Subject: Re: 4/11 *Black Box*
From: jak@ceres.physics.uiowa.edu
Date: 1991-04-15, 15:36
Newsgroups: alt.tv.twin-peaks

In article <1991Apr15.153824.23535@watserv1.waterloo.edu>, alternat@watserv1.waterloo.edu (Ann Hodgins) writes:
> >   
> > Actually this has bugged me for a while.  What makes the moon light?  -
> > reflecting sun light. What causes the dark side?  - as far as I know it
> > is the earth interfering with the light getting to the moon. Technically
> > not an eclipse I guess, but very similar in effect - one planetary body 
> > interfering with the light coming off another body.
> >  
> > ann

  The "dark side of the moon" is sort of a misnomer. The moon rotates on
its axis once for every trip around the earth. This has the effect that
the moon keeps one face to the earth at all times. The other side gets
sunlight, we just don't see that side. As an illustration, put a chair
in the middle of a room, and say the sun is the north wall. You are the
moon. Now, walk around the chair slowly, turning so that you always keep
the front of your body towards the chair. After one trip around the chair,
you have turned once on your axis. You have faced all four walls in the
room, all while keeping the same face towards the chair/earth. Also,
your back, "the dark side", has faced the north wall, the "sun". This
is just what the moon does.

Jeff Kouba
Dept. of Physics and Astronomy
University of Iowa
INET: jak@ceres.physics.uiowa.edu