The shadow cast by the Earth on the Moon during an eclipse is round shaped.

Eclipses occur when one celestial body moves into the shadow of another. In the case of a lunar eclipse, the Earth moves between the Sun and the Moon, casting a shadow on the Moon's surface. This shadow is responsible for the darkening or reddening of the Moon during an eclipse.

1. The Earth's Shadow
The Earth's shadow has two parts: the penumbra and the umbra. The penumbra is the outer part of the shadow and is not completely dark. It gradually gets darker towards the center, where the umbra begins. The umbra is the inner part of the shadow and is completely dark.

2. Shape of the Earth's Shadow
The shape of the Earth's shadow is round. This is because the Earth is a spherical shape, and when it blocks the Sun's light, it creates a circular shadow. The curvature of the Earth determines the shape of the shadow.

3. Projection onto the Moon
When the Earth casts its shadow onto the Moon during a lunar eclipse, the round shape of the shadow is projected onto the Moon's surface. This is why during a total lunar eclipse, we see a perfectly round shadow covering the Moon. The shadow may appear slightly distorted due to the irregularities on the Moon's surface, but overall, it retains its round shape.

4. Variation in Shadow Size
The size of the Earth's shadow on the Moon can vary during different stages of an eclipse. At the beginning and end of a lunar eclipse, when the Moon is partially in the Earth's shadow, the shadow may appear slightly elongated. However, during a total lunar eclipse, when the Moon is fully within the umbra, the shadow takes on a more distinct and round shape.

In conclusion, the shadow cast by the Earth on the Moon during an eclipse is round shaped. This is due to the Earth's spherical shape and the projection of its shadow onto the Moon's surface.