"Vieles sieht man nicht."
Look at this, in multiple choice:
Correct translations:•Much is invisible.
•Much is not seen.
You missed 1 correct translation!
I know they mean the same, but having into mind that "invisible" has a different word directly translatable "unsichtbar", I think it shouldn't be included as a valid translation in an exercise. Otherwise, many others should be included too. Somebody's reporting, "a lot of things are not seen" was not accepted in a translation writing exercise, while "lots of things...", instead, is accepted.
Correction: as HappyTrees89 says below this, they even don't mean the same. I come back to here to add definitions. Websters International's:
1. impossible to see: not able to be seen with the eyes
2. hidden: hidden from view
3. made transparent magically: impossible to see as a result of magic or pseudoscientific processes
4. not easily noticed: not readily noticed or detected
5. unrecorded statistically: not reflected, recorded, or reported in economic statistics invisible earnings
Other sources http://m-w.com/dictionary/invisible
for Internet slang, psychology. http://en.wiktionary.org/wiki/invisible
I don't really think "invisible" and "not seen" are the same thing. The back of my head is "not seen" right now because nobody is looking at it (for me, it is hidden behind my eyes where I can't see it without mirrors, etc, and for everyone else, it is hidden behind the walls and door of the room I'm in), but it is not "invisible" because it DOES reflect light waves in the visible spectrum. Thus, the set of all "invisible" things is only a subset of all things that are "not seen" and the two terms should not be used interchangeably.
That being said, I agree that "invisible" should not be included as a valid translation in this exercise.
I would say the German sentence in this form is not translatable into meaningful English.' No one sees much' is about the best I can do, but it is not grammatical. You still need to know what you cannot see much of, a football match, or a film for example for the sentence to make sense.