Quote from bobcathy1:
Gordon...
A full cycle of sleep is 45 minutes.
If you slept only that long, you are able to get up and function. Probably have to do it a few times in 24 hours. A doctor told me this. Guess he learned this when he was an intern.
When I was a teenager, I could go days without sleeping with no problem at all. My Mom has never grown out of this and she is 72. My dad is nearly 80 and he always slept a lot.....we all think he doe it to get away from my mom bugging him.
So the answer is 45 minutes.
Actually, normal sleep involves four distinct stages of sleep including REM. When we fall asleep we spend a majority of our time in the third level. This is the deepest level of sleep. REM sleep is considered level 4 in some textbooks but it is really a stage where we are very close to being awake. REM (Rapid Eye Movement), is also where our dreams take place.
This entire cycle gets repeated throughout the night with progressively longer periods spent in REM sleep. This is why you'll get a long of dreams the longer you sleep.
Also, if you wake up 2 hours before normal, do a crossword puzzle (or something other intellectually challenging) and then go back to sleep, you will have extremely vivid dreams and possibly OBE's.

