Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
Your heart will pump about 212 million liters in its lifetime.
26
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.
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Coughing can cause air to move through your windpipe faster than the speed of sound - over a thousand feet per second!
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Your body is creating and killing about 2.4 million red blood cells per second.
17
The average person's skin weighs twice as much as their brain.
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For most people, no matter how hard you pinch the skin on your elbow with your fingers it doesn't hurt.
515
Women have about four times as many foot problems as men; lifelong patterns of wearing high heels often are the culprit.
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