How carbon 14 dating works

27-Apr-2014 23:36

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.

For a rare event it happens pretty damn often — one million carbon-14 atoms in your body decay into nitrogen every minute!

But don't panic — of the 800,000,000,000,000,000,000,000,000 carbon atoms in every one of us, about 800,000,000,000,000 are carbon-14, so we've got a few to spare.

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.

And the longer dead things lie around, the lower the carbon-14 levels get.It's not that the radioactive carbon in air or food doesn't decay, it does.But something else is going on that keeps producing new carbon-14 — otherwise it would have all turned to nitrogen millions of years ago.But old age isn't the only thing that affects the accuracy of carbon dating.

The level of radiocarbon in the atmosphere has varied over time — it was about two per cent higher 3,500 years ago, possibly due to factors affecting cosmic rays (like changes in solar cycles or the Earth's magnetic field).

With an extra neutron and one less proton, that's no longer a nitrogen atom — six protons plus eight neutrons spells carbon-14.

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