Physics of archaeology is to accurately determine the age of discovery

© RIA Novosti / Alexander to Nikolskaia in photomontage with gilded cardboard mask in a wooden sarcophagus found during archaeological research conducted by CEI wounds of Deir El-Banat in the Fayum oasis of EgyptPhysics of archaeology is to accurately determine the age of discovery© RIA Novosti / Alexander to Nikolskaia the image Bank

To determine the age of organic remains including tissue and bones, archaeologists use the method of radiocarbon Dating. It allows very accurate Dating of the find, as it is based on radioactive decay, however, the method sometimes fails.

Physical principles of radiocarbon Dating

In the bodies of animals and plants and all biological organics ratio of radioactive and stable carbon remains constant. This fact was used by the American scientist Willard Frank Libby to develop in the 1950-ies of the radiocarbon method of age determination. In 1960 he received a Nobel prize in chemistry.

On Land carbon is represented by three isotope — varieties of atoms, different number of neutrons. Their ratio in the atmosphere is roughly as follows: 12C — 98,93%, 13C is 1.07% and 14C — 10-12%. The first two isotopes are stable, and the third is radioactive, that is prone to spontaneous change in the composition or internal structure by emitting, for example, elementary particles. The isotope 14C is constantly produced in the Earth’s atmosphere at the altitude of 11 to 50 kilometers of the bombardment of nitrogen by neutrons.

Radioactive isotopes are included in the circuit together with stable isotopes of carbon, and this means that they find themselves in a living organism by respiration or photosynthesis. While the animal or plant lives, the ratio of all three carbon isotopes is maintained constant. After the death of the body exchange with the environment stops. In the remains becomes less of 14C, because it is falling apart.

To cope with the first problem helped calculate the age of trees by the number of annual rings in different regions of the world. Scientists have studied sections of bristlecone pine in the southwest USA and the oaks, and buried in river and swamp deposits of Europe. Some changes in the schedule of fluctuation of the level of radioactive carbon has made archaeological finds, whose age was determined according to the written sources — for example, grain in a tomb with a date of burial. For more ancient samples used the results of measurements of the content of 14C in corals, the age of which established the thorium-uranium method. All of this allowed us to calibrate a graph of the content of 14C in the atmosphere at the time and now the data obtained by the radiocarbon analysis, easy to fix just in a computer program.

CC BY-SA 3.0 / Oke / Bristlecone Pines (Pinus longaeva), Schulman Grove, Inyo National Forest, eastern CaliforniaОстистая pine age 4847 years, determined by the number of tree ringsPhysics of archaeology is to accurately determine the age of discoveryCC BY-SA 3.0 / Oke / Bristlecone Pines (Pinus longaeva), Schulman Grove, Inyo National Forest, eastern CaliforniaОстистая pine age 4847 years, determined by the number of tree rings

Error analysis associated with the additional amount of 14C trapped in a dead specimen from the outside, to fix much more difficult. To fully calculate the impact of all sources of radioactive isotopes in the investigated object is impossible, so the Dating may vary within ±300 years. In many cases, especially when we are talking about the prehistoric period is not as critical. Doubt is when radiocarbon Dating showed absolutely some incredible archaeological age of the object.

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