Twentieth-century American physicist John Archibald Wheeler (b. 1911) coined the term black hole to describe a collapsed star whose gravitational field is so intense that not even light can escape from it.
The first leap year was 46 B.C. It was then that the Julian calendar of 365.25 days was adopted. The calendar required that an extra day be added every fourth year.
The earth moves at 66,641 miles per hour around the sun.
Brass is an alloy of copper and zinc. Bronze is a more durable mixture of copper and tin.
Glass is generally made of three components: silica, in the form of sand; an alkali flux, such as soda or potash, which promotes fusion; and lime, which stabilizes the mixture. In the process of being heated and then cooled, glass loses its crystalline nature and becomes an amorphous but rigid substance. Like a solid, it…
A wave breaks when the water that supports a wave is only about 1.3 times as deep as the wave is high. At that point, the water at the crest is moving faster than the water below. This condition commonly occurs in shallow water at the shore, but it may occur farther off if the…