Re: Why does the moon appear larger when it is just rising?

It's simply an illusion! Your brain interprets the Moon as large when it has nearby foreground objects (such as mountains) for reference. When it is high in the sky with nothing nearby, there is nothing to compare it to, except the vast expanse of the starry night, so your brain interprets it as small. But really, the Moon is not changing in size.

You can verify this by holding an object at arms length, and comparing its size with the Moon's at different times -- when it is in different places on the sky. (A fun question to answer, or stump your friends with, is "What object, held at arm's length, would best represent the apparent size of the Moon? A mustard seed? A pea? A coin? A dinner plate?)

Regards, Aaron

p.s. The Moon's distance to the Earth does change over the course of a month, and I think this results in an appreciable change in its apparent size, but this is a less significant effect than the optical illusion.

p.p.s. Since you're in Canberra, you can see if this same optical illusion holds for the Magellanic Clouds -- those two fuzzy patches you can see from a dark place... let me know if you do!