Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
When you take a step, you are using up to 200 muscles.
886
Poor eyesight (myopia) is associated with higher IQ.
232
The human brain doesn't stop developing until about 25 years old.
102
The average sperm cell swims at 8 inches per hour.
76
It takes twice as long to lose new muscle if you stop working out than it did to gain it.
127
The adult human brain weighs about 3 pounds (1,300-1,400 g).
99
Your body is creating and killing about 2.4 million red blood cells per second.
17