New Theory Suggests Lesser Need To Hunt for Dark Matter; Additional Gravity May Be Needed To Hold a Galaxy Together

An astrophysicist proposes the idea that gravity may actually exist without mass and that dark matter may not be needed to explain the phenomena observed in the cosmos.

Dark Matter and Gravity

Dark matter is a hypothetical, elusive substance which is believed to account for 80% of the matter in our universe. Until now, scientists find it hard to detect this mysterious form of matter because it does not absorb, emit, or reflect light. Instead, they assume its existence from its gravitational effects on visible matter, like the distortion of observed light from distant stars.

On the other hand, gravity is the force in the universe that pulls all objects toward one another, as long as they have mass or energy. For many years, scientists have long suspected that invisible dark matter is the source of additional gravity which holds together galaxy and galaxy clusters.

According to Albert Einstein, gravity warps space-time and causes interactions between objects regardless of whether they have mass. For instance, even photons without mass are affected by gravity, since light gets warped as it passes by dense cosmic objects.

Ending the Search for an Elusive Substance

In a recent study, physics and astronomy professor Richard Lieu from the University of Alabama in Huntsville proposed a new theory which can lessen the search for the existence of dark matter. His findings are described in the paper "The binding of cosmological structures by massless topological defects."

According to Lieu, the additional gravity required to hold a galaxy or galaxy cluster together may come from shell-like topological defects in structures that are typically found throughout our universe.

Such defects were likely formed during the early stages of the cosmos when a cosmological phase transition took place. During this physical process, the overall state of matter changes together across the entire universe.

Lieu further explained that the topological effects contain a very high density of matter in space. They are usually in the form of linear structures called cosmic strings, although two-dimensional structures like spherical shells are also possible.

The shells described by Lieu in his paper are composed of a thin inner layer of positive mass and thin outer layer of negative mass. The total mass of the two layers is exactly zero. However, it experiences a large gravitational force that pulls it towards the center when a star lies on this shell.

For Lieu, the mass-less shell-like defects could be the one responsible for observations of the deflection of light and the velocities of stellar orbits in galaxies. He argues that this theory can help in explaining the phenomena better than the theoretical existence of dark matter.

Additionally, the deflection of light and stellar orbital velocities could be the only explanation by which one gauges the strength of the gravitational field in a large-scale structure, whether it is a galaxy or a cluster of galaxies. Lieu's paper argues that at least the shells it posits are massless, so there is no need for the perpetual search for dark matter.