Time: Earth Time

In the episode about Cosmic Time, theoretical physicist Michio Kaku explored the history of the conceptual understanding of time. Today, he attempts to understand the different methods people have devised over time in order to accurately estimate the age of our planet, starting with James Ussher, the 17th century Irish archbishop who attempted to figure out the age of creation by adding and tracing back all the generations mentioned in the Bible.

Ussher's astonishing conclusion was that time itself began the 21st of September, 4004 BC. Although often ridiculed both for his approach and for the inaccuracy of his results, Ussher's ambitious project, as well as the intellectual and practical obstacles he needed to overcome (such as figuring out ways to make various disparate kinds of calendars compatible), deserves our admiration and respect.

Of course, Ussher's results are orders of magnitude wrong, but where are the clues to the age of our planet? Believe it or not, they are everywhere: inside your own body and that of all biological organisms, on the ground you walk on, and even in outer space. The question then becomes, which are the right clues and what do they tell us? The answers might surprise you...

I wonder whether those 200 million year-old bacteria are going WTF?...
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