system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - What is the "falling thing" people apparently experience when trying to sleep?

I keep seeing it popping up, whether that be in memes or comments. I don't think I have experienced this ever. Is this some sort of genetic thing? I tried searching it on Google, and the first result mentioned something like 

> What causes falling sensation while sleeping is the natural disengagement of the astral body

- and I just stopped reading when it mentioned astral body. Is this just another thing we have no idea about or is there something to this?
gpt
Our body relaxes our muscles when we sleep so we don't act out our dreams, however if your body relaxes all it's muscles just before you pass out it can feel like you're falling, which jolts you awake again.