Lemaître connected an expanding-universe model with observations in 1927; Hubble’s 1929 distance–redshift work supplied influential observational evidence. On large scales, more distant galaxies generally show greater recession, consistent with expanding space. This takes first place because a static cosmic setting became an evolving universe. It is not an explosion from a special centre into pre-existing empty space, and locally bound systems do not simply grow at the cosmic expansion rate.
Related reading: Distant supernovae reveal accelerating expansion.
Source: The universe is expanding.
Image credit: NASA, ESA, W. Freedman (University of Chicago), ESO, and the Digitized Sky Survey · Public domain. Resized and JPEG compressed.
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