Relative dating technique
Absolute dates must agree with dates from other relative methods in order to be valid.
The most widely used and accepted form of absolute dating is radioactive decay dating. Radioactive decay refers to the process in which a radioactive form of an element is converted into a nonradioactive product at a regular rate.
Since certain species of animals existed on Earth at specific times in history, the fossils or remains of such animals embedded within those successive layers of rock also help scientists determine the age of the layers.
Similarly, pollen grains released by seed-bearing plants became fossilized in rock layers.
By measuring the amount of original and transformed atoms in an object, scientists can determine the age of that object.
Cosmic rays: Invisible, high-energy particles that constantly bombard Earth from all directions in space.
Relative dating methods are used to determine only if one sample is older or younger than another.
When a piece of pottery is heated in a laboratory at temperatures more than 930°F (500°C), electrons from quartz and other minerals in the pottery clay emit light.
Dendrochronology: Also known as tree-ring dating, the science concerned with determining the age of trees by examining their growth rings.
Half-life: Measurement of the time it takes for one-half of a radioactive substance to decay.
The nucleus of every radioactive element (such as radium and uranium) spontaneously disintegrates over time, transforming itself into the nucleus of an atom of a different element.
In the process of disintegration, the atom gives off radiation (energy emitted in the form of waves). Each element decays at its own rate, unaffected by external physical conditions.