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.
Meteors and meteorites have fascinated human beings for ages, but have you managed to turn your fascination into some hardcore knowledge? Wishing on a star isnâ€™t going to help you now.
Every day, astronomers unravel a little more of the universe's inner workings, but the jury is still out on 95 percent of its contents.