Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
Oxygen, carbon, hydrogen and nitrogen make up 90% of the human body.
118
Every year your body replaces 98% of your atoms.
119
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
It would take about 1,200,000 mosquitoes to fully drain the average human body of blood.
217
The adult human brain weighs about 3 pounds (1,300-1,400 g).
99
Poor eyesight (myopia) is associated with higher IQ.
232