> The abbreviation "BP", with the same meaning, has also been interpreted[1] as "Before Physics"; that is, before nuclear weapons testing artificially altered t

> The abbreviation "BP", with the same meaning, has also been interpreted[1] as "Before Physics"; that is, before nuclear weapons testing artificially altered the proportion of the carbon isotopes in the atmosphere, making dating after that time likely to be unreliable. Kind of neat to think that a civilization 10 million years from now could have some clue about our level of technological development by noting the atmospheric nuclear weapons testing in the geological record.