Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
Your body is creating and killing about 2.4 million red blood cells per second.
17
The human brain uses approximately as much energy as a 10 watt light bulb.
120
Poor eyesight (myopia) is associated with higher IQ.
232
The adult human brain weighs about 3 pounds (1,300-1,400 g).
99
The average person's skin weighs twice as much as their brain.
131
One human hair can support 3 ounces.
191
For most people, no matter how hard you pinch the skin on your elbow with your fingers it doesn't hurt.
515