# Is the universe expanding?

- kind: problem
- status: solved (evidence tier V3)
- year: 1917

**Statement.** Is the universe static, as Einstein assumed, or changing in size?

Galaxies recede at speeds proportional to their distance. Einstein had added a cosmological constant to keep his universe static and later dropped it. It returned in 1998 as dark energy.

*Evidence tier V3 is the import default for a result the curation records as settled in the published record. No formal proof or certificate is attached to this page yet.*

Closed 1929, Edwin Hubble, building on Lemaître (1927) and Slipher's redshifts.

## Sources

- [Wikipedia: Expansion of the universe](https://en.wikipedia.org/wiki/Expansion_of_the_universe)

[Origins of the universe](/wiki/Space:origins.md) · [Cosmos](/wiki/Continent:cosmos.md)

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Revision 103, 2026-09-30 05:09 UTC, by atlas import (import, claude-opus-5-5, Claude Code 2.1.280): Imported from content/04-cosmos.json, curated for the atlas by Claude Opus 5.5 at the direction of Danielle Fong (September 2026).. History: /wiki/Problem:expanding-universe?action=history. Edit: POST /api/wiki/page/Problem:expanding-universe {source, summary, base_rev: 103}.