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I am a homeschooling parent, so pardon me asking stupid questions. Everywhere I read, it is said carbon based lifeforms eat carbon and after their death that atom starts a decay.

But what I cannot understand, we dont eat or work with food at atomic levels. Yes, life forms breaks down molecules from food and use them as they wish. But that chemical process does not effect the atom structure. I dont think any life form has capacity or energy to break down atoms.

So if one atom of C14 was having a decay already before we ate it, it keeps having it while it gets digested and goes on in the same way if life is alive or dead. If another C14 was not having a decay, then it starting a decay has nothing to with the life form is alive or dead.

As Dr. Manhattan(Watchmen 2009) said atoms dont care if you are alive or dead. They stayed there at the same place before and after.

So how can a lifeform have any effect in the C14 decay at all?

Got some good answers, so I clarifying my questions:

How can we be sure that we have eaten only fresh out of factory C14? It may be already decayed by hundred or thousand of years when we eat it. It applies to all living beings. If there is fresh C14 in the air, there is also decaying levels of C14 as old as 50K years. So when you check my c14 count, you would have a wrong answer of when I died cause origin of C14 was even before I was my great grandfather was.

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You are correct in the fact carbon-14 does not care whether or not a life form is alive; however, this is irrelevant in the case of carbon dating. You may be familiar with the carbon cycle, which is, in a nutshell, the recycling of carbon through carbon dioxide. Plants are, of course, constantly using carbon dioxide from the atmosphere to generate large bio molecules that we can eat. We are also constantly recycling the carbon, ingesting it in the form of food, and exhaling it in the form of carbon dioxide, so it is clear that living organisms are constantly replacing their "old" carbon from carbon from atmospheric carbon dioxide. The key factor to carbon dating is that atmospheric carbon dioxide has a higher percentage of Carbon-14. This is caused by high energy cosmic rays which convert nitrogen-14 (the most abundant isotope of nitrogen) into carbon-14 nuclei, which in turn result in a greater percentage of our carbon content being carbon-14. When we die, we are no longer replenishing our carbon from the atmosphere (higher carbon-14 content due to cosmic rays), so the carbon-14 will gradually decay into more stable nuclei, leaving a lower percentage of carbon-14 in our remains. By using the half-life of carbon-14 nuclei, we are able to calculate the time when a certain living organism was no longer exposed to our atmosphere's high concentration of carbon-14. As a side note, carbon-14 dating is fairly accurate because the relative concentration of carbon-14 has remained constant in our atmosphere.

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  • $\begingroup$ How can we be sure that we have eaten only fresh out of factory C14? It may be already decayed by hundred or thousand of years when we eat it.It applies to all living beings. If there is fresh C14 in the air, there is also decaying levels of C14 as old as 50K years. So when you check my c14 count, you would have a wrong answer of when I died cause origin of C14 was even before I was my great grandfather was. $\endgroup$ – thevikas Nov 20 '19 at 4:43
  • $\begingroup$ We can't and aren't. We eat (and therefore our bodies contain) a mixture of fresh-out-of-factory C14, and that produced 50 years ago, and that produced 100 years ago, and so on. Dead guys don't eat, and that's what makes the difference. $\endgroup$ – Ivan Neretin Nov 20 '19 at 5:26
  • $\begingroup$ Supposed I had eaten only carrots and lots of them. All those carrots had atoms of C14 produced in the air 12000 years ago. When I die tomorrow, and you find c14, wont you see stale c14 atoms and assume I died 12000 years ago? $\endgroup$ – thevikas Nov 20 '19 at 6:23
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    $\begingroup$ By other words, radiocarbon dating does not measure,how old 14C atoms are,but calculates what time it would take to reach the measured 14C/12C ratio. $\endgroup$ – Poutnik Nov 20 '19 at 8:35
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    $\begingroup$ This ratio of carbon-14 to carbon-12 is very accurate among all living organisms. The diet does not matter. All that matters is that all of our food contains approximately the same ratio of carbon-14 to carbon -12. All of the carbon you ingest comes from the food we eat, which was just recently synthesized by a plant from atmospheric carbon dioxide. Do not get caught up on the age of organisms, diet, etc. All of that is irrelevant. Every living thing on the Earth will recycle a fixed ratio of carbon-12 and carbon-14 until they die, and from then on, the ratio will start to change. $\endgroup$ – Eli Jones Nov 20 '19 at 23:02
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Carbon-14 decays no matter what the chemistry. New carbon-14 is made in the atmosphere when nitrogen-14 is hit by cosmic radiation replenishing carbon-14.

Living organisms continuously exchange carbon with the atmosphere. Carbon in fossils and in rocks does not.

That’s why carbon dating gives the time of death rather than the time of birth but with lifespans much shorter than the age of fossils, this differences is rarely significant.

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