Carbon 14 dating 1 | Life on earth and in the universe | Cosmology & Astronomy | Khan Academy
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Carbon 14 Dating 1. Created by Sal Khan.
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Thanks this always bothered me because I always assumed that a small percentage of different carbon Isotopes naturally coexist, like Uranium 235 and 238.
Never heard or made that connection that Carbon-14 only gets formed in the athmosphere and the decay in dead bodies only goes in one direction.
When the video was released I was in grade 2.😂😂 Now I'm in grade 12 watching this video for physics. Isn't time an amazing thing?😂
ឮឲឪឲឪឪឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲកកឲឲឲឲឲឲឲឲឲឲឲឲឲឲឪឲឪឲឲឲឲឪឲឲឮឲ្យឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឪឲឲឪឲឲ្យឲឲឲឲឲឪឲឲ្យឲឲឲឲឲឲឲឲឲឲឲឲឲឲកកឲ្យឲឲឲឲឲឲឲឲឲឲឲឲឪឲឲឪឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឪឲឲឲឲឲឲឲឲឲឲឲឮឲឮឲឪឲ្យឲឲឪឲឲឪឲឲឪឲឲឲឲឮមកឲឲឲឲឲឲឲឲឪឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឪឲឲឪឲឲឲឲឲឲឲឪឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲមកឲឲឱឲឲឪឲឪឲ្យឲឲឲឪឲឲឲឲឲឲឲឲឲឲឲឲឲឲឪឲឲឲឲឲឲឪឲឮឲឲឮឲឲឪឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឮឲឲឲឲឪឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឪឪឲឮឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឪឲឲឲឲឲឲឲឲឲឲឲឲឲឮឲឮឲឮឲឲឲឲឲឲឲឲឲឲឲឲឪឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឪឲឪឲឲឲឪឲឲឲឲឲឲឲឲឪឲឲឮឲឮឲឲឲឲឲឲឲឪឲឲឲឲឲឲឲឲឲឲឲឪឱឲឲឲឲឮឲឮឲឮឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឮឲឲឪឲឲឲឲឲឲឲឲឲឪឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឪឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲមកឲឲឲឲឲឲឲឪឲឲឪឲឮឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឪឲឲឮឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឮឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឪឲឲឲឲឲឲឲឲឲឪឲឲឲឲឲឲឲឲឱឲឪឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឮឲឮឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឪឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲកកឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឪឲឪឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឮឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឮឮឪឲឮឲឲឲឲឲឲឲឲឲឮឪឲឮឲឪឲឲឲឲឲឲឪឪឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឪឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឪឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឮឲឲឲឲឲឲឲឲឲឲឲឲឲឮឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឲឪឲឮឮឲឲឲឲឲឲឲឲឲឲឲឲឲឪឲឲឮឮឲឪឲឲឲឲឲឪឲឲឪឲឲឲឲឲឲឲឲឲឲឲឲឱឪឲឪឮឲឲឲឲឪឲឲឪឲឲឲឲឲឲឲឪឮឲឲឲឮឲឲឪឲឲឲឪឲឲឲឲឲឲឲឲឲឲឮឲឲឲឲឪឲឪឲឲឲឪឲឪឮឲឲឲឲឪឲឲឲឪឲឪឲឪឮឲឲឲឲឲឲឮឮឪឮឲឲឲឮឪឮឲឲឲឲឲឲឲឮឲឲឲឲឲឪឲឪឲឲឲឲឪឪឲឲឪឮឲឲឲ្យឲឮឲឮឲឲឲឲឲឪឲឲឮមកឲឲឮឪឪឲឲឲឲឪឪឲឲឮឲឲឪឲឲឲឲឲឮឪឪឲឲឲឲឪឲឮឪឲឲឲឮឪឲឲឮឲឲឲឪឪឲឪឪឲឲឪឲឮឲឮឲឮឲឮឮឲឮឲឮឲឲឲឲឲឲឲឲឲឲឪឲឲឮឪឲឪឪឪឲឮឲឮឲឲឲឲឲឲឲឲឮឮឲឪឲឲឲឲឲឪឮឲឮឲឮឲឲឮឲឲឲឲឪឲឪឲឪឲឪឪឲឲឲឲឪឲឲឲឮឲឲឲឆាឮឮឲឮឲឲឲឮឲឲឲឲឲឮឲឲឮឲឪមកឲឲឮឲឲឲឮឲឲ្យឪឲឪឲឲឮឪឲឲឪឮឮ
ឲឪឮឲឲឲឲឲឪឲឲឲឲឪឮឲឲឪឲឮឮឲឪឪឲឲឪឲឲឲឮឮឲឮឲឲឲឲឮឲឲឮឲឲឪឲលើឪឪឪឪឲឲឪឪឪឲឲឪឮឪឲឲឲឮឪឪឪឲឪឮឲឲឪឪឲមកឮឲឪឲឲឲឲ្យឪឲឪឮឲឮឲឲឪឪឲឲឮឲឮឲឮឪឮឪឲឪឮឮឪឪឲឲឲ្យឲឲឮឪឲឲឲមកឲឲឪឲឮឪឲឲឲឪឲឲឲឲឮឲឪឪឲឮឲឲឪឲមកឲឪឲឮឲឪឲឲឲឲឲឪឪឲឲឪឲឲឲឲឮឲឪឲឲឮឲឲឮឮឲឲឮមកឲឪឲឪឲឪឲឮឲឪឲឲឲឲឲឪឮឲឲឲឮឪឲឲឲឲ
hi there im from the future, but im watching this in grade 9..
@@sofiadeangelis-qu7ohyou need to get your 'time concept' fixed before your exams.
wdym@@thecatwhocriedmeow
Everything absorbs at about the same concentration as is in the atmosphere.
No, that concentration does not remain constant. But we can identify the changes in concentration throughout time by comparing the carbon dating with other forms of dating techniques that do not use radioactive decay, like dendrochronology, varve chronology, coral dating, etc.
that all makes sense, but what i don't get is how we can know 1/2 of the carbon 14, in a bone, is gone.. how do you know its 1/2 or a 1/4 of the carbon 14 that it started with, you'd have to know the amount it started with to say its 1/2... does everythin absorb a set amount, is carbon 14 created at a constant rate?
That's why we calibrate it against dendrochronology, speleothem dating, coral dating, ice core dating, varve chronology, and others...
Scientists don't assume that the concentration has always been the same. In fact, we know that it hasn't...and we correct for it. In fact, we use that knowledge to learn new things about the atmosphere around that time...like maybe a volcano erupted
The only thing that in my opinion makes C14 dating unreliable past a certain point is the fact that we don't know the earth has made the same amount of C14 in the past as it is now. Atmospheric changes since creation would suggest that C14 formed at a different rate as compared to now therefore making our constant we compare with inaccurate.
@Houston810 Yes but he's talking about the element N, not the substance nitrogen.
@Hooya2 You are right.
i double checked. Its phosphorous, not sulphur
my bad.
thank you for sharing your knowledge with us... appriciate it. well done! sir
@Khan Academy Do you mean that the amound of C-14 is constant (roughly) in all living organisms?
Thank you Sal
thats crazyyy, i just started this unit in school today.. aha youre the best..
also think about doing some genetics in the biology tab?
@AngelKnight85268 Potassium-Argon dating is used for dating things that are millions of years old. It's half life is 1.25 billion years. Sal made a video about it in this playlist.
I suspect that 50,000 years on the cosmic time scale is not even a blip and therefore the amount of radiation won't vary in any significant amount during that time.
To back Hooya2 up, it is true that the rates are not constant but we actually have the ability to find the concentrations of C-14 in the past. We can determine direct ages via ring counting of stalagmites and stalactites. Due to the nature of these formations, they lock away atmosphere in a way that there is no mixing with the current concentrations, Through this we have a record of the concentrations of the past. It is also worth noting that the amounts correlate directly with ice cores.
Great!
@TechiesPlace : it's not just losing a neutron , this particular neutron turn into a proton, thus not affecting the mass of the atom as per defenition ( mass = amount of protons + neutrons in the nucleus ), however changing the nature of the atom dues to the amount of protons now present ( which is determined but the amounts of protons only )
Hope that's clear enough to answer your questions !
@inad316 You are talking about the Arsenic Bacteria found in Mono lake.
It still contains carbon, the element this bacteria replaces in its biochemistry is
Sulphur.
can you please put these on the khan academy app.... or prehaps I missed it. the app in regards to biology sort if ends after ecology
All hot girls are here => twitter.com/b820da66252a48305/status/801992405775826944 Carbon 14 dating 1 Life on earth аand in the universee Cоsmology Astrоnoоmу Кhan Acadеmy
Excellent explanation
before reading my question, please understand that it is neither sarcasm nor confrontation: where in the bible is the date(s) of creation provided?
It isn't. The estimates are primarily made from the geneologies that are provided, and the recorded ages. There have also been some archeological finds with regards to some of the ancient kingdoms.
"1/4 of the Carbon 14 that you would expect to find" I don't know why anyone can't see that as a huge assumption. If you change the amount that you "expect" to find, you change the result in a huge way!
Can someone explain how you measure C-14? Do you compare it with the ratio of N-14? Or do you compare it with the ratio of C-12? Because it seems that measuring the amount of C-14 doesn't do you any good, since obtaining a larger sample of carbon would yield more C-14 atoms.
@siggyboss
It doesn't matter, because it's the ration of C-12 to C-14. If you eat more you eat more of both, so the ratio stays the same.
@AngelKnight85268 The general term is radiometric dating, which is composed of a lot of different methods based on uranium, potassium and carbon (among others i don't remember of course).
Why is this rate so fixed?and why is the amount of c14 in living things fixed too?
most important question...
How is half-life estimated?
+jackp6 T(1/2) = Ln (2)/K
By experiments
By amount of carbon 14 taken in, by item - when it was alive. Test works poorly on "contaminated" samples or items fraudulently manipulated.
I still don't understand it. Isn't the ratio in a body dependant on the ratio in the atmosphere? How do know what the ratio in the atmosphere was when the thing died? You said that Carbon 14 is produced at a constant rate in the atmosphere and it also decays at a constant rate (and I assume it does this also in the atmosphere), so the ratio should change over time, shouldn't it? So, wouldn't the calculation of the time when the organism died be dependant on when the organism died because the ratio would be different at different times?
At 4:17 it is stated that we are mostly made up of Carbon 12 and only a small portion of us is Carbon 14, but at 8:51 the quote was "one-half the Carbon 14 of all the living things you see." My question becomes this: How can you be sure that there was a specific amount of Carbon 14 in the body to begin with? Does age come into play? What if the bone was from a person who was a herbivore or carnivore? Does that make a difference?
I suppose the answer may lie in statistics.
We can imagine taking a mean of a large sample.
The large sample may be that of a fish species living in a given region.
We may measure the proportion Carbon14 / (Carbon14 + Carbon12) in each observation.
Then we can get a mean proportion and may use it to predict how old the predecessor of that fish is whose bones were found below the sea's bed.
@CogitoErgoCogitoSum
-- We assume that all life as about equal C14 concentration even at this very moment - ---
No we don`t really.
C-14 concentrations in marine enviroments are much lower and
not as uniform as in terrestrial enviroments, Consequently it is not
considered useful in dating remains found in marine enviroments.
If an organism have ten C14 atoms at the time of death, will all atoms go for decay or only five of them will go for radioactive decay ( as explained after half life the no of C14 would be five)
Is second assumption is correct then
1. Why only 5 will go for radioactive decay?
2. Which of the 5 atoms will go for radioactive decay, and why?
Thanks for this instructive lesson on Carbon 14 dating.
the next part he alludes to is about exponential decay diff equations...
7:02 "breathing from the atmosphere if you are a plant", does a plant even watch this video?
Plants are living things, even non-living things also watch Khan Academy videos, do you need a proof for this?
2018
So how does C-14 decay back into N-14? That I do not understand.
I wonder if it's still possible to detect carbon-14 in dinosaur bones. Like, does the rate at which carbon-14 slow down inversely exponentially?
How can it be used for extinct organisms because then there wont be any alive one from whom you can compare the the number of C14 atoms please explain this to me.. I wanna know how it can be done for extinct organisms
oh yea. first!! haha
Carbon-12 makes up 99 percent of the carbon in the universe. Carbon-13 makes up about 1 percent. Carbon-14 makes up less than 1 percent. Carbon-12 and carbon-13 are stable, but carbon-14 is unstable. This is fascinating, I love your videos!
7:20 In 2011 physicists at Stanford and Purdue placed the whole theory of "constant radioactive decay rates" under question. They have found in some cases there is fluctuation in the rate of decay. They theorize that the fluctuation is caused by solar neutrinos which until this finding was believed not to interact with anything it came in contact with.
oh and btw great vid!
the video mentions that C-14 gets converted to N-14 by losing a neutron. If the atom loses a neutron how can it still be N-14 and not N-13
It's because it's not really 'losing' but that the neutron becomes a proton and an electron by Beta emission. So, despite losing a neutron, it does get a proton and the count is still then 14.
(C-14: 6 protons and 8 neutrons = 14)
(N-14: 7 protons and 7 neutrons = 14)
The only thing I found missing in the video was that it should be mentioned that Carbon 14 dating can only be used to date stuff back to 50,000 years. It cannot be used to date stuff older than that and certainly not dinosaur bones.
@CogitoErgoCogitoSum
You should pose that question to a nuclear physicist. I believe it involves testing for beta decay on shorter timespans and later extrapolating.
The fact that the predictions it makes are consistent with the concentrations found in progressively deeper fossil remains also helps.
Part 1) Radio carbon dating assumes that the amount of Co14 in the atmosphere has always been the same. But there again, we have no way of verifying that. The fact that insects grew to as much as 8 times their present size indicates that in the past o2 levels and atmosphere pressure (14 N) was indeed much higher. Would not those higher levels have greatly alter the formation of Co14 in the atmosphere and hence the amount or % of Co14 invalidating that dating method?
Part 2) And then there is the amount of cosmic radiation. Again the carbon 14 dating method assumes that the amount of cosmic radiation has remained the same for the past 50,000 years. Just a 10% drop in radiation would result in a sample appearing thousands of years older. Can you guarantee and verify that the cosmic radiation has remained the same?
How did scientists determine that the half life of carbon is roughly 5730 years? How does one go about proving this?
Thanks for explaining. Now I finally know how they are doing C14 dating (;. But I guess few thousand years ago carbon 12 isotope was less common then today.
How the amount of C14 in atmosphere always have been same ?
There must be some reason or else why scientist use it
How about solar activity? Volcanoes? We are talking about tens of thousands of years here. How can we be sure nothing out of the ordinary happened.
@@Ta3iapxHs C 14 is usually created only by cosmic rays in upper atmosphere which then in the form of CO2 is inhaled by organisms. Volcanoes produce CO2 but not C 14 CO2
@@Ta3iapxHs and scientist make sure contaminants don't spoil the dating by various methods. For example if we touch the sample the cells from our finger which contain carbon can hastle the value. So they clean of the phospholipids first.
@@prashanthns54321 For Volcanoes I mean:
If CO2 (in general) is increased in the atmosphere, for example from volcanoes or today's industrial evolution, what happens to the C14 / C12 ratio? Is it the same?
8:24 how do we know the proportion of carbon 12 to 14 was the same in the past as it is now?
isn't N(g) a diatomic gas?
that is so sad, I will not be able to eat anything containing C-14 once I am dead
I'm mostly dating girls...
@Hooya2 but carbon dating cant be right it cant accurately date stone tools!
Warning: That was sarcasm.
that's because stone tools aren't living to begin with. Only works "best" with organic samples.
But, you can only date girls that were once alive :o
The meer rules of phyisic can not stop a might power such as Mr Khan
Why the half life of c14 is 5730yrs
How it has been determined
By the amount of beta decay compared to the amount present - 1 gram-mole contains Avogadro's number of atoms. So when the proportion of decaying atoms is compared to the amount present, you have the decay constant. As decay is exponential, dividing the decay constant into ln(2) gives the half-life. This has been determined many times and compared to tree rings and other historical accurate dates for improved calibration, hence the small changes in the accepted half-life value.
my head hurts
I dated a carbon once, she was clingy.
Part 3) As you can see, it takes a lot of assuming (AKA faith) to hold to the old Earth theory. Interesting, if the history of the world as it is outlined in the bible is true ( massive changes to the atmosphere and the geology at the time of the flood) than the Co14 dating method dos not require any assuming for it to fit perfectly.
100th like
The life of C-14 is 5568 years.
Half-life, not "life".
"or...if you are a plant"
Good ol Sal, being so inclusive of the plant community in the audience
Yawn. Kent Hovind, really?
My fat brother managed to make the best pole dancer there is in my town fall for him as he ran the Cupid Love System (Google it). I wish I was happy for him but I want such a sexy lady to fall for me. I am totally green with envy. Does that mean I’m a horrible person?
Let me guess, the Bible? Get out of here.
KEEP THE F****** DEBATES OFF THE KHAN ACADEMY CHANELL!!!
pretty please
thank you for sharing your knowledge with us... appriciate it. well done! sir