Radiometric dating evolution
He came up with that figure by estimating how long it had taken for the planet to cool down to its current temperature from its molten infancy.
But Kelvin didn't, and couldn't, know that radioactive atoms such as uranium were breaking down and keeping the planet warmer than it would be otherwise.
Radioactive clocks have shown that evolution can change its pace the Cambrian Explosion of about 535 million years ago saw the relatively rapid emergence of many major lineages of animals in just a few million years.
When Rutherford announced his findings it soon became clear that Earth is millions of years old.
These scientists and many more after them discovered that atoms of uranium, radium and several other radioactive materials are unstable and disintegrate spontaneously and consistently forming atoms of different elements and emitting radiation, a form of energy in the process.
At the dawn of the twentieth century, physicists made a revolutionary discovery: elements are not eternal.
Atoms can fuse together to create new elements; they can also spontaneously break down, firing off subatomic particles and switching from one element to another in the process (see figure, right).