A lot of people think that to get to orbit, you just go up. That’s partially true, but in reality you go up to get out of the atmosphere, and then go sideways really, really fast.

Imagine throwing a ball in the air. If you throw it straight up, then no matter how high you throw it, it just comes back down. Now imagine throwing it across the room. It falls in a curved arc, right? Now imagine throwing it so fast that it goes past the horizon. That curved arc is still there, and it’s much longer now.

Now imagine throwing it so hard that it not only goes past the horizon, it actually never hits the earth in the first place. That’s an orbit! Of course, the earth has an atmosphere, so it would slow down because of aerodynamic drag. That’s why we send rockets way upward—to get out of the air.

So a satellite in orbit is literally just falling constantly, but because it’s going so fast, it’s always missing the earth.