Isotope dating fossils
But while the difficulties of single life may be intractable, the challenge of determining the age of prehistoric artifacts and fossils is greatly aided by measuring certain radioactive isotopes.
Until this century, relative dating was the only technique for identifying the age of a truly ancient object.
Radiocarbon dating involves determining the age of an ancient fossil or specimen by measuring its carbon-14 content.
Carbon-14, or radiocarbon, is a naturally occurring radioactive isotope that forms when cosmic rays in the upper atmosphere strike nitrogen molecules, which then oxidize to become carbon dioxide.
This is what archaeologists use to determine the age of human-made artifacts. The half-life of carbon-14 is only 5,730 years, so carbon-14 dating is only effective on samples that are less than 50,000 years old.Half-life is defined as the time it takes for one half of a radioactive element to decay into a daughter isotope.As radioactive isotopes of elements decay, they lose their radio activity and become a brand new element known as a daughter isotope.Some of the isotopes used for this purpose are uranium-238, uranium-235 and potassium-40, each of which has a half-life of more than a million years.Unfortunately, these elements don't exist in dinosaur fossils themselves.