A Different Timeline of Earth

One difficulty in teaching biology was explaining the history of Earth.  How do you effectively show 4.6 billion years to 15-year-olds?  I have used timelines, football fields, and even a piano to represent deep time.  There was a great TED talk on the subject as well.

I think that I like this one the best.  The details would be hard to show, but everyone would understand it.  Just use your arm!

It would be like a built in cheat sheet.  Everyone can bring their arm to the test.  I don't know if it would work, but it is an interesting way to think about time.