Spacetime Defects Decouple Gravity from Mass in a Dark Matter Alternative

It appears that something is missing from the universe, which physicists refer to as “dark matter.” Yet, even after a century of searching, it hasn’t been found. A new paper suggests an alternative hypothesis, demonstrating how gravity might exist without mass and account for many phenomena attributed to dark matter.

Einstein’s general relativity remains the leading model for explaining gravity. As you may recall from high school physics, gravity is the force generated by masses distorting the fabric of spacetime. The greater an object’s mass, the more pronounced the “dip” in spacetime, resulting in a stronger gravitational force.

Beginning in the 1930s, astronomers noticed some puzzling phenomena. Galaxy clusters appeared to move too fast to remain stable based on visible matter alone, implying the presence of much more unseen matter.

Dark Matter Hypothesis

This led to the dark matter hypothesis, suggesting that vast amounts of invisible material permeate the universe. Over the decades, observations of stellar motion within galaxies and the bending of light through gravitational lenses have supported this idea.

A robust hypothesis should be testable, prompting physicists to design numerous experiments to detect various potential dark matter particles. However, these efforts have so far yielded no results, leading some scientists to explore alternatives like modified gravity or a “dark fluid” filling the cosmos.

Dr. Richard Lieu from the University of Alabama in Huntsville (UAH) has introduced a new theory. He proposes that topological defects, potentially formed during an early universe phase transition, might influence nearby objects and light without having any mass themselves.

“Topological defects are extremely compact regions of space with high matter density, often forming structures like cosmic strings or spherical shells,” explains Lieu. “The shells in my theory have a thin inner layer of positive mass and a thin outer layer of negative mass. Combined, their total mass is zero, but they exert significant gravitational force on a star resting on the shell, pulling it towards the shell’s center.”

This concept could account for stars moving faster than expected based on their visible mass and for galaxies and clusters maintaining their cohesion. If these shells form concentric rings, they might also explain the behavior of gravitational lenses, which magnify distant light sources.

Gravitational Lensing by Singular Shells

“Light passing through concentric singular shells of a galaxy or cluster is deflected slightly inward, towards the center of these structures,” Lieu says. “The cumulative deflection mimics the gravitational effect attributed to large amounts of dark matter, similar to the observed velocities of stellar orbits.”

Though inventing a new phenomenon might seem speculative, Lieu’s idea has some basis. Negative mass, while sounding like science fiction, has been modeled and even demonstrated in fluids and particles, where an object moves backward when pushed. Additionally, massive ring structures observed in space, not easily explained by dark matter, could support the existence of these topological defects.

While intriguing, this theory faces several challenges. The paper doesn’t detail how these defects form, how to observe these shell structures, or whether this model can fully replace dark matter or merely reduce its significance. Nonetheless, it’s the first model suggesting gravity could exist without mass, opening new avenues for understanding galaxy and cluster formation.

Read the original article on: New Atlas

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