Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
The human brain uses approximately as much energy as a 10 watt light bulb.
120
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 thumb is about the same size as your nose.
124
The largest cell in the human body is the female egg and the smallest is the male sperm.
682
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
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