Columbia University has developed an artificial tree that passively soaks up carbon dioxide from the air using "leaves" that are 1,000 times more efficient than true leaves that use photosynthesis.
15
Pumice is the only rock that floats on water.
14
A cubic yard of air weighs about 2 pounds at sea level.
31
When you walk down a steep hill, the pressure on your knees is equal to three times your body weight.
199
Nylon is made from coal and petroleum.
42
A cesium atom in an atomic clock beats over nine billion times a second.
43
Scientists aren't sure what color dinosaurs were.
312
Iron weighs more after it rusts.
68