What makes the moon appear crescent shaped?
The Moon is a sphere illuminated by the Sun. In its crescent phase, the Moon is mostly “back lit” by the Sun (in photography terminology). If you hold a tennis ball up next to the Moon in daylight, you’ll see that it is lit exactly the same as the Moon. I’m absolutely staggered by the number of people who think that the Moon’s phases are caused by the shadow of the Earth. The _only_ time the shadow off the Earth is anywhere near the Moon is at Full Moon, when it sometimes causes lunar eclipses. Can’t people grasp basic geometry? Heck, I learned this stuff in grade 5.
