HN Reader

In my opinion, this article is misleading at best. "...scans of ancient galaxies gathered by the JWST seem to contradict the commonly accepted predictions of the most widely accepted Cold Dark Matter theory, Lambda-CDM." --> LCDM doesn't predict what galaxies should look like, it simply predicts how much mass is in collapsed structures and that dark matter haloes grow hierarchically. In contrast, with JWST we see light and need to infer what the underlying properties of the system are. It was shown very early on that the theoretical upper limit (i.e. taking all of the gas that is available in collapsed structures and turning it into stars) predicts a luminosity function (i.e. number of galaxies per unit luminosity) that is orders of above what JWST has observed (e.g. https://ui.adsabs.harvard.edu/abs/2023MNRAS.521..497M/abstra...). This means that there is plenty of space within the context of LCDM to have bright and seemingly large and massive galaxies early on. Based on current JWST data at these early epochs, there are really no convincing arguments for or against LCDM because it's highly sensitive to the galaxy formation model that's adopted.

My hangup with MOND is still general relativity. We know for a fact that gravity is _not_ Newtonian, that the inverse square law does not hold. Any model of gravity based on an inverse law is simply wrong.

Another comment linked to https://tritonstation.com/new-blog-page/, which is an excellent read. It makes the case that GR has never been tested at low accelerations, that is might be wrong. But we know for a fact MOND is wrong at high accelerations. Unless your theory can cover both, I don't see how it can be pitched as an improvement to GR.

Edit: this sounds a bit hostile. to be clear, I think modified gravity is absolutely worth researching. but it isn't a silver bullet

Why why why do people share articles with sensational headlines like this? Its no wonder science journalism gets a bad rap. This kind of thing really undermines all the people who are actually trying to communicate science properly.

I wish science reporters would stop using MOND to stand in for all theories for which MOND is the low curvature limit. MOND itself is not covariant and has a lot of other really well known issues which make it obviously a non-starter and more sophisticated theories in the family of General Relativity reproduce MOND like behavior but are better behaved and more plausible.

At the very least the term Modified Gravity or MOG should be used instead of MOND to avoid a lot of pointless back and forth about MOND.

What’s MOND really mean? Here’s the Wikipedia entry https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics

Waiting for Angela Collier to make a video on this, I'm sure many people will forward her this article. MOND is actually a niche in cosmology despite its PR.

Here is what Sean Carroll has to say about MOND…

https://www.preposterousuniverse.com/blog/2011/02/26/dark-ma...

I find this treatment more compelling.

Is there a quantized version of MOND where the increased acceleration is because a quantized unit of gravity will exert force across distances that would otherwise suggest that that the force would be less than a "g quanta" or because maybe quantization "ceilings" more than floors at very large distances? If gravity does have some kind of particle or fundamental quantization like a photon, and basically still exerts at huge or "infinite" distance, does it make sense that it's more likely there's some kind quantization floor or maybe quantization bands or something? Or is it thought that quantization of gravity imposes a limit on distance for the exertion of gravitational attraction? (Or is it thought that that with quantized gravity that what's happening is a decreased rate of "gravitons" interacting between the objects?)

Anyway, a bit clueless about this, just curious what gravitons are supposed to mean for either theory (MOND, LCDM, etc.).

Are any of the MOND theories consistent with this new data also consistent with recent gravitational wave observations? My understanding is that gravitational wave detectors have recently ruled out most plausible MOND theories. The linked paper doesn't seem to discuss this.

For a dark matter researcher’s take on MOND, see this video: https://youtu.be/qS34oV-jv_A

« Stunning evidence » … then later on: « Instead, the readings _seem_ to support a basis for MOND, which _would_ force astronomers and cosmologists to reconsider this alternative and long-controversial theory of gravity. » What’s conditional evidence? I may be missing the overall picture, but I view such writing as non precise at its best.

I follow the lead author, Stacy McGaugh, via his blog where he posts discussions and musings about the latest research into the dark matter vs MOND debate: https://tritonstation.com/new-blog-page/

His arguments are very convincing and relatively clear. I am not an astrophysicist but I have two degrees in physics and have always found the dark matter theory to be lacking -- in absence of any evidence of causation whatsoever, dark matter can only be described trivially as "where we would put matter if we could to make our theory of gravity make sense," which is totally backwards from a basic scientific perspective.

Predictions based on modern MOND postulates are shown to be more and more accurate as our observational instruments continue to improve in sensitivity.

Dark matter is just made up bs if you replace "magic" for dark whenever its mentioned its the same difference - theres no tangable evidence it exists at all.

It shows early galaxies forming way faster and bigger than expected, which kind of shakes up the whole dark matter idea. Seems like it supports the MOND theory—that gravity might not work the way we think. Pretty wild, but it’s still up for debate.

What I find implausible about MOND is the constant a0 (~1.2). Why stick with a measurement based constant instead of exploring a parameter that varies with distance?