Speaker 1: Ay, Katie, what's the weather going to be like tomorrow?
Speaker 1: And you're part of Italy, let me check. It says
Speaker 1: it's going to be sunny with a chance of meatballs,
Speaker 1: and you believe in that, or the weather prediction is
Speaker 1: pretty reliable over there, not really. We're kind of near
Speaker 1: the Alps and that seems to scramble whatever weather radar
Speaker 1: that they use, So sometimes you plan a picnic and
Speaker 1: sometimes you get meat balled on. It's sure would be
Speaker 1: nice if the weather was more reliable, like it was
Speaker 1: just a pattern and it repeated, like you could sort
Speaker 1: of schedule the rain at like two pm and then
Speaker 1: at three o'clock you get some snow. That would be awesome.
Speaker 1: Or you know, you could also just try my strategy.
Speaker 1: What's that? Just moved to a place where there isn't
Speaker 1: any weather. It's just sunny every day. So essentially you're
Speaker 1: going to move to the moon. Sometimes southern California does
Speaker 1: feel like the moon? Is it because of all the
Speaker 1: people just as alien? It's because of all the people
Speaker 1: acting like aliens. Hi, I'm Daniel. I'm a particle physicist
Speaker 1: and a professor at UC Irvine in Southern California, and
Speaker 1: I definitely do appreciate the sunshine. My name is Katie.
Speaker 1: I'm the host of Creature Feature and Animals podcast. I
Speaker 1: live in northern Italy and I do appreciate that our
Speaker 1: weather is mainly like pasta and pesto based. And I
Speaker 1: know we're joking around, but is there an expression in
Speaker 1: Italian that's something like a cloudy with a chance of meatballs?
Speaker 1: Or is that a purely American thing? I think that's
Speaker 1: pretty American. In fact, meatballs are not so much of
Speaker 1: a thing in Italy. It's as much of the iconic
Speaker 1: Italian food as it seems in the US that is
Speaker 1: more kind of an Americanized version of Italy. So it's
Speaker 1: neither on our plates nor in our weather. So there's
Speaker 1: no like strange weather event that would make Italians say
Speaker 1: it's raining meatballs, huge pieces of hail or something not
Speaker 1: that I know of. Now, well, welcome to the podcast.
Speaker 1: Daniel and Jorge explain the Universe, in which we examine
Speaker 1: all of the crazy and amazing and surprising things that
Speaker 1: the universe does. We dig into whether it all makes
Speaker 1: sense and whether it can be predicted, whether we can
Speaker 1: find simple scientific, mathematical stories that explain all of the
Speaker 1: amazing things that the universe does, from compressing matter the
Speaker 1: hearts of black holes, to whizzing corks and gluons together
Speaker 1: inside neutron stars, to causing all of the weather patterns
Speaker 1: on Earth, to maybe even wiping out huge parts of
Speaker 1: life on the planet. This sounds fun. We try to
Speaker 1: be an uplifting podcast as usual, though we don't shy
Speaker 1: away from facing the truth and from accepting our ignorance
Speaker 1: of it. My friend and usual co host Orge can't
Speaker 1: be here today, but I'm very glad to be joined
Speaker 1: by one of our regular co host Katie. Katie, thanks
Speaker 1: again for joining us. Yeah. Absolutely. I noticed Jorge is
Speaker 1: suspiciously absent the day we're talking about asteroid impacts, and
Speaker 1: I gotta ask, does he got a secret space ship?
Speaker 1: Maybe he's the one causing the asteroid impacts, you know,
Speaker 1: he's the one dropping these things on the planet. Has
Speaker 1: Jorge ever been in the same room with you as
Speaker 1: the asteroid. No, but it does seem like sometimes he
Speaker 1: does want to wipe everything out. But I love thinking
Speaker 1: about the long history of life on Earth. You know,
Speaker 1: we are curious beings. We look around ourselves here on
Speaker 1: the planet. We wonder how do we get here? How
Speaker 1: did the Earth end up to be this way and
Speaker 1: not some other way? And one of the more fascinating
Speaker 1: things about the history of life on Earth is how
Speaker 1: much it hinges on certain tipping points, specific moments in history,
Speaker 1: which if they had gone another way, we might not
Speaker 1: be here, or we might look totally different, or we
Speaker 1: might have to there's or three heads. It's fun to
Speaker 1: imagine alternative earths. If you had run this experimental universe
Speaker 1: many times and had different earths, what would life on
Speaker 1: Earth look like at this point? Would there still be dinosaurs?
Speaker 1: Would we all be huge intelligent ladybugs. It's fun to
Speaker 1: imagine all the different varieties and what chance there was
Speaker 1: for us to actually get here. I love the idea
Speaker 1: of being huge intelligent ladybugs. I think we'd need a
Speaker 1: lot more oxygen for that, But I think we would
Speaker 1: also look much more fashionable. Do you think ladybugs, if
Speaker 1: they developed intelligence and technology, would also develop clothing. I mean,
Speaker 1: because they already look good naked. They already looked pretty fantastic.
Speaker 1: But I can't imagine some sort of fashion revolution of
Speaker 1: a ladybug who dares to wear stripes instead of thoughts
Speaker 1: the Ladybug Fashion Podcast. Pretty controversial stuff, but it is
Speaker 1: part of our job here, not just to understand what
Speaker 1: are the basic rules of the universe. How do the
Speaker 1: tiny particles come together and we've our reality out of
Speaker 1: little corks and gluons and electrons or whatever other particles
Speaker 1: might be out there. How does the dark matter shape
Speaker 1: the formation of the universe. We also like to think
Speaker 1: about the formation of life here on Earth and what
Speaker 1: happened to create this story, What exactly led to us
Speaker 1: being here having a podcast that isn't hosted by two ladybugs.
Speaker 1: I mean, in a way, we are feasting on the
Speaker 1: bones of dinosaurs because by their mass death came the
Speaker 1: rise of mammals, and we are mammals, So we can
Speaker 1: thank a dead dinosaur for being here, I think, in
Speaker 1: my opinion, do you think that's like the best example
Speaker 1: of inherited privilege ever? You know, It's like, we're not
Speaker 1: responsible for the dinosaur's extinction directly, but we're definitely benefiting
Speaker 1: from the fact that they were wiped out. Are you
Speaker 1: saying that some kind of very early prehistoric shrew was
Speaker 1: colluding with the asteroid and saying make it look like
Speaker 1: an accident It certainly does seem convenient, right, you know,
Speaker 1: when we benefit from the kinds of things. Well, hopefully
Speaker 1: the dinosaurs of today, that is, birds will not sue us.
Speaker 1: Statute of limitations is long, long, long expired. And one
Speaker 1: fascinating thing about the history of life on Earth is
Speaker 1: that it is punctuated with these mass extinctions. It's not
Speaker 1: just the asteroid that hit the Earth that probably wiped
Speaker 1: out the dinosaurs that created a new flowering of mammals.
Speaker 1: There many times in the history of life on Earth
Speaker 1: when there were these wipeout events where a huge fraction
Speaker 1: of life on Earth was killed, making room for new developments,
Speaker 1: new explorations of the evolutionary tree by the remaining life.
Speaker 1: And it's interesting to think about how each of these
Speaker 1: contribute to us being here today. Right, If all of
Speaker 1: those hadn't gone exactly the way that they went, we
Speaker 1: wouldn't be here talking about it. Maybe we wouldn't even
Speaker 1: be any intelligent life on Earth. It would just be
Speaker 1: a bunch of dumb dinosaurs ting on each other and
Speaker 1: nibbling on plants, right, I mean, it's just hard to
Speaker 1: know where things would have been. I mean, as you said,
Speaker 1: like when there is a die off of animals, there
Speaker 1: is an opportunity as long as the earth is still
Speaker 1: habitable for a new kind of group, a resurgence of
Speaker 1: species who otherwise would not be able to really thrive
Speaker 1: because they'd be out competed by the animals that went extinct.
Speaker 1: So it's hard to imagine, you know, if dinosaurs hadn't
Speaker 1: died off, you know, maybe there would not have been
Speaker 1: evolutionary pressure for any one species to become as intelligent
Speaker 1: as humans. Maybe it would have been too dangerous a
Speaker 1: life for primates to have been able to come to power.
Speaker 1: It's just it's so hard to know. Of course, you know,
Speaker 1: we could have also just been like two dinosaurs now
Speaker 1: talking about stuff on the podcast, talking about like what
Speaker 1: if we had gone extinct because of an asteroid? Would
Speaker 1: some of those little shrews turned into weird pink things? Yea, exactly.
Speaker 1: And I think there's something really interesting that you brought
Speaker 1: up there that's not widely enough appreciated, which is the
Speaker 1: importance of randomness and opportunity in evolution. You know, some
Speaker 1: people feel like evolution is this transformation where species develop
Speaker 1: into more and more advanced versions of themselves. But you know,
Speaker 1: there's really a randomness there, Like how does the species
Speaker 1: change from generation to generation. It's from like changes in
Speaker 1: the genetic code, which comes from transcription errors or cosmic rays.
Speaker 1: There's no design here. It's really just like a random
Speaker 1: walk through genetic space. Right, It's like throwing a bunch
Speaker 1: of dice to see what your kids are going to be. Like, yeah,
Speaker 1: I mean, so evolution doesn't have a game plan. I
Speaker 1: think that's one of the most important things to understand
Speaker 1: is evolution is not this like efficient force perfecting things
Speaker 1: into their most like quote unquote perfect forms. It's just
Speaker 1: a very simple rule. If something survives and passes on
Speaker 1: its genetic information, hooray, it's survived and passed on its
Speaker 1: genetic information to the next that's it. That is absolutely it.
Speaker 1: And for that extremely simple rule, you get incredibly marvelous complexity.
Speaker 1: So there are a lot of things that can happen.
Speaker 1: It's not just the random mutation of DNA. It's the
Speaker 1: reshuffling of DNA. Right, you have like mate choice, what
Speaker 1: happens there, And then it's the environment, like what happens
Speaker 1: with your environment. There can be random changes in the
Speaker 1: environment that leads to selective pressures, to extinction events, two
Speaker 1: changes in related species that then causes the other species
Speaker 1: to have to evolve. So there's so many factors that
Speaker 1: go into evolution that from this incredibly simple rule just
Speaker 1: like if you can pass on your DNA, yeah you
Speaker 1: did it. You passed on your DNA, and then the
Speaker 1: next generation gets a shot at that. That has turned
Speaker 1: into just this incredibly immensely complex and convoluted situation with
Speaker 1: life on Earth, where sometimes an animal will have weird
Speaker 1: features that we try to look at, we think, what
Speaker 1: is this, what is the thing? Why did they evolve it?
Speaker 1: And it just turns out it's this weird artifact of
Speaker 1: earlier evolution or something like you know, we have this
Speaker 1: appendix and it's kind of mysterious. What does it do.
Speaker 1: We're not really sure if it has much of a
Speaker 1: purpose for us. But it's not like evolution has that
Speaker 1: foresight of like, well, I better take this appendix out
Speaker 1: because they're not really going to need it that much
Speaker 1: as modern humans. So like, it's not an intelligent designer.
Speaker 1: It's kind of just improv all the time. I think
Speaker 1: that's a really fascinating aspect of it, not just that
Speaker 1: there's a randomness there, but that it's so tightly linked
Speaker 1: to the environment in which this exploration is happening. Right,
Speaker 1: It's really a reflection. It's like a mirroring of the
Speaker 1: situation that doing the selection because one animal might survive
Speaker 1: very well in one context and just die off rapidly
Speaker 1: in another, and so the animals, the life we have
Speaker 1: here on Earth is a reflection of the selection pressure
Speaker 1: which comes from the environment in which we live, of course, right,
Speaker 1: But that goes also backwards in time. As you say,
Speaker 1: it's like it's telling story of the selection pressure over time.
Speaker 1: Every species that survives has survived through changing environments. Right,
Speaker 1: Things were colder and then they were hotter, and in in
Speaker 1: order to get here, you have to manage all of
Speaker 1: those changes somehow. It's your population grows and evolves and
Speaker 1: gains hair and lose his hair and all that kind
Speaker 1: of stuff. So I think it's really fascinating that not
Speaker 1: only does the earth itself tell the histories you like,
Speaker 1: dig down through the layers and see layers of rock
Speaker 1: and events that have happened through the history, but life
Speaker 1: on Earth also carries with it the history of its evolution. Right,
Speaker 1: As you say, why do you have this vestigial bid. Oh, well,
Speaker 1: we needed that millions of years ago, and we're still
Speaker 1: getting rid of it due to the new pressure. So
Speaker 1: I think that's super fascinating to look at the history
Speaker 1: of life on Earth, And to me, that's one of
Speaker 1: the most important things about science is answering this question,
Speaker 1: like how did we get here? What is the story
Speaker 1: of us? It tells us sort of how to live
Speaker 1: our lives and who we are, and in some sense,
Speaker 1: you know, as much as science can, it tells us
Speaker 1: why we're here at least what happened before we got here. Yeah,
Speaker 1: And I think it's so interesting because our life spans
Speaker 1: are relatively short compared to the universe, even compared to
Speaker 1: our own Earth. So our perception of what is stable, right,
Speaker 1: like what stable species are existence is warped by our
Speaker 1: you know, relatively short lifespans, and so we have this
Speaker 1: sense of things are as they are. Giraffes have always existed,
Speaker 1: We've always existed, but that's really not the case. And
Speaker 1: you know, when we look at some of these animals
Speaker 1: that have gone extinct and we think, like, wow, how
Speaker 1: could something that's strange have existed? Well, maybe hopefully if
Speaker 1: we're still alive, and like a thousand years. Potentially some
Speaker 1: species like the panda that's highly specialized to eat massive
Speaker 1: quantities of bamboo, which makes it very vulnerable to extinction
Speaker 1: if there's an environmental change, you know, we might look
Speaker 1: back and say, like, how could such a silly animal
Speaker 1: have existed where it's entire diet is dependent on bamboo
Speaker 1: and they're really bad at mating in captivity. I think
Speaker 1: we have this very narrow view in our own lifespan,
Speaker 1: so it is it becomes kind of fascinating when we
Speaker 1: zoom out and look at the history of the planet
Speaker 1: and you're like, oh, yeah, we're just like little babies,
Speaker 1: Like we're a little baby species. Yeah. And it's hard
Speaker 1: for us because we tend to think in time scales
Speaker 1: of hours, minutes, years, maybe centuries to understand processes that
Speaker 1: go on that are much much slower. You know, it
Speaker 1: took us a long time to appreciate how old the
Speaker 1: Earth was. The first hints we had that it might
Speaker 1: be billions of years old blew people's minds because it
Speaker 1: was just such a strange concept. Understanding geological processes like
Speaker 1: the formations of the continents and like glaciation work hard
Speaker 1: for people because we don't tend to think in sort
Speaker 1: of deep time, and yet we know that these processes
Speaker 1: really do shape and influence the nature of the world
Speaker 1: in which we live. And maybe most interesting and most
Speaker 1: dramatic are the cataclysmic events, right is where if the
Speaker 1: asteroid it hits somewhere different, maybe the dinosaurs wouldn't have
Speaker 1: wiped out. Or if dinosaur scientists had looked up in
Speaker 1: the sky and seen it coming and developed technology too diverted,
Speaker 1: you know, then maybe things really would be different. I
Speaker 1: love those moments when history could really take lots of
Speaker 1: different courses. Yeah, dinosaur Matt Damon and a dinosaur Jennifer
Speaker 1: Lawrence trying to figure things out. I wonder if the
Speaker 1: dinosaur version of that movie would have been any better. Yeah,
Speaker 1: I mean it is that. I do think about those
Speaker 1: cataclysmic events quite a bit, you know, just the our
Speaker 1: vulnerability of you know, as a single human, were relatively
Speaker 1: vulnerable in our little fleshy bodies, but then our planet
Speaker 1: also feels somewhat vulnerable just this like little paradise of
Speaker 1: being able to be alive on it in a pretty
Speaker 1: unforgiving universe. And then just that rock just traveling along
Speaker 1: randomly could just you know, spell the end for an
Speaker 1: entire planet of species. It's somewhat terrifying right to know
Speaker 1: that these rocks are out there, and if one of
Speaker 1: them falls into the gravity well of the Earth, it
Speaker 1: could end all life on Earth, or some lives on Earth.
Speaker 1: It certainly would not be a good day. And as
Speaker 1: we saw in the nineties, these kind of things do happen,
Speaker 1: like comic Shoemaker Levy, which came into the Solar System
Speaker 1: smashed into Jupiter, creating fireballs bigger than planet Earth. So
Speaker 1: this is not only something that happens than the deep
Speaker 1: history of time, it's something that could happen. We don't
Speaker 1: know when NASA is doing its best to track these asteroids,
Speaker 1: but beyond that, we wonder, like, is it possible to
Speaker 1: predict these events far in the future. Is there some
Speaker 1: sort of like deep time process sort of like glaciation
Speaker 1: or like formations of the continents which we can't yet
Speaker 1: imagine because it happens on a galactic scale, which is
Speaker 1: shaping these asteroid impacts, which is maybe creating patterns that
Speaker 1: we could understand, which we could use to predict, so
Speaker 1: we could know. Guys, we only got a million more
Speaker 1: years before the next wave of killer asteroids. Better start
Speaker 1: funding those spaceships. Yeah, I mean I'd like to know
Speaker 1: because if an asteroid's coming in like the next year,
Speaker 1: I know I can skip a dentist appointment. So don't
Speaker 1: bother saving for retirement, folks. So on today's episode, we'll
Speaker 1: be asking the question is there a pattern to major
Speaker 1: asteroid impacts on Earth? And is it gonna benefit us
Speaker 1: to know this or just make us scared? You can
Speaker 1: short the stock market because you know all life on
Speaker 1: Earth is going so put everything in gold, folks. This
Speaker 1: is now a financial investment podcast. I believe that's illegal.
Speaker 1: But also if the asteroid is made out of gold,
Speaker 1: maybe you shouldn't invest in it because then we will
Speaker 1: be inundated with gold and then also extremely dead. That's
Speaker 1: not actual financial advice. Don't sue me. So you're saying
Speaker 1: that when we're wiped out and the Ladybug civilization rises
Speaker 1: up in our ashes, they're going to find so much
Speaker 1: gold everywhere. It's just gonna be like they're paving their
Speaker 1: streets in gold. Yeah, they're building their little Ladybug toilets
Speaker 1: out of gold. So what is Ladybug Donald Trump then
Speaker 1: going to do to make his bathroom extra bling well
Speaker 1: as usual. I was wondering if people out there had
Speaker 1: thought about if there was a pattern to major asteroid
Speaker 1: impacts and if there was something we could do to
Speaker 1: predict it. So thanks very much to everybody who participates
Speaker 1: in these off the cuff answers on the virtual street.
Speaker 1: If you would like to play this role for future episodes,
Speaker 1: please don't be shy right to me. Two questions at
Speaker 1: Daniel and Jorge dot com. So think about it for
Speaker 1: a moment before you hear these answers. Do you think
Speaker 1: there's a pattern to major asteroid impacts on Earth? Here's
Speaker 1: what some listeners had to say. I think I heard
Speaker 1: once it's like every thirty million years or something like that,
Speaker 1: there's this massive asteroid that crashes into Earth and basically
Speaker 1: wipes off all of the life on it. But I
Speaker 1: don't really know. I don't think there's like any sort
Speaker 1: of pattern to the distribution of asteroids. Those pods will
Speaker 1: collide with Earth at some point in the post island,
Speaker 1: so I don't think that there's a pattern of asteroid impacts.
Speaker 1: It's orbital mechanics. Anything more than two bodies is pretty
Speaker 1: chaotic and random, but I do think that there is
Speaker 1: a governing frequency that decreases over time, so as our
Speaker 1: Earth and Solar system get older, um impacts become less frequent.
Speaker 1: I think you get some patterns with asteroids, because wouldn't
Speaker 1: you get kind of like a cyclic almost resonant wave
Speaker 1: function if you spend things up on a macro scale,
Speaker 1: just since everything is orbiting, you could kind of mathematically
Speaker 1: predict when it might fling stuff in our direction. I
Speaker 1: don't know, well, hopefully if it's a pattern, it will
Speaker 1: show us that no major asteroid will either art in
Speaker 1: the future or until we are able to defend ourselves
Speaker 1: properly to define them, because probably this is the most
Speaker 1: difficult thing to just to see them in time for
Speaker 1: us to prepare to do something about it. I really
Speaker 1: do agree with the person who says that they hope
Speaker 1: that no asteroid hits Earth until we're ready to defend ourselves,
Speaker 1: because I feel like if we just learn like in
Speaker 1: a hundred years we're going to get a big one,
Speaker 1: but we have no way to do anything about it,
Speaker 1: that would be a bit of a bomber. I'll be
Speaker 1: honest with you, what do you mean we have no
Speaker 1: way to do anything about it. You have no faith
Speaker 1: in physicists and engineers to save the planet. It depends
Speaker 1: on how fast you guys are at writing grant proposals.
Speaker 1: I guess. So, if we've got an asteroid coming in
Speaker 1: a hundred years, maybe you can do it. But if
Speaker 1: it's like five weeks, do you think we could do
Speaker 1: something about it? You know, the key really is to
Speaker 1: discovering these things early on. If you see far in
Speaker 1: advance that it's coming, that it only needs a little
Speaker 1: bit of a push to not hit the Earth. It's
Speaker 1: sort of like if somebody's firing a sniper shot from
Speaker 1: five miles away, the tiniest little deviation in the direction
Speaker 1: of their rifle means they're going to miss their target.
Speaker 1: And so if you can figure out that this thing
Speaker 1: is going to come in a hundred years, then even
Speaker 1: the faintest little push, you could throw a rock at it,
Speaker 1: or is that it with a laser, and they would
Speaker 1: miss the Earth. You only have a few weeks of notice.
Speaker 1: Then it's much much harder. You have to give it
Speaker 1: a much bigger push. But actually, you know, this week,
Speaker 1: as we record this episode, NASA is doing an amazing
Speaker 1: test the dart probe is out there and it's about
Speaker 1: to push on an asteroid to see if this works.
Speaker 1: Can we actually find an asteroid and push on it
Speaker 1: and see if we can change its direction. This is
Speaker 1: not one that NASA thinks is going to hit the Earth.
Speaker 1: This is just an experiment to see is it possible
Speaker 1: to change its trajectory. Also, fortunately it's not one that
Speaker 1: NASA thinks is going to hit the Earth after they
Speaker 1: change its traject Right. I was about to say, I
Speaker 1: really hope they double checked their math and their units,
Speaker 1: because that would be a heck of all whoop. See
Speaker 1: that is actually something people worry about developing these tools
Speaker 1: that can affect the future of the human race. Like
Speaker 1: if you can now aim asteroids, then you know some
Speaker 1: super billain might decide to use that to threaten Earth
Speaker 1: with asteroids. Right. Another direction people are working on is
Speaker 1: zapping these things with lasers. That sounds like science fiction,
Speaker 1: but you can get a powerful enough laser and zap
Speaker 1: one side of the asteroid, then you can like vaporize
Speaker 1: some of the rock and the ice and it can
Speaker 1: give it a sideways push so that it doesn't hit
Speaker 1: the Earth. There, people in Santa Barbara working on these
Speaker 1: kind of super lasers. But also that does make me
Speaker 1: worry about you know, like other applications of supers well,
Speaker 1: like you're not firing this laser from Earth right because
Speaker 1: I would imagine you'd scorch a few birds and maybe
Speaker 1: a few planes if you did that. I don't think
Speaker 1: they even have a prototype of this laser so far.
Speaker 1: It's still in the exploratory studies. But there are a
Speaker 1: range of solutions, and we actually have a whole podcast
Speaker 1: episode about how to defend the Earth from asteroids, including
Speaker 1: gravity tractors and laser beams and giving them a push.
Speaker 1: It all depends on what the thing is made out of,
Speaker 1: Like if it's a pile of rubble, it's kind of
Speaker 1: hard to give it a push, or if it's a
Speaker 1: big ball of ice, it's good to zap it with
Speaker 1: a laser, And also really depends on spotting it early
Speaker 1: and understanding where it comes from. We're gonna take a
Speaker 1: quick break, but when we come back, we're going to
Speaker 1: talk about the source of these deadly rocks that might
Speaker 1: wipe out life on Earth, whether or not the data
Speaker 1: suggests there are coming in a pattern, and what we
Speaker 1: can do about it. So like what angle I should
Speaker 1: keep my umbrella at. Essentially how many umbrellas you need
Speaker 1: to buy? Actually, all right, we're back and we're talking
Speaker 1: about whether there's a pattern to asteroid impact on Earth.
Speaker 1: We have some pretty strong evidence that about sixty five
Speaker 1: million years ago there was a huge impact or it
Speaker 1: was something like five to ten kilometers wide, and it
Speaker 1: struck the Earth the twenty thousand miles per hour. You
Speaker 1: might wonder, like, why is it going so fast? Well,
Speaker 1: most of the stuff out there in the Solar System
Speaker 1: is whizzing around the Sun pretty fast. It's like we're
Speaker 1: all the fast land on the freeway, and if somebody
Speaker 1: comes at you at that speed, it's going to be
Speaker 1: pretty fast. But also, the Earth has a lot of gravity,
Speaker 1: so once something comes even near the Earth and then
Speaker 1: falls to the surface, it gets accelerated by the Earth.
Speaker 1: The Earth is like pulling it in, so by the
Speaker 1: time it hits the ground, it has a lot of velocity.
Speaker 1: And this asteroid impact, we think, wiped out about thirty
Speaker 1: of the species on Earth at the time, including many
Speaker 1: of the dinosaurs. Yeah, I mean, I think one of
Speaker 1: the things that is important to remember is that this
Speaker 1: did not just wipe out the dinosaurs, only it wiped
Speaker 1: out anything and everything that was around, like a good
Speaker 1: number of them, the things that ended up surviving. It
Speaker 1: was not like a dinosaur seeking asteroid that targeted the
Speaker 1: dinosaurs specifically. It just targeted anything that was not able
Speaker 1: to survive. The fallout of what happened after the asteroid hit.
Speaker 1: I mean, I'm sure there was a good amount of
Speaker 1: death and the immediate aftermath of the asteroid, but a
Speaker 1: lot of it was sort of both long and slow
Speaker 1: drawn out extinction, and the exact causes of it aren't
Speaker 1: precisely known. It's hard to find really accurate evidence of
Speaker 1: what exactly happened. But you know, there are a lot
Speaker 1: of theories about, you know, the ecosystems collapsing because of
Speaker 1: the you know, massive amount of debris that cut out
Speaker 1: the sun, and of course you don't have as much
Speaker 1: vegetation and so you don't have as many big herbivores,
Speaker 1: and then you don't have as many big carnivores. So
Speaker 1: like that. It basically, you know how these ecosystems are
Speaker 1: like these Jenga towers and you pull one thing out
Speaker 1: and it can collapse. Well, like this asteroid hitting is
Speaker 1: like a throwing a tennis ball at the Jenga tower,
Speaker 1: and so only the things that were hardy enough, you know,
Speaker 1: typically quite small as well, because they didn't require as
Speaker 1: much food, we're able to survive. And not all the
Speaker 1: dinosaurs one extinct, like we still have birds. Birds are
Speaker 1: the surviving dinosaurs of this period, and they were small
Speaker 1: enough that they were able to sort of escape the
Speaker 1: uh starvation of these larger dinosaurs that had much more
Speaker 1: intensive dietary needs. And that's, like, I think, to me,
Speaker 1: is one of the more compelling theories of what happened. Yeah,
Speaker 1: it's important to realize, as you say, that these are
Speaker 1: not like dinosaurs seeking asteroids that didn't come and then
Speaker 1: like hunt down all the dinosaurs and kill them one
Speaker 1: by one. It really is a lot of the death
Speaker 1: probably came from the change in the environment and all
Speaker 1: this stuff is now up in the atmosphere and you're
Speaker 1: blocking the sun's light and so, as you say, ecosystems
Speaker 1: react to that, and now you have to survive in
Speaker 1: a pretty new world. I don't know if anybody out
Speaker 1: there it was a fan of the Dinosaurs sitcom aired
Speaker 1: I think in the eighties and nineties, but the theories.
Speaker 1: Finale of that episode actually features like basically an Aster
Speaker 1: Royd winter where they're all hovering in their house as
Speaker 1: the snow comes down and they're not expecting to see
Speaker 1: the sun for years. It's sort of a bleak ending
Speaker 1: to a comedy series. It was a huge bummer. I
Speaker 1: think it was sort of a cautionary tale because it
Speaker 1: was something about some dino corporation caused this to happen,
Speaker 1: and so it was I think supposed to be an
Speaker 1: environmental message about not destroying our own planet with global
Speaker 1: warming or or whatever you know potential ramifications of destroying
Speaker 1: our environment would be. And it wasn't a comedy. It
Speaker 1: was like this lighthearted comedy with these big puppet dinosaurs
Speaker 1: and like, you know, a dinosaur baby that would hit
Speaker 1: the father with a frying pans. So it was as
Speaker 1: if The Simpsons ended on basically a nuclear war and
Speaker 1: everyone dies. How inappropriate to combine you know, hard hitting
Speaker 1: science with ridiculous jokes. I mean, you choose that kind
Speaker 1: of venue for talking about as a serious topic. Anyway,
Speaker 1: let's keep making some jokes about how all the dinosaurs
Speaker 1: were wiped out millions of years ago. But I think
Speaker 1: it's important to understand where these things come from. Like,
Speaker 1: these rocks don't just appear in space and get dropped
Speaker 1: on the Earth. These are not like malevolent aliens. As
Speaker 1: far as we know, these are parts of our Solar system.
Speaker 1: When big misimpression is that these rocks might come from
Speaker 1: really deep space, like from outside our Solar system to impact,
Speaker 1: that's actually really quite rare because our star is pretty
Speaker 1: far away from other stars. You know, there's many light
Speaker 1: years between us and the next star, and many many
Speaker 1: more between most stars. So there's only been a few
Speaker 1: examples of times when we've even seen a rock come
Speaker 1: from another Solar system and passed through hours like Omamua.
Speaker 1: Most of the times when we're thinking about impacts on Earth,
Speaker 1: we're talking about our own neighbors. We're talking about sources
Speaker 1: in the Solar system. Isn't that the thing with like
Speaker 1: murders and stuff, where stranger danger is pretty overly hyped
Speaker 1: and it's usually someone you know that murders you. I
Speaker 1: guess it's the same thing with asteroids. It's the asteroid
Speaker 1: you know, your neighbor, that comes and destroys your planet.
Speaker 1: Another good example of inappropriate humor, Katie wow Now we're
Speaker 1: now we're joking about murders. I'm going to go to
Speaker 1: podcast jail. No, But you're exactly right. And the thing
Speaker 1: to understand is that the Solar System, like life on Earth,
Speaker 1: has not stopped developing. It's a continuous, ongoing process. Solar
Speaker 1: system is about four and a half billion years old,
Speaker 1: and it's started from some huge cloud of gas and
Speaker 1: dust and little bits of rock left over from the
Speaker 1: death of other stars and coalesced into these planets and
Speaker 1: all of these bits. But it's a dynamic, ongoing process.
Speaker 1: And as we study our Solar system and compare it
Speaker 1: to other solar systems, we understand that lots of things
Speaker 1: are changing through that history of the Solar System. Planets
Speaker 1: might even be changing position. We think that Jupiter amount
Speaker 1: have formed in the outer part of the Solar System
Speaker 1: and then taken a trip to the inner Solar System
Speaker 1: before being pulled back out by Saturn into the outer
Speaker 1: Solar System again. So don't think of the Solar system
Speaker 1: is like a static place where it's finished and it's
Speaker 1: going to be like this forever. It's still ongoing. And
Speaker 1: that goes double for the little bits, not just the planets,
Speaker 1: but the extra little rocks that didn't find their way
Speaker 1: into a big planet. So we know, for example that
Speaker 1: between Mars and Jupiter there's the asteroid belt. Right, These
Speaker 1: are a bunch of little rocks that are not part
Speaker 1: of any planet. And it's not just between Mars and Jupiter.
Speaker 1: There are actually two blobs that are in Jupiter's orbit,
Speaker 1: and like in the same ellipse where Jupiter goes around
Speaker 1: the Sun is a blob that goes ahead of them
Speaker 1: and a blob that goes behind them. That I think
Speaker 1: is really cool. It shows you sort of why the
Speaker 1: asteroids exist exist because of Jupiter's gravity. Jupiter's like this
Speaker 1: huge bully in the outer Solar System. It wasn't for
Speaker 1: Jupiter these rocks might coalesce into a planet. We did
Speaker 1: an episode recently about like why planets get rings versus moons,
Speaker 1: and the answer there was because of the tidal forces
Speaker 1: of the planets, pulling those moons apart into rings if
Speaker 1: they're too close. This is sort of a similar thing.
Speaker 1: Jupiter is tugging on all of these guys, preventing them
Speaker 1: from well lessen into a single larger thing. So you
Speaker 1: have this huge collection of rocks. But again that's not static.
Speaker 1: It used to be in the much earlier times in
Speaker 1: the Solar System that the asteroid belt was much much richer,
Speaker 1: There was much more mass. A lot of that has
Speaker 1: gotten lost because it's a little bit unstable. Things fall
Speaker 1: in towards the Sun or get knocked out of the
Speaker 1: asteroid belt by collisions or just by Jupiter's gravity. What
Speaker 1: causes something to get knocked out of stability? So you
Speaker 1: have this asteroid built, what is the impetus for one
Speaker 1: of these asteroids just deciding to go like, well, see
Speaker 1: it and fall into the Sun. Think about it the
Speaker 1: other direction. What do you have to do in order
Speaker 1: to survive over billions of years? You have Jupiter's gravity
Speaker 1: tugging at you, if all the other planets also tugging
Speaker 1: at you even less, and of course the Sun. In
Speaker 1: order to survive you have to somehow balance all of
Speaker 1: those things for billions of years. So you start out
Speaker 1: with a huge number of rocks, and nobody has organized
Speaker 1: these right there, just sort of like out there in
Speaker 1: the Solar System. They formed gravitationally, and most of them
Speaker 1: are just not on trajectories that are going to survive.
Speaker 1: They're gonna get tugged by Jupiter, or they're gonna get
Speaker 1: yanked by Mars, or they're gonna feel Saturn's pull, and
Speaker 1: then eventually they're gonna fall into the Sun or into
Speaker 1: another planet. So it requires like a really delicate balance
Speaker 1: of all of those gravitational factors in order to survive
Speaker 1: this long, and as time goes on, you're less and
Speaker 1: less likely to survive because you know, it's really chaotic.
Speaker 1: Like you can orbit a single object pretty stable for
Speaker 1: a long long time, you're just feeling gravity towards it.
Speaker 1: You have the right angle you can orbit. Now you
Speaker 1: add another object in the Solar System, another thing with
Speaker 1: heavy gravity, becomes much more complicated to keep a stable orbit.
Speaker 1: Like the Earth, for example, its orbit is constantly being
Speaker 1: tweaked by Jupiter and by Saturn, these tiny little tugs,
Speaker 1: and so it's hard to find a path which is
Speaker 1: going to be stable over billions of years. It's amazing, frankly,
Speaker 1: that any of these asteroids were able to survive this
Speaker 1: fairly chaotic gravitational system that long. I mean that kind
Speaker 1: of sounds similar to evolution, where you know, the rule
Speaker 1: is simple. If you survive, you survive, and if you don't,
Speaker 1: you get tossed into the Sun or pulled into the Sun. Yeah.
Speaker 1: The difference here is that there's no way to reproduce, right,
Speaker 1: there's no like way to replenish these meteors that we
Speaker 1: know that we know of exactly unless like two planets
Speaker 1: collide and create a lot of debris. But our model
Speaker 1: of the asteroid belt is that it's like point one
Speaker 1: percent of its original mass. The first hundred million years
Speaker 1: of the Solar System were pretty chaotic collisions all the time,
Speaker 1: and things were falling out of it. So the asteroid
Speaker 1: belt we think now is much much less mass than
Speaker 1: it used to be. In total, if you took like
Speaker 1: all the asteroids and the asteroid belt and add them up,
Speaker 1: it'd be less than five percent of the mass of
Speaker 1: our moon. So there's not actually that much stuff out there.
Speaker 1: Is That good news for us? Because the more stuff,
Speaker 1: it seems like, the more likely we're going to get
Speaker 1: hit by that stuff. That's very good news for us.
Speaker 1: We want fewer asteroids because each one is like a bullet, right,
Speaker 1: Any of these things, if they're bigger and like ten
Speaker 1: kilometers or so and they hit the Earth, that's an
Speaker 1: extinction event, right, that's really catastrophic. Some of these guys
Speaker 1: are huge. Like there's a dwarf planet in the asteroid belt,
Speaker 1: it's called Series, and it's nine fifty kilometers in diameter, right,
Speaker 1: that would just obliterate the surface of the Earth completely.
Speaker 1: That sounds pretty serious. So it seems like earlier on,
Speaker 1: like we probably had more asteroid collisions near Earth, because
Speaker 1: like the Moon has a bunch of craters, But has
Speaker 1: the Moon been hit by asteroids more recently? Was that
Speaker 1: like debris from Earth hitting the Moon? Why do we
Speaker 1: have more craters Like that seemed to be old than
Speaker 1: we are currently experiencing in terms of getting hit by
Speaker 1: space rocks. Yeah, there's a few things going on there.
Speaker 1: It's true that we have fewer space rocks hitting things
Speaker 1: now than we used to in the very early days
Speaker 1: of the Solar System, just because there are fewer and
Speaker 1: we sort of run out and the trend is towards
Speaker 1: things coalescing into larger objects. So we just have fewer
Speaker 1: of these rocks, which means fewer impacts. But there still
Speaker 1: are a lot of impacts. And if you look at
Speaker 1: the Moon, there's a very rich history there of impacts
Speaker 1: and you can see, for example, really big craters that
Speaker 1: you can tell are old with smaller craters inside them,
Speaker 1: and so you can use that to tell like which
Speaker 1: ones happened first because of the small crater it happened first,
Speaker 1: the big one would have obliterated it. So you can
Speaker 1: tell the sort of like the layers of cratering there,
Speaker 1: and you can use that to try to reconstruct something
Speaker 1: about the history of cratering on the Moon. But yeah,
Speaker 1: there was definitely more cratering earlier on. And remember that
Speaker 1: the Moon doesn't really have much of an atmosphere, has
Speaker 1: almost no atmosphere. We just did an episode about the
Speaker 1: Moon's atmosphere. It's like a few molecules per cubic centimeter,
Speaker 1: whereas the Earth is like ten to the nineteen the
Speaker 1: molecules per cubic centimeter, and that's a huge shield. Any
Speaker 1: rock that hits the Moon is going to cause a crater,
Speaker 1: whereas the rock that hits the Earth, if it's not
Speaker 1: big enough, is going to burn up in our atmosphere
Speaker 1: and we're not going to see it. So every surface
Speaker 1: of the Solar System is constantly getting bombarded by smaller
Speaker 1: rocks and sometimes bigger ones Earth. We don't often notice
Speaker 1: that because our atmosphere protects us, but a big enough
Speaker 1: one is definitely going to make it to the surface
Speaker 1: of the Earth and do some damage. Well, I want
Speaker 1: to hear about how we can predict whether one of
Speaker 1: these big ones are gonna hit us, But I think
Speaker 1: first I'm going to take a quick break to hide
Speaker 1: under the bed a little bit. So we've talked about
Speaker 1: how there is a lot of asteroid activity, that there's
Speaker 1: a lot of randomness and chaos to the movement of asteroids,
Speaker 1: like from say like the asteroid belt to falling into
Speaker 1: the Sun. So it seems like there's so much randomness
Speaker 1: it would be like really hard to predict if one
Speaker 1: of the these guys would come and hit us. It
Speaker 1: does seem like a lot of the process is random, right,
Speaker 1: Like what makes an asteroid hit the Earth or not
Speaker 1: hit the Earth. It does seem like it just needs
Speaker 1: to get tugged the right way gravitationally and then end
Speaker 1: up on a path. You know, for those of you
Speaker 1: out there who are more anxious, NASA is doing their best.
Speaker 1: They have a bunch of telescopes now tracking these things,
Speaker 1: and they think they know where all of the big
Speaker 1: asteroids are, the ones that might do any damage to
Speaker 1: the Earth. They can't find all the asteroids because they
Speaker 1: get to be pretty small, but the bigger ones, and
Speaker 1: especially the shinier ones, they've had a lot of opportunities
Speaker 1: to see these things because the asteroid belt is pretty close,
Speaker 1: so we get lots of chances. The things that are
Speaker 1: harder to predict are the things that come from further
Speaker 1: out in our own solar system. These seem a little
Speaker 1: bit more random and harder to anticipate because they're on
Speaker 1: longer time scales, and those are things like comets. So
Speaker 1: out past the asteroid belt, that's something called the Kuiper
Speaker 1: Belt is now past Neptune. It's like thirty a U
Speaker 1: out there, and instead of just being rock, these things
Speaker 1: are icy rocks out past the snow line, and so
Speaker 1: it's cold enough for vapor to coalesce into ice. These
Speaker 1: chunky ice balls can also get disrupted and then fall
Speaker 1: towards the inner Solar system, and that's what we typically
Speaker 1: call a comet to have a tail, because this ice
Speaker 1: is getting boiled off as they get closer and closer
Speaker 1: to the Sun, and the Kuiper Belt is responsible for
Speaker 1: what we call short period commets, ones that loop around
Speaker 1: every two hundred years or so. That doesn't seem very short, right.
Speaker 1: The problem though, is that if it only comes every
Speaker 1: two hundred years, and we've only had like telescope technology
Speaker 1: for a few hundred years, and we don't get very
Speaker 1: many chances to see these things and like understand their
Speaker 1: orbit and predict very well whether they're going to hit
Speaker 1: the Earth. How much lead time would we have, like
Speaker 1: from first spotting a comment to it making contact with Earth,
Speaker 1: Like how fast could it move from when we could
Speaker 1: first feasibly see it too when it would hit us.
Speaker 1: It's a great question, and we have an answer to
Speaker 1: that because it's happened right Commas Shoemaker levee, which hit
Speaker 1: Jupiter in the nineties. We knew that was going to
Speaker 1: hit but only a few months in advance because it
Speaker 1: comes from pretty far out in the Solar system where
Speaker 1: it's hard to track, and then as it comes in
Speaker 1: people can calculate its trajectory and see where it's going
Speaker 1: to loop around this time, and that's how we knew
Speaker 1: it was going to hit Jupiter. And so some of
Speaker 1: these things can come sort of out of the darkness
Speaker 1: and surprise us. The scary thing is that there are
Speaker 1: also long period comets, these things from the ord cloud,
Speaker 1: and there might be like trillions of things out there,
Speaker 1: much much further out, very loosely held by the Sun's gravity,
Speaker 1: and these things can give comments that have really long
Speaker 1: periods five hundred years, a thousand years, maybe even longer,
Speaker 1: you know, looping through our solar system once every million years.
Speaker 1: And so this is another source of potential killers. And
Speaker 1: one issue is that because they come from so far out,
Speaker 1: when they come in, they're gonna be moving very very fast,
Speaker 1: which makes them hard to predict and also very very dangerous.
Speaker 1: So comets are harder to predict than asteroids and also
Speaker 1: faster moving, so they're really something to be more worried
Speaker 1: about than asteroids. Well I hate that, so thank you
Speaker 1: for that, so ignoring that kind of mortal peril. Are
Speaker 1: we able to predict asteroids better than we can predict
Speaker 1: comments like ore? Is there some science to understanding when
Speaker 1: asteroids would hit us? There is some science there, but
Speaker 1: we're not great at predicting asteroids more than like a
Speaker 1: couple hundred years out. The more measurements you have of
Speaker 1: an object, the better you can predict its trajectory. If
Speaker 1: you've seen an asteroid a hundred times or a thousand times,
Speaker 1: then you have a good sense of exactly what direction
Speaker 1: it's going in and what its velocity is, and you
Speaker 1: can predict pretty well where it's going to go. In
Speaker 1: the end, it always becomes chaotic because there's so many
Speaker 1: things in the Solar System that can tug on it.
Speaker 1: It makes it hard to predict. Comments are harder if
Speaker 1: you don't have much data, if you've only seen it once,
Speaker 1: or if you've never seen it before, where it's just
Speaker 1: entering the Solar system, and you know, the things that
Speaker 1: trigger asteroid or comets to fall into the Earth are
Speaker 1: these gravitational tugs. Right the Solar system, like left to itself,
Speaker 1: is pretty stable. There's some gravitational chaos internally, but something
Speaker 1: that we need to think about our effects from other
Speaker 1: Solar systems. You know, the Sun is moving through the
Speaker 1: galaxy and right now it's pretty far from other stars,
Speaker 1: but as time goes on, it gets closer to other
Speaker 1: stars and further from other stars. It's sort of like
Speaker 1: swimming through an ocean of the galaxy. And if you
Speaker 1: have these things out there in the or cloud that
Speaker 1: are sort of like very tenuously held by the Sun.
Speaker 1: Then a little tug from something else out there might
Speaker 1: not get out of the stable orbit it's been in
Speaker 1: for billions of years and send it rocketing towards the
Speaker 1: inner Solar System. We do have ways to predict things
Speaker 1: that's not always completely accurate, but it's based on like probabilities.
Speaker 1: So like if you have a coin and you're flipping it,
Speaker 1: you can't really with complete accuracy predict whether it's going
Speaker 1: to be heads or tails, but you have an idea
Speaker 1: of if you flip it a bunch of times that
Speaker 1: you know roughly fifty percent at the time it should
Speaker 1: be heads and fifty percent of the time it should
Speaker 1: be tails. So do we have a similar thing when
Speaker 1: it comes to asteroids, Like maybe we can't precisely predict
Speaker 1: when an asteroid would hit us, but we have an
Speaker 1: idea of the rough probability of asteroid hitting us over
Speaker 1: the history of our planet. We can look back into
Speaker 1: our history and try to see if there are patterns
Speaker 1: there to see if there is a periodicity. But before
Speaker 1: we do that, it's fun to think about, like what
Speaker 1: might be causing that periodicity, Like are there even conceivably
Speaker 1: theories that might generate that kind of pattern, because a
Speaker 1: pattern means that there's something underlying happening. There's some like
Speaker 1: very slow process which is grinding forward, which is changing
Speaker 1: the nature of the environment in a way that's predictable. Right.
Speaker 1: That's periodic, the way like the seasons are periodic. Because
Speaker 1: of the way the Earth goes around the Sun, people
Speaker 1: have looked for these kinds of things in our galaxy,
Speaker 1: like periodic events that happen over tens of millions of
Speaker 1: years that might trigger asteroids and comments to hit the
Speaker 1: Earth on some sort of time scale. And there's a
Speaker 1: couple of candidates. One is sort of plausible and the
Speaker 1: other one is kind of crazy and dramatic. The one
Speaker 1: that's sort of plausible is that the Sun does have
Speaker 1: a sort of thirty million year cycle in the galaxy.
Speaker 1: So the Sun is going around the center of the galaxy,
Speaker 1: and it takes a couple of hundred million years to
Speaker 1: orbit the center of the galaxy. That's like one galactic year.
Speaker 1: But the Sun is also wiggling sort of up and
Speaker 1: down through the galactic plane. So if you imagine the
Speaker 1: Sun like going around the center of the galaxy, it's
Speaker 1: also going up and down above and below the galactic
Speaker 1: plane as it does that, and that happens about every
Speaker 1: thirty million years. We pass through the sort of plane
Speaker 1: at the center of the galaxy and then go below
Speaker 1: it and then come back up thirty million years later. So,
Speaker 1: like I've always kind of thought of the Sun as
Speaker 1: this pretty stable, massive or but now I'm thinking of
Speaker 1: it like this rubber ducky that is like circling the
Speaker 1: drain of the bathtub, kind of bobbing under the water
Speaker 1: and over the water exactly. And as it moves through
Speaker 1: the galaxy, its environment changes, we get further and closer
Speaker 1: to other stars. The center of the galaxy. The galactic
Speaker 1: plane is definitely the densest part of the galaxy. And
Speaker 1: so it's not inconceivable that that kind of process my
Speaker 1: trigger comets or Kuiper Belt objects out of their otherwise
Speaker 1: stable orbit give it just the right kind of tug
Speaker 1: that might cause them to fall towards the center of
Speaker 1: the Solar system. So that's the more plausible theory. Then
Speaker 1: there's a theory that was spread in a popular book
Speaker 1: recently about whether dark matter killed the dinosaurs. This is
Speaker 1: a book written by a couple of theorists at Harvard,
Speaker 1: and they suggest that dark matter, which is this invisible
Speaker 1: matter that we know is out there but we don't
Speaker 1: really understand very much. That we know that there's much
Speaker 1: more of it than there is normal matter, and we
Speaker 1: think that it's shaped sort of the whole structure of
Speaker 1: the galaxy. They imagine that dark matter might coalesced into
Speaker 1: sort of like a disk, like a dark frisbee. Yeah,
Speaker 1: like a big dark frisbee. And when the Sun passes
Speaker 1: through this dark matter disc that maybe it's the dark
Speaker 1: matter that's tugging on the things in the outer Solar
Speaker 1: System and then knocking them in towards our safe little garden.
Speaker 1: Is there any evidence for this? So is there any
Speaker 1: evidence for this? You know, this is just a fun
Speaker 1: speculative theory. These two Harvard theorists came up with a
Speaker 1: theory of dark matter that would generate this kind of
Speaker 1: disc and then they went hunting to see if there
Speaker 1: was evidence in the history on our planet for some
Speaker 1: sort of periodicity, so that would be like an explanation
Speaker 1: for that. We don't have any direct evidence of the
Speaker 1: dark matter frisbee existing at all. It's just like another
Speaker 1: idea that might generate a sort of periodic tug on
Speaker 1: the Solar system that would create it. If indeed there
Speaker 1: is any periodicity in the asteroid impacts on Earth, it
Speaker 1: sounds like a very convenient scapegoat to me, Like if I,
Speaker 1: you know, knock over a vase, I'm like, well, hey,
Speaker 1: it's that dark matter, frisbee. You know how it is exactly.
Speaker 1: And so now I think it's time to answer your
Speaker 1: question from a few minutes ago, which is is there
Speaker 1: actually any evidence can we look back on the history
Speaker 1: on Earth and see a pattern of strikes, because you know,
Speaker 1: one good way to predict the feature is of course
Speaker 1: to look at the past and to see if this
Speaker 1: has happened at regular intervals in the past. And this
Speaker 1: is challenging, right because people weren't around, we've not been
Speaker 1: doing astronomy for like hundreds of millions of years to
Speaker 1: take this kind of data. But the sort of two
Speaker 1: categories of evidence that people have looked at to see
Speaker 1: if there are patterns. One is biological and the other
Speaker 1: is geological. So first people look at like the history
Speaker 1: of life on Earth, and they look at the fossil
Speaker 1: record for extinctions, and there are a lot of them.
Speaker 1: You know, if you look back in the history of
Speaker 1: life on Earth is many times when you've had massive
Speaker 1: dieots and big decreases in the diversity of life on Earth. Yeah, yeah,
Speaker 1: you have these like bottleneck events you can look at,
Speaker 1: you know, these kind of genetic because it's like not
Speaker 1: just in terms of you know, you'll have a massive
Speaker 1: dump of fossils that you can look at and that
Speaker 1: are kind of layered and so you can see like
Speaker 1: where you get these uh, these basically evidence of all
Speaker 1: these animals dying. You have interesting sort of genetic bottleneck
Speaker 1: where you can see evidence of mass die offs. I
Speaker 1: think we have this sort of nice notion that these
Speaker 1: mass extinctions don't really happen because we have not really
Speaker 1: been direct witnesses to a mass extinction and our human
Speaker 1: species lifespan. But yeah, they do happen with you know,
Speaker 1: some regularity, not too often, but it's something that it's
Speaker 1: hard to think of happening to us because you know,
Speaker 1: we like very much being alive on the planet. But yes,
Speaker 1: it does happen exactly, and sometimes these processes only happen
Speaker 1: in deep time or there's not things that we witness
Speaker 1: day to day or year to year, but they still
Speaker 1: are part of the larger cycle of life on Earth.
Speaker 1: You just might not have been paying attention long enough
Speaker 1: to notice. And so you know, sixty five million years
Speaker 1: ago there was a big die off, like to the species.
Speaker 1: Two fifty million years ago there was a huge die off.
Speaker 1: And the boundary between the Permian and Triassic period that
Speaker 1: I think people still don't even really understand, something like
Speaker 1: fifty percent of species on Earth died out. And if
Speaker 1: you look at like over time when have species died out?
Speaker 1: And you do see these spikes and you wonder like
Speaker 1: is there a pattern there? So people have done a
Speaker 1: statistical analysis to see like can you fit this to
Speaker 1: a periodic function? Is there like a gap between these
Speaker 1: peaks that's pretty regular or not. The way to do
Speaker 1: this mathematically is something called a Furrier analysis. For those
Speaker 1: you like signal processing nerds out there, it's basically like
Speaker 1: taking a sound and decomposing it into frequencies. You listen
Speaker 1: to Bob Dylan, for example, and you can lower the base,
Speaker 1: or you can raise the trouble, or you know, you
Speaker 1: can change the frequencies. That's because all sound is actually
Speaker 1: built up of a bunch of different frequencies, and you
Speaker 1: can decomposed sound into those frequencies and say Bob Dylan
Speaker 1: is more based than Lady Gaga or whatever. And so
Speaker 1: in the same way, you can take any distribution and
Speaker 1: you can break it down into basically sine waves and say, like,
Speaker 1: what frequencies are more common in this distribution. And when
Speaker 1: you do that and you look at the pattern of
Speaker 1: die offs biologically, you don't see much evidence. There's like
Speaker 1: maybe some weak evidence for periodic die offs every sixty
Speaker 1: million years or every hundred and forty million years. Really
Speaker 1: you don't see something every thirty million years, like this
Speaker 1: cycle that we talked about where the Sun goes in
Speaker 1: and out of the galactic plane that happens every thirty
Speaker 1: million years, But we don't see a die off every
Speaker 1: thirty million years. It doesn't look like life on Earth
Speaker 1: has been wiped out by an asteroid impact every thirty
Speaker 1: million years, right, So it doesn't seem like it's on
Speaker 1: an exact schedule, But it seems like there's also the
Speaker 1: chance that like it wouldn't happen every thirty million years,
Speaker 1: but you know the chance of it happening every thirty
Speaker 1: million years would slightly increase, but you would maybe skip
Speaker 1: a bunch of potential die offs, because just by increasing
Speaker 1: the chance of something doesn't guarantee that it's going to happen,
Speaker 1: Which seems like a really difficult analysis to make because
Speaker 1: we don't have, you know, that much time to work with,
Speaker 1: because like the Earth is not like the oldest thing
Speaker 1: in the universe. Yeah, don't understanding the fossil record and
Speaker 1: our ability to analyze this thing doesn't really go much
Speaker 1: further back than like five or six hundred million years
Speaker 1: after like the Cambrian explosion and that kind of stuff.
Speaker 1: But you're right, it could be sort of like every
Speaker 1: thirty million years we play Russian roulette and sometimes we
Speaker 1: win and sometimes we don't win. But then you would
Speaker 1: see that appearing, right, even if it didn't happen every time,
Speaker 1: you would see it appearing at that periodicity. It wouldn't
Speaker 1: have to happen every time for this analysis to reveal it.
Speaker 1: But you're right, Also, this is limited, like we don't
Speaker 1: have that many examples, and so it could be that
Speaker 1: it's there, we just haven't seen enough examples for it
Speaker 1: to sort of rise out of the data statistically. But
Speaker 1: currently when we look at the data, we can't say
Speaker 1: that there's statistical evidence for any sort of periodicity in
Speaker 1: the die off patterns of life on Earth. There's too
Speaker 1: much noise, uh, and there's not really much evidence of
Speaker 1: a signal. And maybe if we had many billions of
Speaker 1: years to work with, we could have better data, but
Speaker 1: we don't have that. And sadly, crocodiles and celia counts
Speaker 1: and some of these really old species are not really
Speaker 1: good at data collections. So exactly, the fascinating thing is
Speaker 1: that all of these events, somebody was there, you know,
Speaker 1: some life was there, some eyeball was around seeing these
Speaker 1: things happen. Just like all of human history, though most
Speaker 1: of it's forgotten, all of it was witnessed, right, there
Speaker 1: was somebody who knew exactly what happened to humans twenty
Speaker 1: thousand years ago. It's just all those people are dead
Speaker 1: and they didn't write it down, and so all that
Speaker 1: information is now lost. That's so frustrating. Sometimes some scientists
Speaker 1: have turned to the interior of the Earth to try
Speaker 1: to understand if there's evidence in the geologic record for
Speaker 1: these impact, not just like did enough species die off,
Speaker 1: because you know, maybe the asteroid hit, but it just
Speaker 1: didn't cause a big die off. So instead they've looked
Speaker 1: at like the Earth itself to see if there's evidence
Speaker 1: for these impacts. And these guys were interested not just
Speaker 1: in asteroid impacts, but also in slow geologic events that
Speaker 1: could have caused die offs from within the Earth. Like
Speaker 1: what if there's some crazy process inside the Earth that
Speaker 1: causes supervolcanoes every fifty million years that causes a die
Speaker 1: off or some other very like slow process that bubbles
Speaker 1: up every x million years and we just haven't understood
Speaker 1: it yet. You know, we've definitely discovered these kinds of
Speaker 1: things in geology many times, so it's fun to sort
Speaker 1: of imagine even deeper time processes. So these guys look
Speaker 1: not just at evidence for asteroid collisions, but also like
Speaker 1: just large marine extinctions or changes in the sea floor
Speaker 1: or big volcanic events. And they did the same thing.
Speaker 1: They did a four the analysis to look for a
Speaker 1: repeating signal to see like is there a period to
Speaker 1: sort of large theological events on the surface of the Earth.
Speaker 1: And these guys in their paper, they actually claim to
Speaker 1: discover a signal every twenty eight million years. They said
Speaker 1: that there's strong statistical evidence for something bad happening every
Speaker 1: twenty eight million years. But I actually have to take
Speaker 1: issue with this paper. I read this paper and I
Speaker 1: think that they've done these statistical analysis wrong. Oh boy,
Speaker 1: some drama, getting ready for some some statistical analysis drama.
Speaker 1: All right, let's go. Let's let's take them down. What
Speaker 1: they did is they looked for the most common recurrence
Speaker 1: and they found something abound twenty eight million years. But
Speaker 1: you know, every time you're gonna look at your data,
Speaker 1: you're gonna find something to be the most common. The
Speaker 1: question is like, how likely is it to be that significant?
Speaker 1: Is it really a big peak or is it just
Speaker 1: sort of like the biggest peak among a bunch of
Speaker 1: random noise. And so they tried to calculate this. They
Speaker 1: try to say, like how likely is there to see
Speaker 1: this big peak at twenty million years? Is this likely
Speaker 1: to just be noise or is this something real? So
Speaker 1: they ran a bunch of statistical tests to see, like
Speaker 1: how like ease it to see something at twenty eight
Speaker 1: million years, and they found those very unlikely to see
Speaker 1: this kind of peak. And from that they conclude, oh,
Speaker 1: while this must be real because it's very unlikely to
Speaker 1: generate this from just random noise. Problem with this method
Speaker 1: of statistical analysis is that they were only calculating the
Speaker 1: probability of seeing a peak from random events at twenty
Speaker 1: eight million years, whereas these random events also could have
Speaker 1: generated peaks at thirty million years and fifteen million years,
Speaker 1: and if they'd seen that in their data, they would
Speaker 1: have happily written a Nature paper about that as well.
Speaker 1: So I think they sort of overstate the case that
Speaker 1: this thing rises above the random noise. And in my view,
Speaker 1: there's no real statistical evidence here for the geologic record
Speaker 1: having any sort of period of major events, so speaking
Speaker 1: purely for a friend who may go a little cross
Speaker 1: side when discussing statistics. So essentially they're basically kind of
Speaker 1: pruning data points that would make this finding more likely,
Speaker 1: whereas if they included in their analysis all the data points,
Speaker 1: you would get a lot more evidence of noise. Yeah,
Speaker 1: it's like saying, what's the chance of getting a random
Speaker 1: peak at this number? It's pretty small. Well, what's the
Speaker 1: chance of getting a random peak at any number? It's
Speaker 1: going to be much much bigger, And that's the number
Speaker 1: they really need to be accounting for, because they would
Speaker 1: have accepted a peak but basically any number. Right now,
Speaker 1: it is interesting that the peak they get is just
Speaker 1: about at thirty million years. That is suggestive because we
Speaker 1: know there is this process where the Sun goes in
Speaker 1: and out of the galactic plane every thirty one million years,
Speaker 1: though they measure there's to be twenty eight million years.
Speaker 1: And that might not seem like a big difference to you,
Speaker 1: but three million years is not a short amount of time. Yeah,
Speaker 1: sounds circumstantial to me. Can you imagine if literature review
Speaker 1: was like a courtroom that you actually got to kind
Speaker 1: of be a big fancy city lawyer in court arguing
Speaker 1: for against statistical analysis. I think that would make science
Speaker 1: a lot more interesting. It would probably make it for
Speaker 1: a lot more deep grudges also, and you know, for
Speaker 1: answering our question about whether there's a pattern to asteroid
Speaker 1: impacts on Earth, remember that this paper is thinking about
Speaker 1: all geological events, supervolcanoes and all sorts of other stuff.
Speaker 1: And if you look at most of these events the
Speaker 1: boundaries between geological time scales. For example, only the event
Speaker 1: it's sixty five million years ago in the geological record
Speaker 1: shows a significant impact. You know, we can see like
Speaker 1: the ash and the dust from that impact in the record.
Speaker 1: If you dig down into the earth, you can find
Speaker 1: that and see the impact the other transition periods and
Speaker 1: the die offs that don't seem to align with any
Speaker 1: asteroid impact. There's no like event. We can find no
Speaker 1: evidence of ash and dust, so it seems pretty loose.
Speaker 1: As far as we can tell right now, there is
Speaker 1: no evidence of periodic asteroid impact on Earth, which is,
Speaker 1: you know, good news because it means that another one
Speaker 1: might not be coming. But it's bad news because it
Speaker 1: means they might just be unpredictable. I mean, it's also
Speaker 1: bad news if I really want to cancel my dentist
Speaker 1: appointment and the next million years or so, you know.
Speaker 1: I think another thing is that when the big one
Speaker 1: hit Earth and you know, killed off the dinosaurs. Of
Speaker 1: course a little more complicated than that. I mean, there
Speaker 1: were also other things happening at the time, other geological
Speaker 1: activity that was contributing to the extinction. So it wasn't
Speaker 1: just the asteroid. They also think that there was volcanic
Speaker 1: activity that had nothing to do with the asteroid that
Speaker 1: was causing an impact on the environment. And so it
Speaker 1: was just this kind of like poorly timed asteroid that
Speaker 1: kind of helped put a nail in the coffin of
Speaker 1: an already sort of precarious situation for the dinosaurs, and
Speaker 1: so yeah, I think it seems like it'd be a
Speaker 1: little too tidy in terms of finding. You know that
Speaker 1: every thirty million years we get hit by an asteroid
Speaker 1: and all the animals, you know, go oh no, except
Speaker 1: for a lucky few of them that end up surviving.
Speaker 1: But it does seem like the actual picture of it
Speaker 1: would be a lot messier, have to do with a
Speaker 1: lot more kind of just a confluence of environmental factors,
Speaker 1: both on Earth and maybe you know, outside of Earth,
Speaker 1: rather than just one kind of convenient every thirty million
Speaker 1: years asteroids and backdown. You sound like the asteroids defense
Speaker 1: lawyer saying, hey, look, it wasn't my client. Even if
Speaker 1: they were there, there was other stuff going on. I
Speaker 1: may be a simple country lawyer, but the evidence that
Speaker 1: my asteroid was anywhere near those dinosaurs is purely circumstantial.
Speaker 1: I'm going to call in Daniel Whiteson to argue about
Speaker 1: the statistical analysis of this paper. Al Right, well, I
Speaker 1: think you can rest easy then, knowing that a big
Speaker 1: asteroid may not necessarily be on way to pulverize all
Speaker 1: of us. That is the most like lackluster optimistic thing
Speaker 1: I've ever heard. It's like you can rest easy knowing
Speaker 1: that you not die a random and horrible death along
Speaker 1: with everyone else on Earth. But hey, you know, glass
Speaker 1: half full. You may not die of predictable periodic death,
Speaker 1: but you may actually die a random, horrible death because
Speaker 1: comments and asteroids are unpredictable, and especially comets are really
Speaker 1: a source of danger. And we need to keep funding
Speaker 1: those telescopes to look out there. We need to keep
Speaker 1: developing these technologies to divert these objects if they do
Speaker 1: come towards our wonderful planet. Oh, I see, this is
Speaker 1: why you're blaming the asteroids. This is a shakedown for
Speaker 1: funding for science, just trying to save the planet. I mean,
Speaker 1: just a little little thing like saving the planet. How convenient?
Speaker 1: All right, Well, thank you Katy very much for joining
Speaker 1: us on this optimistic view of our situation in the
Speaker 1: Solar System and offering your full throw defense of asteroids.
Speaker 1: And thanks everybody for listening to another deep dive into
Speaker 1: the deep history of life on Earth. Thanks for joining us.
Speaker 1: Tune in next time, yea, thanks for listening, and remember
Speaker 1: that Daniel and Jorge explain the universe is a production
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