When it comes to dating archaeological samples, several timescale problems arise.
For example, Christian time counts the birth of Christ as the beginning, AD 1 (Anno Domini); everything that occurred before Christ is counted backwards from AD as BC (Before Christ).
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.
These statues were made on Easter Island, also known as Rapa Nui, a tiny, remote, island in the Pacific Ocean, 2,000 miles away from Chile.
Scientists have debated for decades when these giant statues were built and why the civilization of Rapa Nui collapsed. (See the picture below.) As a result, every plant and animal has the same share of each kind of carbon. This 14C breaks down over time because it is radioactive.
Think of it like a teaspoon of cocoa mixed into a cake dough—after a while, the ‘ratio’ of cocoa to flour particles would be roughly the same no matter which part of the cake you sampled.
The fact that the C doesn’t matter in a living thing—because it is constantly exchanging carbon with its surroundings, the ‘mixture’ will be the same as in the atmosphere and in all living things.
Once the organism dies, however, it ceases to absorb carbon-14, so that the amount of the radiocarbon in its tissues steadily decreases.
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.
As soon as it dies, however, the C ration gets smaller.
In other words, we have a ‘clock’ which starts ticking at the moment something dies.