Isotope dating problems
When this method was first developed, a fairly large amount of carbon was necessary for dating but use of the AMS (accelerator mass spectrometer) today necessitates only a few milligrams for analysis. What I want to do in this video is kind of introduce you to the idea of, one, how carbon-14 comes about, and how it gets into all living things. They can also be alpha particles, which is the same thing as a helium nucleus. And they're going to come in, and they're going to bump into things in our atmosphere, and they're actually going to form neutrons. And we'll show a neutron with a lowercase n, and a 1 for its mass number. And what's interesting about this is this is constantly being formed in our atmosphere, not in huge quantities, but in reasonable quantities. Because as soon as you die and you get buried under the ground, there's no way for the carbon-14 to become part of your tissue anymore because you're not eating anything with new carbon-14.These samples are carefully cataloged and analyzed with a mass spectrometer.The mass spectrometer is able to give information about the type and amount of isotopes found in the rock.The explanation was that the physicists had assumed that the amount of C-14 in the atmosphere had been constant, when in fact it had varied over time.The solution came using dendrochronology (tree ring dating).One standard deviation has a 68% probability and two standard deviations have a 95% probability.
Fossils are collected along with rocks that occur from the same strata.After one half life, it would have had 1/2 the carbon.And then after another half life, half of that also turns into a nitrogen-14.But as more dates became available, Egyptologists, who had hieroglyphic records back thousands of years, began to recognize that C-14 dates were generally too young.
They proved this by showing that C-14 dates of wooden artifacts with cartouches (dated royal names) did not agree.
And so this would involve two half lives, which is the same thing as 2 times 5,730 years. You'd say this thing is 11,460 years old, give or take.