Understanding Orbits

What is an Orbit?

An orbit isn't magic - it's continuous falling. When you're in orbit, you're constantly falling toward Earth, but you're also moving sideways so fast that you keep missing the ground.

Imagine throwing a ball. It curves down and hits the ground. Now throw it faster - it goes farther before hitting the ground. If you could throw it fast enough (about 7.8 km/s at 400 km altitude), it would curve down at the same rate that Earth curves away beneath it. That's an orbit!

The Magic Speed

At any given altitude, there's a specific speed you need to maintain orbit. Too slow, and you spiral down. Too fast, and you fly away.

For low Earth orbit (about 400 km altitude), that speed is about 7.7 km/s or 27,700 km/h. That's fast enough to circle the entire Earth in just 90 minutes!