There are many methods employed by these scientists, interested in the old, to get to know the age of items.
It is possible to tell the number of years ago a particular rock or archeological site had been formed.
Imagine braving the desert heat for days or even weeks as you dig for dinosaur bones.
You find something extraordinary and want to know as much about it as you can.
Absolute dating uses clues, such as the emperor's face on a coin, to date an artifact.
Tree ring dating offers over 1,000 years of clues in dates of artifacts from the American Southwest.
Two broad categories of classification methods are relative dating and absolute dating.