How do we know the earth is billions of years old?

The Earth is very old. But how old, exactly? And how can we know with any degree of confidence? read more

Based on the very old zircon rock from Australia we know that the Earth is at least 4.374 billion years old. But it could certainly be older. Scientists tend to agree that our little planet is around 4.54 billion years old—give or take a few hundred million. read more

The Earth formed a persistent solid surface 4.54 billion years ago. Life appeared no less than 3.8 billion years ago. A billion years later, cyanobacteria started producing oxygen as a waste product, and this started precipitating iron dissolved in the oceans into the deposits we now quarry for ore. read more

The age of the Earth is 4.54 ± 0.05 billion years (4.54 × 10 9 years ± 1%). This age may represent the age of the Earth’s accretion, of core formation, or of the material from which the Earth formed. read more