Radiocarbon dating before 1950
P.), when placed after a number (as in 2500 BP), means "years Before the Present".
Archaeologists generally use this abbreviation to refer to dates that were obtained through the radiocarbon dating technology, although not exclusively; it was certainly made necessary by the quirks of the radiocarbon methodology.
The prodigious mobilization of science that produced nuclear weapons was so far-reaching that it revolutionized even the study of ancient climates.
The Beta-counting method detects the rate at which purified carbon decays. A rate of 7 decays/gram/minute would indicate an age of one half-life, or 5730 years old. Climate science required the invention and mastery of many difficult techniques.These had pitfalls, which could lead to controversy.3.5 decays/gram/minute of carbon would be produced by a sample 11,460 years old.
However, atmospheric testing of nuclear weapons in the late 1950's and early 1960's greatly increased the amount of radiocarbon in the atmosphere, so the decay rate of 14 decays per minute more than doubled.
The radioactive isotope carbon-14 is created in the upper atmosphere when cosmic-ray particles from outer space strike nitrogen atoms and transform them into radioactive carbon.