For over a century, cosmology has moved forward on the belief that the universe, born in a ferocious Big Bang, has expanded evenly in all directions. It was a tidy model—clean, isotropic, and symmetric. But a new study published in the Monthly Notices of the Royal Astronomical Society suggests a stunning possibility: the universe might not be so symmetrical after all. It may, in fact, be spinning—just at a pace so slow it’s eluded detection.
At the heart of this cosmic rethink is István Szapudi, an astronomer at the University of Hawaiʻi at Mānoa’s Institute for Astronomy. Drawing inspiration from the ancient Greek philosopher Heraclitus, who declared, “panta rhei”—everything flows—Szapudi and his collaborators propose a modern cosmic update: panta kykloutai—everything turns.
This isn’t just poetic musing. If correct, the theory could unlock one of the most baffling contradictions in cosmology: the so-called Hubble tension—a puzzling mismatch between two ways of measuring the universe’s expansion rate. Szapudi’s elegant yet radical idea: maybe the universe isn’t just expanding, maybe it’s also imperceptibly rotating, and that motion has been subtly distorting our measurements all along.
The Hubble Tension: A Cosmic Conflict
The Hubble tension is one of the most vexing problems in modern astronomy. When astronomers try to measure how fast the universe is expanding—the so-called Hubble constant—they get two conflicting answers, depending on the method used.
One method looks at Type Ia supernovae—stellar explosions that act as cosmic mile markers. This technique estimates how quickly the universe has been stretching over the last several billion years and generally returns a faster rate of expansion.
The second method dives deep into the past—back nearly 13.8 billion years—by analyzing the cosmic microwave background (CMB), the relic radiation left behind from the Big Bang. This early-universe method tends to produce a slower expansion rate.
Despite increasingly precise observations, the gap between these two estimates has stubbornly refused to close. It’s not a minor discrepancy—it suggests that our fundamental understanding of the cosmos might be missing a crucial piece.
Adding a Cosmic Twist
This is where Szapudi and his team’s new model comes in. What if, they asked, the universe wasn’t perfectly still in a rotational sense? What if it slowly, almost imperceptibly, turned on a cosmic axis?
At first glance, the idea seems outrageous. Our best observations—such as those from the Planck satellite—support a universe that looks roughly the same in every direction. Any rotation, it would seem, should produce a noticeable distortion. But what Szapudi’s team discovered is that an incredibly slow rotation could exist without violating observational constraints.
Their theoretical universe rotates just once every 500 billion years—about 36 times slower than the current age of the universe itself. At such a glacial pace, the rotation would be practically invisible with existing instruments. But its cumulative effects over billions of years could subtly alter how we perceive distances and expansion rates in the cosmos.
A Gentle Spin with Big Consequences
The researchers developed a mathematical framework that first adhered to the standard model of cosmology—based on general relativity and the assumption of uniform expansion. Then they gently introduced a small rotational component. It was a minimal tweak, but it had dramatic implications.
“Much to our surprise,” Szapudi explained, “we found that our model with rotation resolves the paradox without contradicting current astronomical measurements. Even better, it is compatible with other models that assume rotation. Therefore, perhaps, everything really does turn. Or, panta kykloutai.”
What makes the proposal so powerful is its subtlety. It doesn’t break the known laws of physics. It doesn’t require exotic new particles or dark energy tweaks. It simply suggests that the universe’s metric—the very fabric of spacetime—might include a slowly spinning frame of reference.
And that twist could be the hidden hand behind the Hubble tension.
Echoes from the Early Universe?
A rotating universe isn’t a brand-new idea—it’s been whispered about by theorists for decades. Some alternative cosmological models have explored the idea of global rotation, but they’ve often been dismissed for conflicting with observational data or violating the cherished cosmological principle—the assumption that the universe is homogeneous and isotropic at large scales.
Szapudi’s work, however, offers a fresh approach. By introducing a mathematically consistent and physically plausible model that includes only a minuscule degree of rotation, the team threads the needle between innovation and observation.
Such a rotation could subtly influence how we interpret the CMB or how light travels across vast intergalactic distances. Over time, it could skew distance estimates and redshift calculations—both critical to determining the universe’s expansion rate.
This might explain why the early-universe method (using the CMB) and the late-universe method (using supernovae and galaxies) return different results. They’re measuring expansion from slightly different rotational frames.
What Would a Rotating Universe Look Like?
The idea of a spinning universe might conjure images of galaxies spiraling outward like cosmic fireworks. But in reality, such rotation would be almost unnoticeable on human timescales—or even galactic ones.
A full rotation every 500 billion years means the motion is so slight that it wouldn’t affect local physics. Galaxies would still form, stars would still shine, and life would still evolve as usual. But over billions of light-years, this rotation could change how light curves through space, altering the way we see the universe’s structure and expansion.
If real, this rotation would mean the universe has a kind of preferred direction or axis—a concept known as anisotropy. That alone would upend some core assumptions of cosmology and might even offer new clues about the early universe’s conditions and symmetry-breaking events after the Big Bang.
From Hypothesis to Detection
The next challenge for Szapudi and his colleagues is to transform their elegant mathematics into a full-fledged computer simulation. That would allow them to test their model against more datasets—from galaxy distributions to gravitational lensing effects and deeper CMB analyses.
Crucially, astronomers will need to identify observational fingerprints of rotation. Could the cosmic microwave background contain faint swirls or directional patterns? Might galaxy clusters show subtle alignments? Would redshifts vary along a specific axis?
These are open questions, and answering them will require ingenuity, precision, and perhaps new instruments.
Implications Beyond the Hubble Tension
If confirmed, a rotating universe would ripple through nearly every branch of physics and cosmology. It could reshape how we model large-scale structure formation, influence theories about the universe’s fate, and even lead to new insights about gravity.
Could rotation be tied to the mysterious dark energy driving accelerated expansion? Might it connect with primordial gravitational waves or quantum fluctuations from the earliest moments of the cosmos?
Furthermore, it invites a deeper philosophical inquiry: If the universe has a direction, does that mean it has a beginning, a purpose, or a broader structure beyond our visible horizon?
These aren’t just theoretical musings—they’re questions at the very heart of how we understand reality.
A New Era of Cosmic Curiosity
Einstein’s general relativity revolutionized our understanding of gravity by treating it not as a force, but as a curvature in spacetime. Now, over a century later, Szapudi’s suggestion of a rotating spacetime could represent another paradigm shift.
For now, the theory is a hypothesis—elegant, plausible, but unconfirmed. Yet like all great scientific ideas, it has sparked new curiosity, opening doors to previously unimagined possibilities.
As Szapudi put it with a nod to ancient wisdom, “Everything turns.” If that’s true—not just metaphorically, but literally—it may mean the universe is far more dynamic, more asymmetric, and more astonishing than we ever imagined.
And as we refine our instruments and peer deeper into space, we may soon find out if the cosmos has indeed been slowly spinning, silently shaping the fabric of everything we see.
Reference: Balázs Endre Szigeti et al, Can rotation solve the Hubble Puzzle?, Monthly Notices of the Royal Astronomical Society (2025). DOI: 10.1093/mnras/staf446