16 ms·

New Evidence Against the Standard Model of Cosmology

196 points by nsoonhui 5y ago

JetSetWilly 5y ago
> Two years ago, I told you about a paper by Subir Sarkar and his colleagues, that showed if one analyses the supernovae data correctly, without assuming that the cosmological principle holds on too short distances, then the evidence for dark energy disappears. That paper has been almost entirely ignored by other scientists. Is this a case of science advancing one funeral at a time? We have to wait for the dark energy "establishment" do die off?
- rich_sasha 5y ago
  There is more evidence for dark energy. Discrepancies in redshift vs distance are just one, and there are interestingly also other explanations for it. IIRC in lambda-CDM, if you don’t have dark energy, the whole universe just looks very different, eg the structures of galaxies, groups and supergroups etc are not the same. It might still be wrong, but more nails are needed for this coffin.
  - The_rationalist 5y ago
    MOND lead to less paradoxes/mispredictions than dark matter/energy
  - whatshisface 5y ago
    One thing that can happen when you are doing computer modeling to find the input parameters that explain your observations is getting stuck in a local maximum. I am absolutely ready to believe that eliminating dark energy from current models makes their results look less like the real universe, but the number of re-runs that would be required to sample the entire parameter space and demonstrate that there were no other parameterizations that looked like our universe would be enormous, and if you include the possibility of new theories, infinite. There would either have to be some kind of theoretical reason to think that the best known parameterization of a simulated lambda-CDM universe is not merely a local maximum, or the parameters would have to be well-constrained, by observations, so that the free parameter space was small enough to exhaustively explore. I am not aware of either condition being true so I will express some skepticism about the conclusions from the models. Nonetheless, my lack of knowledge about those conditions is not very strong evidence for their absence, and I know there could be someone reading this and feeling very annoyed that I don't know about the Backhausen-Thule principle, or whatever piece completes this puzzle. (Your contribution to the discussion, oh annoyed reader, would be greatly appreciated.)
  - michelpp 5y ago
    Sarkar addresses this other evidence in this interview: https://youtu.be/JJzU9hDjiRk?t=819 https://youtu.be/JJzU9hDjiRk?t=819 In summary, there is a strong selection bias in cosmology toward the standard model which induces "predictions" that confirm themselves. One bit of evidence he presents, dozens of studies were found to be within one sigma of the wmap measurement and not naturally distributed as one would expect.
  - raattgift 5y ago
    The value for \Lambda, the cosmological constant, is tiny and positive. It's so tiny that as we take it to zero, the universe is still filled with clusters spiral and elliptical galaxies with a strong solid-angle-on-the-sky/brightness/redshift relation, and those galaxies filled with the same sorts of stars we see in the sky. Indeed the evidence available prior to 1998 or so favoured a \Lambda of zero, and the early evidence favouring a tiny positive value was very much a surprise. The Hubble Space telescope had already been running and taking deep views for several years. COBE (https://science.nasa.gov/missions/cobe https://science.nasa.gov/missions/cobe) and the Saskatoon experiment had already finished. None presaged the results of the Supernova Cosmology Project and High-Z Supernova Search Team. Follow-ons by Hubble (and others) and successors to COBE support the accelerated expansion. The physical interpretation of the zero versus the tiny positive value is that in the former there was a last early acceleration which ended essentially all at once, with galaxy clusters then moving purely inertially; or alternatively there was an early acceleration which decayed, possibly in several steps, into a tiny persisting constant acceleration well before the formation of the surface of last scattering (the observed cosmic microwave background). Or alternatively there were mutiple sources of acceleration, one very large and which ceased early, and one which has been always-a-small constant. There are different lines of evidence for how this residual acceleration has evolved. Practically all of it favours it settling down into one constant tiny value in the very early universe, and that the value can be determined with ever greater precision mostly by studying the fine detail in the cosmic microwave background and the various observables of highly red, dim, low-angular-diameter galaxies backlit by quasars and internally lit both by quasars and supernovae. The exact value is a matter of active research, as some of the data is conflicting. None of the data disfavours some ongoing acceleration, and the conflict is generally within 10%. As an example of the physical consequences of the discrepency, the lower value means we can see more galaxies (and more galaxies will be able to see the light from the Crab supernova and other historical galactic supernovae), while the higher value fewer galaxies we can see and a lot fewer galaxies who could see a recent supernova within the Milky Way. There are also various ideas that the tiny value of \Lambda is not constant but continues to evolve. Most of these unfailingly generate observables consistent with a new non-vanishing long-range force to accompany electromagnetism and gravitation, and such an extra ("fifth") force is almost wholly ruled out by evidence. Some store up this fifth force's energy until local matter-energy density is very low (trillions of trillions of years in our future) and unhide it then at various powers (often very high, in an essentially global phase change). Attempts to remove ongoing acceleration altogether by setting \Lambda to zero seem somewhat contrived. A typical approach is to assume that the universe is much less homogeneous than it appears, and that we are being mislead by being in a highly unusual place exceptionally close to the centre of a large matter underdensity. This was of interest to several teams of theoreticians (Clifton, February) around 2008-2009, as they developed specific models -- within general relativity as the theory of gravitation -- in order to try to distinguish whole families of such models from the standard cosmology rather than outright advocating for those models in preference to the standard cosmology. More broadly, this is related to cosmologies that are wildly inhomogeneous at large scales compared to the standard cosmology, such that in some greater-than-galaxy-sized regions of spacetime the matter is much older than in others (in Wiltshire's voids, and in dense areas close to their boundaries, clocks run a lot more quickly so observers will see outside-the-void matter as gravitationally (collapse) rather than cosmologically (accelerated expansion) redshifted). Some of these models are designed to explore how one can generate an averaging procedure for general curved spacetimes, or at least for "lumpy" 3+1-dimensional ones, rather than to really challenge the most general form of the Copernican principle (i.e., they don't really want to put Earth pretty much at the centre of the universe). Motivations do vary though; there are some productive everyday cosmologists whose single-author papers occasionally develop alternatives to the standard cosmology that fit closer to some scripture or other. There are also some modified gravity proponents (some of whom work every day with the standard cosmology) whose theories of gravitation "need help" from a favourable distribution of matter that picks out the region around us as atypical.
- avereveard 5y ago
  > without assuming that the cosmological principle holds on too short distances There's still the problem of colliding galaxies showing a weakly interacting centroid that's shifted compared to the masses but interacts with the visible masses. If truly are variation in the local constants, then one has to explain why these variations shows inertia, at such point it starts looking more and more like matter
  - mdturnerphys 5y ago
    That is evidence for dark matter, not dark energy.
  - Ericson2314 5y ago
    That's about dark matter, this was about dark energy.
- The_rationalist 5y ago
  Is this related to MOND?
- Svoka 5y ago
  That would be true if young scientists wouldn’t continuously make successful predictions based on cosmological principle among other observable effects of the general relativity and standard model. Make observable prediction, coherent thesis, then we’ll talk. Of course our models are not perfect, but it is best we have. Physics so far never dealt in “fundamental truths”, just good enough models. So far, this is best we got.
  - zeven7 5y ago
    I'd argue that Einstein in particular cared a lot about "fundamental truths". Not everyone can be Einstein, but I'm glad some people care about asking deeper questions.
    - kkylin 5y ago
      I don't disagree with your point, but do want to add that not publishing on "fundamental truths" isn't the same as not asking those questions. Not everyone's going to have something novel, plausible, and fundamental to say on a regular basis, hence most publications (even if everyone's asking these questions, which granted they're probably not) are going to be much more incremental.
    - rich_sasha 5y ago
      Ironically, it was Einstein who introduced the “cosmological constant” (and thus indirectly dark energy). I think later in life he called it a glorified fudge factor and his biggest regret.
      - raattgift 5y ago
        Wikipedia covers this sufficiently at https://en.wikipedia.org/wiki/Cosmological_constant#Sequence_of_events_1915%E2%80%931998 https://en.wikipedia.org/wiki/Cosmological_constant#Sequence... The five-line tl;dr: non-expanding cosmologies with no big bang but lots of galaxies tend to collapse in finite time. One can avoid collapse with a positive cosmological constant. That approach predated the work of Hubble (expansion) and Lemaître (big bang). Expanding cosmologies with a sufficiently large initial big bang do not need a cosmological constant to keep expanding forever. Einstein, not being stupid, recognized that and carried on. Since 1998: an accelerating expanding universe is inconsistent with just a single big bang as impulse, but is consistent with a small positive cosmological constant. Einstein and Schrödinger certainly discussed whether to treat the cosmological constant as an energy entering into the right hand side of the Einstein Field Equations instead of a multiplier on the metric in the left hand side: [Harvey 2012] https://arxiv.org/abs/1211.6338 https://arxiv.org/abs/1211.6338 Their conclusion is that choice of side is principally a matter of aesthetics, and that remains true today. Harvey2012 §5 is a good reminder not to put too much weight into the early days of general relativity. Exact solutions were few and simple but still extraordinarily hard to work with by hand. Numerical approaches didn't exist, nor did formalisms that provide post-Newtonian approximations that are more tractable. Realistic distributions of matter were largely as-yet undiscovered (compare 1917 introduction of cosmological constant and low estimates of the number of spiral galaxies in the sky, their mass, and the light-travel distance to them: https://en.wikipedia.org/wiki/Great_Debate_(astronomy) https://en.wikipedia.org/wiki/Great_Debate_(astronomy) which came later). Einstein's adaptation to the flood of astronomical discoveries during his productive lifetime is part of what made him Einstein rather than any less celebrated figure.
- neuronic 5y ago
  Of course. Science is just a chase for grant money. Lots of entertainment money to be earned and documentaries can be made about "dark energy". Knowledge discovery is secondary or tertiary to modern science. The field is full of greedy egomaniacs, leaving the honest scientists at a competitive disadvantage. It's about reputation and $$$.
- analog31 5y ago
  I think this is an aside to what you're asking, but "science advances one funeral at a time" was a clever slogan and not an empirically tested hypothesis.
  - garmaine 5y ago
    It’s not meant to be an empirically testable hypotheses though.
- zeofig 5y ago
  No. That's a meme.
rich_sasha 5y ago
Not knowing much about the subject: cosmological principle appears to say that laws of physics are uniform in space. Then, with known matter and forces, this leads to some structure, with fluctuations, and hence some scale over which matter is uniformly distributed. If we calculate such a scale and find matter is still not uniform at that scale, wouldn’t the first conclusion be that there are missing terms in either matter or interactions (or both)? Rather than saying that laws of physics are not space-homogeneous. The article itself states that the length scale where the c10l principle kicks in is derived from a particular model for matter and interactions (lambda CDM). I think there is plenty of discrepancies between standard model and observations (most of them small). We don’t know what dark matter is, either. So to me the interesting point wouldn’t be, is the model wrong, but how is it wrong?
- ianai 5y ago
  Per Sabine H on YouTube ( https://youtu.be/JETGS64kTys https://youtu.be/JETGS64kTys ), the cosmological constant might be smaller than called for in current cosmology. That would agree with some other observations.
- deleted 5y ago
  [deleted]
- evgen 5y ago
  > the c10l principle Don't do this. It is bad enough that every major devops/infra component needs to create some <letter><number_of_missing_letters><letter> tag, but dropping it in to random places is worse than the regular backronyms and cute project names science and tech people use to try to hide complexity. It just adds confusion for no rhyme or reason other than trying to sound like you are a part of some club of insiders.
  - beeboop 5y ago
    You see it everywhere really. Military and politicians and government orgs all do it to embarrassing lengths too
drran 5y ago
n 2004, New Scientist, published an open letter from Eric Lerner and about 30 other scientists,[1] criticizing the Big Bang theory, and noting that Big Bang theory requires Dark Matter to exists. «Without some kind of dark matter, unlike any that we have observed on Earth despite 20 years of experiments, big-bang theory makes contradictory predictions for the density of matter in the universe. Inflation requires a density 20 times larger than that implied by big bang nucleosynthesis, the theory’s explanation of the origin of the light elements. And without dark energy, the theory predicts that the universe is only about 8 billion years old, which is billions of years younger than the age of many stars in our galaxy.» Can we finally abandon Big Shrink (BS) theory? It's obvious now that Oort cloud of Shapley attractor just collided with Dipole Repeller cloud [2]. [1]: https://www.plasma-universe.com/an-open-letter-to-the-scientific-community/ https://www.plasma-universe.com/an-open-letter-to-the-scient... [2]: https://vimeo.com/189355968 https://vimeo.com/189355968
sahil50 5y ago
Another problem with the standard model is attributing the cosmological redshift to the Doppler effect.
- FridayoLeary 5y ago
  could you pls elaborate on that?
  - JPLeRouzic 5y ago
    sahil50 posted this 2 months ago: https://colab.research.google.com/drive/1K1qoUFvqZp1fWbpcKJWq63nflgwS0ZHh?usp=sharing https://colab.research.google.com/drive/1K1qoUFvqZp1fWbpcKJW...
  - andyjohnson0 5y ago
    I'm not the parent commenter, and I'm not a physicist, but this might be a reference to the non-mainstream theories that are often grouped under the heading of "plasma cosmology". https://en.m.wikipedia.org/wiki/Plasma_cosmology https://en.m.wikipedia.org/wiki/Plasma_cosmology
  - sahil50 5y ago
    What Hubble objectively measured wasn't galaxies receding. He measured redshift. Or photon energy loss. And there's another way to explain this, that is simpler, self-consistent, and doesn't require the concept of "inflation" where apparently space expanded faster than the speed of light. The explanation: photon hubbling, tired light. That galaxies are frankly right where they are. They're not receding. The photon loses energy. It costs energy to forge a path through spacetime.
    - naasking 5y ago
      "Tired light" has failed other tests, so it's probably not the answer.
      - sahil50 5y ago
sahil50 5y ago
(1/H * c) = (1/α * ke^2 / (electron mass * c^2)) * (h / (proton mass * c * pi/2)) / (2G * proton mass / c^2)
- mkl 5y ago
  What does that mean in this context? How does it relate to the cosmological principle in the article?
  - sahil50 5y ago
    Hubble's constant is related to all the other fundamental constants. And is not a measure of "expansion", which is one of the core ideas of the Standard Model. Relation to the cosmological principle: self-similarity not just in terms of density and homogeneity, but also macro and micro scales. H, a measure of cosmic stuff, is literally derivable from atomic stuff.
    - sharpener 5y ago
      I'm not a cosmologist but... Is it possible to have both photon tiring and expansion and still measure the same numbers in experiment? Also wouldn't the arc separation of deep field stars increase detectably with expansion?
      - sahil50 5y ago
        Maybe. But my reasoning is to assume as little as possible and start reasoning up from the point in history where the need for an explanation arose. And the need for an explanation arose when Hubble saw the redshift. He and Zwicky preferred tired light over galactic recession, but the halfwit academic establishment went with galactic recession.
        sharpener 5y ago
        A fair approach. Incidentally, I just drew some diagrams and with the assumptions that the Earth is not at the centre of expansion, Earth orbit has extremes (for parallax), and all light only takes straight routes, my second question has a negative answer. But if one puts a gravitational lens on the view of one of the two stars then (based on a fast doodle though) it looks like maybe expansion could be detected.
oolonthegreat 5y ago
> It increasingly looks like we live in a region in the universe that happens to have a significantly lower density than the average in the visible universe. This area of underdensity which we live in has been called the “local hole” that sounds really weird, if the cosmological principle is invalidated, does that mean that we have to reject the Copernican principle as well? the text seems to imply that there is something "special" about our location in the universe.
- throwaway81523 5y ago
  No I don't think it's like that. We know that matter and vacuum clump together at a series of increasing scales: the solar system, our galaxy, the local cluster, some surrounding supercluster, maybe there is a superdupercluster level after that, but the theory being disputed is that the hierarchical clustering stops after those N levels, and after that, the superduperclusters (or whatever) are distributed randomly instead of grouping into even more enormous structures. The idea is that the universe started as a random fluctuation and that the clusters etc. came from a diffusion process, like stripes on a zebra. The stripes are locally correlated, but less so over longer distances. Sabine H is saying that the clustering goes further than the theory can account for, and that the "local hole" is a feature of this bigger structure, not that it's something special. Anyway, even if our part of the universe is special, there can be an anthropic explanation, like saying we live on the special part of the Earth that has a habitable climate and is not covered with water.
  - Ericson2314 5y ago
    The local hole doesn't seem so contrarian, as the 600 Mly is smaller than the multiple Gly of the funny quasars.
    - throwaway81523 5y ago
      The multiple-Gly funny quasar clusters are also in tension with the existing theory.
- ben_w 5y ago
shmageggy 5y ago
Any time dissenting physics/astronomy opinions show up on here, it's always Sabine Hossenfelder. Is she a lone wolf or the face of a larger community?
- varjag 5y ago
  She's a new kind of popular science presenter, with refreshing depth and command of the subject that's been lacking in this field for ages. She's popular and popular content is getting HN front page often. Add here the dynamics of social media engagement, meaning that more disputed/controversial topics get promoted and shared more. As a physicist she does have certain opinions (would be strange if she didn't), they make for good material so naturally she brings it up. The disputed subjects however are a fraction of her content, which includes covering the well established basics.
  - dgellow 5y ago
    Her music videos are also awesome :)
    - Semaphor 5y ago
      Thanks for the tip. Her current music video channel [0] and a playlist [1] of her older music videos on her science channel. Some of them are her own songs, others are covers. I’m currently enjoying "Cassandra (Prophet of the Dark)" [2] [0]: https://www.youtube.com/channel/UCPtRwW9i43BXbCRQa7BJaiA https://www.youtube.com/channel/UCPtRwW9i43BXbCRQa7BJaiA [1]: https://www.youtube.com/playlist?list=PLwgQsqtH9H5ckD-v9Ux3Tnrn27_WpiDlp https://www.youtube.com/playlist?list=PLwgQsqtH9H5ckD-v9Ux3T... [2]: https://www.youtube.com/watch?v=PX0k0WfMSi0 https://www.youtube.com/watch?v=PX0k0WfMSi0
      - motohagiography 5y ago
        Thank you for these, I just discovered her "Is Time Real?" video linked from it: https://www.youtube.com/watch?v=PdL8CudJTcs https://www.youtube.com/watch?v=PdL8CudJTcs and it was specifically on the topic I was on about in a recent comment, where my own question was whether time is just gravity, or an artifact thereof. She also mentions Julian Barbour, who has apparently posited a theory about how time is not a necessary cosmological dimension as well. Quite a rabbit hole. I can see why people get into this.
DinosaurShampoo 5y ago
If even the Cosmological constant is debunked,there's truly no rules to what's possible.
deleted 5y ago
[deleted]
JoBrad 5y ago
Side tangent: Why are most of her numbers, except dates, spelled out? Is this some convention specific to her country of origin or something?
- platz 5y ago
  This is a transcript of the video embedded below. Some of the explanations may not make sense without the animations in the video.
- tsimionescu 5y ago
  Which numbers are you referring to? "3 billion" instead of "3,000,000,000"? That could just be efficiency of typing (not to mention, German uses , and . inversely from English: Pi is 3,1415... in German writing, while a thousand is 1.000).
  - CurtHagenlocher 5y ago
    Yes, but a German billion isn't the same as an American billion either... .
  - JoBrad 5y ago
    I was thinking of this paragraph. However, after I re-read the article, it seems that there are other numbers that aren't spelled out. Maybe it was an auto-transcription? > Already in nineteen-ninety-one they found the Clowes-Campusano-Quasar group, which is a collection of thirty-four Quasars, about nine point five Billion light years away from us and it extends over two Billion Light-years, clearly too large to be compatible with the prediction from the concordance model.
codethief 5y ago
> Two years ago, I told you about a paper by Subir Sarkar and his colleagues, that showed if one analyses the supernovae data correctly, without assuming that the cosmological principle holds on too short distances, then the evidence for dark energy disappears. That paper has been almost entirely ignored by other scientists. I suppose she's referring to the things discussed in her interview with Sarkar here -> https://www.youtube.com/watch?v=B1mwYxkhMe8 https://www.youtube.com/watch?v=B1mwYxkhMe8 . I can't claim I understand the details of what Sarkar is talking about since I dabbled in cosmology only very briefly but I at least made sure to forward the interview to my former advisor (whose name is on several hundreds of papers on cosmology and astrophysics, including those of the PLANCK collaboration and several others) and his response was along the lines of: > I appreciate Subir Sarkar very much but I'm afraid I don't agree with barely any of his statements. He never looks at the full picture but only individual pieces and then he ends up modifying those until look prettier individually but no longer fit the rest of the cosmological model.
- DudeInBasement 5y ago
  I need more grant money to keep looking for dark garbage. I can't be bothered to question my grants
- codethief 5y ago
  EDIT: > until look prettier individually *until they look prettier individually
gtsop 5y ago
I am so excited to see new observations and theories challenging the current model (Link to earlier comment of mine summarizing what I think is wrong with the established mentality) https://news.ycombinator.com/item?id=27399696 https://news.ycombinator.com/item?id=27399696
Semiapies 5y ago
In honor of weekend HN: https://xkcd.com/1758/ https://xkcd.com/1758/
sesm 5y ago
If you are interested in cosmology, there is a series of papers by Gorkavyi building a cyclic universe cosmological model that's entirely based on Einstein's general relativity and doesn't require any quantum gravity theory. It's based on black holes mergers with mass loss and convertion of mass into gravitational waves, that later get captured by black holes again. https://pos.sissa.it/335/039/ https://pos.sissa.it/335/039/ https://academic.oup.com/mnras/article/476/1/1384/4848298 https://academic.oup.com/mnras/article/476/1/1384/4848298 https://academic.oup.com/mnras/article/461/3/2929/2608669 https://academic.oup.com/mnras/article/461/3/2929/2608669 https://www.sao.ru/Doc-k8/Science/Public/Bulletin/Vol76/N3/ASPB285.pdf https://www.sao.ru/Doc-k8/Science/Public/Bulletin/Vol76/N3/A... (this one is available only in Russian for now)
bryan0 5y ago
> They also point out that if we live in a local hole then this means that the local value of the Hubble rate must be corrected down. This would be good news because currently measurements for the local value of the Hubble rate are in conflict with the value from the early universe. And that discrepancy has been one of the biggest headaches in cosmology in the past years. Wow so a local hole might solve the Hubble measurement problem? I never heard that proposed at a potential solution before…
didibus 5y ago
> Physicists believe they understand quite well how the universe works on large scales Why would a physicist write an article and talk about physicists like they were some mystical "other" single minded group of people. I just hate that characterization, so unhelpful and damaging in my opinion, and kind of manipulative to open up an article with that. I don't actually believe most physicist believe they understand how the universe works, I think most of them feel like there's still so much they don't understand, that it's probably why they wanted to become a physicist in the first place. But I might also be wrong, and in any case, you just shouldn't start your article with a big fallacious generalization that has no data or rationale to back itself up and also somehow position yourself as some sort of "knows better".
stevenalowe 5y ago
Perhaps our universe is the inside of a black hole and the energy for expansion is coming in from elsewhere, creating new spacetime in the center of our universe from mass/energy absorbed in the outer universe. So the cosmo constant would be proportional to mass absorbed times c^2 divided by the volume of our universe - like air inflating a balloon. Early inflation was caused by the initial absorption of mass, and it steadied down since then limited by the black hole’s singularity “throat” capacity and the available of mass/energy to absorb The fun question is then: is the throat of the black hole that contains our universe also in our universe?
Smooth-Weather 5y ago
There is also Jean-Pierre Petit, who presents his Janus Cosmological Model with multiple publications in peer-review journals. It has 19 observational confirmations and various predictions. The Janus bimetric model, for example, describes two parallel universes instead of one, with an opposite time arrow, linked together since the Big Bang and interacting only by gravitation. According to this model, the Universe would be associated with two Riemannian metrics, one with a matter of positive mass and the other with a matter of negative mass, resulting from the CPT symmetry. The two metrics have their own geodesic and are the solution of two coupled field equations. The dark matter would be, in fact, a conglomerates of negative matter. It's interesting, Here is a preprint resuming multiples aspects of it: https://hal.archives-ouvertes.fr/hal-03285671/document https://hal.archives-ouvertes.fr/hal-03285671/document

196 points by nsoonhui 5y ago

rich_sasha 5y ago
There is more evidence for dark energy. Discrepancies in redshift vs distance are just one, and there are interestingly also other explanations for it. IIRC in lambda-CDM, if you don’t have dark energy, the whole universe just looks very different, eg the structures of galaxies, groups and supergroups etc are not the same. It might still be wrong, but more nails are needed for this coffin.
- The_rationalist 5y ago
  MOND lead to less paradoxes/mispredictions than dark matter/energy
- whatshisface 5y ago
  One thing that can happen when you are doing computer modeling to find the input parameters that explain your observations is getting stuck in a local maximum. I am absolutely ready to believe that eliminating dark energy from current models makes their results look less like the real universe, but the number of re-runs that would be required to sample the entire parameter space and demonstrate that there were no other parameterizations that looked like our universe would be enormous, and if you include the possibility of new theories, infinite. There would either have to be some kind of theoretical reason to think that the best known parameterization of a simulated lambda-CDM universe is not merely a local maximum, or the parameters would have to be well-constrained, by observations, so that the free parameter space was small enough to exhaustively explore. I am not aware of either condition being true so I will express some skepticism about the conclusions from the models. Nonetheless, my lack of knowledge about those conditions is not very strong evidence for their absence, and I know there could be someone reading this and feeling very annoyed that I don't know about the Backhausen-Thule principle, or whatever piece completes this puzzle. (Your contribution to the discussion, oh annoyed reader, would be greatly appreciated.)
- michelpp 5y ago
  Sarkar addresses this other evidence in this interview: https://youtu.be/JJzU9hDjiRk?t=819 https://youtu.be/JJzU9hDjiRk?t=819 In summary, there is a strong selection bias in cosmology toward the standard model which induces "predictions" that confirm themselves. One bit of evidence he presents, dozens of studies were found to be within one sigma of the wmap measurement and not naturally distributed as one would expect.
- raattgift 5y ago
  The value for \Lambda, the cosmological constant, is tiny and positive. It's so tiny that as we take it to zero, the universe is still filled with clusters spiral and elliptical galaxies with a strong solid-angle-on-the-sky/brightness/redshift relation, and those galaxies filled with the same sorts of stars we see in the sky. Indeed the evidence available prior to 1998 or so favoured a \Lambda of zero, and the early evidence favouring a tiny positive value was very much a surprise. The Hubble Space telescope had already been running and taking deep views for several years. COBE (https://science.nasa.gov/missions/cobe https://science.nasa.gov/missions/cobe) and the Saskatoon experiment had already finished. None presaged the results of the Supernova Cosmology Project and High-Z Supernova Search Team. Follow-ons by Hubble (and others) and successors to COBE support the accelerated expansion. The physical interpretation of the zero versus the tiny positive value is that in the former there was a last early acceleration which ended essentially all at once, with galaxy clusters then moving purely inertially; or alternatively there was an early acceleration which decayed, possibly in several steps, into a tiny persisting constant acceleration well before the formation of the surface of last scattering (the observed cosmic microwave background). Or alternatively there were mutiple sources of acceleration, one very large and which ceased early, and one which has been always-a-small constant. There are different lines of evidence for how this residual acceleration has evolved. Practically all of it favours it settling down into one constant tiny value in the very early universe, and that the value can be determined with ever greater precision mostly by studying the fine detail in the cosmic microwave background and the various observables of highly red, dim, low-angular-diameter galaxies backlit by quasars and internally lit both by quasars and supernovae. The exact value is a matter of active research, as some of the data is conflicting. None of the data disfavours some ongoing acceleration, and the conflict is generally within 10%. As an example of the physical consequences of the discrepency, the lower value means we can see more galaxies (and more galaxies will be able to see the light from the Crab supernova and other historical galactic supernovae), while the higher value fewer galaxies we can see and a lot fewer galaxies who could see a recent supernova within the Milky Way. There are also various ideas that the tiny value of \Lambda is not constant but continues to evolve. Most of these unfailingly generate observables consistent with a new non-vanishing long-range force to accompany electromagnetism and gravitation, and such an extra ("fifth") force is almost wholly ruled out by evidence. Some store up this fifth force's energy until local matter-energy density is very low (trillions of trillions of years in our future) and unhide it then at various powers (often very high, in an essentially global phase change). Attempts to remove ongoing acceleration altogether by setting \Lambda to zero seem somewhat contrived. A typical approach is to assume that the universe is much less homogeneous than it appears, and that we are being mislead by being in a highly unusual place exceptionally close to the centre of a large matter underdensity. This was of interest to several teams of theoreticians (Clifton, February) around 2008-2009, as they developed specific models -- within general relativity as the theory of gravitation -- in order to try to distinguish whole families of such models from the standard cosmology rather than outright advocating for those models in preference to the standard cosmology. More broadly, this is related to cosmologies that are wildly inhomogeneous at large scales compared to the standard cosmology, such that in some greater-than-galaxy-sized regions of spacetime the matter is much older than in others (in Wiltshire's voids, and in dense areas close to their boundaries, clocks run a lot more quickly so observers will see outside-the-void matter as gravitationally (collapse) rather than cosmologically (accelerated expansion) redshifted). Some of these models are designed to explore how one can generate an averaging procedure for general curved spacetimes, or at least for "lumpy" 3+1-dimensional ones, rather than to really challenge the most general form of the Copernican principle (i.e., they don't really want to put Earth pretty much at the centre of the universe). Motivations do vary though; there are some productive everyday cosmologists whose single-author papers occasionally develop alternatives to the standard cosmology that fit closer to some scripture or other. There are also some modified gravity proponents (some of whom work every day with the standard cosmology) whose theories of gravitation "need help" from a favourable distribution of matter that picks out the region around us as atypical.
avereveard 5y ago
> without assuming that the cosmological principle holds on too short distances There's still the problem of colliding galaxies showing a weakly interacting centroid that's shifted compared to the masses but interacts with the visible masses. If truly are variation in the local constants, then one has to explain why these variations shows inertia, at such point it starts looking more and more like matter
- mdturnerphys 5y ago
  That is evidence for dark matter, not dark energy.
- Ericson2314 5y ago
  That's about dark matter, this was about dark energy.
The_rationalist 5y ago
Is this related to MOND?
Svoka 5y ago
That would be true if young scientists wouldn’t continuously make successful predictions based on cosmological principle among other observable effects of the general relativity and standard model. Make observable prediction, coherent thesis, then we’ll talk. Of course our models are not perfect, but it is best we have. Physics so far never dealt in “fundamental truths”, just good enough models. So far, this is best we got.
- zeven7 5y ago
  I'd argue that Einstein in particular cared a lot about "fundamental truths". Not everyone can be Einstein, but I'm glad some people care about asking deeper questions.
  - kkylin 5y ago
    I don't disagree with your point, but do want to add that not publishing on "fundamental truths" isn't the same as not asking those questions. Not everyone's going to have something novel, plausible, and fundamental to say on a regular basis, hence most publications (even if everyone's asking these questions, which granted they're probably not) are going to be much more incremental.
  - rich_sasha 5y ago
    Ironically, it was Einstein who introduced the “cosmological constant” (and thus indirectly dark energy). I think later in life he called it a glorified fudge factor and his biggest regret.
    - raattgift 5y ago
      Wikipedia covers this sufficiently at https://en.wikipedia.org/wiki/Cosmological_constant#Sequence_of_events_1915%E2%80%931998 https://en.wikipedia.org/wiki/Cosmological_constant#Sequence... The five-line tl;dr: non-expanding cosmologies with no big bang but lots of galaxies tend to collapse in finite time. One can avoid collapse with a positive cosmological constant. That approach predated the work of Hubble (expansion) and Lemaître (big bang). Expanding cosmologies with a sufficiently large initial big bang do not need a cosmological constant to keep expanding forever. Einstein, not being stupid, recognized that and carried on. Since 1998: an accelerating expanding universe is inconsistent with just a single big bang as impulse, but is consistent with a small positive cosmological constant. Einstein and Schrödinger certainly discussed whether to treat the cosmological constant as an energy entering into the right hand side of the Einstein Field Equations instead of a multiplier on the metric in the left hand side: [Harvey 2012] https://arxiv.org/abs/1211.6338 https://arxiv.org/abs/1211.6338 Their conclusion is that choice of side is principally a matter of aesthetics, and that remains true today. Harvey2012 §5 is a good reminder not to put too much weight into the early days of general relativity. Exact solutions were few and simple but still extraordinarily hard to work with by hand. Numerical approaches didn't exist, nor did formalisms that provide post-Newtonian approximations that are more tractable. Realistic distributions of matter were largely as-yet undiscovered (compare 1917 introduction of cosmological constant and low estimates of the number of spiral galaxies in the sky, their mass, and the light-travel distance to them: https://en.wikipedia.org/wiki/Great_Debate_(astronomy) https://en.wikipedia.org/wiki/Great_Debate_(astronomy) which came later). Einstein's adaptation to the flood of astronomical discoveries during his productive lifetime is part of what made him Einstein rather than any less celebrated figure.
neuronic 5y ago
Of course. Science is just a chase for grant money. Lots of entertainment money to be earned and documentaries can be made about "dark energy". Knowledge discovery is secondary or tertiary to modern science. The field is full of greedy egomaniacs, leaving the honest scientists at a competitive disadvantage. It's about reputation and $$$.
analog31 5y ago
I think this is an aside to what you're asking, but "science advances one funeral at a time" was a clever slogan and not an empirically tested hypothesis.
- garmaine 5y ago
  It’s not meant to be an empirically testable hypotheses though.
zeofig 5y ago
No. That's a meme.

Not knowing much about the subject: cosmological principle appears to say that laws of physics are uniform in space. Then, with known matter and forces, this leads to some structure, with fluctuations, and hence some scale over which matter is uniformly distributed. If we calculate such a scale and find matter is still not uniform at that scale, wouldn’t the first conclusion be that there are missing terms in either matter or interactions (or both)? Rather than saying that laws of physics are not space-homogeneous. The article itself states that the length scale where the c10l principle kicks in is derived from a particular model for matter and interactions (lambda CDM). I think there is plenty of discrepancies between standard model and observations (most of them small). We don’t know what dark matter is, either. So to me the interesting point wouldn’t be, is the model wrong, but how is it wrong?

ianai 5y ago
Per Sabine H on YouTube ( https://youtu.be/JETGS64kTys https://youtu.be/JETGS64kTys ), the cosmological constant might be smaller than called for in current cosmology. That would agree with some other observations.
deleted 5y ago
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evgen 5y ago
> the c10l principle Don't do this. It is bad enough that every major devops/infra component needs to create some <letter><number_of_missing_letters><letter> tag, but dropping it in to random places is worse than the regular backronyms and cute project names science and tech people use to try to hide complexity. It just adds confusion for no rhyme or reason other than trying to sound like you are a part of some club of insiders.
- beeboop 5y ago
  You see it everywhere really. Military and politicians and government orgs all do it to embarrassing lengths too

drran 5y ago

n 2004, New Scientist, published an open letter from Eric Lerner and about 30 other scientists,[1] criticizing the Big Bang theory, and noting that Big Bang theory requires Dark Matter to exists. «Without some kind of dark matter, unlike any that we have observed on Earth despite 20 years of experiments, big-bang theory makes contradictory predictions for the density of matter in the universe. Inflation requires a density 20 times larger than that implied by big bang nucleosynthesis, the theory’s explanation of the origin of the light elements. And without dark energy, the theory predicts that the universe is only about 8 billion years old, which is billions of years younger than the age of many stars in our galaxy.» Can we finally abandon Big Shrink (BS) theory? It's obvious now that Oort cloud of Shapley attractor just collided with Dipole Repeller cloud [2]. [1]: https://www.plasma-universe.com/an-open-letter-to-the-scientific-community/ https://www.plasma-universe.com/an-open-letter-to-the-scient... [2]: https://vimeo.com/189355968 https://vimeo.com/189355968

sahil50 5y ago

Another problem with the standard model is attributing the cosmological redshift to the Doppler effect.

FridayoLeary 5y ago
could you pls elaborate on that?
- JPLeRouzic 5y ago
  sahil50 posted this 2 months ago: https://colab.research.google.com/drive/1K1qoUFvqZp1fWbpcKJWq63nflgwS0ZHh?usp=sharing https://colab.research.google.com/drive/1K1qoUFvqZp1fWbpcKJW...
- andyjohnson0 5y ago
  I'm not the parent commenter, and I'm not a physicist, but this might be a reference to the non-mainstream theories that are often grouped under the heading of "plasma cosmology". https://en.m.wikipedia.org/wiki/Plasma_cosmology https://en.m.wikipedia.org/wiki/Plasma_cosmology
- sahil50 5y ago
  What Hubble objectively measured wasn't galaxies receding. He measured redshift. Or photon energy loss. And there's another way to explain this, that is simpler, self-consistent, and doesn't require the concept of "inflation" where apparently space expanded faster than the speed of light. The explanation: photon hubbling, tired light. That galaxies are frankly right where they are. They're not receding. The photon loses energy. It costs energy to forge a path through spacetime.
  - naasking 5y ago
    "Tired light" has failed other tests, so it's probably not the answer.
    - sahil50 5y ago

sahil50 5y ago

(1/H * c) = (1/α * ke^2 / (electron mass * c^2)) * (h / (proton mass * c * pi/2)) / (2G * proton mass / c^2)

mkl 5y ago
What does that mean in this context? How does it relate to the cosmological principle in the article?
- sahil50 5y ago
  Hubble's constant is related to all the other fundamental constants. And is not a measure of "expansion", which is one of the core ideas of the Standard Model. Relation to the cosmological principle: self-similarity not just in terms of density and homogeneity, but also macro and micro scales. H, a measure of cosmic stuff, is literally derivable from atomic stuff.
  - sharpener 5y ago
    I'm not a cosmologist but... Is it possible to have both photon tiring and expansion and still measure the same numbers in experiment? Also wouldn't the arc separation of deep field stars increase detectably with expansion?
    - sahil50 5y ago
      Maybe. But my reasoning is to assume as little as possible and start reasoning up from the point in history where the need for an explanation arose. And the need for an explanation arose when Hubble saw the redshift. He and Zwicky preferred tired light over galactic recession, but the halfwit academic establishment went with galactic recession.
      - sharpener 5y ago
        A fair approach. Incidentally, I just drew some diagrams and with the assumptions that the Earth is not at the centre of expansion, Earth orbit has extremes (for parallax), and all light only takes straight routes, my second question has a negative answer. But if one puts a gravitational lens on the view of one of the two stars then (based on a fast doodle though) it looks like maybe expansion could be detected.

oolonthegreat 5y ago

> It increasingly looks like we live in a region in the universe that happens to have a significantly lower density than the average in the visible universe. This area of underdensity which we live in has been called the “local hole” that sounds really weird, if the cosmological principle is invalidated, does that mean that we have to reject the Copernican principle as well? the text seems to imply that there is something "special" about our location in the universe.

throwaway81523 5y ago
No I don't think it's like that. We know that matter and vacuum clump together at a series of increasing scales: the solar system, our galaxy, the local cluster, some surrounding supercluster, maybe there is a superdupercluster level after that, but the theory being disputed is that the hierarchical clustering stops after those N levels, and after that, the superduperclusters (or whatever) are distributed randomly instead of grouping into even more enormous structures. The idea is that the universe started as a random fluctuation and that the clusters etc. came from a diffusion process, like stripes on a zebra. The stripes are locally correlated, but less so over longer distances. Sabine H is saying that the clustering goes further than the theory can account for, and that the "local hole" is a feature of this bigger structure, not that it's something special. Anyway, even if our part of the universe is special, there can be an anthropic explanation, like saying we live on the special part of the Earth that has a habitable climate and is not covered with water.
- Ericson2314 5y ago
  The local hole doesn't seem so contrarian, as the 600 Mly is smaller than the multiple Gly of the funny quasars.
  - throwaway81523 5y ago
    The multiple-Gly funny quasar clusters are also in tension with the existing theory.
ben_w 5y ago

shmageggy 5y ago

Any time dissenting physics/astronomy opinions show up on here, it's always Sabine Hossenfelder. Is she a lone wolf or the face of a larger community?

varjag 5y ago
She's a new kind of popular science presenter, with refreshing depth and command of the subject that's been lacking in this field for ages. She's popular and popular content is getting HN front page often. Add here the dynamics of social media engagement, meaning that more disputed/controversial topics get promoted and shared more. As a physicist she does have certain opinions (would be strange if she didn't), they make for good material so naturally she brings it up. The disputed subjects however are a fraction of her content, which includes covering the well established basics.
- dgellow 5y ago
  Her music videos are also awesome :)
  - Semaphor 5y ago
    Thanks for the tip. Her current music video channel [0] and a playlist [1] of her older music videos on her science channel. Some of them are her own songs, others are covers. I’m currently enjoying "Cassandra (Prophet of the Dark)" [2] [0]: https://www.youtube.com/channel/UCPtRwW9i43BXbCRQa7BJaiA https://www.youtube.com/channel/UCPtRwW9i43BXbCRQa7BJaiA [1]: https://www.youtube.com/playlist?list=PLwgQsqtH9H5ckD-v9Ux3Tnrn27_WpiDlp https://www.youtube.com/playlist?list=PLwgQsqtH9H5ckD-v9Ux3T... [2]: https://www.youtube.com/watch?v=PX0k0WfMSi0 https://www.youtube.com/watch?v=PX0k0WfMSi0
    - motohagiography 5y ago
      Thank you for these, I just discovered her "Is Time Real?" video linked from it: https://www.youtube.com/watch?v=PdL8CudJTcs https://www.youtube.com/watch?v=PdL8CudJTcs and it was specifically on the topic I was on about in a recent comment, where my own question was whether time is just gravity, or an artifact thereof. She also mentions Julian Barbour, who has apparently posited a theory about how time is not a necessary cosmological dimension as well. Quite a rabbit hole. I can see why people get into this.

DinosaurShampoo 5y ago

If even the Cosmological constant is debunked,there's truly no rules to what's possible.

deleted 5y ago

[deleted]

JoBrad 5y ago

Side tangent: Why are most of her numbers, except dates, spelled out? Is this some convention specific to her country of origin or something?

platz 5y ago
This is a transcript of the video embedded below. Some of the explanations may not make sense without the animations in the video.
tsimionescu 5y ago
Which numbers are you referring to? "3 billion" instead of "3,000,000,000"? That could just be efficiency of typing (not to mention, German uses , and . inversely from English: Pi is 3,1415... in German writing, while a thousand is 1.000).
- CurtHagenlocher 5y ago
  Yes, but a German billion isn't the same as an American billion either... .
- JoBrad 5y ago
  I was thinking of this paragraph. However, after I re-read the article, it seems that there are other numbers that aren't spelled out. Maybe it was an auto-transcription? > Already in nineteen-ninety-one they found the Clowes-Campusano-Quasar group, which is a collection of thirty-four Quasars, about nine point five Billion light years away from us and it extends over two Billion Light-years, clearly too large to be compatible with the prediction from the concordance model.

codethief 5y ago

> Two years ago, I told you about a paper by Subir Sarkar and his colleagues, that showed if one analyses the supernovae data correctly, without assuming that the cosmological principle holds on too short distances, then the evidence for dark energy disappears. That paper has been almost entirely ignored by other scientists. I suppose she's referring to the things discussed in her interview with Sarkar here -> https://www.youtube.com/watch?v=B1mwYxkhMe8 https://www.youtube.com/watch?v=B1mwYxkhMe8 . I can't claim I understand the details of what Sarkar is talking about since I dabbled in cosmology only very briefly but I at least made sure to forward the interview to my former advisor (whose name is on several hundreds of papers on cosmology and astrophysics, including those of the PLANCK collaboration and several others) and his response was along the lines of: > I appreciate Subir Sarkar very much but I'm afraid I don't agree with barely any of his statements. He never looks at the full picture but only individual pieces and then he ends up modifying those until look prettier individually but no longer fit the rest of the cosmological model.

DudeInBasement 5y ago
I need more grant money to keep looking for dark garbage. I can't be bothered to question my grants
codethief 5y ago
EDIT: > until look prettier individually *until they look prettier individually

gtsop 5y ago

I am so excited to see new observations and theories challenging the current model (Link to earlier comment of mine summarizing what I think is wrong with the established mentality) https://news.ycombinator.com/item?id=27399696 https://news.ycombinator.com/item?id=27399696

Semiapies 5y ago

In honor of weekend HN: https://xkcd.com/1758/ https://xkcd.com/1758/

sesm 5y ago

If you are interested in cosmology, there is a series of papers by Gorkavyi building a cyclic universe cosmological model that's entirely based on Einstein's general relativity and doesn't require any quantum gravity theory. It's based on black holes mergers with mass loss and convertion of mass into gravitational waves, that later get captured by black holes again. https://pos.sissa.it/335/039/ https://pos.sissa.it/335/039/ https://academic.oup.com/mnras/article/476/1/1384/4848298 https://academic.oup.com/mnras/article/476/1/1384/4848298 https://academic.oup.com/mnras/article/461/3/2929/2608669 https://academic.oup.com/mnras/article/461/3/2929/2608669 https://www.sao.ru/Doc-k8/Science/Public/Bulletin/Vol76/N3/ASPB285.pdf https://www.sao.ru/Doc-k8/Science/Public/Bulletin/Vol76/N3/A... (this one is available only in Russian for now)

bryan0 5y ago

> They also point out that if we live in a local hole then this means that the local value of the Hubble rate must be corrected down. This would be good news because currently measurements for the local value of the Hubble rate are in conflict with the value from the early universe. And that discrepancy has been one of the biggest headaches in cosmology in the past years. Wow so a local hole might solve the Hubble measurement problem? I never heard that proposed at a potential solution before…

didibus 5y ago

> Physicists believe they understand quite well how the universe works on large scales Why would a physicist write an article and talk about physicists like they were some mystical "other" single minded group of people. I just hate that characterization, so unhelpful and damaging in my opinion, and kind of manipulative to open up an article with that. I don't actually believe most physicist believe they understand how the universe works, I think most of them feel like there's still so much they don't understand, that it's probably why they wanted to become a physicist in the first place. But I might also be wrong, and in any case, you just shouldn't start your article with a big fallacious generalization that has no data or rationale to back itself up and also somehow position yourself as some sort of "knows better".

stevenalowe 5y ago

Perhaps our universe is the inside of a black hole and the energy for expansion is coming in from elsewhere, creating new spacetime in the center of our universe from mass/energy absorbed in the outer universe. So the cosmo constant would be proportional to mass absorbed times c^2 divided by the volume of our universe - like air inflating a balloon. Early inflation was caused by the initial absorption of mass, and it steadied down since then limited by the black hole’s singularity “throat” capacity and the available of mass/energy to absorb The fun question is then: is the throat of the black hole that contains our universe also in our universe?

Smooth-Weather 5y ago

There is also Jean-Pierre Petit, who presents his Janus Cosmological Model with multiple publications in peer-review journals. It has 19 observational confirmations and various predictions. The Janus bimetric model, for example, describes two parallel universes instead of one, with an opposite time arrow, linked together since the Big Bang and interacting only by gravitation. According to this model, the Universe would be associated with two Riemannian metrics, one with a matter of positive mass and the other with a matter of negative mass, resulting from the CPT symmetry. The two metrics have their own geodesic and are the solution of two coupled field equations. The dark matter would be, in fact, a conglomerates of negative matter. It's interesting, Here is a preprint resuming multiples aspects of it: https://hal.archives-ouvertes.fr/hal-03285671/document https://hal.archives-ouvertes.fr/hal-03285671/document