Penumbra
The penumbra is the pale outer part of a shadow, where the light source is only partly blocked.
Full definition of Penumbra →:: COMPARE ::
PenumbravsUmbra
The short answer
Umbra: source completely blocked, total eclipse, narrows with distance. Penumbra: source partially blocked, partial eclipse, widens with distance. They're the same shadow's core and fringe, and they behave in opposite directions as they travel.
Side by side
| Aspect | Penumbra | Umbra |
|---|---|---|
| Source is | Partly blocked | Fully blocked |
| Eclipse | Partial | Total |
| With distance | Widens | Narrows |
| Coverage | A continent | A track |
What each one means
Umbra
The umbra is the dark inner core of a shadow, where the light source is blocked completely.
Full definition of Umbra →