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Technique · The Cosmic Distance Ladder

Redshift & the Hubble–Lemaître Law

For distant galaxies, the expansion of the universe stretches their light to longer, redder wavelengths in proportion to their distance. Measure the redshift, apply the Hubble–Lemaître law, and you have the distance — the top rung of the ladder.

The Cosmic Distance LadderMeasures: Distance to distant galaxies

Knowledge connections

Sources

The primary and reference sources this topic draws on.

  • NASANational Aeronautics and Space Administration

    Mission data, planetary science, space telescopes, and public-domain imagery.

    Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.