by According to conventional scientific wisdom, 85% of the mass of the universe is estimated to be dark matter. But proponents of a radical new theory of gravity, in which space-time is “twitchy”, say their approach could leave out the elusive substance.
The proposition, described in a new paper, raises the controversial possibility that dark matter is a mirage, never directly observed, which much of the physics community has been chasing for decades. The theory is considered quite left field and has yet to be thoroughly tested, but the latest claims are causing a stir in the world of physics.
Announcing the paper on X, Professor Jonathan Oppenheim, from University College London, said: “Guys, something seems to be happening. We show that our theory of gravity … can explain the expansion of the universe and galactic rotation without dark matter or dark energy.”
There are multiple lines of evidence for dark matter, but its nature remains a mystery and searches from the Large Hadron Collider have come up empty. Last year, the European Space Agency launched a mission, Euclid, which aims to produce a cosmic map of dark matter.
The latest paper, published on the Arxiv website and still undergoing peer review, raises the question of whether it even exists, drawing parallels between dark matter and flawed concepts of the past, such as “the ether”. it was an invisible substance. it is thought to permeate all space.
“In the absence of any direct evidence of dark energy or dark matter it is natural to wonder whether they may be unnecessary scientific constructs like celestial spheres, ether, or the planet Vulcan, which have been replaced by simpler explanations all,” he says. “Gravity has a long history of being a trickster.”
In this case, the simplest explanation proposed is Oppenheim’s “postquantum theory of classical gravity”. The UCL professor has spent the past five years developing the approach, which aims to unify two fundamentally incompatible pillars of modern physics: quantum theory and Einstein’s general relativity.
Oppenheim’s theory envisages that the fabric of space-time will be smooth and continuous (classical), but inherently coarse. The rate at which time flows would vary randomly, like a tidal current, space would be haphazardly woven and time would conflict with each other in different patches of the universe. The theory also envisages an intrinsic breakdown of predictability.
The paper claims that this view of the universe could explain significant observations of rotating galaxies that led to the “discovery” of dark matter. Stars on the edges of galaxies, where gravity is expected to be weakest based on visible matter, should rotate more slowly than stars in the center. But in reality, the orbital motion of the stars does not fall out. From this, the astronomers concluded that a mass of invisible (dark) matter was present due to gravity.
In Oppenheim’s approach the extra energy needed to keep the stars locked in orbit is provided by the random fluctuations in spacetime, which actually interferes with background gravity. This would be negligible in a high gravity interaction, such as the Earth orbiting the sun. But in situations with low gravity, such as the edge of a galaxy, the phenomenon would dominate – and together it could be responsible for the majority of the energy in the universe.
“We show that it can explain the expansion of the universe and the galactic rotation curves without the need for dark matter or dark energy,” Oppenheim said on X. “We want to be careful, however, since there is other indirect evidence on dark matter, so further calculations and comparison with data are needed. But if so, then 95% of the energy in the universe appears to be due to the chaotic nature of spacetime, indicating a fundamental breakdown of the predictability of physics, or we are immersed in an environment that does not obey with the laws of classical or quantum theory.”
Not everyone is convinced, including well-known theorists Professor Carlo Rovelli and Professor Geoff Penington, who signed a 5,000:1 odds bet with Oppenheim against his theory being correct.
“I think it’s good that physicists explore a wide range of approaches to very difficult problems like combining quantum mechanics with gravity,” Penington said.
“Personally, I don’t think this particular approach is likely to be the right one. I’ve obviously put my money where my mouth is on that front and there’s nothing new in the recent papers to make me change that assessment.”
Others are more enthusiastic. “I think the authors are on to something really interesting here, exploring some beautiful and fresh ideas,” said Professor Andrew Pontzen, a cosmologist at University College London. “However, the challenge with replacing dark matter is that there are so many different lines of evidence suggesting its existence. So far they have only addressed one of those lines. Only time will tell if the new ideas can truly explain the vast variety of phenomena that point to dark matter.”
