Calculate recession velocity, distance, and redshift using Hubble's Law. Compare Hubble constant values and explore the expanding universe.
Hubble's Law is the observation that galaxies are moving away from us at speeds proportional to their distance—the farther a galaxy is, the faster it recedes. Formulated by Edwin Hubble in 1929, this relationship is the cornerstone of modern cosmology and provides direct evidence that the universe is expanding.
The law is expressed simply as v = H₀ × d, where v is recession velocity, H₀ is the Hubble constant, and d is the distance. The Hubble constant, currently measured at roughly 67–73 km/s/Mpc (a source of ongoing scientific debate known as the Hubble tension), sets the expansion rate of the universe and inversely determines its approximate age.
This calculator enables you to compute any one of the three variables (velocity, distance, or redshift) from the others, explore how different Hubble constant values change the predicted age of the universe, and compare distances to famous cosmic objects from the Andromeda galaxy to the most distant quasars.
This calculator makes one of cosmology's fundamental relationships interactive and intuitive. By experimenting with different Hubble constant values and object distances, you develop a feel for how the universe's expansion connects distance, velocity, and cosmic age. The note above highlights common interpretation risks for this workflow. Use this guidance when comparing outputs across similar calculators. Keep this check aligned with your reporting standard.
Hubble's Law: v = H₀ × d, where v is recession velocity (km/s), H₀ is the Hubble constant (km/s/Mpc), and d is the distance (Mpc). Redshift: z = v/c. Hubble time: t_H = 1/H₀ ≈ 14 Gyr.
Result: Recession velocity ≈ 6,980 km/s; z ≈ 0.0233
A galaxy 100 Mpc (326 million light-years) away recedes at about 6,980 km/s per Hubble's Law, with cosmological redshift z ≈ 0.023.
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The observation that the recession velocity of distant galaxies is proportional to their distance from us: v = H₀ × d. It demonstrates that the universe is expanding uniformly.
The proportionality constant H₀ in Hubble's Law. It is measured in km/s/Mpc and describes the current expansion rate of the universe. Different measurement methods give values between ~67 and ~73.
A significant discrepancy between the Hubble constant measured from the early universe (CMB: ~67.4) and from the local universe (Cepheids/supernovae: ~73). This unresolved tension may hint at new physics.
Yes. Very distant galaxies can recede faster than light due to the expansion of space itself. This does not violate relativity because it is space expanding, not objects moving through space.
The stretching of light wavelengths caused by the expansion of space during the light's journey to us. A redshift z = 1 means the wavelength has doubled.
The Hubble time (1/H₀) gives a rough estimate of ~14 billion years. More precise models accounting for matter and dark energy give 13.8 billion years.