Carbon 14 dating organic material
When the organism dies, the supply stops, and the carbon-14 contained in the organism begins to spontaneously decay into nitrogen-14.The time it takes for one-half of the carbon-14 to decay (a period called a half-life) is 5,730 years.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).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.
Stratigraphy: Study of layers of rocks or the objects embedded within those layers.
This method is based on the assumption (which nearly always holds true) that deeper layers of rock were deposited earlier in Earth's history, and thus are older than more shallow layers.
The successive layers of rock represent successive intervals of time.
Eventually, the entire ecosystem (community of plants and animals) of the planet, including humans, is filled with a concentration of carbon-14.
As long as an organism is alive, the supply of carbon-14 is replenished.
Narrow rings grow in cold or dry years, and wide rings grow in warm or wet years.