Other Free Encyclopedias » Online Encyclopedia » Encyclopedia - Featured Articles » Contributed Topics from F-J

Hubble, Edwin Powell

universe hubble’s law distance

(1889–1953) US astronomer and cosmologist: discovered expansion of universe and measured its size and age.

Hubble was trained in Chicago and Oxford in law; he was also a distinguished athlete and boxer. After a short career in law he turned to astronomy, working for most of his life at Mount Wilson Observatory. Using the 100 in telescope at Mount Wilson, Hubble was able in 1923 to resolve the nebulous outer part of the Andromeda galaxy into individual stars, obtaining a distance of 900 000 light years for several Cepheid variable stars he found there. Together with further work this proved for the first time that what were then thought of as ‘spiral nebulae’ were in fact spiral galaxies, and lay well beyond our own Galaxy. In 1929 he was able to measure the recessional velocities of 18 galaxies, and discovered that these velocities increased in proportion to their distance from Earth. This relationship ( v = Hd ) is now known as Hubble’s Law, the constant of proportionality being Hubble’s constant ( H ). This work gave the first direct evidence supporting the idea of an expanding universe, a concept that had been proposed a few years earlier by the cosmologists and is now fundamental to our understanding of the universe. Hubble’s observations meant that two fundamental quantities of the universe could be calculated for the first time: its ‘knowable’ size, or the distance at which the recession velocity reaches the speed of light, which is about 18 billion light years; and the age of the universe, Hubble himself estimated as 2 billion years, although modern values range between 12 and 15 billion years. Hubble also introduced a widely used system of classification for the shape of galaxies.

It is interesting that Hubble was always cautious in interpreting Hubble’s Law of 1929, which is based on the spectroscopic redshift and Doppler’s principle, as meaning that the universe is expanding. Hubble’s rather ambiguous writings on this imply that possibly the observed increase in red-shift with distance had other causes; and bearing in mind the many novel views advanced in cosmology since 1929, he was probably right to be prudent.

Hubel, David Hunter [next] [back] Hu-Dehart, Evelyn (1947–) - Latin American/Caribbean History; History of the Asian Diaspora; Ethnic Studies

User Comments

Your email address will be altered so spam harvesting bots can't read it easily.
Hide my email completely instead?

Cancel or