Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
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
One human hair can support 3 ounces.
191
Our eyes are always the same size from birth, but our nose and ears never stop growing.
266
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
Dogs can be trained to identify the scent of lung cancer long before symptoms develop.
190