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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.]
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 today|
cosmogeny, 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"