# SEIRAKU - Celestial Mechanics — Simulate orbits and gravity

> Simulate orbits and gravity (iPhone/iPad app by Fuji Bit Inc..)

- Source: https://appshunter.io/ios/app/seiraku-celestial-mechanics/id6760764034 (this page in markdown: same URL + `.md`)
- Developer: [Fuji Bit Inc.](https://appshunter.io/developer/1874205957)
- Category: Education, Utilities
- Price: Free
- Age rating: 4+
- Requires: iOS 15.0 · 26 MB
- Languages: American English, Afrikaans, Albanian, Amharic, Arabic, Armenian, Azerbaijani, Basque, Belarusian, Bangla and 63 more
- Released: 2026-03-22
- Data updated: 2026-11-05

## What is SEIRAKU?

SEIRAKU is a visual learning app that teaches celestial mechanics by letting you move it.

Why do planets keep circling instead of falling? Why can't we predict three stars? How does the Moon move the tides? Move a slider and the bodies respond at once, with their results updating alongside. The formulas in your textbook connect to motion you can see.

[Orbits and flight]
- Orbital motion: central mass and circling planets
- Kepler's laws: ellipses and equal areas
- Hohmann transfer: two burns to change orbits on little fuel
- Gravity slingshot: speed up using a planet

[What gravity does]
- Universal gravitation: see the field as arrows and drop in particles
- Three-body problem: the figure-8 orbit and chaos
- Lagrange points (new): five places where forces balance, and their stability
- Tidal force: how tides rise and fall
- Roche limit (new): the distance where tides tear a moon apart

[Observation and Earth]
- Exoplanet transit: find planets by dimming
- Gravitational lens: light bent by gravity
- Axial precession: Earth's wobble and the changing pole star

[Features]
- Every mode responds live when you change a value
- An explanation sheet shows each formula and what it means
- Everything except ads works offline
- No sign-up. Works on phones and tablets, in landscape, with light and dark themes
- Available in 74 languages

For classrooms, self-study and anyone curious about space. Free with a banner ad. No in-app purchases.

The simulations are simplified models for education.

## Is SEIRAKU safe?

Not enough ratings yet to assess SEIRAKU.

## Is SEIRAKU legit?

SEIRAKU - Celestial Mechanics appears legitimate, with a few gaps. The AppsHunter Legitimacy Score for SEIRAKU is 65 out of 100 points across 7 verification signals from App Store and developer data.


## Version history (last 5 releases)

### 5.0.0 — 2026-11-04

5.0.0
- All-new design
- New modes: Lagrange points and the Roche limit
- Now available in 74 languages
- New ad system, with ad settings added

### 4.0 — 2026-06-04

• NEW: Gravitational Lens — experience light bending and the Einstein ring
• NEW: Axial Precession — watch a spin axis precess and the pole star shift over time
• Improved the Axial Precession view to be larger and clearer
• Refreshed the app icon
• Enjoy all 10 celestial mechanics simulations

### 3.1 — 2026-04-30

We have fixed the bug.

### 3.0 — 2026-04-29

• NEW: Hohmann Transfer — the classical minimum-fuel maneuver between circular orbits
• NEW: Exoplanet Transit — simulate dimming light curves used to detect distant worlds
• NEW: Gravity Slingshot — experience the swing-by technique used by real spacecraft
• English localization added
• 8 celestial mechanics simulations to explore and enjoy

### 2.0 — 2026-03-29

• NEW: Gravity Slingshot simulation — experience the swing-by technique used by real spacecraft
• English localization added
• 6 celestial mechanics simulations to explore and enjoy

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## More apps by Fuji Bit Inc.

- [RENGOKU: Time Attack Pachinko](https://appshunter.io/ios/app/rengoku-time-attack-pachinko/id6758652751)
- [SUUGAKU - Enjoy Numbers](https://appshunter.io/ios/app/suugaku-enjoy-numbers/id6759102221)
- [BUTURAKU](https://appshunter.io/ios/app/buturaku/id6759213255)
- [DENRAKU - Electromagnetism Sim](https://appshunter.io/ios/app/denraku-electromagnetism-sim/id6759393816)
- [PAKEDOU](https://appshunter.io/ios/app/pakedou/id6759820254)
- [OKURERUNA！](https://appshunter.io/ios/app/okureruna/id6759956971)

All apps by Fuji Bit Inc.: https://appshunter.io/developer/1874205957

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-11-05.*