The resulting radiocarbon combines with atmospheric oxygen to form radioactive carbon dioxide, which is incorporated into plants by photosynthesis; animals then acquire in a sample from a dead plant or animal such as a piece of wood or a fragment of bone provides information that can be used to calculate when the animal or plant died.The older a sample is, the less (the period of time after which half of a given sample will have decayed) is about 5,730 years, the oldest dates that can be reliably measured by this process date to around 50,000 years ago, although special preparation methods occasionally permit accurate analysis of older samples.By measuring the amount of radioactive decay of a radioactive isotope with a known half-life, geologists can establish the absolute age of the parent material.A number of radioactive isotopes are used for this purpose, and depending on the rate of decay, are used for dating different geological periods.Paleontology seeks to map out how life evolved across geologic time.A substantial hurdle is the difficulty of working out fossil ages.
The level of atmospheric Radiometric dating in general, of course, poses a huge problem for people who believe that the universe is 6000-odd years old.
Ironically, given how supposedly useless carbon dating is claimed to be, Creation Ministries International rests part of their "101 Evidences" on carbon dating being a useful method for within several thousand years.
Geochronology is the science of determining the age of rocks, fossils, and sediments using signatures inherent in the rocks themselves.
Absolute geochronology can be accomplished through radioactive isotopes, whereas relative geochronology is provided by tools such as palaeomagnetism and stable isotope ratios.
By combining multiple geochronological (and biostratigraphic) indicators the precision of the recovered age can be improved.