Radiocarbon dating calculation
However, limiting ages or "backgrounds" are also determined by process blanks which correspond to the method used to extract the carbon from the sample.» NOSAMS General Statement of C from contamination introduced during chemical preparation, collection or handling.Outside the range of recorded history, calibration of the 14 clock is not possible.This means the above calculations are only evolution speculation and NOT backed up by real science.After acceleration and removal of electrons, the emerging positive ions are magnetically separated by mass and the C counts per second are collected.It is expected then, for a 5,570 year (1 half-life) or 11,140 year old (2 half-lives) sample that 125 or 63 counts per second would be obtained.Other useful radioisotopes for radioactive dating include Uranium -235 (half-life = 704 million years), Uranium -238 (half-life = 4.5 billion years), Thorium-232 (half-life = 14 billion years) and Rubidium-87 (half-life = 49 billion years).
Due to counting and measurement errors for the blanks and samples, statistical errors are higher for very old samples.
Although one can simply measure older samples for longer times, there are practical limits to the minimum sample activity that can be measured.
At the present time, for a 1 milligram sample of graphite, this limiting age is about ten half-lives, or 60,000 years, if set only by the sample size.
However, radioisotope dating may not work so well in the future.
Anything that dies after the 1940s, when Nuclear bombs, nuclear reactors and open-air nuclear tests started changing things, will be harder to date precisely.