How do we know how old Earth is?
When you buy through links on our site , we may earn an affiliate commission . Here ’s how it work . Earth is some 4.54 billion years old . In that metre , it has visit continents conformation and disappear , chalk caps expand and retreat , and life evolve from single - celled organisms into gloomy whales . But how do we know Earth ’s long time ? We start by looking inside it ....