Living things top up their carbon-14 from the air. The instant an organism dies that intake stops and the clock starts: the C-14 already inside simply decays, halving every 5,730 years.
Each atom decays at random, but ten thousand of them are predictable. Measure what fraction of the original C-14 survives and the exponential curve reads off the age. Here that fraction is a real, noisy sample — capture too few atoms and the reading scatters.
Contamination is the field's nightmare. A trace of modern carbon — a fingerprint, a rootlet, a preservative — carries full C-14 and drags the measured ratio up, so the sample dates far too young. The older the true age, the more violent the error.
And the method has a hard floor. Past roughly ten half-lives (~50,000 years) so little C-14 remains that the curve is nearly flat — the tiniest measurement error swings the date by millennia. That is why radiocarbon runs out.
Something in the simulation stopped unexpectedly — the lesson continues without it. Nothing you did was wrong; you can move on.