El universo de Georges Lemaître

The world of Georges Lemaître

Author: Eduardo Riaza Molina
Author of the blog Georges Lemaître
Published at: article unpublished
Date of publication: January 2011

"The theory of the big bang, the 'big explosion' that would have originated our world, belongs to the general culture of our time; but few know that it was originally proposal by Georges Lemaître, physicist and catholic priest".1. Lemaître was able to arrive at this cosmological model thanks to his adherence to a realistic Philosophy and his ability to combine theoretical reasoning with astronomical observations.

Physics in Lemaître's time

The cosmological model of the big bang was forged in the first half of the 20th century, marked by a crisis that influenced all fields. In the field of the arts, for example, the classical moulds were broken, leading to non-figurative painting, the theatre of the absurd and atonal music.

This crisis even affected science, for the confidence of positivist man collapsed with the advent of the new physics. Quantum and relativistic theories gave a different view of reality: "the real elements were not the atoms of the Chemistry, but the waves of electrons and protons, whose mutual interactions were governed by the speed of light and the quantum of energy".2. Things were not as simple, as "explainable" as they seemed in the previous century, when faith in the capacity of human reason was absolute.

Art changed because the author's mentality and his concept of things changed. Science, however, did not change because of whim or fashion, but because the nature of what was observed turned out to be different from what was previously supposed: it was the reality observed that forced it to change. This is how Max Planck - the initiator of quantum theory - put it in a lecture given in November 1941: "This changeover becomes a bitter necessity every time the scientific research stumbles upon some new fact in nature for which the established way of representing the world is unable to provide an explanation".3.

Some scientists gave up a rational understanding of deeper realities in the face of this bewildering prospect. For others, the new physics implied a different way of thinking: assuming that "the world of sensory perceptions was not the only one to which one could conceptually attribute existence, but that there was also another world to which [...] we could not have direct access [...], but which inexorably impelled the researcher to seek its form final. And since it was necessary to assume the existence of that which was being sought, the conviction that there really existed, in the absolute sense of the term, a real world, had to become firmly rooted in him".4.

Unravelling this real world was no easy task. The researcher could not be satisfied with bringing to light what was hidden in the apparent chaos. He had to "admit the universal truth successively discovered, like an unknown land that was being explored and colonised".5. This was the attitude of certain researchers of the time. Among them, Lemaître.

Lemaître's academic training

Georges Lemaître was no stranger to this context. However, the scepticism into which some people fell was not lost on him. The solid religious training he received from his family and the love of classical culture instilled in him in the Jesuit schools where he studied led him to search passionately for the truth. As he himself said in an interview: "I was as interested in truth from the point of view of salvation as I was in truth from the point of view of scientific certainty. It seemed to me that there were two roads that led to truth, and I decided to follow one and the other".6.

His childhood was very normal. He was a cheerful and communicative boy, who showed no particular inclination for anything. However, one of his teachers - Father Henri Bosmans - marked his career guidance: he gave him a taste for the history of mathematics, encouraging him to read the original texts of the mathematicians of Ancient Greece - especially Euclid - and to read the mathematics of the Ancient Greeks.7He encouraged him to read the original texts of Ancient Greek mathematicians, especially Euclid, and other more modern ones, such as Euler or Laplace...

When he arrived at university, he was not satisfied with a few technical engineering courses at programs of study . His eagerness to go further led him to enrol at School at Philosophy. Some of these classes were taught by Désiré Mercier, the future Cardinal of Mechelen, who would go on to found the priestly fraternity The Friends of Jesus, to which Lemaître would eventually belong.

Since childhood he had dreamed of becoming a priest, but his piety matured when he participated as a volunteer in the First World War. During the war he had time to read and think. One author who caught his attention was Léon Bloy. He was attracted to the religiousness of this philosopher: reflective, critical, full of love for the poor and simple. This more intense spiritual life made him feel the need to seek, from time to time, time exclusively for God. In these moments of meditation, he decided to change the programs of study of engineering for those of Physics and Mathematics, and later to enter the seminar of Mechelen.

While he was at seminar, a book fell into his hands.8 on Albert Einstein's theory of relativity. It had been written by Arthur Eddington, who became the main English-speaking popularizer of the German physicist's work. He was so captivated by the new theory that, as soon as he was ordained a priest, he went to the Cambridge Observatory to study it in depth under the tutelage of Eddington himself, with a scholarship that he had obtained from the Belgian government.

Lemaître's people skills and extraordinary talent helped Eddington to involve him in his scientific research. He explained to him the mechanisms that cause the energy radiated by stars and the correspondence between their mass and their luminosity and, more importantly, taught him to relate astrophysics to the theory of relativity.

Moreover, the two men were united in their love of truth. Lemaître's contemplative spirit was a passion to reach the great and universal truth of the cosmos. Eddington, as a Quaker, was constantly impelled to enquire: "In science and in religion the truth shines before us like a beacon showing the way; we do not ask to reach it; it is far better that we should be permitted to seek".9. This was another reason why the two hit it off so well.

The following academic year, 1924-25, he travelled to the United States to carry out the doctorate between Harvard College Observatory and the Massachusetts Institute of Technology (MIT), after obtaining another scholarship from research. There he became proficient in calculating stellar distances, using the observation of stars of varying brightness, called Cepheids. He also visited the Mount Wilson Observatory to discuss with Edwin Hubble the redshift he had detected in the spectrum of light from other galaxies.

The origin of the idea of an expanding universe

After academic year he returned to Belgium, where he began to teach at the University of Louvain thanks to a letter of reference10 that his Cambridge professor - Arthur Eddington - had sent them. In those early years of teaching he finished his thesis doctoral thesis and wrote an article11 in the Annales de la Société Scientifique de Bruxelles in which he gave a solution to the equations of the general theory of relativity, interpreting the redshift as a manifestation of the expansion of the universe.

Lemaître tried to calculate the velocity at which galaxies are moving away from each other, but the value obtained was higher than the present one. This quantity was so enormous that it led him to think that in the very recent past the size of the universe must have been much smaller. If the rate of expansion had always been the same, the age he would have to assign to the universe would be lower than that obtained for the Earth.12. Since this did not make sense, Lemaître preferred to consider an exponentially expanding world with an infinite past, where its size was almost constant at first, and then grew rapidly.

As early as 1922 the Russian mathematician Alexander Friedmann had found several solutions to the Einstein equations, some of which described expanding and some contracting universes.13 to Einstein's equations, some of which described expanding universes and others contracting universes. But Friedmann died prematurely and did not have the opportunity to test his mathematical calculations against the astronomical data of the time.

The idea of an expanding universe did not appeal to the academic community, because since antiquity all theories of celestial motion had advocated the conception of a universe that was globally static, stable and therefore immutable and eternal. Einstein, who was influenced by Spinoza's pantheism, was irritated by Friedmann's and Lemaître's work because he expected his proposed solution to be the only possible description of the universe.

Eddington was the exception. Not only did he admit the expansion of the universe, but he acknowledged that he had been outdone by his disciple: "Working with Professor McVittie, several months ago I carried out investigations in order to clarify whether Einstein's spherical universe is stable. Before our analysis was completed, we read the priest Lemaître's article , where several questions concerning Einstein's and De Sitter's cosmological constructions are excellently and completely resolved. My goal was to analyse the problem from the astronomical point of view, although my initial desire to obtain a concrete result , new in principle, was overtaken by Lemaître's brilliant solution".14. And from then on, Eddington became Lemaître's great supporter: he sent his work to several scientists and had a conversation with Einstein.15 and had a conversation staff with Einstein, trying to convince him. After a while, the German physicist finally gave in.

The story of the beginning

Lemaître had no problem in positing a universe with an infinite past. His programs of study of Philosophy Thomistic had shown him that this did not contradict his belief in a world-making God.16 had shown him that this thesis did not contradict his belief in a God who made the world, since a created universe does not need a beginning in time. We know the temporal origin of the cosmos through supernatural Revelation, but in theory nothing would prevent God from having created the universe from all time. Even if time were infinite - both in the past and in the future - it would still have a cause. Temporality and eternity move on different planes: eternity occurs all at once, while time is the succession of before and after. When it is affirmed that God is eternal, something different is said from a simple indefinite duration. Divine eternity is the possession of Being, unchanging, without before or after, in a wholly self-sufficient manner. And this can never occur in a limited being, such as the universe, for it requires a cause.

However, this cosmological model proposed by the Belgian astrophysicist in 1927 would not be the definitive one. In 1931, Eddington gave a lecture in London on the end of the world from the point of view of mathematical physics. lecture17 in London on the end of the world from the point of view of mathematical physics. Relying on the thermodynamic concept of entropy -Degree of disorder from subject-, he concluded that the cosmos would in the future reach a state of complete dispersion, a total disorganisation of the subject. Going into the past, on the contrary, the order would tend to be complete, inviting to think of a beginning for the world, a matter that Eddington strongly rejected.

This refusal by the Cambridge professor aroused in Lemaître a lively interest in the question of the origin of the cosmos.18. For years he had been considering the possibility of understanding infinity. Because he perceived the difficulty of the human mind to conceive completely of an infinite space and time, and because he had a deep confidence in the rationality of the world and in the capacity of human intelligence to reach the truth, he asked himself whether it was compatible with physics that the universe had a beginning. Finding no contradiction, he set about reformulating his cosmological model , starting from quantum mechanics.

To adjust his new theory, he added an initial phase to the two proposed in the previous model to give the universe a finite age. It all began at a point, where the laws of physics lost all meaning, where the universe expanded and space was "filled" with the products of the decay of the early atom19 -disintegrations similar to those of radioactive substances-, which gave rise to subject, space and time as we know them today. Gravitational attraction gradually slowed this expansion until it reached a stage of virtual equilibrium. At that time galaxies and their clusters arose from local accretions of subject. When the training of these Structures came to an end, the expansion resumed in a hurry.

Philosophy and science in the big bang theory

As a theoretical physicist, Albert Einstein did not bother to experimentally test any of his claims, although he said he was "willing to consider his theory untenable if it did not stand up to certain tests".20. He had read David Hume's "Treatise of Human Nature" and identified with its scepticism, and was later attracted to the thought of Ernest Mach - Austrian philosopher and physicist - who took Hume's empiricism further.21With such influences, Einstein remained at odds with the positivism inherited from these philosophers and the theoretical approach of his finding. sample of this was his resistance to admitting the expansion of the universe and the introduction of the cosmological constant in his equations in order to achieve a world in accordance with his thinking: an immutable and eternal universe. He would later admit that the latter had been the biggest mistake of his life.

With the disappearance of these prejudices, Einstein's empiricism softened into a belief in an objective reality.22. He went so far as to assert that physical theories tried to give "a picture of reality and to establish its relation to the wide world of sensory impressions", and that our mental would be acceptable to the extent that our mental theories would be acceptable to the extent that our mental theories could be accepted.23and that our mental Structures would be acceptable to the extent that they achieved that relation. However, Einstein never admitted that the cosmos could have had a beginning; his pantheistic idea of the world prevented him from admitting such a thing. Moreover, he believed that Lemaître wanted to introduce divine creation into science.

On the other hand, historians do not agree at agreement on Arthur Eddington's philosophical thought, since his metaphysics is very ambiguous. Some describe him as an idealist, even a mystic, others as a neutral monist close to Bertrand Russell.24. Although Eddington combined theory and internship, his eclecticism prevented him from seeing beyond the theory of relativity and astronomical observations: he believed that the problem of the causality of the world could be solved by proposing a less abrupt beginning. He therefore preferred to consider a very small and compact universe, not unlike Lemaître's primitive atom, which gradually expanded until it reached the present status .25.

For his part, Lemaître did not seek to exploit science for the benefit of religion; he was firmly convinced that the two have different paths to the truth. The autonomy of science from faith was proved when he declared that, "from a physical point of view, everything happened as if theoretical zero were really a beginning; to find out whether it was truly a beginning or rather a creation, something that starts from nothing, would be a philosophical question that could not be resolved by physical or astronomical considerations".26.

Lemaître, because of his solid humanistic training , his adherence to a realist Philosophy based on Aristotle and Thomas Aquinas27 and, by combining quantum and relativity theories with experimental data , he was able to formulate the big bang theory. A cosmological model which was later to be qualified by George Gamow and many others, but which retains its originality.28 and many others, but which retains its main idea: an immensely large universe that we access through the knowledge of the extremely small, which leads us to overcome the paradox of the existence of an initial physical instant, breaking with the static vision of the cosmos that had been held up to that time.


(1) ARTIGAS, Mariano, "el origen del universo. Georges Lemaître: el padre del big-bang", in ACEPRENSA, 79/95, 7 June 1995.

(2) PLANCK, Max, Autobiografía científica, Madrid, Nivola, 2000, p. 86.

(3) Ibid. p. 87.

(4) Ibid. p. 90.

(5) YEPES, Ricardo, Entender el mundo de hoy, Madrid, Rialp, 1993, p. 63.

(6) AIKMAN, Duncan, New York Times Magazine, 19 February 1933, p. 3.

(7) Cf. LAMBERT, Dominique, Un atome d'univers. La vie et l'oeuvre de Georges Lemaître, Brussels, Ed. Lessius, 2000, p. 28.

(8) EDDINGTON, Arthur, Space, Time and Gravitation: An Outline of the General Relativity Theory, Cambridge University Press, 1920.

(9) EDDINGTON, Arthur, Science and the Unseen World, New York, The Macmillan Company, 1929, p. 23.

(10) Cf. LAMBERT, Dominique, Un atome d'univers. La vie et l'oeuvre de Georges Lemaître, Brussels, Ed. Lessius, 2000, p. 70.

(11) LEMAÎTRE, Georges, "Un univers homogène de masse constante et de rayon croissant, rendant compte de la vitesse radiale des nébuleuses extra-galactiques", in Annales de la Société Scientifique, Brussels, 1927.

(12) The estimated age of the Earth at that time was 2 billion years. Today we give it a value in the order of 4.5 billion years.

(13) Cfr. FRIEDMANN, Alexander, The Universe as Space and Time, Seville, Ed.

(14) Cfr. HELLER, Michal and DAVÍDOVICH, Artur, Friedman y Lemaître, Sevilla, Ed. URSS, 1991, p. 63.

(15) Willem de Sitter (Netherlands) and Harlow Shapley (USA).

(16) Cfr. AQUINO, Tomás de, Sobre la eternidad del mundo, Madrid, Ed. meeting, 2002.

(17) EDDINGTON, Arthur, "The end of the World from the standpoint of Mathematical Physics", in Nature, March 1931 No. 3203, pp. 447-453.

(18) Cf. LAMBERT, Dominique, Un atome d'univers. La vie et l'oeuvre de Georges Lemaître, Brussels, Ed. Lessius, 2000, p. 111.

(19) Lemaître thought that initially there was a "primitive atom" from which all the subject and energy of the universe came from.

(20) ARTIGAS, Mariano, Karl Popper: búsqueda sin término, Madrid, Magisterio Español, 1979, pp. 16-17.

(21) Cfr. ISAACSON, Walter, Einstein. Su vida y su universo, Barcelona, discussion, 2008, pp. 110-111.

(22) Ibid. pp. 500-501.

(23) EINSTEIN, Albert and INFIELD, Leopold, La evolución de la física, Barcelona, Salvat, 1995, p. 236.

(24) Cfr. MARTÍN, Karim Gherab. "Philosophy de la ciencia y monismo neutral en Arthur S. Eddington", in THÉMATA, Revista de Philosophy, Núm. 36, 2006. pp. 101-127.

(25) Cfr. SINGH, Simon, Big Bang, Barcelona, Library Services Budirán, 2008, p. 250.

(26) LAMBERT, Dominique, Un atome d'univers. La vie et l'oeuvre de Georges Lemaître, Brussels, Ed. Lessius, 2000, p. 278.

(27) Ibid. p. 52.

(28) Cfr. GAMOW, George, La creación del universo, Madrid, Espasa-Calpe, 1963.