Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
An average heart beats 100,000 times a day, pumping some 2,000 gallons of blood through its chambers. Over a 70-year life span, that adds up to more than 2.5 billion heartbeats.
73
Your heart will pump about 212 million liters in its lifetime.
26
The adult human brain weighs about 3 pounds (1,300-1,400 g).
99
If your DNA was stretched out it would reach to the moon 6,000 times.
256
For most people, no matter how hard you pinch the skin on your elbow with your fingers it doesn't hurt.
515
Chewing gum boosts your brain power.
285
It takes about 20 seconds for a red blood cell to circle the whole body.
102