CosmoScale: Space & Planets

Explore the solar system as it really is.

CosmoScale is a solar system simulator where every planet, moon and orbit is driven by real gravity — an N-body calculation running live on your phone, not a looping animation. Set any date between 1900 and 2100 and the planets stand exactly where they stand in tonight's sky. Pinch to zoom from the whole solar system down to the surface of a single moon.

■ TWO SOLAR SYSTEMS
• Easy to view — distances compressed so all eight planets, the asteroid belt and their moons fit on one screen.
• Real scale — nothing exaggerated. Zoom in more than 100,000x to find worlds that are smaller than a pixel from far away, with a scale bar that always tells you what you are looking at.
Tap any planet for a card with its live distance from the Sun and from Earth, its current orbital speed, and the date of its next closest approach — tap that date and travel there.

■ A GUIDE OF 28 SCREENS
Twenty-eight screens of astronomy, each one a working simulation rather than a page of text.
Moon & Earth — Phases of the Moon, Solar & Lunar Eclipses, Tides, Seasons
Rockets & Spaceflight — Rocket Journey: an autopilot flies the whole way from liftoff and the gravity turn to docking at the International Space Station, or from lunar orbit down to a landing
Orbits & Gravity — Kepler's Laws, Newton's Cannon, the Three-Body Problem, Retrograde Motion
Compare Size & Mass — planet size, moon size, mass, density, surface gravity
Compare Time & Speed — length of a day, rotation speed, length of a year, orbital speed
Compare the Sun's Effects — distance from the Sun, sunlight strength, temperature
Put Yourself There — enter your weight and birthday to see your age, your weight and how high you could jump on every world
Real Scale — Travel at Light Speed, Earth & Moon, Jupiter & Moons, Saturn & Titan, Neptune & Triton, Pluto & Charon

■ TEN PLANET SIMULATIONS
The Sun, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto, each drawn from real spacecraft and observatory maps, spinning at its true rotation period under a real day-and-night line. Saturn keeps its rings. Venus and Uranus really do turn backward.

■ TWO GAMES
• Swing-by — slingshot a probe past the planets and let gravity bend it to the goal.
• Landing Mission — touch down on the Moon, Titan, Pluto, Venus, Mars and Earth using real surface gravity, real atmospheric density and real wind. Venus turns out to be easier than Mars, and working out why is the whole lesson.

■ REAL SCIENCE, HONEST ABOUT THE REST
Eclipses only happen on the days they really happen. The Moon's phase matches tonight's sky. Planet positions come from JPL orbital elements, and the surface maps come from NASA, USGS and Solar System Scope. Where something is exaggerated so that you can see it — moon distances, rotation speed, the size of a probe — the in-app help says so, on that screen.

■ WRITTEN FOR BEGINNERS
Every screen has a help card explaining what you are looking at, why it happens, and what was changed to make it visible. No prior astronomy needed. Made for curious kids, students, teachers, and anyone who has ever looked up and wondered.

■ DETAILS
• Five languages: English, 日本語, 한국어, 简体中文, 繁體中文
• No account and no sign-in. The simulations run entirely on your device.
• Free, with a single banner ad on the menu screens only — never over a simulation.
• Portrait, one hand.

Space is mostly empty, and mostly enormous. CosmoScale is built so that you can feel both.