Radiometric dating, often called radioactive dating, is a technique used to determine the age of materials such as rocks.
It is based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates.
For example, decay of the parent isotope Rb-87 (Rubidium) produces a stable daughter isotope, Sr-87 (Strontium), while releasing a beta particle (an electron from the nucleus).
("87" is the atomic mass number = protons neutrons.
There are several ways to figure out relative ages, that is, if one thing is older than another.
For example, looking at a series of layers in the side of a cliff, the younger layers will be on top of the older layers.
By establishing geological timescales, radiometric dating provides a significant source of information about the ages of fossils and rates of evolutionary change, and it is also used to date archaeological materials, including ancient artifacts.
The different methods of radiometric dating are accurate over different timescales, and they are useful for different materials.
Recall that an isotope is a particular form of an element.It is the principal source of information about the absolute age of rocks and other geological features, including the age of the Earth itself, and it can be used to date a wide range of natural and man-made materials.The best-known radiometric dating techniques include radiocarbon dating, potassium-argon dating, and uranium-lead dating.The Geologic Time Scale was originally laid out using relative dating principles.Numerical dating, the focus of this exercise, takes advantage of the "clocks in rocks" - radioactive isotopes ("parents") that spontaneously decay to form new isotopes ("daughters") while releasing energy.However, the crater number relation must be calibrated against something with a known age.To measure the passage of long periods of time, scientists take advantage of a regularity in certain unstable atoms.This amount is a percentage of the original parent amount. Parent Decay and Daughter Growth Curves The half-life of U-235 decaying to Pb-207 is 713 million years.Note that this half-life can be obtained from the graph at the point where the decay and growth curves cross.Or you can tell that certain parts of the Moon's surface are older than other parts by counting the number of craters per unit area.The old surface will have many craters per area because it has been exposed to space for a long time. If you assume that the impact rate has been constant for the past several billion years, then the number of craters will be proportional to how long the surface is exposed.