Methods of dating the earth
When carbon-14 falls to Earth, it is absorbed by plants.
These plants are eaten by animals who, in turn, are eaten by even larger animals.
By measuring the amount of carbon-14 remaining, scientists can pinpoint the exact date of the organism's death.
The range of conventional radiocarbon dating is 30,000 to 40,000 years.
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.
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.
In addition to the radiocarbon dating technique, scientists have developed other dating methods based on the transformation of one element into another.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.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.If a certain kind of pollen is found in an archaeological site, scientists can check when the plant that produced that pollen lived to determine the relative age of the site.