Explain why the moon is always half illuminated and half dark, no matter where it is in the lunar cycle.

The easiest way I know to explain it is this:
-- Take a flashlight and a ball into a dark room.
-- Turn on the flashlight and point it at the ball.
-- Half of the ball is lighted up by the flashlight, and the other half is dark.
-- There is no way you can turn or twist the ball to make more or less than 50% of it lighted up and more or less than 50% of it dark.
Everything in the solar system ... as long as it's shaped like a ball ... is half illuminated by the sun and half dark.

Answered by AL2006 | 2024-06-10

The moon is always half illuminated and half dark because it is a spherical object and receives light from the sun on only one side at a time. As it orbits the Earth, different phases are seen based on the angle from which we observe it, but half remains illuminated at all times. This principle is true for any spherical object in space.
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Answered by AL2006 | 2025-04-10