How do we know how old the Earth is?

When is the next comet? What is past the milky way? Which animals have been sent into space? Did the moon come before the Earth? What lifts up the moon? What are all the dents in the moon? How did the moon form? How do we know how old the Earth is? Why are Neptune and Uranus blue? Why is the sun the only star we can see in the daytime? How fast do you need to go to escape a black hole? Is there other life in the universe? In this 'Classroom Edition' of Ask The Naked Scientists, Dr Chris Smith, Clarence Ford are answering the questions set by pupils at Parow East Primary School... Like this podcast? Please help us by supporting the Naked Scientists