Question: why is the moon sometimes out during the day?

Angus Cook answered on 16 Jun 2016:

(Excellent name)

The idea that the Moon only comes out at night is (I’m sure you know) a myth. It’s a nice popular one, because it would make a kind of tidy sense if you had the Sun come out in the day, and the Moon come out at night.

Tidy, but not correct, unfortunately.

The ONLY thing that makes day and night is the Sun, the moon is NOT involved. When the Sun’s out we can see its light all around us, everything nice and bright and warm (ignoring rain or other weather…), and we call this ‘day’. When the Sun’s gone it’s darker, and usually colder, so we call this bit ‘night’.

Because the Moon’s not involved in the day-night cycle, it can kind of pop up wherever it wants (I mean, it’s still confined by its own orbit, but that orbit doesn’t have to line up with the rotation of the Earth, which is what sets the length of the day and the night). This is why you can see it sometimes in the day, sometimes at night.

Of course, it’s far easier to notice at night because the Sun’s not around to out-shine it.