Here's why:

* The sun is always on the opposite side of the Earth from the moon during the night. When it's nighttime in one part of the world, the sun is shining on the other side of the planet.

* The moon reflects sunlight. We see the moon because it reflects the sun's light. If the sun were behind the moon, the moon would be in darkness.

What causes night?

Night occurs because the Earth rotates on its axis. As the Earth spins, different parts of the planet face the sun. When a particular location faces away from the sun, it experiences night.