Which could be used for things up to around 50,000 years old. So around that time span on our timeline. And it's based on this idea that you have this atmospheric carbon-14 that actually comes from nitrogen-14 that gets between interactions with the solar wind and these cosmic particles becomes this radioactive carbon-14 and that carbon-14, which can become part of carbon dioxide, incorporated into plants through photosynthesis, which then get eaten into animals. So while something is living, they will have a certain amount of carbon-14 in their tissue. But then once they die, they're no longer adding more carbon-14. And the carbon-14 decays into the more stable carbon-12. And so based on the ratio between the carbon-14 to the carbon-12, and it takes roughly 5,000 years, 5,730 years to be exact, for roughly half of the carbon-14 to decay into carbon-12.