How dark should a shadow be?

Question

How dark should a shadow be? I think we've all heard that since the Moon has no atmosphere that shadows on the Moon should be totally dark. On the other hand, when viewing pictures taken on the moon, there is stuff clearly visible that's not in direct sunlight. Conspiracy theorists point this out as evidence that humans have never been to the moon. I came across this recent slide show of work being done on the ISS:

http://news.yahoo.com/nphotos/International-Space-Station/ss/events/sc/050203isspace/s:/ap/space_station#photoViewer=/080710/480/5551e08c6cbc400fa7b8877ccf03bf13

It and several other photos in the slide show have shadows with plenty of light. Explain how that's possible (on the ISS and the moon).

Answer 1

It's very simple: reflected light. The Moon, the ISS, anything, in fact, reflects light. Light doesn't just stop when it hits something, so shadows can be filled in by light bouncing off other surfaces into the area that is blocked from direct sunlight.

Answer 2

The answer is simple, you have sunlight being reflected from the earth, therefore the light in those pictures is not just coming from the direction of the sun. People often neglect the fact that light being reflected off the earth, moon, or any other celestial body is still light and will have this type of effect on those shadows.

Answer 3

No doubt because there is more then one light source. In the case of the ISS the earth is very bright and lamps are used to illuminate the working area.

On the moon, same thing: on earth one can read by the light of the moon, so the earth must be a good light source on the moon as well, despite it's half phase during the moon excursions.