How does c 14 dating work

08-Feb-2017 18:33 by 7 Comments

How does c 14 dating work

So calculating the age range of a once-living sample involves measuring the 14C/12C ratio, and using this the known half-life to estimate the length of time since the sample died.That age range is then compared with known 14C/12C ratios from the tree ring/marine record to find the best match, and the result is a calibrated age range you can be 95 per cent sure of.

Radiocarbon may not be perfect, but as any single 30-something can attest, no dating method is.When those speedy protons hit atoms you end up with a few stray neutrons zipping around the place.And when one of those energetic neutrons hits a nitrogen atom, the nitrogen spits out a proton.And nuclear reactions have seen a leap in carbon-14 activity since 1945.Luckily for us we have a record of atmospheric carbon-14 levels for every one of the last 12,000 years.It's been painstakingly pieced together from the carbon content in living and long-dead tree rings. The layer (or ring) directly reflects the carbon-14 content of that year, so a ring that was formed 500 years ago tells us the ratio of carbon-14 to regular carbon-12 (14C/12C) of something that died 500 years ago.

As well as the tree ring record, scientists have used the carbon record from corals to calculate C14/C12 levels right back to 50,000 years ago.

Radiocarbon dating is used to work out the age of things that died up to 50,000 years ago. As far as working out the age of long-dead things goes, carbon has got a few things going for it. The proteins, carbohydrates and fats that make up much of our tissues are all based on carbon.

Everything from the fibres in the Shroud of Turin to Otzi the Iceman has had their birthday determined the carbon-14 way. There's plenty of hydrogen, oxygen and nitrogen in living things too, but carbon's got something none of them do — a radioactive isotope that can take thousands of years to decay.

So the proportion of carbon-14 inside living things is the same as the proportion of carbon-14 in the atmosphere at that time.

But when we stop eating, or when plants stop photosynthesising, our carbon-14 levels no longer get topped up.

(You can read up on radioactivity and isotopes here).

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