So, tonight is the so-called Supermoon, when the Moon happens to be full at the same time it's at perigee, the point in its orbit closest to the Earth. This makes it somewhat larger and brighter than normal, and that's getting a lot of attention in the press. I pointed out a few days ago that in reality, you almost certainly won't notice the difference between this full Moon and any other, mostly because the difference is small, and our eyes and brain are terrible at judging things like that without something to directly compare it to. I was thinking about this last night as I watched the almost-full Moon rise in the east (which, I'll add, ironically looked huge due to the Moon Illusion!), and thought of something that might help illustrate this last point.
Monetary eclipse Imagine you go outside tonight to look at the full Supermoon rising in the east. Imagine also you're holding a US dime in your hand (if you live in another country, feel free to substitute your local currency, but beware of the math; hang on a minute to see). Let me ask you this: How far away would you have to hold the dime so that it appears as big as the Moon to you? A few inches? A foot? (Convert to metric if you wish). Go ahead, guess! ... OK, ready? [Answer is below the fold so as not to spoil it.] Here's the answer: 6 feet. That's right: unless you're 12 feet tall, you literally cannot hold a dime in your hand far enough away to be as small as the Moon in the sky!
