There are many interesting facts about sleeping that you probably didn't know. The study of sleep is actually pretty modern, in fact most of what we have learned about it has happened in the last 25 years. With this in mind, I have put together a list of the top 10 amazing facts about sleeping. 1. The record for the longest period without sleep is over 18 days. This person experienced hallucinations, blurred vision, slurred speech and memory lapses. 2. It is almost impossible to tell if someone is really awake without medical supervision. People can have naps with their eyes open and not even know it. 3. Elephants lie down during REM sleep, but sleep standing up during non-REM sleep. 4. What is commonly known as the the "natural alarm clock" which allows people to wake up when they want, is caused by the stress hormone adrenocorticotropin. 5. The tiny rays of light from a digital alarm clock can actually be enough to disrupt your sleep cycle. 6. ...