New Evidence Against the Standard Model of Cosmology(backreaction.blogspot.com)
backreaction.blogspot.com
New Evidence Against the Standard Model of Cosmology
http://backreaction.blogspot.com/2021/09/new-evidence-against-standard-model-of.html
108 comments
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.
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.
Not everyone can be Einstein, but I'm glad some people care about asking deeper questions.
Einstein is a great mind. His importance is greatly overblown by pop culture and politics. Outstanding mind, but not unique. He built small bricks on shoulders of titans and with lots of help from his co authors. Would he be born 50 years earlier, none of his discoveries were made.
Anyway. This is outside the topic. Every person who does physics cares about "fundamental truths" But even such great minds as Einstein build their models understanding limits of the model, in best case scenario.
Anyway. This is outside the topic. Every person who does physics cares about "fundamental truths" But even such great minds as Einstein build their models understanding limits of the model, in best case scenario.
This is an easy and naive view of Einstein. Would you argue the same for Newton? The truth is special relativity was going to be discovered soon regardless, general relativity was a leap that required a leader as unique as Einstein, Newton, Galileo.
Of course he had a lot of help from Hilbert. I don't consider collaborating on a discovery as grounds to dismiss a scientist as "not unique".
Of course he had a lot of help from Hilbert. I don't consider collaborating on a discovery as grounds to dismiss a scientist as "not unique".
And he made mistakes based on his bias on what "should" be like all of us. Not everyone can do maths like Einstein, but on this particular point everyone can say "God doesn't do X" and be wrong.
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.
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.
Wikipedia covers this sufficiently at 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 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) 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.
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 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) 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.
He cared about fundamental truths, but he didn’t think we had them.
“ all our science, measured against reality, is primitive and childlike — and yet it is the most precious thing we have.”
The best we can ever say about science is that it is useful, that’s what truth means in science, that it produces accurate predictions. Truth in any deeper sense is a matter for philosophers.
“ all our science, measured against reality, is primitive and childlike — and yet it is the most precious thing we have.”
The best we can ever say about science is that it is useful, that’s what truth means in science, that it produces accurate predictions. Truth in any deeper sense is a matter for philosophers.
He didn't think we had those truths yet but I do think it's clear he thought it was the job of scientists (not only philosophers) to discover them. That's his major motivation behind the EPR paradox, general relativity, and the search for a greater theory.
If you look at what he did, he wanted to figure out what is true. General relativity answered Newton's "metaphysical" question about how gravity could act on bodies at a distance.
If you look at what he did, he wanted to figure out what is true. General relativity answered Newton's "metaphysical" question about how gravity could act on bodies at a distance.
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.
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.
MOND lead to less paradoxes/mispredictions than dark matter/energy
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.)
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.)
Sarkar addresses this other evidence in this interview:
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.
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.
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) 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.
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) 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.
No. That's a meme.
> 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
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
That is evidence for dark matter, not dark energy.
That's about dark matter, this was about dark energy.
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 $$$.
Knowledge discovery is secondary or tertiary to modern science. The field is full of greedy egomaniacs, leaving the honest scientists at a competitive disadvantage. It's about reputation and $$$.
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?
She might be right but, as of now, the evidence shows that she is probably not right.
But as with everything, contrarian point of view is always popular on the internet. And we all want be in the know (have some secret knowledge) thus posts like this are popular.
So if she is really right we will feel like winners - if not, who cares: it is internet.
But as with everything, contrarian point of view is always popular on the internet. And we all want be in the know (have some secret knowledge) thus posts like this are popular.
So if she is really right we will feel like winners - if not, who cares: it is internet.
Ya, it's so easy to point out something might not be exactly the way we thought, this position is probably the statistical more likely outcome anyways, we always refine our understanding of the universe year over year, it's unlikely we cracked the full extent of it yet. So if you just lived as a contrarian over time it be easy to always point out how we had one or more things "wrong", and make the claim you were thus right all along.
What I'd like to see more of is, alright smarty pants, what's your alternate theory and where is your superior evidence, and how is it more useful?
What I'd like to see more of is, alright smarty pants, what's your alternate theory and where is your superior evidence, and how is it more useful?
The love of contrarian views can be quite nauseating on hacker news. Post a somewhat mainstream, but interesting article, and prepare to watch it get nit-picked to death before commenters conclude it was only published due to reviewer friendships and p hacking. Meanwhile a contrarian article is immediately accepted as fact and the only reason scientists haven’t agreed is that they’re too stubborn.
There are a bunch of people with similar thoughts. Just recently a blogpost by Peter Woidt showed up here [1]. While I'm only following this as a lay person I think you can say Woidt and Hossenfelder come from the same corner of "critics of contemporary physics" or however you want to call them.
[1] https://news.ycombinator.com/item?id=28325753
[1] https://news.ycombinator.com/item?id=28325753
Careful there, you're standing on a Hacker News landmine. For whatever reason, whenever Woit's name is invoked here the downvote brigade is not far away.
Huh, is that so? Why?
Anyway, I haven't even said whether I agree with him or not (which tbh wouldn't be very relevant, as I know where my limits are, and judging debates in physics is definitely outside my area of expertise).
Anyway, I haven't even said whether I agree with him or not (which tbh wouldn't be very relevant, as I know where my limits are, and judging debates in physics is definitely outside my area of expertise).
I also watch PBS spacetime series.
I think https://youtu.be/dsCjRjA4O7Y is relevant here.
I think https://youtu.be/dsCjRjA4O7Y is relevant here.
I wonder if she heard about the Stationary Universe Model of Peter Ostermann [1]. He argues along similar lines reagarding the inference of dark energy from the supernovae data.
[1] http://www.peter-osterman.org/index.html
[1] http://www.peter-osterman.org/index.html
I have another error I'd like to discuss with her, but she charges to speak with one of her people. Sorry, I'm not paying for that :-)
She comes into the field from a mathematical background. In that sense she is an outsider.
That is so bizarre. And where would physics be without the mathematicians since Newton? Not a pretty picture would be my guess. But maybe I'm wrong, and all the experiments done in lieu of solving triple-intervals would have made a profound difference. (Einstein's best work came before he got bogged down in math.)
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.
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.
I like her much more than Harald Lesch or MaiLab.
She makes a smart, but also down to earth impression.
The other science presenters are always so full of themselves that I can't watch them.
She makes a smart, but also down to earth impression.
The other science presenters are always so full of themselves that I can't watch them.
Her music videos are also awesome :)
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
[1]: https://www.youtube.com/playlist?list=PLwgQsqtH9H5ckD-v9Ux3T...
[2]: https://www.youtube.com/watch?v=PX0k0WfMSi0
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
[1]: https://www.youtube.com/playlist?list=PLwgQsqtH9H5ckD-v9Ux3T...
[2]: https://www.youtube.com/watch?v=PX0k0WfMSi0
Thank you for these, I just discovered her "Is Time Real?" video linked from it: 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.
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.
I think it's probably fair to say most cosmologists would consider her views marginal, but she is certainly not a crank. My (limited) understanding is that ΛCDM fits cosmological observations extremely well; however, neither dark matter nor dark energy has actually been shown unambiguously to exist. 'Mainstream' cosmology invariably also includes inflation, which remains essentially a speculative idea unsupported by any hard observational evidence. Sabine Hossenfelder has become a popular commentator by drawing attention to discussions of these and other issues.
She's discussing findings that come from papers written by other scientists, so she is obviously not a lone wolf.
I love her so much. Everything she explains is so crystal clear.
I think she is a really credible voice, given her background in theoretical physics and her matter-of-fact demeanor, plus her tendency to express all the necessary caveats. As such, when you see a dissenting belief from her, you are more likely to have people actually believe there is something there and not just BS. I think this is a major factor - basically, dissenting opinions discussed by Sabine Hossenfelder carry more weight than others.
> 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 .
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.
I suppose she's referring to the things discussed in her interview with Sarkar here -> 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.
EDIT:
> until look prettier individually
*until they look prettier individually
> until look prettier individually
*until they look prettier individually
> 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…
Wow so a local hole might solve the Hubble measurement problem? I never heard that proposed at a potential solution before…
> 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.
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.
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.
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.
The local hole doesn't seem so contrarian, as the 600 Mly is smaller than the multiple Gly of the funny quasars.
The multiple-Gly funny quasar clusters are also in tension with the existing theory.
> the text seems to imply that there is something "special" about our location in the universe.
The counterpoint to the Copernican principle is the anthropic principle: we can only find ourselves in places which support the existence of beings like us.
I have no idea if the density variation even might be important for chances of industrial intelligence, but people have suggested galactic (not just stellar) Goldilocks zones as one requirement (and separately “having a very large moon”), so I also wouldn’t automatically dismiss anyone who said it was important.
The counterpoint to the Copernican principle is the anthropic principle: we can only find ourselves in places which support the existence of beings like us.
I have no idea if the density variation even might be important for chances of industrial intelligence, but people have suggested galactic (not just stellar) Goldilocks zones as one requirement (and separately “having a very large moon”), so I also wouldn’t automatically dismiss anyone who said it was important.
1/2
For space reasons I'll cut my reply into two parts. The first discusses the Copernican principle in question, the second answers your question about this specific blog post.
The modern understanding (and name) of the Copernican principle is really owed to mid-20th-century Hermann Bondi's work in general relativity, and it is a generalization of the initial Copernican model of heliocentricity, with the sun at the centre of the universe, and the Earth, other planets, and distant stars tracing out exactly circular concentric orbits around it.
At its most general while still retaining its strength, the Copernican principle says that in a system with certain symmetries, there is no distinguished position on a circular orbit. This is not just orbits within a 4-dimensional spacetime; it applies in certain many-dimensional phase spaces too.
(One can generalize further by giving up some strength and say that most spaces with certain symmetries admit a notion of typicality which applies to any choice of initial momentum almost everywhere in the space. We can then discuss how such a measure breaks in more complicated systems. Consider translational symmetry on the Earth on an overcast moonless night. If you choose a random spot on Earth and then swim or walk a kilometre or ten in any direction, your view of the surface features out to the horizon is unlikely to change. If you found yourself somewhere in a salty body of water nowhere near land you would struggle to tell with any precision where on Earth you were or which compass direction you had moved. If you found yourself somewhere in a sandy desert or flat scrubland far from human settlement and no "celestial guides" like the position of the sun, again you would struggle to tell with any precision where on Earth you were or the direction you are facing. There are however atypical features of the surface of the Earth which break translation symmetry: coasts, edges of forests, peaks of mountains, human settlements, Manhattan, you name it. Moving from water to land or vice-versa clearly breaks some global notions of typicality. However there is a lot of coast on the Earth. You'd probably only find complete atypicality when close enough to major landmarks like the Great Pyramids of Giza or Niagara Falls. We can also add in a notion of temporal typicality -- sufficiently close to sunrise or sunset, or on starry nights, it is easier to orient oneself towards compass points.)
Our solar system's mass distribution is only approximately spherically symmetric, and planetary orbits are non-circular ellipses, so Copernican heliocentricity holds only approximately. And of course we now know that other stars do not orbit our own (even nearby ones do not move in a circular or even elliptical orbit around it). The Copernican approximation is still locally useful as a basis for comparison with observations, and those led quickly to Kepler discovering the features of stable elliptical orbits, Galileo discovering the large moons of Jupiter and their orbits around it, he and others the phases of various planetary bodies, and ultimately Newtonian gravitation.
Copernican heliocentrism is thus correct in some effective limit: it works as long as we do not look too closely at small details of the sun's wobbles or perturbation of various orbits by Jupiter, and as long as we are only considering things at a solar system scale. (It applies in many other solar systems too: a central mass tends to entrain smaller masses into nearly-circular orbits. And it is useful for comparison studies of star systems where orbits are far from circular (many many comets, strange exoplanets) or where there are two or more stellar masses surrounded by smaller bodies.). And that it is not exactly correct made (and still makes) it even more useful in exploration of the real solar system.
There is a notion of Copernican typicality in galaxies too. There is nothing clearly special about our solar system's place on its orbit through the Milky Way, thanks to the galaxy's approximate axisymmetry. Likewise, except close to the galactic centre, the galactic edge, or well outside the plane of the disc, virtually all star system orbits through the Milky way are highly typical. As in Copernican heliocentrism where the position of Earth at any time isn't particularly special, "Copernican Sgr A* centrism" means the position of the sun isn't particularly special either. Of course we are adapted to "goldilocks" atypicality at the solar system scale: we thrive in a family of approximately 1 a.u. orbits, and would struggle to survive in most others. We are less sensitive to the path our solar system takes through the galaxy.
Next, there is the Copernican principle in cosmology. This Cosmological Principle starts with the greatest symmetry: a universe which looks the same in every direction from every possible vantage point. Cosmology is in many ways a study of how the Cosmological Principle breaks down. It does in various ways:
* Locally, we're on a planet. On a starry night, down looks very different from up. There are our solar system's planets in various directions but not in most directions.
* We're also in a galaxy in a local cluster: from the southern hemisphere we see the galactic bulge. Dust and gas distributions are denser in some directions than others. We can also see satellite galaxies like the large Magellanic cloud. We can also see M31 taking up a surprisingly large solid angle of the sky (more than the moon; it's just that the Andromeda galaxy is dim), and a handful of others.
* There is a Cosmic Web structure to bright clusters of galaxies, and (misleadingly named but definitely sparser) "supervoids" between the filaments of the web. There are also smaller overdensities and underdensities in these large regions.
However, we have not done much damage to the typicality of our vantage point. There are lots of similar star systems in lots of similar galaxies in lots of similar clusters in some area of similar Cosmic Web density.
It is clear, though, that the entire cosmos is not uniform, that there are various boundaries against which one can take an orientation.
Cosmology is also about understanding temporal typicality too. Even in the very early 20th century, there were questions being studied: has the universe always looked like this, with lots of galaxies containing many stars like our own? Trying to answer this question with the hard requirement that any answer be in concordance with available evidence led us to a definite no. In the reddest, dimmest, smallest-solid-angle galaxies we have observed, our sun would be extremely atypical based on its spectral lines indicating elements other than hydrogen and helium, but in less-red, less-dim, less-small-solid-angle galaxies (right up to M31) we see that our sun would be less and less unusual.
We can then think of temporal boundaries: what happens in the very earliest times? What's at the highest redshift (answer: the cosmic microwave background and no bright galaxies)? What does that imply about the deeper past? Does it imply anything about the future?
The concordance cosmology -- the standard cosmology, with \Lambda-CDM serving as its mathematical expression -- works exactly with all these various "distractions" smoothed out. Rather than considering star-filled galaxies forming clusters of various sizes, we consider a dust uniformly scattered through an expanding space, with non-gravitational interactions (radiation pressure) becoming more important in the past and less important in the future. This picture is then deliberately perturbed with features found by astronomers, and those perturbations are studied for their impact. Most remain local, a scale far far from cosmological.
Informally, this means "We don't care what happens inside individual galaxies, each of which is just one mote of the cosmological dust, and we track the components generating the energy-density of a typical point in space as the dust -- or its various components -- dilute with the expansion, or grow denser as we look into the deep past".
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For space reasons I'll cut my reply into two parts. The first discusses the Copernican principle in question, the second answers your question about this specific blog post.
The modern understanding (and name) of the Copernican principle is really owed to mid-20th-century Hermann Bondi's work in general relativity, and it is a generalization of the initial Copernican model of heliocentricity, with the sun at the centre of the universe, and the Earth, other planets, and distant stars tracing out exactly circular concentric orbits around it.
At its most general while still retaining its strength, the Copernican principle says that in a system with certain symmetries, there is no distinguished position on a circular orbit. This is not just orbits within a 4-dimensional spacetime; it applies in certain many-dimensional phase spaces too.
(One can generalize further by giving up some strength and say that most spaces with certain symmetries admit a notion of typicality which applies to any choice of initial momentum almost everywhere in the space. We can then discuss how such a measure breaks in more complicated systems. Consider translational symmetry on the Earth on an overcast moonless night. If you choose a random spot on Earth and then swim or walk a kilometre or ten in any direction, your view of the surface features out to the horizon is unlikely to change. If you found yourself somewhere in a salty body of water nowhere near land you would struggle to tell with any precision where on Earth you were or which compass direction you had moved. If you found yourself somewhere in a sandy desert or flat scrubland far from human settlement and no "celestial guides" like the position of the sun, again you would struggle to tell with any precision where on Earth you were or the direction you are facing. There are however atypical features of the surface of the Earth which break translation symmetry: coasts, edges of forests, peaks of mountains, human settlements, Manhattan, you name it. Moving from water to land or vice-versa clearly breaks some global notions of typicality. However there is a lot of coast on the Earth. You'd probably only find complete atypicality when close enough to major landmarks like the Great Pyramids of Giza or Niagara Falls. We can also add in a notion of temporal typicality -- sufficiently close to sunrise or sunset, or on starry nights, it is easier to orient oneself towards compass points.)
Our solar system's mass distribution is only approximately spherically symmetric, and planetary orbits are non-circular ellipses, so Copernican heliocentricity holds only approximately. And of course we now know that other stars do not orbit our own (even nearby ones do not move in a circular or even elliptical orbit around it). The Copernican approximation is still locally useful as a basis for comparison with observations, and those led quickly to Kepler discovering the features of stable elliptical orbits, Galileo discovering the large moons of Jupiter and their orbits around it, he and others the phases of various planetary bodies, and ultimately Newtonian gravitation.
Copernican heliocentrism is thus correct in some effective limit: it works as long as we do not look too closely at small details of the sun's wobbles or perturbation of various orbits by Jupiter, and as long as we are only considering things at a solar system scale. (It applies in many other solar systems too: a central mass tends to entrain smaller masses into nearly-circular orbits. And it is useful for comparison studies of star systems where orbits are far from circular (many many comets, strange exoplanets) or where there are two or more stellar masses surrounded by smaller bodies.). And that it is not exactly correct made (and still makes) it even more useful in exploration of the real solar system.
There is a notion of Copernican typicality in galaxies too. There is nothing clearly special about our solar system's place on its orbit through the Milky Way, thanks to the galaxy's approximate axisymmetry. Likewise, except close to the galactic centre, the galactic edge, or well outside the plane of the disc, virtually all star system orbits through the Milky way are highly typical. As in Copernican heliocentrism where the position of Earth at any time isn't particularly special, "Copernican Sgr A* centrism" means the position of the sun isn't particularly special either. Of course we are adapted to "goldilocks" atypicality at the solar system scale: we thrive in a family of approximately 1 a.u. orbits, and would struggle to survive in most others. We are less sensitive to the path our solar system takes through the galaxy.
Next, there is the Copernican principle in cosmology. This Cosmological Principle starts with the greatest symmetry: a universe which looks the same in every direction from every possible vantage point. Cosmology is in many ways a study of how the Cosmological Principle breaks down. It does in various ways:
* Locally, we're on a planet. On a starry night, down looks very different from up. There are our solar system's planets in various directions but not in most directions.
* We're also in a galaxy in a local cluster: from the southern hemisphere we see the galactic bulge. Dust and gas distributions are denser in some directions than others. We can also see satellite galaxies like the large Magellanic cloud. We can also see M31 taking up a surprisingly large solid angle of the sky (more than the moon; it's just that the Andromeda galaxy is dim), and a handful of others.
* There is a Cosmic Web structure to bright clusters of galaxies, and (misleadingly named but definitely sparser) "supervoids" between the filaments of the web. There are also smaller overdensities and underdensities in these large regions.
However, we have not done much damage to the typicality of our vantage point. There are lots of similar star systems in lots of similar galaxies in lots of similar clusters in some area of similar Cosmic Web density.
It is clear, though, that the entire cosmos is not uniform, that there are various boundaries against which one can take an orientation.
Cosmology is also about understanding temporal typicality too. Even in the very early 20th century, there were questions being studied: has the universe always looked like this, with lots of galaxies containing many stars like our own? Trying to answer this question with the hard requirement that any answer be in concordance with available evidence led us to a definite no. In the reddest, dimmest, smallest-solid-angle galaxies we have observed, our sun would be extremely atypical based on its spectral lines indicating elements other than hydrogen and helium, but in less-red, less-dim, less-small-solid-angle galaxies (right up to M31) we see that our sun would be less and less unusual.
We can then think of temporal boundaries: what happens in the very earliest times? What's at the highest redshift (answer: the cosmic microwave background and no bright galaxies)? What does that imply about the deeper past? Does it imply anything about the future?
The concordance cosmology -- the standard cosmology, with \Lambda-CDM serving as its mathematical expression -- works exactly with all these various "distractions" smoothed out. Rather than considering star-filled galaxies forming clusters of various sizes, we consider a dust uniformly scattered through an expanding space, with non-gravitational interactions (radiation pressure) becoming more important in the past and less important in the future. This picture is then deliberately perturbed with features found by astronomers, and those perturbations are studied for their impact. Most remain local, a scale far far from cosmological.
Informally, this means "We don't care what happens inside individual galaxies, each of which is just one mote of the cosmological dust, and we track the components generating the energy-density of a typical point in space as the dust -- or its various components -- dilute with the expansion, or grow denser as we look into the deep past".
1/2
2/2
Some years ago there was no reason to think that the dust was diluting away with any driver other than some single impulse in the distant past. An initial acceleration, followed by an eternity of inertial motion. More recently evidence has tended to disfavour purely inertial motion, driving the study of possible mechanisms for (and expressions of) ongoing acceleration.
A strong enough violation of the cosmological principle -- that there is something unexpected and atypical about the local neighbourhood our galaxy cluster is in -- might drive us back to a purely inertial expansion, if that atypicality is causing us to mistake a local gravitational acceleration for a cosmological one. This is the topic of the Hossenfelder blog entry.
However, one possible result is that there is something unexpected about the gravitation in the local neighbourhood, but that it applies in other local neighbourhoods too, including those containing extremely bright sources like quasars, returning us to the problem of accelerated expansion. Real proposals that are under investigation include the dynamical outflow of gas and stars from galaxy clusters, driven by the internals of these clusters and the gravitational influence of neighbouring overdensities (our "local hole" is adjacent to several including the Shapley Supercluster, about 231 Mpc distant). Such processes over cosmological timescales may serve to drive galaxy clusters towards typicality.
There are also many open questions about the intermediate regime between the cosmological scale and the galactic scale each of which can be studied with a much more easy to work with approximation of the full theory of General Relativity. z ~ 0.04-0.55 - ~ 100-250 Mpc is right in that intermediate regime. The growth of our theoretical toolbox may resolve some blurry problem at the length scales that are at the root of the arguments in several of the papers Hossenfelder's blog post refers to. The result might be that the allegedly unexpected local phenomenon ("the local hole") should have been expected after all. See https://astrobites.org/2021/09/01/gravity-on-all-scales/ for some details.
Some years ago there was no reason to think that the dust was diluting away with any driver other than some single impulse in the distant past. An initial acceleration, followed by an eternity of inertial motion. More recently evidence has tended to disfavour purely inertial motion, driving the study of possible mechanisms for (and expressions of) ongoing acceleration.
A strong enough violation of the cosmological principle -- that there is something unexpected and atypical about the local neighbourhood our galaxy cluster is in -- might drive us back to a purely inertial expansion, if that atypicality is causing us to mistake a local gravitational acceleration for a cosmological one. This is the topic of the Hossenfelder blog entry.
However, one possible result is that there is something unexpected about the gravitation in the local neighbourhood, but that it applies in other local neighbourhoods too, including those containing extremely bright sources like quasars, returning us to the problem of accelerated expansion. Real proposals that are under investigation include the dynamical outflow of gas and stars from galaxy clusters, driven by the internals of these clusters and the gravitational influence of neighbouring overdensities (our "local hole" is adjacent to several including the Shapley Supercluster, about 231 Mpc distant). Such processes over cosmological timescales may serve to drive galaxy clusters towards typicality.
There are also many open questions about the intermediate regime between the cosmological scale and the galactic scale each of which can be studied with a much more easy to work with approximation of the full theory of General Relativity. z ~ 0.04-0.55 - ~ 100-250 Mpc is right in that intermediate regime. The growth of our theoretical toolbox may resolve some blurry problem at the length scales that are at the root of the arguments in several of the papers Hossenfelder's blog post refers to. The result might be that the allegedly unexpected local phenomenon ("the local hole") should have been expected after all. See https://astrobites.org/2021/09/01/gravity-on-all-scales/ for some details.
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://academic.oup.com/mnras/article/476/1/1384/4848298
https://academic.oup.com/mnras/article/461/3/2929/2608669
https://www.sao.ru/Doc-k8/Science/Public/Bulletin/Vol76/N3/A... (this one is available only in Russian for now)
https://pos.sissa.it/335/039/
https://academic.oup.com/mnras/article/476/1/1384/4848298
https://academic.oup.com/mnras/article/461/3/2929/2608669
https://www.sao.ru/Doc-k8/Science/Public/Bulletin/Vol76/N3/A... (this one is available only in Russian for now)
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
(Link to earlier comment of mine summarizing what I think is wrong with the established mentality)
https://news.ycombinator.com/item?id=27399696
[deleted]
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
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
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?
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?
Per Sabine H on YouTube ( https://youtu.be/JETGS64kTys ), the cosmological constant might be smaller than called for in current cosmology. That would agree with some other observations.
[deleted]
> 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.
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.
> Don't do this.
Do not do that.
Do not do that.
You see it everywhere really. Military and politicians and government orgs all do it to embarrassing lengths too
They also call things polintelcom and codenames like eschelon and prism, doesnt mean it’s great practice for us
Btw ESCHELON and Five Eyes coordination existed for so long and people only woke up when Snowden revealed prism
Btw ESCHELON and Five Eyes coordination existed for so long and people only woke up when Snowden revealed prism
Dude I’m typing on my phone and autocorrect doesn’t know “cosmological”. There, I spelled it out.
> Rather than saying that laws of physics are not space-homogeneous.
No one is saying that, and if the cosmological principle falls, it does not imply that in the least. It just means we need to revisit our assumptions about things like hyperinflation, dark matter, etc. Even more exciting, it may mean we need to look for the remnants of a force active during the initial inflation of the universe, that can account for the non-uniformity of matter's distribution.
No one is saying that, and if the cosmological principle falls, it does not imply that in the least. It just means we need to revisit our assumptions about things like hyperinflation, dark matter, etc. Even more exciting, it may mean we need to look for the remnants of a force active during the initial inflation of the universe, that can account for the non-uniformity of matter's distribution.
Hmm, but if the principle comes with a model-dependent length scale, that experimentally looks wrong, why should I discard the principle when it might as well be an incomplete model?
Or frankly inaccurate estimation, my understanding is that it is extremely hard to actually sully simulate the lambda-CDM model from Big Bang.
Or frankly inaccurate estimation, my understanding is that it is extremely hard to actually sully simulate the lambda-CDM model from Big Bang.
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?
The fun question is then: is the throat of the black hole that contains our universe also in our universe?
Side tangent: Why are most of her numbers, except dates, spelled out? Is this some convention specific to her country of origin or something?
This is a transcript of the video embedded below. Some of the explanations may not make sense without the animations in the video.
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).
Yes, but a German billion isn't the same as an American billion either... .
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.
> 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.
Another problem with the standard model is attributing the cosmological redshift to the Doppler effect.
could you pls elaborate on that?
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 posted this 2 months ago:
https://colab.research.google.com/drive/1K1qoUFvqZp1fWbpcKJW...
https://colab.research.google.com/drive/1K1qoUFvqZp1fWbpcKJW...
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.
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.
"Tired light" has failed other tests, so it's probably not the answer.
How so?
Considering all the data on redshift we have, tired light fits. Not galactic recession.
Rough calculations https://docs.google.com/spreadsheets/d/1HI61-pDIzzSItw48K0ga...
Data from https://ned.ipac.caltech.edu/Library/Distances/
Considering all the data on redshift we have, tired light fits. Not galactic recession.
Rough calculations https://docs.google.com/spreadsheets/d/1HI61-pDIzzSItw48K0ga...
Data from https://ned.ipac.caltech.edu/Library/Distances/
Galaxies are either approaching or receding from our perspective. How could they possibly be stuck in some "place"? Your theory makes no sense.
How do you know?
How do I know that two objects are either receding or approaching? Because it's obvious. Think about it yourself.
Edit: ah, wait, your theory says that approaching objects look the same as receding ones. I think you need to justify that.
Edit: ah, wait, your theory says that approaching objects look the same as receding ones. I think you need to justify that.
You misread.
The cosmological redshift is not attributable to galaxies receding.
The cosmological redshift is photons losing energy as they forge a path through the gravitationally connected universe. It's the cost of traveling.
Total redshift = Cosmological redshift (photon forging a path through spacetime) + Doppler redshift (for example, Andromeda drifting toward us) + Gravitational redshift (like how Sun-to-Earth photons are redshifted because the Sun is more massive)
The cosmological redshift is not attributable to galaxies receding.
The cosmological redshift is photons losing energy as they forge a path through the gravitationally connected universe. It's the cost of traveling.
Total redshift = Cosmological redshift (photon forging a path through spacetime) + Doppler redshift (for example, Andromeda drifting toward us) + Gravitational redshift (like how Sun-to-Earth photons are redshifted because the Sun is more massive)
Since you seem to have a lot of energy to invest in this theory space, why not try your hand at explaining the SDSS-III BOSS results? If you make any progress on that, try SPIDERS and TDSS and explain at least some of the apparent BAOs and high-z = low Tolman surface brightness.
If you're really intrepid, you could try explaining the narrow lines of the Lyman-\alpha forest, and try your hand at predicting it for the background object (or, if you really dig down into your theory, whatever your explanation for the quartet of images at the edge of this structure) in https://research.ast.cam.ac.uk/lensedquasars/indiv/2M1310-17...
Additionally, why is the CMB an almost perfect blackbody spectrum and why is it extremely isotropic? This is a key problem if you plan to retain photon number while depressing photon energy.
While you're there, what is the value of the constant k in your magic equation, and how is it determined? How do you relate this to cosmological neutrino mass constraints in the Mega-Z LRG dataset found by several groups including (slides) http://www.homepages.ucl.ac.uk/~ucapola/Lahav_neutrino2016_8... What is your idea make the hot dark matter vanish and/or fail to couple with your proton mass term?
I don't think that this is a priori unachievable, but it is very much in the land of "show a realistic plan for your work that demonstrates engagement with several public datasets", and is a lot of work for a single author. I would suggest an initial thesis, roughly masters level, with a plan for follow-on work evolving from that initial target. Several widely-cited cosmologists having already had their doctoral dissertations accepted tried their hands at series of individual papers on the back of smaller datasets in the mid 20th century and largely retreated from technical problems in the coupling of emitted photons to specific intervening radiation fields. I don't think their approaches will necessarily help yours, since your equation (your thesis should cite its origin, even if it is a self-cite) does not have an explicit coupling term.
Whether or not you complete this type of project or even have it looked at by anyone else, it is certain that the process of writing it more formally than short Hacker News comments will clarify your thinking. You'll also probably run into some interesting and still technically open problems, and it would be a win for everyone if you helped further resolve some of those.
If you're really intrepid, you could try explaining the narrow lines of the Lyman-\alpha forest, and try your hand at predicting it for the background object (or, if you really dig down into your theory, whatever your explanation for the quartet of images at the edge of this structure) in https://research.ast.cam.ac.uk/lensedquasars/indiv/2M1310-17...
Additionally, why is the CMB an almost perfect blackbody spectrum and why is it extremely isotropic? This is a key problem if you plan to retain photon number while depressing photon energy.
While you're there, what is the value of the constant k in your magic equation, and how is it determined? How do you relate this to cosmological neutrino mass constraints in the Mega-Z LRG dataset found by several groups including (slides) http://www.homepages.ucl.ac.uk/~ucapola/Lahav_neutrino2016_8... What is your idea make the hot dark matter vanish and/or fail to couple with your proton mass term?
I don't think that this is a priori unachievable, but it is very much in the land of "show a realistic plan for your work that demonstrates engagement with several public datasets", and is a lot of work for a single author. I would suggest an initial thesis, roughly masters level, with a plan for follow-on work evolving from that initial target. Several widely-cited cosmologists having already had their doctoral dissertations accepted tried their hands at series of individual papers on the back of smaller datasets in the mid 20th century and largely retreated from technical problems in the coupling of emitted photons to specific intervening radiation fields. I don't think their approaches will necessarily help yours, since your equation (your thesis should cite its origin, even if it is a self-cite) does not have an explicit coupling term.
Whether or not you complete this type of project or even have it looked at by anyone else, it is certain that the process of writing it more formally than short Hacker News comments will clarify your thinking. You'll also probably run into some interesting and still technically open problems, and it would be a win for everyone if you helped further resolve some of those.
Cut the sarcasm because it's going to backfire.
That there are galaxies that appear more frequently at 500 million light-years from each other, is the raw fact. I've read the papers that say that raw fact is proof of big bang LCDM, but that's not actually true. It's not "if and only if" proof, because those papers presuppose the big bang is true and squish the "500 million light-years" observation into their model. They don't consider the possibility of an eternal, eternally evolving universe where 500 million light-years might be an interesting peak of a distribution coming from some interaction of charge and gravity at large scales. Something like chemistry, but at galactic scales.
The cosmic background radiation is likewise not "if and only if" proof of the big bang model. In fact, non-expansionary, non-big-bang models predicted a cosmic temperature around 3K 50 years before Penzias and Wilson. For some reason, this history gets little coverage. https://en.wikipedia.org/wiki/Cosmic_microwave_background#Ti.... There's also a curious coincidence that 2.7K is related to 1/3 electron energy density when in equilibrium with its surroundings. https://twitter.com/sahil5d/status/1413375131078914055 ^ not a fact, just speculation.
k is Coulomb's constant. F=kqq/r^2.
The plot of all known redshift data fits photon hubbling (continuous photon decay) (tired light) more accurately than galactic recession. https://docs.google.com/spreadsheets/d/1HI61-pDIzzSItw48K0ga...
I could spend lots of time whacking moles, but instead I'm fixing the problem at the root, and that problem is interpreting the cosmological redshift as galactic recession. The reason the academic establishment 100 years ago claimed the redshift was the Doppler effect of galaxies receding, was that it was the only "generally accepted mechanism" at the time. That bug in the code has been covered up with patches and patches of convoluted logic for 100 years. Like "space expanded faster than the speed of light". How people swallowed that one, I'll never know.
Gotta fix the bug at the root. Then talk about the rest like dark matter, dark energy, baryon acoustic oscillations.
That there are galaxies that appear more frequently at 500 million light-years from each other, is the raw fact. I've read the papers that say that raw fact is proof of big bang LCDM, but that's not actually true. It's not "if and only if" proof, because those papers presuppose the big bang is true and squish the "500 million light-years" observation into their model. They don't consider the possibility of an eternal, eternally evolving universe where 500 million light-years might be an interesting peak of a distribution coming from some interaction of charge and gravity at large scales. Something like chemistry, but at galactic scales.
The cosmic background radiation is likewise not "if and only if" proof of the big bang model. In fact, non-expansionary, non-big-bang models predicted a cosmic temperature around 3K 50 years before Penzias and Wilson. For some reason, this history gets little coverage. https://en.wikipedia.org/wiki/Cosmic_microwave_background#Ti.... There's also a curious coincidence that 2.7K is related to 1/3 electron energy density when in equilibrium with its surroundings. https://twitter.com/sahil5d/status/1413375131078914055 ^ not a fact, just speculation.
k is Coulomb's constant. F=kqq/r^2.
The plot of all known redshift data fits photon hubbling (continuous photon decay) (tired light) more accurately than galactic recession. https://docs.google.com/spreadsheets/d/1HI61-pDIzzSItw48K0ga...
I could spend lots of time whacking moles, but instead I'm fixing the problem at the root, and that problem is interpreting the cosmological redshift as galactic recession. The reason the academic establishment 100 years ago claimed the redshift was the Doppler effect of galaxies receding, was that it was the only "generally accepted mechanism" at the time. That bug in the code has been covered up with patches and patches of convoluted logic for 100 years. Like "space expanded faster than the speed of light". How people swallowed that one, I'll never know.
Gotta fix the bug at the root. Then talk about the rest like dark matter, dark energy, baryon acoustic oscillations.
As opposed to what?
As opposed to one of "tired light" models.
Light is not immortal, so it loses some energy with time. E.g. gravitational noise can affect photon energy, or photon can lose some energy to medium due to friction, or photon can lose some energy because of truncation of ideal sinusoidal wave at Planck scale, or speed of light is a bit slower than c (because light arrived 16 seconds later than gravitational waves, when gravitational waves were discovered), thus photon is not frozen in time and expands at very slow rate.
Light is not immortal, so it loses some energy with time. E.g. gravitational noise can affect photon energy, or photon can lose some energy to medium due to friction, or photon can lose some energy because of truncation of ideal sinusoidal wave at Planck scale, or speed of light is a bit slower than c (because light arrived 16 seconds later than gravitational waves, when gravitational waves were discovered), thus photon is not frozen in time and expands at very slow rate.
The standard argument against 'tired light' is that it should lead to scattering of light from more distant objects, but this has not been observed in the data.
The standard argument is a straw man argument. Tired light is not photons getting scattered, and is not photons bumping into stray electrons.
Tired light is because there is a cost to traveling through spacetime. The photon is warping the shape of all the universe mass around it. The photon is doing work.
Tired light is because there is a cost to traveling through spacetime. The photon is warping the shape of all the universe mass around it. The photon is doing work.
The intensity of scattering is proportional to loss of energy. It is impossible to detect such low scattering level in our visible Universe because it is full of gasses and dust, which created many many orders of magnitude stronger scattering, which is still hard to notice except for very bright objects near to dense clouds of dust. It's not possible to confirm or disapprove this argument yet.
Moreover, if we are talking about friction and medium (the Ether), then it was predicted long time ago[1], that discussion will be resolved in favor of Ether when Higgs field will be discovered, because Higgs field must be present everywhere, like Ether, and because medium is required for transverse waves to propagate. Discovery of Higgs boson and Higgs field was announced in 2012, so discussion is resolved, but we still call the medium as (physical, quantum) vacuum, like we still call atom as atom («unbreakable») after breaking it, or we use «-» for presence of electrons instead of absence of electrons.
(non-native speaker)
[1]: https://physicstoday.scitation.org/doi/10.1063/1.882562
Moreover, if we are talking about friction and medium (the Ether), then it was predicted long time ago[1], that discussion will be resolved in favor of Ether when Higgs field will be discovered, because Higgs field must be present everywhere, like Ether, and because medium is required for transverse waves to propagate. Discovery of Higgs boson and Higgs field was announced in 2012, so discussion is resolved, but we still call the medium as (physical, quantum) vacuum, like we still call atom as atom («unbreakable») after breaking it, or we use «-» for presence of electrons instead of absence of electrons.
(non-native speaker)
[1]: https://physicstoday.scitation.org/doi/10.1063/1.882562
Photon hubbling, tired light. The photon is doing work as it moves through spacetime. Modeled as E_t / E_0 = e^(-Ht), where H is Hubble's constant, and t is time of travel.
In honor of weekend HN: https://xkcd.com/1758/
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-scient...
[2]: https://vimeo.com/189355968
«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-scient...
[2]: https://vimeo.com/189355968
If even the Cosmological constant is debunked,there's truly no rules to what's possible.
> 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".
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".
(1/H * c) = (1/α * ke^2 / (electron mass * c^2)) *
(h / (proton mass * c * pi/2)) / (2G * proton mass / c^2)
What does that mean in this context? How does it relate to the cosmological principle in the article?
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.
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.
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?
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?
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.
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.
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.
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.
After constructing a better diagram that lens idea looks false too. Similar triangles win again.
Is this a case of science advancing one funeral at a time? We have to wait for the dark energy "establishment" do die off?