Napping is weird

Albert Einstein discovered Time Dilation, but I doubt even he could tell us why when we nap, sometimes we will sleep for 30 minutes and feel like we must have slept at least 6 hours, and we can sleep for over 8 hours and wake up convinced no more than 15 minutes have passed.

Then there is that whole “I just took a nap and I feel even more tired now.” thing.