Re: Moon Shine

Date: Thu Feb 22 2001 - 19:28:57 MST

Ian Goddard wrote:
> So (phew... finally to the question), anyone know more about this?
> Would this effect itself constitute evidence of being on the moon
> (as opposed to only being an effect that produces an "anomaly")?

It seems like I've heard about this being noted by astronomers. The
moon is brighter at full moon than what you would predict if you had
uniform reflectance in all directions.

According to, "The Full
Moon is about a factor of 10 times brighter than the Half Moon phase."

According to,
after several pages of calculus assuming "the surface brightness appears
the same for any direction relative to the surface normal", we find,
"One interesting thing I found that comes out of this is that the phase
factor is 1 for full phase and 1/pi for quarter phase which means the
planet is over 3 times brighter when it is full compared to half full."

So according to this calculation (which I didn't try to verify),
uniform reflectance predicts that a full moon will be pi times as bright
as a half moon, while observations show a much larger factor of 10.
This would suggest that the moon's surface does preferentially reflect
light back in the direction it shines from, since during a full moon we
are looking at the moon from the same direction as the sun.


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