Yawns are more contagious among people with closer relationships.
163
The adult human brain weighs about 3 pounds (1,300-1,400 g).
99
The average person's skin weighs twice as much as their brain.
131
The human brain uses approximately as much energy as a 10 watt light bulb.
120
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
Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
For most people, no matter how hard you pinch the skin on your elbow with your fingers it doesn't hurt.
515