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From: stewart@ihldt.UUCP (R. J. Stewart)
Newsgroups: net.astro
Subject: Re: moon on the horizon - question.
Message-ID: <2265@ihldt.UUCP>
Date: Fri, 2-Mar-84 09:53:05 EST
Article-I.D.: ihldt.2265
Posted: Fri Mar  2 09:53:05 1984
Date-Received: Sat, 3-Mar-84 11:06:07 EST
References: <1690@hplabsc.UUCP>, <694@ihuxq.UUCP> <225@ucbvax.UUCP>
Organization: AT&T Bell Labs, Naperville, IL
Lines: 18

> So naturally when the moon is at the horizon (a closer point,
> according to the mind) it looks bigger, since closer objects are
> bigger.

The way I understand, the effect is just the opposite from this.  When
the moon is high in the sky, there is nothing to compare it to.  The
mind tends to just pick a frame of reference for it.

On the other hand, when the moon is close to the horizon, the mind says
something like: "Gee, the moon is farther away than that building, and
that tree, and everything else I can see.  Since it's so far away, it
must be really big to cover that much of the sky".  In other words, for
a constant apparent size, the perceived size gets larger as the
perceived distance gets greater.

This effect can be created in the laboratory in several different ways.

Bob Stewart