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Hubble constant |
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Hubble constant [′həb·əl ‚kän·stənt] (astrophysics) The rate at which the velocity of recession of the galaxies increases with distance; the value is about 70 kilometers per second per megaparsec (or 2.3 × 10-18s-1) with a relative uncertainty of about ± 10%. How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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Since measurements of the distances to galaxies are uncertain, however, the Hubble constant isn't known to an accuracy better than 10 percent, and the age of the universe derived using this method is plagued by the same uncertainty. The rate of expansion of the universe is described by the Hubble constant (the ratio of the speed at which a galaxy is receding from the earth to its distance from the earth); its measurement and actual value have long been a topic of cosmological controversy, with professional bragging rights, as well as the age and ultimate fate of the universe, on the line. While he welcomes time-delay measurements that are more accurate, he says astronomers must better determine how mass is distributed in each lens before they can convert the data into a new estimate of the Hubble constant. |
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