Carbon 14 is created by cosmic rays in the upper atmosphere.
C14 is continually being created and decaying, leading to an equilibrium state in the atmosphere.
Uranium 235 decay to lead has a half-life of 713 million years, so it is well suited to dating the universe.
other isotope pairs cover intermediate time periods between the spans for carbon 14 and uranium.
Radiometric dating is the method for establishing the age of objects by measuring the levels of radioisotopes in the sample. It decays to nitrogen 14 with a half life of 5730 years.
Absolute dating provides a numerical age or range in contrast with relative ...
Techniques include tree rings in timbers, radiocarbon dating of wood or ...
We note that at the instant the swimmer touches the end of the pool our wristwatch reads and 53 seconds.
How long has the competitor taken to swim the race?