Archaeologists use the exponential, radioactive decay of carbon 14 to estimate the death dates of organic material.
And if it isn't constant, how do you calibrate your measurement so you can actually figure out how much carbon-14 there is relative to living plants and animals at that time?
And the way that you can make that calibration, because it turns out it isn't perfectly constant, the way that you can make that calibration, there's two ways, and I have pictures here of both of them, one is to look at tree things. And I'm told this will work up to about 10,000 years. I don't know of any 10,000 year old trees, I don't think anyone does, but maybe there's some remains of old trees.
Plants and animals assimilate carbon 14 from carbon dioxide throughout their lifetimes.
When they die, they stop exchanging carbon with the biosphere and their carbon 14 content then starts to decrease at a rate determined by the law of radioactive decay.
In the case of radiocarbon dating, the half-life of carbon 14 is 5,730 years.
This half life is a relatively small number, which means that carbon 14 dating is not particularly helpful for very recent deaths and deaths more than 50,000 years ago.
Now, when I did that, I made a pretty big assumption, and some you all have touched on this in the comments on You Tube on the last video, is how do I know that this estimate I made is based on the assumption that the amount of carbon-14 in the atmosphere would have been roughly constant from when this bone was living to now?
And so the question is, is the amount of carbon-14 in the atmosphere and in the water, and in living plants and animals, is it constant?
Libby and coworkers, and it has provided a way to determine the ages of different materials in archeology, geology, geophysics, and other branches of science.