@ved55, a lot of people would be happy if you summed that article up into a paragraph.

@ Hemu, we see light because when it hits our cells in retina they generate a small electric impulse that is transferred to our brain, this impulse is interpreted differently in different brains to give us a sense of what our eyes saw.  When those retina cells don't generate electric impulse, when there is too little or no light, our brain processes the absence of such impulses, giving us an idea that its dark.
I am not saying that absence of matter or energy is insignificant, such absence is not quantifiable in standard physics.


One more random thought:
would there still be darkness if there were no people or any other intelligent minds that observe the absence of light?? I am asking this because no matter how dark we think it is, there is always some light, maybe a single ray from a distant star that is passing by the area under observation.


PS: check out the wikipedia article on Darkness,
http://en.wikipedia.org/wiki/Darkness
and look at the pic of a chess board and a cylinder to the right, its kinda cool.