How Carbon-14 Dating Works

right for a prime time show, yep. So go to s y s K live dot com and follow the links to get information and tickets and we'll see you guys in January. Welcome to Stuff You Should Know, a production of My Heart Radios How Stuff Works. Hey, and welcome to the podcast. I'm Josh Clark. There's Charles W. Chuck Bryan over there. There's Jerry right there, just laughing it up. Yeah, and this is Stuff you should Know. The jokes are Jerry ed issue Dent Science Edition a

k a. Chuck Dies Slowly inside Edition. Dude, No, it's not You're gonna do just fine. This is all so intuitive, it's wonderful. I'm not worried about not doing fine, but thanks for the Reachirch. Well then I'm I'm really excited about this. If you know that, I think you're gonna do fine. You are going to as well. I'm going to see to it. I think Jerry's gonna do great. Jerry, how how are you doing over there? Okay, she's pressing

buttons like I've never seen her press buttons. Stop to that. Um, I wonder what kind of weird sound effects just happened after touching all those buttons. Jerry just laughed. I don't know if the mic pick that up. All right, everybody's like, okay, you're officially stalling now. Jerry's a quiet laugher. Though you ever noticed that it's all knows, Yeah, she's all knows. This is Jerry laughing hard. There's some doing it right now. Serious a SMR triggering going on right now, that's right.

And there's of this not on the microphone cover, all right, Carbon fourteen dating It works sort of the end. It's not the worst description of it ever. Yeah, we can do better than that, though, Yes, and luckily you did a great job with this. But I also you know, my advice to anyone if you don't understand the science thing, and you're an adult, just don't worry about what anyone

behind you thinks. Just looking at your laptop and you go to the most rudimentary children's science website you can find, and that always helps. There is no shame in that, no shame because seriously, the people who write those websites are probably some of the best science explainers on the planet and they know how to really just not dumb it down because kids are smart. But that's funny. You

flip flopped on kids. Apparently you mean stupid kids. Yeah, you always said they were dumb until just now, So good for you, Chuck. We're all over the map. Well,

I feel like we're really growing up these days. So so Carbon four Team, for those of you who don't know, is this um really clever scientific method where you can actually kind of look inside of a material and figure out how much carbon fourteen is in there, and by doing so, you can actually tell how old it is, or at least how long ago it was since the thing you're dating was alive. Yes, and it is a comparative Well, there's another word for that. What's it called

relative dating? Yeah, relative dating, I guess comparative isn't the worst word, especially if you're talking about literature, right because what they're doing is comparing it to things that are alive today, and because of all the gobbledygook we're about to talk about, that equals a pretty good estimate. And then from there they are even further things that one can do if one we're so inclined as a scientist, and there are a lot of people who are inclined

to do this. This is a very exciting, um energetic field of science right now, Like if you want to, if you want to jump into an ever evolving, constantly moving be a um field, the Baracas field kind of um of of science, start studying radiocarbon dating actually wouldn't be a ba Barakas field because didn't that stand for bad attitude? Did it? I think so? Right? Oh, no, one in radiocarbon dating has a bad attitude, but they

are be as right. But you're right it it is ever evolving and they're constantly looking for better ways to pinpoint more accurate timelines on things. So it's not like a job you're going to get in and be like, oh this whole thing again, right, No, no, And it's it's just like they're constantly filling in blanks and stuff like that. It's just it's good work. So, um, what they're looking for the people who do radiocarbon dating is

carbon fourteen, which I said, and that is radiocarbon. It's called that because it's a radioactive form of carbon, that's right, And it's everywhere on Earth. It's just all over the place. It's part of the carbon side goal and it's part of the web of life. But it starts out way up in outer space as cosmic ray, that's right. Should we give the basis definition before we jump to the radio carbon dat Yeah? Yeah, I mean I think like

the most rudimentary definition might help some people out. Um. But like you said, carbon fourteen is everywhere, including inside us, because it's in plants via photosynthesis, and we eat plants, and animals eat plants. Some people eat animals, and because of that, it's kind of in every living thing. Uh.

And carbon fourteen dies away very slowly. And because we know this, because we know it happens predictably, then we can measure that in a sample and then compare it, like I said, to something living and then you do a little math Ipso fact though it's probably an ipso facto is it? Presto change, Yeah, presto change about it being about about it being bon Jovi? What was that that was yours? Was it? Yeah? Man? You came up with that on a carousel at Zoo Atlanta in about

two thousand and twelve. That's right. That's where that's carbon dated too. Yeah, that joke. But because we know that, we can compare it to something that's alive today and then with a little math we can figure out the rough estimate of how old it is. Yeah, that's I mean, that's radio carbon dating in a nutshell for sure. That's right.

But like you said, it starts out as cosmic rays way out in outer space, right, and so a cosmic ray, we're not entirely certain where they come from, but they're super high energy particles, usually like pieces of atoms, that are just shooting towards Earth and through outer space at incredible speeds, and when they encounter the atmosphere, they start

running into the atoms that make up the atmosphere. And because these particles are so high energy, these cosmic rays, when they smack into atoms and other particles in all acules and all that. They just burst them apart, not just burst like an adam into like it's protons and neutrons. It'll tear apart of neutron like like it's nothing. Actually creates other high energy particles like muons, pions, x rays, um, what else? Zaxon's No, that was a video game, was it, Zaxon? Yeah?

With a z uh Yeah. I think it was z A double x O N. I am not familiar with that. Okay, it wasn't a stand up game. Actually it may have been, but I played it on a r because I could see a kid in a Kiss T shirt playing that game stand up in an arcade. Yes, it sounds like that kind of game. That would have been me had I not been deathly afraid of Kiss because they were devil.

They were nights in Satan's service obviously. Yeah. Okay, So all these muons, X rays, pions, all that stuff, there's one other little particle that can be created when a cosmic ray collides with an atom, and that is a neutron, a high energy neutron. Right, that's right. Okay, So what's happening now is a chain reaction because cosmic rays are bombarding the atmosphere, that's right, And uh, what can happen

is they can get really pushy. Uh if a high energy neutron collides with let's say a nitrogen fourteen atom, Yeah, they'll get real pushy and they'll just knock the proton off and move right in there and say this is my house now, right. So what was once a stable atom nitrogen fourteen, which had seven protons and seven neutron, is now an unstable atom with six protons and eight neutrons, and now it's no longer nitrogen fourteen. What you have, fella,

is carbon fourteen. Yes, an unstable meaning radioactive, but not radioactive meaning like scary and dangerous. No, it just means it. It's it's in a higher energy state, and it's temporary.

Eventually wants to decay back into that um nitrogen fourteen stately, Yeah, eventually it's sometimes spontaneously, sometime down the road, that neutron will turn back into a proton, which sounds like magic until you realize that atoms and all of the particles that make up atoms are really just vibrations of energy, and it can temporarily go to a higher energy state or a lower energy state. And that is how something would change from like a high energy neutron back to

a proton. Right. And he said that carbon fourteen is everywhere, which is true, but that doesn't mean there's like tons and tons of it relative to carbon carbon twelve. Yeah, there's a lot more carbon twelve. Right. So carbon twelve is the stable version of carbon, and it's way more abundant than carbon fourteen. Carbon fourteen is kind of like a freak, a monster that gets made accidentally, and it's extremely rare, even though there's a ton of it, but

compared to carbon twelve, it's very rare. Something like one carbon fourteen atom for every trillion carbon atoms. That's that's that's pretty rare. But it also gives us a ratio chuck, And this is a big initial point. Yeah, And like you mentioned before too, or maybe I said it, it's uh, this is part of the carbon cycle. So it's inside all the plants and the animals. Reading the plants were eating plants, some people eat animals, so it's inside all

of us and it's everywhere. Uh. But that ratio is really important because, like we said, it starts to decrease because it craves homeostasis and wants to get back to

its former life. It's a stable particles, a stable boy, stable boy, brush that horse, and it would be it would be an atom because it's going from a carbon fourteen atom to a nitrogen fourteen atom, right, But that ratio is in ard it because as it's you know, dies away, they're going to be fewer and fewer carbon fourteen atoms with that dead organism over time, whereas if

something is alive, it has that steady amount. And that's where the comparison comes in, right, because as far as a plant, or you, or a dog or anything living is concerned, there's no difference whatsoever between a carbon fourteen molecule of carbon dioxide and a carbon twelve molecule of carbon dioxide. Yeah. I mean, it sounds hard to digest because we said it's radioactive, but there really is no

difference as far as we're concerned, right. Um, It basically takes a human scientists to analyze it using an extremely sophisticated machine to be able to tell the difference. So that means that when it does, you know, come down out of the atmosphere, it's spewed out by a volcano or something like that. Um that it just becomes part of the food chain like any other atom of part of carbon that's locked in with oxygen to form carbon dioxide.

So as you're living, like you were saying, you're constantly taking it in, you're constantly eating. It's just a part of life, as carbon fourteen and carbon twelve. Right, But when you die, you stop taking in carbon of all kinds, and all of a sudden that a clock has said because of that decay of carbon fourteen, that's right, And that decay, like we said, it happens spontaneously, and Adam

might suddenly convert from carbon fourteen to nitrogen fourteen. You can't predict when that's going to happen because of the uncertainty. That's part of quantum physics, right, But if you have a large enough sample, then you can start to predict when x number or x percentage of that that sample of carbon fourteen will have spontaneously changed from carbon fourteen to nitrogen fourteen. And that's called the half life. That which is everyone has heard of. That's that's half life.

It's just standard stuff. Yeah, I think everyone has heard of half life, and about the people that know that term don't really fully grasp it. Well, yeah, it's just this the amount of time it takes for half of the radioactive atoms in any given sample to convert back into a stable form. Yeah, that's it. It's pretty easy. Uh. And we know in this case the half life and we'll get to how we figured all this out, but the half life of carbon fourteen is five thousand, seven

hundred and thirty years. Um, if you know you keep going, it goes to a quarter life, then I guess in eight. Yeah, it just keeps going. So like if you have a hundred carbon fourteen atoms, if you come visit it in fifty and thirty years, you're gonna find you a fifty. And if you visit in another thirty years, you're going to have then twelve and a half or thirteen maybe, I don't know. It just keeps going until there's ultimately none. Laughed over a long enought touch of time, which is

with carbon fourteen, like fifty or sixty thousand years. Yeah, I saw sixty thousand mostly, but then I think it starts can get a little hinky at fifty, So fifty to sixty is pretty good, and I think it gets hinky at this point because our because of the equipment we're using to measure it. I think as our equipment gets more and more sensitive, that time will go further and further out, because as long as you have two atoms, you should still be able to measure them, you know,

for sure, or even one. Probably, I'm not going to go out on a limb for that one, but I'm gonna. I'm gonna caveat that with them probably. Okay, Well, let's take a little break here and we're gonna come back here in a second. Talk about the very smart dude who figured all this stuff out quite a few years ago. All right, Chuck, Just to recap real quick, because I think this this episode bears it. Okay, Okay, you've got carbon fourteen. It's part of the food chain. You take

it in as you're living. When you die, you stop taking it in, and so those carbon fourteen adams start to decay, which means that if you compared a dead organism to a living organism, and the ratio of carbon fourteen to carbon twelve in the dead organism compared to the living organism, you be able to tell how long ago the dead organism was alive and taking him more carbon. And that's the basis of radio carbon dating. That's right. So that is Uh, we have Amanda thank from the

University of Chicago name Willard Libby. That's a great name. I heard his name was wild Man or wild Bill, wild Man, Willard Libby, Yeah, because he's just crazy. I guess you must have been a party animal. Who knows. You don't get a nickname like wild Bill for nothing. They don't go around handing those out to just anybody. Yeah, not even just figuring out carbon fourteen dating. You wouldn't get a wild man for that. No, No, like even Chris Farley wasn't called wild Bill. I think Lillard Livy

had a side a side gig. Yeah, you know, but he was the party monster maybe at the University of Chicago in the nineteen forties. Perhaps, so he figured out how carbon fourteen worked and how it could be used to do this before we were even positive science even knew for a fact that there was such a thing as carbon fourteen. That's a pretty impressive, uh. And in fact, it was just a few short years after we had discovered cosmic rays. So he was really on the leading

edge of science. You know he was a wild man, right, He's like, these particles, we're not even sure they exist, but if they do, we could figure out how to use them to date dead organisms. And he won a Nobel Prize in nineteen sixty for this, I think rightfully. So in chemistry, yeah, for sure, even though as we'll see, he got a few things wrong. And the one thing that's kind of tough to wrap your head around here is he and this is it just is what it

is at this point, I think. But he selected nineteen fifty, the year nineteen fifty is year zero for his experimentation, and he compared all the samples against this, and that is still what we do today. That we didn't. We didn't revise a lot of this stuff. It's interesting, no, Like,

they definitely are, like, okay. I think the reason why is because by the time it started to start to become sophisticated and and more refined, so many samples had gone through that it's like, we're just gonna stick with this for now. It's really interesting. So nineteen fifty, when you're radio carbon dating an object, that is year zero, So um, anytime you get a date back, which we'll talk about it's actually saying this is how long before

nineteen fifty this thing was last alive? Right, and we're not talking it just it doesn't have to be like a plant fossil um because we said carbon is in you know, virtually everything. So a leather belt comes from a cow, cow ate the plant um. What else wouldn't plant in ships a pig fabrica. We find poop, of course, old poop, old old alcohol, old beer because of yeast. There are many, many, many things obviously bodies, oats, Yeah,

our pal. Yeah, as long as whatever you are dating was at one point alive, which means it wasn't a rock or a mineral from birth like it's you can date it. You should be able to date as long as it's about fifty or sixty thousand years or younger. Yeah, But there was a problem early on in this process because you needed a lot of this material, uh to

basically destroy to find out how old it is. And people didn't want to give up these gray eight fines, Like they're like, I found a a skull and they're like, well, can we destroy that skull to find out how old it is? And you know they would turn around and say no, it's my skull, right right, And then the radio carbon researchers saying, like I was just asking to

be pleasant, give me that skull. Yeah, but then you would say, no, it's my skull and I'm just happy to call it old right, And WELLRD Libby would step in and just do like a wild man pile driver on the guy with this skull got the name. You would just come in and crush people hiding maybe in another room and back or something, just pound someone to go, he would swarm. Um. But here's the thing. We've gotten

a lot better over time. The equipment has gotten a lot better, more sophisticated, so we don't need that much now. And people are giving up their fines because you can have a little gram bone from the skull and I think everything will be okay. Yeah. And so because of that, like it's gotten way more common to radio carbon dates

stuff I read in the UK. Um they really started dating everything they found because the UK passed a lot of that said, if you're a developer and you turn up any sort of archaeological evidence, I'm like one of your buildings or developments, you have to pay to have

it dated. And so like it started to kind of get the burden for paying for it was shifted to industry, and so it started to really blow up, and that helped kind of push the technology along and help lower the expense and increase the sophistication of the machines that were being used. Yeah, it's pretty pretty neat how that happens. Well, here's what you gotta do if you're gonna start out this process is you've got to really clean your sample

very well. Otherwise it's gonna um you can mess up everything, and not just the test that you're making. If you have what's called a hot sample, which means you didn't clean it well enough for it's contaminated a graham of hot sample, you can destroy a lab basically to the point where they'll just have to shut down for for weeks or even months to get everything right, and everything in there might be destroyed, like, yeah, all the other

samples that may be super valuable my skull. Yeah, you know. Sorry. Um, so it's a big deal if something isn't cleaned right, because it really throws everything off and CARU and everything else. But once you do have it cleaned, um, when you date it, there's a few different methods that you can use, but the one that I saw is the most common is actually turning that carbon based sample into carbon graphite,

like pure carbon. And then you take that little piece of pure carbon that you've just created and you shoot a beam of energy through it, a lot of energy. Yeah, like two million volts, which is a lot, just all once I think they ramp it up, don't they, Yeah, over time, but at some point it's got it's it's

been accelerated to two million volts of energy, okay. And then so once you have this thing basically a particle mini particle accelerators pass through a spectrometer which can actually measure the different masses of the atoms in this beam that you've shot through the graphite. That's right, it's detecting the little bits of carbon. Yeah, that's pretty impressive stuff.

I mean, this is the kind this is the level of technology we're at right now in two thousand nineteen, and this has been around since like the eighties or nineties. Just think of what's coming next. What do they use Before the spectrometer, they used something beta counting, and it was clunky and expensive and not nearly as reliable. But basically what it did was something different where it would sit there and and study a piece of graphite or gas.

They often gasify stuff to pure gas, and then it would just like shoot a beam through and study I think a beam. It would somehow study the sample for days maybe, and it would count the number of atoms that had spontaneously converted from carbon four team new carbon twelve, and then it would do a little mathematic rigamarole and say this is how this is how at this rate of decay, this is how old this organism is. Well, thank goodness, we have the spectrometer now then, because it's

much more precise and it sounds more futuristic too. Yeah, mass pectrometers. So you're gonna shoot this beam, you're gonna throw it in the Wonder machine. Actually not the Wonder machine, We've already taken that. Yeah, it's a thoughtless piece of crap. Fight. Uh. And then you compare that ratio to the again year zero, which is the ratio in which is still a little confusing. Yeah,

it's clunky, It is very clunky. And then that difference, basically, like we've said eight times now, shows how many years have passed to produce the amount of decay in that sample. Right, So if you took like a sample of wood from an old ship, an old boat, you found out right, that's the new right by the way, did you say

route yeah? Um? And you analyze and you found that based on the amount of carbon fourteen in there, it was something like, um, it dated to like eight hundred and forty five b C E. Okay, you'd be like, great, now we know where this ship is from. But if you try to go out and publish a study with that, hopefully your radio carbon colleagues would be like, whoa, whoa, there's a few more steps involved here here, and that's like the most precise radio carbon date anyone would have

ever given. You'll be laughed out of the field if you do this instead. There's a couple of things that you have to do first. So radio carbon dates are given uh as a span of time, a bit of a range, right, so it'll say. And also because it's comparing to it's given not as a date like B C E or a D or C E or anything like that. It's BP before president years before president. So for that piece of wood, say, you would actually get something like twenty seven hundred and fifteen years before present

plus or minus thirty years. So is it always thirty or is it no? No, it can can depend, it can it can range dramatically like Leotsie is there. They have them down to about three hundred or three hundred and fifty years, And you like the shorter the span of time, the plus or minus years or the window of years that you get, um, the less confidence you have.

So maybe you'll have like twenty six percent confidence that it's from you know, uh, eight hundred forty five BC to eight hundred fifty five BC, but you have confidence that there's like this two hundred year span it's somewhere and there. That makes sense because I have a million percent confidence that it's somewhere within the last eighteen million years exactly exactly right. So it just keeps. The larger

the window, the more confident you are. But I mean still you're talking a hundred two hundred years depending on how old the sample is, how good the sample is, so it's still pretty it's pretty um. They can zero it in pretty well. And that sciences job is to not say, well, let's just make a really big range and that will be good enough. They want a zero and as much as possible, Like you know, that's and

still be accurate. So the thing is, though, is if you do the if you do the math, and you say, well, wait a minute, your example, Yeah, fifteen years before present plus or minus thirty years gives you a range of between seven hundred and twenty six and six sixty six BC. But that's not even close to what you said, yeah, which was before right, Yeah, so why wouldn't be in

the sample? Chuck? Because uh, like we said in the very first sentence, radio carbon dating is uh not super I mean, it's accurate on a wide range, but it's a little clunky. It is. Part of it is because there's actual um problems, like known problems built in to the actual process of radio carbon dating and the results that they get back. I'll put that, I'll put that pause. I just had sounded really long in the replay, probably

so I felt like it. But yeah, let's take a break, man, all right, We'll come right back and talk about more science right after this. So I thought this was was this from how stuff works and you in your brain and yeah and a bunch of other places too, and you in your brain. Okay, but there there's an interesting thing to note here, which is science makes a lot of assumptions when it comes to dating stuff. Uh, and

this is the best way to say it. If you find, like if they find like a leather shield that they dig out of an archaeological site, they get super excited and they can date the shield and they can say, or they probably will say, well, whoever this heroic person was in the battlefield died on this around this date, because that's where the shield was dated from. But that is not necessarily true because they're dating the shield from the cow skin that's on the handle, let's say, and

that just says when that cow is alive. Lass has nothing to do with when this person made the shield. How long that leather had been around before they went out onto the battlefield and took an arrow to the forehead. Yeah, maybe they were like super into vintage leather to use on their shield handle here. It's it's sounds ridiculous, but it's also possible. But the thing is is archaeological or archaeology is based on making assumptions and presumptions based on

the context. And it's like, this is totally fine, this is widely accepted. This is not new or scandalous at all, but like that is part of archaeology's job. As you say, here's the context of this find. And based on this radiocarbon date of this, it's a pretty good guess that they killed the cow, made the leather, made the shield, and the guy died probably within a ten fifteen year window. And I mean the idea it would be an even weirder assumption to think that it was an ancient hipster

who collected old hold leathers. Right, check out my new that's right. And then the other part of it too is they also use it to compare to other stuff. Like if they're in a pit filled with other um soldiers of a certain you know, from a certain nation or clan or whatever, um, and they knew of a lost grade, they may have found that if it kind of roughly correlates to the date. They were thinking, Like, there's a lot of a lot of stuff that they

put together. They don't just say, here's what the radio carbon date says, so this is what it is. That's right. So because science does this, Libby was certainly doing this. The wild man was doing this, and he was making assumptions and he was and hey, we're not knocking the guy because he want a Nobel prize for this, but he assumed a couple of things that were not correct. Uh, One of which was he got the half life wrong. Yeah, he said the half life of carbon fourteen was five thousand,

five D sixty eight years. We actually know it's fifty thirty like we said. And he also presumed that carbon fourteen in the atmosphere is very steady over time and it's something we can really depend on, being like they're being a certain amount. And that's not really the case either. No, it's not that second one is a big one. Like the first one. You can just mess around with some math and be like, okay, well this is the actual

half life. Well, but it's interesting. That's what we've had to do because that's another thing we didn't go back and change because it was all done on the basis

of right. Right. So the initial stuff, the initial dates that were done when Libby invented it, were based on a half life from right but from uh, I don't I don't know exactly when they figured it out, but at some point in the ensuing decades they figured out, no, the half life is actually fifty thirty and rather than just go back and re read um uh analyze the

old samples which actually may have been destroyed by this time. Uh, they said, we're just going to stick with this convention and follow it, and we could just do the math and just say, actually, this is the real half life converted to the libyhalf life, and then have a radiocarbon date. Yeah.

But the other thing he got wrong, like you said, is is the bigger problem because it can't just be solved with math, and that is his presumption that uh, carbon fourteen in the upper atmosphere is produced at a steady rate. We know now that they are all kinds of things that can and have affected that rate over the years, everything from ocean currents to super volcanoes, two solar flares, to the Earth's magnetic field. It is fluctuated

a lot over time. Yeah, but I mean from year to year, we're starting to find that it's not at all study. And that's a big one because one of the foundations of radiocarbon dating is this idea that that it's like a reliable clock that just starts clicking backwards. You know, at any point in time, whatever year you come in on you're going to be able to compare it to a modern sample and get a coherent UM

radiocarbon date that will make sense. That's just absolutely not the case because of all of those fluctuations, Right, That's something that this field is definitely grappling with, which uh it will it will be able to overcome and largely has already because they use other types of dating to calibrate their radiocarbon dates. Yeah, which is really cool. We were talking about the um relative dating of carbon fourteen dating.

What they're now trying to do, who not now they've been doing it for a while is absolute dating, like what you're talking about, comparing it to own quantities. And one of those is tree rings. And I'm surprised we've talked about tree rings a little bit here and there, but I wonder if it could be a shorty on its own at least Yeah, maybe more. We'll just start wrapping on it and whether if it turns into a real deal episode we'll go with, we'll just cancel our

dinner plans keep going. But tree ring dating is called dendo chronology counting tree rings, and not all trees have tree rings. Will get to that, which can be a problem, but a lot of them do and some of them grow every year, just like you learned, and everyone probably thinks it's true from like kids science class. It's like once a year a tree has a ring, so if you cut a tree down, you can just count the rings and know how old it is, which is I

mean basically right, depending on the tree is exactly. But here's the thing is, trees absorbed that carbon fourteen just like everything else, but those tree rings don't. Once they have completed a tree ring cycle, that tree ring is essentially dead inside the tree and is not accepting any more carbon fourteen. Yeah, it's like a fossil. It's like if you look at the outside of a tree, that's

the living part. Like as big as a tree is and enormous as it is, the actual living part of it is just this outside veneer and like the leaves and everything. Right, yeah, everything inside is what used to be outside but is now inside because a new ring of growth grew around it. So um, since it's not taking in any more carbon, it's like a snapshot of the carbon fourteen that was in the atmosphere the year

that tree ring grew. Yes, and we know this, and now we have something to compare against those Carbon fourteen data results. Yeah, because if you chop the tree down today, you would say thank you father tree, mother tree, um, for sacrificing your life for for science. That's what you have to say first. Um, And you start counting the

tree rings backwards. If you it to another tree that's much older, but that lived that the lifetime of which overlapped with the tree you just cut down, you can eventually jump over from the tree you just cut down to this older tree and keep counting backwards and then just keep if you find enough old trees, keep leaping from tree to tree, counting tree rings as if it

was one big old tree. That's really cool. It is, and there are very very old trees that do exist on Earth that you can count backwards from over very long spans of time. But you can also use multiple trees. Yeah. And like if you're sitting at home or in your car, thinking, well, why don't they just find the oldest tree and go there, Like you want that overlap because you want a complete

record because stuff you're dating might fall. You know in that that they need everything to fall in that range, right, And so this has been extremely helpful for radio carbon dating because they have managed to compile basically a library of tree ring data UM going back like fourteen thousand, five hundred years. It's amazing. It's called the Holocene tree record, and it's one of the I didn't even know it existed. Now I'm just I love it. Yeah, it's pretty cool.

I want to I like wanta a bound copy of it for the coffee table or something and lay in a hammock in the middle of Pando and read it and read it and be like, oh, look at this year, Pando, what do you think what happened this year? And Panda would hug you. Uh so I was trying to think of something you would do back to Pando, but I would go glow and Panda's leaves. But that feels good. Sure. So there are other places in nature that have the same kind of snapshots. Uh, if you wanted more than

because you need more just than the Holocene tree record. Uh, they can use coral reef because there's clearly carbon in the ocean um still actites and stillagmites, which are called spelio thembs through whenever busts out out at a party, you'll know they're talking about. Yeah, you probably should, because everyone else is just going to be talking about I can never remember which ones are exactly. Oh you mean,

just let me educate you. Goodbye. Uh. They are made of carbon and they are deposited in layers, just like the tree rings in the coral uh. In fact, they have found some in China kind of recently. They go back fifty four thousand years. Yeah. I think they really recently found this so much so that hasn't been like fully vetted, but they were super excited about it. That the idea that it gave a basically a long mineral rich tree ring library of fifty four thousand years of

the carbon fourteen concentrations in the atmosphere. If they if it does pan out, that would be amazing. And what's the deal with the lake in Japan? It reliably puts down a new layer of sediment every six months. That's pretty cool. Yeah. And so they've taken core samples and in these core samples they've turned up like leaves trapped in single layers and something like six hundred and fifty

different spots. So all they have to do is count backwards, find you know, the and they'll know the year that this UM leaf is trapped in and then test the carbon fourteen and the leaf and you've got like a picture right there. And that is called what we'll call a library of atmospheric carbon fourteen concentrations. Yeah, they should have a name. It does. It's called ink COW I

N T C A and UM. There's different programs that you can run all this through like before, back in the forties and fifties, like they were, I guess, using slide rules and stuff like this to come up with these. Now we have basically machine learning algorithms running these these computations for us. But UM, they have programs that use this calibration library to basically say, here's the what the radio harbon date is saying. What does this library of

absolute dates say? And then what they do is they actually, well, the computer I should say, overlaps what's called the wiggles. They hold it up to the light yea, and they find like where these kind of wiggles overlap, which are UM confidence intervals I guess, uh, and where it's most confident that you have a pretty good idea of what the range is for the age of this sample. And that means we know exactly how old everything is always

all right precisely to the day. That is not true because all the things we just mentioned, the spile, thems, the coral, everything has its own individual problems, right. Um. Coral turns out isn't a great material for calibrating this stuff because ocean concentrations of carbon are not the same as in the atmosphere. So that kind of throws it

off right there. It So if you're comparing like something that lived on land to coral in the library in cal library, yeah, it's not gonna it's not gonna calibrate very well. Um. Tree rings are a problem too, because they figured out that depending on the hemisphere that the tree grew in, it will give you a different atmospheric concentration because the southern atmosphere has more oceans and those

oceans absorb more carbon dioxide. So there's actually less carbon fourteen on the land in the southern hemisphere than there is in the northern hemisphere. So if you checked out a water logged oak that grew in Ireland and two c e if you found a cody tree the Cody tree in New Zealand that grew that same year, they would have different radio carbon dates because they have different

carbon radiocarbon concentrations. So it's just there's a lot of things confounding this stuff that's keeping it and being less precise, that's right. And it gets even worse because there have been long stretches of time on Earth in our history where carbon fourteen production really increased every year over you know, hundreds of thousands of years or tens of thousands. Yeah,

well there's stretches that. So all over the radio carbon calendar, there are these things called plateaus, and I think the longest that they've ever found is a few hundred years. When I said tens of thousands, just like a radio carbon date, all right, it feel so bad. They found this thing called the Hallstock plateau, more like the Hallstat disaster. Yeah, that's what some people call them, all right, I'm sure

that's what Willard Libby called that. Sure, But basically there were periods during Earth's history, This one in particular goes from seven sixty four b C where the the production of carbon fourteen in the atmosphere just in priest basically steadily steadily every year, so nothing ever got older relative to new stuff, right, which means that if you radio carbon date something at the in seven sixty b C and something in four twenty BC, they're going to give

you the same exact radio carbon date. Does that make sense for that was your response. Hey, there's people out there thinking it to the Hallstad disaster. All right, Willard Libby would be proud. He was the wild Man. So this is why old this is important. It's not just to put a date on something so we know how old it is and we can just put it down

in a museum or a history book or whatever. Right. Um, it really opens up all of science and all of ancient history to interpretation and kind of rock to the world about a lot of things that we thought were true that are true. Yeah. They call it the radio carbon revolution, and like, well, one good example is in the UK there we talked about Stonehenge. They used to think that Stonehenge was the result of the how do you pronounce that missini myceney? I don't know mycen A.

You'd think I know mice sna. I think it's the mycen A civilization in Greece, But the A and the E on the end. It's got to do something more than like why not just add a Y instead of an e. I'm with you, and you know sometimes you see the A and the E together conjoined, like Ronnie and Donnie Galleon. You know. So what is that? It's its own thing. So we used to think that came from an ancient Greek civilization, but because of radio carbon dating, they said no, no, no, no no, no, this is uh,

we had the age all wrong. And Stonehenge came before that ever, happened before the civilization was even there. So it really helps clear up a picture of everything from Otsy the ice Man to knowing uh that the shroud of Turin was only seven years old. Uh. It so it can confirm things and it can quh other things. Right and then, and the way that they used to do it before was they would just kind of dig

in the earth and turn up artifacts. And because an artifact was closer to the ground than another one, it just meant it was more recent. That's like as precise as they could get. Radio carbon was like, not only are we going to do with that, but get this pal here's a date and a pretty good estimate of a date that this thing existed. That's how much it changed things. They used to be like this is older

than this. Now it's this. Let's see the ice man was running around, you know, in and in doing that, it also changes everything and that they're saying, oh well, Letsie was also ound with tattoos on him that seemed to suggest acupuncture, which apparently they didn't think anymore. But but that changed our idea of how old acupuncture was. And then he had certain tools on him. We didn't know that they were making these tools back then, but now that we've reliably dated Utsie, we know that the

the this, this toolmaking complex is much older. People had professions much sooner than we thought. It just opens up everything when you have a date for one thing. Yeah, the tender rols are far reaching, right, exactly a broad and it happened actually here in the United States to ur in North America. You know, we did a whole

episode on the Clovis Police. Sure the idea that the Clovis people were the first Americans and they came over from crossing over the I guess the bearing Land Bridge when the ice sheet receded, and so Willard Libby did uh a test that showed there's no way that the ice sheet was open anywhere before twelve thousand to five fifteen thousand years ago. So he actually said a baseline,

this is when the earliest people possibly could have been here. Well, we've been finding and radiocarbon dating settlements that are older than that. They found one in Idaho on the Snake River. I can't remember the name of the island. Um, that's like almost sixteen thousand years old, and it shows definitively that since the ice sheet was there, they couldn't have come around the burying language. So now we think the

first Americans came over by boat, all because of radiocarbon dating. Amazing, But we're screwing it all up for the future because of human activity. Um that you know, we're burning a lot of fossil fuels and we were releasing a lot of carbon into the atmosphere, and so much so that that that consistent, previously reliable ratio of carbon twelve to carbon fourteen has been knocked all out of whack because of us. And in the next what uh years, Yeah, thirty to forty years. Uh, we may not be able

to date things accurately using this method anymore. Yeah. Yeah, Because when you know, when they say, well you burn fossil fuels, you release a lot of carbon dioxide. Well, those fuels used to be alive, so they used to have carbon fourteen in them, but they're so old there isn't any carbon fourteen now, it's all just carbon twelve. And we're releasing tons of carbon twelve into the atmosphere

that wouldn't normally be there. That's right. And uh, nuclear tests that we conducted UM had a big actually had the opposite effect. Between nineteen fifty five and nineteen sixty three, the common concentration of carbon fourteen in the atmosphere doubled, almost doubled. Yeah, so there's all screwy now. It is a very screw so much so that now they have

modern samples. They have a beat harvest from the seventies that they used to replace a beat from France from nineteen fifty that they used to be like, this is the baseline now for modern This is what we're reduced to is sampling beats for God's say. That's how much

it screwed things up. But they have figured out how to um use this kind of modern screw nous to also date UM recent remains, which everyone thought was just impossible Um, that you couldn't you couldn't tell when a body lived or died if it were just a you know, a decade or so dead or less. But we have historical records for all this stuff. I know it's a big deal, but like, and we're screwing stuff up to the future. But isn't the the utility of carbon fourteen

dating because it was pre history? Yeah, that that certainly helps. And yeah, I guess you're right that having a record would definitely help quite a bit. And I'm not you know, saying like who cares then? But at least we have that going for us. That's a good point. It'd be like, well, the leather seat from this automobile is the same age as this leather shoe from three thousand years before, which

is which? Um, But yeah, they have figured out how to how to use it for forensics based on your teeth enamel, which are like tree rings, and then based on your soft tissues. But your soft tissues degrade, so they figured out that they can actually test the casings from the larva that eat your soft tissues as you're decomposing.

So the soft tissue is the carbon fourteen in the scenario. Yeah, which you're constantly remaking, and then as you die, it gets it stops being um taken in, and then starts decaying. And as you're being eaten by these you know, bug larva, they shed their casings, and the casings don't degrade. So you can come along and test the casings and they ate your carbon fourteen and you can figure out when that person that body last lived based on the casings

of the bugs that ate it. And in a million years, if I were not to get cremated and they were to bury me into the ground, the only thing that would remain of me are the three titanium screws holding in my three fake teeth. That's Nate. A million years, who'd have thought, Yeah, there he is. Yeah, there's Chuck one. You got anything else? There may be more than that by then too, it might be four or five. Any so, anything else you want to keep going that we can

keep talking about this. I have no dinner plans, Okay, Um, well, I think we're gonna stop with Carbon four team. We don't want to press our luck. It did go pretty well, Chuck, I told you I think so. And since I said it went pretty well, it's time for listener mail all right, and I was preparing for the next episode. Yeah, we got a listener mail for look at me? All right. I'm gonna call this uh soup follow up. If you remember, we talked about cam soup in a previous episode on

what Else Augmented Reality? Right, And I think we were pegged as a progressive guys because you you spoke up first. It's yeah with a name brand. I'm a Campbell's man. Hey, I don't discriminate. I like Campbell's Chunky two. I just kind of went along with it. I didn't want to ruffle any feathers. I didn't speak up, but this is about that. Hey, guys, there are no words to describe how much I enjoy your podcast. I've listened to every single episode and continue to do so each and every week.

Thank you for bringing wonderful science, exploration, for knowledge and laughs to my days. So far, so good. I listened to the latest episode on Augmented Reality while on a plane to Boston, and I could not stop laughing. When you got to a full on sant tangent about can Soup. I thought, this is my moment, this is my chance to write in I've been two Stars struck before. But here we go. I know can Soup all too well. I spent seven years right out of college working for

General Mills. Yes, they make the serial, but they also owned Progresso. I worked in sales, managing our businesses with our East Coast and national accounts. Three years ago, I left General Mills and went to work for Campbell Soup. It's like, I guess, so just outside of Philadelphia. I guess you could say I too have a thing for

Cance Soup. I currently manage our soup and pray go business, one of our largest East Coast grocery chains, and although it doesn't seem complicated, I can tell you a lot of work goes into you enjoying your can of red and white chicken noodle soup. I still love that Campbel's chicken noodle. Oh yeah, it's so good. It's like, how do you mess with a classic like that? Well, but

there's also progressive creamy chicken noodles is the bomb. When you mentioned this episode brought to you by Progresso as a joke, I was just waiting for you to plug that you liked Campbell's as well and even more ha ha. Either way, I'm just glad you both enjoy eating our soups. I would be happy to give you a tour of Campbell's soup HQ if you're ever in Philly. Thanks to the entire team for all you do. You guys are a legend combined into a singular. That's from Kathleen and Kathleen.

Uh no shade to progressive, But I'm a Campbell's man. I eat three soups a day. I eat Campbell's chicken noodle. I ate chicken corn chowder. I don't know. I fare that's and I eat their new England clam chowder. Yeah, that's good. Who who eats Manhattan clam chowder? I don't know, or I'm sorry, man, I had a clam chowder. No one, not even Manahaddan had nights. They're like, get this away, give me the real stuff, give me that creamy goodness.

Do you ever have meatball alphabet? No? I don't know what we're in those meatballs, but I grew up on them, and look at me now. I know. That's all the soups I eat. Though it's weird. I have three soups. Yeah, and you gotta do the chunky stuff Campbell's chunky, I mean become in large cans, is like a hungry man. Well, that's the chicken corn chowder and the I have had that and it's good. Those are chunky. Have you heard the chicken pot pie? No? But I just made a

homemade gluten free chicken pot pie biscuit topped. Well, how do you make a biscuit without gluten? You make it with one to one flower instead of wheat flower? What kind of flower is not wheat flour? What is like the white flower? Do you never luten free pasta? And I mean I've heard of it, I haven't eaten it. It's just made with flower without gluten. It's called one to one is in the ratio. So basically you buy the gluten free flower. Sometimes just rice flour, okay, tapioca,

But have you had chicken flower? I don't think so it's not bad. I mean, I'm not gluten free. I did this so Emily get enjoyed chicken pope pie. But you know, you lay out you make the little chickenscu good little biscuits and you lay them on top of your pot pie, and then you brush it with egg yolk. Nice, and then that Bronze is up to a shiny brown top like people laying on the beach and so good.

That is nice. Man, make a good chicken pop. Have you had it already but had like I haded this past weekend, but I have not had the soup, which is what led me to that danger. It's good, I won't I don't discriminate progressive Campbell's it's all good. Well, Chuck is checking his phone to see what time, and it's so I guess we should probably end this episode. If you want to get in touch a this to offer us a tour of where you work. That's always nice.

Thank you. Um. You can go on to stuff you Should Know dot com, check out our social links, or you can send us an email to stuff Podcasts at I heart radio dot com. Stuff you Should Know is a production of iHeart Radios How stuff Works. For more podcasts for my heart Radio, visit the iHeart Radio app, Apple Podcasts, or wherever you listen to your favorite shows.