The expansion of the universe could be a mirage, new theoretical study suggests
New research looking at the cosmological constant problem suggests the expansion of the universe could be an illusion.
The expansion of the universe could be a mirage, a potentially controversial new study suggests.
This rethinking of the cosmos also suggests solutions for the puzzles of dark energy and dark matter, which scientists believe account for around 95% of the total energy and matter in the universe but remain shrouded in mystery.
The novel new approach is detailed in a paper published June 2 in the journal Classical and Quantum Gravity, by University of Geneva professor of theoretical physics Lucas Lombriser.
Related: Our expanding universe: Age, history & other facts
Scientists know the universe is expanding because of redshift, the stretching of light's wavelength towards the redder end of the spectrum as the object emitting it moves away from us. Distant galaxies have a higher redshift than those nearer to us, suggesting those galaxies are moving ever further from Earth.
More recently, scientists have found evidence that the universe's expansion isn't fixed, but is actually accelerating faster and faster. This accelerating expansion is captured by a term known as the cosmological constant, or lambda.
The cosmological constant has been a headache for cosmologists because predictions of its value made by particle physics differ from actual observations by 120 orders of magnitude. The cosmological constant has therefore been described as "the worst prediction in the history of physics."
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Cosmologists often try to resolve the discrepancy between the different values of lambda by proposing new particles or physical forces but Lombriser tackles it by reconceptualizing what's already there.
"In this work, we put on a new pair of glasses to look at the cosmos and its unsolved puzzles by performing a mathematical transformation of the physical laws that govern it," Lombriser told Live Science via email.
In Lombriser's mathematical interpretation, the universe isn't expanding but is flat and static, as Einstein once believed. The effects we observe that point to expansion are instead explained by the evolution of the masses of particles — such as protons and electrons — over time.
In this picture, these particles arise from a field that permeates spacetime. The cosmological constant is set by the field's mass and because this field fluctuates, the masses of the particles it gives birth to also fluctuate. The cosmological constant still varies with time, but in this model that variation is due to changing particle mass over time, not the expansion of the universe.
In the model, these field fluctuations result in larger redshifts for distant galaxy clusters than traditional cosmological models predict. And so, the cosmological constant remains true to the model's predictions.
"I was surprised that the cosmological constant problem simply seems to disappear in this new perspective on the cosmos," Lombriser said.
A recipe for the dark universe
Lombriser's new framework also tackles some of cosmology's other pressing problems, including the nature of dark matter. This invisible material outnumbers ordinary matter particles by a ratio of 5 to 1, but remains mysterious because it doesn't interact with light.
Lombriser suggested that fluctuations in the field could also behave like a socalled axion field, with axions being hypothetical particles that are one of the suggested candidates for dark matter.
These fluctuations could also do away with dark energy, the hypothetical force stretching the fabric of space and thus driving galaxies apart faster and faster. In this model, the effect of dark energy, according to Lombriser, would be explained by particle masses taking a different evolutionary path at later times in the universe.
In this picture "there is, in principle, no need for dark energy," Lombriser added.
Postdoctoral researcher at the Universidad ECCI, Bogotá, Colombia, Luz Ángela García, was impressed with Lombriser's new interpretation and how many problems it resolves.
"The paper is pretty interesting, and it provides an unusual outcome for multiple problems in cosmology," García, who was not involved in the research, told Live Science. "The theory provides an outlet for the current tensions in cosmology."
However, García urged caution in assessing the paper's findings, saying it contains elements in its theoretical model that likely can't be tested observationally, at least in the near future.
Originally published on LiveScience.com.
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Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.

rod After reading this article and 29page PDF cited, I ask, is the Big Bang model ready to be thrown out? :)Reply
Ref  Cosmology in Minkowski space, https://iopscience.iop.org/article/10.1088/13616382/acdb41, 02June2023.
My note, from the 29page PDF report cited, from the introduction. “This article explores the implications of casting cosmology into different spacetime geometries as a simple mathematical manipulation that leaves physical measurements unaffected but can reveal new physical insights. Clearly, the Minkowski spacetime occupies a special place among the metrics one can transform the cosmic geometry into, being static and flat as well as the spacetime of special relativity and quantum field theory or indeed of the entire Standard Model. Hence, a particular focus is put on casting cosmology into Minkowski space. “3.1.2 Redshift Importantly, as shown in the following, despite the static geometry of the Universe in Sec. 3.1.1, cosmological observations are still redshifted. However, rather than due to the expanding space, redshift is caused here by evolving particle masses (also see Ref. ).”
My thought. Plenty here to chew on for the Big Bang. CMB is referenced 10x and inflation, 15x in the paper. It seems that GR math can be used to explain much in cosmology without an expanding universe model used 😊 The points in “6 Conclusion” are interesting reading, example: “(1) Rather than due to an expanding Cosmos, observed redshifts to distant galaxies can be interpreted as the evolution of particle masses after conformal transformation of the FLRW metric into static or Minkowski space. This recovers the Friedmann equations and the evolution of energy densities, and importantly, leaves measurements such as redshifts invariant.” “(7) Finally, the presence of conformal inhomogeneities in our Universe can offer a simultaneous solution to the Hubble tension, the discrepant measurements in the amplitude of matter fluctuations as well as the preference for a nonstandard lensing amplitude in CMB anisotropies, provided we are located in an underdense conformal region of space. Conformal inhomogeneities can furthermore enhance redshifts to distant galaxies, causing larger distances and older ages to be attributed to galaxies in clusters and consequently larger masses and population sizes than otherwise expected for those. Another effect is a mass bias for the inferred masses of galaxy clusters, where masses inferred from lensing are larger than those inferred dynamically or kinematically. It is worth highlighting that these predictions agree qualitatively with trends identified in current observations and may thus be worthwhile further investigating.” My note, if we use this new cosmology model, it seems the cosmology calculators based upon FLRW metric would not provide reliable distances for objects showing look back or lighttime distances or comoving radial distances as measured from Earth. Such distance measurements, energies claimed, and masses, would be *inflated* 😊 
Ryan F. Mercer rod said:After reading this article and 29page PDF cited, I ask, is the Big Bang model ready to be thrown out? :)
Nope, most definitely not. While it makes for some interesting conjecture, that's all it is, and as the article states, it can't be empirically proven through experimentation. So as it stands, inflation still has a lot more data supporting it. Nothing about this theory disapproves any of it, it just offers a possible alternative, without any proof. Sorry, but even clever ideas have to disprove the accepted ones in order to be relevant. Furthermore, it is my experience that those most excited about any theory that questions inflation are typically overzealous pseudoscience fan boys with little to no expertise and zero credibility. Good science isn't about over hyping an idea that deep down you really really want to be true. That's not how discovery typically works. Just say'n. 
rod Ryan F. Mercer comments in post #3 opens the door here for much :) The 29page PDF does briefly discuss testing. "This multitude of possibilities motivates generally testing, across the vast spacetime, for phenomenological variations in the effective time, length and mass scales of the observed behaviour of different matter species as in Eq. (48), or likewise in the fundamental couplings. Note in this context that while the Minkowskian picture is physically equivalent to the standard cosmological picture both at the classical and quantum level and observationally indistinguishable from it, it offers a different basis for theoreticalReply
extensions. These may appear more natural in one picture over the other and if verified, could
favour one framework over the other."
The space.com article near end does state: "The paper is pretty interesting, and it provides an unusual outcome for multiple problems in cosmology," García, who was not involved in the research, told Live Science. "The theory provides an outlet for the current tensions in cosmology." However, García urged caution in assessing the paper's findings, saying it contains elements in its theoretical model that likely can't be tested observationally, at least in the near future."
There are many discussions on the space.com forums about BB cosmology and inflation. Here is an example where BB model violates the conservation law of energy, Lawrence Krauss acknowledged this back in a 2012 book. https://forums.space.com/threads/whythecurrentmodeloftheuniversebreaksafundamentallawthatenergycannotbecreatednordestroyed.61360/
Just my simple observation. If the redshifts seen in astronomy turn out to have an alternative explanation, the Big Bang will be in real trouble, including distance measurements for billions of light years and outcomes. Even inflation theory requires the existence of exotic objects like the inflaton, including producing many other exotic particles like magnetic monopoles that flood the expanding universe in the early period, Alan Guth writings and some from 1984 in Scientific American. 
EricLerner Good that you covered the theoretical paper on the nonexpansion of the universe. But your readers should know there is great observational evidence against expansion and the Big Bang hypothesis. Observations are the key test, after all, of scientific validity. See here: Monthly Notices of the Royal Astronomical Society, 477, 3185, 2018Reply
Also here: DOI: 10.13140/RG.2.2.21108.63366
And here: 10.13140/RG.2.2.26141.79844
As these papers detail expansionhypothesis predictions are contradicted by 16 sets of observational data and are only confirmed by one, deuterium abundance. I challenge anyone to find more examples of expansion/Big Bang predictions that are quantitatively confirmed by subsequent observations.
JWST has made this a lot worse for expansion. We have not yet published on this, but see the video series starting here: https://youtu.be/360aZiIWdjQ 
Helio The basis to this math model requires mass fluctuations....Reply
"The effects we observe that point to expansion are instead explained by the evolution of the masses of particles — such as protons and electrons — over time.
In this picture, these particles arise from a field that permeates spacetime. The cosmological constant is set by the field's mass and because this field fluctuates, the masses of the particles it gives birth to also fluctuate. The cosmological constant still varies with time, but in this model that variation is due to changing particle mass over time, not the expansion of the universe. "
As Steve Martin would comically quip on "How to make a million dollars: First, get a million dollars."
What science supports an isotropic evolving mass fluctuation? This might be fine in math, but where's the physics?
It is interesting that they seem to claim that the universe is static but exhibits redshift. This isn't as silly as it might sound, admittedly. DeSitter's original GR model was of a static universe that demonstrated redshift, but his model had no mass in the universe to make this work.
Where is the science that support mass "evolution"? How many separate lines of evidence argue this model?
The article's claim that we know of expansion because of redshift, is incomplete. The time dilation found in Type 1a SN makes a strong case for expansion. Then there are a dozen more lines of evidence including the powerful CMBR. How does this model explain the CMBR, which was a prediction of BBT due explicitly to expansion. 
rod
The reference 'Observations contradict galaxy size and surface brightness predictions that are based on the expanding universe hypothesis', "...the angular radius of an object in a nonexpanding universe declines with redshift, while in an expanding universe this radius increases for redshifts z > 1.25."EricLerner said:Good that you covered the theoretical paper on the nonexpansion of the universe. But your readers should know there is great observational evidence against expansion and the Big Bang hypothesis. Observations are the key test, after all, of scientific validity. See here: Monthly Notices of the Royal Astronomical Society, 477, 3185, 2018
Also here: DOI: 10.13140/RG.2.2.21108.63366
And here: 10.13140/RG.2.2.26141.79844
As these papers detail expansionhypothesis predictions are contradicted by 16 sets of observational data and are only confirmed by one, deuterium abundance. I challenge anyone to find more examples of expansion/Big Bang predictions that are quantitatively confirmed by subsequent observations.
JWST has made this a lot worse for expansion. We have not yet published on this, but see the video series starting here: 360aZiIWdjQView: https://youtu.be/360aZiIWdjQ
Interesting here. Angular sizes of various objects with their redshifts, it would seem galaxy sizes in arcminutes and arcsecond will get smaller and smaller as their distances from Earth increases using redshift expansion math from GR, e.g. cosmology calculators. Example, 1 arcsecond at 4 x 10^9 pc from Earth = 4 x 10^9 AU diameter or 63250 LY. Using cosmology calculators, when z=1.4 or larger, space expands faster than c velocity and comoving radial distances, objects cannot be seen on Earth today, thus any angular size measurements apparently cannot be made. 
EricLerner No, if you look at cosmology calculators like New Wright's it gives angular dimensions at any redshift. JWST is measuring angular radii at confirmed redshifts up to around 12.Reply 
rod
I use Ned Wright calculator, https://lambda.gsfc.nasa.gov/toolbox/calculators.htmlEricLerner said:No, if you look at cosmology calculators like New Wright's it gives angular dimensions at any redshift. JWST is measuring angular radii at confirmed redshifts up to around 12.
and others too like, https://www.kempner.net/cosmic.php
The calculators show the angular size for the z value and H0 value used too. As far as I understand, the angular size distance is not the physical size of a galaxy like at redshift 12, otherwise a galaxy would be some 2.5 billion light years across. I believe this is the Universe size at z and we have the age of the Universe at z too including light time or look back time distance and the comoving radial distance where the galaxy should be today if it could be visible from Earth. Space will expand faster than c velocity for all redshifts of 1.4 or larger, Ned Wright calculator and others will show this using the comoving radial distances. If I use Ned Wright with z=1100 for the CMBR postulated redshift and H0 = 69 km/s/Mpc, the angular size distance is a bit more than 41 million light years, thus the size of the Universe or at least radius when the CMBR appears as light. Thus, when z=1100, angular size distance a bit more than 41 Mly for the Universe and at z=12.0, angular size distance a bit more than 2.5 Gly. This shows the expanding Universe size I believe for the redshift values used. 
EricLerner No that is not what angular size distance is defined as. It is the distance in nonexpanding space that an object should be at to have the same angular size that an object in an expanding universe actually has at that redshift. Look at the scale. For example at z=10 and the default parameters the scale is 4.2 kpc per arc secondso a galaxy 4.2 kpc in radius would have and angular radius of 1 arcsec. This of course is the predction. Observations show that galxy size are much smaller than predicted by expansion, but just right for nonexpansion.Reply 
rod
Thanks, I see this now using the calculator like Ned Wright. "This gives a scale of 4.255 kpc/" and the other I listed. I am surprised I do not see much discussion or reporting on this issue concerning BB cosmology as well as the very large comoving radial distances where space expands much faster than c velocity.EricLerner said:No that is not what angular size distance is defined as. It is the distance in nonexpanding space that an object should be at to have the same angular size that an object in an expanding universe actually has at that redshift. Look at the scale. For example at z=10 and the default parameters the scale is 4.2 kpc per arc secondso a galaxy 4.2 kpc in radius would have and angular radius of 1 arcsec. This of course is the predction. Observations show that galxy size are much smaller than predicted by expansion, but just right for nonexpansion.