When you walk down a steep hill, the pressure on your knees is equal to three times your body weight.
199
A cubic yard of air weighs about 2 pounds at sea level.
31
Iron weighs more after it rusts.
68
Hot water can freeze faster than cold water.
181
The most expensive material on the planet is antimatter - worth $62.5 trillion per gram.
18
The only letter not appearing on the Periodic Table is the letter "J".
180
Because heat expands the metal, the Eiffel Tower always leans away from the sun.
79
In 1999, Harvard physicist Lene Hau was able to slow down light to 17 meters per second and in 2001, was able to stop light completely.
39