In discussions about the beginning of the universe, a recurring claim seeks to soften or even negate the significance of the Big Bang as a true temporal boundary. One popular version of this view is that, due to the geometric behavior of space-time near the Big Bang, time "slows down" infinitely as we approach t = 0, rendering the beginning simultaneously eternal. While this may sound sophisticated, it is built on several category mistakes and conceptual confusions.
Before the 20th century, most philosophical and scientific models of the cosmos assumed it was eternal. Even through the early decades of the 1900s, many prominent scientists—including Einstein himself—resisted the idea of a beginning. The shift to a universe with a finite past came as a surprise, driven not by preference but by the data.
Virtually every line of modern evidence—cosmic‑microwave background (Penzias & Wilson, 1965), galactic redshift (Hubble, 1929), primordial‑abundance fits—points to a universe with a finite age. Stephen Hawking summarizes the consensus succinctly:
“Almost everyone now believes that the universe, and time itself, had a beginning at the Big Bang.”
—A Brief History of Time (1988)
FLRW space‑times extrapolated backward lead to a scale‑factor of zero at t = 0, implying a temporal boundary.
The Asymptote Objection in Brief
A popular rebuttal tries to dissolve that boundary by appealing to the geometry of space‑time diagrams. Because proper time shrinks towards zero while coordinate intervals can be drawn ever wider, the Big Bang is portrayed as an asymptote: the closer one moves to t = 0, the slower clocks appear to tick, so that the final “second” of pre‑history stretches without limit. On that reading, the universe is said to possess a beginning and to be “eternally old” in the same breath.
A central confusion often stems from conflating coordinate time with proper time. In General Relativity, coordinate time can behave in unintuitive ways depending on the chosen metric. It is not directly measurable; rather, it provides a framework for describing events.
Proper time, on the other hand, is the physical time measured by a clock along a particular worldline. This is what cosmologists refer to when they say the universe is approximately 13.8 billion years old.
It is entirely possible—indeed common—for coordinate time to diverge or display asymptotic behavior near singularities without this implying that the proper time is infinite. Saying "one second equals infinity when t = 0" is a nonsensical mixing of categories. An infinite value in a coordinate representation is not equivalent to the physical passage of an infinite number of seconds.
Why the Asymptote Does Not Re‑Introduce an Infinite Past
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Finite Proper Age
Even in coordinates where intervals blow up, the integrated proper time along any past‑directed world‑line is finite—about 13.8 Gyr. As Alexander Vilenkin notes:“The conclusion is unavoidable: the universe had a beginning.”
—Vilenkin, Many Worlds in One (2006) -
Geodesic Incompleteness
Hawking‑Penrose singularity theorems establish that, under reasonable energy conditions, past‑directed geodesics cannot be extended indefinitely; they terminate at a singular boundary. Roger Penrose remarks:“The space‑time cannot be continued to the past of the singularity because there is simply nothing there to continue into.”
—Penrose, The Road to Reality (2004) -
Distinction Between Limits and Real Durations
A mathematical limit (e.g., 1/x → ∞ as x → 0) does not entail an actually infinite series of physical events. Saying that coordinate time blows up near t = 0 is not equivalent to saying the universe truly experienced an infinite succession of moments. -
Historical Turnabout
Early‑20th‑century steady‑state advocates (e.g., Bondi, Gold, Hoyle) indeed championed an eternal cosmos. That model was abandoned precisely because new data contradicted it. Sean Carroll summarizes:“The weight of the evidence points to a universe that is finite in age; there’s just no way to stretch that into an infinite past without contradicting observation.”
—Carroll, From Eternity to Here (2010)
Time‑Theory Clarifications
Invoking Minkowski diagrams or McTaggart’s B‑Series (tenseless theory) does not re‑establish an actual infinite past. Even in a “block universe,” the temporal manifold has a lowest boundary value—t = 0—beyond which no events are ordered, whether or not one prefers an A‑theory (tensed) or B‑theory (tenseless) ontology of time.
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Minkowski Space: Extends indefinitely only in special‑relativistic models without metric expansion; general‑relativistic solutions with positive matter density break this symmetry at t = 0.
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Hawking–Penrose Singularity Theorems: Under reasonable energy conditions, geodesics cannot be extended indefinitely into the past; they terminate in a singular boundary of finite proper length.
The Role of Time Theories: A vs. B
If one is trying to rescue some form of cosmic eternity, it is crucial to specify what theory of time is being used. Philosophers distinguish between two major views:
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A-theory (Presentism / Tensed Time): Only the present is real. The past and future do not exist.
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B-theory (Eternalism / Block Universe): All points in time (past, present, future) are equally real.
If someone is claiming that time is “eternal” near the Big Bang, they might be implicitly adopting a B-theory of time, where all events—past and future—coexist timelessly within the spacetime block. But this theory still admits a lowest boundary in the block. Even in B-theory, there is a first temporal coordinate; the block has a bottom.
Moreover, such a metaphysical claim cannot be casually imported into a scientific discussion without qualification. The fact that General Relativity allows for a four-dimensional geometric model of the universe does not settle the ontological debate about the nature of time. This debate is still ongoing in the philosophy of physics.
Metaphysical and Philosophical Implications
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No Return to Classical Eternity
The asymptote, properly understood, safeguards the beginning rather than erasing it. It signals a limit to classical space‑time, after which quantum‑gravity questions may arise—but it emphatically does not reinstate an actual infinite past. -
Time‑Theory Debates Remain Intact
Whether one adopts an A‑theory (tensed) or B‑theory (tenseless) ontology, both sides concede a lowest temporal coordinate. A block universe still has a lower face.
The proposition that the universe is “simultaneously finite and infinitely old” collapses under empirical data and careful conceptual analysis. Modern cosmology, supported by singularity theorems and echoed by leading physicists, affirms a universe of finite age. The asymptotic depiction is a coordinate artifact, not a physical loophole that restores a boundless temporal past.