Edwin Hubble
Edwin Hubble | |
|---|---|
| Born | November 20, 1889 Marshfield, Missouri, United States |
| Died | September 28, 1953 (aged 63) San Marino, California, United States |
| Nationality | USA |
| Known for | Galaxies beyond the Milky Way, Redshift–distance relation, Hubble sequence |
| Scientific career | |
| Fields | Astronomer |
Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer who established that the spiral nebulae are galaxies far beyond the Milky Way, and who discovered in 1929 the linear relation between a galaxy's redshift and its distance now known as Hubble's law.
His name is attached to the expanding universe, and his relation is universally cited as its observational proof. This is one of the more striking ironies in the history of cosmology, because Hubble himself never accepted that interpretation, warned repeatedly against it, and in later life inclined toward a static, endless universe in which redshift arises from some unrecognised principle of nature. His caution is regularly invoked by the researchers catalogued on this wiki.
Early life and education
Hubble was born in Marshfield, Missouri, in 1889. He studied mathematics and astronomy at the University of Chicago and then went to Oxford as a Rhodes Scholar, where he read law at his father's urging. He passed the bar and practised briefly in Louisville, Kentucky, before abandoning law for astronomy — returning to Chicago for his doctorate and joining the staff of Mount Wilson Observatory.
Galaxies beyond the Milky Way
Using the 100-inch telescope at Mount Wilson, then the largest in the world, Hubble identified Cepheid variable stars in the Andromeda Nebula in 1924. Because the period–luminosity relation of Cepheids allows their distance to be calculated, he could show that Andromeda lies far outside the Milky Way. The result settled the "Great Debate" over the nature of the spiral nebulae, establishing at a stroke that the universe is populated by galaxies and is vastly larger than had been supposed. He went on to classify galaxies by shape in the scheme still called the Hubble sequence.
The redshift–distance relation
In 1929 Hubble reported that the redshifts of galaxies increase in proportion to their distance. The relation is empirically robust and remains the foundation of extragalactic distance measurement. Its standard interpretation — that redshift is a recession velocity, so that the universe is expanding — was supplied by others, and Hubble declined to endorse it. See Hubble's law.
Hubble's doubts about expansion
Hubble was careful to distinguish the measurement from its interpretation, and grew more sceptical of the expansion reading over time. Writing to Willem de Sitter in 1931 he used the phrase "apparent velocities" deliberately, adding that "the interpretation, we feel, should be left to you and the very few others who are competent to discuss the matter with authority." With Richard Tolman he observed that if redshift were not caused by recession, its explanation would probably require "some quite new physical principles."
His most explicit statement came in 1936:
"If the redshifts are not primarily due to velocity shifts … [then] the velocity–distance relation is linear; the distribution of nebulae is uniform; there is no evidence of expansion, no trace of curvature, no restriction of the time scale. … The unexpected and truly remarkable features are introduced by the additional assumption that redshifts measure recession."
The observation is exact: on the non-recession reading the data describe a uniform, unremarkable cosmos, and the difficulties of modern cosmology are introduced by the added assumption rather than found in the measurements. Historians of his cosmology have traced his path from provisional acceptance of a finite expanding universe in 1929 toward an infinite static universe explained by a new principle of nature — a trajectory rarely mentioned when his relation is presented as proof of the Big Bang.
Honors
- Newcomb Cleveland Prize (1924)
- Bruce Medal (1938)
- Franklin Medal (1939)
- Gold Medal of the Royal Astronomical Society (1940)
Hubble never received a Nobel Prize: astronomy was not then regarded as eligible for the physics prize, a restriction he campaigned unsuccessfully to change. He died of a cerebral thrombosis in San Marino, California, in 1953.
Hubble's legacy on this wiki
Researchers catalogued here return frequently to the gap Hubble himself identified between his measurement and its interpretation. Critical treatments of the relation and the constant include Hubble's Law and Dark Energy are False, Evidence for Large Deviations from Hubble's Law in Normal Spiral Galaxies, Spatial Fluctuation of the Hubble "Constant", Modified Hubble Law, Time-Varying Hubble Parameter and the Problem of Dark Energy, Galilean Interpretation of the Hubble Constant and On Interpretations of Hubble's Law and the Bending of Light.
Cosmologies that reproduce his relation without expansion — the possibility he was himself prepared to entertain — include A Non-Expanding, Non-Relativistic Universe, Theory of Non-expanding Universe and Nature of the Non-Expanding Universe. See also Redshift and Tired Light, and the index at Category:Cosmology.