Optical illusions occur when what the eyes see conflicts with what the brain expects.
75
Summer on Uranus lasts for 21 years.
358
A comet's tail always points away from the sun.
2
You can only remember 4 things at a time.
31
The United States has paved enough roads to circle the Earth over 150 times.
72
Switching letters is called spoonerism. For example, saying "jag of Flapan", instead of "flag of Japan".
2
Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18