Dark matter has proved an elusive concept to scientists, with some claiming it does not even exist. Now, researchers think the phenomenon could actually be part of an alternate universe.
By JOHN MAC GHLIONN
Sun, Mar 10, 2024
The behaviour of galaxies would be inexplicable without the existence of dark matter
(Image: Getty)
Scientists believe that dark matter could be viewed as an alternative universe following a breakthrough study.
The new paper by Dr. Arushi Bodas, a postdoctoral fellow at the University of Chicago’s Enrico Fermi Institute, and his colleagues, states that dark matter could and possibly should be viewed as a distorted alternate universe that never fully developed.
But before discussing the paper, it’s important to understand just how mysterious dark matter really is.
That's easier said than done, however.
Despite it constituting more than 80 percent of all matter in the universe, scientists have yet to observe dark matter, Its existence is inferred because the behavior of stars, planets, and galaxies would be wholly inexplicable without its presence.
Scientists believe that dark matter could be viewed as an alternative universe following a breakthrough study.
The new paper by Dr. Arushi Bodas, a postdoctoral fellow at the University of Chicago’s Enrico Fermi Institute, and his colleagues, states that dark matter could and possibly should be viewed as a distorted alternate universe that never fully developed.
But before discussing the paper, it’s important to understand just how mysterious dark matter really is.
That's easier said than done, however.
Despite it constituting more than 80 percent of all matter in the universe, scientists have yet to observe dark matter, Its existence is inferred because the behavior of stars, planets, and galaxies would be wholly inexplicable without its presence.
Dark matter is difficult to observe; in fact, it’s completely imperceptible. It emits zero light or energy, making it undetectable by conventional sensors and detectors.
Scientists believe its composition is the key to understanding its mysterious nature. Visible matter, also known as baryonic matter, is composed of subatomic particles called baryons, which consist of protons, neutrons, and electrons. The composition of dark matter, on the other hand, remains speculative.
Potentially, it could consist of baryons, but it could also be composed of non-baryonic matter, which refers to different types of particles. The prevailing belief among scientists is that dark matter is primarily composed of non-baryonic matter. Another potential candidate is neutralinos, hypothetical particles that are heavier and slower than neutrinos, although they have yet to be observed.
Sterile neutrinos are also considered as a candidate for dark matter. Neutrinos are particles that do not contribute to regular matter. While a stream of neutrinos emanates from the sun, they rarely interact with normal matter and pass through the Earth and billions of inhabitants. Among the three known types of neutrinos, the sterile neutrino is proposed as a potential dark matter candidate. It would only interact with regular matter through gravity.
The most recent hypothesis proposes that dark matter exists in a distorted parallel universe within our own, where atoms are unable to come together. In the realm of ordinary matter, protons and neutrons possess almost identical masses, creating the necessary conditions for the formation of stable atoms.
The recent study proposes the existence of a potential shadow universe where protons and neutrons have asymmetrical masses, resulting in a chaotic mix of subatomic particles that rarely interact. In other words, the polar opposite of how conventional matter operates. This phenomenon could also clarify why dark matter does not aggregate.
Ever since astronomers initially suspected the presence of dark matter in the 1930s, debates surrounding what it is (and isn’t) have raged. Observations indicate that it surpasses ordinary matter by a ratio of 6 to 1. Galaxies and galaxy clusters are surrounded by massive spheres, known as "halos," of dark matter.
To remain undetected, astronomers theorize that this substantial amount of material must be composed of particles that have minimal interaction with ordinary matter or even with each other. Their primary function is to provide the gravitational framework for luminous matter. Astronomers believe that these halos were created in the early stages of cosmic history and subsequently attracted ordinary matter, which, due to its diverse range of behaviors, evolved into complex structures, while dark matter, being inert, remained unchanged.
Dark energy, on the other hand, seems to only serve the purpose of accelerating cosmic expansion, and the existing evidence suggests that it has remained constant throughout the existence of the universe.
Although a minority of scientists reject the idea of dark matter, there is now a plethora of evidence supporting its existence, with one of the most straightforward explanations involving the rotation of galaxies.
As Dr. Don Lincoln, a senior scientist at Fermilab, America’s leading particle physics laboratory, has noted, despite the gravitational pull towards the Sun, the planets' velocities result in nearly circular orbits.
The balance between velocity and gravity dictates that planets farther from the Sun move at a slower pace compared to those in closer proximity. Similarly, in galaxies, stars follow a similar pattern, with the laws of physics making analogous predictions.
Potentially, it could consist of baryons, but it could also be composed of non-baryonic matter, which refers to different types of particles. The prevailing belief among scientists is that dark matter is primarily composed of non-baryonic matter. Another potential candidate is neutralinos, hypothetical particles that are heavier and slower than neutrinos, although they have yet to be observed.
Sterile neutrinos are also considered as a candidate for dark matter. Neutrinos are particles that do not contribute to regular matter. While a stream of neutrinos emanates from the sun, they rarely interact with normal matter and pass through the Earth and billions of inhabitants. Among the three known types of neutrinos, the sterile neutrino is proposed as a potential dark matter candidate. It would only interact with regular matter through gravity.
The most recent hypothesis proposes that dark matter exists in a distorted parallel universe within our own, where atoms are unable to come together. In the realm of ordinary matter, protons and neutrons possess almost identical masses, creating the necessary conditions for the formation of stable atoms.
The recent study proposes the existence of a potential shadow universe where protons and neutrons have asymmetrical masses, resulting in a chaotic mix of subatomic particles that rarely interact. In other words, the polar opposite of how conventional matter operates. This phenomenon could also clarify why dark matter does not aggregate.
Ever since astronomers initially suspected the presence of dark matter in the 1930s, debates surrounding what it is (and isn’t) have raged. Observations indicate that it surpasses ordinary matter by a ratio of 6 to 1. Galaxies and galaxy clusters are surrounded by massive spheres, known as "halos," of dark matter.
To remain undetected, astronomers theorize that this substantial amount of material must be composed of particles that have minimal interaction with ordinary matter or even with each other. Their primary function is to provide the gravitational framework for luminous matter. Astronomers believe that these halos were created in the early stages of cosmic history and subsequently attracted ordinary matter, which, due to its diverse range of behaviors, evolved into complex structures, while dark matter, being inert, remained unchanged.
Dark energy, on the other hand, seems to only serve the purpose of accelerating cosmic expansion, and the existing evidence suggests that it has remained constant throughout the existence of the universe.
Although a minority of scientists reject the idea of dark matter, there is now a plethora of evidence supporting its existence, with one of the most straightforward explanations involving the rotation of galaxies.
As Dr. Don Lincoln, a senior scientist at Fermilab, America’s leading particle physics laboratory, has noted, despite the gravitational pull towards the Sun, the planets' velocities result in nearly circular orbits.
The balance between velocity and gravity dictates that planets farther from the Sun move at a slower pace compared to those in closer proximity. Similarly, in galaxies, stars follow a similar pattern, with the laws of physics making analogous predictions.
Specifically, stars located further from the galactic center should move at a slower pace than those nearer to it.
However, observations by astronomers reveal that stars in the outer regions of galaxies move faster than anticipated. If the laws of gravity and motion hold true, the only plausible explanation is the presence of additional, unseen matter intensifying the gravitational force experienced by these rapidly moving stars.
The new paper by Dr. Bodas and his colleagues is just the latest to solidify the "dark matter really does exist' thesis.
However, observations by astronomers reveal that stars in the outer regions of galaxies move faster than anticipated. If the laws of gravity and motion hold true, the only plausible explanation is the presence of additional, unseen matter intensifying the gravitational force experienced by these rapidly moving stars.
The new paper by Dr. Bodas and his colleagues is just the latest to solidify the "dark matter really does exist' thesis.
Controversial new theory of gravity rules out need for dark matter
Exclusive: Paper by UCL professor says ‘wobbly’ space-time could instead explain expansion of universe and galactic rotation
Hannah Devlin
Exclusive: Paper by UCL professor says ‘wobbly’ space-time could instead explain expansion of universe and galactic rotation
Hannah Devlin
THE GUARDIAN
Science correspondent
Sat 9 Mar 2024
Dark matter is supposed to account for 85% of the mass in the universe, according to conventional scientific wisdom. But proponents of a radical new theory of gravity, in which space-time is “wobbly”, say their approach could render the elusive substance obsolete.
The proposition, outlined in a new paper, raises the controversial possibility that dark matter, which has never been directly observed, is a mirage that a substantial portion of the physics community has been chasing for several decades. The theory is viewed as quite left-field and is yet to be thoroughly tested, but the latest claims are creating a stir in the world of physics.
Announcing the paper on X, Prof Jonathan Oppenheim, of University College London, said: “Folks, something seems to be happening. We show that our theory of gravity … can explain the expansion of the universe and galactic rotation without dark matter or dark energy.”
There are multiple lines of evidence for dark matter, but its nature has remained mysterious and searches by the Large Hadron Collider have come up empty-handed. Last year, the European Space Agency launched a mission, Euclid, aiming to produce a cosmic map of dark matter.
The latest paper, published on the Arxiv website and yet to be peer-reviewed, raises the question of whether it even exists, drawing parallels between dark matter and flawed concepts of the past, such as “the ether”, an invisible substance that was thought to permeate all of space.
“In the absence of any direct evidence for dark energy or dark matter it is natural to wonder whether they may be unnecessary scientific constructs like celestial spheres, ether, or the planet Vulcan, all of which were superseded by simpler explanations,” it states. “Gravity has a long history of being a trickster.”
In this case, the simpler explanation being proposed is Oppenheim’s “postquantum theory of classical gravity”. The UCL professor has spent the past five years developing the approach, which aims to unite the two pillars of modern physics: quantum theory and Einstein’s general relativity, which are fundamentally incompatible.
Oppenheim’s theory envisages the fabric of space-time as smooth and continuous (classical), but inherently wobbly. The rate at which time flows would randomly fluctuate, like a burbling stream, space would be haphazardly warped and time would diverge in different patches of the universe. The theory also envisions an intrinsic breakdown in predictability.
The paper, by Oppenheim and Andrea Russo, a PhD candidate at UCL, claims this take on the universe could explain landmark observations of rotating galaxies that led to the “discovery” of dark matter. Stars at the edges of galaxies, where gravity is expected to be weakest based on visible matter, ought to be rotating more slowly than stars at the centre. But in reality, the orbital motion of stars does not drop off. From this, astronomers inferred the presence of a halo of unseen (dark) matter exerting a gravitational pull.
In Oppenheim’s approach the additional energy required to keep the stars locked in orbit is provided by the random fluctuations in spacetime, which in effect add in a background hum of gravitation. This would be negligible in a high gravity interaction, such as the Earth orbiting the Sun. But in low gravity situations, such as the fringes of a galaxy, the phenomenon would dominate – and cumulatively could account for the majority of the energy in the universe.
“We show that it can explain the expansion of the universe and galactic rotation curves without the need for dark matter or dark energy,” Oppenheim said on X. “We do urge caution, however, since there is other indirect evidence for dark matter, so further calculations and comparison with data are needed. But if it holds, it would appear that 95% of the energy in the universe is due to the erratic nature of spacetime, signalling either a fundamental breakdown in predictability of physics, or we are immersed in an environment which does not obey the laws of classical or quantum theory.”
Not everyone is convinced, including the well-known theorists Prof Carlo Rovelli and Prof Geoff Penington, who have signed a 5,000:1 odds bet with Oppenheim against his theory being proven correct.
“I think it’s good that physicists explore a wide variety of approaches to very difficult problems like combining quantum mechanics with gravity,” said Penington.
“Personally, I don’t think this particular approach is likely to be the correct one. I’ve obviously put my money where my mouth is on that front and there is nothing new in the recent papers that would make me change that assessment.”
Others are more enthusiastic. “I think the authors are on to something really interesting here, exploring some beautiful and novel ideas,” said Prof Andrew Pontzen, a cosmologist at University College London. “However, the challenge for replacing dark matter is that there are so many different lines of evidence that suggest its presence. So far they have only addressed one of these lines. Only time will tell whether the new ideas can truly explain the huge variety of phenomena that point towards dark matter.”
Dark matter is supposed to account for 85% of the mass in the universe, according to conventional scientific wisdom. But proponents of a radical new theory of gravity, in which space-time is “wobbly”, say their approach could render the elusive substance obsolete.
The proposition, outlined in a new paper, raises the controversial possibility that dark matter, which has never been directly observed, is a mirage that a substantial portion of the physics community has been chasing for several decades. The theory is viewed as quite left-field and is yet to be thoroughly tested, but the latest claims are creating a stir in the world of physics.
Announcing the paper on X, Prof Jonathan Oppenheim, of University College London, said: “Folks, something seems to be happening. We show that our theory of gravity … can explain the expansion of the universe and galactic rotation without dark matter or dark energy.”
There are multiple lines of evidence for dark matter, but its nature has remained mysterious and searches by the Large Hadron Collider have come up empty-handed. Last year, the European Space Agency launched a mission, Euclid, aiming to produce a cosmic map of dark matter.
The latest paper, published on the Arxiv website and yet to be peer-reviewed, raises the question of whether it even exists, drawing parallels between dark matter and flawed concepts of the past, such as “the ether”, an invisible substance that was thought to permeate all of space.
“In the absence of any direct evidence for dark energy or dark matter it is natural to wonder whether they may be unnecessary scientific constructs like celestial spheres, ether, or the planet Vulcan, all of which were superseded by simpler explanations,” it states. “Gravity has a long history of being a trickster.”
In this case, the simpler explanation being proposed is Oppenheim’s “postquantum theory of classical gravity”. The UCL professor has spent the past five years developing the approach, which aims to unite the two pillars of modern physics: quantum theory and Einstein’s general relativity, which are fundamentally incompatible.
Oppenheim’s theory envisages the fabric of space-time as smooth and continuous (classical), but inherently wobbly. The rate at which time flows would randomly fluctuate, like a burbling stream, space would be haphazardly warped and time would diverge in different patches of the universe. The theory also envisions an intrinsic breakdown in predictability.
The paper, by Oppenheim and Andrea Russo, a PhD candidate at UCL, claims this take on the universe could explain landmark observations of rotating galaxies that led to the “discovery” of dark matter. Stars at the edges of galaxies, where gravity is expected to be weakest based on visible matter, ought to be rotating more slowly than stars at the centre. But in reality, the orbital motion of stars does not drop off. From this, astronomers inferred the presence of a halo of unseen (dark) matter exerting a gravitational pull.
In Oppenheim’s approach the additional energy required to keep the stars locked in orbit is provided by the random fluctuations in spacetime, which in effect add in a background hum of gravitation. This would be negligible in a high gravity interaction, such as the Earth orbiting the Sun. But in low gravity situations, such as the fringes of a galaxy, the phenomenon would dominate – and cumulatively could account for the majority of the energy in the universe.
“We show that it can explain the expansion of the universe and galactic rotation curves without the need for dark matter or dark energy,” Oppenheim said on X. “We do urge caution, however, since there is other indirect evidence for dark matter, so further calculations and comparison with data are needed. But if it holds, it would appear that 95% of the energy in the universe is due to the erratic nature of spacetime, signalling either a fundamental breakdown in predictability of physics, or we are immersed in an environment which does not obey the laws of classical or quantum theory.”
Not everyone is convinced, including the well-known theorists Prof Carlo Rovelli and Prof Geoff Penington, who have signed a 5,000:1 odds bet with Oppenheim against his theory being proven correct.
“I think it’s good that physicists explore a wide variety of approaches to very difficult problems like combining quantum mechanics with gravity,” said Penington.
“Personally, I don’t think this particular approach is likely to be the correct one. I’ve obviously put my money where my mouth is on that front and there is nothing new in the recent papers that would make me change that assessment.”
Others are more enthusiastic. “I think the authors are on to something really interesting here, exploring some beautiful and novel ideas,” said Prof Andrew Pontzen, a cosmologist at University College London. “However, the challenge for replacing dark matter is that there are so many different lines of evidence that suggest its presence. So far they have only addressed one of these lines. Only time will tell whether the new ideas can truly explain the huge variety of phenomena that point towards dark matter.”
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