Vol. 83, No.6 December 1989 Whole No. 621
EDWIN HUBBLE 1889-1953
By Allan Sandage
The Observatories of the Carnegie Institution, Pasadena, California, U.S.A.
(Received September 22, 1989)
Hubble\'s role. This year marks the centennial of the birth of Edwin Hubble. There can be no doubt that future historians, writing about the scientific advances of this age will describe the 20th century as epoch-changing in giving us the first correct view of how the universe is organized. The principal cosmological problem of discovering the large scale content of the universe was solved observationally between 1920 and 1936. Hubble was a major figure in this development. Knowledge that galaxies mark the space and provide the means to measure it was gained by the first convincing analysis of new data on the nature of the nebulae - knowledge that came directly from the sky rather than by dialectic discussion or revelation.
In Hubble\'s time, the centre of observational work on the new astrophysics, and later on what we know as cosmology, was the Mount Wilson Observatory. The two largest telescopes in the world were there and could be regularly used on these problems. With his appointment to the Mount Wilson staff in 1919, Hubble had continuing access to both the 60-inch and the 100-inch Hooker reflectors.
He also had a most remarkable ability to cut to the core of unsolved problems concerning the nature of the nebulae. He would invariably proceed to the essence of a problem without stopping at the many lovely resting places that usually accompany the road to solutions, becoming the leading astronomer in the 1920s concerned with problems of the nebulae. In the 12 years from 1824 to 1936 he had set down the foundations upon which observational cosmology rests. From his central role in the solution of so grand a problem, Hubble has become a legend. But because part of his life has also become a myth, it is only from a study of his published papers that can we obtain a reasonable understanding of his enormous influence on the development of cosmology.
Hubble\'s name is attached to many things of everyday astronomical life. There is Hubble\'s zone of avoidance, the Hubble galaxy type, the Hubble sequence, the Hubble luminosity law for reflection nebulae, the Hubble luminosity profile for E galaxies, the Hubble constant, the Hubble time, the Hubble diagram, the Hubble redshift-distance relation, the Hubble radius for the universe, and now the Hubble Space Telescope. It seems appropriate in this centennial year to celebrate the memory of a scientist whom some have called the greatest astronomer (in changing paradigms) since the times of Galileo, Kepler and Newton. What did he do, and how did he do it?
Characteristics. It will be difficult for historians to write an accurate personal biography of Hubble using some of the extant archive sources. Known facts contradict part of the recollections set out in materials in the Hubble collection in the Huntington Library in San Marino, California, making it difficult to know which other parts are accurate. After his death, Mrs. Hubble, who survived him by 26 years, organized archive materials, also in the Huntington collection, around commentaries of his own, some of which glorify him in ways larger than life. In view of this, the authoritative historical essay by Osterbrock, Brashear, and Gwinn (1990) on Hubble\'s education and career to about 1922 should be consulted. Their history is based on sources that are, as far as possible, independent of personal recollections, largely from letters and documents in the archives of the Yerkes and the Lick observatories.
But interesting as the personal aspects of the life of great scientists are in understanding how they arrive at solutions, the solutions themselves must be independent of the personality. Otherwise, the results have no objective reality. Yet the internal excitement in arriving at solutions is never this cold within the personality itself. Every scientist lives in a world of imagination. The grander the problem, the more wonderful must be the imagination. And Hubble lived with an ineffable problem - the discovery of the structure of the World on the largest scale. From this work, by him and by others of