Pebble, a smooth, rounded stone usually less than 2 inches (64 mm) in diameter. (A larger stone of this type is called a cobble, or cobblestone.) Pebbles are fragments of any kind of rock that have become worn by rubbing together in rivers or on beaches. A loose accumulation of pebbles is called gravel. Conglomerate is rock composed of pebbles cemented together.
He is famous for a phrase he never said, for wearing turtlenecks and for hosting the original 'Cosmos' TV series. As enthusiastic about the stars as he was about marijuana, Carl Sagan led a very surprising life. Here are 10 cool facts.
One was a celebrated author, the other a famed physicist. What the two shared was a public exposure of their religious beliefs. Big E had an on-again, off-again relationship with God, while C.S. was an avowed atheist during his early years.