Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
The average sperm cell swims at 8 inches per hour.
76
For most people, no matter how hard you pinch the skin on your elbow with your fingers it doesn't hurt.
515
After age 30, the brain begins to lose about 50,000 neurons per day - shrinking the brain .25% each year.
55
Every year your body replaces 98% of your atoms.
119
When you get goosebumps and your hair stands, the hair helps to trap air, making you feel warmer by keeping in your body heat.
46
If you are cold you are more likely to be hungry because you use energy to keep warm.
143