system
Given the following post, respond as if you're commenting on Reddit:
human
Why does the shadowed part of the moon appear to be invisible even during the day? Wouldn't we see some faint part of it?
gpt
If you look closely at the moon at night, you may be able to see the circle be completed by a faint glow. That is earthshine -- sunlight that has bounced off the earth, illuminating the shadowed (night) side of the moon. 

During the day, however, our atmosphere scatters so much blue light at us that it all but drowns out the difference. While we may be able to see the difference between pitch black and earthshine-illuminated-moon-shadow at night, during the day it's just two extremely close shades of blue.