Iron weighs more after it rusts.
68
In Arizona, a solar wind energy tower has been proposed that would generate as much energy as the Hoover Dam.
5
When you walk down a steep hill, the pressure on your knees is equal to three times your body weight.
199
Only 12,000 years ago there was a species closely related to modern humans called Homo floresiensis that had been living on an Indonesian Island. They used fire and rather advanced tools, yet were only about 3 feet tall and weighed around 25kg.
15
Balsa wood is classified as a hard wood!
41
A cubic yard of air weighs about 2 pounds at sea level.
31
In zero gravity, a candle's flame is round and blue.
16