How the Universe Began — And What It Means

The Most Important Discovery in the History of Science

For most of human history, the dominant assumption among philosophers and scientists was that the universe was eternal — that matter and space had always existed, with no beginning and no end. The ancient Greeks taught it. Enlightenment thinkers assumed it. Even Albert Einstein, when his own equations of General Relativity predicted a universe that was either expanding or contracting, introduced a "cosmological constant" — an artificial mathematical patch — specifically to force his model back to a static, eternal cosmos. He later called this the greatest blunder of his life.

The reason scientists resisted the idea of a beginning is not hard to understand. A universe with a beginning immediately raises the question: what caused it? And a cause that is itself uncaused, that exists outside of space and time, that brought everything into existence from nothing — that sounds uncomfortably like God. As Sir Arthur Eddington, one of the greatest astrophysicists of the twentieth century, admitted: "Philosophically, the notion of a beginning of the present order of nature is repugnant to me."

But the evidence came anyway. Over the course of the twentieth century, three independent lines of scientific discovery converged on a single, inescapable conclusion: the universe had a beginning. Not a rearrangement of pre-existing matter. Not a transition from one phase to another. An absolute beginning — the origin of space, time, matter, and energy themselves — from nothing.

Today the Big Bang is not a hypothesis or a theory in the colloquial sense of "a guess." It is the foundation of modern cosmology, confirmed by multiple independent lines of evidence and accepted by virtually every working cosmologist on earth. The universe had a beginning. That is now scientific fact.

The Catholic Priest Who Discovered the Big Bang

Here is a fact that popular culture has almost entirely suppressed: the Big Bang theory was first proposed not by an atheist, not by a secular scientist, but by a Catholic priest.

Fr. Georges Lemaître was a Belgian physicist and Roman Catholic priest who earned a doctorate in physics from MIT and another from the Catholic University of Leuven. In 1927 — two years before Hubble's famous observations — Lemaître published a paper proposing that the universe was expanding, deriving this conclusion directly from Einstein's equations of General Relativity. He went further still: in 1931, he proposed what he called the "hypothesis of the primeval atom" — the idea that the entire universe had exploded from a single, unimaginably dense point at a finite moment in the past. The universe, Lemaître argued, had a beginning.

Einstein initially rejected the proposal. When Lemaître presented his expanding-universe solution to Einstein at a 1927 conference, Einstein reportedly told him: "Your calculations are correct, but your physics is abominable." It was only after Hubble's 1929 observational confirmation that Einstein came around — and when he did, his praise was unqualified. At a 1933 seminar in California where Lemaître presented his theory, Einstein stood and applauded, declaring it "the most beautiful and satisfying explanation I have heard."

It is worth pausing on the irony. For decades, atheists had argued that a universe without a beginning was evidence against God. A universe that had always existed needed no Creator. When the evidence began pointing toward a cosmic beginning, it was atheist and materialist scientists who resisted the conclusion — because it pointed toward exactly the God they wanted to avoid. And the man who pressed the case most forcefully, who looked at Einstein's equations and saw what they actually implied, was a man who said Mass every morning and prayed the Liturgy of the Hours every day.

Lemaître himself was careful to keep his science and his theology distinct — not because he thought them opposed, but because he wanted the scientific case to stand on its own merits. He did not need to invoke Genesis to do physics. He simply followed the mathematics wherever it led. And where it led was to a beginning.

The Kalam Cosmological Argument

The scientific confirmation that the universe had a beginning does not, by itself, prove the existence of God. It proves something far more modest — and far more consequential: the universe requires a cause. The philosophical work of moving from "the universe has a cause" to "that cause is God" is done by one of the most powerful arguments in the history of philosophy, an argument that has been sharpened and formalized for modern audiences by philosopher and theologian William Lane Craig.

The Kalam Cosmological Argument takes its name from the medieval Islamic philosophical tradition, though its roots extend to Aristotle and were developed at length by Catholic scholastic thinkers including St. Thomas Aquinas. In its modern form, the argument is elegant in its simplicity:

Both premises are well-supported. Premise 1 is a fundamental principle of rational thought — we have never once observed anything begin to exist without a cause. Quantum fluctuations, sometimes cited as counterexamples, do not occur in a vacuum of true nothingness but within a quantum field — itself a physical structure that requires explanation. Premise 2, as we have seen, is now confirmed by multiple independent lines of cosmological evidence.

The conclusion follows necessarily: the universe has a cause. But what kind of cause? Here the argument becomes genuinely illuminating. The cause of the universe must have the following properties:

• Timeless — because the cause created time itself; it cannot exist within time
• Spaceless — because the cause created space; it cannot exist within space
• Immaterial — because the cause created matter; it cannot itself be composed of matter
• Incredibly powerful — because the cause brought the entire universe into existence from nothing
• Personal — because the only way for a timeless, changeless cause to give rise to a temporal effect is by a free act of will. A personal agent can choose to act; an impersonal mechanism operating according to fixed laws cannot "decide" to begin. The universe's beginning implies a free choice — and free choice implies a person.

Timeless. Spaceless. Immaterial. Infinitely powerful. Personal. This is a precise description of the God proclaimed by Catholic Christianity — and by Judaism and Islam — for thousands of years. The Kalam does not prove every article of faith. But it demonstrates, with the rigor of philosophical argument grounded in modern science, that the universe had a personal Creator. The rest is a question of which religion has correctly identified who that Creator is.

The Borde-Guth-Vilenkin Theorem: Even Eternal Inflation Had a Beginning

One of the most popular scientific strategies for avoiding the conclusion of a cosmic beginning has been the theory of eternal inflation. The idea is that our observable universe is just one bubble in an endlessly expanding cosmic foam — that inflation has been going on forever in the past, with new universes constantly budding off from the inflating background. If inflation is truly past-eternal, the argument goes, then there was never a "beginning" in any meaningful sense.

This hope was definitively extinguished in 2003 by a mathematical theorem proved by three of the most eminent cosmologists in the world: Arvind Borde, Alan Guth (the originator of inflationary cosmology), and Alexander Vilenkin. Their theorem, published in the journal Physical Review Letters, demonstrated with mathematical rigor that any universe that has been expanding — on average — throughout its history must have a beginning. Even if inflation is eternal into the future, it cannot be eternal into the past. The past boundary exists. The beginning is real.

The Borde-Guth-Vilenkin (BGV) theorem applies not only to our universe but to any inflationary multiverse proposed to explain it. Every model that invokes eternal inflation to escape the need for a beginning is itself subject to the theorem: if the model involves average expansion, it requires a past boundary. There is no escape within the framework of known physics.

Alexander Vilenkin, a cosmologist at Tufts University and one of the world's leading experts on the origin of the universe, is not a theist. He has not converted to Christianity. He is a secular scientist following the evidence. And yet this is what he has concluded:

Vilenkin has also written, in his book Many Worlds in One (2006): "It is said that an argument is what convinces reasonable men and a proof is what it takes to convince even an unreasonable man. With the proof now in place, cosmologists can no longer hide behind the possibility of a past-eternal universe. There is no escape: they have to face the problem of a cosmic beginning."

The problem of a cosmic beginning — faced squarely and honestly — is the problem of a Creator.

Stephen Hawking's Objection: The "No Boundary" Proposal

No discussion of the universe's beginning would be complete without engaging the most famous scientific attempt to eliminate the need for a Creator: Stephen Hawking's "no boundary" proposal, developed with physicist James Hartle in the 1980s and popularized in Hawking's bestselling book A Brief History of Time (1988).

Hawking proposed a model of the early universe in which time, near the Big Bang singularity, becomes mathematically indistinguishable from a spatial dimension. In this model, using the mathematical technique of "imaginary time" (multiplying the time coordinate by the square root of negative one), the universe has no sharp boundary at the beginning — it is a smooth, closed surface, like the surface of a sphere. Just as a sphere has no edges, Hawking's model has no initial singularity. His conclusion: "The universe would be completely self-contained and not affected by anything outside itself. It would simply be. What place, then, for a creator?"

The objection sounds powerful. It is, on examination, much less so. Several decisive responses apply:

Philosopher of physics John Lennox, in his book God and Stephen Hawking, put the central error precisely: "Nonsense remains nonsense, even when talked by world-famous scientists." The logical error in Hawking's proposal is the assumption that a mathematical description of a process is an explanation of why that process exists. It is not. Physics describes how the universe behaves. It cannot, by its own methods, explain why there is a universe to behave at all.

The "Eternal Universe" Alternatives — and Why They Fail

Over the past century, various scientific and philosophical alternatives to a universe with a beginning have been proposed. Each has been tested against the evidence — and each has failed.

The Steady State Theory

Proposed in 1948 by astronomer Fred Hoyle (who himself coined the derisive term "Big Bang"), the Steady State theory held that the universe had no beginning — that it had always existed and maintained a constant average density through the continuous creation of new matter as the universe expanded. Hoyle preferred this model explicitly because a universe with a beginning pointed toward a Creator he did not want to acknowledge.

The Steady State theory was decisively refuted by the discovery of the Cosmic Microwave Background in 1965. The CMB is the afterglow of a hot, dense early universe — exactly what the Big Bang predicts and exactly what Steady State cannot explain. The theory is now of historical interest only. Fred Hoyle, to his credit, was honest enough to acknowledge the CMB as the decisive evidence against his preferred model.

Cyclic and Oscillating Models

If the universe began with a Big Bang, might it eventually collapse in a "Big Crunch," then bounce back into a new expansion — cycling forever through an infinite series of expansions and contractions, with no absolute beginning? This is the appeal of cyclic or oscillating universe models, which have been proposed in various forms by physicists including Paul Steinhardt and Neil Turok.

The problem is thermodynamic and cosmological. Each cycle of expansion and contraction, if such cycles occurred, would increase the entropy of the universe — the disorder would accumulate from cycle to cycle. A universe that has been cycling forever would have reached maximum entropy long ago. We have not. This suggests the cycling, if it occurred at all, had a finite number of past cycles — which means a beginning. More fundamentally, the BGV theorem applies directly: any cyclic model that involves average expansion (as all realistic models must) requires a past boundary. Eternal cycling does not escape the beginning.

The Multiverse

The multiverse — the proposal that our universe is one of an enormous or infinite number of universes, each with different physical constants — is perhaps the most fashionable contemporary alternative to divine creation. It is important to be precise about what the multiverse can and cannot accomplish.

The multiverse cannot eliminate the need for a beginning. The BGV theorem applies to any multiverse model that involves average expansion. Even an eternal multiverse requires a past boundary. More fundamentally, the multiverse cannot eliminate the need for a cause: whatever mechanism generates the multiverse — whether it is Alan Guth's eternal inflation, Lee Smolin's cosmological natural selection, or any other proposed mechanism — itself requires a cause and a beginning. Pushing the question back one level does not answer it.

The multiverse also has a profound scientific problem: it is, almost by definition, untestable. We have no access to other universes and no prospect of gaining any. A theory that makes no testable predictions is not science in any meaningful sense — it is metaphysics. And as metaphysics, it is far less parsimonious and less well-supported than the theistic hypothesis it is proposed to replace.

The Theologians Had Been Sitting There for Centuries

Robert Jastrow was not a man given to religious sentiment. He was an astrophysicist, a NASA scientist, the founder and director of NASA's Goddard Institute for Space Studies, and by his own description an agnostic — a man who believed science was the most reliable instrument humanity possessed for understanding reality. He spent his career following the evidence of cosmology with the dispassion of a rigorous scientist.

And then he wrote this:

Jastrow was not converting. He was conceding. He was acknowledging, with the honest intellectual humility of a genuine scientist, that the conclusion science had labored for centuries to reach — that the universe had a beginning — was a conclusion that theologians had proclaimed from the very first words of sacred Scripture. The scientist climbed the mountain of evidence. At the top, he found the believer waiting.

In the Beginning: What Science and Scripture Agree On

The opening words of the Bible are among the most famous in all of human literature: "In the beginning God created the heavens and the earth" (Genesis 1:1). For centuries, skeptics pointed to this verse as evidence that Scripture was pre-scientific mythology — a primitive cosmology that modern science had superseded. The universe was eternal, they said. It had always existed. There was no "beginning," and therefore no need for a Creator.

Modern cosmology has vindicated Genesis. Not in the naïve sense that every detail of the Genesis narrative maps onto astrophysics — the Church has never required a literal six-day creationism, and the Fathers of the Church debated the nature of the Genesis account from the earliest centuries. But in the most fundamental sense: the universe is not eternal. It had a beginning. It is contingent — it did not have to exist, and it came into existence at a definite moment in the finite past.

A contingent universe — a universe that began to exist — requires a cause. That cause must be outside of space, time, and matter, since it brought space, time, and matter into existence. It must be unimaginably powerful, since it created everything from nothing. And as the Kalam argument demonstrates, it must be personal — a free agent who chose to create.

This is not a description that fits any impersonal force or natural mechanism. It is a description of God. The God of Genesis. The God of the Catholic faith. The God who, outside of time and space and matter, spoke — and the universe came into being.

The theologians had the answer first. Science, after centuries of effort, arrived at the same summit. The view from the top is the same from both sides of the mountain: In the beginning, God.

Continue: The Fine-Tuning of the Universe →