[Avodah] sun and moon

[Lampel]

On 8/24/2011 12:05 PM, R. Zev Sero wrote:
> there are mekoros that say the moon still has its own light, that only shines when it's
> stimulated by sunlight.
Here's an interesting piece that shows things are not as simple as 
popular opinion thinks (from 
http://www.universetoday.com/75891/why-does-the-moon-shine/):

"The real mystery is why does the moon reflect at all. Like most objects 
in space, the Moon possesses a reflective characteristic called albedo. 
Albedo is how well an object reflects light. This characteristic seems 
pretty straight forward. Material like ice and snow have very reflective 
albedos. Land and Greenery have very low reflective albedos. *What makes 
the moon so interesting is that it has the same Albedo as coal. That 
means that it has almost no reflective quality up close.* So when the 
Apollo mission were going on the Moon was actually a pretty dark place. 
This only makes sense, because of the large lava plains that it has.
"The reason why the moon still seems so reflective is because of an 
interesting effect called the opposition effect. The opposition effect 
basically states that certain types of non reflective surfaces lose 
their shadows when directly in the line of sight of the light source 
shining on them. This why a road at night lit by head lights will seem 
to brighter than it is. The reason that moon does this so well is the 
loose regolith that covers most of its surface. The opposition effect is 
strongest for the moon when it is directly in the opposite position of 
the Sun in relation to the Earth."

Zvi Lampel
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