Because the time it takes to convert biological materials to fossil fuels is substantially longer than the time it takes for its in the atmosphere, which attained a maximum in 1963 of almost twice what it had been before the testing began.Measurement of radiocarbon was originally done by beta-counting devices, which counted the amount of beta radiation emitted by decaying atoms in the sample and not just the few that happen to decay during the measurements; it can therefore be used with much smaller samples (as small as individual plant seeds), and gives results much more quickly.Research has been ongoing since the 1960s to determine what the proportion of in the atmosphere has been over the past fifty thousand years.
Libby received the Nobel Prize in Chemistry for his work in 1960.
They all have six protons since they are carbon, and therefore they are identical chemically.
The body cannot tell them apart, so they maintain approximately the same relative abundance in living tissue as it does in the atmosphere.
Once the material solidifies the decay product will thereafter be fixed in place with the radioactive material.
This is the date we determine with radiometric dating.
We measure the current ratio of C-14/C-12 and compare it to naturally occurring ratio.