Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer who significantly contributed to the development of extragalactic astronomy and observational cosmology.
Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology.
Hubble demonstrated that numerous celestial entities, previously categorized as "nebulae" and presumed to be interstellar clouds of dust and gas, were in fact distinct galaxies situated beyond the Milky Way. His methodology for determining galactic and extragalactic distances relied upon the robust direct correlation between a classical Cepheid variable's luminosity and its pulsation period, a relationship identified by Henrietta Swan Leavitt in 1908.
In 1929, Hubble substantiated the principle that a galaxy's recessional velocity is directly proportional to its distance from Earth. This phenomenon, subsequently termed Hubble's law, had been initially posited by Georges Lemaître two years prior. The implications of Hubble's law suggest an expanding universe. Furthermore, a decade earlier, American astronomer Vesto Slipher had presented initial empirical data indicating significant redshift in the light emitted from many of these nebulae, thereby signifying substantial recession velocities.
Hubble's legacy is predominantly associated with the Hubble Space Telescope, named in his honor, a model of which is conspicuously exhibited in his birthplace of Marshfield, Missouri.
Early life and education
Born in Marshfield, Missouri, in 1889, Edwin Hubble was the son of Virginia Lee Hubble (née James) (1864–1934) and John Powell Hubble, an insurance executive. The family relocated to Wheaton, Illinois, in 1900. During his youth, Hubble was more renowned for his athletic capabilities than his academic aptitude, despite achieving commendable grades in all subjects except spelling. A highly talented athlete, he participated in baseball, football, and track and field throughout his high school and collegiate years. In 1906, he secured seven first-place finishes and one third-place finish at a single high school track and field event. On the basketball court, he demonstrated versatility, playing various positions from center to shooting guard. In 1907, Hubble captained the University of Chicago's basketball team to its inaugural Big Ten Conference championship.
Undergraduate studies
At the University of Chicago, Hubble's academic pursuits focused on mathematics, astronomy, and philosophy, culminating in a Bachelor of Science degree by 1910. For one year, he served as a student laboratory assistant under physicist Robert Millikan, who would later become a Nobel laureate. Hubble was also initiated into the Kappa Sigma fraternity. As a Rhodes Scholar, he subsequently dedicated three years to studying jurisprudence at The Queen's College, Oxford, fulfilling a commitment made to his ailing father, rather than pursuing science. He later incorporated studies in literature and Spanish, ultimately obtaining a master's degree.
In 1909, Hubble's father relocated the family from Chicago, Illinois, to Shelbyville, Kentucky, seeking a smaller town environment, before ultimately settling in nearby Louisville. His father passed away in the winter of 1913, during Edwin's tenure in England. The subsequent summer, Edwin returned to the United States to provide care for his mother, two sisters, and younger brother, in addition to his brother William. The family subsequently moved to Everett Avenue in Louisville's Highlands neighborhood, to accommodate Edwin and William.
Despite a profound lifelong interest in astronomy, Hubble, as a devoted son, complied with his father's wish for him to pursue legal studies, initially at the University of Chicago and subsequently at Oxford University. During this period, he also undertook coursework in mathematics and science. Following his father's demise in 1913, Edwin returned to the Midwest from Oxford but lacked the inclination to practice law. Consequently, he accepted a teaching position at New Albany High School in New Albany, Indiana, instructing Spanish, physics, and mathematics, and also coaching the boys' basketball team. After one year of secondary education instruction, he enrolled in graduate school, facilitated by a former University of Chicago professor, to study astronomy at the university's Yerkes Observatory. He earned his Ph.D. in 1921, with a dissertation titled "Photographic Investigations of Faint Nebulae." At Yerkes, he utilized the 40-inch refractor telescope, constructed by George Ellery Hale in 1897, and an innovative 26-inch (61 cm) reflector telescope.
Doctoral studies
After the United States declared war on Germany in 1917, Hubble expedited the completion of his Ph.D. dissertation to facilitate his military enlistment. Hubble enlisted in the United States Army and was deployed to the newly formed 86th Division, where he held a position within the 2nd Battalion, 343rd Infantry Regiment. He attained the rank of major and was deemed eligible for overseas deployment on July 9, 1918; the 86th Division was deployed overseas; however, it did not engage in combat, as its personnel were subsequently reassigned as replacements to other units. Following the conclusion of World War I, Hubble undertook a year of postgraduate study at the University of Cambridge, resuming his astronomical research.
Career
In 1919, George Ellery Hale, the founder and director of the Carnegie Institution for Science's Mount Wilson Observatory near Pasadena, California, extended a staff appointment to Hubble. Hubble maintained his affiliation with Mount Wilson until his demise in 1953. Prior to his passing, Hubble was the inaugural astronomer to utilize the recently commissioned 200-inch (5.1 m) Hale Reflector Telescope at the Palomar Observatory near San Diego, California.
Hubble also served as a civilian employee for the United States Army at the Ballistic Research Laboratory's External Ballistics Branch, located at Aberdeen Proving Ground in Maryland, throughout World War II. In this capacity, he oversaw extensive research in exterior ballistics, contributing to enhanced effective firepower for bombs and projectiles. His contributions were augmented by his personal innovations in exterior ballistics instrumentation; notably, he developed the high-speed clock camera, an advancement that enabled comprehensive study of the in-flight characteristics of bombs and low-velocity projectiles. The outcomes of his investigations were instrumental in refining the design, performance, and military efficacy of bombs and rockets. For these contributions, he was awarded the Legion of Merit.
Discoveries
The Universe Extends Beyond the Milky Way Galaxy
Edwin Hubble's arrival at Mount Wilson Observatory, California, in 1919 approximately coincided with the completion of the 100-inch (2.5 m) Hooker Telescope, then the largest in the world. During this period, the predominant cosmological understanding posited that the universe was solely comprised of the Milky Way galaxy.
Utilizing the Hooker Telescope at Mount Wilson, Hubble identified Cepheid variables, a class of standard candles previously discovered by Henrietta Swan Leavitt. By comparing their apparent luminosity with their intrinsic luminosity, astronomers can determine their distance from Earth. Hubble detected Cepheids within several nebulae, notably the Andromeda Nebula and the Triangulum Nebula. His 1924 observations conclusively demonstrated that these nebulae were far too remote to reside within the Milky Way, establishing them as independent galaxies beyond our own; consequently, they are no longer classified as nebulae.
This concept was initially hypothesized in 1755 with the publication of Immanuel Kant's General History of Nature and Theory of the Heavens. Hubble's hypothesis encountered significant resistance from the contemporary astronomical establishment, particularly from Harlow Shapley, who was affiliated with Harvard University. Notwithstanding this opposition, Hubble, then aged thirty-five, first disseminated his findings in The New York Times on November 23, 1924, subsequently presenting them to the broader astronomical community at the American Astronomical Society meeting on January 1, 1925. Formal publication of Hubble's results concerning the Andromeda galaxy in a peer-reviewed scientific journal did not occur until 1929.
Hubble's findings profoundly altered the prevailing scientific understanding of the universe. Proponents assert that Hubble's identification of extragalactic nebulae established a foundational framework for subsequent astronomical research. Despite initial skepticism from some prominent colleagues, Hubble proceeded with the publication of his findings. This published research garnered him the American Association Prize and a monetary award of five hundred dollars from Burton E. Livingston, representing the Committee on Awards.
Hubble also developed the predominant system for galactic classification, categorizing them based on their morphological characteristics observed in photographic imagery. These distinct galactic categories were organized into what is now recognized as the Hubble sequence.
The Redshift-Distance Relationship
Hubble subsequently calculated the distances to 24 extragalactic nebulae, employing diverse methodologies. In 1929, he investigated the correlation between these distances and their radial velocities, which were derived from observed redshifts. While his distance estimations are now recognized as being underestimated by a factor of up to approximately seven, primarily due to issues such as misidentifying bright gas clouds as stars or failing to distinguish between different types of Cepheid variables, his measurements maintained a proportional relationship to the actual distances. By integrating his distance data with galactic redshift measurements obtained by Vesto Slipher and his assistant Milton L. Humason, Hubble identified an approximately linear relationship between galactic distances and their radial velocities (adjusted for solar motion), a finding subsequently termed Hubble's Law.
This observation implied that the relative separation speed between any two galaxies increased proportionally with their distance. Interpreted in this manner, Hubble's analysis of 46 galaxies yielded a Hubble constant value of 500 km/s/Mpc. This figure significantly exceeds contemporary accepted values, such as 74 km/s/Mpc (derived from the cosmic distance ladder method) or 68 km/s/Mpc (obtained via the CMB method), a discrepancy attributed to inaccuracies in his initial distance calibrations.
Despite these findings, the underlying cause of the redshift remained ambiguous. Georges Lemaître, drawing upon Einstein's general relativity equations, theoretically predicted the redshift-distance relationship and subsequently published observational evidence supporting it, predating Hubble's Law by two years. Although Lemaître employed terms like "velocities" in his publication and "apparent radial velocities" in its introduction, he later voiced reservations regarding their interpretation as actual velocities. In 1931, he communicated his perspective on the theoretical implications of the redshift-distance correlation in a letter to the Dutch cosmologist Willem de Sitter:
"Mr. Humason and I are both deeply sensible of your gracious appreciation of the papers on velocities and distances of nebulae. We use the term 'apparent' velocities to emphasize the empirical features 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."
Presently, these "apparent velocities" are generally understood as an increase in proper distance resulting from the universe's expansion. Light propagating through an expanding metric undergoes a Hubble-type redshift, a process distinct from the Doppler effect. Nevertheless, for proximate galaxies, these two mechanisms can be considered equivalent descriptions, linked by a coordinate transformation.
During the 1930s, Hubble dedicated efforts to ascertain the distribution of galaxies and the universe's spatial curvature. His collected data initially suggested a flat and homogeneous universe, yet a departure from flatness became apparent at significant redshifts. Allan Sandage noted:
"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.'"
Methodological flaws in Hubble's survey technique contributed to the observed deviation from flatness at high redshifts. Specifically, his approach failed to account for variations in galactic luminosity caused by galaxy evolution. Previously, in 1917, Albert Einstein's nascent theory of general relativity had suggested that the universe must either expand or contract. Reluctant to accept this implication of his own equations, Einstein incorporated a cosmological constant—a "fudge factor"—to circumvent this perceived "problem." Upon learning of Hubble's redshift observations, Einstein promptly recognized the veracity of the expansion predicted by general relativity, later remarking that altering his equations constituted "the biggest blunder of [his] life." During his 1931 "
Edwin Hubble also identified the asteroid 1373 Cincinnati on August 30, 1935. In 1936, he authored two significant works, The Observational Approach to Cosmology and The Realm of the Nebulae, which elucidated his methodologies in extragalactic astronomy and presented his historical perspective on the field.
During December 1941, Hubble informed the American Association for the Advancement of Science that a six-year observational study conducted with the Mount Wilson telescope yielded data inconsistent with the expanding universe theory. A Los Angeles Times report on Hubble's statements quoted him asserting, "The nebulae could not be uniformly distributed, as the telescope shows they are, and still fit the explosion idea. Explanations which try to get around what the great telescope sees, he said, fail to stand up. The explosion, for example, would have had to start long after the earth was created, and possibly even after the first life appeared here." This perspective was influenced by Hubble's calculation of the constant, which would have placed the Big Bang approximately two billion years in the past.
Personal Life
On February 26, 1924, Hubble married Grace Lillian (Burke) Leib (1889–1980), who was the daughter of John Patrick and Luella (Kepford) Burke.
Although Hubble was raised within the Protestant Christian tradition, certain later declarations indicate a degree of religious uncertainty.
Health and Demise
In July 1949, while vacationing in Colorado, Hubble experienced a myocardial infarction. His wife provided care, and he subsequently adhered to an adjusted diet and work regimen. On September 28, 1953, he succumbed to cerebral thrombosis, a blood clot in his brain, in San Marino, California. No funeral service was conducted, and his wife chose not to disclose his final resting place.
The majority of Hubble's archival materials, including his correspondence, photographs, notebooks, observing logbooks, and other documents, are preserved at the Huntington Library in San Marino, California. These materials were bequeathed by his wife, Grace Burke Hubble, following her death in 1980.
Controversies
Allegations Regarding Lemaître's Priority
In 2011, the scientific journal Nature published allegations suggesting Hubble's potential involvement in the omission of crucial sections from the 1931 English translation of Lemaître's 1927 paper. This original paper had articulated what subsequently became known as Hubble's law and provided empirical evidence. Historians cited in the article expressed skepticism regarding whether these redactions constituted a deliberate effort to secure Hubble's priority. Nevertheless, observational astronomer Sidney van den Bergh later published research positing that, even if executed by a translator, the omissions could still have been intentional.
In November 2011, astronomer Mario Livio announced in Nature the discovery of a letter within the Lemaître archive, which indicated that Lemaître himself had performed the redaction. Lemaître reportedly perceived no utility in re-publishing scientific findings that Hubble had already presented in 1929. Despite this, it remains a historical fact that Lemaître's formulation of the law was published in French two years before Hubble's publication.
Nobel Prize Advocacy
Throughout Hubble's lifetime, the Nobel Prize in Physics did not encompass astronomical research. Hubble dedicated a significant portion of his later career to advocating for the reclassification of astronomy as a sub-discipline of physics, rather than a distinct scientific field. His primary motivation was to enable astronomers, including himself, to receive recognition from the Nobel Committee for their advancements in astrophysics. This endeavor did not succeed during his lifetime; however, shortly after his passing, the Nobel Prize Committee determined that astronomical contributions would qualify for the physics prize. Nevertheless, Nobel Prizes are not conferred posthumously.
Honors
Awards
- Newcomb Cleveland Prize (1924);
- Bruce Medal (1938);
- Franklin Medal (1939);
- Gold Medal of the Royal Astronomical Society (1940);
- Legion of Merit for exceptional contributions to ballistics research (1946).
Distinctions
- Elected member of the United States National Academy of Sciences (1927);
- Elected member of the American Philosophical Society (1929).
Namesakes
- Asteroid 2069 Hubble;
- The lunar crater Hubble;
- The orbiting Hubble Space Telescope;
- The Edwin P. Hubble Planetarium, situated within Edward R. Murrow High School in Brooklyn, New York;
- The Edwin Hubble Highway, which designates the segment of Interstate 44 traversing his birthplace of Marshfield, Missouri;
- Hubble Middle School, a public educational institution in Wheaton, Illinois, where he resided from the age of eleven onwards.
Postage Stamp
On March 6, 2008, the United States Postal Service issued a 41-cent stamp commemorating Hubble as part of an "American Scientists" sheet, which was designed by artist Victor Stabin. The accompanying citation states:
Astronomer Edwin Hubble (1889–1953), frequently recognized as a "pioneer of the distant stars," was instrumental in elucidating the universe's immense and intricate nature. His rigorous investigations into spiral nebulae conclusively demonstrated the existence of galaxies beyond the Milky Way. It is speculated that had he not passed away unexpectedly in 1953, Hubble would have been awarded the Nobel Prize in Physics for that year.
(The claim regarding his potential Nobel Prize win in 1953 is probably inaccurate, despite his nomination for the award during that year.)
Other distinguished scientists featured on the "American Scientists" stamp sheet include biochemist Gerty Cori, chemist Linus Pauling, and physicist John Bardeen.
Additional Notable Recognitions
- In 1934, he delivered the Halley Lecture at the University of Oxford.
- Inducted into the Hall of Famous Missourians in 2003.
- Featured in the 2008 "American Scientists" U.S. stamp series, valued at $0.41.
- Inducted into the Indiana Basketball Hall of Fame in 2017.
Cultural Depictions
The theatrical production Creation's Birthday, authored by Cornell physicist Hasan Padamsee, chronicles Hubble's biographical narrative.
References
References
Bartusiak, Marcia. The Day We Found the Universe. New York: Pantheon, 2009.
- Bartusiak, Marcia. The Day We Found the Universe. New York: Pantheon, 2009.
- Christianson, Gale. Edwin Hubble: Mariner of the Nebulae. Farrar Straus & Giroux (New York, August 1995).
- Hubble, E. P. The Observational Approach to Cosmology. Oxford, 1937.
- Hubble, Edwin Powell (1982) [1936]. The Realm of the Nebulae. Mrs. Hepsa Ely Silliman Memorial Lectures, 25. New Haven, Connecticut: Yale University Press. ISBN 9780300025002. OCLC 611263346.Hubble, Edwin (1929). "A Relation Between Distance and Radial Velocity Among Extra-Galactic Nebulae." PNAS. 15 (3): 168–173. Bibcode:1929PNAS...15..168H. doi:10.1073/pnas.15.3.168. PMC 522427. PMID 16577160.
- Osterbrock, Donald E., Joel A. Gwinn, and Ronald S. Brashear (July 1993). "Edwin Hubble and the Expanding Universe." Scientific American. 269 (1): 84–89. Bibcode:1993SciAm.269a..84O. doi:10.1038/scientificamerican0793-84.
- Time profile
- Edwin Hubble bio – Written by Allan Sandage
- American Physical Society's Hubble Bio Archived July 5, 2008, at the Wayback Machine
- Edwin Hubble – The problem of the expanding universe, 1942
- Osterbrock, Donald E., Joel A. Gwinn, and Ronald S. Brashear (July 1993). "Edwin Hubble and the Expanding Universe." Scientific American. 269 (1): 84–89. Bibcode:1993SciAm.269a..84O. doi:10.1038/scientificamerican0793-84.