Justified True Belief

(●) The Belgian priest who found the expanding universe in Einstein’s own equations, and then followed the expansion back to the beginning of the world, the beginning now called the Big Bang. + In the autumn of 1927 a young Belgian priest in a black cassock fell into step beside Albert Einstein in a park in Brussels and tried to tell him that the universe was getting bigger. Einstein had read the paper. He made a few kind remarks about the mathematics and then said that from the point of view of physics the whole thing seemed to him abominable. Four years later Einstein changed his mind in public, and the priest turned out to have been right twice: right that the universe is expanding, and right that a universe expanding for a finite time backwards must have had a first moment. That priest was Georges Lemaître, professor at the Catholic University of Louvain and a priest of the diocese of Malines. He is the reason anyone speaks of a Big Bang at all. He drew cosmic expansion out of the equations of general relativity, which is Einstein’s account of gravity as the bending of space and time, not knowing that Alexander Friedmann had found the same solutions five years before him, and then he did the thing the other mathematicians were not doing: he took the result outside and checked it against the light of actual galaxies. He got the rate of the expansion out of that data two years before Edwin Hubble measured it, which is why the International Astronomical Union voted in 2018 to call the relation the Hubble-Lemaître law. Then, in 1931, he said the thing nobody else in the field was willing to say out loud: that the world had a beginning, and that time began with it. The signature fact about him is the one people expect least from a priest with a cosmology. When a pope announced from the chair that Lemaître’s cosmology had confirmed the doctrine of creation, Lemaître set out quietly to get the announcement dropped, and succeeded.

(●) 1894 AD: Born to a glassmaker in the Belgian coal country, and handed to the Jesuits at ten. + Georges Lemaître was born at Charleroi on 17 July 1894, in the industrial country south of Brussels that Belgians call the pays noir, the black country, for the coal that came out of it and the smoke that hung over it. His father Joseph ran a glassworks; his mother was Marguerite Lannoy. At ten he went to the Jesuits at the Collège du Sacré-Coeur in Charleroi, and by his second year the mathematics masters had noticed him. Then the glassworks burned. The family recovered, but a fire like that decides where a family lives, and this one moved them to Brussels in 1910, where Georges finished school at another Jesuit house, the Collège Saint-Michel. He is remembered as the kind of schoolboy who reads Euclid in the original Greek for pleasure and works his way through Euler and Gauss in Latin because that is the language they were printed in. In 1911 he entered Louvain to study civil engineering, which was the sensible course for an industrialist’s son, and which he never finished.

(●) 1914 AD: He volunteered in the first week of the war and spent four years in the trenches with a physics book in his kit. + Germany invaded neutral Belgium on 4 August 1914. Within days Georges and his brother Jacques had volunteered, and the engineering degree was set aside for the duration. He served first in the infantry, through the desperate stand along the Yser in October when the Belgian army held a flooded strip of its own country and then sat in it for four years, and later in the artillery. He did not stop working. Inside his copy of Poincaré’s Électricité et Optique he pencilled the successive positions of his battery, so that the book came home as a war diary as well as a textbook. At a course on ballistics, which is the mathematics of where a shell will land once it leaves the gun, he pointed out that the working in the official manual was wrong. He was correct, and being correct did him no good at all: the episode was noted against him as insubordination, and the commission he was in line for went elsewhere. He came out of the war decorated all the same, with the Belgian Croix de guerre with palms. Anyone who has met a veteran who will not discuss the war will recognise what happened next. Lemaître almost never spoke of those years afterward, and the few people who tried to draw him out got very little.

(●) 1923 AD: Ordained a priest in September, he sailed for Cambridge ten days later. + He came back to Louvain in January 1919 and did not go back to engineering. He took up mathematics and physics instead, and by 1920 he had his doctorate under Charles de la Vallée Poussin, with a thesis on approximating functions of several real variables. That October he entered the Maison Saint-Rombaut at Malines, a seminary running a shortened course for men whose vocation had arrived late. Seminarians are not usually encouraged to spend their evenings on tensor calculus, which is the mathematical machinery relativity is written in, and which is about as far from devotional reading as a page of print can get. Cardinal Désiré-Joseph Mercier, who ran the diocese and had spent his own career reviving the study of Thomas Aquinas, told this one to keep reading relativity, and ordained him on 22 September 1923. Ten days after his ordination he crossed to England. A dissertation on relativity and gravitation had won him a travelling scholarship from the Belgian government that summer, and he spent the year of it at Cambridge with Arthur Eddington, the astronomer who had made Einstein famous in the English-speaking world by measuring the bending of starlight during the eclipse of 1919. Eddington reported that he had found in Lemaître a brilliant student of great mathematical ability. From Cambridge he went to the Harvard College Observatory under Harlow Shapley, on a fellowship from the educational foundation that had grown out of the wartime Commission for Relief in Belgium, and registered at the same time for a doctorate at the Massachusetts Institute of Technology, which he took in 1927. That American year gave him the two things he needed, and neither of them was a lecture. He sat in a hall in Washington on New Year’s Day 1925 while Henry Norris Russell read out, for an absent Hubble, the paper announcing that the faint spirals in the sky are galaxies in their own right, far outside our own, so that the universe had just become unimaginably larger than anyone had been assuming. Then at Flagstaff in Arizona he saw the work of Vesto Slipher, who had patiently measured the colour shifts of some forty of them, the slight reddening that the light of a receding source carries with it. One man had told him how big the universe was. The other had left him a column of figures that nobody yet knew how to read. He went home with the numbers.

(●) 1927 AD: He published the expanding universe in a Belgian journal almost nobody read, and Einstein told him his physics was abominable. + The paper appeared in the Annales de la Société Scientifique de Bruxelles under a title that gives away the whole argument: a homogeneous universe of constant mass and increasing radius, accounting for the radial velocity of the extra-galactic nebulae. Nebulae is what people still called galaxies; the vocabulary had not caught up with the discovery. What he had done was this. Einstein’s equations of gravity, applied to the universe as a whole, do not naturally sit still: solve them without a thumb on the scale and the universe they hand you is either growing or shrinking. Einstein wanted neither, so in 1917 he had added an extra term to the equations, a kind of counterweight, to hold his model steady. Lemaître took the counterweight off and let the model move. Then, in the same paper, he went to the observations and showed that the light of the galaxies is doing exactly what a moving model requires. From Slipher’s colour shifts and the distances then available he read off a rate: a galaxy twice as far away recedes about twice as fast, at something like 625 kilometres per second for every megaparsec of distance, a megaparsec being a bit over three million light years. A footnote gives 575 and 670 as well, depending on how the same galaxies are grouped, which is a fair measure of how thin the data were. He was reading a law of the whole universe off a few dozen faint smudges of light, and he knew it. Two years later Hubble published the same proportion from better data, and it entered the textbooks under his name alone. In October Brussels hosted the fifth Solvay Conference, the small invitation-only congress where the physics of the century was being argued out. Lemaître was not invited to the sessions, but Louvain is twenty kilometres away, and he got his walk in the Parc Léopold. Walking beside him, Einstein said that a Russian named Alexander Friedmann had already done the mathematics in 1922. That was news to Lemaître, who had never seen the papers, and it was awkward news for Einstein, who had seen them and dismissed them at the time. Then came the verdict. Lemaître set it down in a memoir of his meetings with Einstein published thirty years afterward: some favourable remarks on the technical side, and then the conclusion that from the point of view of physics the thing seemed to him absolutely abominable. It is a strong word to use about a piece of work whose arithmetic you have just praised, and the young priest went home with it.

(●) 1931 AD: Eddington had the forgotten paper translated, and Lemaître answered him with the beginning of the world. + In January 1930 Eddington and Willem de Sitter were publicly stuck on one question: how to fit galaxies that are running away from us into a universe governed by Einstein’s equations. Lemaître read the report of the meeting, and it must have been an odd thing to read, because the answer was sitting in his own filing cabinet. He wrote to his old teacher to point out that he had published it three years earlier. Eddington, to his credit, was delighted, and arranged an English translation in the Monthly Notices of the Royal Astronomical Society in March 1931. A paragraph went missing in that translation: the one containing the rate of expansion. For eighty years the omission looked like theft, and Hubble’s admirers were the obvious suspects. In 2011 the astrophysicist Mario Livio went through the Royal Astronomical Society correspondence and the Lemaître archive and found the letter that settles it. Lemaître had done his own translating, and had cut the passage himself, on the ground that his own rough 1927 figure was of no actual interest now that Hubble had measured the thing properly. A man less interested in his own priority would be hard to find. Eddington then set the trap he did not know he was setting. He wrote in Nature that philosophically the notion of a beginning of the present order of nature was repugnant to him. Lemaître replied on 9 May 1931 with a letter of 457 words, and the reply proposed that the whole energy of the universe had once been packed into a single quantum, a quantum being the smallest indivisible packet that energy comes in, which then disintegrated. He called it the primeval atom. It has been called the charter of Big Bang cosmology, and it is shorter than most book reviews. The twenty years that followed were the ordinary working life of a professor, and he had one from 1927 until he retired in 1964. He lectured across the United States in 1933, and at a Mount Wilson Observatory seminar near Pasadena that January, with Einstein sitting in the room, he set out the primeval atom and the cosmic rays he took for its relics; Einstein is reported to have stood up and applauded. He went back to the Massachusetts Institute of Technology to work with the Mexican physicist Manuel Sandoval Vallarta on how the earth’s magnetic field bends the cosmic rays that come in from space, which is how he became one of the first physicists anywhere to hand a hard problem to a computing machine. He watched his country invaded a second time in 1940 and taught through the occupation. And in 1946 he gathered his case for a beginning into the one book he wrote for ordinary readers.

(●) 1951 AD: A pope announced that his cosmology had proved creation, and he went quietly to work to stop him. + Pius XII had a serious interest in the sciences and a habit of preparing his own addresses. On 22 November 1951 he spoke to the Pontifical Academy of Sciences, to which Lemaître had belonged since 1936, and argued that modern cosmology had brought natural science round to the moment of creation. Lemaître was not in the room, kept away that week by other scientific engagements, and when word of the address reached him he was not pleased. His objection came in two parts, and neither of them was embarrassment. The first was simply that the theory was not settled. There was a serious rival on the table, the steady-state account, in which the universe has no beginning at all and new matter is quietly made in the gaps as it expands, so that on the large scale it looks much the same at every moment of its history. Good physicists defended that account, and would go on defending it for another fourteen years. The second objection was the deeper one, and it is the thing he cared about most. A first physical state is not the same thing as creation. Weld a doctrine to a physical theory and you have tied its fate to that theory’s fate, the way a lean-to comes down with the wall it was built against. With the help of Daniel O’Connell, the Jesuit who directed the Vatican Observatory, and Monsignor Angelo Dell’Acqua of the Secretariat of State, he obtained an audience with the pope. What passed between them was not recorded, and nobody should pretend to know. What is on the record is that when Pius XII spoke to the International Astronomical Union in Rome on 7 September 1952, he made no such identification again, and never returned to it. The Vatican’s regard for him did not suffer. In March 1960 John XXIII made him a domestic prelate, so that he became Monsignor Lemaître, and appointed him president of the Pontifical Academy of Sciences, which he remained until his death.

(●) 1966 AD: He heard that the echo of the beginning had been found, and died within days. + He had always expected the beginning to have left something behind. If the world had really started hot and crowded and then flown apart, some remnant of the first firework ought still to be arriving, and in a paper of 1934 he said so and named what he thought it would be. He named the wrong thing. He picked the cosmic rays, the stream of fast particles that reaches the earth from space in every direction, and the cosmic rays are not the relic. In 1965 Arno Penzias and Robert Wilson published their measurement of something he had not picked: a faint microwave hum coming from every direction of the sky at once, the cooled glow of a universe that had once been hot and dense everywhere. That was the relic. Thirty-one years after he had gone looking in the wrong place, the thing he had said should be there was there. By then he was very ill. He had had a heart attack in December 1964, had taken emeritus status, and was dying of leukaemia in a hospital in Leuven, and it was there that his old student and colleague Odon Godart brought him the news. The vindication of a life’s work reached him in a hospital room, secondhand, from a friend. He took it in, and was content. He died on 20 June 1966, at seventy-one.

What He Taught

(T1) The universe is not standing still, and the fleeing galaxies are space itself stretching. + Put a raisin loaf in the oven. As the dough rises, every raisin gets further from every other raisin, and the further apart two raisins started, the faster they draw apart. No raisin is at the centre. Nothing is travelling through the dough. The dough is getting bigger, and the raisins are simply along for the ride. That is Lemaître’s universe, with galaxies for raisins. The evidence for it is a colour shift. Light from a source moving away from us arrives stretched toward the red end of the spectrum, the way the siren of a passing ambulance drops in pitch once it is going away from you, and astronomers call that stretch a redshift. Vesto Slipher had found that almost every galaxy he measured was redshifted, and nobody knew what to make of it. Lemaître made this of it. General relativity, Einstein’s theory of gravity as the shape of space and time, applied to the whole universe, gives you a universe that must expand or contract. There is no third option in the mathematics. Einstein wanted neither, so he held his own model still by hand, adding an extra term to the equations, the cosmological constant: a push built into space itself, set to balance exactly against the pull of everything gravity does. Lemaître took the hand away and let the model go. Out came a universe with a growing radius, and out with it came a prediction: the speed at which a galaxy recedes should be proportional to its distance. He then measured that proportion in the data and published the number, which is what separates his 1927 paper from the purely mathematical work of Alexander Friedmann five years before. Hubble measured it far better in 1929, and got the credit for close to ninety years, until in 2018 the International Astronomical Union voted to attach Lemaître’s name to the law as well.

(Q) "The recession velocities of extragalactic nebulae are a cosmical effect of the expansion of the universe." + Source: Lemaître, "Un Univers homogène de masse constante et de rayon croissant rendant compte de la vitesse radiale des nébuleuses extra-galactiques," Annales de la Société Scientifique de Bruxelles A47 (1927), the third of the numbered points in the conclusion, in Jean-Pierre Luminet’s English translation printed in General Relativity and Gravitation 45 (2013). Nebulae means galaxies here; the older word was still in use while the discovery that they lie outside our own galaxy was fresh. The sentence is the whole claim of the paper in one line: the redshifts are not local motions of particular objects but a property of the universe as a whole (T1).

(T2) Run the expansion backwards far enough and the world begins, and time begins with it. + Take the raisin loaf and run the film backwards. The raisins crowd in, the dough shrinks, and if you keep winding back there is a moment when everything that exists is in one place. Most physicists in 1931 found that thought unbearable and said so. Eddington, the kindest man in the profession and Lemaître’s own teacher, wrote that the notion of a beginning of the present order of nature was philosophically repugnant to him. Lemaître took the opposite view: if the equations say the world had a first moment, the job is to describe it, not to flinch. His picture was a single enormous atomic nucleus holding all the mass of the universe, which broke up the way a radioactive atom breaks up, in a cascade of smaller and smaller pieces. A quantum, in the physics of the day, is the smallest indivisible packet a quantity of energy comes in, the way money in a till comes in coins: you can have one or two of them, but there is no such thing as two thirds of one. Lemaître’s beginning was the case where the whole universe is a single packet. He called it the primeval atom. The details are wrong, as he expected them to be, and the shape of the claim is what survived: a hot, dense, definite beginning, with space and time starting at it rather than containing it. The name it goes by now was an insult. Fred Hoyle, who defended a universe with no beginning at all, spoke on the BBC on 28 March 1949 about the rival idea that all the matter of the universe had been made in one big bang, and the phrase stuck to the theory he was attacking. Lemaître never used it. His own image was gentler and sadder, and it stands on page 77 of the lectures Betty and Serge Korff translated as The Primeval Atom: "The evolution of the world can be compared to a display of fireworks that has just ended: some few red wisps, ashes and smoke. Standing on a well-chilled cinder, we see the slow fading of the suns, and we try to recall the vanished brilliance of the origin of the worlds."

(Q) "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." + Source: Lemaître, "The Beginning of the World from the Point of View of Quantum Theory," Nature 127 (9 May 1931), page 706. The whole letter is 457 words, written as a reply to Eddington. The sentence that follows draws the conclusion that unsettled his colleagues: if this is right, the beginning of the world happened a little before the beginning of space and time. He is not saying that something existed before time; he is saying that the categories themselves have no purchase at the first instant (T2).

(T3) A beginning found by physics is not the same thing as the creation confessed by faith. + A librarian can date the first page of a manuscript to within a decade. That is a real and hard-won result, and it settles nothing whatever about whether anyone wrote the book, or why. Lemaître thought the beginning of the world stood in something like that relation to the doctrine of creation, and he spent thirty years keeping the two apart. The doctrine is creatio ex nihilo, creation out of nothing: the teaching that God brought into being everything that is not himself, from no material lying ready to hand, so that there was no stuff he had to work with and no rule outside him he had to obey. "In the beginning, God created the heavens and the earth" (Genesis 1:1); "By faith we understand that the universe was created by the word of God, so that what is seen was not made out of things that are visible" (Hebrews 11:3). What Lemaître had found, on the other hand, was a first state of a physical system, reached by extrapolating a set of equations backwards past the point where anyone knew whether they still applied. Two reasons drove him. The first was ordinary intellectual honesty: the theory was young, contested, and might well be wrong. The second was pastoral. He had watched what happens when a doctrine is tied to a physics, and he did not intend to hand the next generation a church whose account of creation could be refuted by a better telescope. So he said, over and over and in as many rooms as would have him, that his cosmology proved nothing about God, and that this was a feature of it rather than a defect.

(Q) "The question if it was really a beginning or rather a creation, something started from nothing, is a philosophical question which cannot be settled by physical or astronomical considerations." + Source: Lemaître, from a paper written in the years between 1935 and 1946 and left unpublished in his lifetime, printed by Odon Godart and Michael Heller in Cosmology of Lemaître (1985), page 174. He said the same thing in public at the Solvay conference of 1958, in the report he gave there on the primeval atom hypothesis: as far as he could see, the theory remained entirely outside any metaphysical or religious question, and left the materialist free to deny any transcendent being (T3).

(T4) Scripture was given to teach the way of salvation, not the constitution of matter. + In February 1933 a reporter from the New York Times caught up with him in Pasadena, where he was lecturing, and asked the question everyone asked: how does a priest hold these two jobs at once. Lemaître’s answer was that he had been interested in truth about salvation exactly as much as in truth about the physical world, that there appeared to him to be two paths to truth, and that he had decided to follow both. Behind that lies the training Cardinal Mercier gave him. Thomas Aquinas had taught that faith and reason are two roads to a single truth, given by the same God, so that a genuine finding on one road cannot contradict a genuine finding on the other; where they seem to clash, either the science is bad or the reading of Scripture is. Lemaître applied the rule with a straight face in both directions. He would not let his physics be corrected by a devotional reading of Genesis, and he would not let his priesthood be embarrassed by his physics. He was blunt about what follows for the Bible. Neither Moses nor Paul, he said, had the slightest idea of relativity, and on questions that do not bear on salvation the writers of Scripture were as wise or as ignorant as their generation. Christians differ here, and the differences are real: the plainer reading of Psalm 19:1 and Romans 1:20 is that the created order is itself a witness that God intends to be heard, which is more than a bare separation of subjects allows for. But nobody who reads him carefully finds a man trimming his faith to fit his laboratory. He found the trimming unnecessary in both directions.

(Q) "Once you realize that the Bible does not purport to be a textbook of science, the old controversy between religion and science vanishes." + Source: Lemaître, interviewed by Duncan Aikman in "Lemaitre Follows Two Paths to Truth," New York Times, 19 February 1933. The interview was given in Pasadena during the American lecture tour on which Einstein publicly endorsed his cosmology. The sentence has been quoted ever since by Christians in the sciences, and it is worth noticing how much work the word purport is doing: he is making a claim about what kind of book Scripture is, not about how much of it is true (T4).

(Q) "I think that every one who believes in a supreme being supporting every being and every acting, believes also that God is essentially hidden and may be glad to see how present physics provides a veil hiding the creation." + Source: a paragraph Lemaître drafted for his 1931 Nature letter and then struck out before sending it. The crossed-out page survives in his papers at Louvain-la-Neuve. It is the most revealing thing he ever wrote about his own work, and he made sure the world would not read it. The thought behind it is the hidden God of Isaiah, the Deus absconditus of the older theologians: "Truly, you are a God who hides himself, O God of Israel, the Savior" (Isaiah 45:15). On that reading the wall he built between physics and theology (T3) is not a shrug. It is a piece of theology in its own right: a God who does not put himself at the end of a calculation is behaving exactly as Scripture says he does.

What Christian Thinkers Made of Him

(†) He is the awkward fact in the story of a war between science and religion. + For a century before Lemaître, educated opinion had been taught that science and Christianity were combatants. The story had two Victorian authors, John William Draper and Andrew Dickson White, who wrote the history of knowledge as a long campaign fought by science against the churches, and their books gave the story the shape it still has in popular retellings. Historians have been dismantling it ever since, patiently, and with the limited success that always attends corrections issued against a good story. Lemaître is difficult to fit into it. The man who gave the twentieth century its account of the origin of the universe said mass every morning, and he arrived at his cosmology by way of a seminary rather than in spite of it. He is not an exception the story can absorb, because he is not a scientist who happened to keep a private faith. His superiors backed the year at Cambridge, a cardinal told him to read relativity, and the Vatican made him head of its academy of sciences. Older Christian thought had a name for what he was doing. Francis Bacon, three centuries earlier, had spoken of two books, the book of God’s word and the book of God’s works, both to be studied and neither to be read as if it were the other. Lemaître worked out what that looks like when the book of works is a set of field equations.

(†) The beginning he found became a premise in an argument he would not make himself. + There is an old argument for God that runs in three lines: whatever begins to exist has a cause; the universe began to exist; therefore the universe has a cause. It is called the kalam cosmological argument, from kalam, the Arabic word for the medieval Muslim tradition of theological debate in which it was sharpened, and its most famous defender was al-Ghazali in the eleventh century. For most of modern history the weak line was the second one. An eternal universe was simply what educated people assumed, and a Christian who said the world had a beginning was appealing to Genesis, which was no help in an argument with somebody who did not accept Genesis. Lemaître’s cosmology, and then the observations that confirmed it, moved the pressure onto the first line instead. The philosopher William Lane Craig revived the argument in 1979 and made the expanding universe his main support for the premise that the world began, and a good deal of Christian apologetics has followed him. The honest footnotes are two. Lemaître would not have signed that use of his work, and said so repeatedly (T3). And the argument does not stand on his cosmology alone. Its defenders also argue, on grounds that have nothing to do with telescopes, that an actually infinite past could never have been crossed: if an endless run of days had to go by before today, today would still be waiting its turn and would never arrive. His discovery gave the second premise a kind of support it had never had before, which is a real thing to have given, and less than a proof.

(†) Where his own rule is questioned: he set the wall between the two paths higher than Scripture sets it. + The criticism that his own record earns is not that he was a bad priest or a bad physicist. It is that the rule he laid down, taken strictly as he stated it in 1958, proves too much. An argument proves too much when the same reasoning, applied evenly, knocks over things the person making it means to keep standing. Here is what it knocks over. If the beginning of the world can contribute nothing whatever to the question of whether the world was made, then it is very hard to say what could. Scripture does not treat the created order as evidentially silent. "The heavens declare the glory of God, and the sky above proclaims his handiwork" (Psalm 19:1). Paul writes that God’s "invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made" (Romans 1:20), and treats that perception as leaving people without excuse. Theologians call this general revelation: what God makes known of himself to everyone through the world and the conscience, as distinct from the special revelation given in Scripture. A wall high enough to keep cosmology out of theology keeps general revelation out too, or nearly. Two things should be said on the other side, and the second is the stronger. He was right that the theory might still be overturned. The steady-state rival was defended by serious people until the microwave background settled it in 1965, and a church that had staked a doctrine on the primeval atom in 1951 would have been holding a very exposed position for fourteen years. And his own crossed-out paragraph shows a subtler man than his public rule suggests. Physics providing a veil that hides the creation is not neutrality; it is a theological reading of what physics is for. The point at issue between him and his Christian critics is not whether the world testifies, but whether the testimony can ever be written down in an equation, and on that question thoughtful Christians still stand on both sides of him.