The moon, of course, is not a fixed distance for the earth. This is most readily apparent in autumn (northern hemisphere); closest approach is typically 75 to 90 minutes before moonrise, so you won't normally be able to see it, but you will be able to see the moon get smaller as it comes up over the horizon and rises into the sky.
But if you could see closest approach, under the right conditions, the effect can be quite spectacular. This image, taken with a special camera that shows light not normally visible to the human eye, shows the impact of the moon against the ozone layer.
If you look carefully, you'll see bands of shading showing the waves radiating outward from the impact - much like you would see dropping a stone into a puddle. The effect isn't quite the same (the moon doesn't actually drop through, puddles aren't round, and ozone (O3) being inherently symmetric, has a characteristic flow that differs from the lopsided H2O molecule.
If you have a head for the math, Phil Plait describes this in even more detail over at Bad Astronomy.
September 8, 2008 10:53 PM
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