Bats sleep 18-20 hours per day.
5
The human brain is more active during sleep than during the day.
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There's a love mattress that is specifically designed for couples who sleep on each other's arms.
12
Cows can sleep standing up, but they can only dream lying down.
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Some people have a "natural alarm clock" allowing them to wake up when they want. This is actually caused by a burst of the stress hormone adrenocorticotropin.
15
The record for the longest scientifically documented period without sleep is 264.4 hours (eleven days).
15