It’s happened to all of us. You’re in that strange netherworld between awake and asleep when suddenly…ahhhhh…you’re falling! Then you jerk awake and maybe even experience a quick hallucination or two. (Then you either fall asleep for real or give up and watch that Hair-in-a-Can infomercial for the hundredth time.)
What’s going actually has a name, and it’s really common. It’s called the hypnic jerk. When you wake up suddenly for whatever reason, your brain reacts by searching for stability under your hands and feet. It doesn’t detect it, of course, because you’re probably lying down. This leads to a panic reaction similar to falling.
Other scientists think that the brain is just simply misinterpreting your muscles relaxing and settling as falling. Oh, and as far as those hallucinations? They’re normal too and are a result of another misinterpretation by your ever-awake brain thinking it sees something that isn’t really there.