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Carbon dating - definition of carbon dating by The Free Dictionary
Radiocarbon dating also referred to as carbon dating or carbon dating is a method for determining the age of an object containing organic material by using the properties of radiocarbon , a radioactive isotope of carbon. The method was developed in the late s at the University of Chicago by Willard Libby , who received the Nobel Prize in Chemistry for his work in It is based on the fact that radiocarbon 14 C is constantly being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen. The resulting 14 C combines with atmospheric oxygen to form radioactive carbon dioxide , which is incorporated into plants by photosynthesis ; animals then acquire 14 C by eating the plants. When the animal or plant dies, it stops exchanging carbon with its environment, and thereafter the amount of 14 C it contains begins to decrease as the 14 C undergoes radioactive decay. Measuring the amount of 14 C in a sample from a dead plant or animal, such as a piece of wood or a fragment of bone, provides information that can be used to calculate when the animal or plant died. The older a sample is, the less 14 C there is to be detected, and because the half-life of 14 C the period of time after which half of a given sample will have decayed is about 5, years, the oldest dates that can be reliably measured by this process date to approximately 50, years ago, although special preparation methods occasionally make accurate analysis of older samples possible.
Before Present BP years is a time scale used mainly in archaeology , geology , and other scientific disciplines to specify when events occurred before the origin of practical radiocarbon dating in the s. Because the "present" time changes, standard practice is to use 1 January as the commencement date epoch of the age scale. The BP scale is sometimes used for dates established by means other than radiocarbon dating, such as stratigraphy. Some archaeologists use the lowercase letters bp , bc and ad as terminology for uncalibrated dates for these eras.
By: Marshall Brain. A child mummy is found high in the Andes and the archaeologist says the child lived more than 2, years ago. How do scientists know how old an object or human remains are?