SOLAR SYSTEM ORRERY interactive physics simulation
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1 day / s · forward
Camera
Focus (follow)
Scale
Distances ∝ a0.56, sizes ∝ √km — order & feel preserved, extremes compressed. Switch to “True ratios” for exact geometry.
Overlays
Guided demos
Seasons: camera rides with Earth for one full orbit — the axis stays fixed in space while the Sun’s direction swings around. Precession: the pole itself traces its 25,772-year circle. Libration: the Moon’s face wobbles exactly as in the real sky. Eclipse cones: watch the Moon’s umbra just reach Earth near perigee — and fall short near apogee (annular).
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MARS SITES
🌙 Tonight's sky
Lat Lon
Time:
Zenith-centered fish-eye of the whole sky — horizon is the outer circle, N up, E right.
Plots the 95 brightest stars, the ecliptic (dashed gold), Sun, Moon with phase, and the planets.
Positions are geocentric (Moon up to ~1° topocentric parallax); magnitudes approximate;
rise/set times are in your device's timezone.
Solar System Orrery — guide
Mouse
Drag — orbit the camera around the current focus
Wheel / pinch — zoom
Right-drag — pan
Click a label or a body — make it the camera focus (camera then rides along with it)
Keyboard
Space pause/resume · R reverse time · +/− time speed
L labels · O orbits · X Earth axis overlay · H this help
0–8 focus Sun…Neptune · 9 focus the Moon · T top view · E edge view
What is physically real here
Planet positions — JPL “approximate positions” Keplerian elements (J2000 + per-century rates), Kepler’s equation solved each frame. Valid to ≈1° of arc, best 1800–2050. The sky today matches: press ⟲ Now, focus Earth, and the day/night terminator is where it really is.
Earth’s illumination — the globe rotates by true sidereal time (GMST), so the sub-solar point (shown in the info card) is correct to ~1–2° (equation of time & nutation neglected).
Seasons — the 23.44° axial tilt is held fixed in inertial space (pointing at the celestial pole) while Earth orbits; solstices/equinoxes emerge from that, marked on the orbit.
Precession — Earth’s pole sweeps a 25,772-year circle around the ecliptic pole (run the demo or ≥100 yr/s and watch the cyan pole-star dot travel the dashed circle).
The Moon — simplified lunar theory (mean motion + eccentricity + 5.14° inclination, 18.6-yr node regression): phase, distance and libration-ish position are approximate but right. Other major moons orbit their planet’s equatorial plane with real periods and distance order; Triton is retrograde, Uranus lies on its side (97.8°).
Eclipses — Earth and the Moon cast true umbra/penumbra cones (Overlays). The Moon’s umbra just grazes Earth near perigee (total eclipse) and falls short near apogee (annular). Next solar/lunar eclipse scans up to ~6 years ahead and jumps to greatest eclipse; a badge appears whenever one is running.
Moon libration — the globe spins in a Cassini state (axis 1.54° off the ecliptic, node regressing over 18.6 yr), so the visible face wobbles ±6.3° in longitude and ±6.7° in latitude — no more, no less than the real Moon. Enable the graticule or run the demo to watch the sub-Earth point roam.
Zodiac ages — the zodiacal constellations (IAU boundaries, plus Ophiuchus, often omitted) are drawn star-fixed around the sky with their stick figures. The green marker is the March equinox point — currently in Pisces (the Age of Pisces), sliding toward Aquarius. Run Zodiac ages (26 kyr) to watch one full precession lap; the equinox takes ~2,100 years to cross each constellation.
Mars rover sites — real landing sites pinned at their planetographic coordinates (Perseverance/Jezero, Curiosity/Gale, Zhurong, InSight, Opportunity). Click a site for a tracking camera that rides with Mars’ rotation.
Tonight’s sky — enter your location (or use device geolocation) for a fish-eye whole-sky chart: 95 brightest stars, the ecliptic, Sun, Moon with phase and all planets, with alt/az, magnitudes, rise/set and astronomical-twilight times.
Not modelled — mutual perturbations, nutation (9-arcsec wobble), physical libration (~100× smaller than optical), Pluto.
Scale modes
Didactic (default) — distances ∝ a0.56 and sizes ∝ √km so the whole system is visible at once; ordering and rough proportions kept, extremes compressed. The Sun uses a slightly stronger compression (radius ∝ km0.45).
True ratios — exact numbers: 1 AU = 400 units, every radius and moon distance exact. Space is ~99.99% empty — that’s the lesson. Turn on Planet markers and use the focus menu to find things.
Credits
Earth/Moon maps: NASA imagery shipped with the three.js examples. Everything else procedural. Built with three.js.