Hello Everyone :)
I am a former stress engineer and have been working on discrete calculations for years Passionate about astrophysics and cosmology (especially the absolute vacuum), I’m interested in dark matter models (particularly those used to determine the rotation curve of spiral galaxies).
I’m convinced (though not entirely certain, of course) that the effect of time (billions of years of rotation under the influence of gravitational forces) has shaped our Galaxy (and other spiral galaxies) and has, in a way, “optimized” its mass and shape.
Just as an enginner will do some weight reduction by removing some part of a piece (for plane or car pieces for ex), time has optimized the shape of our galaxy to achieve a higher rotation speed with a lower mass.
Starting from this hypothesis, i have done a N-body simulation of our Galaxy with non axisymettric mass distribution (all bodies are located on the lines of local center of gravity, i.e. on the axis of the galaxy’s arms of our Galaxy, see picture below)
Unlike previous studies, where the total rotation speed is obtained by globally summing all contributions within the Milky Way
My results shows that if we study the rotationnal speed within an arm, some contributions will be positive (some arms will participate to increase the radial acceleration, so the rotationnal speed) while others will decrease it. (Do the opposite)
My conclusion is that, overall, the inner arm contributes to accelerating the rotational movement, while the outer arm slows it down, but always to a lesser extent than the acceleration induced by the inner arm. And this could be the explanation of Rotation curve flatness in the spiral area.
What do you think? Your advice and criticisms are welcome (I do not claim to have the solution nor that my model is better than another, but all dark matter models are disk models and none take into account the shape of the arms inside our Galaxy).
Hi Bertrand, I would tend to agree with you, as what you propose captures the essence of Amitabha Ghosh’s analysis of the problem. See below. The chief difference is that Amitabha posits a velocity dependent term in the gravity equation, such that a forward pull is exerted by faster rotating matter inside a given point on the disc, and a retrograde drag arises from outer, slower moving matter. The servomechanism must be active over long periods in order to achieve the flattening effect, i.e., over the lifetimes of galaxies. I am working on a paper that develops Amitabha’s ideas in a field theoretic form and extends the analysis beyond the razor thin disc idealization to more realistic galaxy morphology, and also addresses RAR and vertical kinematics. I would be happy to share the original article by Amitabha and my draft for comment if you care to have a look.
“A dynamic model of gravitational interaction was proposed earlier which results in a velocity dependent drag. … In the present paper it has been shown that such a velocity dependent inertial induction can act as a servomechanism for distributing matter in rotating spiral galaxies in such a way that flat rotation curves are obtained. A truncated thin disc model has been assumed, but the results are strongly in favour of the proposition.”
@article{Ghosh1988, author = {Ghosh, A. and Rai, S. and Gupta, A.}, year = {1988}, title = {A possible servomechanism for matter distribution yielding flat rotation curves in spiral galaxies}, journal = ApSS, volume = {141}, number = {1}, pages = {1–7}
Hello :) Thanks a lot for this very helpful message
I’ll take a look at Amitabha Ghosh’s analysis (what you quoted, “retrograde drag arises from outer,” is exactly what I had in mind; I would simply add that the inner arms of our galaxy transmit (onto the outer arms) the gravitational force/effect from the center to the tips of the arms). I would be delighted to read your draft (my email address is bertrand-m@hotmail.com) and I will send you my article (currently being reviewed for an astrophysics journal).
Thanks again for your message
@Bertrand7592
I did a naive (Newtonian) study a long time ago to the effects of a rotating bar as an outflowing gravity wave, but not travelling at ‘c’ but at some ‘gravity sound’ speed. (Not arguing that gravity doesn’t propagate at c, but that the arm is like a sound wave would be in air) My aim was not to determine radial velocities, but to show that the spiral arm waves were not necessarily circular waves but could be radial outward waves. Obvious motivation is that the arm is always attached to the end of the bar which would not be with a circular wave. If this sounds useful I might still be able to dig up the maths.
@genotics physics is like a fine-tuned engine that is not so fine-tuned anymore. It’s also missing a few parts. Physics is in dire need of engineers to help them self-correct. :)
@Francois-Zinserling well i am interested by everything linked to the rotationnal motion of our Galaxy :) i also think its not a coincidence that the arms are starting from the inner ring in the locations of bar junctions with inner ring The Bar is the most dense object in our Galaxy and obviously will impact the gravitationnal forces following its axis (if we strictly follow Newton’slaw, it will better accelerate the arms when they are located in the bar’s axis, so it has an impact even far from the center)
PS. Apparently it takes engineers to fix physics.
Engineers to the rescue! You may wish to consult papers by Vukcevic and colleagues on spiral structure, e.g., https://arxiv.org/abs/2112.01245
On Sat, 28 Mar 2026 at 12:22, Francois Zinserling @.***> wrote:
Related: On the origin of MW stellar halo substructures https://arxiv.org/abs/2604.13482
Hello All,
I have finally published my idea here: https://www.scirp.org/journal/paperinformation?paperid=153536
My idea is still simple: over billions of years, time has possessed a sort of unconscious intelligence that enabled it to optimize the shape of our Galaxy—hollowing it out and optimizing its mass and mass distribution, much like engineers do with aeronautical components—thereby allowing for a lower total mass than that of a simple disk with a radially concentric density profile.
Bertrand
@kurtcobay-ops would you say that the “one dimensional” structure of galactic arms helps increase the radial force? After all, gravity from a “line” falls off as $1/r$. (Which is exactly what Milgrom proposes for MOND at small accelerations…)
@RedshiftDrift Hello again :) As I said to you, my explanation is more simple but still keep a 2D model (not 1D) of our Galaxy and its arms. Maybe it will be clearer with the following example (see picture) : For 2 differents stars of our Local (Orion) arm we have nearly the same rotation speed (according to Gaia data, around 220km/s)
What I meant is that an arm is a 1-D structure in a 2-D galaxy model. I am not looking what causes the flat rotation curve (I already know from my calculations), my question is how can so little mass produce such a high rotation velocity?
Instead of basing my description on a calculation like the one you do (which is perfectly fine), I am trying to describe it with general physics (without using a computer): Locally, the sun sees the Sagittarius arm as a 1-D filament at a distance of 3E19, with a gravitational force going approximately as 1/r (ignoring everything else). Since the Sgr-arm is the closest mass, it has the strongest effect. So within my approximation, the sun orbits the galaxy as if the gravitational force had a 1/r law.
I have asked astronomers if they did calculations with a mass distribution that represents the arms, just as you do. They told me that they do but I was never able to find a paper on that. Have you found other papers doing the simulation with arms, or are you the first one?
Oh i see what you mean for the 1d approach. I have cited another study made in 2005 about non axysimetric model but only for Gas inside spiral galaxies (https://doi.org/10.3847/1538-4357/ad87f1) . I think, as I state it in the abstract, that my paper is the first about a N-Body simulation using a 2D static model to retrieve the rotation curves, alongside a non-axisymmetric and “almost entirely” baryonic mass model (I have not found any other paper similar to mine).