The radiocarbon stopwatch buzzes round at a great rate, so fast that, after some thousands of years, its spring is almost wound down and the watch is no longer reliable.
https://en.wikipedia.org/wiki/Radiocarbon_dating
It takes 5,730 years for half the carbon-14 to decay to nitrogen; this is the half-life of carbon-14. After another 5,730 years, only one-quarter of the original carbon-14 will remain. After yet another 5,730 years, only one-eighth will be left.
The relatively short half-life of carbon-14, 5,730 years, makes dating reliable only up to about 60,000 years
