Solar System in Miniature

Motion

Every body uses the same simulated time $t$. A planet's orbital angle is $\theta=\theta_0+360^\circ t/P$, where $P$ is its published sidereal orbital period. Axial rotation is $\psi=360^\circ t_h/T$, using sidereal rotation periods in hours. Negative rotation periods preserve the retrograde direction of Venus and Uranus.

The Moon revolves around the moving Earth once every 27.3217 simulated days and turns once in the same interval, keeping the same face toward Earth. The upper scene shows the entire system; the detail enlarges the same Earth–Moon state.

Appearance and sunlight

Orbit circles are viewed obliquely, with a vertical projection factor of 0.68. Each globe is an orthographic sphere with an illuminated cap facing the Sun and a shaded night hemisphere. The terminator and visible lit fraction follow the body's position relative to the Sun. Saturn's rings are split into front and rear halves; the planet obscures the rear half, and ring segments in the geometric shadow of Saturn are darkened as the solar direction changes. The Moon is darkened when it passes through Earth's schematic cylindrical shadow on the night side of Earth. Surface markings rotate independently of the lighting. The enlarged Earth's north pole is at the upper end of its dashed projected rotation axis (N); this fixed illustrative orientation gives the surface a 23.4° on-screen tilt, not a calculation of Earth's seasonal axial orientation relative to the ecliptic. Cloud bands, Jupiter's red spot, Saturn's rings and the markings of the other planets are schematic vector artwork.

Earth and Moon surfaces

Earth's continents are real coastlines: the Natural Earth 1:50m land polygons, generalised to about 0.5° for the close-up and more coarsely for the small Earth of the overview. Deserts, steppe and savanna, rainforest, boreal forest, tundra and the Tibetan Plateau are hand-drawn regions clipped to that coastline; Greenland's ice sheet is Natural Earth's glaciated area and Antarctica is drawn as ice. Arctic sea ice, the clouds and the sun glint on the ocean are illustrative; the clouds drift slowly eastward over the ground (they turn 3 % faster than the Earth). On the night side, lights mark about 80 large metropolitan areas. With Detailed Earth in the close-up switched off, the close-up uses the coarse map of the overview instead (continents, deserts and ice, no clouds, sea ice or city lights).

The Moon's maria are the LROC mare boundaries (Nelson et al., 2014), merged and generalised to about 0.6°. Dark crater floors, bright ray craters and the South Pole–Aitken basin are placed by the IAU Gazetteer of Planetary Nomenclature; the rays of Tycho and Copernicus are schematic. Because the Moon is tidally locked, its near side with the maria always faces Earth, so the viewer sees mostly the pale far side when the Moon passes in front of Earth.

Each map polygon is projected orthographically onto its turning globe: the part on the hidden hemisphere is cut off and the visible outline is closed along the limb. In the close-up, a translucent band also dims the day side where the Sun stands lower than about 15°.

Playback

Press Play beside Time. All orbital and spin periods share one time scale. Use 4 days/s for the overall orbits, 0.02 days/s to inspect day and night, and 200 days/s to see the giant planets advance. Fast playback can make rapid axial rotations appear to strobe: at 4 days/s the Earth turns four times a second, so its continents and clouds jump from frame to frame. Switch off Detailed Earth in the close-up for smooth fast playback, or slow the pace to watch the surface turn. Changing the time scale rescales the current timeline; enter Time = 0 to restart.

• Planet diameters, orbit radii and the Earth–Moon distance are deliberately exaggerated for a textbook-style miniature. They do not represent a common physical scale.
• Orbits are circular and coplanar; the animation preserves real relative mean angular speeds and sidereal spin periods. It does not reproduce changing speeds along eccentric real orbits.
• Initial orbital longitudes and texture longitudes are illustrative, not positions for a calendar date.
• Axial tilts and surface features are drawn schematically for recognition; seasonal illumination, libration and differential rotation are omitted. Earth and Moon share a plane, so this illustration shows an eclipse at each opposition, unlike the real inclined lunar orbit. The projected Earth shadow is a sharp-edged cylindrical approximation (no penumbra, taper or atmospheric refraction). Saturn's rings are flat schematic annuli; the sharp planet shadow uses parallel sunlight and does not include penumbra or shadows cast by the rings onto the planet.
• Earth's coastlines are generalised to about 0.5° (small islands are left out); its climate zones are approximate and without seasons, the cloud field is invented rather than weather data, and the sea-ice edge is illustrative.
• The maria are drawn in one tone; mare patches smaller than about 8 square degrees and the LROC map's polar gaps beyond 65° latitude are left out.
• The Moon close-up enlarges the Earth–Moon geometry and uses the same solar direction as the overview.
• Shading and projection equations are derived here. Planetary periods come from IMCCE; the lunar period comes from NASA.

An educational animated miniature of the eight planets and Earth's Moon. Suitable for comparing orbital periods, rotation directions and the changing illuminated and dark sides. Not an ephemeris, a size/distance scale model, or an N-body simulation.