Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
The adult human brain weighs about 3 pounds (1,300-1,400 g).
99
For most people, no matter how hard you pinch the skin on your elbow with your fingers it doesn't hurt.
515
If your DNA was stretched out it would reach to the moon 6,000 times.
256
After age 30, the brain begins to lose about 50,000 neurons per day - shrinking the brain .25% each year.
55
Yawns are more contagious among people with closer relationships.
163
There are times when you're walking that the pressure on your feet exceeds your body weight, and when you're running, it can be three or four times your weight.
62
The average sperm cell swims at 8 inches per hour.
76