[Picture: Monsignor Lemaître  standing with Einstein at a conference in California in 1933]

On October 29, 2018, the International Astronomical Union (IAU) voted to recommend renaming Hubble’s Law — the equation describing the expansion of the cosmos — as the “Hubble-Lemaître Law.”  That such a vote would take place today — during a time when science and faith are portrayed in the media as implacable foes — speaks to the remarkable character of Lemaître himself, the Belgian monsignor and astronomer who made a number of fundamental contributions to the science of cosmic structure and origins.  His dual career as priest and scientist puzzled many in science and in the public at large when he was alive, and his struggles to defend his “Big Bang” model of the origin of the universe against those who accused him of being religiously motivated epitomizes the growing tension between science and organized religion in post-war Europe and the US.

The story we will tell about Lemaître will of necessity be selective in the details of his life, which was complex and rich enough to merit multiple biographies,^1,2 as well as numerous articles.  I want to emphasize those aspects of his career that merited the decision of the IAU, a body of over 10,000 professional astronomers, along with some other contributions that are less well-known but also deserving of recognition.  Lemaître’s religious views are equally extensive and complex, and I will focus only on those that connect to his scientific work and the debates that emanated therefrom.

Georges Henri Joseph Édouard Lemaître was born July 17, 1894, in Charleroi, Belgium.  At an early age he felt called to become a priest, but did not pursue ordination until after he completed his scientific education at the Catholic University of Louvain.  Initially setting out to study civil engineering, he left the university to fight in World War I as an artillery officer for the Belgian army, for which he was awarded the Belgian War Cross.  Returning to his education in 1918, he obtained a Docteur en Sciences (equivalent to a Ph.D.) from Louvain in 1920, with a thesis on pure mathematics.  He then was ordained a priest in 1923, but having become aware of new developments in astronomy, he sought and obtained permission from his superiors to become a research associate at Cambridge University (UK) under the famous astronomer Sir Arthur Eddington.  A year later he went on to the other Cambridge — Cambridge, MA — where he worked at Harvard College Observatory with Harlow Shapley and in 1927 was awarded a Ph.D. from M.I.T. ³ with a thesis on the behavior of gravitational fields under general relativity.⁴  In 1925, he returned to Louvain to take up a faculty position.  The three short years Lemaître was abroad equipped him with the tools of general relativity and an understanding of the astronomical data of the time, by which he would quickly revolutionize contemporary understanding of the history of the universe.

To appreciate Lemaître’s contribution requires that we recognize how different the astronomy of the early 20^th century was from today.  In 1917, Albert Einstein published his theory of “general relativity,” in which gravity is the geometry of the space and time we exist in.  The size and structure of the universe was poorly known then.  It was understood that the solar system — Sun, Earth, and other planets — is located in a large assemblage of billions of stars called the Milky Way Galaxy.  However, the argument of the day was whether the Milky Way was in fact the entire universe.  Up through the first decade of the 20^th century, telescopes were not powerful enough to resolve the true nature of spiral-shaped “nebulae” (Latin for mists or clouds) as other galaxies like the Milky Way.⁵  Thus, when Einstein conceived his theory of general relativity a decade earlier, the simplest assumption was that the universe is static, unchanging over countless eons of time.⁶  But this posed a serious problem for Einstein, because his theory of gravity required that matter distort space in such a way that a static universe — all matter, and space itself — would simply collapse upon itself.  He therefore introduced an arbitrary “cosmological constant” into his equations governing the geometry of space-time that provided a repulsive force to balance the mutual attraction of all matter preserve a space which he envisioned as static in time.⁷

An alternative model of a static cosmos was developed in 1917 by the Dutch physicist Willem de Sitter.  De Sitter solved the problem of a collapsing universe by postulating that space was empty — devoid of matter.  As unrealistic as this may seem, the de Sitter universe was interesting in two ways.  First, if two small bits of matter were introduced (say, two galaxies in an otherwise empty universe) they would tend to move away from each other.  Second, the space de Sitter considered was flat — a departure from Einstein’s model, in which matter imposed an overall positive curvature on space such that the latter resembled the surface of a ball.  The actual universe seems to be very nearly flat and after an enormity of time will come to resemble a de Sitter universe.⁸

Lemaître wrestled with the problems of the de Sitter model while pursuing his Ph.D.  By that time, 1924, astronomical observers using more powerful telescopes had succeeded in finding distance indicators that established the spiral nebulae as galaxies like the Milky Way.  Hence the universe was not 100,000 light years across (the approximate diameter of the Milky Way), but rather billions of light years in size.  More significantly, observers found that the light of the more distant galaxies seemed shifted toward the red end of the color spectrum relative to nearby galaxies. Various explanation for this red-shift were offered.⁹

Lemaître’s time at Harvard enabled him to be engaged with the astronomical data, and by 1927 he understood how to interpret the galactic red shifts; galaxies were moving away from each other, but not by their own motion through fixed space. His was not the static universe of Einstein, or the empty cosmos of de Sitter, but rather a universe in which space itself was expanding, in which massive galaxies embedded in that space were carried into a future in which the cosmos became ever more dilute. Galaxies appear reddened not because of the classical Doppler Effect but because the light waves themselves are stretched out by the expansion of the space through which they travel. And unlike the original de Sitter model, no observer is in a special position, no galaxy occupies a “center.” ¹⁰

Lemaître was not the first to propose that an expanding universe would satisfy the equations of general relativity and eliminate the need for a cosmological constant.  Alexander Friedmann, a Russian mathematician, published a similar solution in German journals in 1922 and 1924. However, his was a purely theoretical exercise, as he did not have access to the data.  While Einstein was aware of Friedmann’s work, Lemaître — who was just finishing his thesis work when Friedmann died in 1925 of typhoid fever, was not.¹¹ Dissemination of journals was far more difficult then, and Lemaître would soon find himself on the other side of the same problem.

In 1927, Lemaître published his seminal paper on the expanding universe.¹² His expanding cosmos filled with matter combined the best of both Einstein’s and deSitter’s cosmologies, directly confronted the astronomical data at hand, and did not require a cosmological constant. In his universe, the velocity of recession of a galaxy would be proportional to the distance to that galaxy. He used the available astronomical data on galactic distances and redshifts to compute the constant of proportionality.¹³

Lemaître’s paper was virtually unknown and unread. The Annales of the Scientific Society of Brussels, published in French in Belgium, was simply not on the list of prominent scientific journals, nor was French a dominant language in astronomy. Two years later, in 1929, the American astronomer Edwin Hubble published a paper in the prominent Proceedings of the (US) National Academy of Sciences,¹⁴ in which he used the much larger body of data on galactic distances and velocities then available to show empirically that there was a linear relationship between the recessional velocity and distance of a galaxy.  The velocity-distance relationship he derived by plotting data on a chart became known as Hubble’s law, and the constant of proportionality the Hubble constant.

Hubble interpreted the recessional velocities of galaxies by appealing to de Sitter’s cosmology, in which particles would fly apart in a fixed space.  He also invoked what became known as “light fatigue” — light waves would lose energy and increase in wavelength as they traveled from source to observer.  Neither is correct: de Sitter’s model did not apply to the universe in which we live, and light does not lose energy as it travels through the vacuum of space.  It was Lemaître’s expansion of space itself that provided a natural mechanism for the ever-greater reddening of galaxies with distance.  But Hubble was unaware of Lemaître’s 1927 paper, and in any event never accepted the idea of a universe in which space itself was expanding.  As late as the 1940’s, Hubble gave interviews in which he asserted the data to be consistent with a static cosmos¹⁵ — an opinion now well-established to be erroneous.  Ironically, the man for whom the fundamental yardstick of cosmic expansion was named never accepted the idea that space was expanding.

The story would end here were it not for another consequence of Lemaître’s publishing in an obscure journal.  In 1930, Arthur Eddington produced an expanding universe model virtually identical to Lemaître’s and began to lecture on it.  Upon learning from colleagues of his old Cambridge mentor’s reinvention, Lemaître reminded Eddington that he had sent him a copy of the 1927 paper. The gracious Eddington realized immediately that his former student’s choice of journal had doomed the work to obscurity and arranged for the editor of the Monthly Notices of the Royal Astronomical Society, a distinguished journal informally known to astronomers as MNRAS, to publish an English translation.¹⁶

The 1931 English translation of the 1927 seminal paper did nothing to establish Lemaître’s priority in deriving “Hubble’s Law,” because the key paragraph setting forth the relationship between the recession speed of galaxies and their distance, and the constant relating them, was missing.  For decades intrigue swirled around this omission; theories ranged from anti-religious motives to Hubble himself intervening to save his own priority.  In 2011, astronomer Mario Livio solved the mystery after combing the archives of the Royal Astronomical Society, where he discovered a cover letter enclosed with the translated manuscript to the editor of MNRAS.¹⁷ The letter establishes that Lemaître had translated his own 1927 paper into English, and decided to omit the material on the galaxy velocity-distance relationship.

Why would Lemaître do such a thing?  He knew well that by 1929, when Hubble wrote his paper, there were more data of higher accuracy that established the linear nature of the velocity-distance relationship than he had access to in 1927.  When Lemaître wrote out the relationship in his original paper, he had derived it from his cosmological model, in effect predicting what better data would show two years later.¹⁸

By omitting the key paragraph, Lemaître lost the opportunity to have his name attributed to the famous and now fundamentally important cosmological relation.  Although it was easy to go back to the original 1927 paper to see what Lemaître had done, few apparently did.  Further, Hubble had a big personality and was in charge of what was the largest telescope at the time — the Mount Wilson 100-inch reflector; as a public figure he easily overshadowed low-key Belgian priest-professor.

The story of Lemaître’s contributions to cosmology does not end there. By 1931, he had thought through the implications of his model of the cosmos, and realized that the expansion implied a beginning — a point in time at which space and all the matter within it was so compressed that the physical laws which govern the behavior of everything might not have applied.  In four short paragraphs in the journal Nature, Lemaître set forth the case for a universe with a finite age, whose expansion when reversed implied a starting point so alien to the conditions found in the laboratory that normal physics would fail to describe it.¹⁹ What came to be known as the “Big Bang” model²⁰ for the origin of the cosmos remains with us today, and Lemaître is universally acknowledged to be its inventor. Much has changed from the original idea; Lemaître favored a cold starting state and interpreted the then recently discovered cosmic rays to be a signature of the beginning.  Today, we know that the starting state was very hot and the signature of the Big Bang is not cosmic rays, but rather a background field of mostly radio energy at a very low and almost uniform temperature — the “cosmic microwave background” or CMB.  When the CMB was discovered in 1964, Lemaître was literally on his deathbed where he learned of the validation of his model from friends.

While the public was fascinated with the idea of Lemaître’s model, and, even further, that it was invented by a Catholic priest-scientist, many of Lemaître’s colleagues were less charmed.  That the universe would have a beginning was scientifically unattractive, since it meant that some state of reality might not be accessible to scientific investigation.  And it smacked of religion — a kind of scientific version of Genesis.  Lemaître, who firmly asserted that his “primeval atom” model was a scientific hypothesis,²¹ found himself at the center of a firestorm when in 1951 Pope Pius XII opened a meeting of the Pontifical Academy of Science by asserting that the primeval atom model demonstrated the existence of a Creator.  The so-called “Fiat Lux” speech so mortified Lemaître that, learning of the Pope’s plans to read it again at the opening of the much larger IAU assembly in Rome, he traveled to the Vatican to plead (successfully) with the Holy Father to omit the offending portion.²²

However, the damage had been done, which was to confirm the assumption by some of its opponents that what was by now called the “Big Bang” model had been religiously motivated. Several years prior to the 1951 Fiat Lux speech, three physicist-astronomers—Thomas Gold, Hermann Bondi, and Fred Hoyle—proposed an alternative “Steady State” model of an eternally expanding universe in which matter was being continuously created to compensate for the dilution associated with the expansion of space.²³ While some argued that the Steady State model resolved what at the time seemed to be too small an age for the cosmos,²⁴ the required continuous creation of matter had no compelling mechanism.  Though the Steady State model was discredited by the discovery of the CMB, astronomers still seek ways to avoid what remains for many a philosophically unpleasant idea that the cosmos might have had a beginning.²⁵  Over the years, Lemaître produced a wide range of quotable statements on the relationship of science and faith, in which he carefully circumscribed both the practice of science and the applicability of the Bible to topics beyond salvation history.²⁶ Nonetheless, a closer examination of Lemaître’s 1931 Nature paper reveals a somewhat more permeable boundary between these two sides of the scientist-priest.  An archived early draft of the 1931 manuscript includes a final, additional paragraph, crossed out in pen.  The paragraph reads, “I think that everyone who believes in a supreme being supporting every being and every acting [sic], believes also that God is essentially hidden and may be glad to see how present physics provides a veil hiding the creation.” ²⁷  Lemaître’s motive for including this statement in an early draft of a paper to be sent to a scientific journal is unclear, but it is fully consistent with his views expressed elsewhere, that God is hidden in, and operates through, the physical laws of the cosmos.

More intriguing is that much of the second paragraph of the 1931 Nature paper echoes very closely the musings of St. Augustine on the nature of time.  Here Lemaître writes,

If the world has begun with a single quantum, the notions of space and time would altogether fail to have any meaning at the beginning; they would only begin to have a sensible meaning when the original quantum had been divided into a sufficient number of quanta.²⁸

The statement is as much philosophical as it is physical — how can one define space or the progression of time, if there is but a single thing that does not interact with anything else?  In The City of God, written 15 centuries before Lemaître’s paper, Augustine of Hippo wrote:

“For if eternity and time are rightly distinguished by this, that time does not exist without some movement and transition, while in eternity there is no change, who does not see that there could have been no time had not some creature been made, by which some motion could give birth to change?”

Taking the definition of creature as some thing that interacts with other things in the cosmos, the two ideas are essentially identical and phrased quite similarly.  Lemaître then goes on to say, “If this suggestion is correct, the beginning of the world happened a little before the beginning of space and time,” ²⁹ while St. Augustine wrote, “Then assuredly the world was made, not in time, but simultaneously with time.”  The two ideas are identical; “a little before” is only trivially different from “simultaneous” in this context.³⁰

One must imagine that Lemaître’s classical education, perhaps his formation as a priest, provided him with a knowledge of St. Augustine’s writings.  However, there is no citation of St. Augustine’s work in the Nature paper, and if the close correspondence with the text in The City of God was unintentional, it surely indicates that at some point in Lemaître’s life Augustine’s musings on time had made a big impression on him.  It also bears noting that the ideas expressed in those two sentences are not essential to the main idea of the paper: that the expansion of a matter-filled cosmos implies an ultra-dense beginning a finite amount of time ago.  But whatever the reason for the inclusion of these sentences, they provide a striking connection between modern cosmology and 5^th century Catholic theology.

Lemaître’s contributions to cosmology did not stop with the 1931 Nature paper.  Up until World War II, he published a number of important papers that demonstrated again and again his ability to engage observational data with his rigorous solutions to the equations of general relativity.  For example, grappling with the cosmological constant that Einstein disavowed, he proposed in a rigorous mathematical treatment that it might be a kind of vacuum energy, exerting a negative pressure that would accelerate the expansion of the cosmos. This presaged quite closely the idea of dark energy.³¹

Why then is Lemaître’s name not as well known as Hubble, or even Einstein?  By the end of World War II, the center of action in cosmology and the elaboration of the Big Bang model had moved from general relativity to nuclear physics, a field which simply did not interest Lemaître.³²   The contentious atmosphere surrounding the Fiat Lux speech and the Steady State model soured Lemaître further.  He remained a dedicated professor, pioneering high performance computing in Belgium, but in the end produced few students in cosmology as his legacy.  By the 1970’s most of Lemaître’s peers had died, and his contributions in large part became undervalued in publications from then until about a decade ago when interest in his life was rekindled.³³

The case for renaming Hubble’s law the Hubble-Lemaître law rests upon both the timing of the 1927 paper and Lemaître’s unique ability to provide the mathematically sound cosmologies while engaging directly with the astronomical data.  Friedmann first published an expanding universe model, but did not explore the implications for the relationship of galactic recession velocity to distance which bears Hubble’s name.  Hubble fitted astronomical data to obtain that relationship, but did not know how to derive it from general relativity.  Others applied general relativity to the shape and evolution of the cosmos but either used the wrong model or did not grapple with the data.  Had Lemaître published his 1927 paper in a major English language journal, one that would have been widely read by the astronomers of the day, the combination of his expanding mass-filled universe with his explicit derivation of the velocity-distance relation might have been much more widely recognized.

While few discoveries in science are correctly attributed to their discoverers,³⁴ I would argue that this case is special, and that Lemaître really was undervalued despite awards earned in his lifetime.  Lemaître’s religious identity is relevant here — at every talk I give on this subject, audience members express surprise, even amazement, that a Catholic priest could be a scientist, let alone such a prominent one.  Appropriately recognizing Lemaître’s name in the history of astronomy, by accepting the recommendation of the IAU to use the term “Hubble-Lemaître law.” will benefit scientist-believers and scientist-atheists alike.  For the former, it strengthens our case that science and faith are compatible.  And for the latter, it might just help remove the suspicion that Lemaître has been treated differently from his peers, both in his lifetime and thereafter, because of the collar he wore.³⁵

[This article first appeared in the Church Life Journal and is used with their kind permission.  Prof. Lunine is the Vice President of the Society of Catholic Scientists.]

References

1.. Dominique Lambert, The Atom of the Universe: The Life and Works of Georges Lemaitre (Kraków, Copernicus Center Press, 2016).

2.. John Farrell, The Day without Yesterday: Lemaître, Einstein, and the Birth of Modern Cosmology (New York, Basic Books, 2005).

3.. Graduate study in astronomy at Harvard did not officially begin until 1928 (https://astronomy.fas.harvard.edu/history  ).  Thus, Lemaître, who arrived at Harvard in 1924, had to matriculate at nearby MIT in order to obtain his PhD.

4.. Georges H.J.E. Lemaître, (1) The gravitational field in a fluid sphere of uniform invariant density according to the theory of relativity; (2) Note on de Sitter’ Universe; (3) Note on the theory of pulsating stars. PhD Dissertation, MIT, 1925, available from D-space@MIT at https://dspace.mit.edu/handle/1721.1/10753 ).  The notes “on de Sitter’s universe” and “on pulsating stars” were not included in the thesis copy deposited in the library; the all-important first of these two was however published by Lemaître in the Journal of Mathematics and Physics, vol. IV, no. 3, May 1925.

5.. Ideas ranged from smaller systems of stars to individual solar systems in the process of formation; see Robert W. Smith “Cosmology 1900-1931,” in Cosmology: Historical, Literary, Philosophical, Religious, and Scientific Perspectives, ed. Norris S. Hetherington (New York, Garland Publishing, 1993), 329-345.

6.. By 1913, telescopic observations showed that the Andromeda nebula, soon to be revealed definitely as a spiral galaxy, was rushing toward us at a very high speed, while within a few years other galaxies would be shown to be receding.  But the sparsity of data prevented inference of a general expansion of the cosmos until Lemaître and Edwin Hubble came on the scene a decade later. See Robert. W. Smith, op. cit.

7.. Albert Einstein, “Kosmologische Betrachtungen zur allgemeinen Relativitätstheorie,” Prus. Akad. Wiss. Vol. 142, 1917, 142-152.

8.. See, for example, Lawrence M. Krauss and Robert J. Scherrer, “The return of a static universe and the end of cosmology,” General Relativity and Gravitation, Vol. 39, No. 10, 2007, 1545-1550.

9.. The light of galaxies was spread out according to wavelength at the telescope through the use of “spectrometers.  Because galaxies are made up in large part of stars, whose atmospheres contain atoms that absorb light at definite wavelengths, astronomers could see the same pattern of dark lines in the spectrum from one galaxy to another, but in many cases shifted to the red relative to the pattern one would see in the laboratory.  It is possible in this way to measure very precisely the amount of the so-called “red shift” for a given galaxy.

10.. It is difficult to imagine space without a center; after all, if the galaxies are receding, what are they receding from?  The easiest way to visualize such a reality is to consider the surface of a balloon as a two-dimensional analog to three-dimensional space.  Inflate the balloon, and draw dots all over the resulting surface.  Note that no dot is at the center, every dot is at rest in its local spot on the balloon’s surface, and yet as you inflate the balloon, the perspective from every dot is that all other dots are moving away from it.  (The dots themselves, drawn by pen, get bigger, but the real galaxies do not).  By using a ruler, you can also show that the further one dot is from another, the faster it seems to recede — by just the proportionality law Lemaître inferred for his model.  The difficulty with this analogy is that inevitably one fixates on the space outside and inside of the balloon — an extra spatial dimension that has no correspondence with anything in most models of the actual expanding universe.

11.. Helge Kragh and Robert W. Smith, “Who discovered the expanding universe,” History of Science, vol. 41, no. 2, 2003, 141-162.  In 1958, Lemaître stated that he was made aware of Friedmann’s papers in a meeting with Einstein in late October 1927, months after his own paper (note 12) appeared. In view of the subsequent events regarding Hubble’s work, described in this article, there is little reason to disbelieve Lemaître.

12.. G. Lemaître, “Un univers homogene de masse constante et de rayon crossant, rendant compte de la vitesse radiale des nebuleuses extra-galactiques,” Annales de la Societe Scien- tifique de Bruxelles A, vol. 47, 1927, 49-59.

13.. A megaparsec is the conventional unit of distance used by extragalactic astronomers.  One parsec is 3.26 light-years, and a megaparsec is a million parsecs, or roughly thirty million trillion kilometers.

14.. Edwin Hubble, “A relation between distance and radial velocity among extra-galactic nebulae,” Proc. National Academy of Sciences, Vol. 15, 1929, 168-173.

15.. See, for example, “Savant refutes theory of exploding universe,” The Los Angeles Times, December 31, 1941, 10.

16.. Georges Lemaître, “A homogenous universe of constant mass and increasing radius accounting for the radial velocity of Extra-galactic nebulae,” Monthly Notices Royal Astronomical Society, vol. 91, 1931, 483-490.

17.. Mario Livio, “Mystery of the missing text solved,” Nature, Vol. 479, 171-173.

18.. In his 1927 paper, Lemaître averaged the data on galactic distances and velocities to obtain his constant, rather than fitting the data to a straight line.  Given the limitations in the amount and precision of the data at the time, this was the right thing to do, since Lemaître knew that his model of the universe — the primary point of the paper — determined the form of the velocity-distance relationship.

19.. Georges Lemaître, “The beginning of the world from the point of view of quantum theory,” Nature, Vol. 127, 1931, 706,

20.. Lemaître never used this term; it was a derogatory nickname for the model coined by one of its most prominent opponents, the astronomer Sir Fred Hoyle. See [2].

21.. “As far as I can see, such a theory [the Big Bang] remains entirely outside any metaphysical or religious question. It leaves the materialist free to deny any transcendental Being.” Quoted in M. Godart and M. Heller, Cosmology of Lemaître (Tucson, AZ, Pachart Publishing House, 1985).

22.. The details of Lemaître’s intervention differ in various accounts, in particular, whether he spoke directly to the Pope, and if not, then who actually intervened with the Holy Father.  The English language version of the original Fiat Lux speech can be found at http://inters.org/pius-xii-speech-1952-proofs-god.

23.. Hermann Bondi and Thomas Gold, “The Steady-State Theory of the Expanding Universe,” Monthly Notices Royal Astronomical Society, 108, 1948, 252-270; Fred Hoyle, “A new model for the expanding universe”. Monthly Notices Royal Astronomical Society, 108, 372-382.

24.. This problem was solved in the 1950’s and 1960’s by improved measurement of distances to galaxies, which lowered Hubble’s constant and increased the time since the Big Bang.

25.. See, for example, Roger Penrose, Cycles of Time: An Extraordinary New View of the Universe (New York, Vintage Press, 2012); Alan H. Guth, “Eternal inflation and its implications,”  Journal of Physics, A40, 2007, 6811-6826.

26.. The Christian researcher’s faith “has directly nothing in common with his scientific activity. After all, a Christian does not act differently from any non-believer as far as walking, or running, or swimming is concerned.” Quoted in Godart and Heller, op cit.

27.. Jean-Pierre Luminet, “Editorial note to: Georges Lemaître, The beginning of the world from the point of view of quantum theory,” General Relativity and Gravitation, 43, 2011, 2911-2928.

28.. Georges Lemaître, “The beginning of the world from the point of view of quantum theory,” Nature, Vol. 127, 1931, 706.

29.. Ibid.

30.. All Civ. Dei quotes from: Augustine of Hippo, The City of God, Marcus Dods, translator, in Augustine, (Great Books of the Western World, Vol. 18 (Chicago, Encyclopedia Britannica, 1952), 325.

31.. George Lemaître, “Evolution of the expanding universe,” Proceedings of the National Academy of Sciences, vol. 20, 1934, 12-17.  The Harvard astronomer Robert Kirshner wrote, “In 1934, Lemaître associated a negative pressure with the energy density of the vacuum and said, ‘This is essentially the meaning of the cosmological constant.’ That is exactly the way we talk about dark energy today.” Robert Kirshner, “Review of The Day We Found the Universe; Discovering the Expanding Universe,” Physics Today, vol. 62, no. 12, 2009, 51.

32.. Ralph Alpher, Hans Bethe and George Gamow, “The origin of the chemical elements,” Physical Review 73, 1948, 803-804.

33.. I believe that John Farrell’s book [2] was influential in this regard, as was the collection of papers in Rodney Holder and Simon Mitton, eds. Georges Lemaître: Life, Science and Legacy (Heidelberg, Springer, 2012), along with other articles and books published in the last 15 years.

34.. Stigler’s law of eponymy states that “no scientific discovery is named after its discoverer.” Stephen M. Stigler, “Stigler’s law of eponymy,” Proceedings New York Academy of Sciences, vol. 39, no. 1, series II, 1980, 147-157.

35.. Lemaître was recognized in his lifetime with the Francqui Prize (he was nominated by Einstein).