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.
73
The average sperm cell swims at 8 inches per hour.
76
Coughing can cause air to move through your windpipe faster than the speed of sound - over a thousand feet per second!
197
The human brain is very soft, having a consistency similar to soft gelatin or firm tofu.
13
It would take about 1,200,000 mosquitoes to fully drain the average human body of blood.
217
Poor eyesight (myopia) is associated with higher IQ.
232