Celestial Spheres

Celestial Spheres brings the history and geometry of astronomy to life. Compare five interactive 3D models: Ptolemy, Copernicus, Tycho, the historical Keplerian model and Modern Astronomy. Discover how each system represents planetary motion, distances and the sky. EXPLORE FIVE MODELS Rotate, zoom and follow celestial bodies. See circular and epicyclic mechanisms, elliptical orbits, planetary phases, day and night, and twilight. Inspect model-aware distances, sizes, orbital speeds and angular motion. Model Comparison explains the assumptions and scales. YOUR SKY, YOUR LOCATION Enter the Sky Observatory to explore the sky from a chosen place and time. Search and track the Sun, Moon, planets and stars. Display constellations, artwork, names and coordinate grids, with altitude, azimuth, right ascension and declination. Adjust observer height and atmospheric conditions. In Simulator, place a local observer dome on Earth and explore its stars, daylight and twilight up close. ECLIPSES AND RETROGRADE Browse historical and future solar and lunar eclipses, then view the geometry in Simulator or Observatory. Explore retrograde events, stationary points and the different paths planets trace against the stars. GO FURTHER WITH PRO Unlock Tycho, Kepler and Modern Astronomy, the full eclipse collection, retrograde follow tools, major planetary moon systems, and the Comets & Asteroids feature, currently in beta. Explore selected small-body orbits, close approaches and model-aware calculations. Discover the Mechanisms Lab, with satellite orbits, gyroscopes, Coriolis effects, pendulums and weight at different latitudes and altitudes, supported by interactive diagrams and equations. COMPARE DISTANCE AND TIME Use the true-scale distance ruler and travel presentation, or explore the Sun's annual analemma and shadow trace. Switch between live time and accelerated playback. English and Arabic are supported. No advertising. Core simulations work offline; selected online data and imagery require an internet connection. Historical models include explained reconstructions and later comparison extensions. Some visual scales are adjusted for clarity. This is an educational app, not an official navigation or prediction tool. Developed by Map of Truth. © 2026 Celestial Spheres. All rights reserved.