mostly focusing on radio carbon dating.
That's radiocarbon dating and calibration.
And then towards the end, we have a very few slides just to get our heads into age modeling or actually age depth modeling so what do we do, once we have a few ages of deposits.
What should we be thinking of incorporating you know of yeah how to get a model.
model. And then next week we'll be looking at each step models, mostly Bayesian ones we'll start off with a few classical ones, but then move on to Bayesian runs.
And then after that, in the final session will be looking at lead 210 dating.
Using plum, which is Pb210 dating age model, and also running your own course, so that's that will be quite interactive and we'll see where it goes.
Yeah. So the first two sessions, and they are the presentation slides are available on the website that's that Amy has sent around.
And what's in there is the presentation, as PowerPoints, and also as ODP. And there's also the code to our code that you could run.
But we also look at that very same our code in this presentation if it makes sense.
Right.
Okay, So today we'll be talking mostly about ready carbon dating. If your method of dating is not radiocarbon, then this might be a little bit less relevant, but we will still be talking about uncertainties, and that will hopefully be relevant even if
you're not using ready carbon dating.
We'll be talking a little bit on the history of radiocarbon dating, was that i i'd love to dig out about that. I'll try to keep it to a, just a few slides, and also really about assumptions, because there's so many assumptions for ready carbon
dating and there's so many ways in which it can go wrong, and we have to be all aware of. Yeah, where things can go wrong.
Then there's this other thing in depth radiocarbon dates on their own don't really work you need to be calibrated, and we'll be looking at that as well, why we do what we need to do it and how we do the calibration.
And then again at the end of the few slides, just to get our heads into hh Definitely, yeah. So again, we're mixing the PowerPoint slides here with our code.
So if it's possible on your laptop or your computer, and to have both the zoom session open, and an R session. Then, once blue, our code base on your computer, then we can when it appears in resumes so we can try to run that code and see what
happens. Yeah.
I myself, I'm not using our studio. I'm using just a terminal here. And that's the same terminal you would have in the lower left bottom of your studio window.
It's just, I just like to work this way also it takes up less space on my screen than whole our studio window. And then what comes out happens over here.
I hope you can all see this and I can make it bigger if it's all too small.
Okay, so if things go wrong if things don't work, or if I go to slowly move that won't happen or too fast. Just let us know. And yet it will be me nice it'll be looking after the chats, so again if something is unclear.
Let us know will also ask you, I think during the break, or at the end.
Yeah, bits that are clear and big steps that could require more explanation.
Right. So to get started with radiocarbon dating or with any radio metric dating.
We have to look a little bit at predictable periodic table of elements, which we're all familiar with.
And most of these elements actually have at least one stable form of. So yeah, of isotope.
We have for example you have hydrogen, which has just one proton.
And from this one, but some, some different isotopes of the same elements have different weights, of course, for example for hydrogen. If you add a neutral, you get to them.
And if you add two neutrons you get attrition, and different amount of protons, neutrons. Some of those nuclei are very stable perfectly fine.
But some combination are not very stable and those atoms of those isotopes will tend to fall apart after some time, that can be seconds or minutes or years or many, many years.
Yeah.
Now if you plot, and the amount of protons here and have not have neutrons here, and I'm not all the elements and color code, how stable they are. So there's two elements are say here in the middle, or the stables, most stable isotopes.
But towards the edges there will be that there will be, you had the configurations to combinations of protons and neutrons in the nuclear isotopes are in many cases very unstable and over time they will simply decay.
Yeah. And one of those atoms.
One of those isotopes radiocarbon.
So radiocarbon is produced high up in the atmosphere, when there are cosmic rays.
That's arrived on Earth, into the atmosphere that collide with particles, and thereby that produced neutrons, which sometimes crash into nitrogen atoms or 80% or so of the atmosphere is is nitrogen.
And when a neutron collides with nitrogen nitrogen 14, then it becomes suddenly changes into see 14. So a different element.
And it's expels a proton, to see 14 doesn't survive for long. It quickly oxidizes into co2 and becomes part of the carbon cycle to see 14 is an unstable atom, it's over time it will, it will be a point very to decay back into nitrogen again.
And that's what happens at a constant rate.
Yeah. So, as far as we can measure, and as far as we know, these decay rates of the different isotopes are constants.
They're not influenced by their environment.
For example for radio carbon dating for ready government at him, you know that on average, the average lifespan of ready carbon atom is around 8600 years.
plus or minus something. The actual Half Life itself doesn't really matter too much the person. Yeah, we, we do. We used to coloration curve to take into account the half life.
And, what, what, the idea is that you start off with material which has at t zero, it has 100% of radiocarbon. And over time, it will be less and less because of the decay.
Okay.
Good. So, let's play a little bit in our now, and we're going to write some commands for those who haven't written any functions or haven't written like this things in our, you might be perhaps a little bit intimidated by it by it but later on we will
not actually be using this type of commands but just to get our heads into how to work it are, and just to see a half lives, work.
Yeah. So, if you can, if you have your art screen or your studio screen somewhere.
And what we're going to do is we're looking at the first time here, the first blue line, which is very variable called year, why are.
It's just something that I name it you can name it anything, but I decided to call it that. So we're going to create within our available.
Yeah. And this variable, and what it will be. I write a little arrow to the little larger than sign, and a minus sign that little arrow which has.
What's this variable will become.
And what it will make it will make it sequence, and then open brackets and our books in brackets good sequence SEC is one of the many
functions within our, which are very useful, and this one is to make a sequence of values.
And I start here I've started to sequence, Taro, and then have a coma. And then the next option is that I tell it that this sequence which started here, it will increase in steps and the size of the steps by this case is 5730, which is half life of radiocarbon.
And I didn't also tell our that the wanted sequence to be a length, 10, I wanted to have 10 values length, equals 10.
Yes Oh I know all the information, and that close the bracket.
Close to sec function.
And I press enter. Well, nothing happened. That's because there was no error. It's our deeds, but it was told to do it made function yr year, which contains 10 values, but it doesn't really spit them out.
It just says okay, that's what I did. Now, Did you all managed to get that in your session.
Any problems.
No.
Good.
Okay, so what are you again. Now what you can now do is to type yr to ask our to show us what is in the variable. Yeah, so we just type the name of variable and press Enter.
And I notice he has a list of 10 values starting with zero than 5500 730 11,004 60. And so and so and so on until we reach around 50,000.
Yeah. So these are the 10 periods in time to 10 half lives of radiocarbon, in this case, yeah.
Now, we're already said that, at t zero. 100% is available. Yeah, but a half life is. So if you have a population of carbon, she 14 atoms. And if it's half live is 5730 years.
If you start off with 1000 items of see 14.
After one half life, half of the left. Yeah. And if you add another half life, half definitely left, etc.
So definitely trying to do now. So, we have this half life, 0.5.
And if we just put 0.5, and ask what it is, it's 0.5 50%. Yeah.
So, 0.5, if we just used s zero time so if you do, to the power of 0.5, a little funny, but another column in English.
We call them roof in Dutch.
0.5, to the power of zero, and then press Enter becomes one. So at t zero with a half life.
Zero half lives, you have 100% left.
Now if we say one thing with RB your command window, if you use your up arrow on your keyboard. You can retrieve previous detect commands, and that's very useful because if you're like me, you're lazy with typing and you can avoid typing, that's that's
very useful.
So getting back to previous command, 0.5, to the power of zero. And we just delete the zero, and replace it with one.
Yeah, 0.5 to the power of one.
And that's 0.5 so after half up to one half life, half is left, never go back again and change, replace to one by two.
Show up to half lives, half of half left.
And after 3.2 12 and a half percent is left, etc. So we can make it a bit faster by just typing and just give him another name to some variable, little arrow, an essay point five to the power of, 01234 etc.
We just simply open the brackets, and then give the old numbers that were interested in, in our, the numbers, zero to nine, and in our speak that zero.
The dogs are what's called him the colon to nine, and then close to brackets.
Yeah.
Numbers Enter. And again, we don't see anything, but if you can
And again, we don't see anything, but if you can ask our to show what half lives is.
Then we see it is, it starts off at one, then becomes half an hour and a half of a half of a half half at each rep, all the way to reach and very low numbers.
Okay.
Now, in order to see them together, and the year and a half lives, you can combine them together. So she bind, which is bind columns band ferret variables together as columns.
So we can have first year.
And then the next next value I want to combine as a column is half lives.
One other thing, if you want to avoid type into much. You can type a few initial letters of have your variable, and then use tab to fill in the rest.
That's a very handy trick in our.
So we have see bind year and half lives be closed bracket.
And then we end up with a list with two columns.
Now we have, say, a year zero, we have a half life of one at five 730 we have had over, 1.5, etc cheater cheater.
Now I'm just going to go back to that command, again, because I want to present the half life, not as between one and zero but as percent. So I just multiply half lives by 100.
So 100 times, half lives.
And now we end up with these columns, yet year zero we have 100%.
Five 730, or 50%, etc etc. So, after around 10 half lives mirror at 5001. Well, 51,570, then we're only left, we only have say point 2% of radiocarbon left.
And that's really more or less the limits of what we can take.
Okay.
I hope that's that went fine.
Right.
So if we use this distribution equation and we can then see how over time. As time passes, it will be less and less radiocarbon left.
Yeah.
In this animation here. Black is carbon, and most of carbon. So, carbon has three natural isotopes, see 12, which most of carbon is see 12 99%.
See 14 is only 1%, and see 14 is a million of a millions of each particle. So very, very tiny trace amounts.
But it is a month can still be measured which will come back to later.
And over time, it will be less and less radiocarbon left.
But we can still measure it.
But if you have a problem for example with some little bit of contamination with modern carbon, especially for old dates, then that's going to be very problematic.
Of course if you add 10 particles to this final bit and you'll get a totally wrong answer.
It's just do that one again.
So for material back to the Holocene so over the Holocene or back to 20 30,000 years ago so really really good technique. And with carriers can also be used further back.
Once we always have to be mindful of contamination problems,
these animations that can also be downloaded from my website, and I've also added some URLs, you can also download it from download them from Vimeo or YouTube, if you want to hear free to use them for any teaching or anything.
Yeah, right. So what happens in the carbon cycle we've got these cosmic rays that collide high up in the atmosphere with nitrogen, and then produce see 14 and 14 then oxidizes to co2.
And it becomes part of the carbon cycle. Yeah, so co2 goes along with all the other co2, most of which you see 12 year to a little bit of C 13 co2, and def co2 is then part of the carbon cycle it gets into the ocean and photosynthesis is taken up by plants,
and most of the co2 to take this taken up by plants which he 12 to two, a little bit will be c 13 this year two and a tiny bit will receive 14, co2, and then animals will graze the plants and will also, more or less, get that same amount, the same ratio
of see 14, to 12, to see 12.
When they're alive, plants and animals, see 14 will decay.
But animals are constantly topping up their see 14 because they're still eating the plants and plant also come to constantly top up their CEO, Darren see 14 through photosynthesis.
But the moments, that's that metabolism stops when animals die, then this clock starts ticking. Yeah, then there see 14 is any DKC 14 is not replenished anymore.
And we've got them this decaying concentration of radiocarbon over time.
And that's what we measure in order to estimate your radiocarbon age.
Okay.
Right. So, this has been done since the late 1940s, and there were lots of people working on, on nuclear physics, including Richard Levy, who in the late 1940s predicted that there should be radiocarbon produced high up in the atmosphere that just simply
had no way of actually measuring it yet,
And I predicted status UBC 14 and if the receive 14.
It couldn't possibly also be useful for useful for radiocarbon dating.
So he published papers in 1949, saying that, okay, there is this thing called see 14. And then, in 1951, I think he published the first paper with a list of radiocarbon dates.
It's a paper and science, and where we'll come to that later.
Their material of known calendar age, the red carpet construction in debt material was measured, and that way to check if that really carbonated actually worked.
So the original really carbon way to measure rate of carbon was to put it into a flask, as a gas, and then wait wait for days, weeks, and the few radiocarbon particles in the flask in the co2 would overtime decay.
And whenever it decayed, that would be that that event, we can be measured.
So you needed to have your something if you had to have a large large samples and not long long counting times.
Now that's most of the labs No, don't do that approach anymore but instead we measure the particles themselves, not a DK events but the particles, themselves, and that is done in an AMS, here's our previous AMS, which was dismantled in December last year
and now we have a new shiny iron plus. Look at us, which is a web two and a half to three and a half meters.
Size machine, very small and, yeah, very easy, easy to maintain.
We hope I won't get into much detail there now.
What this machine does a sample output in here, and then the carbon particles are accelerated they're put into a beam, and they're there through electrical currents they're going to be there charged and going to very high speeds.
And then at several points, there are magnets, very strong methods and that's the flex the particles.
You can see this year so partners could come in as a beam with a mix of see 1213 and see 14.
But the magnet bends them. Yeah. And when are bent heavier particles Lexi 14 will take a different route, than lighter particles Lexi 14 and see 12, so he separates the beams of C 1213, and 14, and then measure at the end of each beam of each step beam
you measure how many particles arrive. And that way we can calculate how many ready carbon atoms are still left in a, in a sample, or the ratio.
Alright.
But say, originally, this was done through DK counting. And so in 1951 under the levy published this first list of dates in science. I think it's really fascinating paper to read if you if you can find it.
It's, it's online available online in science, and those guys they went to the contact people in different media and asked for material have known historical age.
For example, here in light blue. There are several addiction coffins and older pieces of food from from coffins from boats that are otherwise dated through historical information to the very precisely that sometimes to the very year that could say, what
the tender age of that material is should be also used dental dated priests supplied by Douglas, I think.
And those were general data so tree trees deposit yearly rings and those earrings for counter back, and it up a calendar ages could be obtained.
Also they had some, they went to, they asked from researchers over here in Europe, and if they could supply some organic material from known archaeological sites, for example, hazelnuts, from a site that was, otherwise known to be of a certain times pen,
like early Holocene there the uncertainties are quite large, of the timing, but say that could get some estimate.
Now if you didn't measure it already carbon, age, in each of those samples. You can see there's a.
Well, there's a quite a good relation correlation between the known tender age, and the radiocarbon age that they measured in 1951.
And that dashed line here is the one to one line so if radiocarbon age for exactly the same as consideration that should be on that line. They're not exactly on it so there's.
Well there's some dates that are way, way, way too young or too old.
But generally, there is quite a good relationship between the two.
I've put into this graph as well. The current most recent calibration Curve, Curve, which gives for each kind of a calendar year, the corresponding radiocarbon year for the northern hemisphere atmosphere.
And you see is quite a quite a good relationship between the original very first dates and and current knowledge of how radiocarbon age and calendar age coexist.
Okay.
Right.
So, Let's go to the assumptions, you just check here.
Yeah. Right on time. So let's talk about assumptions involved in ready carbon dating.
The first one is about that we're assuming is that the comes the atmospheric really common levels over time has have remained constant. Yeah. So again, simply us at t zero, as are the concentrations, at t zero have been constant I don't not changing over
time. As we will see this assumption does not hold at all. So we need to correct for this temporal changes in atmospheric carbon levels.
The second assumption is about well mixed carbon reservoirs, and in some cases that is also not this assumption as a Muslim not met, and also that the target event is stated, which is sometimes the case but also not always the case will look at each of
them.
Okay. Right. So, and Libby already showed that that's ready Kevin ages agree more or less with calendar ages, but we needed more information yeah so since the 1950s.
Many people many labs have been continuously trying to produce more values to put in that graph that relates counter age to radiocarbon age, and most useful have been trees.
So, Denver data would say blocks of 10 to 20 years, which were then have known exactly known calendar age, and then those blocks were then radiocarbon dated to see how ready carbon age and gender, age, compare.
Yeah.
And what we found is that, that there's not a clear 100% one to one relation but there's actually several wiggles in this curve that relates calendar year to write a cabin year.
And these vehicles can be seen here, if we just look at them in top 20. So the latest northern hemisphere calibration curves. Over the past thousand years.
So welcome you, working here and cold, yes VP, which is Canada years before the present and the present here is 1950.
This is the confusing. 1950 seems like a strange year to call the present, But actually we just saw that the very first radiocarbon dates different measures were measured in 1950.
So that's 1950 is actually a nice period, to, to, to keep us an anchor the red carpet community decided to get to stick with that dates. At 1950 s t zero, other communities have decided differently for example ice cores, often measured as years before
the year 2000 ad 2000 and say led to 10 dating expresses everything against the year in which it was measured English the lead to 10 was measured.
So it's quite important to be aware of that, those distinctions of what two different time skills are.
Anyway, and we see here many different data sets of trees and ever measured trees from all over the world, mostly the northern hemisphere, but yeah, and also New Zealand.
So trees were taken from different places, and were dated, and then also ready carbon dated in a number of different clubs. So, the black ones here is trees from Seattle measured in Seattle.
Then in red, we've got the herb See, but those are oaks Irish folks, measured in Belfast.
Then we've got in green, some trees from my cattle in New Zealand, and some other trees. Yeah. And, including some new ones in Tokyo, and, and, on our McAdams food.
I hope. Okay, nevermind.
And so, independent scientists, a little bit of an offset with what we see happening in Europe, and that's something that we're actively looking at.
So, although. Originally, the trees were measured same blocks of 10 to 20 years because we needed depth amount of wood.
In order to get sufficient amount to radiocarbon date with TK counting.
Now what are the reasons, as we can actually get tiny slivers of Route just one year of wood.
So recently, many labs have been working on getting yearly dates.
I'm not picking our technological she will get angry.
Yes.
Alright. So, you see this is the data sets, day, more or less agree there's a bit of scatter around the main the main curve, and is disturbed the integral 20 curve, which is.
And, yes, an approach to get all those data sets together and try to get an average an estimate of what the rate of current age has been over time.
Okay.
Right.
And so this is just the most reason, thousand years, but you can go back further in time. So, the three rings we can get reasonably accurate and reliable data sets, all the way back to 14,000 Kelby P.
Beyond that, in the Ice Age they're simply not enough. Trees left to reliably to Denver dating, and the trees are probably very stressed. And so the rings are not very, Very easily replicated.
But say for 14,000, Calvin be up to zero Kelly p we've got a very well replicated record for the coloration curves and yeah it's.
Many of just vehicles are very well replicated.
There's some issues in that some years have seen events have enormous peaks in radiocarbon, and with the Intel 20 curvy tried to have described so like stable enough but also sensitive enough to be able to pick up those peaks as well.
Okay.
So, there's also another curve for the southern hemisphere, which is partly based on data for some southern hemisphere, and then also based on data from northern hemisphere, with an offset applied to it.
And then we also have the marine curve which just saying, with this data is then gone through a marine model, which tries to express what happens in the marine environment, which radiocarbon ages.
Okay so that goes back to 14,000 years.
But we want to go further back yeah because you can date back to say, 50,000 years 55.
And lucky enough we can do it now so over the past decade or so we've been able to expand the Innovation Group from what used to be 14,000 to 26,000 years ago and now and then to 50,000 years ago, and now to 55,000 years ago.
And we do that by having more tree rings of floating rings, so floating dead set that are not linked precisely, and exactly to two calendar years.
Valve records. We say, annual eliminations, and within their have material that can be ready carbon date is one of the sites so you get so in Japan with his beautiful nominations and nice macro fossils of leaves that can be dated and resulting quite good
credit card. Although it's quite a bit of scatter.
And we've also the Kerry echo basin of offshore Venezuela, which also has partly barfed records, then we've also other records like studio films and corals, that can be used as well, so they can be uranium for him data's.
So we have an independent timescale and also retired data based on that so you can then get you can extend our calibration curve further back in time, for example here between 30,040 thousand years ago.
We've got a whole range of data sets.
The black one here is Chris journeys.
Cody data set, which was published at his 42 KA record in science, a few months ago.
And then we also have Should we get so in red, which is just Japanese vironment lake.
And you see quite a bit of scatter of those dates that especially have to get so then the Korea co basin is in green.
And then we've got in blue some curls.
And, yeah, and terraces yet mostly curls and further back we go to less material we have and the more scatter of the dates, until we reach around 55,000 years ago were beyond that, it's still not possible to obtain a good estimate of regulating carbon
ages for you for those kind of the years.
Right.
So if we don't extend the whole curved and this is the current interval 20 coloration curve.
Reading trumpets out here at the end. Very things are becoming very interesting.
Okay.
Right. So, what is causing these fluctuations so these these vehicles in a calibration curve.
So if we look at say the past hundred years or so since at 1900.
And over time, and we've got lower and lower slightly gradually lowering constraints on Friday carbon in the atmosphere, up to around 1950. That's because at that time, and still there.
There's lots of fossil fuels, which are burned and causing lots of co2 to come up in the atmosphere, from carbon deposited millions of years ago. And it's just devoid of sea 14, and therefore we are diluting the sea 14 in the atmosphere, so you can see,
say the greenhouse effect happening, more or less, perfectly if the greenhouse effect or off the co2 emission.
Luckily enough, then recently gets to very high concentrations and that is because of nuclear bombs, which were then set off in the 1950s and especially in 1960s.
got almost a doubling of radiocarbon concentration in the atmosphere. Until the early 1960s 1964 So when a moratorium was placed on atmospheric nuclear tests.
And since then, concentrations of radiocarbon has gradually come down again.
If we look at that in radiocarbon years.
We see here again we've got include the calibration curve in 20.
And since 1900 we've got like a steady increase in radiocarbon years because it will get older older and older years, even though we go to a younger ages.
This is years ad. If you go to even though we go to younger ages in Canada as we get older and radiocarbon ages, because of this dilution effects.
By emission of old carbon into the atmosphere.
And then we've got a sudden.
Seven input of lots of radio carbon into the atmosphere, new radiocarbon, of course, of nuclear explosions.
And it's such an increase that we can't actually use the same access to see the blue and the green.
So what's the green dead set here the postponed date set is we have to plot it on a totally different.
Ready carbon timescale and become, we have to prove to be get very modern year so say minus 5000.
And since the moratorium and then we get back to more. Yeah, more reason to edge we're getting back to zero again.
Am I lacking a pitch, or is it okay.
I think you're dead on my end sorry.
I think you're fine.
Okay, I'm gonna put stuff in the chat. Also, okay because I see myself lagging a bit, but I don't know if I can just buy my system, and I ask a question on the, the minus five.
What are the units of that minus 5000 radiocarbon years that's year. Wow. Yeah. Hi, I'm Leslie will will work on that in our just later on. So, if you get to post boom date so it's generally not expressed as ready carbon years anymore it's expressed as
fraction modern carbon, or the MC percent modern carbon.
But if you express it as ready carbon yes you get to minus 5000 ridiculous, but that's that's what happens.
Because of this enormous nourishment, compared to 1950.
Alright, so in different parts of earth you will see different expressions of this peak in radiocarbon, the bomb peak, and its most expressive the northern hemisphere where there were more tests, I think, and also more landmass, whereas in the southern
hemisphere, which is yellow here. There's more ocean so more of the carbon, see 14 could be if taken up and absorbed by the oceans cosi less of a peak there.
And then very oceanic sighs you very little peak
is our question.
Okay.
Alright so what we can do now in our instead of writing our own teach we can use functions of existing.
Our packages.
But in order to do so, we first have to load that package.
So just a new package that I've wrote over the past year or so, which is Intel.
Originally it was just a package to contain all the coloration curves.
But now I've also added some functions to also blocks the data which I think it's fun.
So we load the internal code by typing require account. So, to load the code you could either use require or library.
And I tend to use require because it types better for me. And I typed our EQ, and then the use tab to fill out that command.
And then I opened my brackets, and I type in.
Cal with capital I, capital C,
and a close bracket.
Echo.
Okay, so internet Press Enter the code.
No, and then the next line I want to do you, so if you can if you can try to go along with it. With this, we type in Cal in all lowercase dot data.
And that's a function to plot the internal data, and we want it from zero, Cal BP to 1000.
And then we press Enter.
And then we end up with this graph here, which you already saw in the presentation. Yeah.
So we can also adapt it to be between zero and 100, for example, and then you can see all the detail of the different data sets that go into producing that's blue curve.
Yeah.
You can also go to between so for two older ages between 30,033 and 14,000.
This year.
Yes.
And we can also draw the curve itself, which is vertical draw that draw dots seeker coloration curve.
You can just open bracket close bracket and Damn you have to curve here.
And we can also go for different parts of the curve.
For example, but saying drove drove curve between 1815 and 2020.
But that's not engaged LBP, we are saying that this is actually in years BC ad.
So we have to tell.
That's we're wanting to work with on the ABC ad scale in this case.
Now close bracket.
Yes.
Okay. So, here we have been integral 20 curve. Yeah.
Okay. And I think in five minutes I'll just have to go and feed her It might also be good for us to have a short break.
And so here we have just internal transfer, we can add.
We can add another curfew it's by tapping cc to to sort of second calibration curve.
And we're using the post boom curve here for the northern hemisphere zone one.
So we add.
You go back to the previous command and we add an option, cc two equals quotation mark and age, one another quotation mark
and gives us this. Yeah, so we hear the both curves on the same.
Pretty carbon scale.
You can see how how enormous changes in postgame curve are Yeah, compared to the pre, boom, where the construction, changing the construction for having very limited compared to what we have seen since 1950.
If we want to place them on two different access, then we can simply add and add dots.
Y axis equals true, true or 250.
It's a true, or 250. And now we have to own to access, so we can see a bit more detail in but either dataset.
Thank you.
Okay.
I hope that works that you were able to produce some of these clubs as well.
Yep.
Okay.
Now, let's do a few more minutes just looking at reasons of why we're in a cabin crustaceans have changed in the atmosphere.
So we already went through, say the past 6070 years where we've got human made changes in our concentration but there's also natural changes, and most of that has to do with changes in the geomagnetic field.
So, in this graph here we see the earth, and around it is is magnetic field. And it's a combination of the solar magnetic field which are these vertical lines here.
And geomagnetic field, which are these lines, and together they make this shield around, around Earth, which is quite effective against cosmic rays entering the earth and producing rate of carbon is quite quite effective.
But this shields this new medical field, and also the shoulder magnetic field is not entirely constant over time and sometimes, when it changes, it will cause change in the effectiveness of this shielding.
And that will then cause either more or fewer cosmic rays, to be able to enter the earth, and produce radiocarbon.
Okay.
So if you look at for example here is a graph of the amount of see 14 produced per centimeter square per second.
Against latitude of the Earth from polar regions to equator and then again the other polar region. And then the altitude, from 10 to 20 to 30 kilometer height.
You can see that in the equator where the here magnetic field is very strong. And there's very few cosmic rays that's can enter and produce ready carbon atoms, but at the polls, where the humid weather matter the field diverges.
There, they're much more chance for cosmic rays to enter and produce radiocarbon, especially so when the sun is at some sense but minimum, which is then, which then causes less solar magnetic magnetism.
And then, less effective shield against cosmic rays are more closer grace can enter, and more radiocarbon can be produced, and during the solar maximum, there's less of that produced.
Yeah.
And there's also the do magnetic say the Earth's magnetic field which also changes over a long time skills and, and also sometimes within a few hundred years.
And generally, this dramatic changes are followed quite well by radiocarbon concentrations.
Okay.
Good.
And I think if you do want to have a break now, and to feed the cat and be back.
Excellent. Okay, I'll stop sharing the screen then for now.
And, and thanks and some of us have this is Amy as some of you saw the chat. I'm having some my zoom is freaking out in a way that I have never seen before.
And so I'm gonna, I'm going to end the meeting and restart my computer and then come back so I apologize, but you'll need to login again give me probably five minutes which is about the period of our break.
Hey.
Thanks, Amy.
And I will also put up a poll about the pace of the course at that time when I come back.
Okay. Thanks.
Have a good roommate six or seven after the hour.