Compare software

Universe Sandbox vs Celestia: catalog facts
Universe Sandbox	Celestia
Paid One-time purchase from the website or Steam.	Free Free and open source.
Windows, macOS, Linux	Windows, macOS, Linux
N-body gravity simulation using Newtonian mechanics Earth climate model you can alter	Free, real-time 3D exploration of space Move freely between planets, stars and galaxies
Paid only Needs a reasonably capable desktop computer	Project website blocks automated visitors with a proof-of-work check A simulator for exploration rather than a structured astronomy course
Downloadable app	Downloadable app
Closed source	Open source
License not stated	License: GPL-2.0
Not stated if an account is needed	No account needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked September 24, 2026	Official website Full listing and sources Checked September 23, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.