3.3 BLY Galaxy Arc Discovered...

[WilliamPaolini]

This is quite interesting. An "apparent" discovery of a concentrated arc of galaxies 3.3 billion LY long at 9.2 BLY distant -- it dwarfs other large structures like the Sloan Great Wall and the South Pole Wall and is 1/15th the radius of the observable universe! What makes it interesting is that according to the Standard Model something like this should not exist because it would reflect a universe that is not generally homogeneous in nature and distributed more or less evenly around the universe (a guiding principle of the Standard Model). Right now it is being called the Giant Arc.

https://www.star.uclan.ac.uk/~alopez/aa ... elease.pdf

[notFritzArgelander]

Thanks for the post. It certainly is amusing and interesting. It is only a press release, though and so subject to a little hype. It is difficult to challenge the homogeneity, isotropy, etc. of the standard model of cosmology, for instance. Those of us who think that the standard model is doing really well are not going to be losing sleep over it. There are two reasons for continued confidence in the standard model.

1) The standard model only needs homogeneity and isotropy on SOME length scale with smaller scales averaging out. There is nothing in the standard model that requires a certain size that is observable for the homogeneity and isotropy to be found. The model could equally well work with an averaging scale larger than the size of the observable universe and I for one would be OK with that.

2) Homogeneity and isotropy of cosmology is deeply linked to the ongoing validity of conservation of momentum and angular momentum. The fact that you can "start your clock" at any initial value is linked to conservation of energy. Homogeneity, isotropy, and initial time invariance are connected to conservation laws via Noether's Theorem.

https://en.wikipedia.org/wiki/Noether%27s_theorem

If and only if Noether's Theorem is true we have conservation laws and physics is possible. Noether's Theorem is true if and only if there is some scale on which the universe is homogenous and isotropic.

[notFritzArgelander]

Here's an added snippet. There are several structures that indicate that the homogeneity length scale is larger than Yadav's simulation predicts.

https://en.wikipedia.org/wiki/Cosmologi ... sistencies

The prediction by Yadav et al that the homogeneity scale is 260/h Megaparsecs is model dependent. If the reality of larger scale structures is born out folks will just have to look at Yadav's simulations and see what went wrong. Observations can falsify Yadav's number but it's hard to see how the cosmological principle of homogeneity and isotropy can be falsified with out violating conservation laws.

[WilliamPaolini]

This is just yet another chipping away for the standard model IMO. There are a number of observations not fitting too nicely. I think it is inevitable that as we discover more, the old concepts will fall by the wayside - and this is what we have seen historically. So IMO these little glitches are just the first signs of impending change. The frustrating part of it all, for me at least, is that so many theories over time get modified and adapted, sometimes significantly, while retaining their same name giving people the impression of a static nature to the theory. Would be nice if they gave them version numbers every time they adapted and changed them. E.g., Darwin's evolutionary theory dramatically changed when his original ideas were merged with ideas from genetics to become the Modern Synthesis, so the current understanding of evolution is quite a bit more dynamic than what Darwin proposed even though the name remains unchanged leading people to think it is the same theory. Sure, foundationally it may be similar, but what is now on top of that foundation is quite a bit different than Darwin could have ever imagined since much of it is based on science that did not exist in his day.

[notFritzArgelander]

Point well taken about theories and, heck, things being more dynamic than our language permits. Nevertheless, Darwin’s key insight about the adaptation of species remains. In addition this work pointing to a larger than some folks have thought homogeneity length scale is not by any means a challenge to the standard model of cosmology.

Heraclitus’s observation that you cannot step into the same river twice is correct but it’s impractical to rename the rivers every time there’s a change. It would make cartography impossible.

Similarly conservation laws (via Noether’s theorem) require homogeneity and isotropy on some larger length scale. The measurements that push that scale larger are a minor quibble. Like naming rivers for cartography every time they change, declaring the universe to be inhomogenous on all length scales is equivalent to making physics impossible.

[turboscrew]

I think, future will show...

[notFritzArgelander]

I think, future will show...

Maybe not? If the length scale on which the universe is homogenous and isotropic is larger than the size of the observable universe then it will never show. If there is not even a huge length scale on which the universe is homogenous and isotropic then physics with conservation laws is impossible.

[turboscrew]

I think, future will show...

Maybe not? If the length scale on which the universe is homogenous and isotropic is larger than the size of the observable universe then it will never show. If there is not even a huge length scale on which the universe is homogenous and isotropic then physics with conservation laws is impossible.

This far it has looked like the conservation laws hold. Maybe in the future we know more, but in the mean time, BAU seems to work quite well. And we don't cast away physics we have, if we don't have anything better to replace it with.
Nothing is definitely not better.

It still rains from the sky towards the ground.

[WilliamPaolini]

This far it has looked like the conservation laws hold. Maybe in the future we know more, but in the mean time, BAU seems to work quite well. And we don't cast away physics we have, if we don't have anything better to replace it with.

I am quite certain that in the future we will know more. 100-200 years from now what we are discussing will probably be seen as naive at best. And no, we should not throw away the physics we have built today. But we also should not consider it anything other than a temporary understanding based on the limitations of observation abilities of the day (a time-based constraint), and the limitations of the reasoning ability of our brains (a species constraint). Given the latter, unlikely that whatever framework we arrive at will be the reality of it all. It will just be the reality as we are capable of understanding it.

[turboscrew]

"But we also should not consider it anything other than a temporary understanding based on..."
To my understanding, that's what natural sciences are.
I don't think we have any theory in natural sciences, that we can say, for certain, that the theory is totally right and the ultimate truth (whatever that is).
All the theories are good or even better models of how things might be.
(Goodness meaning mostly predictive power in different situations.)

[notFritzArgelander]

This far it has looked like the conservation laws hold. Maybe in the future we know more, but in the mean time, BAU seems to work quite well. And we don't cast away physics we have, if we don't have anything better to replace it with.

I am quite certain that in the future we will know more. 100-200 years from now what we are discussing will probably be seen as naive at best. And no, we should not throw away the physics we have built today. But we also should not consider it anything other than a temporary understanding based on the limitations of observation abilities of the day (a time-based constraint), and the limitations of the reasoning ability of our brains (a species constraint). Given the latter, unlikely that whatever framework we arrive at will be the reality of it all. It will just be the reality as we are capable of understanding it.

I am also quite certain that in the future we will know more. Where I differ is from ideas like "100-200 years from now what we are discussing will probably be seen as naive at best". I think that belief is rather wishful thinking and also rather naive. Sure, there are problems to be solved in both the Standard Model of Particle Physics and the ΛCDM model of cosmology. But what are the resources needed to get a handle on them? Progress is slowing down because the resource costs of experiments are growing. Exponential growth is not sustainable and we are already seeing a slowdown in theoretical progress because the experiments cost so many resources. Some physicists are even arguing that we can't afford another accelerator.

For the Standard Model of Particle Physics the energy that is needed to be reached to really get a good grasp on particle physics is estimated to be the energy at which the electromagnetic, weak, and strong interactions are unified, the "Grand Unification Energy". It lies at a factor of 10^12 above what the LHC can produce. Continued progress is going to have to come from more indirect smaller scale experiments like the muon g-2 results from Fermilab and astrophysical sources. All this means is that progress is going to become increasingly tough the more we know.

https://en.wikipedia.org/wiki/Grand_unification_energy

For the ΛCDM model of cosmology the prospects are even more challenging since the development of a "quantum gravity" is necessary. The energy scale for that is several orders of magnitude higher. The Planck energy is even higher than the GUT energy.

So I think that there is no basis for irrational faith in rampant progress. Given the resource costs of probing such high energies in a lab, given that astrophysical data from "natural particle accelerators" is often messy and difficult to interpret, further progress is going to be increasingly tough especially on fundamental questions.

IRL I was trained as a theoretical astrophysicist and did a little before changing career. I have always kept up, though. The thing that scares theoreticians is that there is a long stretch of physics desert before us.

https://en.wikipedia.org/wiki/Desert_(p ... )#Evidence

I hope that progress, though slowed by resource constraints, can be made through exceptionally clever use of experiments like muon g-2 and astrophysical particle detectors.

One thing I am certain of though is that Noether's Theorem is an absolute requirement for physics to be possible. The large scale homogeneity and isotropy of space is a mathematical requirement for Noether's Theorem. The invention of a physics that violates homogeneity and isotropy of space of some large length scale is mathematically forbidden.

I did not lightly call out the hype in the press release link of the original post. I accept (provisionally) the finding that there is a huge structure that is larger than some simulations have suggested as the length scale on which homogeneity and isotropy holds. It is illogical to put forward that this means that the universe is inhomogeneous and anisotropic. The only reasonable interpretation )if the result is correct) is that the length scale on which the universe appears homogenous and isotropic must be even larger.

The result does not have a peer reviewed paper yet. The original presentation is here:



Unfortunately there is excessive glibness and hype about a "challenge to the standard model". All that will be needed for this to be explained within the standard model is some tweaking.

I'm perfectly content that this shows that the length scale for homogeneity and isotropy has to be larger than previous estimates. That's fine. But the claim that it shows that the universe is inhomogeneous and anisotropic on ALL length scales is false and is not supported by the press release or the presentation. The claim that someday we will know better physics than allowed by Noether's Theorem is best treated as a conspiracy theory. What's next? A Flat Earth cosmology?

[WilliamPaolini]

This far it has looked like the conservation laws hold. Maybe in the future we know more, but in the mean time, BAU seems to work quite well. And we don't cast away physics we have, if we don't have anything better to replace it with.

I am quite certain that in the future we will know more. 100-200 years from now what we are discussing will probably be seen as naive at best. And no, we should not throw away the physics we have built today. But we also should not consider it anything other than a temporary understanding based on the limitations of observation abilities of the day (a time-based constraint), and the limitations of the reasoning ability of our brains (a species constraint). Given the latter, unlikely that whatever framework we arrive at will be the reality of it all. It will just be the reality as we are capable of understanding it.

I am also quite certain that in the future we will know more. Where I differ is from ideas like "100-200 years from now what we are discussing will probably be seen as naive at best". I think that belief is rather wishful thinking and also rather naive. Sure, there are problems to be solved in both the Standard Model of Particle Physics and the ΛCDM model of cosmology. But what are the resources needed to get a handle on them? Progress is slowing down because the resource costs of experiments are growing. Exponential growth is not sustainable and we are already seeing a slowdown in theoretical progress because the experiments cost so many resources. Some physicists are even arguing that we can't afford another accelerator. ...

I don't think my statement is naive at all because it is based mostly on my readings of authors in science from more than 100 years ago. I very much enjoy picking up very old books to read the actual thinking of the day (as opposed to some current day internet treatise on the past). Even from works as little as 100 years ago the best scientific contentions of the day are "fun" to read in light of what we know about those topics today. It is the historical pattern of scientific understanding over time, so not conjecture or naivete. So it is always refreshing for me when I see articles like the one I posted as they are often just the small markers of the decade to century long change in thought on a topic that is shaping as we discover more about that which we thought we knew. Nothing negative relative to the process of science in all this as all theory, even when the scientific community's consensus is overwhelmingly behind it, never means it is the reality of the situation but always is just our best deduction based on what we know at the moment and will almost certainly undergo significant change over time. So in that light, just about any theory that is put forth, supported or not, is more or less a "that's nice" for me as I know it will inevitably be much further from the reality of the situation when examined in the light of what will be known in the future. And then of course whatever the future understandings reveal they will always hit that wall of the box that the homo sapiens brain is limited to in understanding and conceptualizing. As a result of all this, I for one can never get too excited about any current day theory.

As a side note on reading ancient works, some ancient Roman writers often amaze me on how sophisticated their thinking was...often much more than what I typically read from current day brighter minds. Would be interesting to have some of those folks transplanted to today :Think:

[notFritzArgelander]

I am quite certain that in the future we will know more. 100-200 years from now what we are discussing will probably be seen as naive at best. And no, we should not throw away the physics we have built today. But we also should not consider it anything other than a temporary understanding based on the limitations of observation abilities of the day (a time-based constraint), and the limitations of the reasoning ability of our brains (a species constraint). Given the latter, unlikely that whatever framework we arrive at will be the reality of it all. It will just be the reality as we are capable of understanding it.

I am also quite certain that in the future we will know more. Where I differ is from ideas like "100-200 years from now what we are discussing will probably be seen as naive at best". I think that belief is rather wishful thinking and also rather naive. Sure, there are problems to be solved in both the Standard Model of Particle Physics and the ΛCDM model of cosmology. But what are the resources needed to get a handle on them? Progress is slowing down because the resource costs of experiments are growing. Exponential growth is not sustainable and we are already seeing a slowdown in theoretical progress because the experiments cost so many resources. Some physicists are even arguing that we can't afford another accelerator. ...

I don't think my statement is naive at all because it is based mostly on my readings of authors in science from more than 100 years ago. I very much enjoy picking up very old books to read the actual thinking of the day (as opposed to some current day internet treatise on the past). Even from works as little as 100 years ago the best scientific contentions of the day are "fun" to read in light of what we know about those topics today. It is the historical pattern of scientific understanding over time, so not conjecture or naivete. So it is always refreshing for me when I see articles like the one I posted as they are often just the small markers of the decade to century long change in thought on a topic that is shaping as we discover more about that which we thought we knew. Nothing negative relative to the process of science in all this as all theory, even when the scientific community's consensus is overwhelmingly behind it, never means it is the reality of the situation but always is just our best deduction based on what we know at the moment and will almost certainly undergo significant change over time. So in that light, just about any theory that is put forth, supported or not, is more or less a "that's nice" for me as I know it will inevitably be much further from the reality of the situation when examined in the light of what will be known in the future. And then of course whatever the future understandings reveal they will always hit that wall of the box that the homo sapiens brain is limited to in understanding and conceptualizing. As a result of all this, I for one can never get too excited about any current day theory.

As a side note on reading ancient works, some ancient Roman writers often amaze me on how sophisticated their thinking was...often much more than what I typically read from current day brighter minds. Would be interesting to have some of those folks transplanted to today :Think:

We'll have to agree to disagree about how naive current science will look a hundred years from now. The last 100-200 years were the golden age of research when experiments were relatively easy. Tougher times are coming. It's naive to think otherwise as I've reasoned above.

The fact remains that this result can be likely brought into complete accord with the standard model cosmology with a few judicious tweaks. It's really not that surprising. The claims of the OP link are hype and exaggeration. It's an unfortunate consequence of the slowing of research due to resource competition that excess self promotion is rampant.

All theory is provisional, of course. Any claim to an absolutely true theory is to be disregarded as hype also.

However there are rules of logic and mathematics that must be followed. It is, as I said, illogical to say that this result implies that the universe is inhomogeneous and anisotropic on length scales larger than observed. The cosmological principle of homogeneity and isotropy of the universe isn't "just a theory". It's baked into the mathematics that all past and future theories must obey. All alternative theories of gravity satisfy Noether's Theorem. All quantum field theories do too.

You might not recognize or appreciate that Noether's Theorem is essentially the foundation of any physical theory. The authors involved in this work might need a refresher course in mathematical physics too. But that doesn't alter the facts of the case which are:

1) this work, if upheld, means ONLY that the homogeneity and isotropy length scale is larger than previously observed and estimated
2) the claim that it's a foretaste of the standard model being overthrown is hype and salesmanship.

[notFritzArgelander]

PS Just to clarify, as a theoretician I've never said that theories are final or Absolutely True. They are always subject to falsification by observation. One needs a theory to design any experiment, "experiments" that don't have a theoretical hypothesis to test aren't proper experiments though.

The philosophy of science I find most congenial is Karl Popper's. Experiments cannot "prove" a theory since different theories often predict the same result. But experiments can "falsify" a theory.

This result does not falsify the standard model of cosmology that assumes the universe is homogenous and isotropic. It only falsifies Yadav's model of the length scale on which homogeneity and isotropy obtains. I am certain that someone working within the ΛCDM standard model of cosmology will come up with a better estimate than Yadav's and put the hype to rest.

The assertion that there is no length scale on which the universe is homogenous and isotropic is untestable and unscientific since large parts of the universe are unobservable (i.e. ALMOST ALL of it).

Although the research seems valuable, hyping it beyond what it can logically imply is annoying. I've consistently called out such instances of hype in the past and will continue to do so. I regard it as a duty to perform and take no particular joy in it. It is always disappointing to see scientists act like used car salesmen. But then again when I was active I was criticized as being "too much of a 19th century natural philosopher". It was intended as a criticism but I took it as a compliment.

[chasmanian]

its such a joy for me to read your posts in this thread nFA.

and thank you to the other posters too.

really great thread guys.