Radioactive elements are unstable; they breakdown spontaneously into more stable atoms over time, a process known as radioactive decay.Radioactive decay occurs at a constant rate, specific to each radioactive isotope.The method works best if neither the parent nuclide nor the daughter product enters or leaves the material after its formation.
Fossils may be dated by taking samples of rocks from above and below the fossil's original position.
Radiometric dating measures the decay of radioactive atoms to determine the age of a rock sample.
It is founded on unprovable assumptions such as 1) there has been no contamination and 2) the decay rate has remained constant.
Radioactive elements were incorporated into the Earth when the Solar System formed.
All rocks and minerals contain tiny amounts of these radioactive elements.