German researchers at the University of Bremen, together with Romanian colleagues at the University of Brașov, have proposed a theory suggesting that “dark energy” might not be a separate, mysterious substance at all.
Dark energy is usually invoked to explain why the universe is expanding at an ever‑increasing rate. In this new approach, however, the team uses an extended form of Einstein’s theory (known as Finsler gravity) to show that cosmic acceleration could arise naturally from gravity itself. In their view, the very geometry of spacetime may be responsible for the universe’s speed‑up.
The researchers’ approach modifies the mathematical foundation of cosmology. In the traditional Einstein-Friedmann model, cosmic acceleration cannot occur without inserting an additional term representing dark energy. But when the team replaced general relativity with Finsler gravity, the modified Finsler-Friedmann equations naturally predicted an accelerating universe, even in the absence of dark energy.
That’s a real breakthrough. I had tried Ainsler, Binsler, Cinsler, Dinsler, and Einsler gravities and got nowhere.
It’s about dark energy. According to Wikipedia, “The term “dark energy” was coined by cosmologist Michael S. Turner in 1998 for a paper written with Saul Perlmutter and Martin White.”
Not quite a century.
The group of German and Romanian scientists mentioned in the article are working on the mystery of accelerating expansion of the universe. The accelerating expansion of the universe has been one of the toughest mysteries for about a quarter of a century.
Observations of distant supernovae in the late 1990s revealed that the cosmos is expanding at an increasing rate. To account for this unexpected behavior, physicists introduced the concept of dark energy. They said dark energy makes up about 70% of the universe. But dark energy is in fact just a hypothetical, invisible force.
The scientists in the article propose an alternative. They argue that the universe’s accelerating expansion may not require dark energy at all. Instead, they suggest that the effect could arise naturally from an extended version of Einstein’s general theory of relativity.
Einstein’s theory describes gravity not as a force but as the curvature of spacetime. It successfully explains a wide range of astronomical phenomena. However, the discovery of cosmic acceleration forced scientists to introduce dark energy as a kind of “patch” to preserve the standard model of cosmology.
The new research challenges this necessity. According to the authors, acceleration can emerge naturally from Einstein’s equations if the geometric structure of spacetime is enriched (without adding any exotic energy component).
Reports indicate that the researchers tested their extended‑gravity equations using cosmological models and found that their approach can reproduce the observed expansion history. Their model appears to fit the available data.
ETA: This is different from earlier attempts. Earlier attemps to modify gravity introduced new fields (scalar-tensor theories), added new particles (massive gravity) or required fine tuning.
Right - the cosmological constant, which Einstein invented to stabilize the universe (which, in fact, wouldn’t work to do that) provides an explanation for an accelerating universe
Einstein’s cosmological constant is just a symbol. It does not offer any hints regarding the physical nature of the “force” behind the observed acceleration. What scientists have been working on for about 25 years is to clarify the physical cause of this acceleration. The scientists mentioned in the article mentioned above claim there may be no “force,” and in fact the geometric structure of spacetime could be responsible for this phenonmenon. They’re not modifying Einstein’s calculations; they’re applying them to a different geometry of spacetime.
The absolute best case here is that these guys somehow managed to learn general relativity without ever learning the history of it, and independently realized that there was room for a constant of integration in the field equations and that that would have the same behavior as what’s now called dark energy. Sort of like that guy a few years back who made the “revolutionary discovery” of the trapezoid method for approximating integrals. The most likely case is that this is just crackpot word salad that coincidentally happens to resemble something real. The next most likely case is that they’re scammers. The absolutely impossible case is that this is some revolutionary new discovery, because everyone already knew about it for ages.
Sarcasm and contempt are almost never effective at reducing ignorance.
Skepticism is fair, of course. Whenever someone claims they have reinvented the wheel (or tepid water, as people in my milieu often say), we should probably treat them with suspicion.
But treating the article in the OP with sarcasm and contempt is too much. Yes, the basic idea that Einstein’s equations allow a constant of integration is not new. Scientists know that this constant behaves like dark energy.
The article mentioned in the OP is the summary of a technical paper. It is typical for this type of summary or paper to oversell itself. We know that even if it is some honest work, it’s just a simple reinterpretation or an extension of an existing theory. But that doesn’t make those people scammers or crackpots.
Besides, modified-gravity models, emergent-gravity ideas, and geometric approaches to cosmic acceleration are active ideas. They don’t replace the standard model, but they’re legitimate lines of inquiry. Dismissing someone’s work with so much sarcasm and contempt (and without looking at the actual paper) is unfair, in my opinion.
You don’t understand. Something that behaves like GR, in the ways that it’s observed to behave, but which also has something in the field equations that acts like dark energy, must just be the cosmological constant. There’s no other mathematical possibility.
The article was published in The Journal of Cosmology and Astroparticle Physics, an “online-only peer-reviewed scientific journal”. It’s listed as one of seven “Flagship” journals in the field by another paper. Possibly wrong, probably not by crackpots.
So, there’s a new theoretical paper suggesting that the mismatch between predicted and observed cosmic expansion might be explained if space itself behaves like a viscous, sticky fluid. This paper is currently in preprint and hasn’t been peer-reviewed yet. The idea is highly speculative, but here it is anyway:
The standard model of cosmology assumes that dark energy is a constant, unchanging force driving the accelerating expansion of the universe. But recent data from the DESI project shows that galaxies aren’t expanding exactly as this model predicts. There’s a small but persistent difference.
Researcher Muhammad Ghulam Khuwajah Khan proposes that the vacuum of space has bulk viscosity. This is described as a kind of resistance to expansion, similar to how honey resists being stretched more than water does.
To explain this, he introduces the idea of spatial phonons. In solids, phonons are collective vibrations of atoms. Khan applies this concept to space itself, suggesting that the vacuum might support longitudinal vibrations, like sound waves. These vibrations would create a viscous effect, which can slow expansion just enough to match DESI’s observations.
If Khan’s theory is true, this would imply that space isn’t a perfect, frictionless void. Dark energy might not be constant after all and the standard cosmological model may be incomplete.
The standard model of the universe assumes a smooth vacuum, predictable expansion, and well‑behaved dark energy. This model no longer matches observations. Two independent ways of measuring the universe’s expansion rate now disagree so sharply that researchers say the model may be fundamentally flawed.
The final results from the Atacama Cosmology Telescope delivered a major blow. This telescope ruled out about 30 previously viable versions of how the universe might have evolved. These versions were attempts to reconcile early‑universe measurements with local ones.
These results suggest that space is not as uniform as the standard model assumes. Also, the expansion history is more complex than a simple interplay between matter and smooth dark energy. It seems that something about the vacuum itself is behaving in an unexpected way.
The article’s central idea is that the vacuum might not be empty at all. Instead, it may behave like a viscous and shape-shifting medium. It acts like a substance that resists stretching or flowing.
If this theory is true, then space must have hidden physical properties. These properties only become visible at extremely high precision. The present equations describing cosmic expansion are missing a key ingredient.
OK, that one, I don’t know anything about. Referring to a property of spacetime as “viscosity” is a strained enough analogy that it’s difficult to say off the cuff what they’re describing.
To be clear, there’s a lot that we don’t know about cosmology, and especially about the “dark energy”, or whatever it is. There’s been talk for a long time that the dark energy might vary with time, for instance. If it does, it’s a small enough variation that it’s difficult to detect, but the idea has mostly just been rejected on the grounds of Occam’s razor and insufficient evidence, not on any sort of theoretical grounds (because we don’t have enough theoretical understanding to be able to reject it on theoretical grounds).
