Obamania - Do we human beings ever been able to identify the source of air, vacuum, all elements like h, he, li, be, br, etc? Are we able to identify the source of stars, sun, etc. Does it mean that it doesn’t exist?

If it is beyond the imagination and beyond our research we cannot say that it doesn't have any source, yet more research needs to be done. If we say darkness doesn't have source in terms of scientific findings then let me remind you we have till now succeed only 0.0001% or even less(just my observation) on defining any substance or its existence proportion to the whole universe/beyond galaxies. And darkness is a big topic. Go for it you will contribute something for human kind.

You can always think darkness as a universal set where light present. Without darkness there is not even a single penny value of light and I believe light doesn't exist without darkness. So getting into conclusion with 0.0001% of findings makes us insane right?

Fortunefaded - Where do you find sound in the midst of the silence right? If anybody have known the speed of silence then you would have told me before you had asked me. Nobody has defined the speed of silence so i can't tell you right now but i do believe there exists the speed of silence too. Just we need to do more research in order to relate silence with (as the speed is calculated in terms of relation like speed of anything is calculated in terms of still object where speed=distance/time don't get confused with this formula go beyond this formula you will find still object which is constantly providing you distance of an object)

Fortunefaded - do you consider sound as energy and does it have mass? Please try to do research on it. You won't be getting an answer like what is the speed of silence but i assure you that you will realize something should be there to relate silence with. Darkness is similar to it.

NightElf - Actually we were talking about the speed but you were more relating it to its presence and absence. I am totally agreed upon you regarding processing the impulse of light by our retina and giving the vision of brightness through our mind. But I am little bit disagree on absence of light means absence of everything. Darkness is what presents on the absence of light.  So physics should quantify it. What do you think?