absolute dating senn-yâbi-ye avast Fr.: datation absolue Any method of measuring the age of an event or object in years. For example, in geology, this method can, unlike → relative dating, give us the age of a rock or fossil in x number of years. The most widely used and accepted method of absolute dating is → radioactive dating. See also: → radiocarbon dating, → radiometric dating. |
dating senn yâbi (#) Fr.: datation Use of appropriate techniques to estimate the age of geological specimens or astronomical objects such as meteorites. Verbal noun of date, from O.Fr. date, from M.L. → data. Sen yâbi, from Ar. sen "age" + yâbi verbal noun of yâftan, yâbidan "to find, discover; to obtain, acquire," Mid.Pers. ayâftan, ayâpênitan "to reach, attain," Manichean Mid.Pers. 'y'b "to attain," Parthian, Sogdian (+ *pati-) pty'b "to reach, obtain," Av. ap- "to reach, overtake," apayeiti "achieved, reached," Skt. âp- "to reach, gain," âpnoti "reaches, gains," Gk. hapto, haptomai "to touch, cling to, adhere to," L. apiscor "touch, reach;" PIE base *ap- "to take, reach." |
radioactive dating sen yâbi-ye partow-žirâ Fr.: datation radioactive Determining the age of an object from the → radioactive decay of its constituting material. The technique consists of comparing the → abundance ratio of a → radioactive isotope to its → decay product. This will yield the number of half-lives that have occurred since the sample was formed. More specifically, if an object is made up of 50 % decay product then it has gone through 1 → half-life. 75% decay product equals 2 half-lives, 87.5% decay product equals 3 half-lives, 93.76% decay product equals 4 half-lives, and so on. For example, the decay product of → uranium-238 (^{238}U) is → lead-206 (^{206}Pb). The half-life of ^{238}U is 4.5 billion years. Hence, if the sample has gone through two half-lives, it is 9 billion years old. See also: → radiocarbon dating. → radioactive; → dating. |
radiocarbon dating senn yâbi-ye partow-karboni Fr.: datation au radiocarbone A radioactive dating technique, applied to organic materials, which measures the content of the radioactive isotope of carbon ^{14}C. The radioactive carbon isotopes created by the impact of cosmic rays with the nitrogen atoms of the atmosphere find their way, via carbon dioxide and photosynthesis, into living material. When an organic material dies it ceases to acquire further ^{14}C atoms, and its ^{14}C fraction declines at a fixed exponential rate due to the radioactive decay of ^{14}C. Comparing the remaining ^{14}C fraction of a sample to that expected from atmospheric ^{14}C allows the age of the sample to be estimated. → radiocarbon; → dating. |
radiometric dating senn yâbi-ye tâbeš-sanjik, ~ tâbeš-sanji Fr.: datation radiométrique A dating method that uses measurements of certain radioactive isotopes to calculate the ages in years (absolute age) of rocks and minerals. → radiometer; → dating. |
relative dating senn-yâbi-ye bâzâni Fr.: datation relative A method of dating that can only tell us whether an event or object is older or younger than another event or object. In geology, different layers of rock are compared to determine an ordered sequence of events in geologic history. In contrast to → absolute dating, relative dating cannot give the actual age of a rock. See also → stratigraphy. |