Question

what is umbra

Answer 1

The umbra (Latin for "shadow") is the innermost and darkest part of a shadow, where the light source is completely blocked by the occluding body. An observer in the umbra experiences a total eclipse. The umbra of a round body occluding a round light source forms a right circular cone; to a viewer at the cone's apex, the two bodies are equal in apparent size. The distance from the Moon to the apex of its umbra is roughly equal to that between the Moon and Earth. Because the Earth is 3.70 times wider than the Moon, its umbra extends correspondingly farther, roughly 1.4 million kilometers.