Physics

Dark matter and dark energy may really be one "dark fluid" with negative mass

Dark matter and dark energy ma...
A new theory suggests that the universe is filled with a dark fluid that has negative mass, which could explain both dark matter and dark energy
A new theory suggests that the universe is filled with a dark fluid that has negative mass, which could explain both dark matter and dark energy
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A new theory suggests that the universe is filled with a dark fluid that has negative mass, which could explain both dark matter and dark energy
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A new theory suggests that the universe is filled with a dark fluid that has negative mass, which could explain both dark matter and dark energy

The Standard Model of particle physics is currently our best understanding of how the universe works – but it only describes about five percent of everything in it. The rest is made up of what we call dark matter and dark energy, which are so far only known through their gravitational interactions with regular matter. Now, an astrophysicist from Oxford has put forward a new theory that suggests that dark matter and dark energy are actually part of the same phenomenon: a "dark fluid" with negative mass that fills the universe.

In a way, dark matter and dark energy are both placeholder concepts, plugging holes between the Standard Model and what we actually observe. For instance, the observed movement and distribution of galaxies doesn't make sense if their mass is limited to the stuff we can see. Since the 1930s, this hidden extra mass has been dubbed dark matter.

Dark energy is a more recent concept. The observation that the expansion of the universe seems to be accelerating was only made in 1998, when it was discovered that more distant objects are moving away from us faster than those closer by. The mysterious force that drives this, which we still know very little about, is now referred to as dark energy.

Taken together, dark matter and dark energy form the basis of our current standard model of Big Bang cosmology, the Lambda-CDM model. The Lambda in that name denotes dark energy as a kind of cosmological constant, while CDM stands for "cold dark matter," which seems to be the most accurate theory of the stuff – it's "cold" because it moves relatively slowly and interacts fairly weakly with ordinary matter.

Dark matter and dark energy have always been treated as separate entities, but are they in fact two sides of the same coin? That's the core idea behind the new theory put forward by Oxford astrophysicist Jamie Farnes, which may expand on the Lambda-CDM model.

Dark fluid theory

Farnes' new theory says that 95 percent of the cosmos is made up of a "dark fluid," and dark matter and dark energy are effectively both "symptoms" of that underlying phenomenon. It does do a good job of describing both of those, although it requires a little number-fudging of its own.

This dark fluid would need to have negative mass. That alone sounds like a sci-fi concept – how can something have a mass of -1 kg? But according to Newtonian physics it's entirely possible, albeit still hypothetical.

Something that has negative mass would have some pretty weird characteristics. For one, forces are inverted, so if you were to push a ball with negative mass it would accelerate towards your hand, instead of away from it. That also means it exhibits a kind of negative gravity, which repels other material instead of attracting it.

If the cosmos is filled with dark fluid, its negative gravity would be pushing everything away from everything else – exactly the observed phenomenon that dark energy was invented to explain. Meanwhile, it's not the gravitational pull of a dark matter halo that's holding galaxies together – it's the negative "push" of the dark fluid surrounding them. Galaxies of regular matter are basically bubbles floating in a cosmological dark fluid.

Do negative masses even exist?

One of the main issues with the theory is that we don't yet know if negative masses exist. But, Farnes argues in the study, other physical forces all seem to be polarized, so why wouldn't mass also be positive and negative?

"For example, electric charges (+ and −), magnetic charges (N and S), and even quantum information (0 and 1) all appear to be fundamentally polarized phenomena," the paper reads. "It could therefore be perceived as odd that gravitational charges – conventionally called masses – appear to only consist of positive monopoles."

Lending more weight to the idea, other recent studies have managed to create fluids and particles that exhibit the properties of negative mass.

A matter of creation

Another problem with the theory is that as the universe expands, the dark fluid would thin out to the point that its effects are no longer seen. To counter that, Farnes introduces a "creation tensor" into his equations, which essentially suggests that this negative mass matter is constantly being created anew, keeping the dark fluid at a regular consistency over time.

That might sound a little too convenient, but the idea of matter creation has some precedent. It was part of the Steady State model, an early alternative to the Big Bang theory that has since been disproven observationally. But it was dealing with regular (or positive mass) matter – Farnes says negative mass matter might still behave that way.

"Previous approaches to combining dark energy and dark matter have attempted to modify Einstein's theory of general relativity, which has turned out to be incredibly challenging," says Farnes. "This new approach takes two old ideas that are known to be compatible with Einstein's theory – negative masses and matter creation – and combines them together. The outcome seems rather beautiful: dark energy and dark matter can be unified into a single substance, with both effects being simply explainable as positive mass matter surfing on a sea of negative masses."

If true, the dark fluid theory could explain why the ongoing hunt for dark matter particles has consistently come up empty-handed. Of course, there's every chance that Farnes is wrong, and the astrophysicist acknowledges that, but he hopes that it will at least get the scientific community discussing different ideas. To find evidence to back up the idea, Farnes plans to use the Square Kilometer Array (SKA) telescope to compare observations of the universe to predictions made by the dark fluid theory, including looking for signs that negative masses exist in the universe.

"There are still many theoretical issues and computational simulations to work through, and Lambda-CDM has a nearly 30 year head start, but I'm looking forward to seeing whether this new extended version of Lambda-CDM can accurately match other observational evidence of our cosmology," says Farnes. "If real, it would suggest that the missing 95 percent of the cosmos had an aesthetic solution: we had forgotten to include a simple minus sign."

The study was published in the journal Astronomy and Astrophysics.

Source: The Conversation, Oxford University via Phys.org

11 comments
amazed W1
Surely if mass and energy are essentially related, then it is perfectly logical to deduce that negative mass would be related to negative energy? And once you get back to energy then force fields due to plasma movements cannot be too far removed either? This suggests that we have to try to understand (positive) mass and energy far better than we do now before we can advance meaningfully into the concepts of the corresponding negatives.
guzmanchinky
How little we know. I would like to order a vehicle that uses dark fluid to repel gravity and creates thrust please.
joe35
I propose that gravity reverses and becomes repulsive at approximately 1.5 million light years. It becomes more and more strongly repulsive, reaches a peak, and then decreases trailing off to zero. This does away both with dark matter and also dark energy. It would explain why most galaxies are accelerating away from each other – leaving no need for cosmological expansion or dark energy. It also explains gravitational rotational rates without the need of dark matter. Galaxies are pushing dust and gas into the interstitial space between galaxies. This dust and gas means that each galaxy or small galaxy cluster is surrounded by a womb of material at a distance that repulsive gravity operates. This repulsive womb, along with the pressure from other galaxies, holds outer stars in place, explaining higher than expected rotation. You may read the justification for this theory here, along with responses to objections at the bottom: https://www.reddit.com/r/MyTheoryIs/comments/87pcgq/what_dark_matter_is/ I think that General Relativity can be adjusted such that we keep time dilation, BUT ditch curved or dilated space. I.e. we should work with flat, 3D , Euclidean space + time dilation. I explain about this in the notes at the bottom of the article.
Cryptonoetic
So has Einstein suddenly become passe? 'Positive' masses do not attract each other. Rather, they are attracted 'to' each other via their deformation of space-time geometry caused by their respective mass. 'Negative' mass implies negative space-time which, as a closed-curve geometry, obviates the possibility of us ever directly observing such a phenomenon. 'Dark energy' isn't an energy at all. A more correct reference would be to interpret the observation of increasing rate of expansion over time as us (i.e., the present) accelerating away from more distant objects (distant past), not the distant objects accelerating away from us. The increasing rate of expansion is a consequence of the (thermodynamic law of) conservation of space-time. As matter is converted into energy, space-time expands accordingly. The ratio of space-time to matter is huge, thus the apparent magnitude of expansion observed.
Douglas Bennett Rogers
Gravitational lensing and, now, gravitational waves are in common use and require spacetime curvature.
MichaelShortland
The aether anybody??
Mzungu_Mkubwa
The recently proposed theory(s) regarding the possibility that the speed of light is not really a constant, but possibly has changed over the eons time, has the potential to account for all the gaps that have been filled in by the "darks". I, for one, certainly don't think its out of the realm of possibility that the speed of light has not been precisely the same from the very beginning... but this notion seems to throw many into a tizzy of sacrilege!
Nik
So, hypothetical matter, hypothetical energy, and a hypothetical fluid! All this to explain unseen forces affecting the movement of the matter in the universe..... If you saw a steel washer, sliding around on the table, would you inspect the hole in the middle for its motive force? Unlikely. The average person would look under the table for a large magnet being moved around. Another more believable, perhaps, and logical hypothesis for the anomalies observed in the motions of the matter in the universe could be;... Astronomical observations have shown that black holes had already formed 800 million years after the 'big bang'. Those black holes would, after some 12 billion + years be on the periphery of our universe, would have absorbed all their accretion disks, and would therefore be completely invisible. Also, they would, by now, exist in their trillions upon trillions. So our universe would be encased in a 'shell' of these trillions upon trillions of black holes. Their combined gravitational forces would have noticeable effects upon all the matter within this shell. In addition, all the matter would be attracted by this shell, hence the accelerating expansion of our universe. Eventually all the matter of the universe would become black holes, and as they would all attract one another, the universe would then start contracting, finally ending in the hypothetical, 'big crunch.' This 'crunch' would be of such violence, that enormous energies would be released, resulting in another 'Big Bang.' ('And so on ad infinitum')
sjbauer
This ground breaking book is set to be presented at the 2019 Association of College and Research Libraries (ACRL) conference in Cleveland, OH, from April 10th to 13th, 2019.
RobertTaylor
@NIK, yes!!!!!!!!!!!!! That is what I have been thinking for some time. The problem with the big bang theory is EVERYTHING DOES NOT COME FROM NOTHING. The big bang theory is the 2nd half of a theory missing the first half. The black hole. The black hole is the front door and the big bang is the back door OF THE SAME THING. So we do have a pulsing universe.