Carbon dating half lives
So even we humans are radioactive because of trace amounts of radiocarbon in our bodies.After radiocarbon forms, the nuclei of the carbon-14 atoms are unstable, so over time they progressively decay back to nuclei of stable nitrogen-14.3 A neutron breaks down to a proton and an electron, and the electron is ejected. The ejected electrons are called beta particles and make up what is called beta radiation. Different carbon-14 atoms revert to nitrogen-14 at different times, which explains why radioactive decay is considered a random process.So if we started with 2 million atoms of carbon-14 in our measured quantity of carbon, then the half-life of radiocarbon will be the time it takes for half, or 1 million, of these atoms to decay.The radiocarbon half-life or decay rate has been determined at 5,730 years.The most well-known of all the radiometric dating methods is radiocarbon dating.Although many people think radiocarbon is used to date rocks, it is limited to dating things that contain carbon and were once alive (fossils).Let’s suppose we find a mammoth’s skull, and we want to date it to determine how long ago it lived.
So one would think that since the radiocarbon dating method works on organic (once-living) materials, then radiocarbon could be used to date fossils.
The difference in the number of sand grains represents the number of carbon-14 atoms that have decayed back to nitrogen-14 since the mammoth died. The sand grains in the top bowl fall to the bottom bowl to measure the passage of time.
Because we have measured the rate at which the sand grains fall (the radiocarbon decay rate), we can then calculate how long it took those carbon-14 atoms to decay, which is how long ago the mammoth died. If all the sand grains are in the top bowl, then it takes exactly an hour for them all to fall.
After plants and animals perish, however, they no longer replace molecules damaged by radioactive decay.
Instead, the radiocarbon atoms in their bodies slowly decay away, so the ratio of carbon-14 atoms to regular carbon atoms will steadily decrease over time (figure 3).