More Experimental Evidence for MOND

This debate continues to rage on a private MOND mailing list. Since it's private, I won't divulge details here, except to suggest that everyone "hang loose" for a bit longer as the science sausage continues to be made. The choice of quality criteria to be applied when selecting Gaia data is still controversial, and seems to be a significant theme underlying the current debate. No doubt more papers will appear soon.

Vanadium 50 said:

Where I do see a problem is, as I mentioned before, that we cannot test MOND in a terrestrial setting because the gravity of Earth obliterates the effect. But we can test it in wide binaries because for some reason the gravity of the planets does not obliterate the effect.

Huh? Which planets are you talking about? Planets that might be orbiting each of the stars in a wide binary pair?

Vanadium 50 said:

I don't see that as a problem. I have published several experimental papers supporting my side of a controversy. A few have even settled the controversy.

Am I biased? In don't know. I am certainly interested. We have controversy when people draw different conclusions from the same data. If N-1 experiments convice me but not everybody, and I do an Nth experiment that does convince everybody, where is the problem?

Not sure if you are referring to my post. The point I was making is that someone supportive of MOND has now published a paper that claims to very strongly rule it out. Banik still thinks lambda CDM is seriously flawed, but the new paper proves (in the authors view) that nothing close to MOND can be the answer.

PAllen said:

The point I was making is that someone supportive of MOND has now published a paper that claims to very strongly rule it out. Banik still thinks lambda CDM is seriously flawed, but the new paper proves (in the authors view) that nothing close to MOND can be the answer.

Heh, I hope you enjoy watching screeching U-turns in the near future.

Separately, Frederico Lelli (Astrophysicist at INAF) has recently re-emphasized a point he made near the end of this paper about how several different types of physical phenomena all reveal a universal acceleration scale of approximately the same value, although there is no a-priori reason for this.

Among others, he mentions these:

- The Baryonic Tully-Fisher relation,

- The Central Density Relation (applicable at small radii in galaxies),

- The Radial Acceleration Relation (applicable at large radii in galaxies).

In a non-MONDian universe there is no reason why the acceleration scales found in these phenomena should be the same. He points out that this is a strong reason to do research on MOND, analogous to how the appearance of ##\hbar## in disparate contexts was a compelling reason to explore quantum mechanics over 100 years ago.

Vanadium 50 said:

I don't see that as a problem. I have published several experimental papers supporting my side of a controversy. A few have even settled the controversy.

Am I biased? In don't know. I am certainly interested. We have controversy when people draw different conclusions from the same data. If N-1 experiments convice me but not everybody, and I do an Nth experiment that does convince everybody, where is the problem?

It's the opposite here. Banik is a major MOND supporter, and now here he says MOND doesn't work.

Dr. Becky Smethurst chimes in on the new paper:

AndreasC said:

It's the opposite here. Banik is a major MOND supporter, and now here he says MOND doesn't work.

Yeah that's significant and shows integrity of the study?

I say again, wide binaries are a terrible test.

Let's go back to the basics. In the Newtonian word, I have two masses, M and m, separated by a distance r, and for simplicity, let's have them at rest. The heavier feels an acceleration Gm/r and the lighter GM/r and two lines of algebra should convince you momentum is conserved: no external force, and the center of mass doesn't move.

In MOND, the accelerations are GM/r and something else (assuming the acceleration is in the deep MOND domain). I think it is [itex]\sqrt{GMa_0/r}[/itex] but it doesn't matter exactly what it is. The point is now that the center of mass starts to move, with no external force.

Nobody believes this is what happens. Nobody.

I think even the MOND proponents would argue that something must happen to prevent this, and that the equations we use for MOND are probably approximations for real, better-behaved ones.

This is part of the reason I say that MOND has problems with composite objects. (We can discuss why rotation curves are particularly ill-suited to sort this out).

So looking at wide binaries is exactly where we know that MOND prediction needs to be altered. It's just a bad test.

Vanadium 50 said:

In MOND, the accelerations are GM/r and something else (assuming the acceleration is in the deep MOND domain). I think it is [itex]\sqrt{GMa_0/r}[/itex] but it doesn't matter exactly what it is. [...]

That's not how it works. You can't simply add MOND-adjusted fields from different sources -- that gives all sorts of nonsense along the lines you sketched (among others). This has been known for ~40 years (cf. Felten).

Rather, one must first compute the total Newtonian field at the point of interest, and then apply the MONDian adjustment. That's more-or-less what AQUAL does. The problem you mentioned was a primary reason for inventing AQUAL. Unfortunately, it's non-relativistic so not much of a surprise that it's a bit off wrt gravitational lensing.

Vanadium 50 said:

I say again, wide binaries are a terrible test.

Let's go back to the basics. In the Newtonian word, I have two masses, M and m, separated by a distance r, and for simplicity, let's have them at rest. The heavier feels an acceleration Gm/r and the lighter GM/r and two lines of algebra should convince you momentum is conserved: no external force, and the center of mass doesn't move.

In MOND, the accelerations are GM/r and something else (assuming the acceleration is in the deep MOND domain). I think it is [itex]\sqrt{GMa_0/r}[/itex] but it doesn't matter exactly what it is. The point is now that the center of mass starts to move, with no external force.

Nobody believes this is what happens. Nobody.

I think even the MOND proponents would argue that something must happen to prevent this, and that the equations we use for MOND are probably approximations for real, better-behaved ones.

This is part of the reason I say that MOND has problems with composite objects. (We can discuss why rotation curves are particularly ill-suited to sort this out).

So looking at wide binaries is exactly where we know that MOND prediction needs to be altered. It's just a bad test.

I don't mean disrespect but I've noticed you have made a lot of posts where you say this or that is an obvious problem with MOND, or that this or that is not explained etc, whereas you could just read some basic review paper and find the answer. What you are saying here only applies to one formulation in the original, proof of concept paper on MOND. There is a bunch of well known theories that have been subsequently developed that do not violate conservation of momentum. People working on MOND are not so stupid that they didn't even notice the third law is violated for decades.

strangerep said:

That's not how it works.

Which is exactly the point. You need to add something beyond just "here's what we see in rotationally supported galaxies" to get a working microscopic (insofar as one can call individual stars "microscopic")

And now you're trying to test two things.

AndreasC said:

you could just read some basic review paper

What makes you think I haven't?

There is a difference between not reading them and not being convinced by them. I find the arguments very epicyclical. Er...epicycular, Um...like epicycles.

One of PF's faults, especially in BSTM physics, is that it attracts a cheerleading mentality: "Go SUSY! Go MOND! Go X17!". It leaves little room for people to point out problems with both (or all) alternatives.

Wide binaries were a bad test when they supported MOND, and wide binaries were a bad test when they undermined MOND. Lining up on the sidelines based on this is a bad idea.

Vanadium 50 said:

One of PF's faults, especially in BSTM physics, is that it attracts a cheerleading mentality: "Go SUSY! Go MOND! Go X17!". It leaves little room for people to point out problems with both (or all) alternatives.

Rubbish. You seem to have no trouble pointing out such problems as you perceive them. No one is telling you to shut up. Quite the opposite, imho. I'm happy to listen carefully to (well considered, well informed, well explained) points of view.

Vanadium 50 said:

What makes you think I haven't?

There is a difference between not reading them and not being convinced by them. I find the arguments very epicyclical. Er...epicycular, Um...like epicycles.

You're not convinced that what, AQUAL or TeVeS or whatever for example does not have the behavior you said? You can just reproduce the calculation, it's not that hard. Do you think this or the other papers on the WBT didn't address these different models of MOND? They did.

According to this paper, pretty much any kind of MOND people have come up with so far disagrees with the data. This may or may not be true, since there are lots of papers contradicting each other currently. Possibly this will only be conclusively resolved with the next Gaia release. Maybe even later than that. True, it doesn't mean the hard core of MOND is falsified, but, if true, all the models we have so far fail in that regime. This has nothing to do with the fact that MOND has to be modified to fit Newton's third law, because, well, this has been done a million years ago, and those models that recover the third law still fail.

In the same way, if we had the opposite result, it would show that current models of MOND do better than CDM in that regime. This would also be very important.

The fact of the matter is that the MOND law still works on galaxies, but if this is true, the hopes of it also working on slightly smaller scales (scales where people thought it would) are lost. That is, if this is correct. That's all there is to this, I don't understand where the controversy is.

This article today favouring a MOND model over ΛCDM, looking at the Hubble tension and Banik is one of the authors.

https://phys.org/news/2023-12-giant-void-puzzle-universe-expansion.html

EDIT: Paper here,(early Galaxy formation found by JWST is mentioned in the conclusion also) https://academic.oup.com/mnras/article/527/3/4388/7337338?login=false

So the paper favouring MOND 2.11.23 Void/ Hubble tension

Not favouring MOND using wide binary data 3.11.23