* Observation: We can see the moon is round with our own eyes! Its shape is clearly visible, even without any special equipment.
* Lunar Phases: The changing phases of the moon (new moon, crescent, full moon, etc.) are caused by the sun illuminating different parts of the moon as it orbits the Earth. These changing phases only make sense if the moon is a sphere.
* Shadows: During a lunar eclipse (when the Earth blocks the sun's light from reaching the moon), the Earth's shadow falls on the moon. The shape of the shadow is always round, regardless of the moon's phase. This proves the moon is spherical.
* Spacecraft Images: Images taken by spacecraft orbiting the moon and even landing on its surface clearly show that it's a round object.
The moon isn't perfectly round, however. It's slightly flattened at its poles due to the Earth's gravitational pull. But it's still much closer to a sphere than it is to any other shape.
