How do satellites stay in orbit without falling down?

Satellites stay in orbit because they're moving sideways so fast that as they fall toward Earth, the planet's surface curves away beneath them at the same rate. They are essentially in a constant state of falling, but continuously missing the Earth. This balance between their forward velocity and gravitational pull keeps them in a stable path. For a low Earth orbit, a satellite needs to travel roughly 17,500 miles per hour to maintain this balance. If it slows down, gravity wins and it falls back to Earth. If it speeds up, it moves to a higher orbit. The near-vacuum of space means there's almost no air resistance to slow them down, so they can maintain this speed indefinitely.