MOND vs. Dark Matter: Research suggests that the rotation curves of galaxies remain flat indefinitely

In a discovery that challenges conventional understanding of cosmology, scientists at Case Western Reserve University have unearthed new evidence that could reshape our perception of the cosmos.

Tobias Mistele, a postdoctoral researcher in the Department of Astronomy at Case Western Reserve’s College of Arts and Sciences, pioneered a revolutionary technique that used “gravitational lenses” to delve into the enigmatic realm of dark matter. He discovered that the rotation curves of galaxies remain flat for millions of light years and that there is no end in sight.

The work has been published on the pre-print server arXiv.

Scientists have previously believed that the rotation curves of galaxies should decrease as you look further into space.

Traditionally, the behavior of stars in galaxies has puzzled astronomers. According to Newtonian gravity, stars at the outer edges should be slower because of the reduced gravity. This was not observed, leading to the inference of dark matter. But even dark matter halos should come to an end, so rotation curves should not remain flat indefinitely.

Mistele’s analysis defies this expectation and yields a surprising revelation: the influence of what we call dark matter extends far beyond previous estimates, stretching at least a million light-years from the galactic center.

Such a long-term effect could indicate that dark matter – as we understand it – may not exist at all.

“This finding challenges existing models,” he said, “suggesting that either vastly extended dark matter haloes exist or that we need to fundamentally reevaluate our understanding of gravitational theory.”

Stacy McGaugh, professor and director of the College of Arts and Sciences’ Department of Astronomy, said Mistele’s findings, scheduled for publication in the Astrophysical diary letterspush traditional boundaries.

“The implications of this discovery are profound,” McGaugh said. “It could not only redefine our understanding of dark matter, but also invites us to explore alternative theories of gravity, challenging the structure of modern astrophysics.”

Turning Einstein’s theory upside down

The main technique Mistele used in his research, gravitational lensing, is a phenomenon predicted by Einstein’s general theory of relativity. Essentially, it occurs when a massive object, such as a cluster of galaxies or even a single massive star, bends the path of light coming from a distant source. This bending of light occurs because the mass of the object distorts the fabric of spacetime around it. This deflection of light by galaxies persists on a much larger scale than expected.

As part of the research, Mistele plotted the so-called Tully-Fisher relationship on a map to highlight the empirical relationship between a galaxy’s visible mass and its rotation rate.

“We knew this relationship existed,” Mistele said. “But it wasn’t clear that the relationship would last the further away you go. To what extent does this behavior persist? That’s the question, because it can’t last forever.”

Mistele said his discovery underlines the need for further research and collaboration within the scientific community – and the possible analysis of other data.

McGaugh noted the Herculean – so far still unsuccessful – efforts in the international particle physics community to detect and identify dark matter particles.

“Either the dark matter halos are much larger than we expected, or the whole paradigm is wrong,” says McGaugh.

“The theory that predicted this behavior in advance is the modified gravity theory that MOND postulated by Moti Milgrom in 1983 as an alternative to dark matter. So the obvious and inevitably controversial interpretation of this result is that dark matter is a chimera; Perhaps the evidence is because it points to a new theory of gravity that goes beyond what Einstein taught us.”