Radiocarbon dating was invented in the late 1940s, and within a few decades, it was discovered that while the dates retrieved from the method have a sound, repeatable progression, they are not a one-to-one match with calendar years. However, a major disadvantage with using BP is--the Present year, of course, changes every twelve months.
Radiocarbon dates are affected by the amount of carbon in the atmosphere, which it was discovered, fluctuated greatly in the past for both natural and human caused reasons (such as the invention of iron smelting, the Industrial Revolution and the invention of the combustion engine). Since the BP designation was originally associated with radiocarbon dating, archaeologists chose the year 1950 as a reference point for the 'the present'.
Unlike radiocarbon dates, TL dates are calculated in straight calendar years--and the dates measured range from a few years to hundreds of thousands of years.
It might not matter if a 100,000 year old luminescence date was measured in 1990 or 2010--the scale is not that close.
But for one that returned a date of only 500 years ago, even 50 years difference would be an important distinction. Current practice is to quote the age along with the date it was measured, but other options are being considered.
Among those are using 1950 as a reference point; or better still, use 2000, cited in the literature as b2k.
After the Gregorian calendar was established throughout most of the world, atomic clocks have allowed us to adjust our modern calendars with leap seconds to correct for the slowing spin of our planet and other corrections. Nachum Dershowitz and colleagues as fascinating examples.Tree rings, which record the amount of atmospheric carbon, are used to calibrate radiocarbon dates, and that methodology has been refined several times over the last few years. The date was chosen because radiocarbon dating was invented in the late 1940s.BP was first established as a way to clarify that relationship. C., with their explicit references to Christianity, or to use the alternatives C. At the same time, atmospheric nuclear testing, which throws huge amounts of carbon into our atmosphere, was begun in the 1940s.But, perhaps the most interesting outcome of all this investigation, for us geeks, anyway, is the wide variety of modern mathematicians and programmers who have taken a crack at perfecting the matches between ancient calendars using modern technology. See the entries on RCYBP and Radiocarbon Dating for further information about carbon 14 dating.
One advantage to using BP is it avoids the whole philosophical debate about whether in this multicultural world of ours it is more appropriate to use A. Radiocarbon dates after 1950 will likely be virtually useless, unless we can figure out a way to calibrate for that. To adjust for that, scholars now typically cite both raw, uncalibrated radiocarbon dates as years RCYBP (radiocarbon years before the present), alongside calibrated versions of those dates as cal BP, cal AD and cal BC (calibrated or calendar years BP, AD and BC).
Thermolumiscence dating, on the other hand, has a unique situation.