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Prominent Catholic astronomers discuss the proposed “Hubble-Lemaître Law”

“Hubble and Lemaître brought different and complementary insights to what would come to be known as Hubble’s law — Hubble the observations, and Lemaître the model of the cosmos that obeys that law. But Lemaître got there first.”

Fr. Georges Henri Joseph Édouard Lemaître (July 1894-1966) was... [Wikipedia]; Image of Milky Way over mountains (Denis Degioanni/

In late August, the International Astronomical Union (“IAU”) held their thirtieth General Assembly in Vienna, Austria. There were many fascinating points that were discussed, yet one of them in particular should capture the attention of Catholics: the popular proposal to rename the “Hubble Law” as the “Hubble-Lemaître Law”.

Monsignor Georges Lemaître (1894-1966) was a Catholic priest, astronomer, and professor of physics at the Catholic University of Leuven, Belgium. Lemaître first proposed what has since been named – at first pejoratively, but since compellingly – the “Big Bang Theory.” As reported by the Catholic Herald earlier this summer, Google thankfully celebrated Lemaître with a “doodle” back on July 18. However, what has taken place within the last few years has been captivating, and it seems that the IAU is poised to grant to Lemaître the honor that is due to him by renaming the “Hubble Law” as the “Hubble-Lemaître Law.”

In an August 31st Discover magazine article titled “Big Bang Vote: IAU Debates Who Gets Credit for Expanding Universe”, Dr. Krzysztof Bolejko of the University of Sydney provided an historical sketch of how the resolution came about. “The rate at which the universe is currently expanding is described by the Hubble Law,” wrote Bolejko, “named after Edwin Hubble who in 1929 published an article reporting that astronomical data signify the expansion of the universe.” But Hubble was not, in fact, the first to publish on the same topic:

In 1927, Georges Lemaître had already published an article on the expansion of the universe. His article was written in French and published in a Belgian journal.

Lemaître presented a theoretical foundation for the expansion of the universe, and used the astronomical data (the very same data that Hubble used in his 1929 article) to infer the rate at which the universe is expanding.

Bolejko further notes that “Lemaître was apparently not concerned with establishing priority for his original discovery. Consequently, the formula that describes the present-day expansion rate bears the name of Hubble. The resolution of the executive committee of the IAU wants to change the name to the Hubble-Lemaître Law, to honour Lemaître and acknowledge his part in the discovery.”

Several current professors of astronomy, all of them faithfully practicing Catholics, have offered remarks to Catholic World Report about the significance of proposed name change to the Hubble-Lemaître Law.

Dr. James (Gerbs) Bauer, a professor in the University of Maryland at College Park’s Department of Astronomy:

I have to note the caveat that I’m a planetary astronomer, not a cosmologist, but was present when the resolution was introduced in the business meeting at the International Astronomical Union’s thirtieth General Assembly, on Tuesday, August 21. The meeting takes place once every three years, and this year, it was held in Vienna. The renaming of the law was based on simple forensics. Lemaître’s original 1927 publication, which contained a similar explanation as Hubble’s for the expansion of the universe, pre-dated Hubble’s 1929 publication, but was in a less-widely-read Belgian journal. Mario Livio, a scientist at the Space Telescope Science Institute (Baltimore, Maryland), did some archival digging, and found a fascinating explanation as to why the translation of Lemaître’s article into English in the Monthly Notices of the Royal Astronomical Society in 1931 did not contain the relation in the original Belgian article; he left it out himself, as the relation had already been published by Hubble. Livio concludes that this was out of a lack of concern for “establishing priority for his original discovery,” and that he rather “preferred to move forward” to publish new works, an admirable focus for the astronomer-cleric. No matter his religion or background, I’m glad that Lemaître is getting credit for what he did. I also think it’s pretty cool he was a Catholic priest.

Dr. Raymond Fermo, who received his Ph.D. in Space Physics from the University of Maryland at College Park’s Department of Physics:

Copernicus, Galileo, Newton, Einstein, Lemaître, Hubble, Gamow, Penrose, Smoot, Hawking. These are some of the giants of physical cosmology, and many of them are surely recognizable as household names; the others might not be instantly recognizable names, but they should be. The common thread between all of the names after Einstein is their successive contributions to the theory of an expanding universe and the Big Bang Theory, both of which originated with the Belgian priest Fr. Georges Lemaître.

Originally, Edwin Hubble was credited with performing the calculations that led to Hubble’s Law, but in fact Lemaître had published those calculations two years earlier in a French journal. Following Hubble’s sudden stardom, Lemaître’s writings were discovered, and he was urged to translate his own work and contributions to the theory. Rather than re-publish data that Hubble had already published (in fact, Hubble’s data was more complete because it included two additional years of data), Lemaître left out the calculations from his own translation. Hubble’s law was already well known and well verified, so he did not see the point in re-publishing it in English. Lemaître prioritized the discovery over the discoverer, so he was not concerned with establishing himself as the original discoverer.

If Lemaître could watch the debate now over whether to rename Hubble’s law to the Hubble-Lemaître law, he might eschew that discussion for more pertinent science, like the recent discovery of gravitational waves and black hole/neutron star collisions. But perhaps this name change is not for Lemaître’s sake, but for ours as modern day scientists, that we might witness his example of faithfulness to scientific integrity over worldly accolades. I doubt many people go into a career of science because of the celebrity spotlight, but surely many people go into a career of science because they fell in love with the beauty and wonder of the universe. Lemaître understood that original love better than most adult scientists, and that might be the most important thing to come out of the Hubble-Lemaître Law.

Dr. Jonathan Lunine, a professor in Cornell University’s Center for Astrophysics and Planetary Science, serves as the vice president of the Society of Catholic Scientists, and is a member of the National Academy of Sciences:

As with every major discovery, different people made complementary and overlapping contributions. Hubble used observations he and other astronomers had made to infer that the distance to any other galaxy (beyond our local cluster of galaxies) is proportional to the speed with which it is receding from us. This is called Hubble’s Law, and the constant of proportionality is called Hubble’s Constant. It is the same no matter what the distance.

Two years prior to Hubble’s paper, Lemaître showed (in a paper published in French in a Belgian journal, and hence ignored) that a model of an expanding cosmos that fits the theory of general relativity would have exactly that proportional relationship. He took the sparser data available in 1927 (including some from Hubble himself), and derived the constant of proportionality. There weren’t enough data to show it was a straight line relationship, but he knew it had to be from his model. Hubble, on the other hand, didn’t understand general relativity, never accepted that the universe was expanding, and sought other reasons for the straight-line relationship that came to bear his name. Those other reasons have proved to be incorrect.

So, Hubble and Lemaître brought different and complementary insights to what would come to be known as Hubble’s law — Hubble the observations, and Lemaître the model of the cosmos that obeys that law. But Lemaître got there first. So, calling it the Hubble-Lemaître Law is fair and reasonable. Indeed, I would also name the constant the Hubble-Lemaître Constant. Lemaître derived it first, Hubble second, and better observations over the last eighty years have given us a different value for that constant than the number either man derived.

Dr. Ryan Maderak, a professor in Benedictine College’s Department of Physics and Astronomy:

This is very significant for two reasons. Firstly, there are many controversies in the history of science regarding why a particular person received credit and name recognition for a work when it is known that others made equally important contributions. This has resulted in scientists who should have been important in their own right being relegated to footnotes in the popular history of science, as was the case with Msgr. Lemaître until renewed interest in his work in recent years. Very few of those controversies have been resolved so definitively as is being done in this case.

Secondly, given the widespread misconception that the Church has historically been anti-science, this is an extraordinary acknowledgement of the important role the Church has played in the history of science and in the development of some of the most important theories. Msgr. Lemaître deserves his place alongside such imminent Catholic cleric-scientists as Mendel. Hopefully this will lead to a renewed appreciation of the Church’s many contributions to the sciences throughout the centuries. And allow me to add a footnote on why this is so common: in the influential work “Structure of Scientific Revolutions,” Thomas Kuhn discusses the fact that the history of science is often simplified for the sake of presenting the scientific processes as smooth progression with clear benchmarks, when it is in truth anything but. And even aspiring scientists are often instructed with this simplified history, because of its pedagogical efficiency.

Dr. Karin I. Öberg, a professor in Harvard University’s Harvard-Smithsonian Center for Astrophysics and a board member of the Society of Catholic Scientists:

I think it would be a perfectly appropriate change, acknowledging that the theoretical foundation of the law was thought out and published by Lemaître before Hubble presented his empirical evidence for the expansion of the Universe.

Dr. Robert Scherrer, a professor in Vanderbilt University’s Department of Physics and Astronomy and serves as the secretary of the Society of Catholic Scientists:

I gave a talk about Lemaître at our first Society of Catholic Scientists conference. Lemaître was uniquely positioned to advance the Big Bang Theory – he had a strong background in both general relativity (which is needed to develop the equations describing the expansion of the universe) and in the observations of the expansion itself. Also, unlike nearly all of his colleagues, he never gave up on the cosmological constant, an idea which was vindicated in 1998 with the discovery that the expansion of the universe is accelerating. Cosmology had many fathers, but only one Father.

Recently, on September 14, 2018, the Church marked the 20th anniversary of the publication of Saint John Paul II’s 1998 watershed encyclical Fides et Ratio: On the Relationship Between Faith and Reason. Every Catholic – and everyone of good will – should read Fides et Ratio in order to better grasp how the “two wings” of faith and reason work together to reveal truth, a key point in overcoming the perceived division that has unfortunately arisen between science and faith in this modern era.

Finally, in a particular way, I thank Dr. Stephen Barr, a professor in the University of Delaware’s Department of Physics and Astronomy, and president of the Society of Catholic Scientists, for his assistance and guidance with this piece. If you are a professional scientist, particularly at the university level, you should consider joining the Society of Catholic Scientists, whose work is described in this recent article from Catholic News Agency.

About Justin McClain, O.P. 1 Article
Justin McClain, O.P. (a lay Dominican), has taught theology and Spanish at Bishop McNamara High School in Forestville, Maryland, since 2006, and he has written books and articles for various Catholic outlets. Justin, his wife Bernadette, and their children live in the Archdiocese of Washington.


  1. Dr. Robert Jastrow, the founding director of the NASA Goddard Institute for Space Studies and its head until 1981, on the Big Bang and the significance of the Universe having a beginning:

    For the scientist who has lived by his faith in the power of reason, the story ends like a bad dream. He has scaled the mountains of ignorance, he is about to conquer the highest peak; as he pulls himself over the final rock, he is greeted by a band of theologians who have been sitting there for centuries.

  2. ” I doubt many people go into a career of science because of the celebrity spotlight…” — Dr Raymond Fermo
    Well…. i always thought it would be very cool to have a constant named after me. “Avogadro’s number”, “a Hertz”, “The Teo”!!!

    • There once was a cleric cosmologist
      (Probably a sidebar apologist)
      But the paper he wrote
      Not much respect did evoke
      But now modern science reposits!

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