Called solar system because Sun is biggest and heaviest. Solar means sun planets revolve about (travel in circles around) the sun path a planet travels is called its orbit earth is the 3rd closest planet to the sun all the planets go around in the same direction (like clockwise or counterclockwise), in roughly the same plane, but at different speeds planets close to sun move fast, far out move slower closer a planet is to the sun, the hotter it is, more or less.