Here's why:
* Umbra: This is the innermost and darkest part of the shadow cast by the Moon. It's formed where the Moon completely blocks out the Sun's light. Observers within the umbra experience a total solar eclipse, where the sky becomes dark, stars become visible, and the Sun's corona (outer atmosphere) is visible.
* Penumbra: This is the outer, lighter part of the shadow where the Moon only partially blocks the Sun's light. Observers within the penumbra experience a partial solar eclipse, where the Sun appears as a crescent or a disk with a bite taken out of it.
So, while both the umbra and penumbra are parts of the shadow, the umbra is the darkest because it receives no direct sunlight.
