This book spells out in detail how the age of the Earth has been determined over the centuries. First — the 'biblical' age: how was the date of Creation 4004 BC figured out? A date which is so important even today … it is the basis of claims made by millions that the Earth is only about 6000 years old. Next — the response of geologists (and Darwin) for a very old Earth. Then, Kelvin's calculation of how long it would take for a hot Earth to cool down to its present state. And finally, today's answer ('billions'), based on the properties of radioactive materials. So, how old is Planet Earth? Readership: General readers who wish to know answers about the history of the Earth.