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Speaker 4: Hey Daniel, it's been a long time. Did you have

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Speaker 4: a nice holiday with your family?

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Speaker 1: We did, Thank you very much. We did some of

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Speaker 1: our favorite holiday traditions.

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Speaker 4: Ooh, like you cooked specific meals that you only cook

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Speaker 4: once a year or something like that.

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Speaker 1: Well, you know, one of our favorite holiday traditions is

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Speaker 1: a little bit unusual. It's trash Day.

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Speaker 4: Like when you roll your bins to the street because

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Speaker 4: I call that Tuesday. Does that count as a holiday? Peal?

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Speaker 5: No?

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Speaker 1: No, No. Trash Day is a much bigger deal. It's

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Speaker 1: when you take all the stuff out of your closets,

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Speaker 1: decide what you actually need, and donate or throw away

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Speaker 1: the rest of it.

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Speaker 4: Oh, I bet you find some real treasures.

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Speaker 1: You know, every year we try to go one layer

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Speaker 1: deeper into the archaeology of our closets.

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Speaker 4: Do you think you'll ever reach the back.

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

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Speaker 1: just be like an infinite stack of useless junk.

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Speaker 4: Well, maybe you'll get lucky and it will have compressed

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Speaker 4: for long enough that it will become diamonds or something.

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Speaker 1: Or there'll be a black hole in there that'll just

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Speaker 1: eat you.

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Speaker 4: That's not lucky, that's less lucky. That's still interesting.

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

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Speaker 1: a particle physicist, and I love throwing stuff away.

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Speaker 4: I'm Kelly Waiter Smith. I'm a parasitologist with Rice University,

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Speaker 4: and I love throwing stuff away. But my family doesn't know.

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Speaker 1: Do you guys have arguments about how many nostalgic elements

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Speaker 1: to keep.

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Speaker 4: Yes, that might be the thing we argue about the

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Speaker 4: most often.

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Speaker 1: Actually, 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 handy very rarely.

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Speaker 4: And also, you know, with things like Amazon, it could

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Speaker 4: show up at your house in less than a day.

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Speaker 4: So even if I'm wrong, you can just get a

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Speaker 4: new melon baller.

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

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Speaker 4: That's right, that's right. You can always just choose this

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Speaker 4: spoom right.

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Speaker 1: Well, I feel like you might appreciate the melon baller,

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Speaker 1: but you'll appreciate the lack of the melon baller even more.

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Speaker 1: You know, nothing is better than negative space if you've

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Speaker 1: succeeded in like cleaning out a closet or cleaning out

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Speaker 1: some corner of your room, and you can just appreciate

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Speaker 1: the emptiness.

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Speaker 4: I agree. I like not tripping over things in the

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Speaker 4: middle of the night because I get up a lot

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Speaker 4: in the middle of the night. I value that well.

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Speaker 1: Welcome to the podcast Daniel and Jorge explain the Universe,

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Speaker 1: in which we explore the meaning of nothingness and the

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Speaker 1: very fabric of space itself. We take the whole universe

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Speaker 1: apart from the junk in your closet it's to the

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

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

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

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

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

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Speaker 4: So what are we working on today? Then?

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Speaker 1: Today we are thinking about the universe as a sort

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Speaker 1: of mystery. I like to think of physicists as like

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Speaker 1: detectives trying to crack the murder mystery of the universe,

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Speaker 1: like what happened here? We are showing up at the

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Speaker 1: scene and wondering, like, how did it all get to

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Speaker 1: be the way that it is?

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Speaker 4: And today you get to be the forensic scientist that

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Speaker 4: dates the dead body.

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Speaker 1: That's always a good character, that's right, because when you

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Speaker 1: show up at the scene, you want to understand what happened.

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Speaker 1: You want to put things in order. You want to

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Speaker 1: say this happened, then that happened, then the other happened,

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Speaker 1: like the Solar System formed and then the Earth cooled,

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Speaker 1: and then life evolved on the planet, or the Big

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Speaker 1: Bang happened, and then heally informed and then much much

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Speaker 1: later stars happened. The whole point of doing science is

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Speaker 1: to put the universe in some sort of order. That's

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Speaker 1: what a store is. And I'm a firm believer in

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Speaker 1: the philosophy that human thinking is mostly about storytelling, and

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Speaker 1: so in order to do that, you have to figure

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Speaker 1: out like how old is stuff, what came before what

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Speaker 1: other stuff? You need to have dates and clocks and

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Speaker 1: times if you're going to unravel the murder mystery of

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Speaker 1: the universe.

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Speaker 4: And there's a lot of different ways that we've done

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Speaker 4: that throughout the years, and some of them work better

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Speaker 4: for particular kinds of mysteries than others. So what sort

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Speaker 4: of mysteries are we solving today?

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Speaker 1: Well, of course we are interested in the mysteries of

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Speaker 1: deep time. What happened in the first few moments of

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Speaker 1: the universe. How long has the Earth been around, and

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Speaker 1: what's been going on? How did everything come together? One

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Speaker 1: of my favorite things about dating stuff is discovering those surprises,

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Speaker 1: those realizations like wow, oh my gosh, the Earth is

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Speaker 1: so much older than anybody ever imagined, or that the

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Speaker 1: universe is shockingly old, or you know, for some people

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Speaker 1: the universe might be shockingly young. Maybe some people thought

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Speaker 1: the universe had been around forever or millions of years.

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Speaker 1: So anytime you get one of these dates, it's this

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Speaker 1: glorious moment where you get to like pin down the

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Speaker 1: universe and say, aha, now I know something about you,

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Speaker 1: and that like eliminates a bunch of possibilities. When you're

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Speaker 1: a reader digesting a mystery novel, you have like lots

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Speaker 1: of different options in your head. Maybe it was this person,

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Speaker 1: maybe it was that person, maybe it was this third person.

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Speaker 1: And as you get clues, you get to eliminate possibilities,

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Speaker 1: which finally reveals to you the truth, right, what actually

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Speaker 1: happened in the universe. The story is revealed by elimination,

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Speaker 1: and so those clues are absolutely essential. But you're right

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Speaker 1: tell you that there's lots of different ways to date

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Speaker 1: things in the universe, and today we're going to be

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Speaker 1: focusing on something a little bit more recent how we

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Speaker 1: can use physics to understand fairly recent history here on Earth.

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Speaker 4: Ooh, that sounds a lot less disgusting than using fly maggots.

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Speaker 1: Fly maggots, what are you talking about?

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Speaker 4: That's for dating things like you know, dead bodies that

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Speaker 4: you find, like what stage are the fly eggs that

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Speaker 4: have been laid on the body, So that that's you know,

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Speaker 4: we're working with like days to weeks there, So are

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Speaker 4: we working on that scale or are we working like

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Speaker 4: past the rotting dipter and phase?

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Speaker 1: Definitely past the rotting corpse phase. But I think you

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Speaker 1: put your finger on a really interesting point, which is

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Speaker 1: that there are all these clocks build into nature, right,

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Speaker 1: like maggots take a certain amount of time to digest

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

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Speaker 1: to cool, and these clocks are things we can take

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Speaker 1: advantage of in order to figure out how old things are,

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

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Speaker 1: or how long they've been radioactively decaying. We don't get

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

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Speaker 1: and like leave clocks in place to tell us how

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Speaker 1: long things took. Instead, we have to just take advantage

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Speaker 1: of the clocks that we find. And some of these clocks,

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Speaker 1: as you say, are really short lived, like they tell

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Speaker 1: us about things that happened just over weeks. Some of

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Speaker 1: them can tell us about things that happened for billions

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Speaker 1: of years, and other ones can tell us about things

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Speaker 1: that happened in the last ten fifty thousand years, which

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

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

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

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Speaker 4: I love learning about this topic because it's so exciting

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Speaker 4: to me how we figure out what tools are the

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Speaker 4: best ones to use to explore the past. And I

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Speaker 4: specifically like hearing about sort of physics and chemistry sorts

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Speaker 4: of tools because my sense is that they're a little

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Speaker 4: bit less susceptible to uncertainty. So, for example, you know,

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Speaker 4: temperature can impact how fast those flies are developing. But

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Speaker 4: maybe today you're going to explain to me that chemistry

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Speaker 4: and physics aren't that straightforward either.

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Speaker 1: It turns out to be a twisty and complicated topic,

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Speaker 1: and of course sewage is involved.

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Speaker 4: Yay.

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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?

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Speaker 4: Well, should we start by seeing what the listeners think?

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Speaker 1: Yes, absolutely, I was curious to hear what people people

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Speaker 1: had to say about this. Radiocarbon dating is something I

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Speaker 1: think a lot of people have heard about. It's on

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Speaker 1: television all the time, and we date this and we

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Speaker 1: date that. But I was wondering if people like really

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Speaker 1: understood the mechanism of it, like what the physics is

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Speaker 1: of these clocks? Why is there a clock? Why does

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Speaker 1: it start when you die? And how do we read

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Speaker 1: it out? So thanks very much to everyone who participates

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Speaker 1: in this segment of the podcast, sharing your thoughts without

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Speaker 1: a chance to prepare. If you would like to participate

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Speaker 1: in the future, please don't be shy. I'll be gentle.

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Speaker 1: It's fun. Just write to me two questions at Danielandhorge

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Speaker 1: dot com. So before you hear these answers, think to yourself,

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Speaker 1: do you know how radiocarbon dating works? Here's what people

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Speaker 1: had to say.

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Speaker 6: If we find some animal spoon, let's say some dinosaurs poon,

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Speaker 6: but it inside the earth, and then we calculate the

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Speaker 6: amount of carbon s forteen specifically present in it. Through

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Speaker 6: those calculations, we can easily calculate the age of that skeleton.

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Speaker 1: I've heard it get called carbon fourteen dating before, so

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

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Speaker 1: with the isotope and the decay of that carbon atom.

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Speaker 4: You can detect the age of organic objects by looking

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Speaker 4: at the ratio of carbon isotopes.

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Speaker 7: I feel like carbon dating is when like two particles

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Speaker 7: of carbon are like connected. I don't know, I don't

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Speaker 7: really know anything about that.

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Speaker 4: I felt like the answers to these fell into two camps,

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Speaker 4: people who sounded like they really knew what they were

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Speaker 4: talking about and people who had maybe not even heard

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Speaker 4: of carbon dating. And to me, that's sort of interesting

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Speaker 4: that it's like an either or scenario, Like maybe either

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Speaker 4: you're into the kinds of TV shows that this is

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Speaker 4: shown in, or maybe you're not watching NCIS Or what

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Speaker 4: was that shit bones where the archaeologist was doing carbon

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Speaker 4: fourteen dating? Yeah, what do you think?

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

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Speaker 1: like carbon and fourteen adams are like hooking up, you know,

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Speaker 1: they're like on Tinder, finding each other and making magic.

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Speaker 4: That was a clever off the cuff response.

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Speaker 1: There.

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Speaker 4: Yeah, I liked it.

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Speaker 1: Our listeners are funny, funny people, absolutely, and I had

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Speaker 1: 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'd 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.

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Speaker 4: How can listeners suggest topics to you? Just shoot you

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Speaker 4: an email.

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

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Speaker 1: write to me too. Questions at Danielandhorhe 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.

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Speaker 4: I'm with you. There are a few things I enjoy

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Speaker 4: more than an excuse to study a topic that's interesting

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Speaker 4: 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 slice off a few hours of your day and

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

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

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Speaker 1: having to do a podcast on it to explain it

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Speaker 1: of the folks. Is a good excuse to go and

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Speaker 1: actually learn how something works.

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Speaker 4: That is one of the weird things about academia. You

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Speaker 4: don't feel like you have a lot of time to

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Speaker 4: just sit and think. But I too, have created a

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Speaker 4: bunch of tricks in my life, you know, like, oh,

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Speaker 4: I'm gonna write a book about ten emerging technologies, so

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Speaker 4: I have to read about all of them. So yeah,

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Speaker 4: but at least we have these tricks, all right. So

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Speaker 4: what is carbon fourteen?

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Speaker 1: Right? So radio carbon dating or carbon fourteen dating uses

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Speaker 1: this weird form of carbon called carbon fourteen. And when

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Speaker 1: we say carbon fourteen, that number fourteen tells us how

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Speaker 1: many nucleons there are in the atom. So remember that

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Speaker 1: an atom has electrons around it, and in the nucleus

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Speaker 1: there are protons and neutrons. Now, usually carbon has six

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Speaker 1: protons and six neutrons, and so that's carbon twelve. That's

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Speaker 1: like the vanilla kind of carbon, the kind that makes

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Speaker 1: up most of you, and if it's in carbon dioxide

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Speaker 1: and everywhere in the atmosphere, So that's carbon twelve, which

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Speaker 1: is stable. Carbon fourteen is a weird version of carbon

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Speaker 1: it's still carbon, so there are six protons inside, but

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Speaker 1: there's two extra neutrons, so it's like a heavier nucleus.

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Speaker 1: So that's what carbon fourteen is.

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Speaker 4: And do those neutrons want to stay there or do

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Speaker 4: they want to escape?

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Speaker 1: So, you know, the stability of the nucleus is a

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Speaker 1: really interesting and complicated question. Some collections of protons and

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Speaker 1: neutrons are stable. You can like build carbon twelve and

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Speaker 1: have it sit in space and come back a billion

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Speaker 1: years later and it'll still be carbon twelve. Other constructions

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Speaker 1: are not stable, Like you add two more neutrons and

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Speaker 1: all of a sudden you have carbon fourteen. It's not stable.

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Speaker 1: It will fall apart after a few thousand years. And

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Speaker 1: this all comes down to how those protons and neutrons

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Speaker 1: like to put themselves together inside the nucleus. Remember that

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

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

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Speaker 1: so initially you might wonder, well, how does the nucleus

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Speaker 1: stay together anyway? It's all positive charges, why don't they

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Speaker 1: just blow each other apart? And there is that desire, right,

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Speaker 1: They definitely are pushing against each other. But on the

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Speaker 1: other hand, they're held together by a much stronger force.

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Speaker 1: The strong nuclear force sticks the protons and the neutrons

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Speaker 1: all together. So it's a delicate balance in some cases

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Speaker 1: between the strong force sticking it together and the electromagnetic

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Speaker 1: force trying to push it apart.

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Speaker 4: You have one prouton and one neutron held together by

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Speaker 4: the strong nuclear force. That's stable. And then when you've

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Speaker 4: got extra neutrons floating around so that they don't pair evenly,

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Speaker 4: is that what makes it unstable?

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Speaker 1: Yeah, that's right. You can actually think about the construction

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Speaker 1: of the nucleus in a similar way to how we

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Speaker 1: think about electron orbitals. You remember learning in like high

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Speaker 1: school chemistry that electrons aren't all just buzzing around the

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Speaker 1: nucleus the same way. It's like one in the lowest

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Speaker 1: energy level and another one in the next energy level,

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Speaker 1: and they sort of fill up and they get to

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Speaker 1: like more and more elaborate orbitals as they get to

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Speaker 1: higher and higher energy. Well, the nucleus is constructed sort

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Speaker 1: of in the same way. The picture you often have

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Speaker 1: of the nucleus is just like a scoop full of

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Speaker 1: protons and neutrons, but that's not really very accurate. It's

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Speaker 1: more like there are shells. You're like an inner core

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Speaker 1: where protons and neutrons have clicked together, and then you

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Speaker 1: can surround that with another layer of like protons and neutrons,

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Speaker 1: and the most stable atoms are the ones where those

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Speaker 1: layers are filled. You've like clicked in all the protons

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Speaker 1: and neutrons. It's sort of like making a roman arch.

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Speaker 1: When you have all the bricks together, they click together

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Speaker 1: to make a very stable structure. If you're just missing one,

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Speaker 1: then it can be very unstable.

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Speaker 4: So I didn't do great in high school chemistry. Is

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Speaker 4: the reason that that sounds new to me because we've

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Speaker 4: learned this in the twenty plus years since I've been

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Speaker 4: in high school. Or is that something we usually just

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Speaker 4: sort of, you know, skip over in high school or

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Speaker 4: what's the story there? How long have we known that?

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

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Speaker 1: school chemistry teacher to really find the answer to that.

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Speaker 1: Let's dig deep into your past. In fact, we have

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Speaker 1: them here on the podcast Surprise Surprise Your Life.

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Speaker 4: I don't think they like to be very much.

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Speaker 1: Let's move on. No, my high school chemistry teacher would

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Speaker 1: not be happy to hear from me either. I think

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

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

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

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

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

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Speaker 1: and heavier nuclei to understand, like what are the limits

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Speaker 1: of stability? How many protons and neutrons can you stick

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Speaker 1: together and have something which will stick around for billions

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Speaker 1: of years. We have a whole podcast episode about what

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Speaker 1: are the heaviest stable atoms and we think, for example,

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Speaker 1: there might be an island of stability where you get

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Speaker 1: like hundreds of protons and neutrons stuck together to make

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Speaker 1: new super heavy stable elements nobody's ever seen before. So

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Speaker 1: it's a complex field of study, and it's probably not

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

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Speaker 1: because it's messy, and I don't think that high school

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Speaker 1: sophomores aren't necessarily ready for it.

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Speaker 4: I'm not sure that I was ready for the electron

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Speaker 4: stuff either, but all right, so these things aren't stable,

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Speaker 4: and every once in a while the neutrons get kicked out.

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Speaker 4: How long are we talking before the neutrons get get

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Speaker 4: kicked out? Does it take like weeks, years, millennia? What

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Speaker 4: are we looking at?

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Speaker 1: So every atom is different. Uranium, for example, has a

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Speaker 1: half life which is like the age of the Earth,

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Speaker 1: but carbon fourteen only lasts about fifty seven hundred years. Now,

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Speaker 1: remember when we say that, we don't mean that there's

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Speaker 1: like a little clock inside every carbon and when the

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Speaker 1: time expires, it dies. What we mean is that that's

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Speaker 1: how long it takes, like a population of carbon atoms

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Speaker 1: for half of them to decay. Each individual one might

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Speaker 1: take longer or less time, because fundamentally it's a quantum

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Speaker 1: mechanical effect. There's a randomness to when these things decay.

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Speaker 4: So like thousand, seven hundred years, that's much longer than

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Speaker 4: any of us live. And so certainly there was no

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Speaker 4: scientist who was sitting around, you know, watching these things

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Speaker 4: for five thousand, seven hundred years. How do we figure

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Speaker 4: something like that out?

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Speaker 1: That's a great question. And you know, if it did

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Speaker 1: take fifty seven hundred years for every carbon atom to decay,

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Speaker 1: then you couldn't measure that half life without waiting for

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Speaker 1: the first one to decay would literally take thousands of years.

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

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

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

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Speaker 4: And you wouldn't get tenure.

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Speaker 1: You need a very understanding department chair area that's right.

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Speaker 1: And so it's the statistical nature of that, the randomness

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Speaker 1: that really helps you, because even though the half life

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Speaker 1: is five thousand, seven hundred years, after one hundred years,

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Speaker 1: there is a chance that a few of them will

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Speaker 1: have decayed. So all you need is like a lot

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Speaker 1: of carbon atoms, millions and billions and zillions. Unfortunately, there

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Speaker 1: are a lot of them around, and you just watch

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Speaker 1: for a few years or even a few months, and

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Speaker 1: a few of them will decay, and from that you

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Speaker 1: can extrapolate, right as soon as you start to see

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Speaker 1: some of them decay, you know how likely it is

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Speaker 1: for any of them to decay, and from that you

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Speaker 1: can calculate how long it would take for half of

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Speaker 1: them to decay.

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Speaker 4: As it decay, does it go from carbon fourteen, the

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Speaker 4: carbon thirteen, the carbon twelve, or does it go right

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Speaker 4: from fourteen to twelve does it lose two neutrons all

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Speaker 4: 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. It will stick around

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

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

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Speaker 1: state it can flip intwo is also a little potential well.

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Speaker 1: And like classically, if you had a particle trapped in

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Speaker 1: a little well, it could never get out. So what

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Speaker 1: happens is that this atom switches from one state to

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

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Speaker 1: between it. It does this by quantum tunneling. It's like

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Speaker 1: an electron stuck in one little hole that ends up

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Speaker 1: in another little hole, even though it doesn't have the

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

439
00:21:21,280 --> 00:21:25,920
Speaker 1: into nitrogen fourteen through this random quantum mechanical tunneling process

440
00:21:26,160 --> 00:21:28,399
Speaker 1: that lets us switch from one state to a lower

441
00:21:28,520 --> 00:21:31,760
Speaker 1: energy state without having enough energy to actually go over

442
00:21:31,800 --> 00:21:33,080
Speaker 1: the barrier in between them.

443
00:21:33,280 --> 00:21:35,600
Speaker 4: That's another thing I'm amazed we ever managed to figure out.

444
00:21:36,480 --> 00:21:39,160
Speaker 1: I know, so like quantum mechanics is happening all over

445
00:21:39,160 --> 00:21:41,560
Speaker 1: the place in the atmosphere right in front of us.

446
00:21:41,880 --> 00:21:44,960
Speaker 4: That's crazy. So where do we get carbon fourteen in

447
00:21:45,000 --> 00:21:45,639
Speaker 4: the first place?

448
00:21:45,960 --> 00:21:48,800
Speaker 1: Yeah, carbon fourteen only sticks around for a few thousand years.

449
00:21:48,840 --> 00:21:51,080
Speaker 1: So you might wonder, like the Earth is billions of

450
00:21:51,200 --> 00:21:53,840
Speaker 1: years old, why do we have any carbon fourteen? And

451
00:21:53,920 --> 00:21:55,879
Speaker 1: the only reason we do is that we have a

452
00:21:55,920 --> 00:21:58,800
Speaker 1: source of it, right this new carbon fourteen being made

453
00:21:59,240 --> 00:22:02,560
Speaker 1: all the time, and of course it comes from space.

454
00:22:03,359 --> 00:22:06,200
Speaker 1: The Earth is not just sitting out in empty space.

455
00:22:06,320 --> 00:22:09,800
Speaker 1: Space is very far from empty. We're being inundated with

456
00:22:09,960 --> 00:22:13,160
Speaker 1: high energy particles all the time from the Sun, from

457
00:22:13,200 --> 00:22:16,680
Speaker 1: the Black hole, accretion, disks from other galaxies. All sorts

458
00:22:16,680 --> 00:22:19,679
Speaker 1: of stuff are smashing into the Earth all the time.

459
00:22:19,960 --> 00:22:22,480
Speaker 1: And we call these things cosmic rays, and when they

460
00:22:22,560 --> 00:22:26,040
Speaker 1: hit the upper atmosphere, they cause all sorts of reactions.

461
00:22:26,119 --> 00:22:28,840
Speaker 1: They smash into stuff and they change it. What happens

462
00:22:29,000 --> 00:22:32,760
Speaker 1: is a cosmic ray will smash into like a proton

463
00:22:32,840 --> 00:22:35,840
Speaker 1: that's in nitrogen, which is seven P seven N, and

464
00:22:36,000 --> 00:22:39,400
Speaker 1: convert it into a neutron. So you have nitrogen fourteen,

465
00:22:39,880 --> 00:22:42,280
Speaker 1: smash bang with a proton, and you end up with

466
00:22:42,359 --> 00:22:46,040
Speaker 1: carbon fourteen because one of those protons has gotten converted

467
00:22:46,080 --> 00:22:46,960
Speaker 1: into a neutron.

468
00:22:47,160 --> 00:22:50,800
Speaker 4: WHOA Okay, And that's all happening in the atmosphere and

469
00:22:50,840 --> 00:22:52,680
Speaker 4: not happening much on Earth. Is that right?

470
00:22:52,720 --> 00:22:55,320
Speaker 1: That's right, it's happening mostly in the upper atmosphere. Cosmic

471
00:22:55,320 --> 00:22:58,600
Speaker 1: grays can't just fly through the atmosphere. They interact with particles.

472
00:22:58,680 --> 00:23:00,479
Speaker 1: It's sort of like running into a crack, right, You're

473
00:23:00,480 --> 00:23:03,480
Speaker 1: going to bang into all the other particles because cosmic areas,

474
00:23:03,480 --> 00:23:06,000
Speaker 1: they're just particles. They sound spooky and weird, but they're

475
00:23:06,040 --> 00:23:08,200
Speaker 1: just particles. So these things are created in the upper

476
00:23:08,280 --> 00:23:10,760
Speaker 1: atmosphere and then they sort of drift down to the

477
00:23:10,800 --> 00:23:11,640
Speaker 1: rest of the planet.

478
00:23:11,760 --> 00:23:13,360
Speaker 4: Okay, all right, so now we know how we get

479
00:23:13,400 --> 00:23:17,240
Speaker 4: carbon fourteen, and we should take a break, and when

480
00:23:17,240 --> 00:23:19,760
Speaker 4: we come back we'll talk about how it goes from

481
00:23:19,760 --> 00:23:24,760
Speaker 4: the atmosphere to being incorporated into living things.

482
00:23:26,640 --> 00:23:29,560
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533
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535
00:26:10,359 --> 00:26:14,720
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536
00:26:14,800 --> 00:26:16,920
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537
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538
00:26:20,280 --> 00:26:23,879
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539
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540
00:26:27,080 --> 00:26:30,720
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541
00:26:30,760 --> 00:26:34,000
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542
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543
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546
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547
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548
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549
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550
00:27:04,400 --> 00:27:09,280
Speaker 4: And we're back. Okay. So, carbon fourteen, made by cosmic

551
00:27:09,359 --> 00:27:13,480
Speaker 4: rays in the atmosphere, falls down towards the living stuff

552
00:27:13,520 --> 00:27:16,080
Speaker 4: that lives below, and then what happens, Daniel.

553
00:27:16,240 --> 00:27:19,879
Speaker 1: So carbon fourteen interacts with oxygen in the atmosphere to

554
00:27:19,880 --> 00:27:23,040
Speaker 1: make carbon dioxide, and so now you have these special

555
00:27:23,119 --> 00:27:26,159
Speaker 1: molecules of carbon dioxide. Most of the carbon dioxide in

556
00:27:26,200 --> 00:27:28,959
Speaker 1: the atmosphere has carbon twelve in it the normal stuff,

557
00:27:29,280 --> 00:27:33,199
Speaker 1: but about one in a trillion has a carbon fourteen atom,

558
00:27:33,520 --> 00:27:37,000
Speaker 1: So it's carbon fourteen plus two normal oxygens. And this

559
00:27:37,119 --> 00:27:39,760
Speaker 1: is just floating out there around in the atmosphere. And

560
00:27:39,840 --> 00:27:42,920
Speaker 1: so when plants, for example, do photosynthesis and they breathe

561
00:27:42,960 --> 00:27:46,600
Speaker 1: in carbon dioxide, most of the time they're breathing in normal,

562
00:27:46,680 --> 00:27:50,360
Speaker 1: the nilla carbon dioxide, but sometimes one in a trillion

563
00:27:50,480 --> 00:27:53,720
Speaker 1: they get the extra spicy version of carbon dioxide that

564
00:27:53,760 --> 00:27:56,560
Speaker 1: has carbon fourteen in it, so they take it in.

565
00:27:56,960 --> 00:27:59,840
Speaker 1: And then when you eat your impossible burger, which is

566
00:28:00,119 --> 00:28:02,320
Speaker 1: out of plants, you're eating that carbon fourteine that got

567
00:28:02,400 --> 00:28:03,719
Speaker 1: incorporated into the plant.

568
00:28:03,920 --> 00:28:09,359
Speaker 4: So do plants have more carbon fourteen than animals because

569
00:28:09,400 --> 00:28:11,600
Speaker 4: they're sucking so much of it out of the atmosphere

570
00:28:11,720 --> 00:28:13,199
Speaker 4: or is that not how it works?

571
00:28:13,359 --> 00:28:16,919
Speaker 1: Carbon fourteen definitely flows through the sort of biosphere, and

572
00:28:16,960 --> 00:28:19,040
Speaker 1: it's richest at the source, Like if you go into

573
00:28:19,080 --> 00:28:22,200
Speaker 1: the upper atmosphere, that's the highest fraction of carbon fourteen.

574
00:28:22,520 --> 00:28:24,720
Speaker 1: As you get further and further away from the source,

575
00:28:24,960 --> 00:28:27,439
Speaker 1: you get less and less carbon fourteen because it starts

576
00:28:27,440 --> 00:28:30,680
Speaker 1: to decay. Now it decays all really really slowly. So

577
00:28:30,800 --> 00:28:33,240
Speaker 1: like most plants and most animals on the surface have

578
00:28:33,320 --> 00:28:36,119
Speaker 1: about as much carbon fourteen in them as exists in

579
00:28:36,160 --> 00:28:38,600
Speaker 1: the upper atmosphere. But like the bottom of the ocean,

580
00:28:38,640 --> 00:28:42,480
Speaker 1: the deep ocean doesn't interact with the atmosphere as often,

581
00:28:42,800 --> 00:28:45,280
Speaker 1: and so the rate of carbon fourteen down there is

582
00:28:45,400 --> 00:28:47,840
Speaker 1: much less because it takes longer to get down there,

583
00:28:47,880 --> 00:28:50,480
Speaker 1: and by the time it does, some of it has decayed.

584
00:28:51,080 --> 00:28:53,840
Speaker 1: And so like deep ocean animals tend to have less

585
00:28:53,880 --> 00:28:56,880
Speaker 1: carbon fourteen than like birds that live in the high

586
00:28:56,920 --> 00:28:59,640
Speaker 1: atmosphere or you know, cows that live on the surface.

587
00:29:00,000 --> 00:29:03,600
Speaker 1: Actually map the carbon fourteen fraction over the biosphere and

588
00:29:03,640 --> 00:29:04,680
Speaker 1: see how that flows.

589
00:29:04,920 --> 00:29:07,680
Speaker 4: Okay, And so in general, we're also not really interested

590
00:29:07,720 --> 00:29:10,520
Speaker 4: in like you know, there are one hundred units of

591
00:29:10,600 --> 00:29:14,800
Speaker 4: carbon fourteen in a tree. We're interested in the relative

592
00:29:14,840 --> 00:29:19,120
Speaker 4: amounts of carbon twelve compared to carbon fourteen. Is that right?

593
00:29:19,160 --> 00:29:21,240
Speaker 4: So it's about you know, relative amounts as opposed to

594
00:29:21,320 --> 00:29:22,320
Speaker 4: absolute quantities.

595
00:29:22,480 --> 00:29:25,160
Speaker 1: Yeah, exactly. And this is the really fascinating bit about

596
00:29:25,200 --> 00:29:27,960
Speaker 1: carbon fourteen. Right. First of all, it's a natural clock.

597
00:29:28,000 --> 00:29:30,320
Speaker 1: It's this thing that happens in the universe, you create

598
00:29:30,360 --> 00:29:33,640
Speaker 1: carbon fourteen, you have about fifty seven hundred years until

599
00:29:33,640 --> 00:29:36,720
Speaker 1: it decays. The fascinating thing about carbon fourteen is that

600
00:29:36,760 --> 00:29:40,600
Speaker 1: we use it to date when something dies, right, we

601
00:29:40,640 --> 00:29:43,560
Speaker 1: can tell when something has died. And when I first

602
00:29:43,560 --> 00:29:46,120
Speaker 1: heard about this, I thought, what, how does like the

603
00:29:46,160 --> 00:29:49,120
Speaker 1: carbon know that you've died. Is it like as soon

604
00:29:49,120 --> 00:29:52,040
Speaker 1: as you die your carbon fourteen atoms start ticking or something.

605
00:29:52,080 --> 00:29:54,240
Speaker 1: I thought that was really weird, because you know, life

606
00:29:54,240 --> 00:29:57,400
Speaker 1: and death is this holistic property of an object, and

607
00:29:57,440 --> 00:30:00,760
Speaker 1: like the carbon fourteen doesn't care if you're alive or dead. Right,

608
00:30:00,840 --> 00:30:03,200
Speaker 1: So the reason that carbon fourteen is sensitive to your

609
00:30:03,240 --> 00:30:06,040
Speaker 1: moment of death is because of what you stop doing

610
00:30:06,080 --> 00:30:08,360
Speaker 1: when you die, which is you stop breathing and you

611
00:30:08,400 --> 00:30:12,200
Speaker 1: stop eating, so you stop getting new carbon fourteen. So

612
00:30:12,320 --> 00:30:15,080
Speaker 1: all the carbon fourteen in your body is always decaying.

613
00:30:15,200 --> 00:30:17,680
Speaker 1: Like that clock started when the cosmic array hit in

614
00:30:17,680 --> 00:30:19,920
Speaker 1: the upper atmosphere, and maybe it took a few hundred

615
00:30:20,000 --> 00:30:22,520
Speaker 1: years before you ate that carbon fourteen, and so that

616
00:30:22,560 --> 00:30:25,479
Speaker 1: clock has already started. What doesn't happen anymore when you

617
00:30:25,560 --> 00:30:28,320
Speaker 1: die is that you don't get any fresh carbon fourteen.

618
00:30:28,480 --> 00:30:30,480
Speaker 1: And so now the carbon fourteen in your body is

619
00:30:30,520 --> 00:30:33,760
Speaker 1: decaying and it's not being replaced. So something that died

620
00:30:33,800 --> 00:30:36,800
Speaker 1: a long time ago will have almost no carbon fourteen

621
00:30:36,840 --> 00:30:38,840
Speaker 1: in it, whereas if you died ten minutes ago, you

622
00:30:38,920 --> 00:30:41,320
Speaker 1: still have a lot of carbon fourteen in you. So

623
00:30:41,360 --> 00:30:43,600
Speaker 1: it's not really like the moment of death. It's more

624
00:30:43,640 --> 00:30:47,600
Speaker 1: like the moment you stopped participating in the biosphere, which

625
00:30:47,600 --> 00:30:48,960
Speaker 1: I guess is really the same thing.

626
00:30:49,280 --> 00:30:53,280
Speaker 4: Do like the microbes that break you down put some

627
00:30:53,320 --> 00:30:55,920
Speaker 4: more carbon fourteen in there to mess the clock up

628
00:30:55,920 --> 00:30:57,400
Speaker 4: a little. I guess it doesn't matter, because if the

629
00:30:57,440 --> 00:30:59,640
Speaker 4: half life is five thy seven hundred years, we're talking

630
00:30:59,640 --> 00:31:02,920
Speaker 4: about a week or two of microbes messing up the values.

631
00:31:03,120 --> 00:31:05,320
Speaker 1: Yeah, good question. I guess it depends a little bit

632
00:31:05,360 --> 00:31:08,760
Speaker 1: if they're aerobic or anaerobic. Right, are they consuming CO two?

633
00:31:08,840 --> 00:31:11,600
Speaker 1: I'll have to ask mycrobiologist about that, check in with

634
00:31:11,600 --> 00:31:12,480
Speaker 1: my wife about it later.

635
00:31:13,280 --> 00:31:16,120
Speaker 4: Thank you, no one. Yeah, that's right. That's very convenience.

636
00:31:16,320 --> 00:31:18,480
Speaker 1: And so this has a really interesting history. It was

637
00:31:18,520 --> 00:31:21,800
Speaker 1: like in the forties that people figured out, oh maybe

638
00:31:21,800 --> 00:31:25,080
Speaker 1: this is possible. People were studying carbon fourteen just from

639
00:31:25,080 --> 00:31:27,320
Speaker 1: like a chemistry point of view, like what is this stuff?

640
00:31:27,600 --> 00:31:29,840
Speaker 1: How long does it last? And at the time, you know,

641
00:31:29,880 --> 00:31:32,640
Speaker 1: we didn't really understand the nucleus very well. People were

642
00:31:32,680 --> 00:31:35,400
Speaker 1: making estimates for like how long it might last, and

643
00:31:35,480 --> 00:31:37,920
Speaker 1: the measurements they made were really surprising. They discovered, oh

644
00:31:37,960 --> 00:31:40,640
Speaker 1: my gosh, this stuff lasts a lot longer than we thought.

645
00:31:40,840 --> 00:31:43,760
Speaker 1: They expected to have a much shorter half life, like

646
00:31:44,080 --> 00:31:46,960
Speaker 1: tens or hundreds of years. So when they discovered that

647
00:31:47,000 --> 00:31:49,920
Speaker 1: it has a half life of almost six thousand years,

648
00:31:50,040 --> 00:31:53,440
Speaker 1: they were surprised, But it also opened up this really

649
00:31:53,440 --> 00:31:54,360
Speaker 1: cool possibility.

650
00:31:54,480 --> 00:31:58,680
Speaker 4: Why were they surprised, Like, did we expect that half

651
00:31:58,760 --> 00:32:01,400
Speaker 4: lives would be like so similar between objects on the

652
00:32:01,400 --> 00:32:04,760
Speaker 4: periodic table and they ended up not being similar?

653
00:32:04,960 --> 00:32:05,160
Speaker 7: Yah?

654
00:32:05,200 --> 00:32:07,080
Speaker 4: Is there a reason they were surprised or just sometimes

655
00:32:07,120 --> 00:32:07,920
Speaker 4: sits surprising?

656
00:32:08,560 --> 00:32:11,440
Speaker 1: They were surprised because we just didn't understand the nucleus

657
00:32:11,440 --> 00:32:13,520
Speaker 1: of the atom very well. I mean, this is the forties, right,

658
00:32:13,600 --> 00:32:16,000
Speaker 1: Quantum mechanics was very very new, and so all of

659
00:32:16,000 --> 00:32:18,560
Speaker 1: our calculations of how things work in the nucleus were

660
00:32:18,640 --> 00:32:20,960
Speaker 1: very very rough and a lot of handwaving. I mean

661
00:32:21,000 --> 00:32:24,960
Speaker 1: even today, it's not easy to do these calculations to say,

662
00:32:25,000 --> 00:32:26,720
Speaker 1: like what would be the mass of this particle or

663
00:32:26,720 --> 00:32:29,200
Speaker 1: how stable would that be. You know, we have theories

664
00:32:29,280 --> 00:32:32,200
Speaker 1: about whether the super heavy elements would be stable, but

665
00:32:32,280 --> 00:32:34,400
Speaker 1: we can't say these things for certain because we don't

666
00:32:34,440 --> 00:32:37,440
Speaker 1: know how to do a lot of these calculations. Because

667
00:32:37,480 --> 00:32:41,120
Speaker 1: the strong nuclear force is very complicated. It's very very strong,

668
00:32:41,120 --> 00:32:43,760
Speaker 1: which means the calculations are very very sensitive to getting

669
00:32:43,800 --> 00:32:45,920
Speaker 1: things wrong. It's a kind of calculation where if you

670
00:32:45,920 --> 00:32:47,960
Speaker 1: start to get things a little bit wrong, the wrongness

671
00:32:48,040 --> 00:32:50,800
Speaker 1: gets amplified by the strength of the force instead of

672
00:32:50,800 --> 00:32:53,760
Speaker 1: like decaying away. Like with gravity, if you get the

673
00:32:53,800 --> 00:32:56,280
Speaker 1: location of an asteroid a little bit wrong, it's not

674
00:32:56,320 --> 00:32:58,960
Speaker 1: going to propagate to becoming really really wrong later on

675
00:32:59,040 --> 00:33:01,560
Speaker 1: because gravity is so week, so you can make approximations

676
00:33:01,560 --> 00:33:03,360
Speaker 1: and mostly get the right answer, at least for the

677
00:33:03,360 --> 00:33:06,080
Speaker 1: foreseeable future. With the strong force, as soon as you

678
00:33:06,080 --> 00:33:08,560
Speaker 1: get something a little bit wrong, everything goes totally wrong.

679
00:33:08,640 --> 00:33:11,480
Speaker 1: So the short version is that nuclear physics is hard.

680
00:33:11,720 --> 00:33:14,160
Speaker 4: Well, that's not surprising, and so maybe they shouldn't have

681
00:33:14,200 --> 00:33:18,040
Speaker 4: been surprised because nuclear physics is hard. Okay, So you

682
00:33:18,120 --> 00:33:20,320
Speaker 4: had mentioned at the top of the show that sewage

683
00:33:20,440 --> 00:33:22,440
Speaker 4: was gonna come into the story at some point, and

684
00:33:22,440 --> 00:33:24,720
Speaker 4: so I'm hoping that now that we're talking about, you know,

685
00:33:24,920 --> 00:33:27,560
Speaker 4: when we figure out the whole carbon fourteen thing, is

686
00:33:27,560 --> 00:33:29,160
Speaker 4: this one we get to talk about the sewage.

687
00:33:29,200 --> 00:33:31,760
Speaker 1: This is when we get to talk about the sewage. Absolutely.

688
00:33:32,560 --> 00:33:36,040
Speaker 1: So it was in the mid nineteen forties and Willard Libby,

689
00:33:36,320 --> 00:33:39,280
Speaker 1: who was at Berkeley, learned about these results that carbon

690
00:33:39,360 --> 00:33:42,840
Speaker 1: fourteen was surprisingly long lasting, and he thought, hey, that

691
00:33:42,880 --> 00:33:45,160
Speaker 1: would be a really cool way to figure out how

692
00:33:45,240 --> 00:33:47,920
Speaker 1: long something has been dead. And so what he did

693
00:33:48,280 --> 00:33:50,000
Speaker 1: is he moved to a new job at University of

694
00:33:50,080 --> 00:33:53,400
Speaker 1: Chicago and he proposed this idea. He said, maybe this

695
00:33:53,440 --> 00:33:55,959
Speaker 1: will work. And the first thing they did was to

696
00:33:56,120 --> 00:34:00,680
Speaker 1: study methane from the Boston sewage system. It's a methane

697
00:34:00,800 --> 00:34:04,160
Speaker 1: is a gas, right that's produced when sewage basically ferments,

698
00:34:04,680 --> 00:34:07,440
Speaker 1: migrooves are consuming your sewage. And so they gathered this

699
00:34:07,520 --> 00:34:11,160
Speaker 1: and they measure the carbon fourteen fraction in methane basically

700
00:34:11,239 --> 00:34:14,880
Speaker 1: from Boston's dark matter, and then they compared that to

701
00:34:15,480 --> 00:34:19,560
Speaker 1: how much carbon fourteen there was in methane from fossil fuels. Right,

702
00:34:19,600 --> 00:34:21,880
Speaker 1: like the methane that maybe you burn in your house

703
00:34:22,040 --> 00:34:25,120
Speaker 1: comes from plants that died millions and millions and millions

704
00:34:25,160 --> 00:34:27,480
Speaker 1: of years ago, and what they found is no surprise

705
00:34:27,520 --> 00:34:29,920
Speaker 1: to us now, is that the methane from the Boston

706
00:34:30,000 --> 00:34:32,560
Speaker 1: sewage system has a lot of carbon fourteen and the

707
00:34:32,560 --> 00:34:34,720
Speaker 1: methane from fossil fuels has none.

708
00:34:35,360 --> 00:34:37,640
Speaker 4: All right, So that's beginning to tell us the limits

709
00:34:37,680 --> 00:34:40,040
Speaker 4: for how we can use carbon fourteen for dating. But

710
00:34:40,120 --> 00:34:43,640
Speaker 4: I'll note you said that Libby had moved to Chicago,

711
00:34:44,280 --> 00:34:47,080
Speaker 4: but he looked at the Boston sewage is there just

712
00:34:47,200 --> 00:34:50,239
Speaker 4: like is Boston sewage The best sewage he traveled all

713
00:34:50,280 --> 00:34:54,040
Speaker 4: the way to Boston was the Chicago sewage. Wasn't disgusting

714
00:34:54,040 --> 00:34:54,439
Speaker 4: with us.

715
00:34:55,520 --> 00:34:57,520
Speaker 1: I'm sure those people who live in Boston are very

716
00:34:57,560 --> 00:35:00,239
Speaker 1: proud of their sewage. I have a little glimpse into

717
00:35:00,280 --> 00:35:02,640
Speaker 1: this because of my wife's research. You know, she studies

718
00:35:02,640 --> 00:35:05,600
Speaker 1: the microbes and sewage, and it can be surprisingly tricky

719
00:35:05,640 --> 00:35:07,880
Speaker 1: to get access to it. So I suspect it's just

720
00:35:07,920 --> 00:35:11,040
Speaker 1: a question of like politics and access. Not every waste

721
00:35:11,080 --> 00:35:14,440
Speaker 1: management system is interested in having scientists like dig around

722
00:35:14,440 --> 00:35:17,680
Speaker 1: in their facility, while others are, you know, free to

723
00:35:17,719 --> 00:35:21,120
Speaker 1: share the science gold that is flowing through their pipes.

724
00:35:24,280 --> 00:35:25,320
Speaker 4: Politics and sewage.

725
00:35:25,480 --> 00:35:27,960
Speaker 1: Yeah, so I suspect they had a good Boston connect,

726
00:35:28,000 --> 00:35:30,680
Speaker 1: you know, for some real primo Boston sewage.

727
00:35:30,880 --> 00:35:34,839
Speaker 4: Got it, Okay, So by the time you ask petroleum,

728
00:35:35,000 --> 00:35:38,840
Speaker 4: there's no carbon fourteen, and you start losing carbon fourteen

729
00:35:38,960 --> 00:35:41,719
Speaker 4: when you die. So can you use this for? Is

730
00:35:41,760 --> 00:35:44,200
Speaker 4: this helpful for like certain kinds of fossils? What kind

731
00:35:44,239 --> 00:35:45,839
Speaker 4: of things have we used this for so far?

732
00:35:46,080 --> 00:35:48,600
Speaker 1: You can use this for basically anything that's died in

733
00:35:48,640 --> 00:35:51,960
Speaker 1: the last you know, maybe fifty thousand years, because those

734
00:35:52,000 --> 00:35:55,400
Speaker 1: things were accumulating carbon fourteen as they were alive and

735
00:35:55,440 --> 00:35:58,360
Speaker 1: participating in the biosphere, and as soon as they died,

736
00:35:58,440 --> 00:36:02,600
Speaker 1: then they stopped and the carbon fourteen started to decay away. Now,

737
00:36:02,640 --> 00:36:04,799
Speaker 1: things that are much much older than that, they just

738
00:36:04,840 --> 00:36:07,680
Speaker 1: have zero carbon fourteen. So you can't tell is this

739
00:36:07,719 --> 00:36:10,080
Speaker 1: thing one hundred thousand years old or one hundred million

740
00:36:10,160 --> 00:36:13,279
Speaker 1: years old or four billion years old, because you just

741
00:36:13,280 --> 00:36:15,800
Speaker 1: get zero. So what you got to do is measure

742
00:36:16,120 --> 00:36:19,359
Speaker 1: the carbon fourteen the carbon twelve ratio in your thing,

743
00:36:19,560 --> 00:36:22,160
Speaker 1: and then you're going to extrapolate back to when did

744
00:36:22,200 --> 00:36:25,239
Speaker 1: this thing last have the sort of normal rate of

745
00:36:25,280 --> 00:36:26,120
Speaker 1: carbon fourteen?

746
00:36:26,440 --> 00:36:30,000
Speaker 4: Got it all right? So dinosaurs are out, but helpful

747
00:36:30,080 --> 00:36:34,360
Speaker 4: for things like human archaeology questions exactly.

748
00:36:34,600 --> 00:36:38,640
Speaker 1: Human archaeology was really like revolutionized by this subject. The

749
00:36:38,680 --> 00:36:41,319
Speaker 1: first time that they used it was actually to date

750
00:36:41,440 --> 00:36:44,759
Speaker 1: some Egyptian tombs. These are some things that archaeologically, we

751
00:36:44,800 --> 00:36:47,759
Speaker 1: already knew what the dates were based on writing and

752
00:36:47,800 --> 00:36:52,120
Speaker 1: other analysis, Like archaeologists already knew when somebody had been buried,

753
00:36:52,200 --> 00:36:54,600
Speaker 1: and now they were able to take a sample and

754
00:36:54,719 --> 00:36:57,440
Speaker 1: measure the carbon fourteen fraction in like a piece of

755
00:36:57,480 --> 00:36:59,960
Speaker 1: linen or in a piece of wood from the two

756
00:37:00,000 --> 00:37:04,200
Speaker 1: boom and independently establish the date of the death of

757
00:37:04,280 --> 00:37:07,440
Speaker 1: that object, like here's when the tree that formed this

758
00:37:07,560 --> 00:37:10,920
Speaker 1: plank must have been killed, or here's when this plant

759
00:37:10,960 --> 00:37:14,440
Speaker 1: was harvested to make this linen. And that's really powerful.

760
00:37:14,520 --> 00:37:18,640
Speaker 1: It's like a completely separate clock that lines up archaeologically

761
00:37:18,960 --> 00:37:19,840
Speaker 1: with your records.

762
00:37:20,000 --> 00:37:22,319
Speaker 4: Okay, So one, that's awesome, and two, I bet this

763
00:37:22,400 --> 00:37:24,520
Speaker 4: has been used at some point in ways that have

764
00:37:24,600 --> 00:37:27,440
Speaker 4: made people angry, like people who thought they had a

765
00:37:27,440 --> 00:37:29,120
Speaker 4: thing that was old but it ended up not being

766
00:37:29,160 --> 00:37:32,319
Speaker 4: that old, or the other way around. But before I

767
00:37:32,360 --> 00:37:35,320
Speaker 4: ask you about that, let's take another quick break.

768
00:37:39,400 --> 00:37:41,200
Speaker 1: When you pop a piece of cheese, into your mouth

769
00:37:41,280 --> 00:37:44,440
Speaker 1: or enjoy a rich spoonful of Greek yogurt. You're probably

770
00:37:44,480 --> 00:37:48,520
Speaker 1: not thinking about the environmental impact of each and every bite,

771
00:37:48,560 --> 00:37:51,160
Speaker 1: but the people in the dairy industry are. US Dairy

772
00:37:51,200 --> 00:37:55,520
Speaker 1: has set themselves some ambitious sustainability goals, including being greenhouse

773
00:37:55,520 --> 00:37:58,120
Speaker 1: gas neutral by twenty to fifty. That's why they're working

774
00:37:58,120 --> 00:38:00,479
Speaker 1: hard every day to find new ways to reduce use, waste,

775
00:38:00,560 --> 00:38:04,759
Speaker 1: conserve natural resources, and drive down greenhouse gas emissions. Take water,

776
00:38:04,800 --> 00:38:07,879
Speaker 1: for example, most dairy farms reuse water up to four

777
00:38:07,960 --> 00:38:11,399
Speaker 1: times the same water cools the milk, cleans equipment, washes

778
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Speaker 1: the barn, and irrigates the crops. How is US dairy

779
00:38:14,280 --> 00:38:18,040
Speaker 1: tackling greenhouse gases. Many farms use anaerobic digestors that turn

780
00:38:18,080 --> 00:38:22,000
Speaker 1: the methane from maneuver into renewable energy that can power farms, towns,

781
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Speaker 1: and electric cars. So the next time you grab a

782
00:38:24,120 --> 00:38:26,160
Speaker 1: slice of pizza or lick an ice cream cone, know

783
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Speaker 1: that dairy farmers and processors around the country are using

784
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Speaker 1: the latest practices and innovations to provide the nutrient dense

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Speaker 4: All right, So, has this method been used in a

824
00:40:37,200 --> 00:40:38,840
Speaker 4: way that ended up making people ling?

825
00:40:41,320 --> 00:40:44,200
Speaker 1: Why do I feel like you're digging for the controversy here, Klly?

826
00:40:44,480 --> 00:40:45,960
Speaker 4: Well, you know it makes good radio.

827
00:40:47,360 --> 00:40:50,480
Speaker 1: It does. Absolutely. Yeah. This is a really cool technique

828
00:40:50,520 --> 00:40:52,600
Speaker 1: and it's powerful because they can date things to like

829
00:40:52,680 --> 00:40:55,359
Speaker 1: within a few decades. You know, the thing is that

830
00:40:55,400 --> 00:40:58,359
Speaker 1: there's a lot of carbon in living stuff, and the

831
00:40:58,360 --> 00:41:01,200
Speaker 1: more carbon you have, the more precise measurement can be,

832
00:41:01,480 --> 00:41:03,880
Speaker 1: so you can like pin down within a few decades

833
00:41:03,960 --> 00:41:07,040
Speaker 1: when something died. And for example, when people discovered like

834
00:41:07,080 --> 00:41:11,239
Speaker 1: the Dead Sea Scrolls, these ancient scrolls outside of Jerusalem

835
00:41:11,320 --> 00:41:13,279
Speaker 1: that had been in the desert for who knows how

836
00:41:13,360 --> 00:41:15,680
Speaker 1: long and may have been one of the earliest written

837
00:41:15,719 --> 00:41:18,439
Speaker 1: records of you know, the books of the Bible, people

838
00:41:18,480 --> 00:41:21,440
Speaker 1: wanted to know like are these real? Are they actually

839
00:41:21,480 --> 00:41:23,840
Speaker 1: thousands of years old or is this like a forgery

840
00:41:23,920 --> 00:41:28,239
Speaker 1: from last week that's been stained with tea? And so

841
00:41:28,280 --> 00:41:31,160
Speaker 1: they were able to use radiocarbon dating to confirm that

842
00:41:31,200 --> 00:41:35,200
Speaker 1: these things were one nine hundred and seventeen years old,

843
00:41:35,320 --> 00:41:37,800
Speaker 1: which really told people like, these are an ancient relic.

844
00:41:37,840 --> 00:41:40,320
Speaker 1: You know, these were not created recently, or at least

845
00:41:40,440 --> 00:41:43,960
Speaker 1: the materials on which they were made are fairly old.

846
00:41:44,040 --> 00:41:46,799
Speaker 1: So either it's a really old book or it's new

847
00:41:46,840 --> 00:41:48,840
Speaker 1: writing on a really old sheet of paper.

848
00:41:49,000 --> 00:41:51,280
Speaker 4: Well, I'm going to have to give you that. That's awesome.

849
00:41:51,400 --> 00:41:54,160
Speaker 4: That's not what I asked. I asked you for controversy,

850
00:41:54,480 --> 00:41:57,520
Speaker 4: but you gave me confirmation, but still all right, so

851
00:41:57,560 --> 00:41:58,440
Speaker 4: that's pretty awesome.

852
00:41:58,560 --> 00:42:01,279
Speaker 1: Well, this controversy also, you may have heard about the

853
00:42:01,320 --> 00:42:03,960
Speaker 1: Shroud of Turin. This is this piece of cloth that

854
00:42:04,040 --> 00:42:06,879
Speaker 1: I think is held in Milan that's supposed to have

855
00:42:06,960 --> 00:42:10,279
Speaker 1: like the face of Jesus on it, and the mythology

856
00:42:10,320 --> 00:42:12,960
Speaker 1: around it is that it wrapped to Jesus's corpse and

857
00:42:13,000 --> 00:42:15,359
Speaker 1: it was sort of imprinted by the power of his

858
00:42:15,560 --> 00:42:19,960
Speaker 1: unknown spiritual personality with his face. And so this is

859
00:42:20,000 --> 00:42:23,600
Speaker 1: a relic that's been celebrated in people like pilgrimage to

860
00:42:23,760 --> 00:42:26,400
Speaker 1: go and see it, and so they radiocarbondated it and

861
00:42:26,440 --> 00:42:30,040
Speaker 1: discovered Oops, it's actually from the fourteenth century, which means

862
00:42:30,160 --> 00:42:33,120
Speaker 1: it's pretty old. It's like six hundred years old. But

863
00:42:33,239 --> 00:42:37,240
Speaker 1: the plants that made this shroud were grown and planted

864
00:42:37,320 --> 00:42:39,960
Speaker 1: like fourteen hundred years after Jesus died.

865
00:42:40,239 --> 00:42:44,359
Speaker 4: That's disappointing. Is it safe to assume that there are

866
00:42:44,400 --> 00:42:47,520
Speaker 4: people who don't buy the science on this to this day?

867
00:42:47,719 --> 00:42:51,080
Speaker 1: Oh? Absolutely, the way people deny evolution or that the

868
00:42:51,120 --> 00:42:55,160
Speaker 1: Earth is round or the dinosaurs existed well before humans.

869
00:42:55,400 --> 00:42:58,160
Speaker 1: There are people who say radiocarbon dating is not reliable

870
00:42:58,520 --> 00:43:00,920
Speaker 1: and that you can't use it, especially, you know, when

871
00:43:00,960 --> 00:43:03,480
Speaker 1: it contradicts their belief. The thing I love about the

872
00:43:03,600 --> 00:43:06,960
Speaker 1: Shroud of Turn story is not just that it reveals

873
00:43:07,000 --> 00:43:08,719
Speaker 1: that the whole thing is a hoax, but it's an

874
00:43:08,800 --> 00:43:13,359
Speaker 1: ancient hoax. The hoax is now hundreds of years old, right,

875
00:43:13,440 --> 00:43:16,920
Speaker 1: The hoax itself is of historical interest. That's how old

876
00:43:16,960 --> 00:43:19,960
Speaker 1: it is, right, A six hundred year old hoax is

877
00:43:20,000 --> 00:43:22,720
Speaker 1: pretty cool. Okay, it's not the face of Jesus, but wow,

878
00:43:22,880 --> 00:43:25,160
Speaker 1: that's really cool insight and like what people were doing

879
00:43:25,200 --> 00:43:26,919
Speaker 1: and why they wanted to do it, and all sorts

880
00:43:26,960 --> 00:43:29,839
Speaker 1: of stuff. I love how like today's mundanity, right, and

881
00:43:29,880 --> 00:43:34,880
Speaker 1: even lies can turn into something fascinating for future anthropologists.

882
00:43:35,000 --> 00:43:37,600
Speaker 4: Ye know, humans have enjoyed messing with each other for

883
00:43:37,640 --> 00:43:40,040
Speaker 4: a really long time. It's good to know that.

884
00:43:40,640 --> 00:43:43,200
Speaker 1: But it is tricky to date things with carbon fourteen

885
00:43:43,400 --> 00:43:45,880
Speaker 1: because it turns out that the assumption we made at

886
00:43:45,920 --> 00:43:48,520
Speaker 1: the beginning, that like carbon fourteen is produced in the

887
00:43:48,600 --> 00:43:52,640
Speaker 1: upper atmosphere and spreads around mostly evenly to everything not

888
00:43:52,960 --> 00:43:56,160
Speaker 1: exactly true. And so you got to like make some

889
00:43:56,320 --> 00:43:59,759
Speaker 1: corrections and calibrations to get things as precise as you'd like.

890
00:44:00,080 --> 00:44:04,560
Speaker 4: So, like how not exact. Are we talking here like

891
00:44:04,640 --> 00:44:07,080
Speaker 4: you know the flies that you find in bodies? I

892
00:44:07,080 --> 00:44:10,200
Speaker 4: think things like temperature impact development time. How many things

893
00:44:10,360 --> 00:44:13,920
Speaker 4: impact our ability to date things based on carbon fourteen

894
00:44:13,960 --> 00:44:15,839
Speaker 4: And are they things that we can learn about and

895
00:44:15,880 --> 00:44:17,480
Speaker 4: control for or.

896
00:44:17,680 --> 00:44:19,879
Speaker 1: No, Yes, absolutely we can learn about them. And it's

897
00:44:20,000 --> 00:44:23,560
Speaker 1: a whole field of people calibrating carbon fourteen dating. We

898
00:44:23,640 --> 00:44:27,239
Speaker 1: first discovered this actually when carbon fourteen dating got some

899
00:44:27,360 --> 00:44:30,759
Speaker 1: Egyptian tombs wrong, like some of them were bang on

900
00:44:30,840 --> 00:44:34,280
Speaker 1: the archaeological records, and other ones that archaeologists were pretty

901
00:44:34,320 --> 00:44:37,839
Speaker 1: sure about. Radiocarbon dating got a little wrong, and people thought, hmm,

902
00:44:38,120 --> 00:44:40,799
Speaker 1: that's weird. I wonder what it means. And so they

903
00:44:40,840 --> 00:44:44,480
Speaker 1: discovered a few interesting effects. For example, carbon fourteen production

904
00:44:44,800 --> 00:44:47,720
Speaker 1: is not constant over time. If you want to assume

905
00:44:47,719 --> 00:44:50,920
Speaker 1: that you can extrapolate backwards from the carbon fourteen ratio

906
00:44:50,960 --> 00:44:54,680
Speaker 1: today to the carbon fourteen ratio when this object died,

907
00:44:54,719 --> 00:44:57,360
Speaker 1: you have to assume that carbon fourteen is being replenished

908
00:44:57,360 --> 00:44:59,640
Speaker 1: at the same rate over time. But it turns out

909
00:45:00,120 --> 00:45:03,160
Speaker 1: that it's not that there's a variation in the carbon

910
00:45:03,200 --> 00:45:05,359
Speaker 1: fourteen rates in the atmosphere.

911
00:45:05,440 --> 00:45:08,799
Speaker 4: WHOA and is that because cosmic rays hit us at

912
00:45:08,800 --> 00:45:10,840
Speaker 4: different rates. Is this like a solar Now that's not

913
00:45:10,840 --> 00:45:14,000
Speaker 4: a solar wind thing? Do we know? Yeah? Why I

914
00:45:14,040 --> 00:45:14,759
Speaker 4: am confused.

915
00:45:15,360 --> 00:45:18,360
Speaker 1: It's really interesting and there's some cool physics there. One

916
00:45:18,440 --> 00:45:21,120
Speaker 1: is that, yes, cosmic rays have sort of like seasons.

917
00:45:21,160 --> 00:45:23,799
Speaker 1: They are not totally constant. It's sort of like the

918
00:45:23,880 --> 00:45:26,960
Speaker 1: solar weather. You know, where these cosmic rays come from

919
00:45:27,000 --> 00:45:30,319
Speaker 1: depend on like magnetic fields and the galaxy. You know

920
00:45:30,360 --> 00:45:32,759
Speaker 1: what's going on with the objects that are created them.

921
00:45:33,120 --> 00:45:35,520
Speaker 1: So there's those kinds of effects. But we can actually

922
00:45:35,560 --> 00:45:39,120
Speaker 1: measure that in independent ways because they can look at

923
00:45:39,320 --> 00:45:44,439
Speaker 1: super ancient trees. Right. Trees are really cool because they

924
00:45:44,480 --> 00:45:47,360
Speaker 1: grow and they add rings, and those new rings interact

925
00:45:47,400 --> 00:45:51,200
Speaker 1: with the biosphere, but the old rings don't. So every

926
00:45:51,280 --> 00:45:54,680
Speaker 1: year a tree is basically like taking a sample of

927
00:45:54,719 --> 00:45:58,440
Speaker 1: the carbon fourteen fraction in the atmosphere and storing it forever.

928
00:45:58,719 --> 00:46:01,520
Speaker 1: And so if you slice open a really old tree

929
00:46:01,719 --> 00:46:03,919
Speaker 1: and look back at the carbon fourteen fraction in each

930
00:46:03,960 --> 00:46:06,600
Speaker 1: of the rings, you can get like a history of

931
00:46:06,600 --> 00:46:09,440
Speaker 1: the carbon fourteen fraction at the time that the tree

932
00:46:09,520 --> 00:46:10,040
Speaker 1: was growing.

933
00:46:10,239 --> 00:46:12,399
Speaker 4: Do you happen to know what the oldest tree? We've

934
00:46:12,440 --> 00:46:15,040
Speaker 4: done that on is are we talking about, like hundreds

935
00:46:15,040 --> 00:46:17,160
Speaker 4: of years worth of data are thousands We.

936
00:46:17,160 --> 00:46:19,160
Speaker 1: Have lots that are hundreds of years and a few

937
00:46:19,239 --> 00:46:21,879
Speaker 1: that are thousands of years, and so that really helps

938
00:46:21,960 --> 00:46:25,080
Speaker 1: us calibrate like the more recent fluctuations in carbon fourteen.

939
00:46:25,480 --> 00:46:29,600
Speaker 1: But also humans have really altered the carbon fourteen fraction

940
00:46:29,840 --> 00:46:33,120
Speaker 1: in the atmosphere. For example, we've been burning a lot

941
00:46:33,160 --> 00:46:35,680
Speaker 1: of fossil fuels over the last couple of hundred years.

942
00:46:36,120 --> 00:46:40,560
Speaker 1: Fossil fuels have carbon but no carbon fourteen, So we've

943
00:46:40,560 --> 00:46:43,279
Speaker 1: been releasing a lot of carbon twelve into the atmosphere,

944
00:46:43,360 --> 00:46:47,360
Speaker 1: really bringing down the carbon fourteen fraction in the atmosphere. So,

945
00:46:47,440 --> 00:46:50,440
Speaker 1: like human effects have really changed this and made it

946
00:46:50,520 --> 00:46:52,400
Speaker 1: more complicated to interpret the past.

947
00:46:52,560 --> 00:46:55,239
Speaker 4: Wow. So like if you were an alien trying to

948
00:46:55,320 --> 00:46:58,719
Speaker 4: age stuff that was happening down here on Earth and

949
00:46:58,800 --> 00:47:01,680
Speaker 4: you wanted to something you know, thousands of years from

950
00:47:01,719 --> 00:47:04,920
Speaker 4: now that happened during our period, it would be a mess.

951
00:47:05,520 --> 00:47:07,840
Speaker 1: It would be a mess if you didn't have ways

952
00:47:07,840 --> 00:47:10,759
Speaker 1: to calibrate it. And so fortunately, like trees can help

953
00:47:10,840 --> 00:47:12,920
Speaker 1: us understand these things. Because trees have been around for

954
00:47:13,000 --> 00:47:15,279
Speaker 1: hundreds of years since, we can understand the effect the

955
00:47:15,480 --> 00:47:19,200
Speaker 1: humans have had on the carbon fourteen fraction in the atmosphere,

956
00:47:19,600 --> 00:47:22,960
Speaker 1: but more confusingly, we've had effects in both directions. So

957
00:47:23,040 --> 00:47:26,520
Speaker 1: burning fossil fuels lowers the carbon fourteen fraction because you're

958
00:47:26,520 --> 00:47:29,720
Speaker 1: pumping out super old carbon where everything is already decayed.

959
00:47:29,760 --> 00:47:33,760
Speaker 1: But nuclear testing in the atmosphere increases the carbon fourteen

960
00:47:33,800 --> 00:47:36,480
Speaker 1: fraction because it makes new carbon fourteen. Is all this

961
00:47:36,640 --> 00:47:40,000
Speaker 1: radiation and all the products of the nuclear testing makes

962
00:47:40,160 --> 00:47:42,880
Speaker 1: lots and lots of carbon fourteen, much more than it's

963
00:47:42,920 --> 00:47:45,680
Speaker 1: made from cosmic rays. So like in the middle of

964
00:47:45,719 --> 00:47:48,440
Speaker 1: this century, we had like twice as much carbon fourteen

965
00:47:48,480 --> 00:47:50,600
Speaker 1: in the atmosphere as we usually do.

966
00:47:50,800 --> 00:47:55,600
Speaker 4: Where are the worst That'll be another interesting problem for

967
00:47:55,640 --> 00:47:58,040
Speaker 4: the aliens to solve. Then where did all this carbon

968
00:47:58,080 --> 00:48:00,640
Speaker 4: fourteen come from? Oh, they were setting off new weapons

969
00:48:00,640 --> 00:48:02,359
Speaker 4: in the sky, of course there were.

970
00:48:03,320 --> 00:48:06,480
Speaker 1: It's fascinating because there are two sides to that. Archaeologists

971
00:48:06,480 --> 00:48:09,600
Speaker 1: are frustrated by that, because we're like poisoning the historical

972
00:48:09,640 --> 00:48:12,200
Speaker 1: record and making it harder to figure out when things

973
00:48:12,280 --> 00:48:16,120
Speaker 1: came from. But geologists actually really like it because it's

974
00:48:16,160 --> 00:48:18,440
Speaker 1: like a really bright signal. They're like, okay, cool, we

975
00:48:18,480 --> 00:48:20,680
Speaker 1: can use this to calibrate and we can tell when

976
00:48:20,760 --> 00:48:23,760
Speaker 1: something happened because there's so much carbon fourteen in that layer.

977
00:48:24,000 --> 00:48:26,000
Speaker 1: So geologists, I think would like us to be like

978
00:48:26,080 --> 00:48:30,840
Speaker 1: regularly nuking the atmosphere in predictable and periodic ways because

979
00:48:30,840 --> 00:48:33,440
Speaker 1: it leaves like this ruler back in the record.

980
00:48:33,760 --> 00:48:35,719
Speaker 4: You know. I know a geologist I think is not

981
00:48:35,840 --> 00:48:39,480
Speaker 4: quite that self interested, but I can imagine him thinking

982
00:48:39,520 --> 00:48:42,560
Speaker 4: that that's a silver lining of an author thing. Humans

983
00:48:42,560 --> 00:48:43,359
Speaker 4: are complicated.

984
00:48:43,480 --> 00:48:46,000
Speaker 1: So yeah, so you have to take all this into account,

985
00:48:46,080 --> 00:48:47,960
Speaker 1: and you have to know, like what was the rate

986
00:48:48,000 --> 00:48:50,600
Speaker 1: of carbon fourteen in the atmosphere over the last few

987
00:48:50,640 --> 00:48:52,960
Speaker 1: thousand years, And you also have to take into account

988
00:48:53,040 --> 00:48:55,279
Speaker 1: where you have found something. If you found it in

989
00:48:55,320 --> 00:48:57,120
Speaker 1: the deep ocean, then it was going to get less

990
00:48:57,120 --> 00:48:59,719
Speaker 1: carbon fourteen to begin with, and then if you found

991
00:48:59,719 --> 00:49:03,239
Speaker 1: it in the upper atmosphere. Also, the different hemispheres of

992
00:49:03,280 --> 00:49:06,840
Speaker 1: Earth have different depositions of carbon fourteen because there's different

993
00:49:06,880 --> 00:49:09,359
Speaker 1: like patterns of winds, and the North and the South

994
00:49:09,400 --> 00:49:13,640
Speaker 1: hemisphere actually have totally separate, independent wind systems that don't

995
00:49:13,719 --> 00:49:17,000
Speaker 1: really mix very well. So there's less carbon fourteen in

996
00:49:17,040 --> 00:49:20,520
Speaker 1: the southern atmosphere because it's like more surface area of ocean,

997
00:49:20,880 --> 00:49:23,640
Speaker 1: which sucks up more carbon fourteen, and there's more carbon

998
00:49:23,640 --> 00:49:27,160
Speaker 1: fourteen in the northern hemisphere where there's less ocean surface.

999
00:49:27,440 --> 00:49:30,000
Speaker 4: Do you have any sense for like for the hemisphere thing?

1000
00:49:30,040 --> 00:49:32,600
Speaker 4: Are we talking like if you didn't correct for that,

1001
00:49:32,640 --> 00:49:35,560
Speaker 4: you'd be off by about ten years or one thousand

1002
00:49:35,680 --> 00:49:37,520
Speaker 4: years or it just kind of depends on a lot

1003
00:49:37,560 --> 00:49:38,239
Speaker 4: of other stuff too.

1004
00:49:38,480 --> 00:49:41,359
Speaker 1: These all are really small effects, and everybody wants really

1005
00:49:41,400 --> 00:49:43,960
Speaker 1: precise dating of things, you know, down to the decades,

1006
00:49:44,120 --> 00:49:45,840
Speaker 1: and so this is the kind of thing that happens

1007
00:49:45,840 --> 00:49:48,880
Speaker 1: in science. First you have a very approximate effect. You're like, okay,

1008
00:49:48,960 --> 00:49:52,160
Speaker 1: let's just assume carbon fourteen is constant everywhere and over time.

1009
00:49:52,560 --> 00:49:54,799
Speaker 1: What do we get? Oh my gosh, it can teach

1010
00:49:54,880 --> 00:49:57,680
Speaker 1: us something already. Then you start to hone in on

1011
00:49:57,760 --> 00:50:00,480
Speaker 1: the details you want, like the second digit to be accurate,

1012
00:50:00,520 --> 00:50:02,600
Speaker 1: and then the third, and then the fourth, and by

1013
00:50:02,640 --> 00:50:06,280
Speaker 1: now we're like, you know, seventy years into this research project,

1014
00:50:06,320 --> 00:50:08,360
Speaker 1: we're getting down to the nitty gritty detail. So a

1015
00:50:08,360 --> 00:50:11,880
Speaker 1: lot of these things will affect our estimate for the

1016
00:50:11,960 --> 00:50:15,080
Speaker 1: dates of things by decades or maybe up to hundreds

1017
00:50:15,120 --> 00:50:17,279
Speaker 1: of years, not thousands of years. It's not going to

1018
00:50:17,320 --> 00:50:20,600
Speaker 1: like upend everything we thought we knew. We also need

1019
00:50:20,640 --> 00:50:24,400
Speaker 1: a really precise estimate of the half life of carbon fourteen, right,

1020
00:50:24,440 --> 00:50:26,520
Speaker 1: we have to be able to calibrate this clock to

1021
00:50:26,640 --> 00:50:30,240
Speaker 1: know how long does it take carbon fourteen to decay?

1022
00:50:30,480 --> 00:50:32,319
Speaker 1: And as you said, you can't wait around for five

1023
00:50:32,360 --> 00:50:34,680
Speaker 1: thousand years, which would be the best way to get

1024
00:50:34,680 --> 00:50:37,160
Speaker 1: an accurate measurement. But people have been developing more and

1025
00:50:37,160 --> 00:50:40,800
Speaker 1: more precise experiments with like larger samples of carbon fourteen,

1026
00:50:40,960 --> 00:50:44,040
Speaker 1: so they actually had to update the official half life

1027
00:50:44,040 --> 00:50:47,799
Speaker 1: of carbon fourteen from fifty five sixty eight later to

1028
00:50:48,000 --> 00:50:50,640
Speaker 1: fifty seven thirty, so it changes like one hundred and

1029
00:50:50,680 --> 00:50:53,640
Speaker 1: fifty years. And this is super fascinating because it then

1030
00:50:53,719 --> 00:50:57,120
Speaker 1: required a change of all the archaeological dates. Like all

1031
00:50:57,160 --> 00:50:59,239
Speaker 1: the archaeologists who thought that their thing was data a

1032
00:50:59,320 --> 00:51:02,200
Speaker 1: certain date. Oops, I got updated because the nuclear physicists

1033
00:51:02,280 --> 00:51:04,160
Speaker 1: or the chemists got the number wrong.

1034
00:51:04,719 --> 00:51:07,719
Speaker 4: Does that mean that you get to redo all of

1035
00:51:07,719 --> 00:51:11,200
Speaker 4: your publications with the updated date and double the number

1036
00:51:11,200 --> 00:51:13,720
Speaker 4: of lines you have on your CV because in that case,

1037
00:51:13,760 --> 00:51:14,919
Speaker 4: thank you physicists.

1038
00:51:15,200 --> 00:51:17,080
Speaker 1: It means that there's a bunch of papers out there

1039
00:51:17,080 --> 00:51:19,920
Speaker 1: with old dates that we now like know need corrections.

1040
00:51:19,880 --> 00:51:22,759
Speaker 1: So you can't just read the old papers in archaeology

1041
00:51:22,760 --> 00:51:24,440
Speaker 1: and take the dates at face value. You have to

1042
00:51:24,480 --> 00:51:27,960
Speaker 1: know when that date was calculated, like what effects did

1043
00:51:27,960 --> 00:51:30,600
Speaker 1: they take into account? And what effects do we now

1044
00:51:30,760 --> 00:51:33,160
Speaker 1: take into account. So the whole thing has gotten really

1045
00:51:33,200 --> 00:51:36,680
Speaker 1: really complicated. That is frustrating, but it also has been

1046
00:51:36,719 --> 00:51:40,600
Speaker 1: an enormous boon to archaeology. I mean, what a powerful tool,

1047
00:51:40,680 --> 00:51:43,640
Speaker 1: Like anything that was alive now you can date the

1048
00:51:43,680 --> 00:51:47,000
Speaker 1: moment of its death. And that's not a perfect tool, right,

1049
00:51:47,040 --> 00:51:49,560
Speaker 1: There's still thinks like when was this metal forged? Well,

1050
00:51:49,600 --> 00:51:51,640
Speaker 1: we can't tell because it was never alive. It doesn't

1051
00:51:51,680 --> 00:51:55,040
Speaker 1: participate in the carbon biosphere, so you can't date like

1052
00:51:55,160 --> 00:51:58,200
Speaker 1: jewelry or swords or stuff like that. But you can

1053
00:51:58,239 --> 00:52:00,959
Speaker 1: look at what else is any and you can tell

1054
00:52:01,000 --> 00:52:04,759
Speaker 1: maybe when that person died. And before this, archaeologists had

1055
00:52:05,080 --> 00:52:08,120
Speaker 1: much more rudimentary methods. You know, they had this like

1056
00:52:08,360 --> 00:52:11,080
Speaker 1: layer method where they would like count down from the

1057
00:52:11,120 --> 00:52:14,080
Speaker 1: ground and try to like find things that they knew

1058
00:52:14,200 --> 00:52:16,799
Speaker 1: happened that they could use to like sandwich when their

1059
00:52:16,880 --> 00:52:20,280
Speaker 1: relics might have been buried. So it was very, very rough,

1060
00:52:20,760 --> 00:52:22,839
Speaker 1: and now we have this way to like measure for

1061
00:52:22,920 --> 00:52:25,720
Speaker 1: these objects when they died. It's super powerful.

1062
00:52:25,840 --> 00:52:28,120
Speaker 4: It's super powerful. But I wonder if there was also

1063
00:52:28,160 --> 00:52:30,640
Speaker 4: a generation of scientists who were, like, you know, the

1064
00:52:30,680 --> 00:52:33,160
Speaker 4: whole reason I got into archaeologies because I don't want

1065
00:52:33,200 --> 00:52:35,480
Speaker 4: to be in the lab, and now I have to

1066
00:52:35,520 --> 00:52:37,839
Speaker 4: be in the lab to get these dates. But on

1067
00:52:37,880 --> 00:52:39,840
Speaker 4: the other hand, I think we all benefit when we

1068
00:52:39,880 --> 00:52:42,360
Speaker 4: get accurate, precise information.

1069
00:52:42,760 --> 00:52:45,680
Speaker 1: Yeah, I think that's probably true. After this was discovered,

1070
00:52:45,840 --> 00:52:48,200
Speaker 1: very rapidly, a bunch of labs were set up around

1071
00:52:48,200 --> 00:52:51,040
Speaker 1: the world to start doing radiocarbon dating. So it's not

1072
00:52:51,080 --> 00:52:53,400
Speaker 1: the kind of thing that like a typical archaeologist so

1073
00:52:53,640 --> 00:52:56,600
Speaker 1: does in the field, or every archaeologist has their own

1074
00:52:56,960 --> 00:52:59,880
Speaker 1: radiocarbon setup. It's a little bit of an involved process.

1075
00:53:00,000 --> 00:53:02,640
Speaker 1: What you have to do is measure the carbon fourteen ratio.

1076
00:53:02,840 --> 00:53:04,239
Speaker 1: In the old days, what they did was just sort

1077
00:53:04,280 --> 00:53:07,839
Speaker 1: of like count the radiation emitted because it's emitting betaies

1078
00:53:08,160 --> 00:53:11,479
Speaker 1: when it's decaying. So that was the old strategy. More

1079
00:53:11,520 --> 00:53:15,200
Speaker 1: recently they have a more precise strategy which uses mass spectrometer,

1080
00:53:15,320 --> 00:53:17,880
Speaker 1: so it like takes a sample of it, accelerates it

1081
00:53:17,960 --> 00:53:20,440
Speaker 1: bends it through a magnetic field, and then it'll bend

1082
00:53:20,560 --> 00:53:22,840
Speaker 1: more if it has low mass and less if it

1083
00:53:22,880 --> 00:53:25,640
Speaker 1: has high mass. So it gives you like a spectrum

1084
00:53:25,680 --> 00:53:28,560
Speaker 1: of the mass of the object that you're sampling, and

1085
00:53:28,600 --> 00:53:31,239
Speaker 1: you can tell how much carbon fourteen, how much carbon

1086
00:53:31,280 --> 00:53:33,680
Speaker 1: twelve is in there. You don't have to wait for

1087
00:53:33,719 --> 00:53:36,400
Speaker 1: the carbon fourteen to decay, so you're getting to take

1088
00:53:36,400 --> 00:53:39,279
Speaker 1: advantage of like all the carbon fourteen in there, not

1089
00:53:39,400 --> 00:53:41,920
Speaker 1: just the ones that happen to be decaying as you're watching.

1090
00:53:42,040 --> 00:53:44,719
Speaker 1: So these are pretty specialized techniques now, and I think

1091
00:53:44,760 --> 00:53:47,720
Speaker 1: most archaeologists like will send a sample to the lab

1092
00:53:48,160 --> 00:53:50,120
Speaker 1: rather than like doing it themselves. So I think you

1093
00:53:50,160 --> 00:53:53,440
Speaker 1: still have like old school Indiana Jones types out there

1094
00:53:53,480 --> 00:53:59,160
Speaker 1: in the field, gathering stuff, plundering sites exactly. Oh man,

1095
00:53:59,200 --> 00:54:01,400
Speaker 1: the ethics of ourology, and that's something I want to

1096
00:54:01,440 --> 00:54:01,879
Speaker 1: get into.

1097
00:54:02,200 --> 00:54:03,560
Speaker 4: Yeah, nodalistic with science.

1098
00:54:03,760 --> 00:54:06,640
Speaker 1: Yeah, but then sending those samples to a lab to

1099
00:54:06,719 --> 00:54:08,600
Speaker 1: do the dating. So you probably have like a division.

1100
00:54:09,239 --> 00:54:11,960
Speaker 1: You know, we have the radiocarbon archaeologists in the lab

1101
00:54:12,000 --> 00:54:13,480
Speaker 1: and the folks who are not in the lab.

1102
00:54:13,640 --> 00:54:17,400
Speaker 4: Okay, well, let's step away from the ethical quandaries presented

1103
00:54:17,440 --> 00:54:22,960
Speaker 4: to us by archaeology and talk about dinosaurs. So sorry,

1104
00:54:23,000 --> 00:54:26,360
Speaker 4: So we've we've established unfortunately early on, that carbon fourteen

1105
00:54:26,440 --> 00:54:28,759
Speaker 4: is not helped for dinosaurs. Is there something we can

1106
00:54:28,880 --> 00:54:32,640
Speaker 4: use if we're interested in when a dinosaur bone, you know,

1107
00:54:32,680 --> 00:54:33,719
Speaker 4: when the dinosaur died.

1108
00:54:34,600 --> 00:54:37,960
Speaker 1: Dinosaurs are tricky, absolutely, because this clock has all run out.

1109
00:54:38,239 --> 00:54:41,560
Speaker 1: All carbon fourteen that was in dinosaurs has now decayed.

1110
00:54:41,680 --> 00:54:44,520
Speaker 1: So what you need are longer clocks. We did an

1111
00:54:44,520 --> 00:54:49,040
Speaker 1: episode about using uranium to date stuff because this is

1112
00:54:49,040 --> 00:54:52,959
Speaker 1: this cool relationship between uranium and lead. Uranium two thirty

1113
00:54:53,000 --> 00:54:55,520
Speaker 1: eight and uranium two thirty five have half lives of

1114
00:54:55,560 --> 00:54:58,600
Speaker 1: more than a million years, and so they're useful for

1115
00:54:58,719 --> 00:55:01,880
Speaker 1: dating stuff that's super due old. And when they form,

1116
00:55:01,960 --> 00:55:06,839
Speaker 1: this cool thing happens. They get these zircon crystals zr con.

1117
00:55:07,040 --> 00:55:10,279
Speaker 1: And when those zircon crystals form, they reject any lead

1118
00:55:10,320 --> 00:55:13,120
Speaker 1: and they like expel lead from inside the crystal. So

1119
00:55:13,120 --> 00:55:16,319
Speaker 1: when they're formed, they're like lead free, but they do

1120
00:55:16,360 --> 00:55:20,719
Speaker 1: take uranium in them, and uranium decays into lead. So

1121
00:55:20,760 --> 00:55:22,520
Speaker 1: each one is like a little clock. If you pick

1122
00:55:22,560 --> 00:55:25,400
Speaker 1: up a zircon crystal and measure how much lead is

1123
00:55:25,440 --> 00:55:27,960
Speaker 1: inside of it, you can tell when it was formed.

1124
00:55:28,400 --> 00:55:31,760
Speaker 1: So now we're dating like when a rock cooled into

1125
00:55:31,800 --> 00:55:33,760
Speaker 1: these crystals, which is pretty cool.

1126
00:55:34,040 --> 00:55:36,239
Speaker 4: That's awesome. And so then you're measure in the rock

1127
00:55:36,280 --> 00:55:37,720
Speaker 4: around the fossils or something.

1128
00:55:37,880 --> 00:55:41,560
Speaker 1: Yeah, exactly, No, dinosaur bones don't have this stuff in them.

1129
00:55:41,719 --> 00:55:46,160
Speaker 1: But sometimes around the dinosaur bones there's like cooled magma.

1130
00:55:46,440 --> 00:55:50,839
Speaker 1: So this igneous rock. Because fossils only form in sedimentary rock.

1131
00:55:51,120 --> 00:55:53,840
Speaker 1: But if you have like layers of igneous rock above

1132
00:55:53,880 --> 00:55:56,480
Speaker 1: and below your fossil, then you can use the zircon

1133
00:55:56,520 --> 00:56:00,000
Speaker 1: crystals in those rocks to figure out when those crystals

1134
00:56:00,200 --> 00:56:03,160
Speaker 1: were formed and therefore racket your dinosaur bones, so you

1135
00:56:03,200 --> 00:56:06,560
Speaker 1: can tell roughly when it must have existed. Yay science,

1136
00:56:07,320 --> 00:56:09,880
Speaker 1: Yay science. I was always puzzled as a kid when

1137
00:56:09,880 --> 00:56:12,040
Speaker 1: people would talk about like the age of rocks. I'm like,

1138
00:56:12,280 --> 00:56:14,960
Speaker 1: what does that mean, Like when it's a rock born? Right,

1139
00:56:15,280 --> 00:56:17,759
Speaker 1: rock was never alive. And it's only later that I

1140
00:56:17,880 --> 00:56:20,879
Speaker 1: understood that they're talking about when the rock cooled. Because

1141
00:56:20,880 --> 00:56:23,200
Speaker 1: you have like that blob of magma. It was still

1142
00:56:23,200 --> 00:56:25,719
Speaker 1: basically rock. It was just like liquid rock. But it's

1143
00:56:25,719 --> 00:56:28,680
Speaker 1: when it's cooled into a rock and formed crystal. That's

1144
00:56:28,760 --> 00:56:31,480
Speaker 1: what they're interested and that's what they're measuring. It's like saying,

1145
00:56:31,760 --> 00:56:34,080
Speaker 1: how old is my ice cube? Well, you know, the

1146
00:56:34,160 --> 00:56:36,719
Speaker 1: water in it has been water forever, but it's only

1147
00:56:36,800 --> 00:56:38,160
Speaker 1: been an ice cube since you put it in the

1148
00:56:38,160 --> 00:56:41,040
Speaker 1: freezer last Tuesday. So that's like the age of your

1149
00:56:41,080 --> 00:56:42,359
Speaker 1: ice cube in the same way.

1150
00:56:42,440 --> 00:56:43,560
Speaker 4: That's a good way to explain it.

1151
00:56:43,640 --> 00:56:46,200
Speaker 1: So yeah, that's the story of radiocarbon dating. There's an

1152
00:56:46,200 --> 00:56:50,360
Speaker 1: incredible cool process where clocks are created in the upper

1153
00:56:50,360 --> 00:56:53,960
Speaker 1: atmosphere and then drift down into the biosphere inhaled by

1154
00:56:54,000 --> 00:56:57,680
Speaker 1: plants eaten by you, and then stop ticking as soon

1155
00:56:57,719 --> 00:57:00,879
Speaker 1: as you stop eating and breathing. Thanks very much Kelly

1156
00:57:00,920 --> 00:57:04,200
Speaker 1: for joining us on this trip into debunking the Shroud

1157
00:57:04,239 --> 00:57:06,640
Speaker 1: of Turn and confirming the Dead Sea scrolls.

1158
00:57:06,920 --> 00:57:08,799
Speaker 4: Thanks for bringing me along on the trip. I had

1159
00:57:08,800 --> 00:57:10,560
Speaker 4: a great time, all.

1160
00:57:10,520 --> 00:57:12,560
Speaker 1: Right, And thanks everyone for listening. And if you have

1161
00:57:12,680 --> 00:57:15,200
Speaker 1: questions about how something works, please don't be shy. Write

1162
00:57:15,200 --> 00:57:18,320
Speaker 1: to us two questions at Daniel and Jorge dot com.

1163
00:57:18,360 --> 00:57:19,360
Speaker 1: Tune in next time.

1164
00:57:19,520 --> 00:57:25,520
Speaker 4: Bye.

1165
00:57:28,280 --> 00:57:31,080
Speaker 1: Thanks for listening, and remember that Daniel and Jorge explain

1166
00:57:31,120 --> 00:57:35,080
Speaker 1: the universe is a production of iHeartRadio. For more podcasts

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Speaker 1: from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever

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