When Christians think about creation, we often look to Genesis 1, “In the beginning,
God created the Heavens and the Earth.” Today, that might just as easily bring to
mind a mental image of a massive explosion from a science documentary on the Big Bang,
the unfathomable expansion event that scientists have been able to date to 13.77 billion years ago,
plus or minus 40 million years. That is an unimaginably large amount of time,
but it is not infinite. There was some moment, a long time ago, when the Big Bang happened.
An obvious question to ask is “why”? Why then? Why at all? If the Big Bang marks the beginning of the
universe, don’t we need something outside the universe to explain it, to cause it?
Is the Big Bang actually the beginning? Does the fact of the Big Bang prove the existence of God?
The question of the beginning of the universe dates back as far as our earliest written records.
Many of these earliest discussions are religious in nature, presenting
a story or account of the origin of the world. Philosophers discussed the question as well,
arguing from philosophical principles that the Universe either began to be or had always existed.
For instance, Plato argued that the world had to have a beginning, while Aristotle tries to
demonstrate that it had always existed from the perfect motion of the heavens.
From the witness of the scriptures, Christians have always known, by faith, that the world had a
beginning, but this did not stop medieval thinkers from arguing over the philosophical question
of whether we could know that the world had a beginning in time, simply by human reason.
Many people are surprised to hear that St. Thomas Aquinas, while affirming that we know the world
had a beginning by faith, argued strenuously that we could not demonstrate that the world
had a beginning by reason alone. He defended the idea that the world could have existed for an
infinite amount of time in the past, but would still need a Creator to explain its existence.
I’m not going to go into the details of that argument here, but suffice it to say that not
everyone agreed with him. Many thinkers thought that proving the world had a beginning was
possible on natural principles, and that doing so immediately provided a proof for God’s existence.
One such argument is known today as the “Kalam Cosmological Argument,” which goes as follows:
Everything that has a beginning needs a cause. The universe had a beginning.
Therefore the universe had a cause, and the only cause that could fit the effect is God.
While Aquinas was convinced that you could prove that God existed by natural reason,
he didn’t think this proof worked.
In many ways, the question of the beginning and origin of the universe remained
simply a matter of religious faith and philosophical debate throughout the rise
of modern science. While Astronomy changed our understanding of the solar system and the stars,
their origins and history still remained opaque and inaccessible. Most scientists
tended to think that while there were local motions of stars and galaxies,
the overall structure of the universe was basically static and had always been that way. Any
talk about the beginning of the universe or its age was philosophical and religious speculation.
All that changed in the early 20th century with the theory of the Big Bang,
proposed by Fr. George Lemaître. That concept is based on Einstein's General
Theory of Relativity and supported by the observational discovery that
almost all of the stars and galaxies we see in the universe are moving away from us.
Today, scientists can do more than muse philosophically about the age of the universe — we
can try to measure it. But does the fact that we can put a date on the Big Bang (plus or
minus 40 million years) mean that we know that the universe had to have a beginning? Not necessarily.
The first thing to clarify is that Big Bang Cosmology is not primarily
meant to be an explanation of the fundamental origin of the universe.
Instead, it offers an explanation for why the universe looks the way it does
today. The basic model for the Big Bang does not describe the transition from nothing to something,
but the change from an unimaginably dense and hot initial state to the fairly cool, diffuse universe
of galaxies, stars, and planets that we see today, with all their complex physics and chemistry.
You might think we could just rewind the physics of general relativity a bit to
see what the initial “hot dense” state was doing a second before the Big Bang.
But the model says the density becomes infinite at the Big Bang. In other words, the model itself
breaks down at that point, in what mathematicians and physicists refer to as a “singularity”.
As we cram more and more matter into a smaller and smaller space, we come dangerously close
to “dividing by zero” and our equations start spitting out infinite and uninterpretable results.
So that’s it, then right? At that point, physics breaks, so it must be the beginning.…
Well, not so fast.
These sorts of infinities and singularities have shown up in physical models before, and they
did not point to a fundamental breakdown of the natural order.
Instead, they point to a gap in our understanding of that order. The absurdly dense and hot state
of the universe at those earliest moments means that we cannot just rely on general relativity,
but must invoke quantum mechanics as well. That introduces a whole new problem because
general relativity and quantum mechanics — our two best theories of physics — are built on different
mathematical and physical foundations and do not obviously play nice together.
That said,
physicists have been working on unifying general relativity and quantum mechanics for decades and
some reasonable progress has been made. Sketches of various possible theories of quantum gravity
help to shed light on what the “singularity” of the Big Bang might have looked like.
Physicists have proposed a variety of possible physical models for what
might have come before the Big Bang even, often seeing the singularity that “began”
everything as one of several explosive events in the history of the broader universe, often either
one in a cyclic repeating sequence of Big Bangs over time, or as one of several Big Bangs in a
complicated branching pattern sometimes referred to as the “multiverse”. While these ideas might
sound strange and fantastic, they are rooted in reasonable and defensible physical intuitions, and
we should remember that the Big Bang itself seemed fanciful to many when it was first proposed.
Physicists continue to debate about the reasonableness of various proposed
theories of what came before the Big Bang, as well as whether other physical principles
like the Second Law of thermodynamics or other cosmological principles, might still prevent such
extended theories of the cosmos from stretching infinitely far back in time.
These theoretical disagreements are usually only settled in science through new experimental and
observational data. But, in this case, that presents a problem. The sorts of
effects that would distinguish between different theories of quantum gravity
are well beyond any observation or experiment we could hope to make in the near future and,
worse, most of the theories for what came before the Big Bang are, in principle,
untestable because of the extreme conditions of the singularity 13.77 billion years ago.
While physics and astronomy have not yet and, arguably, never will,
prove definitively that the universe had a beginning, much of the data and
trends of contemporary science over the last century or so strongly suggest that it did.
While this may not be the key to an unassailable proof of God’s existence that some would like it
to be, it is nevertheless remarkable how much of a change in perspective modern cosmology is relative
to the classical physics that came before. Earlier views of the universe rooted in classical physics
presumed that it was infinitely old and basically static. This made any act of creation
arbitrary and discontinuous. This made any act of creation seemingly arbitrary and discontinuous.
Modern cosmology, on the other hand, forces us to deal with a dynamic and historical cosmos
which makes the possibility of a beginning much more scientifically interesting and palatable.
We may never know, for certain, on scientific grounds alone that the universe had a beginning,
but the theory of the Big Bang gives us an image and an icon for the truth that we know
by faith: “In the beginning, God created the heavens and the earth”.
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