Falling around the world

An orbital playground · Three experiments · About five minutes

An orbit is a fall that keeps missing the ground. Find out what that means by launching a satellite of your own. Drag the scene to look around, or choose Follow satellite to travel beside it. Top-down gives you a diagram view.

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Your satellite starts one planet radius above the surface. Give it some sideways speed, then Launch. What happens if you launch too slowly?

A trail records where you have been. Reset gives you another attempt. Try a little more speed each time. What changes about the shape of the trail?

This satellite starts at the speed for a circular orbit. Before launching, predict where the two arrows will point a quarter of the way around.

Velocity points along the path. Gravity points inward, continually bending that path. At circular speed, the satellite keeps falling while its distance from the center stays constant. There is still gravity in orbit.

This launch starts farther from the planet. Predict: does a circular orbit here need more or less speed? Test your prediction, then turn on the predicted path to see how a small change reshapes the orbit.

In our units, circular speed is 1 / √r, where r is distance from the planet’s center. Here r is 3, so try about 0.577. A higher circular orbit needs less speed, and takes longer to complete.

These experiments use an idealized model: one spherical planet, a satellite with negligible mass, no atmosphere, and motion in a single plane. Distances use the planet’s radius; time and speed use consistent simulation units. The gold path is a numerical prediction using the same gravity model.

Change the lesson by editing altitude, speed, or vectors on an <orbit-lab> tag. Keep your question and experiment together in a Block. The literate component source explains the controls, rendering, and physics, with an experiment you can run.