The core also likely contains radiogenic sources, although how much is uncertain.
It has been proposed that significant core radioactivity (1-2 TW) may be caused by high levels of U, Th, and K.
dating and the ages of fossil hominids, molecular dating and divergence times for mammalian lineages, meteorites and the age of the solar system, and the use of color-magnitude diagrams for assessing ages of collections of stars.
Argon is a gas that does not ordinarily combine with other elements.
So, when a mineral forms – whether from molten rock, or from substances dissolved in water – it will be initially argon-free, even if there is some argon in the liquid.
However, if the mineral contains any potassium, then decay of the K isotope present will create fresh argon-40, that will remain locked up in the mineral.
Since the rate at which this conversion occurs is known, it is possible to determine the elapsed time since the mineral formed by measuring the ratio of U, as the source of radiogenic heat.
It is used for human and animal bone and other organic material.
Specific changes in its amino acid structure (racemization or epimerization) which occur at a slow, relatively uniform rate, are measured after the organism's death.The basis for the technique is the fact that almost all amino acids change from optically active to optically passive compounds (racemize) over a period of time.a technique for determining the age of minerals based on the occurrence in natural potassium of a small fixed amount of radioisotope 40K that decays to the stable argon isotope 40Ar with a half-life of 1.28x109 years. It makes up 0.012% (120 ppm) of the total amount of potassium found in nature.Potassium-40 is a rare example of an isotope that undergoes all three types of beta decay.About 89.28% of the time, it decays to calcium-40 ( Potassium-40 is especially important in potassium–argon (K–Ar) dating.