Rosa Rubicondior: How Science Works - And Why Religion Fails

Dipartimento di Fisica e Astronomia: Unipd develops new model to understand the origins of the Universe

Credit: NASA/WMAP Science Team

Unlike religion, science does not claim to know exactly how the universe began. What we do know, however, is that at the moment when time (t) = 0, both time and space came into existence. This means that in the conventional sense of time, there was no ‘before’, because ‘before’ presupposes the existence of time. Questions about what existed before the Big Bang are therefore meaningless, even though our intuition insists that there must have been something.

Religion, by contrast, has claimed to know how the universe began ever since creation myths were first invented in the Bronze Age or earlier — and those claims have remained unchanged. The problem is that they substitute genuine explanations with “God did it!” — a statement that explains nothing, is untestable, unfalsifiable, and devoid of any predictive power. It provides comfort only to those who are content not to know the details and unconcerned with truth.

This highlights another crucial difference between science and religion as tools for understanding reality: science continuously updates its knowledge and understanding. It never settles on convenient certainties, no matter how emotionally satisfying they may be, nor does it declare the search for answers to be over.

For many years, the consensus in cosmology has been that the initial few microseconds of the Big Bang involved a period of hyperinflation — a rapid expansion driven by a massive increase in space. Now, however, a team of researchers from Spain and Italy has revived a model first proposed by Albert Einstein and the Dutch mathematician Willem de Sitter, known as De Sitter space. Using this framework, they argue that gravity alone can explain the first few microseconds of space-time. Their new theory has been published, open access, in Physical Review Research.

One key advantage of this explanation over the inflationary model is its relative simplicity. It also, unlike the 'inflation' model, doesn't need elements that have never been observed, but relies solely on gravity and quantum mechanics. Applying Occam's razor, the simpler explanation with fewer elements or 'entities', is more likely to be correct.

The First Few Seconds of the Big Bang. The Big Bang marks the beginning of space and time about 13.8 billion years ago. It was not an explosion into space but an expansion of space itself from an extremely hot, dense state.

t = 0 (The Origin)
This is the moment time and space came into existence. The universe had zero age at this point. Conditions were so extreme that our current laws of physics cannot describe them. The concept of “before” has no meaning because time itself did not exist.
t ≈ 10⁻⁴³ s (Planck Time)
This is the earliest moment after the Big Bang at which our physical theories can meaningfully describe the universe. Below this, space, time, and energy are not well-defined, and known laws break down. A complete theory of quantum gravity may one day reveal what happened in this earliest phase.
t < 10⁻³⁶ s (Inflationary Epoch)
The universe underwent exponential expansion, growing far faster than the speed of light (which does not violate relativity because it is space itself expanding). This smoothed out irregularities and set the structure of the cosmos.
t ≈ 10⁻³² to 10⁻¹² s (Quark Epoch)
As temperatures dropped slightly, the fundamental forces began to separate. Quarks, gluons, and leptons filled the universe in a hot, dense plasma.
t ≈ 10⁻⁶ s (Hadron Epoch)
Quarks combined to form protons and neutrons as the universe cooled to about a trillion degrees Kelvin.
t ≈ 1 s (Lepton Epoch)
Neutrinos decoupled and began travelling freely through space. Electrons and positrons largely annihilated each other, leaving a slight excess of electrons.
t ≈ 3 min (Nucleosynthesis)
Protons and neutrons fused to form the first atomic nuclei — mostly hydrogen and helium, with traces of lithium.
t ≈ 380,000 years (Recombination)
Electrons combined with nuclei to form neutral atoms, allowing light to travel freely. This produced the cosmic microwave background radiation, still detectable today.

This very brief period — from less than a trillionth of a second to just a few minutes — set the stage for everything that followed: the formation of stars, galaxies, planets, and eventually, life.

Further details of the research and its background are explained in this news release from Dipartimento di Fisica e Astronomia Galileo Galilei, Università degli Studi di Padova.

Unipd develops new model to understand the origins of the Universe
A team of scientists, including Daniele Bertacca and Sabino Matarrese from the Department of Physics and Astronomy "G. Galilei" at the University of Padua, in collaboration with Raúl Jiménez from the University of Barcelona and Angelo Ricciardone from the University of Pisa, has published an article in Physical Review Research Letters titled "Inflation without an inflaton", proposing a new theory about the origin of our Universe.
This new theoretical framework represents a radical shift in how we understand the very first moments of the Universe's existence—without relying on some of the speculative elements traditionally assumed in the standard theory of inflation. For decades, cosmologists have worked within the inflationary paradigm, a model suggesting that the Universe underwent an incredibly rapid expansion, setting the stage for everything we observe today. This paradigm explains why the Universe appears so homogeneous and isotropic, while also accounting for the inhomogeneous structures like galaxies and galaxy clusters. However, there’s a catch: the theory involves too many “free” or “adjustable” parameters that can be tweaked at will. In science, too much flexibility can be problematic—it becomes difficult to tell whether a model is genuinely making predictions or simply adapting itself to fit the observed data after the fact.

The international research team has proposed a new model in which the early Universe doesn't require any of these arbitrary parameters. Instead, it depends on a single energy scale that determines all observable predictions. The researchers start from a well-established cosmological state known as de Sitter space-time, a geometric model of a Universe dominated by vacuum energy and expanding at an accelerating rate—like a balloon inflating faster and faster at every point. This new model doesn’t rely on hypothetical fields or particles such as the so-called “inflaton” field. Rather, it suggests that the natural quantum oscillations of space-time itself—in the form of quantum gravitational waves (or “gravitons”)—were enough to trigger the tiny density fluctuations that eventually led to the formation of galaxies, stars, and planets. These gravitational ripples evolve in a nonlinear way, meaning they interact and build complexity over time, leading to testable predictions. Researchers can now analyze, scrutinize, and compare these predictions with data from Earth-based and space-based experiments.

“Understanding the origin of the Universe is not just a philosophical pursuit—it helps us answer fundamental questions about who we are and where everything comes from,” say the authors of the newly published theory. “This new proposal offers a simple yet powerful framework. It delivers clear predictions that can be confirmed or ruled out by future observations—such as the measurement of the amplitude of primordial gravitational waves and statistical studies of cosmic structure. Moreover, it shows that no speculative ingredients are needed to explain the cosmos, just a deep understanding of gravity and quantum physics. This model could mark a new chapter in how we think about the birth of the Universe.”

Publication:
Bertacca, Daniele; Jimenez, Raul; Matarrese, Sabino; Ricciardone, Angelo (2025)
Inflation without an inflaton
Physical Review Research 7(3) L032010; DIO: 10.1103/vfny-pgc2

Quoted in Universe Today, Dr. Raúl Jiménez of ICREA, Spain and co-author of the paper, said:

For decades, we have tried to understand the early moments of the Universe using models based on elements we have never observed. What makes this proposal exciting is its simplicity and verifiability. We are not adding speculative elements but rather demonstrating that gravity and quantum mechanics may be sufficient to explain how the structure of the cosmos came into being.

Abstract

We propose a novel scenario in which scalar perturbations, which seed the large-scale structure of the universe, are generated without relying on a scalar field (the inflaton). In this framework, inflation is driven by a de Sitter space time, where tensor metric fluctuations (i.e., gravitational waves) naturally arise from quantum vacuum oscillations, and scalar fluctuations are generated via second-order tensor effects. We compute the power spectrum of such scalar fluctuations and show it to be consistent with near scale invariance. We derive the necessary conditions under which scalar perturbations become significant and much larger than the tensor modes, and we identify a natural mechanism to end inflation via a transition to a radiation-dominated phase. Our proposed mechanism could remove the need for a model-dependent scenario: the choice of a scalar field, as the inflaton, to drive inflation.

Bertacca, Daniele; Jimenez, Raul; Matarrese, Sabino; Ricciardone, Angelo (2025)
Inflation without an inflaton
Physical Review Research 7(3) L032010; DIO: 10.1103/vfny-pgc2

Copyright: © 2025 The authors.
Published by the American Physical Society. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

This revived de Sitter model, based on the elegant mathematics first explored by Albert Einstein and Willem de Sitter, removes the need to invoke a speculative inflaton field to explain the early rapid expansion of the universe. By showing how gravity alone could have driven this process, the researchers offer a more economical explanation — one that appeals strongly to Occam's razor. It’s a compelling demonstration of how theoretical physics continually seeks to simplify and unify our understanding of nature.

Of course, this does not mean the inflationary model has been discarded. Inflation theory has been highly successful in explaining key cosmological observations, from the uniformity of the cosmic microwave background radiation to the large-scale structure of the universe. What the de Sitter approach offers is a potentially deeper, more fundamental explanation of inflation, showing it may not require an additional, hypothetical force at all.

As with all scientific ideas, this proposal will now be rigorously tested against data and alternative models. Observations — especially of the cosmic microwave background and primordial gravitational waves — will help determine whether this simpler explanation holds up. If it does, it could reshape our understanding of the universe’s earliest moments.

And this is where science stands in stark contrast to religion. Religious explanations were fixed thousands of years ago, impervious to evidence and unchangeable by design. Scientific explanations, by contrast, are provisional, self-correcting, and constantly refined in the light of new discoveries. We do not fill gaps in our knowledge with comforting stories — we investigate, test, and revise. What began as a Bronze Age myth has remained frozen in time; what began as a scientific hypothesis continues to evolve with every new observation. That is why science, not myth, moves us ever closer to understanding how our universe truly began.

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