Equations · equation

Hubble's Law

Cosmology · 1929

Equation: v = H₀·d
Field: Cosmology
Named After: Edwin Hubble · Georges Lemaître
Symbols: v recession velocity of a galaxy · d its distance from us · H₀ the Hubble constant (about 70 km/s per megaparsec today)
Year: 1929

Significance

The farther a galaxy, the faster it recedes — space itself is expanding. Lemaître derived it from general relativity in 1927; Hubble's 1929 measurements made it fact. Run the expansion backwards and you arrive at the Big Bang; H₀ is the first Friedmann equation's ȧ/a measured today — and its exact value is still argued over, a puzzle known as the Hubble tension.

Timeline

The First Galaxies Dark Energy Takes Over Present Day The Local Group Is Alone

Celestial Objects

Sun

Theories

Dark Energy Steady State Theory Big Bang Cosmology

Related

Doppler Effect First Friedmann Equation Second Friedmann Equation Chandrasekhar Limit Cosmological Redshift Critical Density Wien's Displacement Law Linear Perturbation Growth

Instruments

Planck Satellite James Webb Space Telescope (JWST)Large Synoptic Survey Telescope (LSST)Hubble Space Telescope (HST)

Constants

Hubble constant (SH0ES 2022, distance ladder)Hubble constant (Planck 2018, CMB)Parsec Age of the universe

Requires

First Friedmann Equation Cosmological Redshift

Elements

Hydrogen Calcium

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From the Equations database in Notion, last edited 2026-08-26. This page is the row, rendered by the build; nothing on it is written by hand.