When you walk down a steep hill, the pressure on your knees is equal to three times your body weight.
199
Iron weighs more after it rusts.
16
The hair of an adult man or woman can stretch 25 percent of its length without breaking.
116
In Arizona, a solar wind energy tower has been proposed that would generate as much energy as the Hoover Dam.
5
4.5 pounds of sunlight strike the Earth each day.
27
The Earth's atmosphere weighs about 5.5 quadrillion tons.
108
Optical illusions occur when what the eyes see conflicts with what the brain expects.
75
One barrel of petroleum holds 42 gallons.
20