Radiometric dating or radioactive dating is a technique used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed.The method compares the abundance of a naturally occurring radioactive isotope within the material to the abundance of its decay products, which form at a known constant rate of decay.Radioactive decay can be used as a “clock” because it is unaffected by physical (e.g. For instance, the amount varies according to how many cosmic rays reach Earth.This is affected by solar activity and the earth’s magnetic field.
Radiocarbon dating works by comparing the three different isotopes of carbon.and is now the principal source of information about the absolute age of rocks and other geological features, including the age of fossilized life forms or the age of the Earth itself, and can also be used to date a wide range of natural and man-made materials.Together with stratigraphic principles, radiometric dating methods are used in geochronology to establish the geological time scale.It goes without saying that this is a significant deviance.So then, how do scientists know what the original composition of rocks were?Isotopes of a particular element have the same number of protons in their nucleus, but different numbers of neutrons.This means that although they are very similar chemically, they have different masses.All ordinary matter is made up of combinations of chemical elements, each with its own atomic number, indicating the number of protons in the atomic nucleus.Additionally, elements may exist in different isotopes, with each isotope of an element differing in the number of neutrons in the nucleus.I understand how radioactive dating works, but something about it concerns me. If we have a rock and assume that it was 100% carbon-14 at formation, and we now measure it to be 25% carbon-14 and 75% nitrogen-14 (I know nitrogen is a gas, but bear with me), then we can calculate that the rock has been around long enough to pass through 2 half-lives (2 x 5,730 years = 11,460 years). If, in fact, the rock was 50% carbon-14 and 50% nitrogen-14 at its formation, then it would actually be only 5,730 years old (only half the originally calculated age). This measurement seems to hinge on the fact that we know that the rock was originally 100% carbon-14.