Expanding Universe
Expanding Universe
One-line summary: Galaxies aren't flying apart through space — space itself is stretching everywhere at once, which is why the Big Bang had no center.
The insight
The single biggest misconception about the Big Bang, per michelle-thaller, is picturing it as an explosion hurling galaxies into empty space. Instead the galaxies stay roughly put while the space between them expands in every direction — like nails on a stretching elastic sheet. There is no center and no empty exterior the universe expands "into." Running this backward gives a hot, dense early state (~13.8 billion years; estimated by extrapolating the expansion). "Big Bang" was coined by Fred Hoyle as a mockery; the expanding model traces to Belgian priest-scientist Georges Lemaître's "primordial atom" (~1920s).
Evidence
- michelle-thaller in 2026-05-28-youtube-powerfuljre-joe-rogan-experience-2506-michelle-thaller: "The galaxies are not flying through space. It's the space itself that is getting bigger in every direction at once. And that's why there's no center."
- The "observable universe" is only as large as light has had time to reach us; other galaxies have their own observable spheres extending past ours — so the whole universe is larger than what we can see, possibly infinite.
- Inflation (Alan Guth, MIT, 1970s) proposes the expansion may never fully stop and could "pop off" universes — flagged by Thaller as a necessary first model, not settled fact.
Contradictions / tensions
Thaller is careful: only the observable universe was demonstrably once in a small volume; the total universe could already have been infinite "before" the Big Bang. Sub-second early-universe physics (Planck epoch, force unification) she takes "with a big chunk of salt" because gravity and quantum mechanics don't yet combine — see what-preceded-the-big-bang.
Open questions
- what-preceded-the-big-bang
- How big is the whole universe — finite or infinite?