SEIRAKU - Celestial Mechanics

SEIRAKU is a visual learning app that teaches celestial mechanics by letting you move it. Why do planets keep circling instead of falling? Why can't we predict three stars? How does the Moon move the tides? Move a slider and the bodies respond at once, with their results updating alongside. The formulas in your textbook connect to motion you can see. [Orbits and flight] - Orbital motion: central mass and circling planets - Kepler's laws: ellipses and equal areas - Hohmann transfer: two burns to change orbits on little fuel - Gravity slingshot: speed up using a planet [What gravity does] - Universal gravitation: see the field as arrows and drop in particles - Three-body problem: the figure-8 orbit and chaos - Lagrange points (new): five places where forces balance, and their stability - Tidal force: how tides rise and fall - Roche limit (new): the distance 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 wobble and the changing pole star [Features] - Every mode responds live when you change a value - An explanation sheet shows each formula and what it means - Everything except ads works offline - No sign-up. Works on phones and tablets, in landscape, with light and dark themes - Available in 74 languages For classrooms, self-study and anyone curious about space. Free with a banner ad. No in-app purchases. The simulations are simplified models for education.