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Asked by snip1 to Austin, Kirsty, Nicola, Nike, Sarah on 14 Jun 2012. This question was also asked by josua2k, dani2.
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Austin Elliott answered on 14 Jun 2012:
The scientific consensus for the age of the earth is about 4.5 Billion years, and for the time since the Big Bang (the beginning of the Universe) the best estimate we have is about 13.75 Billion years.
Estimates of when life began on earth are more variable, but the evolutionary biologists think bacteria and Archaea (single-celled organisms with no nuclei or organelles) were around within a Billion years of earth’s formation.
Much more detail on Wikipedia (e.g. here), or probably in your textbooks.
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Kirsty Ross answered on 15 Jun 2012:
If you were to squish the lifetime of the earth into just one hour, then not a lot of life was around for the first 15 mins or so. At 17:37, single celled organisms (bacteria etc) came into life but cells with a nucleus didn’t appear until 40:26. Dinosaurs appeared at 57:01, and disappeared at 59:09. Modern humans have only been around since 59:59.9! More info here: http://en.wikipedia.org/wiki/Geologic_time_scale
Comments
Austin commented on :
That ‘parts of the hour’ timescale is really good, Kirsty. Had forgotten that. It does show you very well just how briefly humans have been around on the earth compared to the whole of geological time.