That would be.... DEATH.
Death is just so confusing, the concept of life disappearing, being there, and then not. I can't even fathom being dead.
(From a non-religous standpoint) I wonder if when you die, your "soul" floats away to some alternate universe where it can experience "life" once more. Maybe our souls stay here and haunt the world, making up the things we cannot understand, such as light, fire, electricity. Maybe there is nothing. Like, when we die, its just the end. BAM. Nothing. Not even the sensation of a void, or nothing. Just... the end.
Maybe we go to heaven or hell. Although I can't imagine either, or spending eternity in either. If you do go to one of those places, how do you appear? What do you experience?
Yeah, you could say this pesters my mind.