English | Deutsch
An interactive 3D simulation of the solar system that runs in the browser, with explanatory texts on three educational levels and a documented scientific basis.
Live: https://orrery3d.de
An orrery is a mechanical model of planetary motion, named after the Earl of Orrery, for whom one of the first was built in 1704. This one is digital: it computes positions from published orbital elements, and its positions are tested against JPL Horizons. The simulation always calculates physically correctly; only the display may exaggerate sizes and brightness so that small and distant bodies stay visible. How much it exaggerates is a slider setting, not a built-in compromise.
| Dataset | Source | Validity / accuracy |
|---|---|---|
| Planetary orbits | JPL Approximate Positions, extrapolated linearly | Checked 1800–2050; nominal longitude error 15″–600″ |
| Moons | Planetary Satellite Mean Elements (JPL SSD) | No separately maintained Laplace plane |
| Dwarf planets and the Pluto system | Osculating elements, JPL Small-Body Database | Pluto deviates from DE441 by up to 1.4° (1800) |
| Rotation and poles | Fixed right ascension/declination, mostly the pole official since 2015 (Archinal et al. 2018); Mars keeps the 2009 pole, Uranus/Neptune the Voyager 2 periods (1986/1989) | No precession, no periodic terms |
| Time scales | Clock shows UTC, feeds it into the orbit calculation unconverted | Valid year 1–9999; UTC used as TDB |
| Lunar eclipses | Computed, not read from tables; checked against the NASA eclipse catalog | Matches 135 of 143 umbral eclipses (1951–2050) |
| Star catalogue | HYG database (Astronexus), version 4.1, CC BY-SA 4.0 | 5070 stars to magnitude 6.0 |
| Milky Way | NASA SVS "Deep Star Maps 2020", from Gaia DR2 | SVS public domain; Gaia share CC BY-NC 3.0 IGO |
| Textures | Solar System Scope (CC BY 4.0) and NASA/USGS Astrogeology (public domain) | 14 CC BY maps, 15 public-domain maps |
| Check against JPL Horizons | JPL Horizons vector table; compares 8 planets and 5 dwarf planets, 5 dates 1850–2040 (65 points) | Planet tolerance 12,000–9,000,000 km |
The topic Limits of the model in the app describes the model's simplifications and
quantifies them where possible; further detail in ASSETS.md and
docs/belege/hochschule/.
Every body, every cinema scene and every topic has an explanatory text on three levels, in German and English. Level and language can be switched in the app at any time.
| Level | Style | Data shown alongside | Texts |
|---|---|---|---|
| Primary school | Short texts in plain language | Diameter, orbital period, current distance from the Sun | 63 |
| Secondary school | Figures, physical relationships, links to related topics | Also mass, rotation period, axial tilt, eccentricity, orbital velocity | 63 |
| University | Full scientific basis: formulas, tables with uncertainties, open questions with both sides, citations | Also orbital elements at J2000 with rates, pole direction, geometric albedo | 69 |
The texts cover 35 bodies (the Sun, eight planets, five dwarf planets, 21 moons), 20 cinema scenes and 9 general topics such as eclipses, ring systems, axial tilt and Kirkwood gaps. The university level adds six advanced topics: tides, orbital resonances, reference systems and time scales, interior structure, photometry, and the formation of the solar system.
A dedicated topic, Limits of the model, lists what Orrery simplifies and quantifies the resulting errors, for example the time scale used for orbits or the rotation models of the planets.
- 91 source cards link each text to public reference material: NASA (50), Wikipedia (23), JPL (11), ESA (4), IAU (1) and two others. They open in a new tab and are never embedded.
- 761 publications form the literature catalogue of the university texts, 737 of them
with a DOI. Each entry is checked automatically against Crossref or arXiv
(
npm run literatur:pruefen). - 69 evidence files in
docs/belege/hochschule/record, for every university text, each claim with its value, source, location in the source and verification.
- Sun, planets, dwarf planets and moons with Saturn's and Uranus's rings, the asteroid belt with Kirkwood gaps, the Kuiper belt, a star catalogue and the Milky Way at its true position.
- Shadows and eclipses: moon shadows on planets, ring shadows, the blood moon; the cinema scene Lunar eclipse jumps to the next real one.
- View from Earth: the sky as seen from the centre of the Earth (key G), with the planets' tracks over one year, the ecliptic and the celestial equator; the field of view acts as zoom, and the cinema scene Mars loop shows the retrograde loop.
- Time control from 1 January of year 1 to 31 December 9999: pause, speed, reverse, date jump.
- Separate scale sliders for size and distance.
- Cinema mode: full screen, automatic camera flights through 20 curated scenes.
- Installable web app; works on phones, with keyboard, mouse and game controller.
- Shareable links to any date and body, e.g.
https://orrery3d.de/#date=1990-05-17&body=mars; the share button copies the exact view. - Embeddable in other pages via iframe (the Embed button copies the code);
ui=offstarts without the interface, e.g. for presentations on a projector:https://orrery3d.de/#scene=mondfinsternis&ui=off.
Orrery was built in 15 calendar days, from the initial prompt to its own domain — built with an AI coding assistant, a tool that does not work deterministically. The guiding idea was to use that tool to build a deterministic, verifiable application anyway: tests, numbers, and pixel measurements instead of impressions. How that unfolded in detail, with every number and commit hash, is told by the overview and the detailed chronicle. Both are also available as web pages at https://orrery3d.de/doku/making-of/en/.
Code is licensed under MIT (LICENSE); own texts and images under CC BY-SA 4.0
(LICENSE-TEXTE.md). Textures and the Milky Way map are subject to the
licences listed in ASSETS.md (mostly CC BY 4.0; the Milky Way map includes Gaia
data under CC BY-NC 3.0 IGO).
Development, deployment, custom music and code structure (in German):
docs/entwicklung.md.