From: CWandke@aol.com
A poster in sci.astro asked why the moon appears larger on the horizon than at the zenith. The following responses appeared:
(excerpts, revised)
From: brad@looking.UUCP (Brad Templeton) Date: 16 Aug 87 960701 The real truth about the moon Newsgroups: sci.astro
Actually the moon appears so much larger because it is almost twice as close to you when on the horizon as it is when it is overhead.
When the moon is on the horizon, it is attracted by all the mass of the Earth you see running from where you are standing to the point on the horizon where you see the moon. Up above you, there is no mass of Earth between you and the moon, so the force is less.
The massive force brings the moon much closer when it rises and sets. As it gets higher, the force is less, and it moves further away. Then it comes back in again.
The moon is actually closest to the Earth when below the horizon, only you can't see it then. Those of us on the other side of the Earth actually get a really good view. Apollo reached the moon by leaving from the other side of the Earth when the moon was close.
From Astronet