Massless gravity is a new explanation for the failure to find dark matter

A new explanation for why dark matter has not been found suggests that it does not exist. Instead, the author believes we have misunderstood gravity. He is not the first to suggest this, but the new proposal, that of massless gravity arising from topological defects in spacetime, is particularly novel.

Dark matter was first proposed in 1932, based on the observation that galaxies move in ways consistent with their mass being greater than the sum of their stars and gas. What started with a few amazing measurements has blossomed. Simple explanations, such as not counting stars, have certainly failed.

A wide range of options have been proposed about the composition of dark matter, from primordial black holes to subatomic particles. So far, we haven’t found any, except for rogue planets and stellar-mass black holes Which can only represent a small fraction of one percent of what is missing.

This has led some physicists to wonder whether we’ve got the whole thing wrong. Maybe there is no dark matter, instead, Gravity works differently On larger scales than we think. One version of this, known as modified Newtonian dynamics (MOND), has received a fair amount of attention, but has proven more popular among online commentators than with physicists, who generally consider it highly improbable.

Professor Richard Liu of the University of Alabama in Huntsville has delved into this situation with his own spin on gravity, which he argues can exist without mass. If he’s right, it would turn much of cosmology upside down, making the search for dark matter an embarrassing diversion in science, like phlogiston. However, there is still a long way to go before it is widely treated as plausible, let alone possible.

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Liu suggests that topological defects arose in spacetime shortly after the Big Bang.

“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 two-dimensional structures such as spherical shells are also possible,” Liu said in his research. statement.

“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 that can be measured in terms of mass – is exactly zero, but when the star is on this shell it is subjected to a great gravitational force that pulls it toward the center of the cortex.”

The force here will have a force equal to the inverse of the distance, not the inverse of the square of the distance as applied under Newton’s law of gravitation. Whether this is physically possible is unproven, but Liu claims to have proven that it works mathematically.

Liu suggests that when light passes an object like a galaxy in gravitational lensing, it is slightly bent inward as it passes through these shells. It would be difficult to distinguish this bend from what would happen if there was more mass pulling on it. The same applies to the star’s movements around the center of the galactic cluster.

Since these two phenomena, Liu notes, are the basis for our confidence in the existence of dark matter, an alternative process for both would make dark matter unnecessary.

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On the other hand, the idea of ​​shells with positive and negative mass on each side is not equally proven, and it is very difficult to explain why they exist at all.

Liu suggests that the creation of these defects was related to a “cosmic phase transition” in the early universe, where matter across the entire universe underwent a change in state.

“My inspiration came from my quest to find another solution to the gravitational field equations in general relativity,” Liu said. This could give “a limited gravitational force in the absence of any detectable mass.”

Liu’s proposal requires several things for which we have no direct evidence, not just one thing, as in the case of dark matter. The same researcher admits: “It is currently unclear what exact form of phase transition in the universe could lead to topological defects of this kind.”

Some possible steps have been suggested, for example that the shells were once straight planes or strings that became coiled. However, currently all of this seems almost ad hoc like Epicycles Ptolemaic astronomers explained the orbits of the planets.

However, in defense of his hypothesis, Liu could point out that the idea is new enough that no one has looked for suitable evidence. On the other hand, billions of dollars and some of the best minds of our generation have been devoted to the unsuccessful search for dark matter.

“This initiative, in turn, is driven by my frustration with the status quo, that is, the idea that dark matter exists despite the lack of any direct evidence for an entire century,” Liu added.

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“Of course, the availability of a second solution, even if very suggestive, is not in itself enough to discredit the dark matter hypothesis – it could be an interesting mathematical exercise at best,” Liu concluded. Evidence that gravity can exist without mass.”

The proposal was published in Monthly Notices of the Royal Astronomical Society.

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