Orbital Motion
Why planets keep circling
Celestial mechanics
Move the universe to see how it works
Orbits, tides, slingshots, gravitational lensing. Change the numbers, watch the sky respond, and see the formula behind it.
- 12 interactive modes
- 74 languages
- No sign-up needed
12 simulations you can touch
Every mode runs live. Drag a slider and the sky responds immediately.
Orbits and flight
Kepler's Laws
Ellipses and equal areas
Hohmann Transfer
Change orbits on little fuel
Gravity Slingshot
Speed up using a planet
What gravity does
Universal Gravitation
See gravity as arrows
Three-Body Problem
Three stars and chaos
Lagrange Points
Five places where forces balance
Tidal Force
How tides rise and fall
Roche Limit
Where tides tear a moon apart
Observation and Earth
Exoplanet Transit
Find planets by dimming
Gravitational Lens
Light bent by gravity
Axial Precession
Earth's slow axis wobble
How it works
Choose a phenomenon
Pick from orbits and flight, what gravity does, or observation and Earth.
Change the numbers
Adjust mass, distance, speed and tilt, and watch the result as it moves.
Read the reason
The explanation sheet shows the formula and what it means in the real universe.
Made for learning
Live simulation
Numerical integration runs in real time, with key values on screen.
Real formulas
Universal gravitation, Kepler's laws, transfer orbits and tides, explained simply.
Works offline
Everything except ads works without a connection.
Phone and tablet
Layouts fit large screens, landscape, and light or dark themes.
Start moving the planets
Free with a banner ad. No in-app purchases.