Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
For most people, no matter how hard you pinch the skin on your elbow with your fingers it doesn't hurt.
515
Every year your body replaces 98% of your atoms.
119
If your DNA was stretched out it would reach to the moon 6,000 times.
256
The human brain doesn't stop developing until about 25 years old.
102
If every muscle in your body could pull in one direction, you could lift nearly 25 tons.
22
The human brain uses approximately as much energy as a 10 watt light bulb.
120