There has been a considerable mythology built around Hubble since his work in the 1920s at the Mount Wilson observatory. In particular, despite his magnificent work that needs no exaggeration, he has been attributed with discovering redshift, with discovering the distance-redshift correlation and with discovering the expanding universe, none of which is actually true.
Hubble preferred the term ‘Red Shift’ as a neutral description because the then used term, ‘radial velocity’, implied a cause for the phenomena, one in which he didn’t agree. He used the conventional ‘radial velocity’ term in his 1929 paper but the preferred ‘Redshift’ term appears in subsequent papers. Hubble was not implying an expanding universe, that was suggested by others, especially Richard Tolman, and modelled by the likes of Georges LemaĆ®tre who also came up with the first crude version of the Big Bang dubbed ‘The primeval Atom’.
Richard Tolman was the real energy behind the expanding universe view and tried, unsuccessfully, to convince Hubble of it. Hubble wrote a joint paper in 1935 with Tolman ‘Two Methods of Investigating The Nature of the Nebular Red-Shift’ in which Tolman argued for the expanding universe and Hubble argued for an alternative interpretation of the redshift: “In the case of the relation between nebular dimensions and luminosities, the observations are such as to confirm our general ideas as to the extra-galactic character of the objects in question, but are not yet sufficient to permit a decision between recessional or other causes for the red-shift.” (from the abstract). In his 1936 book 'The realm of the nebulae’ he says “The expanding universe of general relativity would still persist in theory, but the rate of expansion would not be indicated by the observations. (redshift)” and in his 1942 paper 'The Problem of The Expanding Universe’ he not only argues against redshift as caused by cosmological expansion but gives a list of reasons why this can not be the case.
Hubble did not actually measure any red shifts, that was done by his colleague Milton Humason. Redshifts had first been measured by Vesto Slipher initially in 1912 and he measured at total of some 40 ‘nebulae’. Hubble used some of that data in his famous 1929 paper ‘A Relation between distance and Radial Velocity among Extra-Galactic Nebulae’.
Considering terms like ‘Hubble Expansion’, ‘Hubble Flow’, ‘The Hubble Constant’ and other such terms you’d think that Hubble was front and centre in the expansion of the universe hypothesis, but actually he never believed it and never came up with any of the concepts that were named in his honour. Hubble led the alternative explanation for the Redshift debate.
I came to this conclusion after reading some of Hubble’s papers, articles and books but others did not agree. During a conversation with Adam Riess, one of the Hubble telescope site’s administrators, I found the original scientific obituary of Hubble written just one year after his death by a distinguished scientist and colleague of Hubble at the Mount Wilson Observatory Dr. Nicholas Mayall (https://en.wikipedia.org/wiki/Nicholas_Mayall) of the Lick Observatory University of California who wrote both the more academic biography for National Academy of Sciences and a less formal obituary in Sky and Telescope just one year after Hubble’s Death which is linked to this essay.
Members can read the full text by following the attached link. I have transcribed the relevant section and reproduced it below. Note that this obituary was written before historical revisionism deified Hubble and started to say such things as ‘Hubble discovered the expanding Universe’. A 1977 interview with the author (Dr.Mayall) of this piece can be found here (includes more details on what Hubble *actually* did). https://www.aip.org/history-programs/niels-bohr-library/oral-histories/4766 and the academic biography mentioned above can be downloaded here http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/hubble-edwin.pdf
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Edwin Hubble
Observational Cosmologist
By Nicholas Ulrich Mayall, Lick Observatory University of California
“Directly as a consequence of his use of brightest stars in spirals, Hubble obtained distances several times more accurate than those previously based only on diameters or on brightnesses of nebulae. By 1929 he had distances for 18 isolated nebulae and for four in the Virgo cluster. Radial velocities by V. M. Slipher were available for all of these. The two quantities, velocity and distance, proved to be closely proportional: the larger the distance, the greater the velocity of recession. Such a relationship had to some extent been anticipated by Lundmark and Wirtz from fewer and less precise data, and by de Sitter’s mathematical work using relativity theory. But Hubble’s new approach clarified an obscure situation and laid a firm foundation for a spectacular advance involving fainter and more distant nebulae.
While Hubble measured total brightnesses of galaxies in clusters to obtain increasingly greater distances, his colleague Milton Humason photographed their spectra for measurement of radial velocities. The results were of unprecedented interest: a straight-line relationship between distances out to 250 million light-years and velocities up to 26,000 miles per second. These data were forthwith exploited by theorists into a concept of the expanding universe. But when apparent velocities for entire stellar systems reached nearly one seventh of the velocity of light, there seemed good reason to ask if the spectrum measurements really represented motion, and here Hubble again blazed the trail. Thenceforth he preferred the term red shift, a simple noncommittal description of the spectral lines displaced toward the longer wavelengths.
The observational interpretation of red shifts, either as motion or as no motion, became for Hubble a central problem of extragalactic research. He showed how such discrimination might be made by counts of nebulae to the faintest possible magnitude limits, provided the latter could be accurately specified. His formulation of the problem indicated that the crucial data lay at the dim threshold of long exposure taken with the 100-inch reflector. From a bold use of this instrument to the limits of its power, he concluded that the red shifts may represent a new phenomenon, rather than velocity recession. He was well aware, however, that a more powerful telescope was necessary for a definitive solution of the problem, and his researches on nebulae furnished some of the strong arguments for the construction of the 200-inch reflector. He actively supported the project from its beginning, and it is fitting that he made the first photographic observations of nebulae with the Hale telescope.
But Hubble did far more than set up a distance scale to follow the mysterious red shifts out to an enormously extended astronomical horizon.”
[page 78 of Sky and Telescope, Vol. XIII, No.3, January 1954]
https://archive.org/details/Sky_and_Telescope_1954-01-pdf
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Here are some examples from his published work::
Red Shifts and the distribution of Nebulae
Edwin Hubble 1937
“The interpretation of red shifts by the theory of expanding universes is so plausible and so widely current that, in making a delicate test of the theory, it is desirable to push uncertainties in the favourable direction before admitting a discordance. Nevertheless—and this is perhaps the significant result of the investigation—when the observational data are weighted in favour of the theory as heavily as can reasonably be allowed, they still fall short of expectations.”
And in the conclusions:
“For these reasons the direct evaluation of R0 and its derivatives from the laws of distribution and of red shifts, separately, seems preferable to McVittie’s indirect approach. Nevertheless, the observations as they stand lead to the anomaly of a closed universe, curiously small and dense, and, it may be added, suspiciously young. On the other hand, if red shifts are not primarily velocity-shifts, these characteristics vanish and the observable region appears as a small, homogeneous, but insignificant sample of a universe that may extend indefinitely both in space and in time.”
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Well known Cosmologist Allan Sandage lists some facts about Hubble’s thinking:
“Hubble concluded that his observed log N(m) distribution showed a large departure from Euclidean geometry, provided that the effect of redshifts on the apparent magnitudes was calculated as if the redshifts were due to a real expansion. A different correction is required if no motion exists, the redshifts then being due to an unknown cause. 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”. This viewpoint is emphasized (a) in The Realm of the Nebulae, (b) in his reply (Hubble 1937a) to the criticisms of the 1936 papers by Eddington and by McVittie, and © in his 1937 Rhodes Lectures published as The Observational Approach to Cosmology (Hubble 1937b). It also persists in his last published scientific paper which is an account of his Darwin Lecture (Hubble 1953).“
Sandage, Allan (1989), "Edwin Hubble 1889–1953”, The Journal of the Royal Astronomical Society of Canada, Vol. 83, No.6. Retrieved March 26, 2010.
https://apod.nasa.gov/diamond_jubilee/1996/sandage_hubble.html
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In his book of 1938 “The Realm of The Nebula”, introduction to the eighth chapter 'The Velocity-Distance Relation’: “Red-shifts resemble velocity-shifts, and no other satisfactory explanation is available at the present time : red-shifts are due either to actual motion of recession or to some hitherto unrecognized principle of physics. Therefore, the empirical law is generally described as the velocity-distance relation (velocity = constant X distance), and is often considered as visible evidence of the expanding universe of general relativity.”
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