What causes moonbeams?

Moonbeams are caused by the reflection of sunlight off the surface of the Moon. When the Moon is illuminated by the Sun, the light reflects and scatters, creating the appearance of beams of light radiating from the Moon. This effect is enhanced when the Moon is low in the sky, as the light passes through more of the Earth's atmosphere, which can scatter the light and create a shimmering effect. Thus, moonbeams are essentially a visual phenomenon resulting from the interaction of reflected sunlight and atmospheric conditions.