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Speaker 1: Hey Daniel, it's been a long time. Did you have

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Speaker 1: a nice holiday with your family? We did, thank you

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Speaker 1: very much. We did some of our favorite holiday traditions. Oh,

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Speaker 1: like like you cooked specific meals that you only cook

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Speaker 1: once a year or something like that. Well, you know,

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Speaker 1: one of our favorite holiday traditions is a little bit unusual.

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Speaker 1: It's trash Day, like when you roll your bins to

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Speaker 1: the street because I call that Tuesday. Does that count

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Speaker 1: as a holiday? CD? No? No, No. Trash Day is

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Speaker 1: a much bigger deal. It's when you take all the

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Speaker 1: stuff out of your closets, decide what you actually need,

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Speaker 1: and donate or throw away the rest of it. Oh,

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Speaker 1: I bet you find some real treasures. You know, every

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Speaker 1: year we try to go one layer deeper into the

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Speaker 1: archaeology of our closets. Do you think you'll ever reach

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Speaker 1: the back. I'm not even convinced a back exists anymore.

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Speaker 1: It might just be like an infinite stack of useless junk. Well,

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Speaker 1: maybe you'll get lucky and it will have compressed for

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Speaker 1: long enough that it will become diamonds or something, or

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Speaker 1: be a black hole in there that'll just eat you.

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Speaker 1: That's not lucky, that's less lucky. That's still interesting. Hi.

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Speaker 1: I'm Daniel. I'm a professor at UC Irvine and a

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Speaker 1: particle physicist, and I love throwing stuff away. I'm Kelly

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Speaker 1: Wayder Smith. I'm a parasitologist with Rice University, and I

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Speaker 1: love throwing stuff away. But my family doesn't know. Do

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Speaker 1: you guys have arguments about how many nostalgic elements to keep? Yes,

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Speaker 1: that might be the thing we argue about the most often. Actually,

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Speaker 1: And are you ever right where they really need something?

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Speaker 1: And you're like, Hi, you shouldn't have thrown away that

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Speaker 1: melon baller. I knew we would come in Andy very rarely.

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Speaker 1: And also, you know, with things like Amazon, it could

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Speaker 1: show up at your house in less than a day.

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Speaker 1: So even if I'm wrong, you can just get a

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Speaker 1: new melon baller. That's true. Amazon has undermined your argument.

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Speaker 1: That's right, That's right. You can always just use the spoon.

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Speaker 1: Am I right? Well? I feel like you might appreciate

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Speaker 1: the melonballer, but you'll appreciate the lack of the melonballer

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Speaker 1: even more. You know, nothing is better than negative space.

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Speaker 1: If you've succeeded in like cleaning out a closet or

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Speaker 1: cleaning out some corner of your room, and then you

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Speaker 1: can just appreciate the emptiness. I agree, I like not

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Speaker 1: trimping over things in the middle of the night because

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Speaker 1: I get up a lot the middle of the night.

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Speaker 1: I value that well. Welcome to the podcast Daniel and

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Speaker 1: Jorge Explain the Universe, in which we explore the meaning

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Speaker 1: of nothingness and the very fabric of space itself. We

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Speaker 1: take the whole universe apart from the junk in your closets,

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Speaker 1: to the junk between your toes, to the junk that

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Speaker 1: fills the whole cosmos. We want to understand it. We

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Speaker 1: want to take it apart. We want to understand what

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Speaker 1: it means when it's there and it's not there, and

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Speaker 1: how it all got to be the way that it is.

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Speaker 1: So what are we working on today? Then? Today we

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Speaker 1: are thinking about the universe as a sort of mystery.

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Speaker 1: I like to think of physicists as like detectives trying

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Speaker 1: to crack the murder mystery of the universe, Like what

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Speaker 1: happened here? We are showing up at the scene and

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Speaker 1: wondering how did it all get to be the way

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Speaker 1: that it is? And today you get to be the

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Speaker 1: forensic scientist that dates the dead body. That's always a

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Speaker 1: good character. That's right, because when you show but the scene,

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Speaker 1: you want to understand what happened. You want to put

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Speaker 1: things in order. You want to say, what this happened,

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Speaker 1: then that happened, then the other happened, like the Solar

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Speaker 1: system formed and then the Earth cooled and then life

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Speaker 1: evolved on the planet, or the Big Bang happened, and

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Speaker 1: then helium formed, and then much much later stars happened.

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Speaker 1: The whole point of doing science is to put the

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Speaker 1: universe in some sort of order. That's what a story is.

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Speaker 1: And I'm a firm believer in the philosophy that human

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Speaker 1: thinking is mostly about storytelling. And so in order to

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Speaker 1: do that, you have to figure out why, how old

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Speaker 1: is stuff, what came before what other stuff? You need

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Speaker 1: to have dates and clocks and times if you're going

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Speaker 1: to unravel the murder mystery of the universe. And there's

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Speaker 1: a lot of different ways that we've done that throughout

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Speaker 1: the years, and some of them work better for particular

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Speaker 1: kinds of mysteries than others. So what sort of mysteries

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Speaker 1: are we solving today? Well, of course we are interested

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Speaker 1: in the mysteries of deep time. What happened in the

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Speaker 1: first few moments of the universe. How long has the

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Speaker 1: Earth been around? And what's been going on? How did

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Speaker 1: everything come together? One of my favorite things about dating

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Speaker 1: stuff is discovering those surprises, those realizations like wow, oh

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Speaker 1: my gosh, the Earth is so much older than anybody

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Speaker 1: ever imagined, or that the universe is shockingly old, or

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Speaker 1: you know, for some people the universe might be shockingly young.

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Speaker 1: Maybe some people bought the universe had been around forever

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Speaker 1: or trillions of years. So anytime you get one of

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Speaker 1: these dates, it's this glorious moment where you get to

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Speaker 1: like pin down the universe and say, ah, now I

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Speaker 1: know something about you, and that like eliminates a bunch

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Speaker 1: of possibilities. When you're a reader digesting a mystery novel,

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Speaker 1: you have like lots of different options in your head.

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Speaker 1: Maybe it was this person, maybe it was that person,

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Speaker 1: maybe it was this third person. And as you get clues,

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Speaker 1: you get to eliminate possibilities, which finally reveals to you

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Speaker 1: the truth, right, what actually happened in the universe. The

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Speaker 1: story is revealed by elimination, and so those clues are

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Speaker 1: absolutely essential. But you're right, Kelly, that there's lots of

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Speaker 1: different ways to date things in the universe, and today

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Speaker 1: we're gonna be focusing on something a little bit more recent,

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Speaker 1: how we can use physics to understand fairly recent history

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Speaker 1: here on Earth. Oh, that sounds a lot less disgusting

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Speaker 1: than using flymaggots. Fly maggots, what are you talking about?

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Speaker 1: That's for dating things like you know, dead bodies that

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Speaker 1: you find like what stage are the fly eggs that

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Speaker 1: have been laid on the body? So that's you know,

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Speaker 1: we're working with like days to weeks there. So are

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Speaker 1: we working on that skill or are we working like

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Speaker 1: past the writing DiPT in phase. Definitely past the rotting

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Speaker 1: corpse phase. But I think you put your finger on

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Speaker 1: a really interesting point, which is that there are all

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Speaker 1: these clocks build into nature, right like maggots take a

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Speaker 1: certain amount of time to digest a corpse, or rocks

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Speaker 1: take a certain amount of time to cool, and these

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Speaker 1: clocks are things we can take advantage of in order

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Speaker 1: to figure out how old things are, how long they've

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Speaker 1: been digesting, or how long they've been cooling, or how

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Speaker 1: long they've been radioactively decaying. We don't get to like

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Speaker 1: design these things go back in the past and like

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Speaker 1: leave clocks in place to tell us how long things took. Instead,

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Speaker 1: we have to just take advantage of the clocks that

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Speaker 1: we find. And some of these clocks, as you say,

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Speaker 1: are really short lived, like they tell us about things

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Speaker 1: that happened just for over weeks. Some of them can

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Speaker 1: tell us about things that happened for billions of years,

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Speaker 1: and other ones can tell us about things that happened

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Speaker 1: in the last ten fifty thousand years, which is a

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Speaker 1: super interesting time for the story of human civilization, how

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Speaker 1: we got to be who we are. And of course,

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Speaker 1: it turns out physics plays a big role. I love

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Speaker 1: learning about this topic because it's so exciting to me

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Speaker 1: how we figure out what tools are the best ones

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Speaker 1: to use to explore the past. And I specifically like

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Speaker 1: hearing about sort of physics and chemistry sorts of tools

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Speaker 1: because my sense is that they're a little bit less

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Speaker 1: susceptible to uncertainty. So, for example, you know, temperature can

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Speaker 1: impact how fast those flies are developing. But maybe today

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Speaker 1: you're going to explain to me that chemistry and physics

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Speaker 1: aren't that straightforward either. It turns out to be a

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Speaker 1: twisty and complicated topic. And of course sewage is involved. Yea,

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Speaker 1: my wife is very happy to hear about that. And

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Speaker 1: so today on the podcast, we'll be answering the question

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Speaker 1: how does radiocarbon dating work? Well, should we start by

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Speaker 1: seeing what the listeners think? Yes, absolutely, I was curious

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Speaker 1: to hear what people had to say about this. Radiocarbon

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Speaker 1: dating is something I think a lot of people have

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Speaker 1: heard about. It's on television all the time, and we

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Speaker 1: date this and we date that. But I was wondering

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Speaker 1: if people like really understood the mechanism of it, like

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Speaker 1: what the physics is of these clocks? Why is there

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Speaker 1: a clock? Why does it start when you die? And

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Speaker 1: how do we read it out? So thanks very much

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Speaker 1: to everyone who participates in this segment of the podcast,

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Speaker 1: sharing your thoughts without a chance to prepare. If you

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Speaker 1: would like to participate in the future, please don't be shy.

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Speaker 1: I'll be gentle. It's fun. Just write to me two

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Speaker 1: questions at Daniel Njorge dot com. So before you hear

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Speaker 1: these answers, think to yourself, do you know how radiocarbon

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Speaker 1: dating works? Here's what people had to say. If we

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Speaker 1: find some animal spoon, let's say some dinosaur spone, but

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Speaker 1: it inside the Earth, and then we calculate the amount

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Speaker 1: of carbon cfteen specifically present in it. Through those calculations,

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Speaker 1: we can easily calculate the age of that skeleton. I've

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Speaker 1: heard it get called carbon fourteen dating before, so that

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Speaker 1: makes me think that it has something to do with

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Speaker 1: the isotope and the decay of that carbon. Adam, you

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Speaker 1: can do tet the age of organic objects by looking

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Speaker 1: at the ratio of carbon isotopes. I feel like carbon

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Speaker 1: dating is when like two particles of carbon or like connected.

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Speaker 1: I don't know, I don't really know anything about that.

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Speaker 1: I felt like the answers to these fell into two camps.

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Speaker 1: People who sounded like they really knew what they were

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Speaker 1: talking about and people who had maybe not even heard

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Speaker 1: of carbon dating. And to me, that's it's sort of

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Speaker 1: interesting that it's like an either or scenario, like maybe

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Speaker 1: either you're into the kinds of TV shows that this

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Speaker 1: is shown in, or maybe you're not watching and cis

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Speaker 1: or what was that ship bones where the archaeologist was

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Speaker 1: doing carbon fourteen dating? Yeah, what do you think? I

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Speaker 1: was pretty tickled by the answer that suggested that, like

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Speaker 1: carbon fourteen atoms are like hooking up. You know, they're

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Speaker 1: like on Tinder, He's still finding each other and making magic.

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Speaker 1: It was a clever the cuff response there. Yeah, I

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Speaker 1: like our listeners are funny, funny people, absolutely, and I

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Speaker 1: had a lot of fun digging into the details of this.

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Speaker 1: This is not something I use in my research and

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Speaker 1: so not something i'd really ever wrapped my mind around.

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Speaker 1: And one of my favorite things about this podcast is

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Speaker 1: that I get an excuse to go off and learn

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Speaker 1: about something I always wanted to understand but never really

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Speaker 1: given myself the time to dig into. So thanks for

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Speaker 1: the listener who suggested this topic. How can listeners suggest

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Speaker 1: topics to you? Just shoot you an email. Absolutely, if

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Speaker 1: there's something you'd like to understand, please just write to

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Speaker 1: me to questions at Daniel and jorhe dot com. We

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Speaker 1: put it on our list and we get to every

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Speaker 1: single one eventually. And I'm with you. There are a

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Speaker 1: few things I enjoy more than an excuse to study

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Speaker 1: a topic that's interesting that isn't part of my research program.

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Speaker 1: I know, And it's weird that sometimes you feel like

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Speaker 1: you need an excuse, you know, you don't just like

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Speaker 1: get to slice off a few hours of your day

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Speaker 1: and go read about how something works. For some reason,

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Speaker 1: I feel like I have to give myself the opportunity

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Speaker 1: and having to do a podcast on it, explained of

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Speaker 1: the books is a good excuse to go and actually

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Speaker 1: learn how something works. That is one of the weird

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Speaker 1: things about academia. You don't feel like you have a

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Speaker 1: lot of time to just sit and think. But I too,

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Speaker 1: have created a bunch of tricks in my life, you know, like, oh,

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Speaker 1: I'm going to write a book about ten emerging technology,

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Speaker 1: so I have to read about all of them and

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Speaker 1: so yeah, but at least we have these tricks, all right.

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Speaker 1: So what is carbon fourteen? Right? So, radiocarbon dating or

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Speaker 1: carbon fourteen dating uses this weird form of carbon called

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Speaker 1: carbon fourteen. And when we say carbon fourteen, that number

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Speaker 1: fourteen tells us how many nucleons there are in the atom.

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Speaker 1: So remember that an atom has electrons around it, and

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Speaker 1: in the nucleus there are protons and neutrons. Now, usually

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Speaker 1: carbon has six protons and six neutrons, and so that's

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Speaker 1: carbon twelve. That's like the vanilla kind of carbon, the

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Speaker 1: kind that makes up most of you. And if it's

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Speaker 1: in carbon dioxide, and everywhere in the atmosphere. So that's

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Speaker 1: carbon twelve, which is stable. Carbon fourteen is a weird

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Speaker 1: version of carbon. It's still carbon, So there are six

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Speaker 1: protons inside, but there's two extra neutrons, so it's like

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Speaker 1: a heavier nucleus. So that's what carbon fourteen is. And

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Speaker 1: do those neutrons want to stay there or do they

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Speaker 1: want to escape? So you know, the stability of the

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Speaker 1: nucleus is a really interesting and complicated question. Some collections

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Speaker 1: of protons and neutrons are stable. You can build carbon

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Speaker 1: twelve and have it sit in space and come back

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Speaker 1: a billion years later and it'll still be carbon twelve.

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Speaker 1: Other constructions are not stable, Like you had two more

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Speaker 1: neutrons and all of a sudden you have carbon fourteen.

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Speaker 1: It's not stable. It will fall apart after a few

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Speaker 1: thousand years. And this all comes down to how those

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Speaker 1: protons and neutrons like to put themselves together inside the nucleus.

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Speaker 1: Remember that the nucleus is only protons and neutrons, and

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Speaker 1: the protons are positively charged. The neutrons are neutral, of course,

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Speaker 1: and so initially you might wonder, like, well, how does

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Speaker 1: the nucleus stay together anyway? It's all positive charges. Why

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Speaker 1: don't they just blow each other apart? And there is

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Speaker 1: that desire, right, They definitely are pushing against each other,

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Speaker 1: But on the other hand, they're held together by a

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Speaker 1: much stronger force. The strong nuclear force sticks the protons

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Speaker 1: and the neutrons all together. So it's a delicate balance

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Speaker 1: in some cases between the strong force sticking it together

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Speaker 1: and the electromagnetic force trying to push it apart. You

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Speaker 1: have one prototon and one neutron held together by the

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Speaker 1: strong nuclear force. That's stable. And then when you've got

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Speaker 1: extra neutrons floating around so that they don't pair evenly,

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Speaker 1: is that what makes it unstable? Yeah, that's right. You

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Speaker 1: can actually think about the construction of the nucleus in

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Speaker 1: a similar way to how we think about electron orbitals.

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Speaker 1: You remember learning in like high school chemistry. The electrons

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Speaker 1: aren't all just buzzing around the nucleus the same way.

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Speaker 1: It's like one in the lowest energy level and another

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Speaker 1: one in the next energy level. They sort of fill

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Speaker 1: up and they get to like more and more elaborate

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Speaker 1: orbitals as they get to higher and higher energy. Well,

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Speaker 1: the nucleus is constructed sort of in the same way.

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Speaker 1: The picture you often have of the nucleus is just

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Speaker 1: like a scoopful of protons and neutrons, But that's not

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Speaker 1: really very accurate. It's more like there are shells, you're

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Speaker 1: like an inner core or protons and neutrons have clicked together,

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Speaker 1: and then you can surround that with another layer of

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Speaker 1: like protons and neutrons, and the most stable atoms are

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Speaker 1: the ones where those layers are filled. You've like clicked

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Speaker 1: in all the protons and neutrons. It's sort of like

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Speaker 1: making a roman arch. When you have all the bricks together,

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Speaker 1: they click together to make a very stable structure. If

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Speaker 1: you're just missing one, then it can be very unstable.

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Speaker 1: So I didn't do great in high school chemistry? Is

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Speaker 1: the reason that that sounds new to me? Because we've

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Speaker 1: learned this in the twenty plus years since I've been

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Speaker 1: in high school? Or is that something we usually just

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Speaker 1: sort of, you know, skip over in high school, or

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Speaker 1: what's the story there? How long have we known that? Well?

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Speaker 1: I think we're gonna have to interview your high school

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Speaker 1: chemistry teacher to really find the answer to that. Let's

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Speaker 1: dig deep into your past. In fact, we have them

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Speaker 1: here on the podcast Surprise Surprise is Your Life, Kelly,

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Speaker 1: I don't think they like to be very much. Let's

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Speaker 1: move on. No, my high school chemistry teacher would not

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Speaker 1: be happy to hear from me either. I think it's

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Speaker 1: a combination of both things. We have understood what's going

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Speaker 1: on in the nucleus much much better in the last

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Speaker 1: few decades because we've been shooting stuff at it and

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Speaker 1: breaking it up and seeing what's inside of it, and

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Speaker 1: it's a hard project. We've also been building heavier and

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Speaker 1: heavier nuclei to understand, like what are the limits of stability?

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Speaker 1: How many protons and neutrons can you stick together and

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Speaker 1: have something which will stick around for billions of years.

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Speaker 1: We have a whole podcast episode about what are the

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Speaker 1: heaviest stable atoms And we think, for example, there might

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Speaker 1: be an island of stability where you get like hundreds

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Speaker 1: of protons and neutrons stuck together to make new super

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Speaker 1: heavy stable elements nobody's ever seen before. So it's a

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Speaker 1: complex field of study and it's probably not taught in

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Speaker 1: high school chemistry because it's evolving, and also because it's messy,

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Speaker 1: and I don't think that high school sophomores aren't necessarily

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Speaker 1: ready for it. I'm not sure that I was ready

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Speaker 1: for the electron stuff either, But all right, so these

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Speaker 1: things aren't stable, and every once in a while the

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Speaker 1: neutrons get picked out. How long are we talking before

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Speaker 1: the neutrons get picked doubt? Does it take like weeks? Years, millennia?

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Speaker 1: What are we looking at? So every atom is different. Uranium,

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Speaker 1: for example, has a half life which is like the

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Speaker 1: age of the Earth, but carbon fourteen only lasts about

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Speaker 1: fifty seven hundred years. Now, remember when we say that,

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Speaker 1: we don't mean that there's like a little clock inside

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Speaker 1: every carbon and when the time expires, it dies. What

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Speaker 1: we mean is that that's how long it takes, like

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Speaker 1: a population of carbon atoms for half of them to decay.

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Speaker 1: Each individual one might take longer or less time, because

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Speaker 1: fundamentally it's a quantum mechanical effect. There's a randomness to

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Speaker 1: win these things decay. So like five seven hundred years,

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Speaker 1: that's much longer than any of us live. And so

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Speaker 1: certainly there was no scientists who was sitting around, you know,

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Speaker 1: watching these things for five thousand, seven hundred years. How

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Speaker 1: do we figure something like that out? That's a great question,

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Speaker 1: And you know if it did take fifty seven hundred

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Speaker 1: years for every carbon atom to decay, then you couldn't

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Speaker 1: measure that half life without waiting for the first one

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Speaker 1: to decay, would literally take thousands of year years After

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Speaker 1: one thousand years or three thousand years, you would have

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Speaker 1: seen none decay, and you still wouldn't know is the

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Speaker 1: half life five thousand years or five billion years right?

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Speaker 1: And you wouldn't get ten year. You need a very

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Speaker 1: understanding department chare that's right. And so it's the statistical

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Speaker 1: nature of that, the randomness that really helps you because

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Speaker 1: even though the half life is five thousand, seven hundred years,

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Speaker 1: after one hundred years, there is a chance that a

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Speaker 1: few of them will have decayed. So all you need

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Speaker 1: is like a lot of carbon atoms, millions and billions

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Speaker 1: and zillions. Unfortunately, there are a lot of them around,

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Speaker 1: and you just watch for a few years or even

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Speaker 1: a few months, and a few of them will decay,

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Speaker 1: and from that you can extrapolate. Right as soon as

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Speaker 1: you start to see some of them decay, you know

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Speaker 1: how likely it is for any of them to decay,

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Speaker 1: and from that you can calculate how long it would

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Speaker 1: take for half of them to decay as a decay

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Speaker 1: is does it go from carbon fourteen the carbon thirteen,

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Speaker 1: the carbon twelves, or does it go right from fourteen

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Speaker 1: to twelve? Does it lose two neutrons all in one step?

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Speaker 1: So actually, carbon fourteen doesn't decay to carbon twelve. What

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Speaker 1: it does when it decays is that it goes to nitrogen.

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Speaker 1: Like normal nitrogen is nitrogen fourteen, but it has seven protons.

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Speaker 1: So you go from something which has eight neutrons and

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Speaker 1: six protons that's carbon fourteen, into something that has seven

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Speaker 1: neutrons and seven protons. So you take one of the

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Speaker 1: neutrons and you do a beta decay into a proton,

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Speaker 1: and now carbon fourteen has flipped into nitrogen fourteen. And

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Speaker 1: to me, this is really cool because this is the

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Speaker 1: quantum mechanics of it. Like carbon fourteen is not totally stable,

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Speaker 1: but it's also not totally unstable, like it will stick

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Speaker 1: around for a long long time. It's like a particle

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Speaker 1: trapped in a little potential well, and nitrogen fourteen is

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Speaker 1: other state it can flip into is also a little

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Speaker 1: potential well. And like classically, if you had a particle

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Speaker 1: trapped in a little well, it could never get out.

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Speaker 1: So what happens is that this atom switches from one

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Speaker 1: state to another state even though there's like a potential

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Speaker 1: barrier in between it. It does this by quantum tunneling.

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Speaker 1: It's like an electron stuck in one little hole that

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Speaker 1: ends up in another little hole, even though it doesn't

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Speaker 1: have the energy to go over the barrier. So carbon

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Speaker 1: fourteen turns into nitrogen fourteen through this random quantum mechanical

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Speaker 1: tunneling process that lets a switch from one state to

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Speaker 1: a lower energy state without having enough energy to actually

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Speaker 1: go over the barrier in between them. That's another thing

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Speaker 1: I'm amazed we ever managed to figure out. I know,

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Speaker 1: so like quantum mechanics is happening all over the place

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Speaker 1: in the atmosphere right in front of us. That's crazy.

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Speaker 1: So where do we get carbon fourteen in the first place? Yeah,

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Speaker 1: carbon fourteen only sticks around for a few thousand years.

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Speaker 1: So you might wonder, like the Earth is billions of

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Speaker 1: years old, why do we have a new carbon fourteen?

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Speaker 1: And the only reason we do is that we have

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Speaker 1: a source of it, right, this new carbon fourteen being

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Speaker 1: made all the time, and of course it comes from space.

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Speaker 1: The Earth is not just sitting out in empty space.

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Speaker 1: Space is very far from We're being inundated with high

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Speaker 1: energy particles all the time, from the Sun, from black

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Speaker 1: hole accretion disks, from other galaxies. All sorts of stuff

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Speaker 1: are smashing into the Earth all the time. And then

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Speaker 1: we call these things cosmic rays, and when they hit

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Speaker 1: the upper atmosphere, they cause all sorts of reactions. They

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Speaker 1: smash into stuff and they change it. What happens is

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Speaker 1: a cosmic ray will smash into like a proton that's

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Speaker 1: in nitrogen, which is seven P seven N, and convert

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Speaker 1: it into a neutron. So you have nitrogen fourteen smash

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Speaker 1: banging with a proton, and you end up with carbon

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Speaker 1: fourteen because one of those protons has gotten converted into

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Speaker 1: a neutron. WHOA Okay, And that's all happening in the

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Speaker 1: atmosphere and not happening much on Earth, Is that right?

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Speaker 1: That's right, It's happening mostly in the upper atmosphere. Cosmic

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Speaker 1: rays can't just fly through the atmosphere. They interact with particles.

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Speaker 1: It's sort of like running into a crowd, right, You're

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Speaker 1: going to bang into all the other particles. Because cosmic

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Speaker 1: rays they're just particles. They sound spooky and weird, but

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Speaker 1: they're just particles. So these things are created in the

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Speaker 1: atmosphere and then they sort of drift down to the

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Speaker 1: rest of the planet. Okay, all right, so now we

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Speaker 1: know how we get carbon fourteen, and we should take

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Speaker 1: a break and when we come back, we'll talk about

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Speaker 1: how it goes from the atmosphere to being incorporated into

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Speaker 1: living things. And we're back. Okay. So carbon fourteen, made

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Speaker 1: by cosmic rays in the atmosphere, falls down towards the

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Speaker 1: living stuff that lives below. And then what happens, Daniel,

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Speaker 1: So carbon fourteen interacts with oxygen in the atmosphere to

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Speaker 1: make carbon dioxide, and so now you have these special

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Speaker 1: molecules of carbon dioxide. Most of the carbon dioxide in

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Speaker 1: the atmosphere has carbon twelve in its normal stuff, but

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Speaker 1: about one in a trillion has a carbon fourteen atom,

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Speaker 1: So it's carbon fourteen plus two normal oxygens. And this

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Speaker 1: is just floating out there around in the atmosphere. And

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Speaker 1: so when plants, for example, do photosynthesis and they breathe

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Speaker 1: in carbon dioxide, most of the time they're breathing in

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Speaker 1: normal vanilla carbon dioxide, but sometimes one in a trillion

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Speaker 1: to get the extra spicy version of carbon dioxide that

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Speaker 1: has carbon fourteen in it, so they take it in

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Speaker 1: and then when you eat your impossible burger, which is

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Speaker 1: made out of plants, you're eating that carbon fourteen that

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Speaker 1: got incorporated into the plant. So do plants have more

430
00:22:28,960 --> 00:22:33,199
Speaker 1: carbon fourteen than animals because they're sucking so much of

431
00:22:33,200 --> 00:22:35,440
Speaker 1: it out of the atmosphere or is that not how

432
00:22:35,480 --> 00:22:39,520
Speaker 1: it works? Carbon fourteen definitely flows through the sort of biosphere,

433
00:22:39,560 --> 00:22:41,560
Speaker 1: and its richest at the source. Like if you go

434
00:22:41,600 --> 00:22:45,000
Speaker 1: into the upper atmosphere, that's the highest fraction of carbon fourteen.

435
00:22:45,280 --> 00:22:47,480
Speaker 1: As you get further and further away from the source,

436
00:22:47,720 --> 00:22:50,200
Speaker 1: you get less and less carbon fourteen because it starts

437
00:22:50,200 --> 00:22:53,440
Speaker 1: to decay. Now it decays a really, really slowly, So

438
00:22:53,520 --> 00:22:56,000
Speaker 1: like most plants and most animals on the surface have

439
00:22:56,080 --> 00:22:58,879
Speaker 1: about as much carbon fourteen in them as exist in

440
00:22:58,920 --> 00:23:01,480
Speaker 1: the upper atmosphere. Like the bottom of the ocean, the

441
00:23:01,600 --> 00:23:05,639
Speaker 1: deep ocean doesn't interact with the atmosphere as often, and

442
00:23:05,680 --> 00:23:08,360
Speaker 1: so the rate of carbon fourteen down there is much

443
00:23:08,440 --> 00:23:10,720
Speaker 1: less because it takes longer to get down there, and

444
00:23:10,720 --> 00:23:13,200
Speaker 1: by the time it does, some of it has decayed.

445
00:23:13,760 --> 00:23:16,600
Speaker 1: And so like deep ocean animals tend to have less

446
00:23:16,640 --> 00:23:19,680
Speaker 1: carbon fourteen than like birds that live in the high

447
00:23:19,720 --> 00:23:22,439
Speaker 1: atmosphere or you know, cows that live on the surface.

448
00:23:22,480 --> 00:23:25,679
Speaker 1: We can actually map the carbon fourteen fraction over the

449
00:23:25,680 --> 00:23:28,719
Speaker 1: biosphere and see how that flows. Okay, And so in general,

450
00:23:28,760 --> 00:23:31,840
Speaker 1: we're also not really interested in like you know, there

451
00:23:31,840 --> 00:23:35,119
Speaker 1: are one hundred units of carbon fourteen in a tree.

452
00:23:35,200 --> 00:23:40,200
Speaker 1: We're interested in the relative amounts of carbon twelve compared

453
00:23:40,240 --> 00:23:43,200
Speaker 1: to carbon fourteen. Is that right? So it's about relative

454
00:23:43,200 --> 00:23:46,200
Speaker 1: amounts as opposed to absolute quantities. Yeah, exactly. And this

455
00:23:46,280 --> 00:23:49,400
Speaker 1: is the really fascinating bit about carbon fourteen. Right. First

456
00:23:49,440 --> 00:23:51,359
Speaker 1: of all, it's a natural clock. It's this thing that

457
00:23:51,440 --> 00:23:54,439
Speaker 1: happens in the universe. You create carbon fourteen, you have

458
00:23:54,440 --> 00:23:58,119
Speaker 1: about fifty seven hundred years until it decays. The fascinating

459
00:23:58,119 --> 00:24:00,359
Speaker 1: thing about carbon fourteen is that we use it to

460
00:24:00,480 --> 00:24:04,439
Speaker 1: date when something dies, right, we can tell when something

461
00:24:04,480 --> 00:24:07,639
Speaker 1: has died. And when I first heard about this, I thought, what,

462
00:24:08,000 --> 00:24:11,119
Speaker 1: how does like the carbon know that you've died. Is

463
00:24:11,119 --> 00:24:13,159
Speaker 1: it like as soon as you die your carbon fourteen

464
00:24:13,200 --> 00:24:16,000
Speaker 1: atoms start ticking or something. I thought that was really weird,

465
00:24:16,040 --> 00:24:19,000
Speaker 1: because you know, life and death is this holistic property

466
00:24:19,000 --> 00:24:21,800
Speaker 1: of an object, and like the carbon fourteen doesn't care

467
00:24:21,880 --> 00:24:24,359
Speaker 1: if you're alive or dead. Right, So the reason that

468
00:24:24,400 --> 00:24:27,240
Speaker 1: carbon fourteen is sensitive to your moment of death is

469
00:24:27,320 --> 00:24:29,680
Speaker 1: because of what you stop doing when you die, which

470
00:24:29,760 --> 00:24:32,479
Speaker 1: is you stop breathing and you stop eating, so you

471
00:24:32,520 --> 00:24:36,000
Speaker 1: stop getting new carbon fourteen. So all the carbon fourteen

472
00:24:36,080 --> 00:24:39,120
Speaker 1: in your body is always decaying. Like that clock started

473
00:24:39,240 --> 00:24:41,399
Speaker 1: when the cosmic array hit in the upper atmosphere, and

474
00:24:41,400 --> 00:24:43,600
Speaker 1: maybe it took a few hundred years before you ate

475
00:24:43,640 --> 00:24:46,520
Speaker 1: that carbon fourteen, and so that clock has already started.

476
00:24:46,600 --> 00:24:49,080
Speaker 1: What doesn't happen anymore when you die is that you

477
00:24:49,119 --> 00:24:51,879
Speaker 1: don't get any fresh carbon fourteen, and so now the

478
00:24:51,920 --> 00:24:54,439
Speaker 1: carbon fourteen in your body is decaying and it's not

479
00:24:54,560 --> 00:24:57,600
Speaker 1: being replaced. So something that died a long time ago

480
00:24:57,720 --> 00:25:00,320
Speaker 1: will have almost no carbon fourteen in it. If you

481
00:25:00,359 --> 00:25:02,639
Speaker 1: died ten minutes ago, you still have a lot of

482
00:25:02,680 --> 00:25:05,200
Speaker 1: carbon fourteen in you. So it's not really like the

483
00:25:05,240 --> 00:25:07,760
Speaker 1: moment of death. It's more like the moment you stopped

484
00:25:07,840 --> 00:25:11,239
Speaker 1: participating in the biosphere, which I guess is really the

485
00:25:11,280 --> 00:25:13,880
Speaker 1: same thing. Do you like the microbes that break you

486
00:25:14,000 --> 00:25:17,760
Speaker 1: down put some more carbon fourteen in there to mess

487
00:25:17,800 --> 00:25:19,760
Speaker 1: the clock up a little. I guess it doesn't matter,

488
00:25:19,760 --> 00:25:22,080
Speaker 1: because if the half life is five thousand, seven hundred years,

489
00:25:22,119 --> 00:25:24,639
Speaker 1: we're talking about like a week or two of microbes

490
00:25:24,680 --> 00:25:27,159
Speaker 1: messing up the values. Yeah, good question. I guess it

491
00:25:27,200 --> 00:25:30,199
Speaker 1: depends a little bit if they're aerobic or an aerobic. Right,

492
00:25:30,240 --> 00:25:32,240
Speaker 1: are they consuming CO two? I'll have to ask a

493
00:25:32,320 --> 00:25:35,320
Speaker 1: microbiologist about that. Check in with my wife about it later.

494
00:25:35,359 --> 00:25:38,800
Speaker 1: I thank you, no one. Yeah, that's right, that's very convenient.

495
00:25:39,040 --> 00:25:41,200
Speaker 1: And so this has a really interesting history. It was

496
00:25:41,280 --> 00:25:44,520
Speaker 1: like in the forties that people figured out, oh maybe

497
00:25:44,560 --> 00:25:47,800
Speaker 1: this is possible. People were studying carbon fourteen just from

498
00:25:47,880 --> 00:25:50,080
Speaker 1: like a chemistry point of view, like what is this stuff?

499
00:25:50,320 --> 00:25:52,600
Speaker 1: How long does it last? And at the time, you know,

500
00:25:52,600 --> 00:25:55,400
Speaker 1: we didn't really understand the nucleus very well. People were

501
00:25:55,440 --> 00:25:58,320
Speaker 1: making estimates for how long it might last, and the

502
00:25:58,359 --> 00:26:00,720
Speaker 1: measurements they made were really surprised, and they discovered, oh,

503
00:26:00,720 --> 00:26:03,399
Speaker 1: my gosh, this stuff lasts a lot longer than we thought.

504
00:26:03,600 --> 00:26:06,520
Speaker 1: They expected to have a much shorter half life, like

505
00:26:06,800 --> 00:26:09,720
Speaker 1: tens or hundreds of years, so when they discovered that

506
00:26:09,760 --> 00:26:12,639
Speaker 1: it has a half life of almost six thousand years,

507
00:26:12,800 --> 00:26:16,160
Speaker 1: they were surprised. But it also opened up this really

508
00:26:16,160 --> 00:26:19,800
Speaker 1: cool possibility. Why were they surprised, Like, did we expect

509
00:26:20,400 --> 00:26:24,040
Speaker 1: that half lives would be like similar between objects on

510
00:26:24,080 --> 00:26:27,960
Speaker 1: the periodic table and they ended up not being similar. Yes,

511
00:26:28,000 --> 00:26:30,680
Speaker 1: there are reason they were surprised, or just sometimes sizes surprising.

512
00:26:31,320 --> 00:26:34,159
Speaker 1: They were surprised because we just didn't understand the nucleus

513
00:26:34,200 --> 00:26:36,280
Speaker 1: of the atom very well. I mean, this is the forties, right,

514
00:26:36,359 --> 00:26:38,760
Speaker 1: Quantum mechanics were very very new, and so all of

515
00:26:38,800 --> 00:26:41,320
Speaker 1: our calculations of how things work in the nucleus were

516
00:26:41,400 --> 00:26:43,680
Speaker 1: very very rough and a lot of handwaving. I mean

517
00:26:43,760 --> 00:26:47,680
Speaker 1: even today, it's not easy to do these calculations to say,

518
00:26:47,720 --> 00:26:49,480
Speaker 1: like what would be the mass of this particle or

519
00:26:49,520 --> 00:26:51,959
Speaker 1: how stable would that be. You know, we have theories

520
00:26:52,040 --> 00:26:54,959
Speaker 1: about whether the super heavy elements would be stable, but

521
00:26:55,040 --> 00:26:57,160
Speaker 1: we can't say these things for certain because we don't

522
00:26:57,160 --> 00:27:00,240
Speaker 1: know how to do a lot of these calculations. Because

523
00:27:00,280 --> 00:27:03,879
Speaker 1: the strong nuclear force is very complicated. It's very very strong,

524
00:27:03,880 --> 00:27:06,560
Speaker 1: which means the calculations are very very sensitive to getting

525
00:27:06,560 --> 00:27:08,639
Speaker 1: things wrong. It's a kind of calculation where if you

526
00:27:08,680 --> 00:27:10,720
Speaker 1: start to get things a little bit wrong, the wrongness

527
00:27:10,800 --> 00:27:13,520
Speaker 1: gets amplified by the strength of the force instead of

528
00:27:13,560 --> 00:27:16,440
Speaker 1: like a decaying away. Like with gravity, if you get

529
00:27:16,440 --> 00:27:18,960
Speaker 1: the location of an asteroid a little bit wrong, it's

530
00:27:18,960 --> 00:27:21,560
Speaker 1: not going to propagate to becoming really really wrong later

531
00:27:21,640 --> 00:27:23,560
Speaker 1: on because gravity is so weak, so you can make

532
00:27:23,600 --> 00:27:26,000
Speaker 1: approximations and mostly get the right answer at least for

533
00:27:26,040 --> 00:27:28,760
Speaker 1: the foreseeable future. With the strong force, as soon as

534
00:27:28,800 --> 00:27:31,320
Speaker 1: you get something a little bit wrong, everything goes totally wrong.

535
00:27:31,400 --> 00:27:34,640
Speaker 1: So the short version is that nuclear physics is hard. Well,

536
00:27:34,640 --> 00:27:37,040
Speaker 1: that's not surprising, and so maybe they shouldn't have been

537
00:27:37,080 --> 00:27:41,000
Speaker 1: surprised because nuclear physics is hard. Okay. So you had

538
00:27:41,040 --> 00:27:43,240
Speaker 1: mentioned at the top of the show that sewage was

539
00:27:43,280 --> 00:27:45,320
Speaker 1: gonna come into the story at some point, and so

540
00:27:45,359 --> 00:27:47,480
Speaker 1: I'm hoping that now that we're talking about, you know,

541
00:27:47,720 --> 00:27:50,320
Speaker 1: when we figure out the whole carbon fourteen thing, is

542
00:27:50,320 --> 00:27:52,119
Speaker 1: this when we get to talk about the sewage. This

543
00:27:52,200 --> 00:27:54,800
Speaker 1: is when we get to talk about the sewage. Absolutely yea.

544
00:27:55,320 --> 00:27:58,760
Speaker 1: So it was in mid nineteen forties and Willard Libby,

545
00:27:59,080 --> 00:28:02,040
Speaker 1: who was at Berkeley, learned about these results that carbon

546
00:28:02,119 --> 00:28:05,600
Speaker 1: fourteen was surprisingly long lasting, and he thought, hey, that

547
00:28:05,640 --> 00:28:07,920
Speaker 1: would be a really cool way to figure out how

548
00:28:07,960 --> 00:28:10,640
Speaker 1: long something has been dead. And so what he did

549
00:28:11,080 --> 00:28:12,719
Speaker 1: is he moved to a new job at the University

550
00:28:12,720 --> 00:28:15,719
Speaker 1: of Chicago and he proposed this idea. He said, oh,

551
00:28:15,800 --> 00:28:18,280
Speaker 1: maybe this will work. And the first thing they did

552
00:28:18,440 --> 00:28:22,840
Speaker 1: was to study methane from the Boston sewage system. Right,

553
00:28:22,840 --> 00:28:25,840
Speaker 1: So methane is a gas, right, that's produced when sewage

554
00:28:25,840 --> 00:28:29,320
Speaker 1: basically ferments. Right, my grooves are consuming your sewage. And

555
00:28:29,320 --> 00:28:31,880
Speaker 1: so they gathered this and they measured the carbon fourteen

556
00:28:31,920 --> 00:28:35,960
Speaker 1: fraction in methane basically from Boston's dark matter, and then

557
00:28:36,000 --> 00:28:40,120
Speaker 1: they compared that to how much carbon fourteen there was

558
00:28:40,200 --> 00:28:43,080
Speaker 1: in methane from fossil fuels, right, Like the methane that

559
00:28:43,160 --> 00:28:45,720
Speaker 1: maybe you burn in your house comes from plants that

560
00:28:45,840 --> 00:28:49,000
Speaker 1: died millions and millions and millions of years ago. And

561
00:28:49,080 --> 00:28:51,240
Speaker 1: what they found is no surprise to us now, is

562
00:28:51,280 --> 00:28:53,840
Speaker 1: that the methane from the Boston sewis system has a

563
00:28:53,840 --> 00:28:56,560
Speaker 1: lot of carbon fourteen and the methane from fossil fuels

564
00:28:56,640 --> 00:28:59,760
Speaker 1: has none. All Right, So that's beginning to tell us

565
00:28:59,760 --> 00:29:02,640
Speaker 1: the limits for how we can use carbon fourteen for dating.

566
00:29:02,720 --> 00:29:06,400
Speaker 1: But I'll know you said that Libby had moved to Chicago,

567
00:29:07,040 --> 00:29:10,040
Speaker 1: but he looked at the Boston sewage is there, just like,

568
00:29:10,200 --> 00:29:12,880
Speaker 1: is Boston sewage the best sewage? Why did you travel

569
00:29:12,920 --> 00:29:16,200
Speaker 1: all the way to Boston? Was the Chicago sewage wasn't

570
00:29:16,240 --> 00:29:19,959
Speaker 1: disgusting enough. I'm sure those people who live in Boston

571
00:29:20,000 --> 00:29:22,360
Speaker 1: are very proud of their sewage. I have a little

572
00:29:22,400 --> 00:29:24,760
Speaker 1: glimpse into this because of my wife's research. You know,

573
00:29:24,880 --> 00:29:27,320
Speaker 1: she studies the microbes and sewage, and it can be

574
00:29:27,360 --> 00:29:30,240
Speaker 1: surprisingly tricky to get access to it. So I suspect

575
00:29:30,320 --> 00:29:33,120
Speaker 1: it's just a question of like politics and access. Not

576
00:29:33,160 --> 00:29:36,480
Speaker 1: every waste management system is interested in having scientists like

577
00:29:36,600 --> 00:29:40,320
Speaker 1: dig around in their facility, while others are you free

578
00:29:40,360 --> 00:29:43,840
Speaker 1: to share the science gold that is flowing through their pipes?

579
00:29:47,040 --> 00:29:49,480
Speaker 1: Politics and sewage? Yeah, so I suspect they had a

580
00:29:49,520 --> 00:29:52,760
Speaker 1: good Boston connect, you know, for some real primo Boston

581
00:29:52,880 --> 00:29:56,560
Speaker 1: sewage got it okay. So so by the time you

582
00:29:56,640 --> 00:30:00,800
Speaker 1: ask petroleum, there's no carbon fourteen and you start losing

583
00:30:00,800 --> 00:30:03,880
Speaker 1: carbon fourteen when you die. So can you use this for?

584
00:30:04,440 --> 00:30:06,760
Speaker 1: Is this helpful for like certain kinds of fossils? What

585
00:30:06,840 --> 00:30:08,600
Speaker 1: kind of things that we use this for? So far,

586
00:30:08,840 --> 00:30:11,320
Speaker 1: you can use this for basically anything that's died in

587
00:30:11,360 --> 00:30:15,280
Speaker 1: the last maybe fifty thousand years, because those things were

588
00:30:15,320 --> 00:30:18,840
Speaker 1: accumulating carbon fourteen as they were alive and participating in

589
00:30:18,840 --> 00:30:21,560
Speaker 1: the biosphere, and as soon as they died, then they

590
00:30:21,560 --> 00:30:25,360
Speaker 1: stopped and the carbon fourteen started to decay away. Now,

591
00:30:25,400 --> 00:30:27,560
Speaker 1: things that are much much older than that, they just

592
00:30:27,600 --> 00:30:30,440
Speaker 1: have zero carbon fourteen. So you can't tell is this

593
00:30:30,480 --> 00:30:32,880
Speaker 1: thing one hundred thousand years old or one hundred million

594
00:30:32,960 --> 00:30:35,960
Speaker 1: years old or four billion years old, because you just

595
00:30:36,080 --> 00:30:38,520
Speaker 1: get zero. So what you got to do is measure

596
00:30:38,840 --> 00:30:42,120
Speaker 1: the carbon fourteen to carbon twelve ratio in your thing,

597
00:30:42,280 --> 00:30:45,080
Speaker 1: and then you can extrapolate back to when did this

598
00:30:45,120 --> 00:30:48,880
Speaker 1: thing last have the sort of normal rate of carbon fourteen?

599
00:30:49,240 --> 00:30:52,760
Speaker 1: Got it all right, So dinosaurs are out, but helpful

600
00:30:52,840 --> 00:30:58,320
Speaker 1: for things like human archaeology questions exactly. Human archaeology was

601
00:30:58,360 --> 00:31:02,400
Speaker 1: really like revolutionized this subject. The first time that they

602
00:31:02,560 --> 00:31:05,800
Speaker 1: used it was actually to date some Egyptian tombs. These

603
00:31:05,840 --> 00:31:08,400
Speaker 1: are some things that archaeologically we already knew what the

604
00:31:08,480 --> 00:31:12,480
Speaker 1: dates were based on writing and other analysis, Like archaeologists

605
00:31:12,520 --> 00:31:15,480
Speaker 1: already knew when somebody had been buried, and now they

606
00:31:15,480 --> 00:31:18,280
Speaker 1: were able to take a sample and measure the carbon

607
00:31:18,360 --> 00:31:20,920
Speaker 1: fourteen fraction in like a piece of linen or in

608
00:31:20,960 --> 00:31:25,160
Speaker 1: a piece of wood from the tomb and independently establish

609
00:31:25,400 --> 00:31:28,520
Speaker 1: the date of the death of that object, like here's

610
00:31:28,520 --> 00:31:31,920
Speaker 1: when the tree that formed this plank must have been killed,

611
00:31:32,280 --> 00:31:35,560
Speaker 1: or here's when this plant was harvested to make this linen.

612
00:31:35,880 --> 00:31:39,360
Speaker 1: And that's really powerful. It's like a completely separate clock

613
00:31:39,400 --> 00:31:43,320
Speaker 1: that lines up archaeologically with your records. Okay, So one,

614
00:31:43,360 --> 00:31:45,800
Speaker 1: that's awesome, and two I bet this has been used

615
00:31:45,840 --> 00:31:48,960
Speaker 1: at some point in ways that have made people angry,

616
00:31:48,960 --> 00:31:50,640
Speaker 1: like people who thought they had a thing that was

617
00:31:50,680 --> 00:31:52,600
Speaker 1: old but it ended up not being that old, or

618
00:31:52,680 --> 00:31:56,040
Speaker 1: the other way around. But before I ask you about that,

619
00:31:56,680 --> 00:32:12,960
Speaker 1: let's take another quick break. All right, So has this

620
00:32:13,040 --> 00:32:16,320
Speaker 1: method been used in a way that ended up making

621
00:32:16,320 --> 00:32:21,000
Speaker 1: people like why do I feel like you're digging for

622
00:32:21,000 --> 00:32:24,120
Speaker 1: the controversy here? Keey? Well, you know it makes good radio.

623
00:32:25,440 --> 00:32:28,600
Speaker 1: It does absolutely. Yeah, this is a really cool technique

624
00:32:28,640 --> 00:32:30,720
Speaker 1: and it's powerful because they can date things to like

625
00:32:30,840 --> 00:32:33,479
Speaker 1: within a few decades. You know. The thing is that

626
00:32:33,520 --> 00:32:36,440
Speaker 1: there's a lot of carbon in living stuff, and the

627
00:32:36,520 --> 00:32:39,320
Speaker 1: more carbon you have, the more preciser measurement can be.

628
00:32:39,600 --> 00:32:41,560
Speaker 1: So you can like pin down to within a few

629
00:32:41,560 --> 00:32:45,040
Speaker 1: decades when something died, and for example, when people discovered,

630
00:32:45,080 --> 00:32:48,800
Speaker 1: like the Dead Sea Scrolls, these ancient scrolls outside of

631
00:32:48,880 --> 00:32:51,160
Speaker 1: Jerusalem that have been in the desert for who knows

632
00:32:51,200 --> 00:32:52,920
Speaker 1: how long, and what may have been one of the

633
00:32:52,960 --> 00:32:56,160
Speaker 1: earliest written records of you know, the books of the Bible.

634
00:32:56,320 --> 00:32:59,080
Speaker 1: People wanted to know like, are these real? Are they

635
00:32:59,160 --> 00:33:01,440
Speaker 1: actually thousands of years old? Or is this like a

636
00:33:01,480 --> 00:33:05,440
Speaker 1: forgery from last week that's been stained with tea? And

637
00:33:06,280 --> 00:33:09,120
Speaker 1: so they were able to use radiocarbon dating to confirm

638
00:33:09,200 --> 00:33:12,560
Speaker 1: that these things were one thousand, nine hundred and seventeen

639
00:33:12,640 --> 00:33:15,160
Speaker 1: years old, which really told people like, these are an

640
00:33:15,200 --> 00:33:18,000
Speaker 1: ancient relic. You know, these are not created recently, or

641
00:33:18,000 --> 00:33:21,240
Speaker 1: at least the materials on which they were made are

642
00:33:21,360 --> 00:33:24,440
Speaker 1: fairly old. So either it's a really old book or

643
00:33:24,480 --> 00:33:27,320
Speaker 1: it's new writing on a really old sheet of paper. Well,

644
00:33:27,560 --> 00:33:29,760
Speaker 1: I'm gonna have to give you that. That's awesome. That's

645
00:33:29,800 --> 00:33:32,680
Speaker 1: not what I asked. I asked you for controversy that

646
00:33:32,840 --> 00:33:35,920
Speaker 1: you gave me confirmation. But still all right, so that's

647
00:33:35,920 --> 00:33:39,000
Speaker 1: pretty awesome. Well this controversy. Also, you may have heard

648
00:33:39,040 --> 00:33:41,640
Speaker 1: about the Shroud of Turin. This is this piece of

649
00:33:41,680 --> 00:33:44,720
Speaker 1: cloth that I think is held in Milan. That's supposed

650
00:33:44,720 --> 00:33:47,320
Speaker 1: to have like the face of Jesus on it, and

651
00:33:47,400 --> 00:33:50,520
Speaker 1: the mythology around it is that it wrapped to Jesus's

652
00:33:50,560 --> 00:33:53,360
Speaker 1: corpse and was sort of imprinted by the power of

653
00:33:53,440 --> 00:33:57,400
Speaker 1: his un don't know, spiritual personality with his face. And

654
00:33:57,480 --> 00:34:00,520
Speaker 1: so this is a relic that's been celebrated in people

655
00:34:00,560 --> 00:34:03,280
Speaker 1: like pilgrimage to go and see it, and so they

656
00:34:03,400 --> 00:34:06,440
Speaker 1: radiocarbon dated it and discovered Oops, it's actually from the

657
00:34:06,520 --> 00:34:09,919
Speaker 1: fourteenth century, which means it's pretty old. It's like six

658
00:34:10,040 --> 00:34:13,680
Speaker 1: hundred years old. But the plants that made this shroud

659
00:34:14,160 --> 00:34:18,080
Speaker 1: were grown and planted like fourteen hundred years after Jesus died.

660
00:34:18,440 --> 00:34:22,520
Speaker 1: That's disappointing. Is it safe to assume that there are

661
00:34:22,560 --> 00:34:26,880
Speaker 1: people who don't buy the science on this to this day? Oh? Absolutely,

662
00:34:26,920 --> 00:34:29,640
Speaker 1: the way people deny evolution or that the Earth is

663
00:34:29,719 --> 00:34:33,719
Speaker 1: round or the dinosaurs existed well before humans. There are

664
00:34:33,760 --> 00:34:36,880
Speaker 1: people who say radiocarbon dating is not reliable and that

665
00:34:36,960 --> 00:34:39,759
Speaker 1: you can't use it, especially, you know, when it contradicts

666
00:34:39,760 --> 00:34:42,200
Speaker 1: their belief. The thing I love about the Shroud of

667
00:34:42,360 --> 00:34:45,360
Speaker 1: Tern story is not just that it reveals that the

668
00:34:45,360 --> 00:34:47,880
Speaker 1: whole thing is a hoax, but it's an ancient hoax.

669
00:34:48,160 --> 00:34:51,640
Speaker 1: The hoax is now hundreds of years old, right, the

670
00:34:51,680 --> 00:34:56,000
Speaker 1: hoax itself is of historical interest. That's how old it is. Right,

671
00:34:56,640 --> 00:34:59,000
Speaker 1: A six hundred year old hoax is pretty cool. Okay,

672
00:34:59,040 --> 00:35:01,560
Speaker 1: it's not the face of g but wow, that's really

673
00:35:01,560 --> 00:35:03,680
Speaker 1: cool insight and like what people were doing and why

674
00:35:03,719 --> 00:35:05,480
Speaker 1: they wanted to do it and all sorts of stuff.

675
00:35:05,520 --> 00:35:08,720
Speaker 1: I love how like today's mundanity, right, and even lies

676
00:35:08,880 --> 00:35:13,400
Speaker 1: can turn into something fascinating for future anthropologists. Yeah, know,

677
00:35:13,520 --> 00:35:16,480
Speaker 1: humans have enjoyed messing with each other for a really

678
00:35:16,520 --> 00:35:19,319
Speaker 1: long time. It's good to know that. But it is

679
00:35:19,400 --> 00:35:22,240
Speaker 1: tricky to date things with carbon fourteen because it turns

680
00:35:22,239 --> 00:35:24,719
Speaker 1: out that the assumption we made at the beginning that

681
00:35:24,800 --> 00:35:27,680
Speaker 1: like carbon fourteen is produced in the upper atmosphere and

682
00:35:27,800 --> 00:35:32,360
Speaker 1: spreads around mostly evenly to everything, it's not exactly true,

683
00:35:32,960 --> 00:35:35,160
Speaker 1: and so you got to like make some corrections and

684
00:35:35,239 --> 00:35:38,600
Speaker 1: calibrations to get things as precise as you'd like. So, like,

685
00:35:38,840 --> 00:35:43,040
Speaker 1: how not exact are we talking here? Like you know

686
00:35:43,600 --> 00:35:45,600
Speaker 1: the flies that you find in bodies? I think things

687
00:35:45,600 --> 00:35:49,200
Speaker 1: like temperature impact development time. How many things impact our

688
00:35:49,239 --> 00:35:52,359
Speaker 1: ability to date things based on carbon fourteen? And are

689
00:35:52,360 --> 00:35:54,600
Speaker 1: they things that we can learn about and control for

690
00:35:55,440 --> 00:35:57,840
Speaker 1: or no, yes, absolutely we can learn about them. And

691
00:35:57,880 --> 00:36:00,640
Speaker 1: it's like a whole field of people calib rating carbon

692
00:36:00,680 --> 00:36:04,440
Speaker 1: fourteen dating. We first discovered this actually when carbon fourteen

693
00:36:04,520 --> 00:36:08,239
Speaker 1: dating got some Egyptian tombs wrong, like some of them

694
00:36:08,239 --> 00:36:11,040
Speaker 1: were bang on the archaeological records, and other ones that

695
00:36:11,200 --> 00:36:15,200
Speaker 1: archaeologists were pretty sure about. Radiocarbon dating got a little wrong,

696
00:36:15,200 --> 00:36:17,840
Speaker 1: and people thought, hmm, that's weird. I wonder what it means.

697
00:36:18,400 --> 00:36:21,440
Speaker 1: And so they discovered a few interesting effects. For example,

698
00:36:21,560 --> 00:36:25,279
Speaker 1: carbon fourteen production is not constant over time. If you

699
00:36:25,280 --> 00:36:27,880
Speaker 1: want to assume that you can extrapolate backwards from the

700
00:36:27,880 --> 00:36:31,960
Speaker 1: carbon fourteen ratio today to the carbon fourteen ratio when

701
00:36:31,960 --> 00:36:34,680
Speaker 1: this object died, you have to assume the carbon fourteen

702
00:36:34,760 --> 00:36:36,920
Speaker 1: is being replenished at the same rate over time. But

703
00:36:36,960 --> 00:36:40,440
Speaker 1: it turns out that it's not that there's a variation

704
00:36:40,640 --> 00:36:44,239
Speaker 1: in the carbon fourteen rates in the atmosphere. Whoa is

705
00:36:44,280 --> 00:36:47,759
Speaker 1: that because cosmic rays hit us at different rates? Is

706
00:36:47,800 --> 00:36:49,879
Speaker 1: this like a solar Now that's not a solar wind thing?

707
00:36:50,120 --> 00:36:54,080
Speaker 1: Do we know? Yeah? Why? I am confused. It's really

708
00:36:54,120 --> 00:36:57,000
Speaker 1: interesting and there's some cool physics there. One is that, yes,

709
00:36:57,080 --> 00:36:59,799
Speaker 1: cosmic rays have sort of like seasons that are not

710
00:37:00,080 --> 00:37:03,440
Speaker 1: holy constant. It's sort of like the solar weather. You know,

711
00:37:03,520 --> 00:37:06,680
Speaker 1: where these cosmic grays come from depend on like magnetic

712
00:37:06,719 --> 00:37:09,279
Speaker 1: fields and the galaxy. You know, what's going on with

713
00:37:09,360 --> 00:37:12,239
Speaker 1: the objects that are created them. So there's those kinds

714
00:37:12,239 --> 00:37:15,160
Speaker 1: of effects. But we can actually measure that in independent

715
00:37:15,239 --> 00:37:20,040
Speaker 1: ways because they can look at super ancient trees, right.

716
00:37:20,120 --> 00:37:23,960
Speaker 1: Trees are really cool because they grow and they add rings,

717
00:37:24,000 --> 00:37:26,880
Speaker 1: and those new rings interact with the biosphere, but the

718
00:37:26,960 --> 00:37:31,160
Speaker 1: old rings don't. So every year a tree is basically

719
00:37:31,200 --> 00:37:34,560
Speaker 1: like taking a sample of the carbon fourteen fraction in

720
00:37:34,600 --> 00:37:37,600
Speaker 1: the atmosphere and storing it forever. And so if you

721
00:37:37,680 --> 00:37:40,520
Speaker 1: slice open a really old tree and look back at

722
00:37:40,520 --> 00:37:43,160
Speaker 1: the carbon fourteen fraction in each of the rings, you

723
00:37:43,200 --> 00:37:46,120
Speaker 1: can get like a history of the carbon fourteen fraction

724
00:37:46,400 --> 00:37:48,560
Speaker 1: at the time that the tree was growing. Do you

725
00:37:48,640 --> 00:37:50,799
Speaker 1: not happen to know what the oldest tree we've done

726
00:37:50,840 --> 00:37:53,239
Speaker 1: that on is. Are we talking about like hundreds of

727
00:37:53,320 --> 00:37:55,799
Speaker 1: years worth of data? A thousands. We have lots that

728
00:37:55,800 --> 00:37:58,200
Speaker 1: are hundreds of years and a few that are thousands

729
00:37:58,200 --> 00:38:00,840
Speaker 1: of years, and so that really helped us calibrate like

730
00:38:00,880 --> 00:38:05,279
Speaker 1: the more recent fluctuations in carbon fourteen. But also humans

731
00:38:05,360 --> 00:38:08,960
Speaker 1: have really altered the carbon fourteen fraction in the atmosphere.

732
00:38:09,360 --> 00:38:12,200
Speaker 1: For example, we've been burning a lot of fossil fuels

733
00:38:12,200 --> 00:38:15,520
Speaker 1: over the last couple of hundred years. Fossil fuels have

734
00:38:15,719 --> 00:38:19,440
Speaker 1: carbon but no carbon fourteen, so we've been releasing a

735
00:38:19,480 --> 00:38:22,680
Speaker 1: lot of carbon twelve into the atmosphere, really bringing down

736
00:38:22,920 --> 00:38:26,400
Speaker 1: the carbon fourteen fraction in the atmosphere. So, like, human

737
00:38:26,440 --> 00:38:29,440
Speaker 1: effects have really changed this and made it more complicated

738
00:38:29,480 --> 00:38:31,759
Speaker 1: to interpret the past. Wow. So like if you were

739
00:38:32,239 --> 00:38:35,359
Speaker 1: an alien trying to age stuff that was happening down

740
00:38:35,400 --> 00:38:38,840
Speaker 1: here on Earth, and you wanted to age something you know,

741
00:38:38,960 --> 00:38:41,280
Speaker 1: thousands of years from now that happened during our period,

742
00:38:42,160 --> 00:38:44,600
Speaker 1: it would be a mess. It would be a mess

743
00:38:44,920 --> 00:38:47,840
Speaker 1: if you didn't have ways to calibrate it. And so fortunately,

744
00:38:47,880 --> 00:38:50,560
Speaker 1: like trees can help us understand these things. Because trees

745
00:38:50,560 --> 00:38:52,279
Speaker 1: have been around for hundreds of years since, we can

746
00:38:52,360 --> 00:38:55,360
Speaker 1: understand the effect the humans have had on the carbon

747
00:38:55,400 --> 00:38:59,239
Speaker 1: fourteen fraction in the atmosphere. But more confusingly, we've had

748
00:38:59,239 --> 00:39:03,040
Speaker 1: effects in both directions. So burning fossil fuels lowers the

749
00:39:03,080 --> 00:39:06,400
Speaker 1: carbon fourteen fraction because you're pumping out super old carbon

750
00:39:06,520 --> 00:39:09,440
Speaker 1: where everything has already decayed. But nuclear testing in the

751
00:39:09,520 --> 00:39:13,359
Speaker 1: atmosphere increases the carbon fourteen fraction because it makes new

752
00:39:13,400 --> 00:39:16,400
Speaker 1: carbon fourteen. Is all this radiation and all the products

753
00:39:16,400 --> 00:39:20,080
Speaker 1: of the nuclear testing makes lots and lots of carbon fourteen,

754
00:39:20,360 --> 00:39:22,960
Speaker 1: much more than it's made from cosmic rays. So like

755
00:39:23,080 --> 00:39:25,480
Speaker 1: in the middle of this century, we had like twice

756
00:39:25,520 --> 00:39:28,759
Speaker 1: as much carbon fourteen in the atmosphere as we usually do.

757
00:39:28,920 --> 00:39:33,880
Speaker 1: Where the worst that'll be another interesting problem for the

758
00:39:33,920 --> 00:39:36,560
Speaker 1: aliens to solve. Then where did all this carbon fourteen

759
00:39:36,640 --> 00:39:38,840
Speaker 1: come from? Oh, they were setting off nuclear weapons in

760
00:39:38,880 --> 00:39:42,839
Speaker 1: the sky, of course there were. It's fascinating because there's

761
00:39:42,840 --> 00:39:45,919
Speaker 1: two sides to that. Archaeologists are frustrated by that because

762
00:39:45,920 --> 00:39:48,920
Speaker 1: we're like poisoning the historical record and making it harder

763
00:39:48,960 --> 00:39:52,560
Speaker 1: to figure out when things came from. But geologists actually

764
00:39:52,560 --> 00:39:55,480
Speaker 1: really like it because it's like a really bright signal.

765
00:39:55,560 --> 00:39:57,840
Speaker 1: They're like, Okay, cool, we can use this to calibrate

766
00:39:57,880 --> 00:40:00,120
Speaker 1: and we can tell when something happened because the so

767
00:40:00,200 --> 00:40:03,120
Speaker 1: much carbon fourteen in that layer. So geologists, I think

768
00:40:03,120 --> 00:40:05,839
Speaker 1: would like us to be like regularly nuking the atmosphere

769
00:40:05,960 --> 00:40:09,759
Speaker 1: in predictable and periodic ways because it leaves like this

770
00:40:10,160 --> 00:40:12,680
Speaker 1: ruler back in the record. You know, I know a

771
00:40:12,719 --> 00:40:15,680
Speaker 1: geologist I think is not quite that self interested, but

772
00:40:16,280 --> 00:40:19,000
Speaker 1: I can imagine him thinking that that's a silver lining

773
00:40:19,080 --> 00:40:22,239
Speaker 1: of an awful thing. Humans are complicated. So yeah, so

774
00:40:22,280 --> 00:40:24,400
Speaker 1: you have to take all this into account, and you

775
00:40:24,440 --> 00:40:26,560
Speaker 1: have to know, like what was the rate of carbon

776
00:40:26,600 --> 00:40:29,520
Speaker 1: fourteen in the atmosphere over the last few thousand years.

777
00:40:29,520 --> 00:40:31,560
Speaker 1: And you also have to take into account where you

778
00:40:31,640 --> 00:40:34,200
Speaker 1: have found something. If you found it in the deep ocean,

779
00:40:34,239 --> 00:40:36,360
Speaker 1: then it was going to get less carbon fourteen to

780
00:40:36,480 --> 00:40:38,200
Speaker 1: begin with, and then if you found it in the

781
00:40:38,239 --> 00:40:42,440
Speaker 1: upper atmosphere. Also, the different hemispheres of Earth have different

782
00:40:42,480 --> 00:40:46,160
Speaker 1: depositions of carbon fourteen because there's different like patterns of winds,

783
00:40:46,520 --> 00:40:49,960
Speaker 1: and the North and the South hemisphere actually have totally separate,

784
00:40:50,080 --> 00:40:53,640
Speaker 1: independent wind systems that don't really mix very well. So

785
00:40:53,680 --> 00:40:56,920
Speaker 1: there's less carbon fourteen in the southern atmosphere because it's

786
00:40:56,960 --> 00:40:59,920
Speaker 1: like more surface area of ocean which sucks up more

787
00:41:00,040 --> 00:41:02,920
Speaker 1: carbon fourteen, and there's more carbon fourteen in the northern

788
00:41:02,960 --> 00:41:05,920
Speaker 1: hemisphere where this is less ocean surface. Do you have

789
00:41:06,040 --> 00:41:08,440
Speaker 1: any sense for like for the hemisphere thing, are we

790
00:41:08,480 --> 00:41:11,480
Speaker 1: talking like if you didn't correct for that, you'd be

791
00:41:11,560 --> 00:41:14,520
Speaker 1: off by about ten years or a thousand years, or

792
00:41:14,560 --> 00:41:15,880
Speaker 1: it just kind of depends on a lot of other

793
00:41:15,920 --> 00:41:18,920
Speaker 1: stuff too. These all are really small effects, and everybody

794
00:41:18,960 --> 00:41:21,360
Speaker 1: wants really precise dating of things, you know, down to

795
00:41:21,400 --> 00:41:23,480
Speaker 1: the decades, and so this is the kind of thing

796
00:41:23,520 --> 00:41:26,440
Speaker 1: that happens in science. First, you have a very approximate effect.

797
00:41:26,480 --> 00:41:28,960
Speaker 1: You're like, okay, let's just assume carbon fourteen is constant

798
00:41:29,000 --> 00:41:32,360
Speaker 1: everywhere and over time. What do we get? Oh my gosh,

799
00:41:32,400 --> 00:41:35,160
Speaker 1: it can teach us something already. Then you start to

800
00:41:35,200 --> 00:41:37,520
Speaker 1: hone in on the details you want, like the second

801
00:41:37,640 --> 00:41:39,719
Speaker 1: digit to be accurate, and then the third, and then

802
00:41:39,800 --> 00:41:42,400
Speaker 1: the fourth, and by now we're like, you know, seventy

803
00:41:42,480 --> 00:41:45,239
Speaker 1: years into this research project, we're getting down to the

804
00:41:45,320 --> 00:41:47,560
Speaker 1: nitty greedy details. So a lot of these things will

805
00:41:47,600 --> 00:41:51,759
Speaker 1: affect our estimate for the dates of things by decades

806
00:41:51,920 --> 00:41:54,959
Speaker 1: or maybe up to hundreds of years, not thousands of years.

807
00:41:54,960 --> 00:41:57,000
Speaker 1: It's not going to like up end everything we thought

808
00:41:57,040 --> 00:42:00,560
Speaker 1: we knew. We also need a really precise estimate of

809
00:42:00,600 --> 00:42:02,960
Speaker 1: the half life of carbon fourteen, right, we have to

810
00:42:03,080 --> 00:42:06,000
Speaker 1: be able to calibrate this clock to know how long

811
00:42:06,080 --> 00:42:09,200
Speaker 1: does it take carbon fourteen two decay? And as you said,

812
00:42:09,200 --> 00:42:11,600
Speaker 1: you can't wait around for five thousand years, which would

813
00:42:11,640 --> 00:42:13,920
Speaker 1: be the best way to get an accurate measurement. But

814
00:42:13,960 --> 00:42:16,600
Speaker 1: people have been developing more and more precise experiments with

815
00:42:16,680 --> 00:42:19,799
Speaker 1: like larger samples of carbon fourteen, So they actually had

816
00:42:19,800 --> 00:42:23,759
Speaker 1: to update the official half life of carbon fourteen from

817
00:42:23,760 --> 00:42:27,560
Speaker 1: fifty five sixty eight later to fifty seven thirty so

818
00:42:27,640 --> 00:42:29,680
Speaker 1: a change of like one hundred and fifty years. And

819
00:42:29,719 --> 00:42:32,960
Speaker 1: this is super fascinating because it then required a change

820
00:42:32,960 --> 00:42:36,239
Speaker 1: of all the archaeological dates. Like all the archaeologists who

821
00:42:36,320 --> 00:42:38,160
Speaker 1: thought that their thing was data to a certain date. Oops,

822
00:42:38,160 --> 00:42:41,120
Speaker 1: they got updated because the nuclear physicists or the chemists

823
00:42:41,320 --> 00:42:43,839
Speaker 1: got the number wrong. Does that mean that you get

824
00:42:43,920 --> 00:42:48,399
Speaker 1: to redo all of your publications with the updated date

825
00:42:48,440 --> 00:42:50,239
Speaker 1: and double the number of lines you have on your

826
00:42:50,239 --> 00:42:53,680
Speaker 1: CV because in that case, thank you physicists. It means

827
00:42:53,680 --> 00:42:55,600
Speaker 1: that there's a bunch of papers out there with old

828
00:42:55,680 --> 00:42:58,560
Speaker 1: dates that we now like no need corrections. You can't

829
00:42:58,600 --> 00:43:01,279
Speaker 1: just read the old pay in archaeology and take the

830
00:43:01,360 --> 00:43:03,400
Speaker 1: dates and face value. You have to know when that

831
00:43:03,520 --> 00:43:07,280
Speaker 1: date was calculated. Like what effects did they take into account?

832
00:43:07,560 --> 00:43:10,040
Speaker 1: And what effects do we now take into account? So

833
00:43:10,080 --> 00:43:13,600
Speaker 1: the whole thing has gotten really really complicated. That is frustrating,

834
00:43:13,760 --> 00:43:16,719
Speaker 1: but it also has been an enormous boon to archaeology.

835
00:43:17,080 --> 00:43:20,400
Speaker 1: I mean, what a powerful tool, Like anything that was alive,

836
00:43:20,719 --> 00:43:23,880
Speaker 1: now you can date the moment of its death. And

837
00:43:23,920 --> 00:43:25,960
Speaker 1: that's not a perfect tool, right, It still thinks like

838
00:43:26,040 --> 00:43:28,560
Speaker 1: when was this metal forged? Well, we can't tell because

839
00:43:28,560 --> 00:43:32,239
Speaker 1: it was never alive. It doesn't participate in the carbon biosphere,

840
00:43:32,360 --> 00:43:34,960
Speaker 1: So you can't date like jewelry, you know, or swords

841
00:43:35,040 --> 00:43:36,920
Speaker 1: or stuff like that, but you can look at what

842
00:43:37,040 --> 00:43:39,480
Speaker 1: else is in a grave and you can tell maybe

843
00:43:39,480 --> 00:43:43,480
Speaker 1: when that person died. And before this, archaeologists had much

844
00:43:43,520 --> 00:43:46,840
Speaker 1: more rudimentary methods. You know, they had this like layer

845
00:43:46,920 --> 00:43:49,640
Speaker 1: method where they would like count down from the ground

846
00:43:49,680 --> 00:43:52,760
Speaker 1: and try to like find things that they knew happened

847
00:43:52,760 --> 00:43:55,480
Speaker 1: that they could use to like sandwich when their relics

848
00:43:55,680 --> 00:43:58,359
Speaker 1: might have been buried. So it was very, very rough.

849
00:43:58,840 --> 00:44:01,800
Speaker 1: And now we have this whittle measure for these objects

850
00:44:01,840 --> 00:44:05,040
Speaker 1: when they died. It's super powerful. It's super powerful. But

851
00:44:05,080 --> 00:44:07,520
Speaker 1: I wonder if there was also a generation of scientists

852
00:44:07,560 --> 00:44:09,680
Speaker 1: who are like, you know, the whole reason I got

853
00:44:09,680 --> 00:44:12,000
Speaker 1: into archaeologies because I don't want to be in the lab,

854
00:44:12,520 --> 00:44:14,480
Speaker 1: and now I have to be in the lab to

855
00:44:14,520 --> 00:44:16,960
Speaker 1: get these dates. But on the other hand, I think

856
00:44:17,000 --> 00:44:21,080
Speaker 1: we all benefit when we get to more accurate, precise information. Yeah,

857
00:44:21,120 --> 00:44:24,600
Speaker 1: I think that's probably true. After this was discovered, very rapidly,

858
00:44:24,640 --> 00:44:26,760
Speaker 1: a bunch of labs were set up around the world

859
00:44:26,800 --> 00:44:29,480
Speaker 1: to start doing radiocarbon dating. So it's not the kind

860
00:44:29,520 --> 00:44:32,000
Speaker 1: of thing that like a typical archaeologist so does in

861
00:44:32,080 --> 00:44:36,240
Speaker 1: the field, or every archaeologist has their own radiocarbon setup.

862
00:44:36,400 --> 00:44:38,319
Speaker 1: It's a little bit of an involved process. What you

863
00:44:38,360 --> 00:44:41,040
Speaker 1: have to do is measure the carbon fourteen ratio. In

864
00:44:41,080 --> 00:44:42,480
Speaker 1: the old days, what they did was just sort of

865
00:44:42,480 --> 00:44:45,919
Speaker 1: like count the radiation emitted because it's emitting beta rays

866
00:44:46,280 --> 00:44:49,600
Speaker 1: when it's decaying. So that was the old strategy. More

867
00:44:49,640 --> 00:44:53,319
Speaker 1: recently they have a more precise strategy which uses mass spectrometer.

868
00:44:53,480 --> 00:44:56,400
Speaker 1: So it takes a sample of it, accelerates it bends

869
00:44:56,400 --> 00:44:58,960
Speaker 1: it through a magnetic field, and then it'll bend more

870
00:44:59,080 --> 00:45:01,160
Speaker 1: if it has low mass ass unless if it has

871
00:45:01,280 --> 00:45:03,880
Speaker 1: high mass. So it gives you like a spectrum of

872
00:45:03,920 --> 00:45:06,839
Speaker 1: the mass of the object that you're sampling, and you

873
00:45:06,840 --> 00:45:09,760
Speaker 1: can tell how much carbon fourteen, how much carbon twelve

874
00:45:09,840 --> 00:45:11,920
Speaker 1: is in there. You don't have to wait for the

875
00:45:11,960 --> 00:45:14,960
Speaker 1: carbon fourteen to decay, so you're getting to take advantage

876
00:45:14,960 --> 00:45:17,719
Speaker 1: of all the carbon fourteen in there, not just the

877
00:45:17,760 --> 00:45:20,319
Speaker 1: ones that happen to be decaying as you're watching. So

878
00:45:20,320 --> 00:45:23,120
Speaker 1: these are pretty specialized techniques now, and I think most

879
00:45:23,160 --> 00:45:26,520
Speaker 1: archaeologists like will send a sample to the lab rather

880
00:45:26,560 --> 00:45:28,560
Speaker 1: than like doing it themselves. So I think you still

881
00:45:28,600 --> 00:45:31,680
Speaker 1: have like old school Indiana Jones types out there in

882
00:45:31,680 --> 00:45:37,319
Speaker 1: the field, gathering stuff, plundering sites, civilization exactly. Oh man,

883
00:45:37,360 --> 00:45:40,520
Speaker 1: the ethics of archaeology not something I want to get into. Yeah,

884
00:45:40,640 --> 00:45:43,799
Speaker 1: nuralistic was science, Yeah, but then sending those samples to

885
00:45:43,840 --> 00:45:46,040
Speaker 1: a lab to do the dating. So you probably have

886
00:45:46,040 --> 00:45:49,640
Speaker 1: like a division. You know, you have the radiocarbon archaeologists

887
00:45:49,680 --> 00:45:51,160
Speaker 1: in the lab and the folks who are not in

888
00:45:51,200 --> 00:45:54,239
Speaker 1: the lab. Okay, well, let's step away from the ethical

889
00:45:54,320 --> 00:45:59,200
Speaker 1: quandaries presented to us by archaeology and talk about dinosaurs.

890
00:45:59,600 --> 00:46:03,680
Speaker 1: So sorry, So we've we've established, unfortunately early on, that

891
00:46:03,760 --> 00:46:06,640
Speaker 1: carbon fourteen is not help for dinosaurs. Is there something

892
00:46:06,680 --> 00:46:10,000
Speaker 1: we can use if we're interested in when a dinosaur bone,

893
00:46:10,600 --> 00:46:14,400
Speaker 1: you know, when the dinosaur died. Dinosaurs are tricky, absolutely,

894
00:46:14,440 --> 00:46:17,360
Speaker 1: because this clock has all run out. All carbon fourteen

895
00:46:17,400 --> 00:46:20,160
Speaker 1: that was in dinosaurs has now decayed. So what you

896
00:46:20,239 --> 00:46:24,280
Speaker 1: need are longer clocks. We did an episode about using

897
00:46:24,560 --> 00:46:28,640
Speaker 1: uranium to date stuff because there's this cool relationship between

898
00:46:28,760 --> 00:46:32,040
Speaker 1: uranium and lead. Uranium two thirty eight and uranium two

899
00:46:32,040 --> 00:46:35,280
Speaker 1: thirty five has half lives of more than a million years,

900
00:46:35,360 --> 00:46:38,720
Speaker 1: and so they're useful for dating stuff that's super duper old.

901
00:46:38,840 --> 00:46:41,480
Speaker 1: And when they form, this cool thing happens. They get

902
00:46:41,480 --> 00:46:45,600
Speaker 1: these zircon crystals zi r c N, And when those

903
00:46:45,640 --> 00:46:48,799
Speaker 1: zircon crystals form, they reject any lead and they like

904
00:46:48,920 --> 00:46:52,000
Speaker 1: expel lead from inside the crystal. So when they're formed,

905
00:46:52,160 --> 00:46:55,680
Speaker 1: they're like lead free, but they do take uranium in them,

906
00:46:56,040 --> 00:46:59,520
Speaker 1: and uranium decays into lead, so each one is like

907
00:46:59,560 --> 00:47:01,720
Speaker 1: a little hawk. Could you pick up a zircon crystal

908
00:47:01,920 --> 00:47:04,360
Speaker 1: and measure how much lead is inside of it, you

909
00:47:04,360 --> 00:47:07,360
Speaker 1: can tell when it was formed. So now we're dating

910
00:47:07,400 --> 00:47:11,279
Speaker 1: like when a rock cooled into these crystals, which is

911
00:47:11,320 --> 00:47:14,040
Speaker 1: pretty cool. That's awesome, And so then you measure in

912
00:47:14,040 --> 00:47:16,960
Speaker 1: the rock around the fossils or something. Yeah, exactly. Now,

913
00:47:17,120 --> 00:47:20,960
Speaker 1: dinosaur bones don't have this stuff in them, but sometimes

914
00:47:21,000 --> 00:47:24,759
Speaker 1: around the dinosaur bones there's like cooled magma, so this

915
00:47:25,000 --> 00:47:29,360
Speaker 1: igneous rock. Because fossils only form in sedimentary rock. But

916
00:47:29,400 --> 00:47:32,080
Speaker 1: if you have like layers of igneous rock above and

917
00:47:32,160 --> 00:47:35,279
Speaker 1: below your fossil, then you can use the zircon crystals

918
00:47:35,280 --> 00:47:38,480
Speaker 1: in those rocks to figure out when those crystals were

919
00:47:38,520 --> 00:47:41,400
Speaker 1: formed and therefore racket your dinosaur bones, so you can

920
00:47:41,480 --> 00:47:46,240
Speaker 1: tell roughly when it must have existed. Yea science. Science.

921
00:47:46,600 --> 00:47:48,479
Speaker 1: I was always puzzled as a kid when people would

922
00:47:48,480 --> 00:47:50,520
Speaker 1: talk about like the age of rocks. I'm like, what

923
00:47:50,600 --> 00:47:53,080
Speaker 1: does that mean? Like when is a rock born? Right,

924
00:47:53,120 --> 00:47:55,680
Speaker 1: it's not. Rock was never alive. And there's only later

925
00:47:55,719 --> 00:47:58,440
Speaker 1: that I understood that they're talking about when the rock cooled.

926
00:47:58,719 --> 00:48:01,080
Speaker 1: Because you have like that block of magma. It was

927
00:48:01,120 --> 00:48:03,680
Speaker 1: still basically rock. It was just like liquid rock. But

928
00:48:03,680 --> 00:48:06,280
Speaker 1: it's when it's cooled into a rock and formed crystal.

929
00:48:06,480 --> 00:48:09,160
Speaker 1: That's what they're interested in. That's what they're measuring. It's

930
00:48:09,160 --> 00:48:12,120
Speaker 1: like saying, how old is my ice cube? Well, you know,

931
00:48:12,160 --> 00:48:14,680
Speaker 1: the water in it has been water forever, but it's

932
00:48:14,719 --> 00:48:16,239
Speaker 1: only been an ice cube since you put it in

933
00:48:16,239 --> 00:48:19,000
Speaker 1: the freezer last Tuesday. So that's like the age of

934
00:48:19,040 --> 00:48:20,960
Speaker 1: your ice cube in the same way. It's a good

935
00:48:20,960 --> 00:48:23,040
Speaker 1: way to explain it. So yeah, that's the story of

936
00:48:23,120 --> 00:48:27,920
Speaker 1: radiocarbon dating, this incredible cool process where clocks are created

937
00:48:27,960 --> 00:48:30,560
Speaker 1: in the upper atmosphere and then drift down into the

938
00:48:30,600 --> 00:48:34,880
Speaker 1: biosphere inhaled by plants eaten by you and then stop

939
00:48:34,960 --> 00:48:37,920
Speaker 1: ticking and as soon as you stop eating and breathing.

940
00:48:38,080 --> 00:48:40,600
Speaker 1: Thanks very much Kelly for joining us on this trip

941
00:48:40,719 --> 00:48:44,000
Speaker 1: into debunking the Shroud of Turn and confirming the Dead

942
00:48:44,040 --> 00:48:46,680
Speaker 1: Sea scrolls. Thanks for bringing me along up the trip.

943
00:48:46,719 --> 00:48:49,800
Speaker 1: I had a great time, all right, and thanks everyone

944
00:48:49,840 --> 00:48:52,080
Speaker 1: for listening, And if you have questions about how something works,

945
00:48:52,120 --> 00:48:54,480
Speaker 1: please don't be shy, right to us to questions at

946
00:48:54,600 --> 00:49:02,680
Speaker 1: Dangel and Jorge dot com. Tune in next time. Bye,

947
00:49:06,400 --> 00:49:09,200
Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain

948
00:49:09,280 --> 00:49:13,160
Speaker 1: the Universe is a production of iHeartRadio or more podcast

949
00:49:13,320 --> 00:49:17,200
Speaker 1: from my heart Radio visit the iHeartRadio app, Apple Podcasts,

950
00:49:17,320 --> 00:49:19,680
Speaker 1: or wherever you listen to your favorite shows.