An interesting theory about deep sleep came to me and I decided to elaborate it. For brain exercise and keeping my open-mindedness, I suppose.
Damn, not even exactly a theory, but bunch of abstract ideas I jotted down.


What if, while a person is in a state of deep sleep, they are actually awake in a parallel reality - and when they go to sleep there, they wake up here? Not being able to remember the other reality, when awake - in both cases.
The deep sleep reality may be too chaotic for us to remember when we're here(different laws of physics, colour spectrum, etc?). That would make the dreaming state a bridge between these realities we skip into;(since in our dreams, there is much chaos - unexplainable thoughts, actions, images - along with the familiar situations, thoughts and images we connect with certain elements of our known world). Therefore, it would make sense for people to be able to remember their dreams, but not "travels" in the deep sleep state;

If you don't sleep here, you're probably a lazy-ass, snoring-all-day dude over there. But then again, time may not exist there at all in the same way we imagine it.

Random thoughts or sudden bursts of creativity may be explained as brief glimpses(memories) of the chaotic reality.

Also, it would make sense for the soul to travel in such a way. Gaining experience, perfecting oneself and whatnot...