Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
Your body is creating and killing about 2.4 million red blood cells per second.
17
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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Every year your body replaces 98% of your atoms.
119
If every muscle in your body could pull in one direction, you could lift nearly 25 tons.
22
Enamel is hardest substance in the human body.
61
After age 30, the brain begins to lose about 50,000 neurons per day - shrinking the brain .25% each year.
55