Astronomy & Space Science · AST-656
Expansion of the Universe & the Hubble–Lemaître Law: Foundations
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Overview
Core model: Expansion of the Universe & the Hubble–Lemaître Law
On large scales, distant galaxies participate in cosmic expansion: their recession rate increases approximately in proportion to distance in the nearby Hubble flow. The Hubble-Lemaître law expresses this relationship and reflects changing spacetime scale rather than galaxies simply exploding outward from one central point.
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- 01The Big Bang — SummaryOpen source ↗
OpenStax Astronomy 2e · Mar 9, 2022
View claim-by-claim traceability3 verified claims
Galaxy spectra show systematic redshift increasing with independently estimated distance.
supported · checked Sep 22, 2026As the cosmic scale factor increases, comoving separations between widely separated unbound galaxies grow.
supported · checked Sep 22, 2026On large scales, distant galaxies participate in cosmic expansion: their recession rate increases approximately in proportion to distance in the nearby Hubble flow.
supported · checked Sep 22, 2026