@NutjobBob Just because there's no light it doesn't mean the molecules disappear. Things don't stop existing because you can't see them...or do they... (something something matrix cat something something) .
Yeah, I picked up on that a about ten minutes ago xD
However, if we take the line as simply a perceived line, such as the results already suggested (As if we're dealing with a singular grouping of molecules that we are trying to make longer without altering them, it's impossible.), Thus, in a room without lighting, the perceived line disappears and to a viewer it would appear that the line doesn't exists, an extension of this of course is that the line becomes all consuming due to the lack of lighting itself.