Edwin Hubble
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- For the politician, see Edwin N. Hubbell.
Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer, noted for his discovery of galaxies beyond the Milky Way and the cosmological redshift. Edwin Hubble was one of the leading astronomers of modern times and laid down the foundation upon which physical cosmology now rests.
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[edit] Biography
Edwin Hubble was born to an insurance executive in Marshfield, Missouri and moved to Wheaton, Illinois in 1889. In his younger days, he was noted more for his athletic abilities rather than his intellectual genius, although he did earn good grades in every subject, except for spelling. He won seven first places[1] and a third placing in a single high school meet in 1906. That year he also set a state record for high jump in Illinois.
His studies at the University of Chicago concentrated on mathematics and astronomy which led to a BS degree in 1910. He spent the next three years as one of Oxford's first Rhodes Scholars, where he originally studied jurisprudence, before switching his major to Spanish and receiving the MA degree, after which he returned to the United States. Some of his British mannerisms and dress stayed with him all his life, occasionally irritating his more Americanized colleagues.
Returning to the United States he worked as a high school teacher and a basketball coach at New Albany High School in New Albany, Indiana (near Louisville), and practiced law in Kentucky. He served in World War I and quickly became Major. He returned to astronomy at the Yerkes Observatory of the University of Chicago, where he earned a PhD in 1917 with a dissertation entitled "Photographic Investigations of Faint Nebulae".
In 1919 Hubble was offered a staff position by George Ellery Hale, the founder and director of Carnegie Institution's Mount Wilson Observatory, near Pasadena, California, where he remained until his death. He also served in the US Army at the Aberdeen Proving Ground during World War II. For his work there he received the Legion of Merit. Shortly before his death, Palomar's 200-inch Hale Telescope was completed; Hubble was the first to use it.
He died of a cerebral thrombosis on September 28, 1953, in San Marino, California. His wife, Grace, did not have a funeral for him and never revealed what was done with his body - it was apparently Hubble's wish to have no funeral service and be buried in an unmarked grave, or that he wanted to be cremated. As of 2006, the whereabouts of his remains are unknown.
[edit] Discoveries
[edit] Galaxies exist beyond the Milky Way
Hubble's arrival at Mount Wilson in 1919 coincided roughly with the completion of the 100-inch Hooker Telescope, then the world's largest telescope. Hubble's observations in 1923–1924 with the Hooker Telescope established beyond doubt that the fuzzy "nebulae" seen earlier with less sensitive telescopes were not part of our galaxy, as had been thought, but were galaxies themselves, outside the Milky Way. He announced this discovery on January 1, 1925.
Hubble also devised a classification system for galaxies, grouping them according to their content, distance, shape, size and brightness.
[edit] Redshift increases with distance
Hubble was generally incorrectly credited with discovering[2] the redshift of galaxies. These measurements and their significance were understood before 1917 by James Edward Keeler (Lick & Allegheny), Vesto Melvin Slipher (Lowell), and Professor William Wallace Campbell (Lick) at other observatories. Combining his own measurements of galaxy distances with Vesto Slipher's measurements of the redshifts associated with the galaxies, Hubble and Milton L. Humason discovered a rough proportionality of the objects' distances with their redshifts. Though there was considerable scatter (now known to be due to peculiar velocities), Hubble and Humason were able to plot a trend line from the 46 galaxies they studied and obtained a value for the Hubble-Humason constant of 500 km/s/Mpc, which is much higher than the currently accepted value due to errors in their distance calibrations.[3] In 1929 Hubble and Humason formulated the empirical Redshift Distance Law of galaxies, nowadays termed simply Hubble's law, which, if the redshift is interpreted as a measure of recession speed, is consistent with the solutions of Einstein’s equations of general relativity for a homogeneous, isotropic expanding space. Although concepts underlying an expanding universe were well understood earlier, this statement by Hubble and Humeson lead to wider scale acceptance for this view. The law states that the greater the distance between any two galaxies, the greater their relative speed of separation.
This discovery was the first observational support for the Big Bang theory which had been proposed by Father Georges Lemaître in 1927. The observed velocities of distant galaxies, taken together with the cosmological principle appeared to show that the Universe was expanding in a manner consistent with the Friedmann-Lemaître model of general relativity. In 1931 Hubble wrote a letter to the Dutch cosmologist Willem De Sitter expressing his opinion on the theoretical interpretation of the redshift-distance relation[4]:
- "... we use the term 'apparent velocities' in order to emphasize the empirical feature of the correlation. The interpretation, we feel, should be left to you and the very few others who are competent to discuss the matter with authority."
Today, the 'apparent velocities' in question are considered to be artifacts of a coordinate transformation that occurs in an expanding space. Light traveling through stretching space will experience a Hubble-type redshift, a mechanism different from the Doppler effect.
In the 1930s Hubble was involved in determining the distribution of galaxies and spatial curvature. This data seemed to indicate that the universe was flat and homogeneous, but there was a deviation from flatness at large redshifts. According to Allan Sandage,
- "Hubble believed that his count data gave a more reasonable result concerning spatial curvature if the redshift correction was made assuming no recession. To the very end of his writings he maintained this position, favouring (or at the very least keeping open) the model where no true expansion exists, and therefore that the redshift "represents a hitherto unrecognized principle of nature."[5]
There were methodological problems with Hubble's survey technique that showed a deviation from flatness at large redshifts. In particular the technique did not account for changes in luminosity of galaxies due to galaxy evolution.
Earlier, in 1917, Albert Einstein had found that his newly developed theory of general relativity indicated that the universe must be either expanding or contracting. Unable to believe what his own equations were telling him, Einstein introduced a cosmological constant (a "fudge factor") to the equations to avoid this "problem". When Einstein heard of Hubble's discovery, he said that changing his equations was "the biggest blunder of my life".[6]
[edit] Other discoveries
Hubble discovered the asteroid 1373 Cincinnati on August 30, 1935. He also wrote The Observational Approach to Cosmology and The Realm of the Nebulae around this time.
[edit] Nobel Prize
Hubble spent much of the later part of his career attempting to have astronomy considered an area of physics, instead of being its own science. He did this largely so that astronomers - including himself - could be recognized by the Nobel Prize Committee for their valuable contributions to astrophysics. This campaign was long unsuccessful and unfortunately Hubble's great achievements would remain unrewarded. The Nobel Prize Committee eventually decided that astronomical work would be eligible for the physics prize. Unfortunately for Hubble, this occurred in 1953 some months after Hubble's death. The Nobel Prize is never awarded posthumously.
[edit] Honors
Awards
- Bruce Medal in 1938.
- Gold Medal of the Royal Astronomical Society in 1940.
- Medal of Merit for outstanding contribution to ballistics research in 1946--ARP
Named after him
- Asteroid 2069 Hubble.
- Hubble crater on the Moon.
- Orbiting Hubble Space Telescope.
[edit] Notes
- ^ For the record, these were discus, hammer throw, pole vault, standing and running high jump, shot put, mile-relay. The third-placing was for broad jump.[citation needed]
- ^ This had actually been observed by Vesto Slipher in the 1910s, but the world was largely unaware. Ref: Slipher (1917): Proc. Amer. Phil. Soc., 56, 403.
- ^ Distance determination in astronomy continues to be an active area of research, see the article on cosmic distance ladder for more details.
- ^ http://www.astronomycafe.net/anthol/expan.html
- ^ http://antwrp.gsfc.nasa.gov/diamond_jubilee/1996/sandage_hubble.html
- ^ http://www.pbs.org/wnet/hawking/strange/html/strange_cosmo.html
[edit] References
- Christianson, Gale; Edwin Hubble: Mariner of the Nebulae Farrar Straus & Giroux (T) (New York, August 1995.)
- Hubble E.P., The Observational Approach to Cosmology (Oxford, 1937.)
- Hubble E.P., The Realm of the Nebulae (New Haven, 1936.)
- Hubble, A relation between distance and radial velocity among extra-galactic nebulae, Proceedings of the National Academy of Sciences Volume 15 (1929)
[edit] See also
- Galaxies
- Galaxy classification
- Gerard de Vaucouleurs
- De Vaucouleurs modified Hubble sequence
- Galaxy classification
- Spiral nebula
- William Wilson Morgan
- Expansion of the universe
- Hubble Space Telescope
- Cosmic distance ladder
[edit] External links
- Time 100 Profile
- Astronomy at the University of Louisville - Photographs of Edwin Hubble at New Albany High School.
- Edwin Hubble bio - Written by Allan Sandage
- O'Connor, John J., and Edmund F. Robertson. "Edwin Hubble". MacTutor History of Mathematics archive.
| Persondata | |
|---|---|
| NAME | Hubble, Edwin Powell |
| ALTERNATIVE NAMES | |
| SHORT DESCRIPTION | American astronomer |
| DATE OF BIRTH | 20 November 1889 |
| PLACE OF BIRTH | Marshfield, Missouri |
| DATE OF DEATH | 28 September 1953 |
| PLACE OF DEATH | San Marino, California |
