Why Don't the Planets Fall Into the Sun?

One star holds eight planets, moons, and millions of rocks in place — all because of one force: gravity. The Sun contains 99.8 percent of all the mass in the solar system. That much mass creates a gravitational pull like an invisible string reaching across billions of miles. Picture swinging a ball on a string over your head. The string pulls the ball inward, but the ball's sideways speed keeps it from falling in. Every planet is doing exactly that — moving fast enough sideways that it keeps missing the Sun, forever. Planets closer to the Sun move faster. Mercury orbits in just 88 days. Neptune, way out on the edge, takes 165 Earth years. The layout goes: rocky planets close in, then an asteroid belt, then gas and ice giants, then the icy Kuiper Belt. Right now you are spinning at 1,000 miles per hour, orbiting the Sun at 67,000 miles per hour, and hurtling through the galaxy at 515,000 miles per hour — all held in perfect balance by nothing but gravity.