Optical illusions occur when what the eyes see conflicts with what the brain expects.
75
Pumice is the only rock that floats on water.
14
A 'jiffy' is an actual unit of time for 1/100th of a second!
66
Airports that are at higher altitudes require a longer airstrip due to lower air density.
39
The average temperature at 40,000 feet above sea level is -60 F.
56
Blue eyes are a genetic mutation. Before the mutation occured, all humans had brown eyes.
89
In zero gravity, a candle's flame is round and blue.
16