The theory of general relativity may have been developed by Albert Einstein at the beginning of the 20th century, but it still raises many questions that fuel current scientific experiments and avenues of research. This concept, more than 100 years old, is that it is the presence of matter that influences the movement of the stars.
However, it has often been possible to observe systems where mass was not enough to explain its behavior, recalls Interesting Engineering. The scientific community has therefore used dark matter to fill the gaps between theory and observations. Dark matter is an invisible mass that does not interact with light. Since then, its research and explanation have been one of the key research avenues in general physics.
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Topological defects to explain gravitational curvatures rather than dark matter
However, distinguished professor of physics and astronomy Richard Lieu, of the University of Alabama in Huntsville, disputes the existence of this hypothetical matter. In his study, published in the journal Monthly Notices of the Royal Astronomical Society, he assures that gravity could exist without needing mass to exert itself. With this new principle, he undermines the role of dark matter.
Richard Lieu explains that this theory “stems from his frustration with the status quo, namely the notion of the existence of dark matter despite the absence of direct evidence for a century”. He believes that topological defects could be the cause of gravity.
Topological defects are compact structures with a high density of matter present only in space. Their origin is believed to date back to the early universe during a phase change, an event which saw matter undergo a major physical change. They take the form of long linear formations (called “cosmic strings”) or flat, shell-like shapes, Interesting Engineering says.
“The total mass of the two layers – which is all that can be measured in terms of mass – is exactly zero, but when a star rests on this shell, it experiences a large gravitational force which pulls it towards the center of the shell”specifies Richard Lieu.
An explanation that alone is not enough to discredit the dark matter hypothesis
According to the theory of general relativity, gravitational curvatures (the curves of light beams along a massive astronomical object) provide indirect evidence for the existence of mass and gravity on an object. Thus, when a gravitational curvature is observed, it is today accepted that it is the expression of a force of gravity imposed by a mass of invisible dark matter.
But for Professor Richard Lieu, galaxies and clusters whose mass is not visible are made up of topological defects resembling shells. Each time a shell is passed through by light, it is attracted towards the center of these structures, which would explain the gravitational curvatures. Under this theoretical scheme, dark matter does not exist.
“It is not yet clear what precise form of phase transition in the universe could give rise to topological defects of this type”recognizes Richard Lieu.
Also, he adds that his theory is not enough “alone to discredit the dark matter hypothesis”. However, “this is the first proof that gravity can be exerted without mass”concludes the professor.
