The entire universe may be rotating—just like its individual components, from massive galaxies to solar systems and planets—a possibility that could help explain the long-standing “Hubble tension” that has puzzled scientists for years.
None of the currently accepted models of the universe account for any overall spin. Instead, they describe it as expanding uniformly in all directions. However, these models run into trouble with the so-called Hubble tension, a discrepancy where different methods of measuring the universe’s expansion yield conflicting results.
“To paraphrase the Greek philosopher Heraclitus of Ephesus, who famously said ‘Panta Rhei’—everything moves—we thought that perhaps Panta Kykloutai—everything turns,” said István Szapudi of the University of Hawaiʻi at Mānoa, co-author of the new study.
Measuring the Expansion
Astrophysicists currently rely on two main techniques to measure how fast the universe is expanding. One involves observing relatively recent events, such as supernovae and distant galaxies, to measure expansion over the last few billion years. The other looks much farther back—about 13 billion years—by studying relic radiation from the Big Bang.
“The Hubble tension, the inconsistency of the late and early time measurements of the universe’s expansion rate, emerges as the most significant chink in the otherwise shiny armour of the concordance Lambda cold dark matter (CDM) model,” the authors write in their paper.
The “Hubble constant”—a term first proposed by astronomer Edwin Hubble in 1929—defines the universe’s rate of expansion. Yet researchers have long struggled to agree on a precise value, with measurements consistently producing different results. Despite increasing observational data, the Hubble constant has remained elusive. This growing inconsistency is considered the most significant flaw in the prevailing CDM model of the universe.
“The discrepancy has been established in a wide range of data sets,” the authors add.
Modeling the Universe
The research team began with a conventional mathematical model of the universe based on expected behavior. Their innovation was to introduce a small degree of rotation. When tested against existing measurements, the modified model proved surprisingly accurate.
“Much to our surprise, 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!” said Szapudi.
A Slow Spin
In their revised model, the universe rotates slowly—completing a full revolution once every 500 billion years. While such a slow spin would be extremely difficult to detect, it may account for the discrepancies observed in current measurements of universal expansion. The model doesn’t fundamentally alter the laws of physics but suggests a different overall shape or motion for the universe.
The researchers also constrained their model to ensure the rotational speed remains below the speed of light. Intriguingly, they found that “the allowed maximal rotation is approximately the same as the one required to solve the Hubble Puzzle.”
To continue their work, the team plans to enhance their computer model. The current version relies on Newtonian physics, which is sufficient for initial exploration but will need to incorporate general relativity for more accurate modeling. Proving that the universe spins will be a far greater challenge—scientists don’t yet know how such a slow rotation could be directly observed.
The paper “Can Rotation Solve the Hubble Puzzle?” appeared on March 21, 2025 in Monthly Notices of the Royal Astronomical Society.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.