There was a listener question on a science podcast recently that asked about how the temperature changed on the moon during the recent solar eclipse.

They almost got what a solar eclipse was, but not quite. During a solar eclipse, the moon gets between the sun and the earth, blocking the light getting to the earth and casting a shadow on the earth. The side of the moon facing the earth is completely dark because the thing that normally lights it up (the sun) is completely behind it. But, the back side of the moon is getting full sun and just as hot as normal.

I think part of the problem with understanding all this is that the sun is just so insanely bright. Like, it's a bit hard to believe that the full moon is so bright just because it's reflecting sunlight. It's also amazing that the "wandering stars" (planets) look like stars when they're just blobs of rocks or gases that are reflecting the insanely bright light of the sun.

It's amazing if you think about it. Light comes out of the sun in every possible direction. A tiny fraction of it hits the surface of Mercury, and only some of that light is reflected back out. The light reflected from Mercury goes in almost every direction. A tiny fraction of it hits the earth. But, even with that indirect bounce, it's bright enough to see with the naked eye.

Answer: Light travels in straight lines (well, for this purpose) and the moon is roughly an opaque sphere. Maybe you could see it with earthshine, but I get the impression the corona is still much brighter.

I've heard dumber.

A solar or lunar eclipse?