Natural Origin
Primordial nuclides found in the earth are residues from ancient supernova explosions which occurred before the formation of the solar system. They are the long-lived fraction of radionuclides surviving in the primordial solar nebula through planet accretion until the present. The naturally occurring short-lived radiogenic radionuclides found in rocks are the daughters of these radiactive primordial nuclides. Another minor source of naturally occurring radioactive nuclides are cosmogenic nuclides, formed by cosmic ray bombardment of material in the Earth's atmosphere or crust. For a summary table showing the number of stable nuclides and of radioactive nuclides in each category, see radionuclide. Radionuclides can also be produced artificially e.g. using particle accelerators or nuclear reactors.
Read more about this topic: Radioactive Decay
Famous quotes containing the words natural and/or origin:
“Doubtless, we are as slow to conceive of Paradise as of Heaven, of a perfect natural as of a perfect spiritual world. We see how past ages have loitered and erred. “Is perhaps our generation free from irrationality and error? Have we perhaps reached now the summit of human wisdom, and need no more to look out for mental or physical improvement?” Undoubtedly, we are never so visionary as to be prepared for what the next hour may bring forth.”
—Henry David Thoreau (1817–1862)
“We have got rid of the fetish of the divine right of kings, and that slavery is of divine origin and authority. But the divine right of property has taken its place. The tendency plainly is towards ... “a government of the rich, by the rich, and for the rich.””
—Rutherford Birchard Hayes (1822–1893)