Yup, sleep cycles are 1.5 hours each and most humans need 5 of them. As long as you don't break out of a sleep cycle before the 1.5 hours is completed you tend

Yup, sleep cycles are 1.5 hours each and most humans need 5 of them. As long as you don't break out of a sleep cycle before the 1.5 hours is completed you tend to feel pretty awake when you do wake up, even if it's only been 3 hours.