Moon During the Day
Date: 1999 - 2000
Why does the moon appear during the day?
For the same reason that you can see anything during the day - the sun
shines on it, and you can see the light that reflects off it.
So why can you sometimes see the moon during the day, but not the stars?
The reason is that the sky is bright, and washes out the faint light from
stars. The moon, however, is much brighter in the sky than the stars are,
so sometimes you can see it through the sky.
It turns out that sophisticated cameras CAN see the stars during the day.
They have to be selective enough to tell the difference between the normal
blue sky and blue sky with starlight added to it. Our eyes just aren't good
enough to tell the difference.
Richard E. Barrans Jr., Ph.D.
PG Research Foundation, Darien, Illinois
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Update: June 2012