A recent study that poses new challenges to the existence of dark matter suggests that gravity may exist without matter.
Although all life on Earth experiences its effects daily, gravity remains one of the great mysteries of modern physics. Now a new study published by Dr. Richard Lieu with The University of Alabama in Huntsville (UAH) proposes that the gravitational effects seen in galaxies and clusters may be the result of what he likens to topological defects in the universe, a theory that yes. they do not require the inclusion of dark matter to explain the phenomena observed in our universe.
Dark matter, a hypothetical nonluminous material believed by many to make up as much as 85% of the matter in the known universe, was originally conceived to help explain gravitational effects that scientists currently cannot explain with Einstein’s theory of general relativity. First proposed in 1932 by Dutch astronomer Jan Oort, astrophysicists have continued to search for evidence of this mysterious invisible material, which remains unconfirmed.
But not everyone is convinced that dark matter offers the best solution to the questions astrophysicists have about the universe. In his recent study, Lieu proposes a completely new approach that could fundamentally change our current understanding of matter and gravitational forces in the universe.
“My own inspiration came from my quest to further solve the gravitational field equations of general relativity—a simplified version of which, applicable to the conditions of galaxies and galaxy clusters, is known as Poisson’s equation,” Lieu said recently of his unique approach.
Lieu, Distinguished Professor of Physics and Astronomy at UAH, says his interpretation of the problem “provides a finite gravitational force in the absence of any detectable matter,” an approach he says arose out of his frustration with prevailing ideas about dark matter that have increasingly than a century since the idea was originally proposed, any direct evidence is lacking.
According to Lieu, concentric structures consisting of shell-like topological defects could account for the excess gravity that current models require to bind galaxies or clusters together. These structures likely have their origins in a cosmological phase transition—an event where the state of matter changes throughout the universe—that occurred very early in the universe.
Lieu says such a phase transition could potentially generate massless gravitational effects.
“Topological defects are compact regions of space with very high matter density, usually in the form of cosmic strings or spherical shells,” Lieu said in a statement. These spherical shells would probably consist of an inner layer of positive matter surrounded by an outer layer composed of negative matter. The result would be a structure with a net weight of zero. Despite having essentially no mass, objects near these shells would still experience significant gravitational forces pulling them toward their center.
According to Einstein’s theories, gravity distorts space-time and causes interactions between objects regardless of their mass. Even immaterial photons are affected by gravity, for example when light is distorted as it passes near extremely dense celestial objects.
For Lieu, observations of the deflection of light and the velocities of stellar orbits in galaxies may be the result of these hypothetical massless envelopes, which he says could offer a better explanation than the theoretical existence of dark matter in these regions.
Although Lieu does not currently offer an explanation for how these matterless shells could form, he says his alternative theory could lead to new discoveries that could solve such long-standing questions or even help us confirm the existence of dark matter.
“The availability of the second solution, while highly suggestive, is not enough to discredit the dark matter hypothesis,” says Lieu, adding that his study can only be “an interesting mathematical exercise at best.”
If proven by further research, Lieu’s theory could indeed offer proof that gravity can exist without the need for matter. The discovery could potentially represent a major advance in our understanding of the universe and one of its most enduring mysteries.
Lieu’s recent study, “Bounding of Cosmological Structures by Immaterial Topological Defects,” appeared in Monthly Notices of the Royal Astronomical Society.
Micah Hanks is the editor-in-chief and co-founder of The Debrief. He can be reached by e-mail at the address micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.