What is/What causes the strange "falling" sensation during a dream or while falling asleep?

Question

What is/What causes the strange "falling" sensation during a dream or while falling asleep?

Answer 1

Falling? I some times get a floating sensation but never falling.

Answer 2

It's called a 'hypnic jerk' It's nothing to worry about. A lot of people do get this and it's most common with people who suffer from sleep deprivation. You can read more about it on the website below.  

Answer 3

Im not sure what causes that, but its usually associated with a myoclonic jerk - which is that huge twitch you get when you 'hit the ground' - i've almost broken a toe kicking my legs out during those :P

Answer 4

If you're talking about that thing that happens just as you feel you've JUST gone to sleep & it shakes/scares you back to reality, I get that on a rare occasion.  Always thought of it as rolling off a roof.   My mom said she got it too.  Someone said it's the beginning of astral projection or something.  I really don't know what it is, but in my experience, if it just occasionally, it's nothing to worry about.