Read more on calibration and accuracy of radiocarbon dating.

The Biblical book of Exodus does not name the Pharaoh whom Moses encountered after his return from Sinai. The bibliographies in these sections are of more value than the discussions in the text, which adopts a very negative view on the historicity of the Exodus.

By about 58,000 years (ten half-lives) after an organism has died, there's so little radioactive carbon left (less than 1/1000) that calculations of age are no longer accurate.

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Not only that, we top up our carbon-14 levels every time we eat.

And plants top up their radioactive carbon every time they turn carbon dioxide to food during photosynthesis.

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.

Chemically, carbon-14 is no different from non-radioactive carbon atoms, so it ends up in all the usual carbon places — one trillionth of the carbon atoms in air, plants, animals and us are radioactive.

All radioactive atoms eventually decay into something more stable, and carbon-14 decays into nitrogen.

The exact age of an unknown sample can never be known for sure, so short of discovering a time machine, 95 per cent accuracy is as good as it gets.

Radiocarbon may not be perfect, but as any single 30-something can attest, no dating method is.

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.