And you can look at their tree rings, and I think most of us are familiar with this idea that every year that a tree grows, it forms another layer of bark.
And so you can look back to that layer of bark just for the half life of carbon-14, and then figure out how much carbon-14 was there in the atmosphere at that period in time. Those are those speleothems that are kind of coming out of the bottom of the cave, or stalactites.
Over the past six decades, the amount of radiocarbon in people or their remains depends heavily on when they were born or, more precisely, when their tissues were formed.
Ironically, given how supposedly useless carbon dating is claimed to be, Creation Ministries International rests part of their "101 Evidences" on carbon dating being a useful method for within several thousand years.
It takes another 5,730 for half of the remainder to decay, and then another 5,730 for half of what's left then to decay and so on.
The period of time that it takes for half of a sample to decay is called a "half-life." Radiocarbon oxidizes (that is, it combines with oxygen) and enters the biosphere through natural processes like breathing and eating.
In the last video, we talked about the idea that if I dug up a bone someplace, if I dug up a bone, and if I were to measure its carbon-14, and I found that it had half of the carbon-14 that I would expect to find in a living animal or plant, that I said, hey, maybe one half life has gone by, or roughly for carbon-14, one half life is 5,730 years.
So I said maybe it's 5,730 years since this bone was part of a living animal, or it's roughly that old.