What Is Dark Matter?
Dutch astronomer Jan Oort first suggested dark matter in 1932, a form of matter believed to make up about 27% of the universe. Unlike ordinary matter, dark matter does not emit, absorb, or reflect light, making it invisible to the eye.
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Scientists infer the existence of dark matter from its gravitational influence on visible matter, such as stars and galaxies.
The Fundamental Force of Nature
Gravity, one of the four fundamental forces of nature, is a force that attracts objects with mass towards each other. This is crucial in shaping the universe at all scales as it pulls objects towards each other, giving them weight and motion, and encouraging their evolution.
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According to Albert Einstein’s theory of general relativity, gravity comes from the curvature of space-time caused by the presence of mass and energy. The more mass an object has, the greater its gravitational influence on other objects.
The Mystery Behind Gravity
Despite the importance of gravity, this force remains one of the least understood in physics, making it even more difficult to study and explain dark matter and dark energy.
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Even though there have been decades of extensive research, dark matter’s exact nature remains unknown. However, a recent study by Dr. Richard Lieu at the University of Alabama in Huntsville hopes to solve the puzzle of this phenomenon.
Dark Matter May Just Be Gravity
Lieu published a paper in the Monthly Notices of the Royal Astronomical Society, explaining how gravity can exist without mass.
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This radically new, thought-provoking research offers an alternative theory that challenges the need for dark matter.
The Inspiration for the Study
“My own inspiration came from my pursuit for another solution to the gravitational field equations of general relativity,” says Lieu, a distinguished professor of physics and astronomy at UAH.
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“This initiative is in turn driven by my frustration with the status quo, namely the notion of dark matter’s existence despite the lack of any direct evidence for a whole century.
A New Function of Gravity
Lieu states that concentric sets of shell-like topological defects in structures commonly found throughout the cosmos could cause the “excess” gravity needed to bind a galaxy or cluster together.
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These defects were likely created during a cosmological phase transition that occurred early in the universe’s existence. This physical process changed the overall state of matter across the entire universe.
The Creation of Topological Effects
“It is unclear presently what precise form of phase transition in the universe could give rise to topological defects of this sort,” Lieu says.
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“Topological effects are very compact regions of space with a very high density of matter, usually in the form of linear structures known as cosmic strings, although 2D structures such as spherical shells are also possible.”
The Effects on the Shells
Lieu’s paper theorizes that the shells of these large-scale structures are massless, suggesting that gravity has been mistaken for dark matter for decades.
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“Of course, the availability of a second solution, even if it is highly suggestive, is not by itself sufficient to discredit the dark matter hypothesis — it could be an interesting mathematical exercise at best,” Lieu states.
Gravity Can Work with Massless Objects
The shells proposed in Lieu’s paper consist of a thin inner layer of positive mass and a thin outer layer of negative mass, making the total mass of both layers exactly zero. Despite this, a large gravitational force pulls them together.
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Similar to massless photons that experience gravitational effects, gravity warps space-time to enable all objects to interact with each other, whether they have mass or not.
Dark Matter May Not Exist
“Gravitational bending of light by a set of concentric singular shells comprising a galaxy or cluster is due to a ray of light being deflected slightly inwards — that is, towards the center of the large-scale structure, or the set of shells — as it passes through one shell,” Lieu notes.
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Lieu explains that light traversing through multiple shells could cause this effect, creating an appearance similar to gravitational influence. Previously understood as dark matter, Lieu’s research suggests that this phenomenon is actually gravity acting in an unfamiliar way.
Waiting for Confirmation
Lieu’s theory and research challenge the century-old notion of dark matter and propose that gravity can function in a fundamentally new way. By demonstrating how gravity can exist without mass through the concept of massless shells, Lieu has opened up a new way of thinking about the universe.
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However, further investigation is necessary to evaluate Lieu’s research and confirm whether his theory holds weight.