New ground study suggests gravity can exist without mass: ScienceAlert

What is gravity without mass? both of them Revolutionary Newton Laws describing its global effect and Einstein's proposal of dimpled spacetime, we used to think that gravity lies exclusively in the realm of matter.

Now, a wild new study suggests that gravity can exist without mass, eliminating the need for one of the most elusive substances in our universe: dark matter.

Dark matter is a hypothetical, invisible mass that is believed to make up 85% of the total mass of the universe. Originally created for Calculating galaxies Although they hold together under high-speed rotation, they have not yet been observed directly, leading physicists to suggest all kinds of Ideas out there To avoid calling this elusive material a way to fill in the gaps in existing theories.

The latest demonstration in this context comes from astrophysicist Richard Liu at the University of Alabama in Huntsville, who proposed that instead of dark matter holding galaxies and other objects together, the universe… May contain thin, crust-like layers of “topological defects” Which leads to gravity without any fundamental mass.

Leo began trying to find another solution to the problem Einstein's field equationsWhich links the curvature of space-time to the presence of matter within it.

As Einstein described it in his theory in 1915 General relativitySpacetime wraps around bundles of matter and streams of radiation in the universe, depending on their energy and momentum. This energy is of course related to mass in Einstein's famous equation: E=mc².

So an object's mass is related to its energy, which leads to the curvature of spacetime – and this curvature of spacetime is What Einstein described as gravityIt is a degree more complex than Newton's 17th century approximation of gravity Force between two objects with mass. In other words, gravity appears to be closely related to mass.

Not so, says Liu.

In his work, Liu set out to solve a simplified version of Einstein's field equations that allow for a finite gravitational force in the absence of any detectable mass. he He says His efforts were “motivated by my frustration with the status quo – the idea that dark matter exists despite the lack of any direct evidence for a century.”

Liu's solution consists of shell-shaped topological defects that may occur in very compressed regions of space with a very high density of matter.

These groups of concentric shells contain a thin layer of positive mass tucked inside an outer layer of negative mass. The two masses cancel each other out, so the total mass of the two layers is exactly zero. But when a star falls on this crust, it is exposed to a great gravitational force that pulls it towards the center of the crust.

“What my paper claims is that the shells it assumes are at least massless,” Liu said He says. If these controversial suggestions carry any weight, “then there is no need to perpetuate this seemingly endless search for dark matter.” Add.

The next question then is how to confirm or refute the shells proposed by Liu through observations.

“The increasing frequency of observations of rings and galaxy-like formations in the universe provides evidence for the type of source proposed here.” He writes in his paper. Although he admits that the solution he proposed is “very suggestive” and cannot alone refute the dark matter hypothesis.

“It can be an interesting exercise at best,” Leo He finishes. “But it's the first [mathematical] Evidence that gravity can exist without mass.”

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