# Hubble's constant

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Related to Hubble's constant: Hubble diagram, Hubble time

## Hub·ble's constant

(hŭb′əlz)*n.*

A ratio used in Hubble's law to express the rate of apparent expansion of the universe, equal to the velocity at which a typical galaxy is receding from Earth divided by its distance from Earth, approximately 71 kilometers per second per megaparsec.

[After Edwin Powell

**Hubble**.]## Hubble's Constant

In 1924, Edwin P. Hubble discovered that the farther away a galaxy is, the faster its apparent speed. The speed-to-distance ratio is the constant, now measured at 30–60 mi/sec (50–100 km/sec) per million parsecs.

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Noun | 1. | Hubble's constant - (cosmology) the ratio of the speed of recession of a galaxy (due to the expansion of the universe) to its distance from the observer; the Hubble constant is not actually a constant, but is regarded as measuring the expansion rate todaycosmogeny, cosmogony, cosmology - the branch of astrophysics that studies the origin and evolution and structure of the universe constant - a number representing a quantity assumed to have a fixed value in a specified mathematical context; "the velocity of light is a constant" |

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