When was earth formed ?

The oldest rocks found so far are thought to be about 3850 million years old – so the Earth had a solid crust by then . Some meteorites and piece of Moon rock are probably 4600 million years old, so scientists think that the earth formed about 4600 million years ago.

Scientists measure the Earths age by studyting the rate of decay of radioactive elements with special equipment . This technique is called carbon- dating .