Would planets still orbit the sun if there was no gravity

Some visitors to the gheens science hall & rauch planetarium at the university of louisville in kentucky recently asked why the planets go around the sun. most people take this fact for granted, but the answer involves many interesting ideas and important concepts. i'll touch on a few.

first of all, saying the planets go around the sun is just another way of saying the planets are in orbit around the sun. a planet orbiting the sun is like the moon or a nasa satellite orbiting earth. now why does a planet orbit the sun and not the sun orbit the planet? the lighter object orbits the heavier one, and the sun is, by far, the heaviest object in the solar system. the sun is 1000 times heavier than the largest planet, jupiter (which also happens to be my favorite planet), and it is more than 300,000 times heavier than earth (another planet i am very fond of). in the same way, the moon and satellites we launch orbit earth because they are so much lighter than our planet.