Dating organic material
Relative dating methods are used to determine only if one sample is older or younger than another.Absolute dating methods are used to determine an actual date in years for the age of an object.With sensitive instrumentation, this range can be extended to 70,000 years.In addition to the radiocarbon dating technique, scientists have developed other dating methods based on the transformation of one element into another.These include the uranium-thorium method, the potassium-argon method, and the rubidium-strontium method. Thermoluminescence (pronounced ther-moeloo-mi-NES-ence) dating is very useful for determining the age of pottery.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.The older the pottery, the brighter the light that will be emitted.
Cosmic rays: Invisible, high-energy particles that constantly bombard Earth from all directions in space.
The age of the remains of plants, animals, and other organic material can be determined by measuring the amount of carbon-14 contained in that material.
Carbon-14, a radioactive form of the element carbon, is created in the atmosphere by cosmic rays (invisible, high-energy particles that constantly bombard Earth from all directions in space).
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.
Narrow rings grow in cold or dry years, and wide rings grow in warm or wet years.