Radiodating earth dating site bio
Mammals, which for 150 million years had been small, rodent-sized creatures, rapidly evolved to massive proportions in the wake of the Cretaceous-Tertiary extinction 65 million years ago.
Geological timekeeping continues to be a lively science, with new methods emerging all the time.
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).
Darwin had argued that the Earth was immensely old which gave his gradual process of evolution plenty of time to unfold.
We know it is accurate because radiometric dating is based on the radioactive decay of unstable isotopes.
Life is well over 3.5 billion years old, and until about 600 million years ago, the planet was dominated by microbes.
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.
And by comparing the ratios of those atoms to atoms from meteorites, they could estimate how long ago it was that the Earth formed along with the rest of the solar system.
In 1956 the American geologist Clair Patterson (left) announced that the Earth was 4.5 billion years old.
For example, a problem I have worked on involving the eruption of a volcano at what is now Naples, Italy, occurred 38500 years ago with a plus or minus of 300 years.