So, I was just outside looking at the moon. Looks more like a half moon tonight. EDT.
If the moon is in front of us, relative to the sun, why isn’t curve rounder given that the earth is spherical?
This is not an eclipse where the earth’s shadow is cast upon the moon... it is just a crescent moon where the shape of the earth is completely irrelevant. None of the shade on the moon is cast by Earth, it’s just the part of the moon that the sun isn’t shining on at the moment. Hold up a tennis ball to a lamp... it’ll look the same when viewed from the same angle as we see the moon.
The only things interacting in the scene are sunlight and the moon. The moon would have a shady side whether the Earth is present or not.
The Earth is just providing a bit of indirect reflected light from Earth’s sunny side to what would otherwise be a starkly dark shadowed side of the moon if there was but a single light source.
Kind of like when good artists paint horses, and show a bit of light on the underbellies- this is the light that is reflected from sunlit ground or grass back up to the belly. It’s not enough to just paint the light that hits a subject from one source- an artist has to consider that light also bounces from other elements of a scene, and when it does, it often adds a hint of the color of the object it bounced off of before. If the horse is standing on green grass the reflected light will have a hint of green. If the horse is standing on exposed soil, such as iron-rich red earth, the light that bounces up onto the belly will have a bit of that oxide orange-red to it.
The dark area is the area not illuminated by the sun. In the half moon photo we are seeing the moon from 90 degrees off from the center of the illuminated side so it looks like a straight. The dark side is not from the Earth’s shadow. That happens in a lunar eclipse.