After Relativity: When Spacetime Becomes Reality: 4 The Big Bang Is Not a Beginning

Few scientific ideas have travelled so far, so fast, and with so much metaphysical luggage as the Big Bang.

Within physics, it is a technical term: a limit point in our best cosmological models, characterised by extreme temperature, density, and curvature. It marks the boundary beyond which those models no longer apply without further theoretical extension.

Outside physics, it is something else entirely.

It is heard as the beginning — the moment when the universe came into existence, when time itself started, when everything that is was set in motion. It becomes an origin story, a causal explanation, and, often enough, a kind of metaphysical full stop.

This post is about how that transformation happens — and why it is not licensed by the physics that made the Big Bang intelligible in the first place.

A Boundary, Not an Event

In cosmological models derived from general relativity, the Big Bang appears as a singularity: a point at which certain quantities diverge and the equations cease to be well-defined. This is not a discovery of a physical explosion or a literal moment of creation. It is a signal that the model has reached the edge of its domain of applicability.

Physicists know this. Singularities are not treated as objects or processes; they are treated as warnings.

Yet when the Big Bang is described as an event — something that happened at a time, at a place — the warning is quietly ignored. The boundary of explanation is redescribed as the deepest explanation of all.

The slide is subtle but consequential.

From Model to Myth

The temptation to treat the Big Bang as a beginning is not just linguistic. It is narrative.

Human explanation is deeply attuned to stories with origins. We understand things by asking how they started, what caused them, and how everything that followed flowed from that first moment. When cosmology offers something that looks like an origin, it is almost irresistible to press it into that familiar shape.

But cosmology does not, in fact, provide a privileged first moment.

Cosmic time — the parameter with respect to which the universe is said to be a certain age — is defined relative to a particular class of models and observers. It is not time as such. To say that the universe is approximately 13.8 billion years old is to make a statement internal to a modelling framework, not to report a fact from outside all frameworks.

Once again, a disciplined construal is mistaken for an ontological vantage point.

Explanation Without Closure

What does the Big Bang explain?

It explains why, given the symmetries and constraints of our cosmological models, the universe exhibits the large-scale features we observe today. It explains patterns in the cosmic microwave background, the distribution of galaxies, and the relation between distance and redshift.

What it does not explain is why spacetime exists at all, why these laws hold rather than others, or why there is a universe rather than nothing.

Treating the Big Bang as an answer to those questions is not an extension of cosmology. It is a shift into metaphysics — one that is usually unacknowledged.

The problem is not that such questions are illegitimate. The problem is that the authority of physics is quietly borrowed to settle them.

The Hunger for a First Cause

The Big Bang is often pressed into service as a modern substitute for older metaphysical beginnings. Where once there was creation, now there is inflation; where once there was divine fiat, now there is a quantum fluctuation.

These substitutions may feel more sophisticated, but structurally they do the same work. They promise closure. They suggest that, at last, we have reached the point beyond which no further question can meaningfully be asked.

Relativity and cosmology themselves resist this promise.

They replace absolute beginnings with boundaries of applicability, absolute times with relational parameters, and ultimate explanations with tightly constrained accounts of dependence within a theory.

Owning the Boundary

The achievement of modern cosmology is not that it has discovered the moment when everything began. It is that it has shown how far disciplined modelling can take us — and where it must stop.

To own the Big Bang as a boundary rather than a beginning is not to diminish it. It is to respect it.

The temptation to turn that boundary into an origin story is understandable. It is also optional.

In the next post, we will examine what happens when this optional step hardens into authority — when cosmological narratives begin to speak not just about models, but about reality as a whole, and when restraint gives way to metaphysical confidence.