2D Orrery
Flat map view
Side-by-side Heliocentric and Tychonic views, date picker, and epicycle trails on the Tychonic panel.
Work in progressSpace view (3D)
Early preview — orbit in 3D. The 2D orrery is the main demo for now.
The core idea
Heliocentric: the Sun is at the center; planets orbit the Sun.
Tychonic (geo-centered): Earth is at the center; the Sun and planets move around it.
These sound like opposite worlds — but for any observer standing on Earth, both models predict the same direction and distance to every planet. The demos prove that by computing one set of positions, then redrawing them in either frame.
What changes vs. what stays the same
- Same: every planet's direction and distance from Earth, retrograde loops, conjunctions, phases, tables of positions — the whole sky.
- Different: which body sits at the origin, how the diagram is drawn, what you take to be "at rest" philosophically.
Heliocentric: Sun fixed at origin; planets at (x, y) from the Sun
Tychonic: Earth fixed at origin; Sun at (−xₑ, −yₑ); planets repositioned
Earth → any planet: same vector in both models ← that is the observation
How to use the demos
- Open the 2D orrery — Heliocentric and Tychonic panels side by side at the same moment.
- Watch the observation panel — every planet's angle and distance from Earth stay the same in both panels.
- Enable Trails — epicycle paths on the Tychonic panel, the loops Tycho Brahe's model was built to explain.
- Watch the observation panel — every planet's angle and distance from Earth stay the same when you toggle models.
- Speed up time — retrograde motion appears as backward loops on the trail, not as planets literally reversing.