You asked us, "What keeps satellites from falling out of the sky?"
Over the last half-century, more than 2,500 satellites have followed the first one into space. What keeps them all afloat? It is a delicate balance between a satellite's speed and the pull of gravity.
Satellites are basically constantly falling. Crazy, right?
They fall at the same rate that the curve of the Earth falls away from them if they're moving at the right speed. Which means instead of racing farther out into space or spiraling down to Earth, they hang out in orbit around the planet.
Corrections are often needed to keep a satellite on the straight and narrow.
Earth's gravity is stronger in some places than others. Satellites can get pulled around by the sun, the moon and even the planet Jupiter.
You would think gravity was enough to deal with. But, satellites in low earth orbit such as the Hubble Space Telescope can also get pulled out of their orbit by drag from the atmosphere.
Not to mention the ongoing game of Frogger that satellites have to play. That's so they can avoid space junk and other high flyers.