Introducing the Hubble–Lemaître Law

On October 29, 2018, the International Astronomical Union announced its recommendation that the erstwhile “Hubble Law” be referred to as the “Hubble–Lemaître Law.” The law relates the distances of galaxies to their motion away from Earth. Among other lines of evidence, extrapolating from the law suggests that the entire material cosmos emerged from a single point in the ancient past which expanded into the cosmos we know today, a theory now known as the “Big Bang.”

American astronomer Edwin Hubble, who made measurements of the redshifts of distant galaxies – which are related to their distance and speed away from Earth – has long had his name associated with the discovery. But in fact it was Belgian priest Georges Lemaître who first derived the laws related to the expanding cosmos, and who proposed the universe’s origin from an ancient, singular point; his contribution has been gaining more recognition over recent years, including such gestures as the IAU’s most recent recommendation.

Because modern science and faith are so often alleged to be opposed, it’s good to see a priest, especially a modern priest, recognized for any important contribution to science. But more than merely illustrating that Catholics can find a place in the workings of science, there is something especially and ironically significant in the association of a Catholic clergyman with the theory of the Big Bang.

Big Bang cosmology provides the overarching framework for our contemporary understanding of the entire cosmos as an evolving, historical thing. If it can be said that classical cosmology, with its ordered spheres and geometric neatness, resonated with the Catholic mind in its emphasis on hierarchical order, then the resonance of modern cosmology is with the Catholic instinct for story.

Fr. Lemaître with Albert Einstein, 1927

In modern science, as in the Catholic view, we find not a cosmos of eternal, changeless homogeneity (as in the “Steady State” theory that was the rival to the Big Bang in early 20thcentury cosmology); nor do we find a confused chaos, with complicated beings arising seemingly from nowhere, as in pagan cosmogonies. Rather, modern science presents a picture in which the rich complexity of the modern universe arises from a causal singularity, from which basic physical forces arise and interact to blossom into the cosmos we know today.

Lemaître himself referred to this ancient singularity as a “Cosmic Egg.” To borrow an analogy used originally for a higher purpose, we might also invoke the image of a tiny seed, which grows to produce great branches, in which the birds of the air make their nests.

On a material level, current science affirms that from the great cosmic seed came the web of galaxies, stars, and planets. In the formation and explosive endings of the life-cycles of uncountable stars, the universe became enriched with the elements that make all the stuff of our world around us possible – including life. Carl Sagan, the religiously skeptical but charismatic popularizer of modern science, liked to say that “we are stardust.” What Sagan, for all his poetic imagery, never quite imagined, however, is that one day, on a small rocky world orbiting one of these points of light, the Author of the whole cosmic story took on that stardust himself and entered bodily into his Creation.

Objections to the Big Bang today often come from a religious direction: how can this account be squared with the biblical presentation of Creation? But originally suspicion of the Big Bang came from the opposite direction: it smacked too much of religion. The Church proclaimed a Creation ex nihilo – a moment before which no moments and nothing material were – and now science seemed to point to the same thing.

In 1978, Arno Penzias and Robert Wilson received the Nobel Prize in Physics for their observation of the “cosmic microwave background,” the first major evidence of the Big Bang event. Penzias would later write of the Big Bang and the origin of the universe, “The best data we have are exactly what I would have predicted, had I nothing to go on but the five books of Moses, the Psalms, the Bible as a whole.”

But let us be careful: it was Lemaître himself who famously warned Pope Pius XII away from too closely identifying the Big Bang with the actual act of Creation. To find Creation is, strictly speaking, beyond the purview of science. Even Thomas Aquinas held that reason alone could not discern whether the universe had a beginning; only revelation could say so. So too science, investigating material causes, can only follow such causes as far as they lead; beyond them, it cannot see.

The Big Bang may have been the beginning, or it may not. Nevertheless, scientifically speaking, the Big Bang represents the singular historical event from which all the material world we know emerges, the one and only point through which all physical histories pass. It is, so far as modern science can say, the beginning of the known cosmos. And there, at its discovery, we find Fr. Lemaître, a priest contributing to science not merely by one important scientific insight among others, but by outlining the most fundamental theory of the history of the physical cosmos.

Religion had always had its own cosmology, its history of Creation. But we find, in an interesting twist, that when science used its own legitimate tools to discover its comprehensive story of the world, that the story was first discovered not by a reasonable atheist freed from the shackles of “superstition,” but by a priest who found no conflict between his ancient faith and the revolutionary findings of the newest science.

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Michael Baruzzini is a freelance science writer and editor who writes for Catholic and science publications, including Crisis, First Things, Touchstone, Sky & Telescope, The American Spectator, and elsewhere. He is also the creator of, which offers online science curriculum resources for Catholic students.