How Old Is Earth?

How Old Is Earth?

Getting our heads around TIMESCALES and CHRONOLOGY can be hard. Even archaeologists, who think a lot about time, have to constantly remind themselves about how events are positioned along a timescale and how they relate to one another.

Condensing timescales can be mindboggling, so to help us there's nothing like a good analogy and an infographic! Here we've used a 12 hour clock face to see if we can get to grips with how old the earth is:

The earth is about 4.6 billion (4600 million) years old. We know this because scientists have studied the radioactive decay of certain rocks.
If you squeeze 4.6 billion years of earth's history into a 12 hour clock face, then the some of the oldest rocks ever discovered formed at about 2.52. Life first appeared as simple bacteria around 4.20, then not a lot really happened until about 10.30 when many celled animals made an entrance. At about 11 land plants appeared and by 11.30 dinosaurs were roaming the land. Another 25 minutes later flowering plants bloomed and the dinosaurs were replaced by birds and mammals. Human-like animals arrived only about half a minute (30 seconds!) before noon! And the entire history of civilisation spans just the last tenth of a second!
For most of its history earth has been a pretty empty and barren place and we make such a minute part of it's existence. Sometimes this can be quite a comforting feeling when things get a bit too much in the here and now - learning about these huge timescales can sometimes help give us a broader perspective. 
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