're like little kid
Speaker 1: in class who's looking at his test or her tests
Speaker 1: and going like, I have no idea what's going on,
Speaker 1: and you're sort of like looking around to see if
Speaker 1: anyone else knows the answers. Yes, I definitely want to
Speaker 1: cheat off of alien physicists. I would love to get
Speaker 1: like an alien physics textbook and then win like a
Speaker 1: whole string of Nobel prizes here on Earth just by
Speaker 1: copying their ideas. Yes, I will completely admit that is
Speaker 1: my fantasy. Really, So wait, you would get the secrets
Speaker 1: from the alien I'm just trying to figure this scenario.
Speaker 1: Let's work through it. You would get the secrets from
Speaker 1: the aliens, but you wouldn't tell anyone that aliens exist,
Speaker 1: and you would use that knowledge for your own personal game.
Speaker 1: That sounds fantastic. Yes, remind me not to tell you
Speaker 1: any secrets. Then, If you are holding a Nobel prize
Speaker 1: winning secret, please do share it with me. I would
Speaker 1: love to hear it. You would be the last person
Speaker 1: I would share with, obviously. I hope you would share
Speaker 1: it with all of humanity, Like if somebody gave me
Speaker 1: secrets from aliens, I would share it with all of
Speaker 1: humanity absolutely, But the aliens themselves would be the biggest secrets.
Speaker 1: I just said it's the biggest question in human existence. No,
Speaker 1: you're right, And of course, if aliens do come or
Speaker 1: communicate with us, probably physicists wouldn't be at the front
Speaker 1: of the line of people who get to chat with them, right,
Speaker 1: probably would send like engineers or doctors, or politicians or
Speaker 1: linguists or mathematicians or philosophers before the physicists even get
Speaker 1: their shot. I think I would send the physicists first
Speaker 1: for sure. Yeah, because you know what, if they're hungry,
Speaker 1: we got to test the waters here. So you don't
Speaker 1: want me to learn the secrets from the aliens, but
Speaker 1: you do want me to be there first. I mean,
Speaker 1: there's two sides to that coin. Well, I want you
Speaker 1: to learn the secrets, but I want you to share
Speaker 1: the secrets verybody. I will share the secrets with you
Speaker 1: and the Nobel Committee. And if their secret is what
Speaker 1: their stomachs look like, well, you know you can't share it,
Speaker 1: but at least we would know. Just like going inside
Speaker 1: a black hole, you learn some deep secrets about the universe,
Speaker 1: but only you can know them. But it's interesting you
Speaker 1: talk about some of the ways that people usually think
Speaker 1: that we're gonna meet aliens or know about aliens, which
Speaker 1: is getting signals from them. I mean that's sort of
Speaker 1: like one way we can learn about them. I guess
Speaker 1: another way is to go to another planet and see
Speaker 1: them too, right, Yeah, And this is a really common
Speaker 1: thing in science. When you have no idea how hard
Speaker 1: a problem is, you start with the easiest things, like
Speaker 1: maybe the universe is filled with aliens and they're all
Speaker 1: sending messages and we just haven't been listening, and as
Speaker 1: soon as we turn on our electronic ears and use
Speaker 1: our radio satellites to tune in, maybe we could instantly
Speaker 1: tap into the galactic internet and hear all those conversations.
Speaker 1: There's some scenario in which it would have been easy,
Speaker 1: and as soon as we started listening, we discovered it.
Speaker 1: So it makes sense to first do the easy thing
Speaker 1: and see if alien messages our feeling space. Of course,
Speaker 1: we've been listening and we haven't heard anything, and so
Speaker 1: people are starting to try to be creative and think about, like, well,
Speaker 1: what are other ways we could hear from aliens, or
Speaker 1: what are other ways we could detect their existence? As
Speaker 1: you say, maybe we could go to those planets and
Speaker 1: discover them. Right. That's limited, of course, by our ability
Speaker 1: to travel from star to star. These stars are so
Speaker 1: far away and the speed of light is such a
Speaker 1: stubborn limitation. But until we develop a warp drives or
Speaker 1: practical wormholes, it's not realistic to think that we could
Speaker 1: explore a significant fraction of the galaxy. Yeah, Like, what
Speaker 1: would it take, I guess to send a probe to
Speaker 1: Alpha Centauri? Right, it's four light years away. That's like
Speaker 1: zillions of miles away. Right now, it seems kind of
Speaker 1: impossible because I think the furthest we've send a probe
Speaker 1: right now is just barely outside this Solar system, right,
Speaker 1: and it took like thirty years, yes, exactly, the most
Speaker 1: distant object send by humanity. Some of these old Voyager
Speaker 1: and Pioneer probes are not very far outside the Solar system,
Speaker 1: so it would take a long time for anything to
Speaker 1: get anywhere. But you know, if you were thinking about
Speaker 1: it on long time scales, it's not going to take
Speaker 1: like millions of years. We're talking like thousands or tens
Speaker 1: of thousands of years. And if you send a few
Speaker 1: probes to other planets, and if those probes are very clever,
Speaker 1: they're like AI driven self replicating probes, so they can
Speaker 1: land on some distant moon, they can find materials on
Speaker 1: those moons to make more of themselves, and then they
Speaker 1: can send those probes out, and those probes make more
Speaker 1: of themselves, and those make more of themselves. It's not
Speaker 1: impossible to imagine rapidly exploring the entire galaxy, where by
Speaker 1: rapid we mean on the time scale of like fifty
Speaker 1: to one hundred thousand years. So that's a really interesting
Speaker 1: argument because it suggests that with technology not super far
Speaker 1: in our future, some other civilization could have explored the
Speaker 1: whole galaxy with self replicating probes. And then you have
Speaker 1: to ask, like, well, why haven't we been visited by
Speaker 1: such a probe yet? Are there no other advanced civilizations
Speaker 1: out there who have this idea? Yeah, we address this
Speaker 1: question and this whole scenario in our book. Frequently asked
Speaker 1: questions about the universe. That was one of the chapters,
Speaker 1: right like why haven't we seen aliens? And maybe we
Speaker 1: can do that with these self repulating robots, which would
Speaker 1: litter the universe in no time exactly. And one basic
Speaker 1: assumptions a lot of these scenarios make is that aliens
Speaker 1: want us to find them, or that they are trying
Speaker 1: to talk to us, or they are curious about the
Speaker 1: rest of the universe as well, so they're sending messages
Speaker 1: out or they're sending probes out there explorational the same
Speaker 1: way that we are. But of course we don't know
Speaker 1: what alien psychology is like, and what does aliens want,
Speaker 1: or even what it means to want something as an alien.
Speaker 1: So these days a lot of people are imagining other
Speaker 1: ways to detect aliens when they're not trying to be detected.
Speaker 1: Are there things the aliens can do imprints they leave
Speaker 1: on the universe that aren't intended for us to discover them,
Speaker 1: but might allow us to spot them anyway. So today
Speaker 1: on the program, we'll be asking the question could we
Speaker 1: detect alien nuclear explosions? I imagine you're saying these are
Speaker 1: like accidental nuclear explosions or on purpose nuclear explosions, either one, right,
Speaker 1: we don't discriminate. We just like to know the aliens
Speaker 1: are there, and whatever they do in their normal civilization extrapolasition,
Speaker 1: we'd like to see if we could detect it. Maybe
Speaker 1: they're just doing testing like we're doing, or maybe they
Speaker 1: have some globe spanning nuclear annihilation. The question is, could
Speaker 1: we see it right, If aliens are blowing up nuclear bombs,
Speaker 1: is it possible for us to spot that? Yeah, because
Speaker 1: as you mentioned, you know, one scenario is that they're
Speaker 1: sending out signals on purpose, either to talk to us
Speaker 1: directly or just like that's their TV, maybe their broadcast TV.
Speaker 1: But I think we talked in an earlier episode about
Speaker 1: how like for us to detect the signal from an alien,
Speaker 1: it would have to be like a pretty focus beam, right,
Speaker 1: like the like the club we're just listening to their
Speaker 1: TV broadcast is pretty low, that's right. If you're just
Speaker 1: sending signals in every direction, then you pay a really
Speaker 1: big price because those signals get weaker with distance, and
Speaker 1: they get weaker with distance squared. So when signals go
Speaker 1: twice as far, they're four times as week, When they
Speaker 1: go ten times as far, they're one hundred times as week.
Speaker 1: That makes it really really hard to detect non focus signals.
Speaker 1: And if we wanted to detect signals that we could
Speaker 1: generate using technology that we have, we would not be
Speaker 1: able to spot signals of the kinds we can generate
Speaker 1: using our own technology from planets that are more than
Speaker 1: like one light year away. If however, they're like beaming
Speaker 1: us messages, they're shooting laser beams in our direction. Then
Speaker 1: the math works differently and we could get messages from
Speaker 1: further away, But then they'd have to know we were
Speaker 1: here and try to send us messages on purpose, which
Speaker 1: seems less likely. I think here today we're exploring a
Speaker 1: different scenario, which is like, what if they're doing something
Speaker 1: without trying by accident maybe or through some sort of event,
Speaker 1: and then that's what we see, and that's how we
Speaker 1: know that there are aliens exactly. And people have been
Speaker 1: thinking about this and wondering like, well, what's the most
Speaker 1: visible thing that you can do, not just broadcasting Rick
Speaker 1: and Morty episodes into the cosmos? All right, Sometimes our
Speaker 1: civilization does things which generate very bright flashes of radiation,
Speaker 1: and hey, what's brighter than a nuclear explosion? But what
Speaker 1: if there's a kid in that alien planet pointing a
Speaker 1: laser partner directly Ow my eye? Ow alien burnt my eye? Yeah,
Speaker 1: I know, that's why you should be careful you knock
Speaker 1: about this guy. So then the scenario here is that
Speaker 1: somehow this alien civilization out there is exploding nuclear their
Speaker 1: own nuclear bombs, either by accident, or some testing or something.
Speaker 1: Maybe they have their own nuclear war, and so the
Speaker 1: question is like, could we see those nuclear explosions exactly?
Speaker 1: All right? Well, as usual, we were wondering how many
Speaker 1: people out there had the interesting curiosity to ask this
Speaker 1: question about alien life and how we could detect them. So,
Speaker 1: as usual, Daniel went out there. Did you go to
Speaker 1: the internet or are you? Are you going on campus?
Speaker 1: Now these are still Internet based questions. I felt a
Speaker 1: little bit weird walking around campus asking people about aliens
Speaker 1: and nuclear bombs. That's never stopped you before. I thought
Speaker 1: it might get reported to the UCI police. Yeah, you
Speaker 1: have tenure. They're not gonna fire you. Anyways, usually have
Speaker 1: to do worst things. So thanks very much to our
Speaker 1: internet volunteers who responded with enthusiasm to this question. If
Speaker 1: you would like to play this part in future episodes,
Speaker 1: please write to me to questions at Daniel and Jorge
Speaker 1: dot com. We can do it all over email. It's fast,
Speaker 1: it's easy, it's fun to think about it for a second.
Speaker 1: Do you think we could detect alien nuclear explosions? Here's
Speaker 1: what people have to say. Yes, So it depends whether
Speaker 1: the detonation happened on Earth or a planet from Solar
Speaker 1: System or somewhere far away. In any of these cases,
Speaker 1: I think we might be able to detect. Considering that
Speaker 1: why decaying of the matter and the amount of radiation
Speaker 1: that is being exposed out of that location on Earth,
Speaker 1: we might be able to analyze whether it's man made
Speaker 1: or alien, and if it is happening on some other planet.
Speaker 1: Considering the amount of information that we have already gained
Speaker 1: with the telescopes in place, we will be able to
Speaker 1: do it. That's what I believe. By now, we have
Speaker 1: satellites now that can detect detonations on Earth. I don't
Speaker 1: think it would work at interstellar distances, especially considering that
Speaker 1: there's so many sources of radiation in space, you know,
Speaker 1: from stars to gamma ray burst everything in between. So no,
Speaker 1: I don't think we could. Well, I guess so. I
Speaker 1: guess it would depend on how good the detector was
Speaker 1: and how far away it was away from you. If
Speaker 1: there was set off over your head, you might be
Speaker 1: able to detect it pretty soon. I feel like we
Speaker 1: probably could detect alien nuclear detonations if there was like
Speaker 1: enough radiation to reach far enough, But other than that,
Speaker 1: I don't really think we could all right. Some people
Speaker 1: said yes, some people said no, some people said maybe yeah.
Speaker 1: I think they really put their finger on the issue,
Speaker 1: which is that nobody knows, not even us. It's all
Speaker 1: about brightness and distance. You know, what's the faintest radiation
Speaker 1: we could pick up? And how close would these bombs
Speaker 1: have to be for us to spot them. I feel
Speaker 1: like you're missing one important factor, which is how big
Speaker 1: are these bombs? That's a huge unknown. You're right, and
Speaker 1: we'll get into it in a minute. And the only
Speaker 1: standard we have is like how big are our bombs?
Speaker 1: So we can imagine whether we could detect nuclear explosions
Speaker 1: of the size we could make if aliens also did them.
Speaker 1: All right, we'll dig into it, but I guess first
Speaker 1: let's start with the basics, Like Daniel, what happens during
Speaker 1: a nuclear explosion? Besides the explosion part of it. Yeah,
Speaker 1: to understand whether we could see a nuclear explosion on
Speaker 1: another planet, you have to think about what the signals are,
Speaker 1: like what signals does a nuclear explosion generate? And we
Speaker 1: had a whole episode about how nuclear bombs work where
Speaker 1: we went to a lot of detail, but not enough
Speaker 1: detail for you to build a nuclear bomb. Hopefully but
Speaker 1: human nuclear weapons at least are either fission weapons or
Speaker 1: fusion weapons triggered by fission. And remember that the basic
Speaker 1: processes here fission involved breaking up of a heavy nucleus
Speaker 1: like plutonium or uranium, which then shoots off a bunch
Speaker 1: of neutrons and rams into other nuclei, which breaks them
Speaker 1: apart and sets off a chain reaction where you very
Speaker 1: rapidly are releasing energy. And the fusion bomb is similar
Speaker 1: except it uses a fission bomb to compress a bunch
Speaker 1: of fusion fuel that it fuses, and in both scenarios
Speaker 1: the key thing is releasing a huge amount of energy
Speaker 1: very very quickly, but not just energy, right, You're releasing
Speaker 1: energy but also a lot of radiation. Yeah, maybe step
Speaker 1: us through like what's actually being released, Like when you
Speaker 1: fuse things together they click together, to nuclear click together,
Speaker 1: and then what actually gets released like light or particles
Speaker 1: or Yeah, so fusion produces high energy photons. It also
Speaker 1: produces neutrons and electrons and neutrinos. Right, so all these
Speaker 1: kinds of things are produced and then much just produced,
Speaker 1: but they're like they're produced, but then they're flying really fast. Yes,
Speaker 1: they're produced, and they're carrying a lot of energy is
Speaker 1: what you actually see from the bomb from like a
Speaker 1: certain distance. Depends on how that energy is absorbed or
Speaker 1: not absorbed. So, for example, a lot of the energy
Speaker 1: gets dumped into the matters immediately surrounding the bomb, right,
Speaker 1: and so it's absorbed very very rapidly by the st
Speaker 1: around the bomb, which expands that matter and creates a
Speaker 1: shock wave. I mean like the bomb casing or like whatever,
Speaker 1: if it's on the ground, that that's what it's going
Speaker 1: to push out. Yeah, I mean whatever material is around
Speaker 1: the bomb, like the air or the water or the ground,
Speaker 1: and you get very different scenarios if you have an
Speaker 1: in air explosion or underground explosion or just above the water.
Speaker 1: But the material that surrounds the bomb is inundated with
Speaker 1: a huge amount of energy, a lot of it from
Speaker 1: gamma rays, and a lot of that gets rapidly absorbed
Speaker 1: and that material gets heated up to like tens of
Speaker 1: millions of degrees and then you get this shockwave. So
Speaker 1: in the end, on average, and it depends on exactly
Speaker 1: what you've surrounded the bomb with, about half of the
Speaker 1: energy of a nuclear bomb go these shockwaves, these expanding
Speaker 1: waves of matter basically sound waves through matter that carry
Speaker 1: away a lot of this energy, doesn't It depend on
Speaker 1: what's around the bomb. Like if you explode it in water,
Speaker 1: all of it's going to go into the water, But
Speaker 1: if you put it in air, you know there's maybe
Speaker 1: a chance for that energy to go out further. Even
Speaker 1: in air, a lot of that energy is absorbed by
Speaker 1: the air and you get shock waves. So yes, it
Speaker 1: definitely does depend on the kind of material surrounded. Like
Speaker 1: if you blow it up underground, it's absorbed differently than
Speaker 1: if you blow it up in the air. But you know,
Speaker 1: since we're just dealing with like approximate numbers here, roughly
Speaker 1: on average, over all those circumstances, about half of the
Speaker 1: energy gets dumped into shock waves and then like another
Speaker 1: forty percent of the energy comes out in what we
Speaker 1: call thermal radiation, basically photons to which the atmosphere is
Speaker 1: transparent visible light, infrared light, UV light, things that are
Speaker 1: not immediately absorbed by the surrounding material which conduct fly
Speaker 1: out through that material because that material is transparent to
Speaker 1: this kind of radiation. Why is it transparent. Is it
Speaker 1: because it just doesn't absorb because of quantum effects, or
Speaker 1: is it just that it's so like air is so
Speaker 1: thin that it just doesn't hit enough air molecules. Yeah,
Speaker 1: air is transparent to visible light, right, we know that
Speaker 1: because we can see the sun through the air. Why
Speaker 1: is the air transparent to visible light, You're right, is
Speaker 1: quantum effects. You have certain gases under certain conditions, and
Speaker 1: they either like to absorb photons of various frequencies or
Speaker 1: they don't. These air molecules can't just absorb a photon
Speaker 1: of an arbitrary frequency. They have to have like a
Speaker 1: quantum state that their electron can jump up into, or
Speaker 1: like a new rotation that they can do. So atoms
Speaker 1: can only absorb certain frequencies of light, and the other
Speaker 1: frequencies pass right through. So air is mostly transparent to
Speaker 1: visible light and also infrared light. It's less transparent in
Speaker 1: the UV, which is one reason why we have like
Speaker 1: UV space telescopes above the atmosphere. But you know a
Speaker 1: lot of energy is dumped out and so some of
Speaker 1: these very high energy UV light does survive passing through
Speaker 1: the atmosphere. If you're near a nuclear bomb, so you
Speaker 1: have like fifty percent of it roughly in the shock wave,
Speaker 1: like another forty percent in thermal radiation these photons that
Speaker 1: don't get absorbed, and then another ten percent in other
Speaker 1: particles like neutrons or very high energy photons we call
Speaker 1: gamma rays or electrons. Is it sort of like lightning
Speaker 1: and thunder? Like you will see the flash of a
Speaker 1: nuclear bomb before you actually get hit by the shockwave. Yeah,
Speaker 1: it's really cool. You actually see two flashes of a
Speaker 1: nuclear bomb. You see the first flash because the visible
Speaker 1: light reaches you before the shockwave. But at some point
Speaker 1: the shock wave passes the fireball because the shockwave is
Speaker 1: making the material more dense, which acts to obscure the fireball.
Speaker 1: So the shockwave itself is opaque to the kind of
Speaker 1: light being generated by the nuclear bomb. So then for
Speaker 1: a moment you can't see the fireball, but then it
Speaker 1: dissipates and you can see it again. So it's like
Speaker 1: you see fireball and then you see the shock wave,
Speaker 1: and then you see the fireball. So it's sort of
Speaker 1: like lightning and then thunder and then a second flash
Speaker 1: of lightning. Whoa, I mean, assuming you survived the first
Speaker 1: event to get to see the other two. Yeah, So
Speaker 1: this is a very characteristic signature of nuclear bombs. This
Speaker 1: double peak of gamma radiation over several milliseconds. Well, it's
Speaker 1: definitely an event and nuclear explosion. And so the question
Speaker 1: is if aliens exploded nuclear bombs in their planets, could
Speaker 1: we see them from here. Let's dig into that question
Speaker 1: and what we should be looking for if we're looking
Speaker 1: for those kinds of signals. First, let's take a quick break.
Speaker 1: All right, we are spending today imagining aliens blowing themselves up.
Speaker 1: We're not hoping they blow themselves up, but if they do,
Speaker 1: we hope to see it. We're not hoping they blow
Speaker 1: themselves up, but if they do, it would be nice.
Speaker 1: Is that what you say? Is that? What are you saying?
Speaker 1: I mean, I don't aliens living in obscurity forever, or
Speaker 1: aliens killing themselves about then we find out about them.
Speaker 1: I mean, it would also be kind of sad to
Speaker 1: discover aliens only to discover they had all killed themselves,
Speaker 1: that they were the last ones. Yeah, that would be
Speaker 1: that would be pretty tragic. Yeah, that would be a bummer. Well,
Speaker 1: we've talked about what a nuclear explosion is and what
Speaker 1: happens to it. So you said about half of the
Speaker 1: energy is really just pushing the stuff around it so
Speaker 1: I imagine that won't get very far. Maybe forty percent
Speaker 1: of it goes into just light, basically invisible light or
Speaker 1: light you'd be light, And about ten percent of it
Speaker 1: goes into shooting out basically radiation, right, like charged particles. Yeah,
Speaker 1: not just charged particles, but neutrons, gamma rays, and also electrons. Well,
Speaker 1: gamma rays are light, right, Gamma rays are very high
Speaker 1: energy photons, Yeah, even more high energy than X rays
Speaker 1: or UV. These are all ionizing radiation. They all have
Speaker 1: the capacity to knock electrons off of materials. And because
Speaker 1: they're ionizing and electrons themselves have charge, they can also
Speaker 1: generate an electro magnetic pulse. This is a common feature
Speaker 1: a lot of movies nuclear weapons knocking out electronics because
Speaker 1: of a very high energy pulse of electromagnetic radiation. Oh interesting,
Speaker 1: it's not just that it's like a giant magnet. It's
Speaker 1: like it's actually shooting out little magnets. Yeah, exactly. And
Speaker 1: so all those gamma rays and all those electrons can
Speaker 1: damage a lot of electronics. So if you have electronics
Speaker 1: near a nuclear weapons blast, then you will feel it.
Speaker 1: They could get knocked offline. They don't shoot protons explosions
Speaker 1: or neutrinos. They do generate a lot of neutrinos. He
Speaker 1: has absolutely fusion and fission both generate neutrinos, but not
Speaker 1: so many protons. Mostly neutrons and neutrinos and electrons. What
Speaker 1: about later rays and sound effects like in Star Wars?
Speaker 1: They don't go pupupu as far as I've seen. It's
Speaker 1: not in the literature. But the sounds of thousands of
Speaker 1: souls being snuffed at the same time, Oh, that's sad.
Speaker 1: I don't know if they create a great disturbance in
Speaker 1: the force. We don't have detectors that can measure the
Speaker 1: force yet, so I'm not sure about that, not yet
Speaker 1: at least, although I have a good acronym for them.
Speaker 1: They should be a named Jedi, right, And how does
Speaker 1: that work? Just the Electron Detection Institute sounds good? Are
Speaker 1: you setting that up with some funding? Are you going
Speaker 1: to endow the Jedi Institute? Maybe I have already, I'm
Speaker 1: just not telling you. No. That's extra frustrating. But you know,
Speaker 1: there are a lot of scientists here on Earth that
Speaker 1: are developed very sensitive technology for a studying nuclear weapons,
Speaker 1: both because we want to understand what happens when they
Speaker 1: blow up, because we have done tests and we want
Speaker 1: to understand whether our nuclear weapons are working and are
Speaker 1: still working and are surviving the test of time as
Speaker 1: they sit in our stockpiles. But also because we wanted
Speaker 1: to detect if other countries are blowing up their nuclear bombs.
Speaker 1: So there's been a lot of investment in detection of
Speaker 1: nuclear weapons activity, you mean, like here on Earth. Like
Speaker 1: if you wanted to detect whether a nuclear bomb exploded
Speaker 1: here on Earth, not in an alien planet, we have
Speaker 1: techniques here on Earth to do that because I guess
Speaker 1: if someone explodes a nuther bomb on the other side
Speaker 1: of the world, in the middle of the ocean, you
Speaker 1: may not necessarily know what happened, right, And if you're
Speaker 1: a big country in a cold war or not, you
Speaker 1: might want to know if your enemies are exploding bombs
Speaker 1: or testing them, that's right, and you might not want
Speaker 1: the other country to know that you're doing it. So,
Speaker 1: like secret testing of nuclear weapons was a big industry
Speaker 1: and a sort of an arms race of hiding nuclear
Speaker 1: bomb detonations and nuclear weapons detections. I grew up in
Speaker 1: Los Almos, which was certainly a nerve center for this
Speaker 1: kind of stuff. My mom actually worked on a nuclear
Speaker 1: non proliferation technology when she was at Los Almos, trying
Speaker 1: to detect if people are blowing up nuclear bombs and
Speaker 1: all this kind of stuff. So we have a lot
Speaker 1: of ways to try to figure out if someone has
Speaker 1: blown up a nuclear bomb here on Earth. Yeah, it
Speaker 1: sounds like you would want to know. And it's kind
Speaker 1: of interesting that we test nuclear bombs right Like, first
Speaker 1: of all, I guess you have to test them right
Speaker 1: now or the wise do not even know they work.
Speaker 1: But it's amazing to me that we have tested nuclear
Speaker 1: bombs here in the US, right in the desert back
Speaker 1: in the fifties and sixties that there was all they did. Yeah,
Speaker 1: they have done above ground tests here in the US.
Speaker 1: You know, Alamagordo was the first site in New Mexico
Speaker 1: and they tested them on a bunch of islands, which
Speaker 1: was terrible and like totally obliterated them. And then there
Speaker 1: was an atmosphereic test ban treaty, so you couldn't test
Speaker 1: the nuclear weapons in the atmosphere anymore, which is good,
Speaker 1: and they moved the testing underground. So in the United States,
Speaker 1: for example, there's the Nevada underground test site where they
Speaker 1: blow these weapons up underground. But there hasn't been any
Speaker 1: recent testing. There's a Comprehensive Test Band treaty now and
Speaker 1: so instead people now do simulations. They try to understand
Speaker 1: what would happen in the event of a nuclear explosion,
Speaker 1: or try to model what's happening to the nuclear weapons
Speaker 1: we have now, are they going to survive? The whole
Speaker 1: big industry called stockpile stewardship to try to make sure
Speaker 1: that our nuclear weapons would still work if we fired them. Interesting,
Speaker 1: So it's a treaty. So like with Russian other countries,
Speaker 1: we have a handshake agreement that you can't test. Basically,
Speaker 1: you can't test nuclear weapons anymore. Yeah, there's a Comprehensive
Speaker 1: Nuclear Test Band Treaty signed in nineteen ninety six. And
Speaker 1: you know, these treatings are always complicated because some nations
Speaker 1: don't ratify them. They're signed by presidents and then their
Speaker 1: local parliaments don't agree to them. But yeah, it's been
Speaker 1: a long time since there was sort of a public
Speaker 1: test of a nuclear weapon out in the open, all right.
Speaker 1: So if someone did test the weapon or use one
Speaker 1: here on earth, how can we detect them? So we
Speaker 1: have a few ways to try to spot this. Number
Speaker 1: one is seismic. If you do test underground, then it's
Speaker 1: going to shake the earth and the earth will ring
Speaker 1: like a bell. Shock waves will pass all the way
Speaker 1: around the Earth, and you can detect them in other
Speaker 1: places the same way we can put detectors in California
Speaker 1: that can spot earthquakes in Japan or in other parts
Speaker 1: of the world. You can detect large seismic events all
Speaker 1: over the world. Right because I guess the shock waves
Speaker 1: of these earthquakes or nuclear explosions, they kind of go
Speaker 1: through the rock of the Earth, right, even though it's
Speaker 1: like lava and molten it'll still kind of propagate sound
Speaker 1: waves lava sound waves. Imagine the Earth is just like
Speaker 1: a ball of metal and you ring it with a hammer,
Speaker 1: then those sound chock waves are going to bounce all
Speaker 1: around inside it. And this is actually really cool for
Speaker 1: studying the interior of the Earth. You ring the earth
Speaker 1: and how those shockwaves move through the earth tells you
Speaker 1: about what's inside of it. And like the boundary layers,
Speaker 1: that's actually given us a lot of clues about what's
Speaker 1: inside the earth. Is watching the impact of earthquakes sending
Speaker 1: shockwaves through the earth. It can be hard, however, to
Speaker 1: tell the difference between an earthquake and a smaller nuclear
Speaker 1: weapons explosion, and they try to do a lot these
Speaker 1: days to hide the nuclear weapons explosions by having like
Speaker 1: dampers materials which will absorb a lot of this energy
Speaker 1: instead of properly getting it into the earth. And one
Speaker 1: thing that they've done to try to distinguish between earthquakes
Speaker 1: and nuclear bombs is to listen to it, to take
Speaker 1: the data and translate it into an audio file. And
Speaker 1: it turns out the human brains are pretty good at
Speaker 1: distinguishing the sound of an earthquake versus the sound of
Speaker 1: a nuclear bomb going off. Okay, so sound waves through
Speaker 1: the earth is one way we can detect them here
Speaker 1: on Earth. What are some of the other ways? Other
Speaker 1: ways are through the air and through the water. So
Speaker 1: if you, for example, blowing up underwater, then you create
Speaker 1: hydroacoustic signals. It's just like shock waves through the earth,
Speaker 1: but instead now you're make sways through the water, and
Speaker 1: water is very good at transmitting sound. Right. The speed
Speaker 1: of sound through water is faster than it is through air,
Speaker 1: and so sound travels pretty far. All the way across
Speaker 1: the globe, which is one reason why they think that
Speaker 1: like whales can talk to each other from different parts
Speaker 1: of the planet. You know, they think whales in Japan
Speaker 1: might be able to hear the songs of whales off
Speaker 1: of Alaska, this kind of stuff. And so in the
Speaker 1: same way, if you blow up a nuclear bomb anywhere
Speaker 1: neither its not even just in the water, then the
Speaker 1: seismic waves will propagate through the ocean. And we have
Speaker 1: a lot of listening stations underwater to try to listen
Speaker 1: for all sorts of activity, but including nuclear explosions. Is
Speaker 1: that allowed? Can you test nuclear weapons in the water?
Speaker 1: Definitely not allowed, but has been done in the past, right,
Speaker 1: all right, how else you can also look more directly
Speaker 1: for the radioactivity, right if you do blow up a
Speaker 1: nuclear bomb, and there's a lot of radiation emitted and
Speaker 1: radioactive elements. So one thing we do is we try
Speaker 1: to sample by airplane. You know, you have airplanes flying
Speaker 1: all around the world, and they're sampling for unusual radioactive isotopes,
Speaker 1: some of which are indicative of nuclear explosions. Even if
Speaker 1: you like test it underground, a little bit of these
Speaker 1: radioactive isotopes will eventually leak. It's not always easy to
Speaker 1: tell where the nuclear bomb explosion happened using these techniques,
Speaker 1: because it depends on how it's carried by the wind
Speaker 1: and the weather and how recently it happened. But you
Speaker 1: can sort of tell that one maybe did happen if
Speaker 1: you pick up a signal of these particular fingerprints of
Speaker 1: a nuclear bomb through their radioactive isotopes. So that's happening
Speaker 1: right now. Like there are aeroplanes out there up there
Speaker 1: basically sweeping the earth like a like a roombay. Exactly.
Speaker 1: I don't know the details because they're not public because
Speaker 1: like the US doesn't want Russia, for example, to know
Speaker 1: exactly how it's monitoring it, because then Russia will know
Speaker 1: how best to evade it. So it's a whole game
Speaker 1: of secrecy. But absolutely I'm sure that the Russians and
Speaker 1: the Americans are both monitoring the atmosphere in high altitude
Speaker 1: planes to try to detect whether the other side is
Speaker 1: cheating on the Test band treaty. We're also basically looking
Speaker 1: for these explosions, right like if you can have satellites
Speaker 1: maybe with camera strain at the Earth looking waiting for
Speaker 1: these flashes of light, absolutely, and that's one of the
Speaker 1: most powerful ways we can see these and one of
Speaker 1: the ways that might apply to alien detonations, which is
Speaker 1: just look with satellites, right, we have pictures basically the
Speaker 1: entire surface of the Earth, and we can look for
Speaker 1: high energy sources of gamma rays and X rays, which
Speaker 1: are unusual and you don't expect to produce these things
Speaker 1: in lots of different ways. And so if you see
Speaker 1: one of these signals, flashes of gamma rays, especially the
Speaker 1: double peak signature, then you have a very strong smoking
Speaker 1: gun signature of a nuclear detonation. But what if you
Speaker 1: detonated underground, like deep underground would be with the X
Speaker 1: rays and gamma rays still make it through all those
Speaker 1: layers of rock. It depends a lot on the shielding, right,
Speaker 1: and sometimes they try to shield it with heavier metals
Speaker 1: or they go deep deep underground. X rays can penetrate
Speaker 1: a lot of material. Rays tend to be more ionizing,
Speaker 1: so they do end up getting absorbed, but it depends
Speaker 1: a lot on the depth. All right, Well, that's how
Speaker 1: you can tell if someone exploded something here on Earth.
Speaker 1: But what about the question of aliens exploding things in
Speaker 1: their planets? Could we detect alien explosions or an alien
Speaker 1: nuclear war. So if aliens have the same kind of
Speaker 1: technology that we have, meaning they're blowing up bombs similar
Speaker 1: to the ones we have, then we can look for
Speaker 1: the same signatures from their planets that we would look
Speaker 1: for on Earth. Obviously, we can't look for seismic activity
Speaker 1: or hydroacoustic activity, and we can't sample their atmosphere directly.
Speaker 1: The best way to do it would be to look
Speaker 1: for these gamma ray flashes. And of course we already
Speaker 1: have telescopes that are scanning the sky looking for gamma
Speaker 1: rays because lots of non alien sources of gamma rays
Speaker 1: are very interesting to us, and there's even a huge
Speaker 1: fun physics mystery about gamma ray flashes. These things are
Speaker 1: called gamma ray bursts that come from all over the sky.
Speaker 1: We don't really understand them. They last for like sometimes
Speaker 1: a few seconds, sometimes like thirty seconds. We think they
Speaker 1: might be due to the collapse of supermassive stars, but
Speaker 1: they generate very bright flashes of gamma rays that are
Speaker 1: sort of similar to what you might expect from a
Speaker 1: nuclear detonation. M I think you're sort of painting the
Speaker 1: scenario where We're basically looking at the sky right with
Speaker 1: giant antennas that can detect gamma rays. And if we
Speaker 1: somehow are pointing to a particular planet or star and
Speaker 1: we see a big flash or a signal, then that
Speaker 1: could be the sign that the amiens blew themselves up.
Speaker 1: It could be the sign. As one of the members
Speaker 1: of Listener Panel pointed out, it might be hard to distinguish. Right.
Speaker 1: On one hand, it's cool that supermassive stars collapse and
Speaker 1: give off gamma ray bursts. On the other hand, it's
Speaker 1: a bit of a bomber because it makes it harder
Speaker 1: to distinguish between alien nuclear bomb gamma ray bursts and
Speaker 1: just natural sources of gamma ray bursts. But I guess
Speaker 1: if it was a super massive star collapsing, wouldn't we
Speaker 1: also see other signs that go along with it that
Speaker 1: wouldn't go along with a nuclear explosion. It could be,
Speaker 1: And one thing we're doing is to try to study
Speaker 1: these gamma ray bursts in more detail and see whether
Speaker 1: they come along with other signs like flashes of neutrinos
Speaker 1: or other things we can see in the optical To
Speaker 1: try to figure these things out. We don't always have
Speaker 1: a lot of warning, right, We don't know when it's
Speaker 1: going to happen. We just see like, oh wow, that
Speaker 1: was a big flash of gamma rays from this spot
Speaker 1: in the sky. You don't always have time to train
Speaker 1: other telescopes on that spot to get sort of multi
Speaker 1: channel data, and they do look kind of similar. In fact,
Speaker 1: when we first discovered gamma ray bursts, scientists thought that
Speaker 1: what they were seeing were gamma rays from earthbound detonations
Speaker 1: of nuclear weapons. They thought they had just picked up
Speaker 1: the Russian explosions because I would explain the signal too, Yeah,
Speaker 1: because that would have explained the signal. Now, gamma ray
Speaker 1: bursts come from really really incredibly powerful events. These things
Speaker 1: release enormous amounts of energy, so we can see gamma
Speaker 1: ray bursts from all across the universe. We've seen them
Speaker 1: from really really far away, like millions and millions, almost
Speaker 1: a billion light years away, because they are so powerful.
Speaker 1: Some of these things released like ten to the forty
Speaker 1: four jewels of energy just in the gamma rays, and
Speaker 1: so they're very bright, very powerful. We can see these
Speaker 1: things from very very far away. Our nuclear bombs are
Speaker 1: not nearly as powerful as these other natural sources of
Speaker 1: gamma rays, so they would be relatively dim in comparison.
Speaker 1: You mean if there was an alien looking at us
Speaker 1: for these gamma ray bursts, Yeah, exactly. If aliens were
Speaker 1: watching our nuclear explosions and they had technology similar to hours,
Speaker 1: they would not be able to see our explosions from
Speaker 1: very very far away because our explosions are not that
Speaker 1: bright compared to gamma ray bursts. Well, sort of depends
Speaker 1: on how many nukes we detonate at the same time.
Speaker 1: It does. But if you imagine, like a doomsday scenario,
Speaker 1: you take all of our nuclear weapons, you set them
Speaker 1: all off at the same time, you can calculate, like
Speaker 1: how much energy in gamma ray bursts would be emitted.
Speaker 1: It's only like ten to the nineteen jewels, Like obviously cataclysmic,
Speaker 1: terrible scenario, enough energy to devastate civilization on Earth. But
Speaker 1: compared to gamma ray bursts, which are ten to the
Speaker 1: forty four jewels, we're talking about ten to the twenty
Speaker 1: five times less powerful than a gamma ray burst, So
Speaker 1: they're relatively dim compared to these other astrophysical sources. It's
Speaker 1: twenty five orders of magnitude weaker, but I guess you're saying, like,
Speaker 1: if we do see a gamma ray burst and we're
Speaker 1: not sure if it's an alien or a star collapsing,
Speaker 1: I mean that would mean that this alien civilization blew
Speaker 1: up twenty five orders of magnude, many more bombs than
Speaker 1: we did. We're a bomb that was twenty five orders
Speaker 1: of magnitude bigger than ours. Yeah, it depends on how
Speaker 1: far away they are. If they are as far away
Speaker 1: as some of these really distant gamma ray bursts, then
Speaker 1: you're right, they would have like much much bigger nuclear
Speaker 1: arsenals than we have, like ten to twenty five times
Speaker 1: as powerful, or they had or they exactly exactly kind
Speaker 1: of tense. But if you're imagining an alien civilization with
Speaker 1: the power of our nuclear weapons and they had some
Speaker 1: sort of cataclysmic event where they blew them all up
Speaker 1: at once, then you can ask how far away would
Speaker 1: they be for us to detect it. Our gamma ray
Speaker 1: sensors are pretty sensitive, but remember that things get much
Speaker 1: dimmer as you get further away, so the sources have
Speaker 1: to be very bright to be visible. For an alien
Speaker 1: nuclear war at human levels to look about as bright
Speaker 1: as a typical gamma ray burst, that we see it
Speaker 1: could only be around eight to ten astronomical units away
Speaker 1: because it wouldn't be nearly as bright as its source
Speaker 1: as gamma ray bursts that are typically much further. So
Speaker 1: eight to ten AU that's like the distance to Pluto.
Speaker 1: Beyond that, we might still be able to pick it up,
Speaker 1: but it would start getting dimmer very fast because remember
Speaker 1: the next star over is much further away than Pluto.
Speaker 1: So it's possible to see it in another star system,
Speaker 1: but not a guarantee, and our abilities fade very quickly
Speaker 1: as you consider even further star systems. So if like
Speaker 1: there are aliens in Pluto and they had a nuclear
Speaker 1: war and they detonated all their nuclear weapons, then we
Speaker 1: would see it through the gamma ray radiation. But if
Speaker 1: it happened like and in another source system, it'd be
Speaker 1: way too dim, or would it, or maybe maybe just
Speaker 1: need better instruments. I mean, you're not saying it's impossible,
Speaker 1: or you're saying it's impossible, or that it's really hard.
Speaker 1: I'm not saying it's impossible. I'm saying it's at the
Speaker 1: edge of our ability currently, like we can barely pick
Speaker 1: up super bright, very distant gamma ray bursts, or we
Speaker 1: could pick up less bright closer gamma ray bursts. Right,
Speaker 1: there's sort of a line there between distance and brightness.
Speaker 1: But we could also improve our technology and make our
Speaker 1: gamma ray detectors more sensitive. Then we could see dimmer
Speaker 1: things that were further away, including gamma ray bursts or
Speaker 1: alien technology. Is definitely not impossible. But I think you
Speaker 1: said that gamma ray are only one of the things
Speaker 1: that come out of a nuclear explosion. There's also like
Speaker 1: the actual visible light flash tour, and that's like many
Speaker 1: times bigger than the gamma ray burst. Do we see
Speaker 1: a star war happening just on the visible spectrum? We
Speaker 1: might be able to, but the universe is a little
Speaker 1: bit less transparent to that kind of light. Gamma rays
Speaker 1: are awesome because most of the universe is transparent to them,
Speaker 1: but visible life, for example, is more likely to get
Speaker 1: blocked by gas or dust or these kinds of things.
Speaker 1: But it is possible, and we should look for multiple signatures. Right,
Speaker 1: So we can look at the gamma rays, we can
Speaker 1: look in the visible light. We certainly should keep an
Speaker 1: eye on that. There are also other more subtle ways
Speaker 1: that we might be able to detect nuclear weapons explosions
Speaker 1: on other planets and to distinguish them from gamma ray bursts.
Speaker 1: The point you were making earlier about telling the difference
Speaker 1: between nuclear weapons and gamma rays. All right, let's get
Speaker 1: into those other ways we could detect an alien nuclear
Speaker 1: war and whether or not it might ever happen. But
Speaker 1: first let's take another quick break. All right, So what
Speaker 1: do you think is the scenaro here where aliens have
Speaker 1: a nuclear war? Do you think they just disagree about something?
Speaker 1: Do you think it's inevitable for all civilizations to eventually
Speaker 1: snuff themselves out? I don't know. I've heard this theory,
Speaker 1: you know, the great filter that the reason we haven't
Speaker 1: seen aliens or been visited by their probes is that
Speaker 1: technological civilizations don't tend to last very long because they
Speaker 1: tend to destroy themselves through climate change or annihilation or
Speaker 1: war or whatever. And that's possible, I suppose, but it
Speaker 1: seems to me like a huge amount of projection. It's
Speaker 1: imagining that aliens are a lot like humans, and their
Speaker 1: psychology and their struggles and their sociology is a lot
Speaker 1: like ours. And that's possible, But it also seems to
Speaker 1: me to be possible for it to be completely different,
Speaker 1: for their politics to be totally different, and they never
Speaker 1: even invent nuclear weapons. So I think it's too big
Speaker 1: a question without really data to speculate on. Yeah, it's
Speaker 1: a big unknown, but I think it has maybe kind
Speaker 1: of the basis and the idea that, you know, anything
Speaker 1: that evolves evolution works by competition, right, and so basically
Speaker 1: any intelligent society will most likely it kind of come
Speaker 1: up like we did, being having this kind of balanced,
Speaker 1: this idea of competition and killing each other but also
Speaker 1: being nice to each other. Yeah. We had an astrozoologist
Speaker 1: on the podcast recently who made that point. He said,
Speaker 1: predation is inevitable in evolution. You will eventually have one
Speaker 1: guy that wants to eat the neighboring guy. And that's
Speaker 1: probably true, but it doesn't mean that it doesn't mean
Speaker 1: you can't like progress past your evolutionary impulses. Right. Our
Speaker 1: behavior now is quite different from the behavior in which
Speaker 1: we evolve, much more complex cooperative society. So I don't
Speaker 1: know that it's inevitable that you're dominated by that competitive nature,
Speaker 1: but hey, let's find out hopefully, listen, let's not find
Speaker 1: out the negative outcome the hard way. So you're saying
Speaker 1: before that for us to see alien nuclear explosions in
Speaker 1: other planets, I mean they would have to basically detonate
Speaker 1: twenty five orders of Maude, many more bombs that all
Speaker 1: of humanity has for us to even have a chance
Speaker 1: to see it. Yes, for us to detect these bright flashes,
Speaker 1: they would have to have a much more substantial arsenal
Speaker 1: than we have twenty five orders of magnitude more right,
Speaker 1: like bombs that could destroy you. I don't even know
Speaker 1: the number for that, but twenty five orders of magnitude
Speaker 1: many more planets. Yeah, sorry, I don't know if I
Speaker 1: said twenty five times right, it's ten to the twenty
Speaker 1: five times, So it's one with a lot of zeros
Speaker 1: in front of it. Absolutely, But if they do have
Speaker 1: a canterclismic nuclear war, there will also be other impacts
Speaker 1: on their planet that we might be able to detect
Speaker 1: even if we don't spot the gamma ray burst. And
Speaker 1: these are the kind of things we might be able
Speaker 1: to spot from planets in other solar systems. And number
Speaker 1: one on that list is changes in their atmosphere. You mean,
Speaker 1: like maybe we don't detect the explosion itself, that of
Speaker 1: the nuclear war. But we can detect their nuclear winter exactly,
Speaker 1: their nuclear winter. If you do have this kind of
Speaker 1: event where you blow up a lot of nuclear bombs
Speaker 1: in your atmosphere, it would really change your atmosphere. Number One,
Speaker 1: it would very briefly make your atmosphere glow. Right, you're
Speaker 1: dumping a huge amount of energy into your atmosphere. It
Speaker 1: would ionize a bunch of the gases from the radiation
Speaker 1: produced by a lot of the byproducts, and so the
Speaker 1: atmosphere itself would glow sort of like the Northern lights.
Speaker 1: Ionized air tends to emit this kind of glow. We've
Speaker 1: seen it on Earth, we've seen it on Venus, we've
Speaker 1: seen it on Mars. And so if you have a
Speaker 1: lot of nuclear bombs, then their atmosphere would have this
Speaker 1: air glow and we might be able to spot that.
Speaker 1: Wait wait, wait, we could see their atmosphere glow like
Speaker 1: how like with telescopes. Yeah, telescopes pointed at these planets
Speaker 1: might be able to gather some information about the light
Speaker 1: that's coming directly from the planet. Right, we now have
Speaker 1: direct imaging of exoplanets. And if you see, for example,
Speaker 1: a spike in the oxygen line, that increases the oxygen
Speaker 1: rapidly by a factor of ten than our telescopes could
Speaker 1: spot that. But wait, if we can see their amosphere glow,
Speaker 1: surely we would see their explosions themselves, right, Like explosions
Speaker 1: would be pretty flashy, right, he said, forty percent of
Speaker 1: a nuclear explosions energy goes into visible light. I mean,
Speaker 1: if we can see their atmospherre glow, surely we would
Speaker 1: see their like a big flash before the explosion or
Speaker 1: during the explosion. The explosion itself might not be bright
Speaker 1: enough for us to see. It'll also be really short lived.
Speaker 1: What we're talking about here is seeing a change in
Speaker 1: the atmosphere chemistry, which we usually detect from how the
Speaker 1: light from the planet's star passes through its atmosphere or
Speaker 1: reflex off its atmosphere. So the light we get from
Speaker 1: these planets is not from any source on the planet itself,
Speaker 1: but from the star, which is why it's visible at all.
Speaker 1: The air glow might last longer than the flash, and
Speaker 1: so it might be easier to spot. But what we're
Speaker 1: doing is thinking about, like what are the multiple signatures,
Speaker 1: Because in the end, the story is going to be
Speaker 1: that you probably can't conclude that you've seen an alien
Speaker 1: an explosion based on only one of these signatures, because
Speaker 1: there are other ways to mimic any one of them.
Speaker 1: So to conclude you've seen alien signatures, what you're going
Speaker 1: to want is multiple pieces of evidence. I see, like
Speaker 1: the afterglow will last longer, so there's more likelihood that
Speaker 1: will see it. But also it's sort of like more
Speaker 1: of a telltale sign. If planet is glowing more than
Speaker 1: it should, then you can maybe infer that there was
Speaker 1: an explosion there exactly, like maybe you see a gamma
Speaker 1: ray burst and you see a bright flash of light
Speaker 1: from the visible light emission and you're wondering, like, well,
Speaker 1: was that some sort of star collapsing or was it
Speaker 1: an alien nuclear bomb? Then you can look for the
Speaker 1: air glow. There are other effects in the atmosphere as well,
Speaker 1: like these blasts tend to produce a lot of nitrogen
Speaker 1: oxides which react with and deplete ozone, And so if
Speaker 1: you're watching the atmosphere of this planet, then you're looking
Speaker 1: in the UV light, you can detect changes in the
Speaker 1: ozone layer. So a lot of these other signals require
Speaker 1: you to be looking at one of these planets already
Speaker 1: in studying its atmosphere and seeing change in its atmosphere,
Speaker 1: so it increases an ionization of the gases that lead
Speaker 1: to air glow or decrease in the ozone layer by
Speaker 1: interaction from some of the byproducts of the blast. Or
Speaker 1: if you just like see the atmosphere become opaque, Right,
Speaker 1: you have a bunch of nuclear bombs go off, it's
Speaker 1: going to throw up a huge amount of either vapor
Speaker 1: or dust or something to make the atmosphere more opaque,
Speaker 1: and that could last for years. Right, We're talking about
Speaker 1: a nuclear winter. And so if you see an atmosphere
Speaker 1: becomes suddenly more opaque than it was before, that tells
Speaker 1: you something big happened in that atmosphere, Like if there's
Speaker 1: more dust in the atmosphere, Although that could also be
Speaker 1: an asteroid, right, Like if an asteroid hits planet, it
Speaker 1: would also cause a big flash of light and also
Speaker 1: a lot put a lot of stuff in the atmosphere, right,
Speaker 1: Or would it look differently? Is it's not radioactive? Yeah,
Speaker 1: an asteroid wouldn't look exactly the same as a nuclear
Speaker 1: bomb because it wouldn't deplete the ozone in the same way.
Speaker 1: It might not cause the same amount of air glow
Speaker 1: because it wouldn't have the same sort of radioactive byproducts,
Speaker 1: but a lot of the signatures would be the same.
Speaker 1: It would throw up a lot of dust in the atmosphere,
Speaker 1: probably make the atmosphere opaque for years as well, but
Speaker 1: you probably wouldn't also get the gamma ray burst. So
Speaker 1: there's lots of things out there in the universe that
Speaker 1: could make signatures similar to alien nuclear total annihilation, global
Speaker 1: thermonuclear war, but not all of them. So if you
Speaker 1: happen to see like several of these signatures all together
Speaker 1: from an exoplanet, then you could probably conclude that there
Speaker 1: were aliens and they had just had a very very
Speaker 1: bad day. Or maybe they were celebrating something, you know,
Speaker 1: it's just how they do fireworks in that ailing culture.
Speaker 1: Maybe they detected us and they were celebrating because they
Speaker 1: were going to get to eat a good mule latter.
Speaker 1: Or maybe they try to have some fireworks and they
Speaker 1: accidentally shot the fireworks right at their nuclear arsenal and
Speaker 1: set it off. I think I've seen that on TikTok.
Speaker 1: All right, well, I kind of feel like we have
Speaker 1: to be looking for these things though, right, like gamma rays,
Speaker 1: it's not like we have a camera looking out the
Speaker 1: whole universe looking for gamma ray. Gamma detectors here on
Speaker 1: Earth are very specific. Likely we have to point them
Speaker 1: at specific stars and stuff, right, So it seems kind
Speaker 1: of unlikely that will just happen to catch another civilization
Speaker 1: having their nuclear war just as we're pointing our telescope
Speaker 1: at them. I yeah, exactly. I think some people were
Speaker 1: hoping that this would be a very easy way, a
Speaker 1: very obvious way to identify alien civilizations. But unfortunately they're
Speaker 1: not as bright as you might imagine, and the universe
Speaker 1: is very very large, and there are other ways to
Speaker 1: create a lot of these signals, and so you have
Speaker 1: to be very lucky. You'd have to be looking at
Speaker 1: a planet basically when this happens, and have been looking
Speaker 1: at it beforehand so you could see the changes. And
Speaker 1: this is one of the big problems in detecting alien
Speaker 1: civilizations is just the deep length of time. Right, Maybe
Speaker 1: alien civilizations have existed and they've all killed each other
Speaker 1: and those signals came to Earth, but like a few
Speaker 1: hundred years ago and we missed it, right. Jill Tarter
Speaker 1: is famous for saying that we've been watching for aliens
Speaker 1: for a cosmically insignificant amount of time, and adding looking
Speaker 1: for nuclear explosions is a good way to increase our
Speaker 1: ability to see them, But it doesn't change this problem
Speaker 1: that we've only been looking very very briefly, and aliens
Speaker 1: could have existed and lived for millions of years and
Speaker 1: died off recently and we still wouldn't have seen it. Yeah,
Speaker 1: I see what you're saying. You're saying like, maybe these
Speaker 1: star wars happened a long long time ago and the
Speaker 1: galaxy far far away. Is that kind of what the
Speaker 1: conclusion of scientists is, Yes, exactly, that's entirely possible. Which
Speaker 1: I feel like I've seen that in a movie already.
Speaker 1: Did somebody have that idea already? Dang it, man, every
Speaker 1: time I have a good idea, it's still your Nobel
Speaker 1: Prize again and my ten billion dollars in box office receipts.
Speaker 1: All right, Well, I think it's still kind of interesting
Speaker 1: to think about, right, It's still worth thinking about because
Speaker 1: we do happen to see the city signals, right then
Speaker 1: we would know a lot about not only the idea
Speaker 1: that we're out there alone or not, but also like
Speaker 1: what these other aliens are capable of. Yeah, and these
Speaker 1: aliens could have court developed technologies that are far beyond
Speaker 1: what we have and create flashes of light much much
Speaker 1: brighter than the kinds of things we're imagining, and we
Speaker 1: should keep our eyes open for that. I think the
Speaker 1: spirit of this is just to try to be inclusive
Speaker 1: about the kind of things we're looking for, to increase
Speaker 1: our chances of seeing anything at all. Yeah, or I think,
Speaker 1: as we talked about in other episodes, like you might
Speaker 1: be limited in your imagination, right, Like maybe if you
Speaker 1: imagine giant space civilizations and have bombs that are twenty
Speaker 1: five orders of mine need to bigger than our bombs,
Speaker 1: then we would be able to see that kind of spectacle. Yeah,
Speaker 1: we talked about the Kardaship scale of civilizations. Some aliens
Speaker 1: might have tapped into all of the energy output of
Speaker 1: their sun and built a huge laser capable of vaporizing planets.
Speaker 1: You know, I think I've seen that in the movie also,
Speaker 1: but it could be real, and if they shoot that
Speaker 1: laser in our direction, we might be able to see it.
Speaker 1: That is exactly the plot of these Star Wars trilogies.
Speaker 1: They literally suck a son into their gun and then
Speaker 1: shoot it at other planets. Not something we're recommending, but
Speaker 1: if it happens, we might be able to see it. Yeah,
Speaker 1: and you'll be there with your popcorn, gleefully looking at
Speaker 1: the extinction of thousands or billions of alien lives as
Speaker 1: they melt my eyeballs. All right, well, we hope they
Speaker 1: give you something to think about, and maybe think about
Speaker 1: the trajectory of our own civilization, Like do we want
Speaker 1: to be known to other alien species by our last moments?
Speaker 1: Or should we be working harder to work things out
Speaker 1: between us so that they see us for other reasons.
Speaker 1: Or maybe we should take all of our nuclear bombs
Speaker 1: and launch them into space and blow them up out
Speaker 1: there so aliens know we're here. You mean, like a
Speaker 1: dinner bell, Like ring a different dinner bell. No, like
Speaker 1: an invitation to a party, right, a dinner party? Sounds
Speaker 1: like maybe we should put that up for a vote
Speaker 1: before we do that. All right, Well, we hope you
Speaker 1: enjoyed that. Thanks for joining us, See you next time.
Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain
Speaker 1: the Universe is a production of iHeartRadio. For more podcasts
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