Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18
The human brain doesn't stop developing until about 25 years old.
102
One human hair can support 3 ounces.
191
Your thumb is about the same size as your nose.
124
If you are cold you are more likely to be hungry because you use energy to keep warm.
143
Staying awake for 17 hours is the same for your body as drinking 2 glasses of wine.
193
Coughing can cause air to move through your windpipe faster than the speed of sound - over a thousand feet per second!
197