Dark Matter or Modified Gravity? A virtual panel discussion Apr. 7th 3pm central time

[RedshiftDrift]

https://neiulibraries.libguides.com/displays/events
"During this 90-minute virtual panel discussion, to be held on Monday, April 7, physicists Scott Dodelson and Stacy McGaugh will address one of the most controversial questions facing contemporary physics: whether or not the standard cosmological model is valid, and in particular, whether evidence supports the existence of dark matter—and/or, whether evidence supports a modification of Newton's laws of gravity."

[genotics]

In anticipation of this online event, I wonder if t his thread would be the appropriate context to seek comment on the state of my project (now in its third year) to establish the notion of inertial induction on a firmer foundation. One of the three papers I am working on is an attempt to apply the concept to the flat rotation curve/RAR problem. There are a few preliminary drafts, supplemented by a script under development to plot results. Of course I rely heavily on AI models for both the research/writing and coding, my role being mainly that of stoker. The rotation curve script will likely require considerable recoding. Martin, would you care to have a look at a draft?

[budrap00]

The syllabus is somewhat misleading in claiming that the discussion will involve "whether or not the standard cosmological model is valid." As is made clear, the discussion will only entail a binary choice between DM and MOND. That restriction to only those two possibilities which only involves one aspect of the standard model means that the standard cosmological model's overall validity is not up for debate. Too bad, cosmology, if it is to be a science, desperately needs that discussion. MOND vs DM is just rearranging the deck chairs on the Titanic.

[genotics]

Some would say that it is like rearranging the chairs once the ship has gone to Davy Jones' locker. Perhaps it is time for a third choice, but it is probably expecting too much that academics should treat the BB as other than dogma.

[RedshiftDrift]

@genotics Roy, "Whether or not the standard cosmological model ($\Lambda{\rm CDM}$) is valid" means that the discussion will be about dark matter while examining only two possibilities: $\Lambda{\rm CDM}$ and MOND within a Big Bang cosmology framework. I agree with @budrap00, the Big Bang model will not be up for debate is this panel discussion.

However, I think that Stacy McGaugh is doing more than rearranging the deck chairs on the Titanic gone to Davy Jones' locker. He is seriously considering using Titanic Lifeboat No. 19, but he doesn't know where this will lead him. My interest in this debate is to find out how McGaugh argues against Dodelson. (I've read Dodelson's book "Modern Cosmology" which is just Big Bang + $\Lambda{\rm CDM}$ nonsense.)

I doubt McGaugh will want to hear about alternatives to MOND, but if your paper on "flat rotation curve/RAR problem" produces similar effects to what McGaugh is modeling with MOND, you might get him interested by sending him your paper. (I don't think Martín López-Corredoira is on GitHub, but I can look at your paper after May 15th if you want...)

For my part, STz produces an optical force that causes an acceleration ${\rm Milgromian} a_0/2 $, and this can be linked to the empirically observed $2\pi a_0 = c H_0$. In listening to McGaugh's arguments, I hope to write the paper in a way that would reassure him that Titanic Lifeboat No. 19 == MOND is supported by physics other than the Big Bang model.

[HanDeBruijn]

@RedshiftDrift .

the empirically observed $2\pi a_0 = cH_0$.

I've asked this before to @sahil5d . How can a factor $(2\pi)$ be empirically observed? Why not instead e.g. $7 a_0 = cH_0$? Is there any theoretical underpinning for the factor $(2\pi)$?

[RedshiftDrift]

@HanDeBruijn
The precise description of this is: what is empirically observed is an acceleration $a_0 = 1.2 \times 10^{-10} \mbox{ m/s}^2 \ \pm 18$%.

There is a theoretical justification for $a_0 = c H_0/(2\pi)$ given in the paper I am writing, so the factor $2\pi$ is empirically observed to within 18%.

(It's taking me a lot more time to write than I had expected. I wasted months trying to solve a hybrid version of the Jeans/Vlasov/Poisson equations before finding a much simpler way to get the answer. You'll get the draft as soon as it's presentable... Peek preview: the factor $2\pi$ is a geometrical factor equal to half the solid angle of a sphere.)

@sahil5d's equation is an assembly of physical quantities that give an equality within the uncertainty on $H_0$. Just like Dirac's large number hypothesis (which also involves $H_0$ via the age of the universe), the equation does not have any theoretical justification.

[LifeIsStrange]

would be nice to talk about quantized inertia too

[LifeIsStrange]

new paper on mond wide binaries
https://arxiv.org/abs/2504.07569

[shafizadehmr]

I miss this event, is there any record?

[ExpEarth]

It was pretty interesting. They posted it here:
https://www.youtube.com/watch?v=AK2GxgwY7_U

[RedshiftDrift]

Following the debate, Stacy McGaugh also wrote this:
https://tritonstation.com/2025/04/17/some-persistent-cosmic-tensions/

[genotics]

Question for Martin:
Could you please respond to the following information request in compact form?

Since López‐Corredoira et al. present their results in terms of the surface density
[
\Sigma(R,z)
]
and convert to vertical acceleration via
[
g_z(R,z)=2\pi G,\Sigma(R,z),
]
could you please extract the following numerical values (with $1\sigma$ uncertainties) as reported at the solar circle ($R=R_\odot$):

\begin{enumerate}
\item The measured surface densities
(\Sigma(R_\odot, z)) (and their errors) at each height
(z = 0.15,;0.30,;0.60,;1.05;\mathrm{kpc}.)
\item The exact radius (R) (and radial bin width (\Delta R)) used for these measurements.
\item Any description of how they convert (\Sigma) into (g_z) (i.e.\ confirmation of the relation (g_z=2\pi G,\Sigma) or any variant thereof).
\end{enumerate}