Study shows gravity can exist without mass, dark matter could be myth

> According to the theory of general relativity, a galaxy must have a certain amount of mass to be held together by gravity. However, scientists don’t see enough visible mass in many galaxies in the universe, yet gravity keeps such galaxies intact. How’s this even possible?

> This is where the concept of dark matter comes into play. Scientists believe that galaxies have invisible mass in the form of matter that doesn’t interact with light. The gravity holding these galaxies exists because of this invisible mass.

> For decades, this explanation has supported the existence of the hypothetical dark matter. However, a new study claims that gravity can exist even without mass, potentially eliminating the need for dark matter altogether.

> According to Lieu, the gravity needed to hold some galaxies or clusters together might come from “shell-like topological defects.” These defects might appear as long, linear formations called cosmic strings, or as flat, shell-like shapes.

> “The shells in my paper consist of a thin inner layer of positive mass and a thin outer layer of negative mass; the total mass of both layers — which is all one could measure, mass-wise — is exactly zero, but when a star lies on this shell it experiences a large gravitational force pulling it towards the center of the shell,” Lieu explained.

> It is somewhat similar to how photons, which themselves do not have mass, still experience gravity due to the presence of big astronomical entities. This is because when gravity warps space and time, it interacts with everything within the curvature whether it has mass or not.

> When light travels through multiple shells, the combined effect causes a noticeable bend, which looks similar to the effect of a large amount of dark matter, just like how the speed of stars in orbit appears to be affected by dark matter.

> However, according to the current study, there is no dark matter and the gravitational bending is entirely the result of the topological defects. “It is unclear presently what precise form of phase transition in the universe could give rise to topological defects of this sort,” Lieu said.

When you’re so attractive, you put Dark Matter out of a job.