Sandman, tell me your secrets

Have you ever wondered why you can't sleep with opened eyes?

When I have my eyes opened I can often see floaters, so today out of curiosity I closed my wonderful devices of sight and tried to observe if I can still see those. So technically speaking eyes don't "shut down" when you close eyelids. The question is why do you need to close eyes in order to get sleep. Or rather why the shutters fall down when you're tired (falling asleep). Why does the body needs to do that in order to let the brain turn into regenerating mode?

And speaking of regenerating mode. Where the hello some of the dreams come from? Today I dreamt about going for a trip with friends, when all of sudden we appear need my parents' place mixed with views from The Shinning. Soon after that there was this great fog (I would like to greet Stephen King with his visions of Maine) and people started to fall asleep / unconscious. I found myself hidden with some of those people in a basement from where we observed aliens swapping real people with their hybrids.

Think this is weird? It gets better.

When I finished the alien part I found myself in my primary school waiting for some maths test. People around were my classmates from then and they looked as when we were in 8th grade. Then the teacher appeared. My maths high school teacher who taught me just for a year. With tests on the university level.

Why is this so bizarre? I haven't have watched a horror film or read such book for a longer time. No alien stuff also. Not to mention I have no idea what's happening to people from my primary school for a longer time. And to be frank - I'm not dying to discover that. So why the hell my brain conjured up such dream? And how? I haven't seen anything that would trigger such an interesting scenario.