Thank you, Thierry

Of course my hypothesis is significant only when a gap between reliably observed masses and by gravitational lensing estimated masses are smaller than multiple of 2. I think that there is space expanding mechanisms showing illusory dark matter too. Taken account that the orbital based galaxy mass calculations can be corrected way up more massive.

Amyhow, it's naiive thought that some wimps or axions could explain the whole, especially we have no clue about them...

The retarded potential effect seen by a cluster is indeed an effect that should be taken into account to be strictly conform with GR.  In practice this effect is small for the required precision, because the ratio of matter speeds (50-300 km/s for a galaxy, 500-2000 km/s for a cluster) to the speed of light (300'000 km/s) is small.  So it is neglected.  

But the technics to take propagation delays  into account is well known when high precision is required, like for the solar system, where the speed ratio is even smaller, but the required precision is higher.  The current popular method is called "Parameterized Post-Newtonian formalism" (PPN).  For an introduction, see the link below. 

In short, astrophysicists are well aware of the problem, but don't think that it is relevant to solving the dark matter problem.

https://en.wikipedia.org/wiki/Parameterized_post-Newtonian_formalism

Thierry, as your theory is non-standard, you need to prove logically and quantitatively your claims.  The way to achieve it is to publish your results in well recognized referred journals.   I found no publication of your part in the standard physics or astrophysics literature.   As you are Editor at the "General Science Journal",  self-publications there  cannot serve as a path to recognition by peers.  I do not remember to ever see a single citation from this journal, so it would be interesting to know its ranking, if it exists, among the journals in the field.

In your reply you write something confusing: "The angular momentum that is present in spinning structures and stars is effectively causing changes by the creation of an anisotripic gravity field upon long-lasting orbits.".    But angular momentum  is unrelated to gravity by definition, it is just a vector product of positions and velocities weighted by mass, and thus is unable in itself to "cause" a gravity field. The source of gravity  in Newtonian theory is mass, and mass-energy in GR.  So what you could argue is that in GR kinetic energy is causing some gravitational field contribution, but certainly not angular momentum.  In the strong gravtational regime, such as near black-holes, so not at all comparable to galaxies and galaxy clusters, space-time drags indeed test particles. This is the Lense-Thirring effect (1918). Its tiny effect around the Earth has been measured and found to follow GR predictions.  So what you say is nothing new, just that this effect is so tiny in galaxies and galaxy clusters that experts in the field know it is negligible and don't need to even discuss it further. If you think otherwise, show why generations of experts have been wrong and quantitatively by how much. For gaining audience it is insufficient to assert the former experts are wrong or "ridicule". 

There is no need of an obscure explanation for understanding astrophysical disks.  The cause of flattness in such disks is energy dissipation in situations where angular momentum is better conserved. In galaxies radiative processes are efficient at exporting energy while inefficient at transporting momentum.  All this has been quantitatively tested by a large number of independent numerical experiments over decades. 

Finally, your last two phrases are just incoherent. If your effect redistributes stars in an unexpected way,  surely the observed stellar distribution in itself would show a problem distinct from stellar kinematics and dark matter.  What is causing the dark matter problem is the combination of stellar distribution (mass density decreases ~exp(-R/h)) with its kinematics (which requires mass-energy density decreasing as R^-2).  If you think the disk rotational kinetic energy is able to explain the difference, you would need rotational speeds close to the speed of light to get any substantial effect, which is obvioulsy contradicted by the known speed of ~0.007 c.  Since kinetic energy is proprotional to the squared velocity,  the speed effect is actually ~10^6 times too small to match your claims.

Thierry, let us stick to the question topic. 

Gravitomagnetism, linked with the finite propagation of gravity disturbances, is a well established effect, nobody contests that.  Heaviside guessed the right equations in the non-GR case.  Later the correct equations in the GR case where worked out, leading among other to the Lense-Thirring effect, verified by experiments.   Experts in the field are well aware of these facts.  Google a bit "gravitomagnetism" to see you are not alone.   But you will not get much attention resurrecting the non-GR theory while the GR theory is better matching facts.

The main weakness in your work is not being quantitative.  If you would apply correctly even the non-GR equations you must  find the speed effect is completely negligible to solve the dark matter problem.  If you stick to vague affirmations while igoring most of literature on the topic, do not expect in return much attention by scientists, they have more urgent problems to investigate.   Compare for example the work of Harihar Behera linked below published the same year as your paper (2005), and see how much more literatrure is dicussed and shown assimilated in Behera's paper.  In the process of building scientific knowledge, citing and assimilating earlier works is very important to be taken seriously.   Showing respect to earlier works and experts is socialy  more efficient than qualifying  them as "ridicule" .

https://arxiv.org/abs/gr-qc/0510003

Thierry: Again if we stick to the original question we can close the debate.  Yes the speed of light can be taken into account, but this effect is negligible for explaining dark matter in clusters.

Still, if it takes clearly more time parsing and changing wide areas of gravitational curved space - interactions? How the changed center mass density could "know" how much the curved space it must be signalling to change? Maybe it needs many feedbacks...

Esa: Nothing is fundamentally different in galaxy clusters than in the solar system.  You could as well wonder how the Earth "knows" where the Sun is while it takes 8 min for its attraction to reach the Earth.   The theory explaining it the best is GR which does take into account all the propagation delays.  Yet Newtonian theory is for most applications sufficiently precise to describe planet orbits to very good approximation because the speed of planets is so much lower than the speed of light.

In galaxy clusters the speed of galaxies, of order 1000 km/s,  is still much lower than the speed of light.  Despite the huge sizes (Mpc) the time-scale for gravity disturbances to cross a cluster is "only" a few millions years, while the time for  galaxy to cross the cluster is easily hundreds times larger.   So to excellent approximation the delay effect can be neglected.  

It is only in situations like close binary black-holes that full GR is needed.  The recent detection of gravitational waves from merging black-holes is a fantastic achievement confirming GR in the strong regime.

Daniel, your error is that the curved spacetime doesn't need any signalling between objects if they don't change their positions. Only the changes need signals between the spacetime near moving objects and the spacetime farther.

If the strongest area changes much in short time, the wide areas of  curved spacetime round original clusters continues moving. I think (a ruff estimation) that the correction in clusters as diameter of 1...10 million lightyears could take 1 billion years.

Of course there is many open questions with dark energy and dark mass, but some new models must be studied.

Esa: My error?  So you mean GR is wrong? 

In the GR frame space-time is curved according to mass-energy.  Any motion induces propagation of information in space-time.  The propagation speed is the speed of light in the curved space.  In galaxy clusters curvature is weak so in good approximation the propagation time is at most a few millions years, not billions. If you think otherwise ("...could take 1 billion years") you should explain why.

No, I meant my view is that you read GR wrong. The gravity doesn't propagate, only the gravitational changes do.

So if the problem is to define what is gravity, the best answer is the GR equations.  They contain all the subtelties that words cannot capture.   Newton was just saying the same for his theory, he didn't want to justify how gravity propagates, just that his equations describe how nature works.

http://thedaily.case.edu/rotating-galaxies-distribution-normal-matter-precisely-determines-gravitational-acceleration/

Now it seems to be possible that the whole dark mass is a counterpartner of conventional mass. My hypothesis of the series of delays when changing the gravity field can be one of the serious ideas.

I would be delighted if you would make your last assertion qualitatively more substanciated, say, at the level  of the quoted paper. .

My tentative little update on the project extending the theme of this thread.

https://www.researchgate.net/project/Studying-gravitational-serial-delay-mechanism-as-a-candidate-for-dark-mass-effect-in-spiral-galaxies-and-at-cluster-collisions

Debunking Dark Matter as an Unnecessary Parameter in Paradigm Gravitation

http://dx.doi.org/10.13140/RG.2.2.32243.50728