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. Continents, cloud bands, Jupiter's red spot, Saturn's rings, polar caps and lunar maria are schematic vector artwork.

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. 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.
• 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.