Optical illusions occur when what the eyes see conflicts with what the brain expects.
75
The average sperm cell swims at 8 inches per hour.
4
Bats sleep 18-20 hours per day.
5
A comet's tail always points away from the sun.
2
The smell of freshly cut grass is actually a plant distress call.
31
Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
It would take about 1,200,000 mosquitoes to fully drain the average human body of blood.
217