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Hubble and His Law

July 31, 2013

The Internet is a great laxative to relieve editorial blockage. A recent example is an arXiv posting, "Anybody but Hubble!" by noted astronomer, Virginia Trimble.[1] Trimble's paper was prepared for the proceedings of a conference at Lowell Observatory in 2012, but it was rejected by the editors. The paper is about the discovery of Hubble's law, which expresses the rate of expansion of the universe. A rejected paper by a noted scientist has much more merit than other rejected papers, and such a rejection may actually increase the number of readers.

As I've noted in previous articles (for example, Sexism in Science, September 28, 2012), women scientists were rare in earlier times, but somewhat less rare after the middle of the twentieth century. A 1962 article in Life about UCLA featured a sophomore Trimble as an eighteen year-old astrophysics student.[1] She received her B.A. from UCLA in 1964, an M.A. from Cambridge University in 1969, and her Ph.D. from Caltech in 1968. Trimble joined the astronomy faculty at the University of California, Irvine, in 1971, where she remains. She was a vice president of the American Astronomical Society and the International Astronomical Union.

Hubble's law is named after American astronomer, Edwin Hubble (1889-1953). Hubble's was not really a household name until the Hubble Space Telescope (HST) was launched in 1990. The HST was launched with a flawed mirror which was spherically aberrant. The problem was solved with corrective optics in a 1994 servicing mission. Many astronomers think that astronomer Hubble's claim to his law is also flawed, and it's this question that Trimble addresses in her paper. There's another arXiv paper that argues that this law was just one of several ideas appropriated by Hubble without attribution.[3]

Edwin Hubble

Edwin Hubble (1889-1953)

During Hubble's lifetime, the Nobel Prize was withheld from astronomers; but, as astronomers started answering some important questions in physics, that changed.

(Photograph via Wikimedia Commons, modified for artistic effect.)

It's not unusual for great scientific discoveries to be independently discovered by more than one scientist. The reason for this is that science is data-driven, and these data are freely available to all in the published literature. Hubble made significant contributions to twentieth century cosmology, including observations that the recessional velocities of galaxies increase with their distance from the Earth, indicative of universal expansion. Hubble, however, wasn't the only cosmologist during the early part of the century.

It's been argued that Georges Lemaître, a Belgian priest and astronomer, discovered this law before Hubble; and, perhaps in a humility that befitted his priestly calling, he published his 1927 paper on this idea in French in a lesser known journal where it was ignored.[4] An English translation was published in 1931 in the Monthly Notices of the Royal Astronomical Society (MNRAS); however, this was not an exact translation.[4]

Georges Lemaître

Georges Lemaître (1894-1966)

Lemaître has a spacecraft named after him, as well as a lunar crater.

(Photograph via Wikimedia Commons, modified for artistic effect.)

Although Lemaître is the most cited example, Trimble lists many others who have been suggested as the originator of Hubble's law; viz.,
• Knut Lundmark, who was one of the first to work on the hypothesis that galaxies were not part of the Milky Way. Lundmark measured the distance to the Andromeda Galaxy in 1919.
• Willem de Sitter, creator of a relativistic mathematical model of the universe that allows for expansion.
• Vesto Slipher, who discovered galactic redshifts. Lemaître used Slipher's data in his 1927 paper.
• Alexander Friedmann, whose 1922 Friedmann equations provided a model for an expanding universe.
• Carl Wilhelm Wirtz, who observed galactic (then nebular) redshifts in 1918, publishing his results in 1922.
• Johann Karl Zoellner, who also worked on redshifts.
Much of the recent Lemaître-Hubble controversy has centered on the idea that Hubble may have censored Lemaître's MNRAS translation to retain priority, since text about the recession law and some of the notes were missing.[5] Astrophysicist, Mario Livio, as related in an interview with Jennifer Ouellette, investigated the matter by examining the archived correspondence of the Royal Astronomical Society, where he discovered that Lemaître, himself, had updated the article. Lemaître had deferred to Hubble's more complete work on the matter.[5]

Lemaître's 1927 paper calculated the proportionality constant of the recessional velocity vs distance relationship, which is now called the Hubble constant, to be 625 kilometers-per-second-per-megaparsec (km/s/Mpc).[5] He had used data taken by astronomer Vesto Slipher. Hubble's 1929 paper contained additional data, and it produced a Hubble constant of 500 km/s/Mpc. Hubble didn't reference Lemaître's paper, probably because he had never seen it.

Trimble concludes that "Hubble's Law" is a proper designation.[2] I think that Lemaître deserves some credit as well, but not to the extent of changing the designation to "Lemaître's Law." The moral of the story is, "Don't hide your lamp under a bushel basket." If Lemaître had originally published in a mainstream journal, the story might have been different.

One thing I enjoyed about Trimble's paper is fig. 3, shown below. In this plot, the values of the Hubble constant for poster papers at a 1995 conference are plotted as a function of poster number, which is derived from the alphabetical ordering of the first author's name. Writes Trimble, "The correlation is about as good as some of the others in cosmology."[2]

Hubble constant values from a 1995 conference

Correlation is in the eye of the beholder.

There is no apparent law that connects the value of the Hubble constant (H) and the abscissa of this plot.

(Fig. 3 of ref. 2, via arXiv.)[2]


  1. "Behind a Lovely Face, a 180 I.Q.," Life Magazine, October 19, 1962, pp. 98-99.
  2. Virginia Trimble, "Anybody but Hubble!" arXiv Preprint Server, July 8, 2013.
  3. Michael J. Way, "Dismantling Hubble's Legacy?" arXiv Preprint Server, January 30, 2013.
  4. Jean-Pierre Luminet, "Editorial note to "A Homogeneous Universe of Constant Mass and Increasing Radius accounting for the Radial Velocity of Extra--Galactic Nebulae" by Georges Lemaître (1927)," arXiv Preprint Server, May 28, 2013.
  5. Jennifer Ouellette, "Q&A With Astrophysicist Mario Livio on Brilliant Blunders," Cocktail Party Physics, May 29, 2013.

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