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Speaker 1: Hey, Jorge, been enjoying their recent run of rainy days.

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Speaker 2: Yeah, I like a rainy day. It's kind of cozy.

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Speaker 1: Well, I guess that's what we get for living in

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Speaker 1: ice age rainy days. Even in southern California.

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Speaker 2: Where we're in an ice age, I don't see any

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Speaker 2: wooly mammoths around.

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Speaker 1: Yeah, the wooly mammoths disappeared, and not just because the temperature.

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Speaker 2: What happened They moved to a warmer planet.

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Speaker 1: No, I think our ancestors turned them all into soup

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Speaker 1: and blankets so they could be cozy on rainy days.

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Speaker 2: Wait, that's not what I saw in the movie Ice Age.

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Speaker 1: Not a documentary.

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Speaker 2: It's also not TG I guess. I am Hore Makertoona

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Speaker 2: and the author of Oliver's Great Big Universe.

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Speaker 1: Hi, I'm Daniel. I'm a particle physicist and a professor

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Speaker 1: at UC Irvine, and I live for the sunshine.

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Speaker 2: Well, we all live because of the sunshine too.

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Speaker 1: Right, Yeah, that's right. Almost all energy used by life

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Speaker 1: on Earth comes initially from the sun.

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Speaker 2: It grows vegetables and food, and that's how we can

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Speaker 2: all stay alive and warm.

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Speaker 1: Also, that's right, when you burn a piece of wood

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Speaker 1: and you feel that glow. It's like it's released that

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Speaker 1: original solar energy trees are basically solar energy batteries.

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Speaker 2: Yeah, whenever I see a big green field that I

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Speaker 2: always thinking, well, that's an awesome natural solar panel.

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Speaker 1: I know, it is incredible that evolution has devised this

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Speaker 1: way to eat photons and turn it right into chemical energy.

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Speaker 1: Pretty amazing.

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Speaker 2: Yeah. Yeah, although in between there's you know, a nice salad,

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Speaker 2: and maybe more in between is a nice a piece

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Speaker 2: of fried chicken.

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Speaker 1: I like to think of all the photons in my.

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Speaker 2: Salad, although it is a little heavy. It's not very

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Speaker 2: light to have a fried chicken salad. But anyways, welcome

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Speaker 2: to our podcast Daniel and Jorge Explain the Universe, a

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Speaker 2: production of iHeartRadio.

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Speaker 1: In which we try to shine a light on all

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Speaker 1: the heavy questions of the universe. How does it all work?

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Speaker 1: What are the smallest little bits? How do those come

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Speaker 1: together to make grass and chicken and people and planets

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Speaker 1: and stars and black holes and everything else that we

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Speaker 1: see out there in the universe. It's an incredible, dizzying

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Speaker 1: array of complexity, but we think it's possible to simplify it,

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Speaker 1: to boil it all down into a few basic ideas

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Speaker 1: that could be understood by you.

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Speaker 2: That's right. We try to serve up a nice, tantalizing

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Speaker 2: buffet of amazing facts about the universe, amazing discoveries, and

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Speaker 2: also incredible mysteries that we are still trying to figure

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Speaker 2: out in a way that is hopefully not a word

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Speaker 2: salad in your head.

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Speaker 1: A crucial goal of doing physics is understanding the nature

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Speaker 1: of the universe so that we can get a better

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Speaker 1: sense for our context. Every time we learn something about

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Speaker 1: where we are in the cosmos and how it works,

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Speaker 1: it changes the way we relate to it, how we

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Speaker 1: live our lives, what we think about it. And of course,

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Speaker 1: at the center of our local cosmic neighborhood is the Sun,

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Speaker 1: which is a source of all energy for life on

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Speaker 1: Earth and could eventually fry everything on Earth.

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Speaker 2: Yeah, because I guess it's easy sometimes to forget that

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Speaker 2: we are just sitting atop a little tiny rock, flying

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Speaker 2: around a big burning ball of gas in the middle

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Speaker 2: of a gigantic space full of things that might at

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Speaker 2: any moment kill us.

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Speaker 1: It seems like sort of a precarious and fragile situation,

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Speaker 1: Like if we didn't live it, and you read about

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Speaker 1: it in a science fiction novel, you'd be like, hmm,

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Speaker 1: that sounds kind of implausible.

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Speaker 2: You mean, the idea that we were just like perched

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Speaker 2: in the middle of a giant void where that might

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Speaker 2: kill us at anytime.

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Speaker 1: Yeah, that we're the perfect place between a huge freezing

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Speaker 1: void and an enormous ball of fire that could kill us,

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Speaker 1: and we're in the Goldilocks zone right in between them.

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Speaker 2: Yeah, and an orbit that is sort of miraculously stable, right,

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Speaker 2: that just keeps going around the over and over again

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Speaker 2: in a very stable way.

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Speaker 1: It is sort of amazing that it's worked for this long,

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Speaker 1: and we are grateful for it.

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Speaker 2: It's amazing that the Sun arises every day because it

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Speaker 2: could not, right.

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Speaker 1: It could just stay in bed like your local cartoonists.

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Speaker 2: Yeah, yeah, that's right, thankfully.

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Speaker 1: But the Sun and other stars out there are not

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Speaker 1: eternal fixtures which will be pumping out energy to support

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Speaker 1: life on Earth and alien planets forever. Sometimes they go boom.

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Speaker 1: Sometimes they explode in enormous supernova which can fry their

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Speaker 1: local region of space.

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Speaker 2: Yeah. I think we're used to the stars being out

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Speaker 2: their way out there and not really affecting our everyday

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Speaker 2: lives other than making for nice night sky view here

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Speaker 2: on Earth. But it is possible for those stars out

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Speaker 2: there to actually affect us and maybe change the way

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Speaker 2: that we live.

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Speaker 1: That's right. It's not so crazy to imagine that our

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Speaker 1: sun's variations as it gets brighter or colder as we

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Speaker 1: move closer further away, could affect temperature on Earth and

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Speaker 1: even potentially cause ice ages or global heating. But what

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Speaker 1: about other stars out there in the universe. How susceptible

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Speaker 1: are we to their.

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Speaker 2: Quirks or their big explosive quirks for that matter. So

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Speaker 2: to the podcast, we'll be asking the question, can super

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Speaker 2: nova's cause ice ages? Well, I feel like that's two

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Speaker 2: movie names and one title here, super novas, And I.

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Speaker 1: Know, I know it means we're in danger of jumping

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Speaker 1: the Shark, because now we're doing like bizarre mashups, you know,

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Speaker 1: like Shark Tornado.

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Speaker 2: I think we jumped to Shark a few hundred episodes ago,

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Speaker 2: didn't we? And we're still here. We're still writing the Shark.

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Speaker 1: I promise I didn't come up with this episode by

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Speaker 1: randomly throwing darts at the wall with topic names.

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Speaker 2: Maybe we should do an episode on the physics of sharks.

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Speaker 1: Jumping, the physics of sharknados.

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Speaker 2: You know, there's a lot of questions there. How do

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Speaker 2: you launch the shark? What are the aerodynamics of the

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Speaker 2: shark in air?

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Speaker 1: Yeah, we have a crossover episode with Katie, she probably

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Speaker 1: knows all about it.

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Speaker 2: There you go, and then you could have maybe Henry

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Speaker 2: Winkler the Fawns as a guest star, just to wrap

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Speaker 2: it all up.

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Speaker 1: And then we'll take a field trip and literally jump

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Speaker 1: over a shark, just to hammer that point home. If

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Speaker 1: people weren't getting it already, right.

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Speaker 2: Right, I think that might be illegal, uh, and feel advised,

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Speaker 2: but hey, if you want to go for it, I'll

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Speaker 2: be unsure taking pictures.

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Speaker 1: But this is not just a rim collection words mashed

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Speaker 1: together for a new idea for an episode. This is

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Speaker 1: actually something on the cutting edge of science.

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Speaker 2: Yeah, the idea that maybe a supernova out there in

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Speaker 2: space could have, maybe or can cause an ice age

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Speaker 2: here on Earth. And so, as usual, we were wondering

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Speaker 2: how many people out there had thought about this question

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Speaker 2: or maybe even linked those two ideas together. I guess

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Speaker 2: if it was close enough, we could do a lot

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Speaker 2: of damage.

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Speaker 3: One way or the other supernova was sent out heavy

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Speaker 3: Adams and on a planet, if they pile up around

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Speaker 3: the planet, they can block the other sunlight that's closer

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Speaker 3: to the body and then calls ICAG just.

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Speaker 4: Indeed, hopefully that doesn't mean the Sun, because I'm not

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Speaker 4: sure if the Sun were to go super nova it

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Speaker 4: would be cold enough for an ice age. But if

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Speaker 4: it were like a close star, maybe some of the

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Speaker 4: matter coming off of that star would shield us from

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Speaker 4: the Sun and the temperatures were cool.

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Speaker 2: I don't know.

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Speaker 4: Seems far fetched, but I can't think of it any

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Speaker 4: other way.

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Speaker 5: This is a real if a butterfly flaps its wings

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Speaker 5: on the other side of the world kind of question. Sure,

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Speaker 5: a supernova would admit charged particles that would mess with

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Speaker 5: a magnetic field and potentially strippinozone layer, so that would

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Speaker 5: affect the climate dramatically. So yes, supernovas could cause ice ages.

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Speaker 1: Thanks very much to everybody who participates. I love hearing

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Speaker 1: your voices on the topics of the day. If you'd

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Speaker 1: like to lend your thoughts to this segment of the podcast,

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Speaker 1: please don't be shy wright to me. Two questions at

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Speaker 1: Daniel and Jorge dot com. I'm pretty sure nobody ever

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Speaker 1: regretted it.

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Speaker 2: Would they tell you though.

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Speaker 1: You know, people on the Internet are not shy to

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Speaker 1: share their opinions, so I'm pretty sure I would get

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Speaker 1: a grumpy email. If somebody's really grumpy about it.

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Speaker 2: Well, I think if they regretted it, they wouldn't reply

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Speaker 2: back again. So think about all the emails you're not getting.

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Speaker 1: If you participate in this segment of the podcast and

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Speaker 1: you deeply, deeply regret it, please write to me share

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Speaker 1: your pain.

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Speaker 2: Just havn't fill out a survey after every interaction with

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Speaker 2: ten you have you enjoyed my talking with me? Please

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Speaker 2: wanting to fill out the survey?

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Speaker 1: No, then they're going to regret it because everybody regrets

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Speaker 1: getting those surveys.

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Speaker 2: Well, maybe you haven't fill out a survey about being

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Speaker 2: asked to fill out.

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Speaker 1: A survey, and then they recursively begin to hate me.

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Speaker 2: Yeah, there you go, And as time goes to infinity,

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Speaker 2: the universe will filled with it all approach to having

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Speaker 2: gained zero.

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Speaker 1: Knowledge and the band with the Internet will be surveys.

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Speaker 2: But anyways, these are great answers from people. It seems

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Speaker 2: like people think that maybe there could be a connection

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Speaker 2: there in the same way that maybe a butterfly can

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Speaker 2: flap its wing and I could get fried chicken the

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Speaker 2: next morning because of that.

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Speaker 1: Yeah, it's sort of a cosmic butterfly effect. Imagine a

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Speaker 1: butterfly and alien planet triggering a supernova in that solar system,

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Speaker 1: which then somehow makes ice ages in hours. Amazing power

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Speaker 1: of butterflies.

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Speaker 2: Yeah, and fried chicken as well. But this is an

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Speaker 2: interesting question. Could a supernova out there in space somehow

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Speaker 2: affect the climate here on Earth to the extent that

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Speaker 2: maybe we actually get an ice age?

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Speaker 1: Hmm amazing.

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Speaker 2: So maybe let's start with the basics here that Daniel,

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Speaker 2: what is the supernova and could one happen near us?

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Speaker 1: A supernova is a really exciting and dramatic possible endpoint

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Speaker 1: to a star. Not every star ends the same way.

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Speaker 1: The fate of a star depends almost entirely on its

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Speaker 1: initial mass. These stars are formed from huge clouds of

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Speaker 1: gas and dust where something has triggered a gravitational runaway effect.

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Speaker 1: So klump of stuff pulls together, and if it's too

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Speaker 1: small it makes something like a brown dwarf. But if

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Speaker 1: you get enough stuff in there, you can think of

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Speaker 1: nice fusion and you can get a star and it

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Speaker 1: can be burning. A lot of stars are kind of small.

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Speaker 1: They're called like red dwarf stars, and those stars are

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Speaker 1: just going to burn for a long long time and

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Speaker 1: then eventually become like white dwarfs. Larger stars, though, when

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Speaker 1: they run out of fuel that fuels what's preventing them

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Speaker 1: from collapsing further gravitationally by providing pressure from the fusion

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Speaker 1: inside of them. Larger stars, when that fuel runs out,

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Speaker 1: they have so much gravity that they collapse, which then

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Speaker 1: triggers an explosion at the heart of the star, which

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Speaker 1: we call a supernova.

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Speaker 2: But I guess a couple of questions there. First of all,

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Speaker 2: do smaller stars ever run out of fuel? Don't they

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Speaker 2: run out of fuel too? And what happens to them

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Speaker 2: when they run out of fuel?

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Speaker 1: Yeah, smaller stars definitely run out of fuel because they're smaller,

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Speaker 1: their core is not as high temperature or as high pressure,

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Speaker 1: so they go through their fuel more. So they can

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Speaker 1: last for like billions and billions of years, but they

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Speaker 1: eventually will run out of fuel and they'll just form

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Speaker 1: white dwarfs. White dwarfs are just like their remnant of fusion.

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Speaker 1: But it's no longer fusing. Like if you produce a

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Speaker 1: bunch of carbon, but you're not hot enough to fuse carbon,

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Speaker 1: then you just turn into a hot lump of carbon,

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Speaker 1: and that white dwarf sits around for maybe trillions of years,

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Speaker 1: glowing in space without fusing, until cools enough to become

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Speaker 1: a black dwarf.

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Speaker 2: But somehow there's a difference between that and a larger

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Speaker 2: star because the larger stars collapse. The smaller stars don't collapse.

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Speaker 1: Yeah, the larger stars have born gravity and so they

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Speaker 1: can overcome the structural strength of the fusion remnants. Like

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Speaker 1: the reason that white dwarf doesn't collapse further is that

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Speaker 1: the structure of that big blob of carbon or nickel

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Speaker 1: or whatever it's turned out to be is stronger than

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Speaker 1: the gravitational forces. But if you have enough mass, you

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Speaker 1: can overcome that and you can trigger another collapse, and

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Speaker 1: that creates intense pressure and temperature at the core. So

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Speaker 1: now you can fuse stuff you couldn't fuse before, and

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Speaker 1: that creates very very fast, burning, very short lived reaction

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Speaker 1: which causes an explosion again, which blows out a huge

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Speaker 1: amount of material, and that's the supernova.

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Speaker 2: Well, the other question I had was does the fate

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Speaker 2: of a star also depend on what it's made out of,

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Speaker 2: not just its mass, Like does a star with its

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Speaker 2: pure hydrogen have a different fate than one that's more

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Speaker 2: mixed in with other elements?

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Speaker 1: Yeah. Absolutely, the amount of metal that a star starts

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Speaker 1: with can really change the star's behavior. The more metal

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Speaker 1: there is in a star, the more opaque it is

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Speaker 1: to its own radiation, so the more it absorbs those

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Speaker 1: photons rather than emitting it, So that can really change

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Speaker 1: the temperature in the star, which changes the rate of fusion.

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Speaker 1: And so the question of like how much metal each

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Speaker 1: star starts with is really important one and one we're

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Speaker 1: still trying to understand. We had a whole episode recently

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Speaker 1: about how metal is our sun, and we know that

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Speaker 1: it's like a couple percent metal, by which we mean

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Speaker 1: things heavier than helium and hydrogen. But it is an

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Speaker 1: important contribution, and so it's mostly determined by the mass

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Speaker 1: of the star, but also other things like the composition,

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Speaker 1: and it's not totally understood, like which star will go

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Speaker 1: supernova is not something we can actually predict.

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Speaker 2: Now, does this star having more metal make it more

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Speaker 2: explosive or less explosive? Like it's being more metal, more radical.

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Speaker 1: More metallic stars are more likely to undergo supernova and

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Speaker 1: turn into neutron stars, whereas low metallicity stars are more

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Speaker 1: likely to collapse directly into a black hole and might

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Speaker 1: not even give you a supernova.

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Speaker 2: Interesting. Yeah, I guess I would go straight into a

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Speaker 2: black hole. Then there's nothing to explode out because nothing

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Speaker 2: can get out.

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Speaker 1: Yeah, exactly, But that's from like really massive stars above

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Speaker 1: like forty times the mass of our star. In the

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Speaker 1: intermediate region, like between ten and forty times the mass

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Speaker 1: of our star. A lot of these will go supernova,

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Speaker 1: but again it's hard to predict. It's a very chaotic event.

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Speaker 1: In the moment at which a star is going to

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Speaker 1: go supernova is not easy to tell. Like people have

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Speaker 1: been watching Beetlejuice recently because it's brightness has become quite

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Speaker 1: variable and they're wondering, like, is it about to go supernova?

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Speaker 1: But nobody can tell when a star is about to

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Speaker 1: go supernova. We don't understand the process, even in simulation.

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Speaker 1: It's not something we know how to explain.

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Speaker 2: Yeah, that's something that you said that also made me curious,

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Speaker 2: was this idea we don't really understand this process very well.

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Speaker 2: And I guess it's interesting that we haven't really studied

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Speaker 2: supernova's very much, right, Like, we haven't been present when

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Speaker 2: we see one. We haven't been up close to another

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Speaker 2: star when supernova goes up, thankfully, maybe, But it's all

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Speaker 2: sort of done through simulations and models of what we

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Speaker 2: think is happening inside of a star from what we

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Speaker 2: can gather from the kind of these pinpoints in the sky. Right.

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Speaker 1: Yeah, we certainly have studied supernova, and you're right, a

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Speaker 1: lot of the work is done in models. The reason

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Speaker 1: we haven't studied more supernova is because supernova are really rare.

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Speaker 1: It's not something that has depends all the time, sort

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Speaker 1: of thankfully, otherwise we might have been fried out of existence.

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Speaker 2: You know.

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Speaker 1: In the Milky Way, for example, we expect there to

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Speaker 1: be like two supernova's out of the hundreds of billions

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Speaker 1: of stars every hundred years, and so it's not something

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Speaker 1: that happens very often. And weirdly, we haven't seen a

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Speaker 1: supernova in the Milky Way for a few hundred years.

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Speaker 1: So that's another mystery we did a whole podcast episode about.

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Speaker 1: But it's not something that happens often enough for us

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Speaker 1: to get a lot of data. It's like spontaneous human combustion.

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Speaker 1: You know, you hear about it happening occasionally. It's really

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Speaker 1: hard to predict and so you have like sort of

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Speaker 1: sparse data to work with to understand, you know, what

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Speaker 1: might cause it.

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Speaker 2: M I guess what makes it hard to predict, Like,

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Speaker 2: isn't under signs that the sun goes through or the

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Speaker 2: star goes through right before it blows up, Like doesn't

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Speaker 2: it maybe ramp up in brightness or something.

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Speaker 1: We'd love to know that. And it's really tricky because

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Speaker 1: we can't monitor every single star until one of them

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Speaker 1: goes supernova. They're just so many stars. So typically what

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Speaker 1: happens is we see a star go supernova, then we

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Speaker 1: start taking a lot of detailed data on it, but

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Speaker 1: that's all post supernova. It we'd be very lucky to

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Speaker 1: have been watching in great detail star just before it

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Speaker 1: goes supernova, and that's one reason why we can't tell

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Speaker 1: it stars go supernova. And from the theoretical side, it's

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Speaker 1: very tricky because it's very intense physics. The stuff is

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Speaker 1: moving close to the speed of light. It's very high density,

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Speaker 1: it's very high intensity. There's a huge number of particles.

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Speaker 1: The kind of calculations are very difficult to do correctly

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Speaker 1: because not only are all the particles important, but it's

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Speaker 1: very chaotic, like a small change in the structure of

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Speaker 1: the star can lead to a large change in how

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Speaker 1: that collapse happens and the shock waves. It's very complicated.

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Speaker 1: I'm actually working with some folks at Berkeley who are

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Speaker 1: doing supernova simulations, and each one of them requires running

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Speaker 1: the supercomputer for millions and millions of hours, so we

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Speaker 1: don't even have a lot of examples of supernova in simulation.

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Speaker 2: Well, yeah, and I guess if you, you know, try

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Speaker 2: to look for supernova and by looking at this guy

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Speaker 2: all the time, you'd still be waiting, right, he said,

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Speaker 2: we haven't had one in a long time. When was

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Speaker 2: the last supernova that we've seen.

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Speaker 1: In our galaxy? The last supernova was seen I think

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Speaker 1: by Kepler, so four hundred years ago.

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Speaker 2: Four hundred years ago, is it possible that one happened?

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Speaker 2: What we didn't see it?

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Speaker 1: Those are just supernova's in the Milky Way, And it's

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Speaker 1: possible there have been supernova's in the Milky Way we

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Speaker 1: haven't seen because we can't see through all the cosmic

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Speaker 1: dust at the center of the galaxy. And weirdly, a

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Speaker 1: lot of the supernovas we have seen in the Milky

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Speaker 1: Way are far away from where most of the stars are.

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Speaker 1: That's a whole funny, amazing mystery. But because supernova are

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Speaker 1: so bright, we can also see them from other galaxies.

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Speaker 1: In fact, when a supernova goes sometimes they're like a

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Speaker 1: million or billion, or even a trillion times brighter than

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Speaker 1: the Sun. They can outshine the rest of the galaxy.

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Speaker 2: Yeah, they're super bright. But I guess any given time,

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Speaker 2: isn't it true that we can only look at half

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Speaker 2: of the sky, like the daylight side. We can't really

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Speaker 2: see any stars, right can we?

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Speaker 1: Yeah, that's right, we can only see half of the sky.

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Speaker 1: And if you see a star in another galaxy go supernova,

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Speaker 1: you can tell something has gone supernova. But we can't

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Speaker 1: often pinpoint individual stars in other galaxies, so you can't

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Speaker 1: be like, oh, it was that one over there and

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Speaker 1: then go check your archival data to see what you

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Speaker 1: know about it. So if we had more telescopes constantly

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Speaker 1: studying the sky, then we could learn a lot more

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Speaker 1: about supernova because we could see them before they go,

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Speaker 1: which be really valuable.

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Speaker 2: But as we just said, basically, you'd be waiting for

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Speaker 2: four hundred years at this point, in which nobody wanted

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Speaker 2: to wait that long to get a PhD.

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Speaker 1: Yeah, exactly. And we have seen again in supernova more recently,

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Speaker 1: like there's a famous one in nineteen eighty seven, very bright.

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Speaker 1: You could almost even see it in the daytime from

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Speaker 1: another galaxy, of course, not in the Milky Way.

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Speaker 2: So they're sort of rare, but they do happen. And

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Speaker 2: of course the universe in our galaxies are billions of

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Speaker 2: years old, so many of them, probably a lot of

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Speaker 2: them have happened since. And so the idea is that

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Speaker 2: maybe the supernovas could somehow affect what life is like

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Speaker 2: here on Earth.

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Speaker 1: That's the question, yes, exactly, And so.

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Speaker 2: Let's get into that question of whether a super and

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Speaker 2: I can actually trigger an ice age here on this planet.

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Speaker 2: So let's dig into that, but first let's take a

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Speaker 2: quick break. All right, we're talking about supernovas and ice ages,

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Speaker 2: both great movies, different audience.

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Speaker 1: Though, what is the movie supernova? I haven't seen that one.

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Speaker 1: I think there must be a movie called Supernova. Yeah,

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Speaker 1: of course, you're right, there's a movie Supernova. Twenty twenty,

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Speaker 1: Sam and Tusker are traveling across England in their old

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Speaker 1: RV to visit friends. I'm not sure it's really about

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Speaker 1: the supernova, but yeah.

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Speaker 2: That doesn't sound like it's about astrophysics or space for

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Speaker 2: that matter. Isn't there an older movie called Supernova?

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Speaker 5: Oh?

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Speaker 1: Okay, here's one from two thousand. This is a science

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Speaker 1: fiction action film. Is it the one starting Killian Murphy?

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Speaker 1: It chronicles the search and rescue patrol of a medical

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Speaker 1: ship in deep space.

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Speaker 2: All right, well, obviously it was not very popular.

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Speaker 1: But everybody should go check it out. I mean, this

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Speaker 1: one from twenty has an eleven percent rating on Rotten Tomatoes.

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Speaker 2: So yeah, ja, I guess the movie didn't blow up.

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Speaker 1: Yeah, I don't think it an ignited passion in the audience.

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Speaker 2: Yeah, it just kind of collapsed under its own weight perhaps.

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Speaker 2: But anyways, we're talking about whether a supernova that happens

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Speaker 2: out there in space could somehow trigger an ice age

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Speaker 2: here on Earth, which is because sort of mind blowing

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Speaker 2: to think about that's something so far away that is

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Speaker 2: explosive and hot can somehow make us cooler. Yeah.

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Speaker 1: Yeah, it is amazing how interconnected everything is and how

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Speaker 1: delicate everything is.

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Speaker 2: Now we've talked about supernova's. Now let's talk about ice ages,

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Speaker 2: and so what do we know about ice ages here

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Speaker 2: on Earth?

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Speaker 1: So ice age is a generic term for basically a

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Speaker 1: period when Earth is cold, there's more glaciers, there's more

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Speaker 1: polar ice, and if you look back at the history

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Speaker 1: of life on Earth, you see these big variations in

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Speaker 1: the climate. So there are times when like all of

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Speaker 1: North America was under ice sheets, and then times when

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Speaker 1: there's almost no ice on Earth. So it oscillates between

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Speaker 1: like a greenhouse Earth and a snowball Earth.

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Speaker 2: So they're just periods in time where things were cold.

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Speaker 1: Yeah, exactly, And this is just what geologists have called

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Speaker 1: these historic periods when the average temperature was much lower.

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Speaker 1: But it's really fascinating because it tells us a lot

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Speaker 1: about how climate on Earth. Works. And there's not just

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Speaker 1: these big ice ages which lasts like millions of years,

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Speaker 1: but there's also cycles within those ice ages. So within

440
00:21:42,760 --> 00:21:45,800
Speaker 1: an ice age, there are glacial periods, which is when

441
00:21:45,840 --> 00:21:49,600
Speaker 1: it's colder, and interglacial periods when it's hotter. So like

442
00:21:49,720 --> 00:21:52,800
Speaker 1: currently we are in an ice age, but we're in

443
00:21:52,840 --> 00:21:56,199
Speaker 1: an interglacial period. Of that ice age, so like on

444
00:21:56,320 --> 00:21:58,879
Speaker 1: average it's colder than Earth has been in the past,

445
00:21:59,040 --> 00:22:01,919
Speaker 1: but we're in a warmer period of that ice age.

446
00:22:02,119 --> 00:22:04,800
Speaker 2: Well, yeah, I guess, first of all, it's kind of

447
00:22:04,880 --> 00:22:07,040
Speaker 2: a mind blown to think that, you know, the Earth

448
00:22:07,160 --> 00:22:10,480
Speaker 2: goes through these changes in these periods, like the Earth

449
00:22:10,480 --> 00:22:11,840
Speaker 2: hasn't always been the same.

450
00:22:12,680 --> 00:22:15,119
Speaker 1: It's sort of like a dynamic system. Yeah, it's definitely

451
00:22:15,119 --> 00:22:17,760
Speaker 1: a dynamic system. And these ice ages date back like

452
00:22:17,880 --> 00:22:20,879
Speaker 1: billions of years. One of the earliest ice ages we

453
00:22:20,920 --> 00:22:24,080
Speaker 1: know about started like almost two and a half billion

454
00:22:24,200 --> 00:22:27,159
Speaker 1: years ago, and then the more recent ones are all

455
00:22:27,200 --> 00:22:30,159
Speaker 1: in the last like five hundred million years. But the

456
00:22:30,200 --> 00:22:32,080
Speaker 1: Earth is definitely a dynamic and you know life on

457
00:22:32,119 --> 00:22:35,040
Speaker 1: Earth has responded to it and influenced it. You know,

458
00:22:35,160 --> 00:22:38,399
Speaker 1: early life, for example, couldn't tolerate the presence of oxygen,

459
00:22:38,840 --> 00:22:41,600
Speaker 1: and then when oxygen started to be produced by photosynthesis,

460
00:22:41,920 --> 00:22:44,800
Speaker 1: life then evolved to take advantage of that. And so

461
00:22:44,920 --> 00:22:46,880
Speaker 1: it's fascinating how it's all interconnected.

462
00:22:48,040 --> 00:22:49,760
Speaker 2: I guess the question is how do we know about

463
00:22:49,800 --> 00:22:53,040
Speaker 2: ice ages from billions of years ago? Like, wasn't the

464
00:22:53,080 --> 00:22:55,800
Speaker 2: Earth totally different? Do we still have evidence of those things?

465
00:22:55,920 --> 00:22:57,960
Speaker 1: We know a lot about the history of the Earth

466
00:22:58,040 --> 00:23:01,760
Speaker 1: from sort of three different categories of evidence. There's like

467
00:23:01,880 --> 00:23:06,560
Speaker 1: geological evidence, there's chemical evidence, and then there's evidence from life,

468
00:23:06,600 --> 00:23:11,120
Speaker 1: like paleontology. And so the geological evidence is like, let's

469
00:23:11,200 --> 00:23:13,600
Speaker 1: look at the shape of the surface of the Earth.

470
00:23:14,200 --> 00:23:16,040
Speaker 1: You know, about one hundred and fifty years ago or

471
00:23:16,040 --> 00:23:18,880
Speaker 1: in the mid eighteen hundreds, people were noticing weird things

472
00:23:18,920 --> 00:23:22,720
Speaker 1: they couldn't explain, like weirdly shaped valleys and like boulders

473
00:23:22,720 --> 00:23:24,800
Speaker 1: and the alps that looked like they came from much

474
00:23:24,800 --> 00:23:27,000
Speaker 1: further north in Europe, and like how did they get there.

475
00:23:27,560 --> 00:23:30,440
Speaker 1: There's then that people postulated this idea that like glaciers

476
00:23:30,720 --> 00:23:34,679
Speaker 1: move across the Earth and like create valleys and scrape

477
00:23:34,760 --> 00:23:38,280
Speaker 1: out regions of the earth and can carry boulders with

478
00:23:38,400 --> 00:23:41,440
Speaker 1: them for thousands of miles. So the geology of the

479
00:23:41,480 --> 00:23:44,080
Speaker 1: Earth tells us a lot about the sort of history of.

480
00:23:44,119 --> 00:23:49,199
Speaker 2: Glaciation, even though I guess rocks are constantly changing and

481
00:23:49,320 --> 00:23:51,879
Speaker 2: moving and churning with the core of the Earth.

482
00:23:52,000 --> 00:23:54,240
Speaker 1: Yeah, absolutely, there's a lot of things going on, but

483
00:23:54,280 --> 00:23:56,440
Speaker 1: this is one of the processes and an important one

484
00:23:56,440 --> 00:23:59,520
Speaker 1: for understanding sort of the shape of the surface of

485
00:23:59,600 --> 00:24:00,000
Speaker 1: the Earth.

486
00:24:00,359 --> 00:24:03,199
Speaker 2: Mm, so that's looking at rocks. How else can we know?

487
00:24:03,520 --> 00:24:05,720
Speaker 1: So we can also take samples of the Earth because

488
00:24:05,720 --> 00:24:08,320
Speaker 1: the different conditions on the surface are stored in the

489
00:24:08,480 --> 00:24:11,080
Speaker 1: history on Earth. So, for example, if you go to

490
00:24:11,160 --> 00:24:14,080
Speaker 1: the poles and you take ice cores, they do these

491
00:24:14,119 --> 00:24:16,920
Speaker 1: amazing drills where they're like drilled into the ice one

492
00:24:17,040 --> 00:24:19,560
Speaker 1: or two miles deep and then they pull it out.

493
00:24:19,560 --> 00:24:22,359
Speaker 1: You can see layers from all the different winters on Earth.

494
00:24:22,840 --> 00:24:25,080
Speaker 1: And in those layers you can measure like, first of all,

495
00:24:25,080 --> 00:24:27,560
Speaker 1: the thickness of the layer, like what was the average snowfall?

496
00:24:28,080 --> 00:24:31,240
Speaker 1: And there are trapped air bubbles in there which give

497
00:24:31,280 --> 00:24:34,800
Speaker 1: you samples of the atmosphere from hundreds of thousands of

498
00:24:34,920 --> 00:24:38,000
Speaker 1: years ago. And if you look at those samples of atmosphere,

499
00:24:38,040 --> 00:24:40,240
Speaker 1: you can do clever tricks to figure out like how

500
00:24:40,280 --> 00:24:40,880
Speaker 1: cold it.

501
00:24:40,960 --> 00:24:43,920
Speaker 2: Was back then, yeah, and what it smelled like. Right,

502
00:24:43,960 --> 00:24:47,200
Speaker 2: Basically you can smell the air from millions of years ago.

503
00:24:47,560 --> 00:24:50,400
Speaker 1: Yeah, that's right. We might have some mammoth farts saved

504
00:24:50,480 --> 00:24:51,280
Speaker 1: in the North Pole.

505
00:24:53,080 --> 00:24:56,680
Speaker 2: Well, Takende, we we're all smelling mammoths farts right now

506
00:24:57,160 --> 00:25:00,359
Speaker 2: because the same air molecules where around back then.

507
00:25:01,280 --> 00:25:04,280
Speaker 1: Yeah, I guess that's true. And so the ice cores

508
00:25:04,280 --> 00:25:06,800
Speaker 1: give us samples of the atmosphere up to like hundreds

509
00:25:06,840 --> 00:25:09,440
Speaker 1: of thousands of years ago. And we can go even

510
00:25:09,480 --> 00:25:12,520
Speaker 1: deeper into the path by looking at ocean sediment, like

511
00:25:12,600 --> 00:25:15,040
Speaker 1: stuff that falls into the ocean and then settles to

512
00:25:15,080 --> 00:25:17,720
Speaker 1: the bottom of the ocean. If you take cores of

513
00:25:17,760 --> 00:25:20,920
Speaker 1: the ocean floor, you can again drill down really really

514
00:25:20,960 --> 00:25:24,240
Speaker 1: far you find this sedimentation, and there's a lot of

515
00:25:24,280 --> 00:25:27,280
Speaker 1: details about the chemistry of that sedimentation and what's deposited

516
00:25:27,280 --> 00:25:29,879
Speaker 1: in the thickness of those layers that give you important

517
00:25:29,920 --> 00:25:32,920
Speaker 1: clues about what was going on in the Earth's atmosphere,

518
00:25:33,000 --> 00:25:35,840
Speaker 1: and that can take you back millions and millions of years.

519
00:25:36,240 --> 00:25:38,439
Speaker 2: Well, you can tell how cold and hot it was.

520
00:25:38,600 --> 00:25:38,800
Speaker 4: Yeah.

521
00:25:38,840 --> 00:25:41,760
Speaker 1: Most of these clues about the temperature from the ice

522
00:25:41,800 --> 00:25:46,160
Speaker 1: cores and the ocean sediment come from isotope ratios, because

523
00:25:46,240 --> 00:25:50,000
Speaker 1: different isotopes of water, for example, have different chemistry and

524
00:25:50,040 --> 00:25:52,840
Speaker 1: so like more of it will evaporate, for example, when

525
00:25:52,880 --> 00:25:55,399
Speaker 1: it's hotter, and so the ratio of these isotopes you

526
00:25:55,440 --> 00:25:57,960
Speaker 1: can back that out and figure out something about the

527
00:25:58,000 --> 00:26:01,040
Speaker 1: temperature of the air, which is pretty yeah.

528
00:26:01,040 --> 00:26:04,159
Speaker 2: Wow, it's sort of like carbon dating but water dating

529
00:26:04,320 --> 00:26:04,639
Speaker 2: kind of.

530
00:26:04,920 --> 00:26:07,399
Speaker 1: Yeah, exactly, and it's not trivial, right, there's lots of

531
00:26:07,440 --> 00:26:09,560
Speaker 1: reasons why stuff on the ocean floor or in the

532
00:26:09,560 --> 00:26:12,440
Speaker 1: ice cores can get confused, but it's an important part

533
00:26:12,440 --> 00:26:15,560
Speaker 1: of this evidence. There's a really impressive scientific body of

534
00:26:15,560 --> 00:26:18,520
Speaker 1: work here figuring out how to deduce this from these

535
00:26:18,560 --> 00:26:19,400
Speaker 1: weird clues.

536
00:26:19,760 --> 00:26:22,280
Speaker 2: Yeah, it's pretty amazing. And so we can also look

537
00:26:22,280 --> 00:26:23,560
Speaker 2: at fossils.

538
00:26:23,119 --> 00:26:25,640
Speaker 1: Right, Yeah, we can look to see where animals were,

539
00:26:25,680 --> 00:26:27,960
Speaker 1: and we can look to see, like from fossils, where

540
00:26:27,960 --> 00:26:30,240
Speaker 1: they lived and what the pattern and the climate might

541
00:26:30,280 --> 00:26:33,000
Speaker 1: have been. You know, if you know that one kind

542
00:26:33,000 --> 00:26:35,760
Speaker 1: of creature needs warmth and you see it in warm areas,

543
00:26:35,920 --> 00:26:38,399
Speaker 1: you can also see where else you find fossils and

544
00:26:38,400 --> 00:26:40,280
Speaker 1: that can give you a clue as to what the temperature.

545
00:26:40,280 --> 00:26:42,880
Speaker 1: But the climate might have been like when they were around.

546
00:26:43,240 --> 00:26:44,879
Speaker 2: So can you tell if there were sweating or if

547
00:26:44,880 --> 00:26:46,280
Speaker 2: they were shivering.

548
00:26:47,800 --> 00:26:49,760
Speaker 1: You can tell if their kids liked their dinners or

549
00:26:49,800 --> 00:26:52,400
Speaker 1: didn't like their dinners by the amount of complaining and whining.

550
00:26:52,480 --> 00:26:57,200
Speaker 1: That also changes the isotopes in the atmosphere. No, I'm

551
00:26:57,240 --> 00:26:59,760
Speaker 1: totally making that up, but you know, you can tell

552
00:26:59,840 --> 00:27:03,840
Speaker 1: what other organisms survive unchanged for millions of years, would

553
00:27:03,920 --> 00:27:06,359
Speaker 1: tell you that the climate was likely stable for millions

554
00:27:06,400 --> 00:27:08,600
Speaker 1: of years. So you can back out a lot of

555
00:27:08,600 --> 00:27:11,320
Speaker 1: interesting information from these fossils. And for me, this is

556
00:27:11,320 --> 00:27:14,320
Speaker 1: an example of the most impressive thing that science can do,

557
00:27:14,359 --> 00:27:18,320
Speaker 1: which is like reconstruct a detailed story from all these

558
00:27:18,400 --> 00:27:22,000
Speaker 1: incomplete threads, from little clues left here and there. We

559
00:27:22,040 --> 00:27:24,520
Speaker 1: can really figure out what life was like on Earth,

560
00:27:24,640 --> 00:27:27,800
Speaker 1: or understand what's inside the Earth or inside the Sun.

561
00:27:28,160 --> 00:27:30,840
Speaker 1: From all this incomplete knowledge. It's like the whole universe

562
00:27:30,880 --> 00:27:33,080
Speaker 1: is a huge mystery novel and we have just a

563
00:27:33,080 --> 00:27:36,480
Speaker 1: few traces of clues. But sometimes those clues come together

564
00:27:36,520 --> 00:27:39,040
Speaker 1: and tell you a coherent story, so you can become

565
00:27:39,080 --> 00:27:41,560
Speaker 1: convinced that you actually know something which you might have

566
00:27:41,600 --> 00:27:43,240
Speaker 1: thought would be impossible to figure out.

567
00:27:43,560 --> 00:27:45,800
Speaker 2: Yeah, it's amazing. We can look back in time. Basically,

568
00:27:45,800 --> 00:27:46,920
Speaker 2: it's like having a time machine.

569
00:27:47,200 --> 00:27:48,560
Speaker 1: Yeah, exactly.

570
00:27:49,000 --> 00:27:51,600
Speaker 2: And so what we've seen is that the temperature, the

571
00:27:51,680 --> 00:27:55,199
Speaker 2: climate on Earth has been changing a lot, and it

572
00:27:55,200 --> 00:27:57,840
Speaker 2: goes through ways and within those waves there are many waves.

573
00:27:58,240 --> 00:28:00,800
Speaker 2: I guess a big question now is what causes all

574
00:28:00,840 --> 00:28:04,359
Speaker 2: of these changes? Right? Like mm because the orbit around

575
00:28:04,359 --> 00:28:08,000
Speaker 2: the Sun hasn't changed that much for billions of years,

576
00:28:08,000 --> 00:28:08,280
Speaker 2: has it.

577
00:28:08,720 --> 00:28:10,600
Speaker 1: Yeah, Well, there's a lot of factors of play, but

578
00:28:10,720 --> 00:28:13,480
Speaker 1: one of them is the Earth's orbit. And this is

579
00:28:13,480 --> 00:28:15,920
Speaker 1: a very complex system and very chaotic because there's a

580
00:28:15,920 --> 00:28:18,480
Speaker 1: lot of feedback loops and we're gonna do some simplifications

581
00:28:18,480 --> 00:28:20,359
Speaker 1: here and we're not gonna be able to really treat

582
00:28:20,400 --> 00:28:23,119
Speaker 1: it with its full justice. But we do know some

583
00:28:23,200 --> 00:28:25,679
Speaker 1: things about what can cause an ice age. You know.

584
00:28:25,760 --> 00:28:29,200
Speaker 1: Number one is the atmosphere. If life on Earth produces

585
00:28:29,200 --> 00:28:31,320
Speaker 1: a lot of CO two or a lot of methane,

586
00:28:31,440 --> 00:28:34,720
Speaker 1: that can change the temperature on Earth for sure, right,

587
00:28:34,760 --> 00:28:37,320
Speaker 1: And there's been times in Earth's history when life is

588
00:28:37,359 --> 00:28:40,200
Speaker 1: producing more or less methane or more or less CO two,

589
00:28:40,840 --> 00:28:43,360
Speaker 1: And so what's in the atmosphere can change, like how

590
00:28:43,440 --> 00:28:45,600
Speaker 1: much light is absorbed by the Earth, how much is

591
00:28:45,640 --> 00:28:49,000
Speaker 1: reflected back out into space, and because it's a sensitive system,

592
00:28:49,320 --> 00:28:51,640
Speaker 1: that kind of an impact and even cause or end

593
00:28:51,840 --> 00:28:54,840
Speaker 1: ice ages. But another big factor is the orbit of

594
00:28:54,880 --> 00:28:58,320
Speaker 1: the Earth. There are these Melankovitch cycles, so the Earth

595
00:28:58,440 --> 00:29:00,880
Speaker 1: orbits the Sun and it's you know, mostly stable, but

596
00:29:00,920 --> 00:29:03,560
Speaker 1: there are wobbles here. Things process, and so there are

597
00:29:03,600 --> 00:29:06,680
Speaker 1: periods when we work closer and further on average, and so

598
00:29:06,720 --> 00:29:09,320
Speaker 1: these things really do change a little bit, and people

599
00:29:09,360 --> 00:29:11,680
Speaker 1: think that this is a big effect of these glacial

600
00:29:11,760 --> 00:29:14,360
Speaker 1: versus interglacial periods within an ice age.

601
00:29:14,600 --> 00:29:17,640
Speaker 2: WHOA, what causes these wobbles in our orbit? Is it

602
00:29:17,840 --> 00:29:20,920
Speaker 2: other planets or something else?

603
00:29:21,240 --> 00:29:24,040
Speaker 1: Yeah, essentially, it's because it's not such a simple system.

604
00:29:24,040 --> 00:29:27,400
Speaker 1: It's not a single mass orbiting another single mass. There's

605
00:29:27,400 --> 00:29:30,760
Speaker 1: an excentricity, we have an axial tilt, we have a procession,

606
00:29:31,120 --> 00:29:33,200
Speaker 1: and all of these things are interacting with the other

607
00:29:33,240 --> 00:29:36,440
Speaker 1: gravitational objects in the Solar System, and so we get

608
00:29:36,440 --> 00:29:39,000
Speaker 1: like little tugs from Jupiter and little tugs from other

609
00:29:39,000 --> 00:29:41,360
Speaker 1: stuff in the Solar system, and these things change. So

610
00:29:41,400 --> 00:29:43,959
Speaker 1: it changes like how much axial tilt we have and

611
00:29:44,200 --> 00:29:47,880
Speaker 1: exactly the procession of our ellipse around the Sun. And

612
00:29:47,960 --> 00:29:50,800
Speaker 1: as a result, we get slightly further or slightly closer

613
00:29:50,800 --> 00:29:53,560
Speaker 1: to the Sun, and that changes how much energy we get.

614
00:29:53,720 --> 00:29:56,600
Speaker 1: And these little effects can really cause a change in

615
00:29:56,640 --> 00:29:57,480
Speaker 1: the climate.

616
00:29:57,160 --> 00:30:01,280
Speaker 2: On Earth cool well or hot. I guess what else

617
00:30:01,280 --> 00:30:02,760
Speaker 2: it can cause an ice age.

618
00:30:02,920 --> 00:30:05,320
Speaker 1: Well, the Sun itself is variable, right, The Sun has

619
00:30:05,360 --> 00:30:08,440
Speaker 1: an eleven year cycle when it gets brighter and looser,

620
00:30:08,680 --> 00:30:10,840
Speaker 1: and then the north and south magnetic poles of the

621
00:30:10,840 --> 00:30:13,720
Speaker 1: Sun flips. This is not something we understand very well.

622
00:30:13,720 --> 00:30:16,200
Speaker 1: We don't really have a great model for the inner

623
00:30:16,240 --> 00:30:18,400
Speaker 1: workings of the Sun. We know there are these weird

624
00:30:18,480 --> 00:30:21,560
Speaker 1: plasma tubes, but it's again very chaotic, and we can't

625
00:30:21,560 --> 00:30:24,720
Speaker 1: see inside the Sun. But the Sun itself grows in

626
00:30:24,800 --> 00:30:27,840
Speaker 1: brightness and then fades, so that is part of the calculation.

627
00:30:28,080 --> 00:30:29,880
Speaker 2: Like the Sun is pulsating.

628
00:30:30,520 --> 00:30:35,240
Speaker 1: Years, yeah, exactly, and the Sun is gradually getting brighter overall, right,

629
00:30:35,360 --> 00:30:38,840
Speaker 1: the Sun's brightness is increasing very gradually as it gets older.

630
00:30:39,080 --> 00:30:41,480
Speaker 1: That doesn't change a lot over the last few centuries,

631
00:30:41,720 --> 00:30:44,480
Speaker 1: but over the long term, you know, all these things

632
00:30:44,520 --> 00:30:48,080
Speaker 1: do contribute to changes in the Earth's situation and therefore

633
00:30:48,160 --> 00:30:52,520
Speaker 1: it's climate. And then you have things like volcanoes on Earth.

634
00:30:52,680 --> 00:30:55,960
Speaker 1: If a volcano spews an enormous amount of stuff, it

635
00:30:55,960 --> 00:30:59,320
Speaker 1: could create a cloud which shrouds the earth and cools

636
00:30:59,320 --> 00:31:01,920
Speaker 1: it significantly. Or if you have like a meteor that

637
00:31:02,000 --> 00:31:05,920
Speaker 1: comes and impacts and throws up ejecta into the atmosphere,

638
00:31:06,000 --> 00:31:08,480
Speaker 1: or huge amounts of water vapor can also cause a

639
00:31:08,520 --> 00:31:09,560
Speaker 1: lot of reflectivity.

640
00:31:09,960 --> 00:31:13,520
Speaker 2: I feel really exposed right now, Like any of these

641
00:31:13,560 --> 00:31:17,240
Speaker 2: things at any moment could throw us into deathly freezing

642
00:31:17,240 --> 00:31:20,560
Speaker 2: temperatures or super duper unbearably hot temperatures.

643
00:31:20,800 --> 00:31:25,160
Speaker 1: Yeah. And it's this incredible combination of slow changing effects

644
00:31:25,480 --> 00:31:30,240
Speaker 1: and fast sudden effects like volcanoes and meteors. The last

645
00:31:30,280 --> 00:31:34,640
Speaker 1: major component is tectonic motion, like as the plates move

646
00:31:34,840 --> 00:31:37,520
Speaker 1: and as the continents themselves get dragged around the Earth,

647
00:31:37,840 --> 00:31:40,560
Speaker 1: it changes how like water flows around the Earth and

648
00:31:40,600 --> 00:31:43,760
Speaker 1: how wind currents move, and that can change the temperature

649
00:31:43,800 --> 00:31:46,120
Speaker 1: all over the Earth, like are you getting more air

650
00:31:46,160 --> 00:31:49,200
Speaker 1: from the Arctic? Is it getting fully distributed or is

651
00:31:49,200 --> 00:31:51,720
Speaker 1: it more segmented. Can really change what it's like to

652
00:31:51,760 --> 00:31:52,840
Speaker 1: be at lower latitudes.

653
00:31:53,440 --> 00:31:56,800
Speaker 2: M Well. Also, something interesting you said was that we're

654
00:31:56,840 --> 00:32:01,080
Speaker 2: currently in an ice age, meaning that over the long

655
00:32:01,200 --> 00:32:04,480
Speaker 2: history of the Earth, the average Earth temperature is actually

656
00:32:04,560 --> 00:32:06,160
Speaker 2: hotter than it is right now.

657
00:32:06,200 --> 00:32:08,720
Speaker 1: I don't know the exact number about the average, but

658
00:32:08,760 --> 00:32:11,600
Speaker 1: there definitely have been hotter periods on Earth than we

659
00:32:11,680 --> 00:32:12,400
Speaker 1: have right now.

660
00:32:12,600 --> 00:32:16,560
Speaker 2: Mm. So when you say it's colder, you mean it's

661
00:32:16,600 --> 00:32:19,440
Speaker 2: just like colder than the hottest it can get.

662
00:32:19,720 --> 00:32:22,240
Speaker 1: Yeah, the Earth is now colder than the hottest it's

663
00:32:22,240 --> 00:32:24,560
Speaker 1: ever been. For sure, there are some very very hot

664
00:32:24,560 --> 00:32:26,720
Speaker 1: periods in the history of the Earth. Of course, we

665
00:32:26,840 --> 00:32:29,080
Speaker 1: know that the Earth's climate has changed a lot in

666
00:32:29,080 --> 00:32:30,760
Speaker 1: the last one hundred ish years or so because of

667
00:32:30,760 --> 00:32:34,720
Speaker 1: the Industrial revolution and human contribution to the atmosphere, and

668
00:32:34,760 --> 00:32:38,160
Speaker 1: so things are changing pretty rapidly. But in the bigger strokes,

669
00:32:38,160 --> 00:32:40,360
Speaker 1: we are still in an ice age, though in an

670
00:32:40,400 --> 00:32:42,320
Speaker 1: interglacial period, right right.

671
00:32:42,360 --> 00:32:45,840
Speaker 2: Well, I think, and maybe an important dimension of this

672
00:32:46,040 --> 00:32:48,840
Speaker 2: idea is the rate at which things are changing, right

673
00:32:49,040 --> 00:32:51,719
Speaker 2: mm hmm. Like maybe in the past things have changed,

674
00:32:51,840 --> 00:32:55,280
Speaker 2: but maybe gradually, with enough time for life to evolve

675
00:32:55,320 --> 00:32:58,360
Speaker 2: and to adapt to it. But it can also change rapidly,

676
00:32:58,480 --> 00:33:00,560
Speaker 2: like for example, if it will case it blows up,

677
00:33:00,640 --> 00:33:02,760
Speaker 2: or if a meteor hits the Earth, that can change

678
00:33:02,760 --> 00:33:05,440
Speaker 2: things very rapidly to the point where we can that

679
00:33:05,560 --> 00:33:08,520
Speaker 2: or if we keep you know, pumping greenhouse gases into

680
00:33:08,560 --> 00:33:12,080
Speaker 2: the atmosphere, that can also make things change too rapidly

681
00:33:12,120 --> 00:33:13,400
Speaker 2: for anyone to adjust.

682
00:33:14,200 --> 00:33:16,400
Speaker 1: Yeah, it's a sensitive system and there are a lot

683
00:33:16,440 --> 00:33:18,920
Speaker 1: of things that affected and those things all have different

684
00:33:18,960 --> 00:33:22,760
Speaker 1: time scales, and they combine to make a very chaotic

685
00:33:22,880 --> 00:33:25,840
Speaker 1: sort of structure of the Earth's climate, and you have

686
00:33:25,880 --> 00:33:28,280
Speaker 1: these things that are very slowly but inevitably, like the

687
00:33:28,280 --> 00:33:31,400
Speaker 1: sun increasing in its temperature or regularly, and then the

688
00:33:31,400 --> 00:33:34,560
Speaker 1: Melankovitch cycles, which are actually like several different cycles layered

689
00:33:34,640 --> 00:33:36,840
Speaker 1: on top of each other. So as a result, you

690
00:33:36,840 --> 00:33:40,840
Speaker 1: gets very complex behavior of the Earth's climate, and it

691
00:33:40,880 --> 00:33:43,640
Speaker 1: has affected life on Ear even very recently, like this

692
00:33:43,720 --> 00:33:46,640
Speaker 1: interglacial period that we're in only started like ten to

693
00:33:46,680 --> 00:33:49,360
Speaker 1: fifteen thousand years ago, and obviously there were lots of

694
00:33:49,440 --> 00:33:52,040
Speaker 1: humans on Earth back then, and that's back when there

695
00:33:52,040 --> 00:33:55,000
Speaker 1: were more wooly mammos and there were glaciers much further

696
00:33:55,160 --> 00:33:58,640
Speaker 1: down across North America, for example. And so this is

697
00:33:58,640 --> 00:34:00,960
Speaker 1: sort of like in the deep history, maybe even the

698
00:34:00,960 --> 00:34:03,560
Speaker 1: deep memory of our own civilization.

699
00:34:04,840 --> 00:34:07,320
Speaker 2: The humans have written out some of these waves, is

700
00:34:07,320 --> 00:34:07,920
Speaker 2: what you're saying.

701
00:34:08,080 --> 00:34:11,000
Speaker 1: And these waves have affected human migration, right, there's all

702
00:34:11,040 --> 00:34:14,279
Speaker 1: these theories about humans leaving Africa and populating Europe and

703
00:34:14,320 --> 00:34:18,239
Speaker 1: doing so in several waves between ice ages perhaps, so

704
00:34:18,280 --> 00:34:20,919
Speaker 1: it's really set the whole context for life on Earth

705
00:34:20,960 --> 00:34:24,160
Speaker 1: and the evolution of humanity and its migration. It's basically

706
00:34:24,239 --> 00:34:26,719
Speaker 1: the frame in which we exist whoa.

707
00:34:27,040 --> 00:34:29,760
Speaker 2: That is pretty cool, maybe even ice cool.

708
00:34:30,440 --> 00:34:31,480
Speaker 1: It's definitely cosmic.

709
00:34:31,719 --> 00:34:34,040
Speaker 2: All right, Well, we talked about different things that can

710
00:34:34,080 --> 00:34:37,040
Speaker 2: maybe trigger changes in the climate, But the question we're

711
00:34:37,040 --> 00:34:40,320
Speaker 2: asking today is can a supernova from a star blowing

712
00:34:40,400 --> 00:34:43,360
Speaker 2: up far away from here? Can that maybe affect the

713
00:34:43,400 --> 00:34:47,120
Speaker 2: temperature and climate here on Earth? So let's dig into

714
00:34:47,160 --> 00:35:02,960
Speaker 2: that idea. But first let's take another quick break. All right,

715
00:35:03,000 --> 00:35:06,280
Speaker 2: we're asking a question can of supernova cause an ice age?

716
00:35:06,360 --> 00:35:09,160
Speaker 2: Which is kind of a triggy question, right because supernovas

717
00:35:09,160 --> 00:35:14,120
Speaker 2: are big, explosive, hot, deadly impactful, But an ice age

718
00:35:14,120 --> 00:35:17,239
Speaker 2: here on Earth is sort of slow and cold and

719
00:35:19,040 --> 00:35:22,600
Speaker 2: you know, freezing. So how can something exploding far away

720
00:35:22,920 --> 00:35:25,160
Speaker 2: cause things to get cooler here on Earth?

721
00:35:25,239 --> 00:35:27,480
Speaker 1: So the connection is still kind of tenuous, but it's

722
00:35:27,520 --> 00:35:32,399
Speaker 1: sort of fascinating. The idea is that supernovas, they don't

723
00:35:32,440 --> 00:35:34,279
Speaker 1: just go boom and send out a bunch of light

724
00:35:34,320 --> 00:35:37,440
Speaker 1: in the sky. They also send out dust, like little

725
00:35:37,480 --> 00:35:40,960
Speaker 1: bits of those supernovas that get carried along by like

726
00:35:41,040 --> 00:35:44,480
Speaker 1: cosmic and galactic winds and can come here to Earth.

727
00:35:45,040 --> 00:35:47,319
Speaker 1: And when supernovas do go boom, they make sort of

728
00:35:47,440 --> 00:35:50,960
Speaker 1: unique materials. They make stuff that you can't otherwise make

729
00:35:51,040 --> 00:35:53,839
Speaker 1: in the universe because you just don't have the conditions.

730
00:35:54,239 --> 00:35:58,440
Speaker 1: Like stars, they confuse hydrogen into helium, and helium into carbon,

731
00:35:58,480 --> 00:36:00,640
Speaker 1: and carbon into heavier stuff all the way up to

732
00:36:00,680 --> 00:36:03,440
Speaker 1: about iron, but they can't make anything heavier than that

733
00:36:03,480 --> 00:36:06,680
Speaker 1: because above that it costs more energy to fuse than

734
00:36:06,760 --> 00:36:09,920
Speaker 1: fusion creates. So all the heavier elements in the universe

735
00:36:09,960 --> 00:36:13,200
Speaker 1: are made under much more special conditions, such as neutron

736
00:36:13,239 --> 00:36:17,600
Speaker 1: star mergers or during those moments of supernova fusion. The

737
00:36:17,719 --> 00:36:22,160
Speaker 1: explosion that creates the supernova also can create weird new

738
00:36:22,239 --> 00:36:26,200
Speaker 1: heavy isotopes of elements and also heavier elements, and some

739
00:36:26,280 --> 00:36:29,000
Speaker 1: of those bits can fly through the universe and even

740
00:36:29,080 --> 00:36:33,040
Speaker 1: land on Earth, potentially affecting the climate here on Earth.

741
00:36:33,480 --> 00:36:36,680
Speaker 2: Right, Because I think as a start collapses and becomes

742
00:36:36,680 --> 00:36:39,440
Speaker 2: a supernova, it collapses, then it crunches together, and then

743
00:36:39,480 --> 00:36:42,399
Speaker 2: it bounces, and then everything just kind of blows out

744
00:36:42,440 --> 00:36:44,960
Speaker 2: in all directions, and that shock wave is where a

745
00:36:45,000 --> 00:36:47,200
Speaker 2: lot of the heavier elements get made. Because things are

746
00:36:47,200 --> 00:36:51,080
Speaker 2: being exploded out and compressed so much they become heavier elements.

747
00:36:51,120 --> 00:36:53,920
Speaker 2: And you're saying that stuff being flung out can actually

748
00:36:54,000 --> 00:36:55,320
Speaker 2: maybe reach us at some point.

749
00:36:55,480 --> 00:36:57,720
Speaker 1: We know that it has reached us, and we found

750
00:36:57,800 --> 00:37:01,160
Speaker 1: evidence of it here on Earth. This one particular kind

751
00:37:01,160 --> 00:37:03,640
Speaker 1: of element is called iron sixty, so it's a heavy

752
00:37:03,719 --> 00:37:07,080
Speaker 1: isotope of iron. This is something which can be made

753
00:37:07,200 --> 00:37:10,200
Speaker 1: under other normal circumstances. But it's interesting because that's a

754
00:37:10,239 --> 00:37:12,680
Speaker 1: fairly short half life, just like two and a half

755
00:37:12,760 --> 00:37:16,279
Speaker 1: million years. So if it was present on Earth when

756
00:37:16,320 --> 00:37:18,800
Speaker 1: Earth was formed, for example, all of that would have

757
00:37:18,840 --> 00:37:22,200
Speaker 1: decayed away into nickel. So if you find iron sixty

758
00:37:22,280 --> 00:37:25,560
Speaker 1: on Earth, that means it was made fairly recently, sometime

759
00:37:25,600 --> 00:37:28,239
Speaker 1: in the last five to ten million years. But there's

760
00:37:28,280 --> 00:37:31,239
Speaker 1: no process on Earth that can make iron sixty. The

761
00:37:31,280 --> 00:37:33,280
Speaker 1: only way we know that you can make iron sixty

762
00:37:33,400 --> 00:37:35,759
Speaker 1: is in the heart of a star, especially in a supernova.

763
00:37:36,480 --> 00:37:39,279
Speaker 1: And so if you find iron sixty on Earth, that's

764
00:37:39,520 --> 00:37:43,120
Speaker 1: very strong evidence that you found remnants of a supernova

765
00:37:43,280 --> 00:37:46,760
Speaker 1: here on Earth, like supernova dust has landed on Earth.

766
00:37:47,080 --> 00:37:49,400
Speaker 2: WHOA wait, how do you know it's not just really

767
00:37:49,440 --> 00:37:52,240
Speaker 2: old iron sixty from when the Earth was formed? Cann't

768
00:37:52,320 --> 00:37:53,960
Speaker 2: you just have a bunch of it and some of

769
00:37:54,000 --> 00:37:57,160
Speaker 2: it still survived, like we still have uranium on Earth.

770
00:37:57,320 --> 00:37:59,360
Speaker 1: We do still have uranium on Earth. Uranium is on

771
00:37:59,520 --> 00:38:02,440
Speaker 1: much longer half life than a couple of million years.

772
00:38:02,600 --> 00:38:04,839
Speaker 1: The Earth is four and a half billion years, which

773
00:38:04,880 --> 00:38:07,680
Speaker 1: is many, many lifetimes. This stuff has a lifetime of

774
00:38:07,680 --> 00:38:10,840
Speaker 1: two and a half million years. And if there was

775
00:38:10,960 --> 00:38:15,000
Speaker 1: original primordial iron sixty, you would be evenly distributed and

776
00:38:15,040 --> 00:38:17,799
Speaker 1: you'd see a sort of typical decay. Well, what we

777
00:38:17,840 --> 00:38:20,399
Speaker 1: find when we look for iron sixty is we see

778
00:38:20,400 --> 00:38:24,520
Speaker 1: depositions consistent with an increased amount of iron sixty like

779
00:38:24,640 --> 00:38:27,719
Speaker 1: tuish million years ago, and maybe like another deposition like

780
00:38:27,760 --> 00:38:30,239
Speaker 1: a million years ago. It really looks like we got

781
00:38:30,280 --> 00:38:33,719
Speaker 1: fresh doses of iron sixty a couple of times in

782
00:38:33,719 --> 00:38:34,520
Speaker 1: the recent past.

783
00:38:34,760 --> 00:38:38,719
Speaker 2: Well you mean like we've seen basically coatings of the

784
00:38:38,760 --> 00:38:43,920
Speaker 2: Earth with this iron. Yeah, isotope exactly, and there's several coatings.

785
00:38:43,960 --> 00:38:46,520
Speaker 1: There's several coatings, and if you just like dig down

786
00:38:46,600 --> 00:38:48,680
Speaker 1: into the earth, you don't find this stuff. But on

787
00:38:48,719 --> 00:38:51,680
Speaker 1: the ocean floor you do see it, and you can

788
00:38:51,719 --> 00:38:54,360
Speaker 1: see it in the sedimentary layers. You could see it

789
00:38:54,400 --> 00:38:57,480
Speaker 1: like layered at certain times and not other times. And

790
00:38:57,520 --> 00:39:00,920
Speaker 1: so it's really consistent with like the Earth blasted with

791
00:39:01,200 --> 00:39:03,320
Speaker 1: supernova iron sixty.

792
00:39:03,440 --> 00:39:05,040
Speaker 2: Well, I wonder if you would see it on one

793
00:39:05,080 --> 00:39:07,439
Speaker 2: side of the Earth, you know, or not the other,

794
00:39:07,719 --> 00:39:09,680
Speaker 2: or would you see it evenly coating the whole earth.

795
00:39:09,880 --> 00:39:12,040
Speaker 1: Yeah, that's a great question because we'd love to know

796
00:39:12,400 --> 00:39:15,840
Speaker 1: where these supernova were, right, which direction did they come from?

797
00:39:16,280 --> 00:39:18,480
Speaker 1: And if you saw, like where it landed on the Earth,

798
00:39:18,480 --> 00:39:20,840
Speaker 1: you might be able to like reconstruct that not just

799
00:39:20,920 --> 00:39:23,040
Speaker 1: from which side it's on, but like where is it

800
00:39:23,120 --> 00:39:26,400
Speaker 1: more dense? And Unfortunately on Earth, these things tend to

801
00:39:26,400 --> 00:39:28,560
Speaker 1: get swirled around a lot. Like on the ocean floor,

802
00:39:28,880 --> 00:39:31,560
Speaker 1: things get mixed around, and so you can tell it's there,

803
00:39:31,600 --> 00:39:34,000
Speaker 1: and you can tell what year it was deposited. But

804
00:39:34,120 --> 00:39:36,160
Speaker 1: you know, over millions of years, these things do get

805
00:39:36,239 --> 00:39:39,000
Speaker 1: swirled around and spread out. But if we went to

806
00:39:39,040 --> 00:39:41,520
Speaker 1: the Moon, the moon is a much better place to

807
00:39:41,600 --> 00:39:45,279
Speaker 1: keep these sort of ancient geological records because you know,

808
00:39:45,280 --> 00:39:47,279
Speaker 1: there's no weather on the Moon, there's no water, there's

809
00:39:47,280 --> 00:39:49,879
Speaker 1: no air, and so where things landed on the Moon

810
00:39:50,000 --> 00:39:52,759
Speaker 1: is pretty much where they still are. So the Moon

811
00:39:52,920 --> 00:39:55,439
Speaker 1: might have a great snapshot if you measure the iron

812
00:39:55,520 --> 00:39:57,359
Speaker 1: sixty on the surface of the Moon to figure out

813
00:39:57,600 --> 00:39:59,400
Speaker 1: which direction these things came from.

814
00:40:00,880 --> 00:40:03,600
Speaker 2: Well, we've been to the Moon and we've gotten samples

815
00:40:03,600 --> 00:40:06,560
Speaker 2: from there, and what do we find in terms of

816
00:40:06,600 --> 00:40:07,120
Speaker 2: this iron?

817
00:40:07,320 --> 00:40:09,520
Speaker 1: We didn't find very much, But the samples are not

818
00:40:09,560 --> 00:40:11,960
Speaker 1: really the kind you would need to answer this question.

819
00:40:12,440 --> 00:40:14,919
Speaker 1: You know, Apollo landed on the near side of the Moon,

820
00:40:15,080 --> 00:40:17,399
Speaker 1: and much more likely these things landed on the far

821
00:40:17,520 --> 00:40:20,839
Speaker 1: side of the Moon because it's facing out, and so

822
00:40:20,880 --> 00:40:24,640
Speaker 1: we'd need much broader sampling also to like reconstruct the direction.

823
00:40:25,400 --> 00:40:28,080
Speaker 1: And so if you wanted to answer this question from

824
00:40:28,120 --> 00:40:30,600
Speaker 1: samples on the Moon, you need to sample very differently

825
00:40:30,640 --> 00:40:33,040
Speaker 1: from the way Apollo did. So we don't really have

826
00:40:33,120 --> 00:40:35,640
Speaker 1: the data we would need to answer that question. One

827
00:40:35,640 --> 00:40:37,080
Speaker 1: more reason to go back to the moon.

828
00:40:38,000 --> 00:40:40,120
Speaker 2: So the Earth has gone in a few dustings of

829
00:40:40,200 --> 00:40:43,880
Speaker 2: this iron from potentially supernova's. What's the connection to an

830
00:40:43,880 --> 00:40:46,440
Speaker 2: ice age? Then, so there's a couple of things. One

831
00:40:46,520 --> 00:40:48,960
Speaker 2: is they can look at the timing of the supernova

832
00:40:49,320 --> 00:40:51,759
Speaker 2: and it looks like there was a string of supernovas

833
00:40:51,760 --> 00:40:53,960
Speaker 2: that went off in the last ten million years in

834
00:40:54,040 --> 00:40:57,319
Speaker 2: our galaxy. It's like a blob of deposition of iron

835
00:40:57,360 --> 00:41:00,000
Speaker 2: sixty from like one point seven to three point five

836
00:41:00,040 --> 00:41:03,480
Speaker 2: two million years ago. And then there's another deposition like

837
00:41:03,600 --> 00:41:05,640
Speaker 2: two and a half million years ago and another one

838
00:41:05,760 --> 00:41:08,080
Speaker 2: zero point eight million years ago that they think are

839
00:41:08,080 --> 00:41:11,000
Speaker 2: consistent with supernova's that went off like around three hundred

840
00:41:11,080 --> 00:41:13,759
Speaker 2: light years away from the Earth, And the time of

841
00:41:13,800 --> 00:41:16,279
Speaker 2: these things kind of lines up with the timing of

842
00:41:16,320 --> 00:41:18,800
Speaker 2: the ice ages. So if you look at the history

843
00:41:18,800 --> 00:41:20,920
Speaker 2: of the climate on the Earth and you look at

844
00:41:20,920 --> 00:41:22,880
Speaker 2: the history of these supernova, you can like kind of

845
00:41:22,920 --> 00:41:26,359
Speaker 2: line these things up. Now that's just correlational, but it's

846
00:41:26,360 --> 00:41:29,279
Speaker 2: intriguing and it makes people wonder like, hmm, could the

847
00:41:29,400 --> 00:41:32,920
Speaker 2: arrival of this iron sixty on Earth somehow trigger climate

848
00:41:32,920 --> 00:41:36,239
Speaker 2: effects which lead to ice ages? WHOA. But I guess

849
00:41:36,320 --> 00:41:38,880
Speaker 2: maybe one question people might have right now is these

850
00:41:38,920 --> 00:41:41,960
Speaker 2: supernova were super duper far away. Three hundred light years

851
00:41:42,040 --> 00:41:46,120
Speaker 2: is gazillions of kilometers away. Could there still be enough

852
00:41:46,160 --> 00:41:49,040
Speaker 2: iron in that explosion this far out? Wouldn't it be

853
00:41:49,120 --> 00:41:52,200
Speaker 2: super diluted and spread out, it would actually be a

854
00:41:52,239 --> 00:41:53,760
Speaker 2: significant amount that we could see.

855
00:41:53,880 --> 00:41:56,400
Speaker 1: It's a great question, and it highlights the incredible numbers

856
00:41:56,440 --> 00:41:58,399
Speaker 1: that are going on here. Like, first of all, when

857
00:41:58,440 --> 00:42:01,760
Speaker 1: you make a supernova, the mounts of material are vast

858
00:42:02,000 --> 00:42:05,480
Speaker 1: because supernova come from really big stars right, So you're

859
00:42:05,480 --> 00:42:08,600
Speaker 1: starting with an incredible number of atoms. But then, of course,

860
00:42:08,600 --> 00:42:10,919
Speaker 1: as you say, space is huge and we're far away

861
00:42:10,920 --> 00:42:12,680
Speaker 1: from these things, so how are we getting any of them?

862
00:42:13,680 --> 00:42:15,799
Speaker 1: And the answer is that we're not getting many. The

863
00:42:15,960 --> 00:42:20,200
Speaker 1: number of iron sixty atoms, we've recovered numbers in the thousands.

864
00:42:20,719 --> 00:42:23,080
Speaker 1: So we've scoured the planet for these things, and people

865
00:42:23,080 --> 00:42:25,680
Speaker 1: have done these incredible missions to the bottom of the ocean.

866
00:42:25,960 --> 00:42:28,200
Speaker 1: We don't have a lot of examples. We have enough

867
00:42:28,200 --> 00:42:30,720
Speaker 1: to reconstruct the timing of these things to say something

868
00:42:30,719 --> 00:42:34,680
Speaker 1: about which direction maybe they were coming from, but we

869
00:42:34,719 --> 00:42:36,480
Speaker 1: don't have a large number of examples.

870
00:42:36,520 --> 00:42:39,400
Speaker 2: No, meaning, this is a very faint signal.

871
00:42:39,600 --> 00:42:41,799
Speaker 1: It's a pretty faint signal, but it started out so

872
00:42:41,960 --> 00:42:44,799
Speaker 1: bright and so intense that even this far away we

873
00:42:44,880 --> 00:42:45,640
Speaker 1: can't pick it up.

874
00:42:46,880 --> 00:42:50,040
Speaker 2: Now, then, how can this iron affect the climate here

875
00:42:50,040 --> 00:42:50,319
Speaker 2: on Earth?

876
00:42:50,560 --> 00:42:53,320
Speaker 1: So that's something people are more speculating about and trying

877
00:42:53,360 --> 00:42:56,680
Speaker 1: to understand. Is not a solid model here, but you

878
00:42:56,680 --> 00:42:59,640
Speaker 1: can imagine that the arrival of heavy metals in the

879
00:42:59,640 --> 00:43:02,600
Speaker 1: app sphere could change the way things circulate and the

880
00:43:02,600 --> 00:43:05,799
Speaker 1: way things nucleate and the atmosphere chemistry, which is very

881
00:43:05,840 --> 00:43:09,080
Speaker 1: complicated and so there isn't like a very clear argument

882
00:43:09,120 --> 00:43:10,840
Speaker 1: here yet. I mean, I was reading some papers that

883
00:43:10,880 --> 00:43:13,960
Speaker 1: were kind of hand wavy. But the general idea is

884
00:43:14,360 --> 00:43:18,440
Speaker 1: the atmosphere composition is an important component of understanding the climate,

885
00:43:18,640 --> 00:43:21,400
Speaker 1: and changes in the atmosphere can change the climate. We

886
00:43:21,480 --> 00:43:25,080
Speaker 1: know that's true. And so the question is can iron

887
00:43:25,160 --> 00:43:27,720
Speaker 1: sixty or how much iron sixty would have to arrive

888
00:43:28,200 --> 00:43:30,640
Speaker 1: to trigger a change in the climate that might give

889
00:43:30,680 --> 00:43:33,640
Speaker 1: you an ice age. That question is not answered, right.

890
00:43:33,680 --> 00:43:35,560
Speaker 2: It seems like you wouldn't get I mean, if we

891
00:43:35,560 --> 00:43:38,680
Speaker 2: were talking about thousands of atoms, that doesn't seem like

892
00:43:38,680 --> 00:43:41,320
Speaker 2: a lot enough to trigger and ice it. But maybe

893
00:43:41,440 --> 00:43:43,960
Speaker 2: the super wall that send other things besides iron, right, Like,

894
00:43:44,000 --> 00:43:47,040
Speaker 2: maybe it's send other elements, Absolutely a ton of other elements.

895
00:43:47,160 --> 00:43:49,719
Speaker 1: Yeah, And we have found thousands of atoms. Of course,

896
00:43:49,760 --> 00:43:52,360
Speaker 1: we have a tiny detection efficiency, which means there are many,

897
00:43:52,400 --> 00:43:55,759
Speaker 1: many more atoms actually arrived on Earth. And you're absolutely right,

898
00:43:55,760 --> 00:43:58,120
Speaker 1: the iron sixty is just like one of the easiest

899
00:43:58,120 --> 00:44:01,479
Speaker 1: things to identify. Along with it must have come all

900
00:44:01,520 --> 00:44:04,640
Speaker 1: sorts of other debris from the supernova. And when you

901
00:44:04,680 --> 00:44:08,600
Speaker 1: get unusual, weird cosmic dust from space that might trigger

902
00:44:08,719 --> 00:44:11,880
Speaker 1: changes in the atmosphere, but it's kind of speculative. I

903
00:44:11,920 --> 00:44:15,040
Speaker 1: think the most suggestive piece of evidence is the coincidence

904
00:44:15,080 --> 00:44:17,560
Speaker 1: between the timing of the ice ages and the timing

905
00:44:17,600 --> 00:44:20,239
Speaker 1: of these recent supernova although it's hard to tell if

906
00:44:20,239 --> 00:44:21,359
Speaker 1: that's a coincidence or not.

907
00:44:21,640 --> 00:44:24,160
Speaker 2: I see, they seem correlated, they seem to be happening

908
00:44:24,200 --> 00:44:26,399
Speaker 2: at the same time, but we don't know how yet

909
00:44:26,560 --> 00:44:29,000
Speaker 2: or how that's even possible exactly.

910
00:44:29,040 --> 00:44:30,840
Speaker 1: And you know, this is the process of science. You

911
00:44:30,880 --> 00:44:33,400
Speaker 1: see this weird effect, you wonder if they could be connected.

912
00:44:33,719 --> 00:44:36,439
Speaker 1: You look for a mechanism. Rather than just saying, oh, look,

913
00:44:36,480 --> 00:44:38,600
Speaker 1: it happened at the same time, therefore one cause the other.

914
00:44:38,760 --> 00:44:40,640
Speaker 1: You try to dig into it and understand, like, how

915
00:44:40,680 --> 00:44:42,879
Speaker 1: could that be? Is is there a way that could

916
00:44:42,880 --> 00:44:45,640
Speaker 1: really happen, and how could we check that? And so

917
00:44:45,680 --> 00:44:47,600
Speaker 1: some people are working on that right now, like trying

918
00:44:47,640 --> 00:44:50,759
Speaker 1: to understand what kind of supernova debris might trigger a

919
00:44:50,880 --> 00:44:51,960
Speaker 1: change in the atmosphere.

920
00:44:52,640 --> 00:44:55,959
Speaker 2: Interesting. It made me think that you know, the supernovas

921
00:44:56,560 --> 00:45:00,560
Speaker 2: happened really far away, right and they're huge, and which

922
00:45:01,120 --> 00:45:04,239
Speaker 2: maybe affect the entire Milky Way galaxy or a big

923
00:45:04,280 --> 00:45:06,160
Speaker 2: part of the Milky Way galaxy, in which case, like

924
00:45:06,200 --> 00:45:09,239
Speaker 2: one of these supernovas exploding could maybe trigger an ice

925
00:45:09,280 --> 00:45:12,040
Speaker 2: age in a whole bunch of planets around that start, right.

926
00:45:12,120 --> 00:45:16,279
Speaker 1: Yeah, absolutely, And when the supernova happens, it like sterilizes

927
00:45:16,360 --> 00:45:18,880
Speaker 1: the nearby planets. It's cool to think it could have

928
00:45:18,880 --> 00:45:22,239
Speaker 1: a more subtle effect on even further away planets, right,

929
00:45:22,520 --> 00:45:25,000
Speaker 1: it can change the climate of those planets, which could

930
00:45:25,040 --> 00:45:28,000
Speaker 1: really affect the evolution of life on those planets. Like

931
00:45:28,360 --> 00:45:30,960
Speaker 1: maybe life is more likely to become intelligent when there

932
00:45:30,960 --> 00:45:33,400
Speaker 1: are ice ages or when it's oscillating ice ages and

933
00:45:33,400 --> 00:45:36,960
Speaker 1: warm periods. Who knows, right, But supernovas definitely have a

934
00:45:37,040 --> 00:45:40,160
Speaker 1: rippling effect on the whole history of the galaxy, and

935
00:45:40,320 --> 00:45:43,680
Speaker 1: that changes the whole frame for life everywhere in the galaxy.

936
00:45:43,880 --> 00:45:46,360
Speaker 2: Yeah, it's definitely a cool effect. And like you said,

937
00:45:46,440 --> 00:45:49,239
Speaker 2: like maybe it's possible that the only reason we evolved

938
00:45:49,840 --> 00:45:52,400
Speaker 2: is because of a supernova. Like maybe even that supernova

939
00:45:52,480 --> 00:45:55,600
Speaker 2: hadn't happened and sent all this material here, we wouldn't

940
00:45:55,600 --> 00:45:56,120
Speaker 2: have evolved.

941
00:45:56,200 --> 00:45:58,239
Speaker 1: Yeah, or we could have evolved very differently, you know,

942
00:45:58,520 --> 00:46:01,920
Speaker 1: migrated differently, had different patterns and paths if the climate

943
00:46:01,960 --> 00:46:04,800
Speaker 1: were different, and so life on Earth could be vastly

944
00:46:04,840 --> 00:46:06,240
Speaker 1: different without that super Nivah.

945
00:46:06,400 --> 00:46:09,280
Speaker 2: Yeah, without that iron in which case it means Daniel,

946
00:46:09,320 --> 00:46:15,560
Speaker 2: I think that we're all ironmen. It's not just Tony Stark,

947
00:46:17,239 --> 00:46:17,640
Speaker 2: that's right.

948
00:46:17,719 --> 00:46:21,480
Speaker 1: Oh, you don't have to run a marathon and bike

949
00:46:21,560 --> 00:46:24,359
Speaker 1: fifty miles and swimed in miles all the same time

950
00:46:24,400 --> 00:46:26,640
Speaker 1: to be iron man. You just got to live here

951
00:46:26,680 --> 00:46:28,560
Speaker 1: on Earth and listen to podcast.

952
00:46:28,560 --> 00:46:30,960
Speaker 2: And or build an armor, yes, a robotic armor.

953
00:46:31,840 --> 00:46:34,080
Speaker 1: Awesome. Well, I'm looking forward to writing my own saber

954
00:46:34,120 --> 00:46:35,080
Speaker 1: tooth cat to work.

955
00:46:35,760 --> 00:46:38,520
Speaker 2: And then yeah, you're looking forward to jumping your own

956
00:46:38,800 --> 00:46:39,960
Speaker 2: prehistoric shark.

957
00:46:39,840 --> 00:46:42,640
Speaker 1: Right, that's right, exactly, sabertooth shark.

958
00:46:42,840 --> 00:46:45,520
Speaker 2: Yes, or maybe you should start a new meme or term, right,

959
00:46:45,640 --> 00:46:49,560
Speaker 2: jumping the saber tooth tiger. We're jumping the wooly mammoth.

960
00:46:49,680 --> 00:46:52,319
Speaker 2: Oh that sounds even better, you go, yeah, we really

961
00:46:52,400 --> 00:46:54,760
Speaker 2: that podcast was great, but then it jumped the wooly mammoth,

962
00:46:54,840 --> 00:46:57,640
Speaker 2: and you know, now it's even better.

963
00:46:58,160 --> 00:47:01,320
Speaker 1: Yeah, well, maybe we're entering the vast podcast ice age.

964
00:47:01,600 --> 00:47:04,839
Speaker 2: Yeah. Thanks are definitely cooling a little bit here, all right. Well,

965
00:47:04,880 --> 00:47:08,160
Speaker 2: another reminder of how carrious life here on Earth is

966
00:47:08,280 --> 00:47:10,600
Speaker 2: to all of these cosmic events that are happening all

967
00:47:10,640 --> 00:47:13,960
Speaker 2: around this and maybe hopefully make your appreciate the fact

968
00:47:14,000 --> 00:47:16,799
Speaker 2: that we are here talking about these things. And then

969
00:47:16,800 --> 00:47:19,640
Speaker 2: maybe that fact is only possible because of a certain

970
00:47:20,120 --> 00:47:22,479
Speaker 2: string of events that happened billions of years ago.

971
00:47:22,760 --> 00:47:26,120
Speaker 1: Our curiosity to understand the universe continues to burn hot,

972
00:47:26,520 --> 00:47:29,120
Speaker 1: even if the heat of those stars eventually causes an

973
00:47:29,120 --> 00:47:29,840
Speaker 1: ice age.

974
00:47:30,160 --> 00:47:30,319
Speaker 4: Right.

975
00:47:30,360 --> 00:47:33,919
Speaker 2: We hope you enjoyed that. Thanks for joining us, See

976
00:47:33,920 --> 00:47:34,480
Speaker 2: you next time.

977
00:47:39,320 --> 00:47:42,200
Speaker 1: For more science and curiosity, come find us on social

978
00:47:42,239 --> 00:47:47,160
Speaker 1: media where we answer questions and post videos. We're on Twitter, Discord, Instant,

979
00:47:47,239 --> 00:47:50,960
Speaker 1: and now TikTok. Thanks for listening, and remember that Daniel

980
00:47:50,960 --> 00:47:54,440
Speaker 1: and Jorge Explain the Universe is a production of iHeartRadio.

981
00:47:54,719 --> 00:47:59,799
Speaker 1: For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts,

982
00:48:00,080 --> 00:48:02,320
Speaker 1: or wherever you listen to your favorite shows.