What blocks the moon when it is half a moon?

Answer 1

The object that blocks the moon when there is a half moon is the moon itself. The moon is a sphere, so only one half of it can be sunlit at any moment. The other half is dark just because the sun is below the horizon for that half of the moon. And when we see a half moon, we are simply looking at the moon just as the line of sunrise/sunset cuts across the moon's diameter.

Answer 2

When the moon is in its half phase, the Earth, moon, and sun are not perfectly aligned, so the Earth blocks some of the sunlight from reaching the moon. This causes only half of the moon's surface to be illuminated, creating the appearance of a half moon.

Answer 3

When the moon is at its half phase, it is located at a 90-degree angle relative to the Earth and the Sun. The half of the moon facing the Earth is illuminated by the Sun, while the other half remains in shadow. The shadowed portion of the moon is not visible from Earth, giving the appearance of a half moon.