Carbon 14 dating 1 | Life on earth and in the universe | Cosmology & Astronomy | Khan Academy

Carbon 14 Dating 1. Created by Sal Khan.

Cosmology & Astronomy on Khan Academy: The Earth is huge, but it is tiny compared to the Sun (which is super huge). But the Sun is tiny compared to the solar system which is tiny compared to the distance to the next star. Oh, did we mention that there are over 100 billion stars in our galaxy (which is about 100,000 light years in diameter) which is one of hundreds of billions of galaxies in just the observable universe (which might be infinite for all we know). Don't feel small. We find it liberating. Your everyday human stresses are nothing compared to this enormity that we are a part of. Enjoy the fact that we get to be part of this vastness!

About Khan Academy: Khan Academy offers practice exercises, instructional videos, and a personalized learning dashboard that empower learners to study at their own pace in and outside of the classroom. We tackle math, science, computer programming, history, art history, economics, and more. Our math missions guide learners from kindergarten to calculus using state-of-the-art, adaptive technology that identifies strengths and learning gaps. We've also partnered with institutions like NASA, The Museum of Modern Art, The California Academy of Sciences, and MIT to offer specialized content.

For free. For everyone. Forever. #YouCanLearnAnything

[Innengelaender]

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.

[amaizenblue]

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.

[amaizenblue]

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

[sugam_]

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?😂

[thadhaines]

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.

[djaste]

thank you for sharing your knowledge with us... appriciate it. well done! sir

[jrsoccer]

thats crazyyy, i just started this unit in school today.. aha youre the best..
also think about doing some genetics in the biology tab?

[MrAnderson]

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?

[nivinajith]

@Khan Academy Do you mean that the amound of C-14 is constant (roughly) in all living organisms?

[GeologyJack]

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.

[csl]

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

[noxure]

@Houston810 Yes but he's talking about the element N, not the substance nitrogen.

[vicksoma]

@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.

[AcanLord]

@Hooya2 You are right.
i double checked. Its phosphorous, not sulphur
my bad.

[SnoopyDoofie]

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.

[animalsfeelpain]

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.

[eggie]

the next part he alludes to is about exponential decay diff equations...

[AcanLord]

@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.

[idave]

Thanks for this instructive lesson on Carbon 14 dating.

[Rendall]

@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 !