Tuesday, November 15, 2016

How big does the moon look?

Yesterday at his Bad Astronomy blog Phil Plait posted So, About Today’s Supermoon... and posed a question:

“The Moon is pretty small on the sky, far smaller than you think. Let me ask you this: If you held up a dime, how far away from your eyes would it have to be to appear the same size as the Moon?  Here’s the answer, and it may surprise you.”

It’s a trick - that dime would have to be six feet away, but your arms aren’t that long. For me that brought to mind the title from a 1976 Broadway musical, Your Arms Too Short to Box with God.

My arms are about two feet long, so instead of the 0.705-inch diameter for a dime I’d need to hold up something almost three times smaller, like a paperclip. The comparison is a good example of how to describe a number in a way that a nontechnical audience can easily understand.

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