How Do Planets Stay Up In The Sky?

15/09/11

How do planets stay up in the sky?” must have been one of the first questions scientists asked when they began looking through their telescopes into space. The telescope was first introduced to astronomy in 1609 by the magnificent Italian scientist Galileo Galilei – he was even the first man to see the craters on the Moon and the rings of Saturn! But what must have he thought while gazing up at the planets, hundreds of years ago? Are these gigantic marbles floating in space? Did a wizard send them up there with a wicked spell? Or are we watching an intergalactic puppeteer’s playtime?

Discoveries by other famous scientists such as Sir Isaac Newton have helped answer this amazing mystery: The planets in our solar system all circle the sun, which holds them in a tight gravitational grip. The planets also have their own momentum which is why they spin around the sun, their orbits being a balance between gravity and the motion of the planet. If the planet’s went slower, or didn’t have their own momentum at all they would be pulled into the sun, and If they went faster, they would shoot off into deep space! The Sun is a lot bigger than the Earth (more than 100 times the size!) therefore it has a much more powerful gravitational pull. The planets don’t fall down to Earth because they are orbiting around the Sun, and not around the Earth.