Scientific definition radioactive dating
The technique of comparing the abundance ratio of a radioactive isotope to a reference isotope to determine the age of a material is called radioactive dating.
Many isotopes have been studied, probing a wide range of time scales.
An age could be estimated by measuring the amount of carbon-14 present in the sample and comparing this against an internationally used reference standard.
The CRA conventions include (a) usage of the Libby half-life, (b) usage of Oxalic Acid I or II or any appropriate secondary standard as the modern radiocarbon standard, (c) correction for sample isotopic fractionation to a normalized or base value of -25.0 per mille relative to the ratio of carbon 12/carbon 13 in the carbonate standard VPDB – Cretaceous belemnite formation at Peedee in South Carolina, (d) zero BP (Before Present) is defined as AD 1950, and (e) the assumption that global radiocarbon levels are constant.
There are three principal techniques used to measure carbon 14 content of any given sample— gas proportional counting, liquid scintillation counting, and accelerator mass spectrometry.
Gas proportional counting is a conventional radiometric dating technique that counts the beta particles emitted by a given sample. In this method, the carbon sample is first converted to carbon dioxide gas before measurement in gas proportional counters takes place.
By knowing how much carbon 14 is left in a sample, the age of the organism when it died can be known.
It must be noted though that radiocarbon dating results indicate when the organism was alive but not when a material from that organism was used.