The initials BP (or bp and rarely B.P.), when placed after a number (such as 2500 BP), means “the year before the current”. Archaeologists and geologists often use this abbreviation to refer to dates obtained through radiocarbon dating techniques. Although BP is often used as an inaccurate estimate of the age of an object or event, the quirks of the radiocarbon approach make it necessary to use it in science. Radiocarbon dating was invented in the late 1940s, and within a few decades it was discovered that although the dates retrieved from the method have good, repeatable progress, they are not one-on-one with the calendar year. match. Most importantly, the researchers found that the radiocarbon date was affected by the carbon content of the atmosphere, which in the past was largely fluctuated by natural and human factors (such as the invention of iron smelting, industrial revolution and invention). internal combustion engine). The tree rings record the carbon content of the atmosphere at the time of creation and are used to calibrate or fine tune the radiocarbon date to its calendar date. Scholars use tree chronology to match those toroidal rings with known carbon fluctuations. This approach has been improved and improved many times over the past few years. BP was first established to clarify the relationship between the calendar year and the radiocarbon age. One of the advantages of using BP is that it avoids the occasional irritating philosophical debate that in our multicultural world, using AD and BC, more explicitly citing Christianity, or using the same calendar but without a clear reference: CE (common era) and BCE (before the common era). Of course, the problem is that CE and BCE still use the estimated date of birth as the reference point for their numbering system: 1 year BC and 1 BC are numerically equivalent to 1 BC and 1 year AD.