Radioactive Nuclides by Half-Life

This table of radioactive nuclides sorted by their half-lives is taken from Miller, who uses it to point out that only those radionuclides with half-lives greater than 80 million years are found in nature. The exceptions are those marked with "Yes-P" indicating that they are being produced in nature, but would otherwise be missing. The point of Miller's use was to make the case that the Earth is more than 80 million years old since all isotopes with shorter halflives are no longer found in nature. It is also evident that the Earth is not infinitely old because all the radioactive series would have decay. There are various ways of modeling the age of the Earth, and the values center around 4.5 billion years.

Beryllium-10 is found because it is continually produced by cosmic ray bombardment of the upper atmosphere. So very small amounts of this isotope are found in rainfall and sediment. Neptunium-237 is produced by cosmic ray bombardment of the moon. There are other short half-life isotopes found on the Earth from the natural radioactive series.

Note: Information about isotopes may be found in tables linked to the