Find a term from the labs, understand the process behind it, and see how it appears in the landscape. Each entry connects an explanation with a real observation and a model you can explore.
Term
Penumbra
The part of a shadow where the light source is only partly obscured. On the Moon it produces subtler dimming than the umbra.
What to look for
NASA Kennedy Space Center photograph, 20 January 2000. Earth's shadow falls on the Moon; sunlight filtered through Earth's atmosphere gives the eclipsed surface a reddish colour.
