you say that MOND cannot be extended.
Where did I say that? I expect MOND can be generalized, but I'm don't know of one that has been verified by data as yet. That's not to say there isn't one. It's hard to know when then are few layman interpretations of the load of grand abstract cosmo theories around at mo.
Structure formation: Can you be more specific? Whats there to not understand?
Mass binds due to gravity, so no surprise that it binds under MOdified Gravity ( which is stronger that gravity ). In Newton grav, extra mass ( DM ) is needed to get galaxys to bind. In MOND, the extra acel binds the galaxys.
MOND cannot account for large scale structures without some amount of DM.
Wrong.
Reiterate: People fixate on dark matter and dark energy as the solution to any disagreement between model and observation. They do this to preserve Newton's gravity. But since mond is not bound by Newtons grav, there's no need for this narrow focus on hidden mass-energy when using mond.
Reiterate :At the core of any DM vs MOND debate is always the insistance from the DM group to apply MOND as a universal\general theory whereby MOND fails. MOND isn't a general theory, so such arguments against MOND are not valid. It's really that simple.
This point has not been properly addressed by MOND advocates.
I just have done. Twice.
As an aside let's move onto this curious line chronos takes. He's made statements to this effect before.
I have no prejudice against MOND, merely doubts. It is an effective theory - not fundamentally based on the known laws of phyics. I therefore consider it suspect.
History shows that effective theories are almost always correct. I find it impossible to understand why anyone could think they are suspect in their correctness. All that has to be done to create an effective theory is to express what is seen. e.g. 'If I let go of a ball, it falls.' No need to invoke any physics at all. The only assumption here is time symmetry. The data is already there. It was the same with MOND.
In constrast, almost all hypotheses based on physics models fail. When one is found to be correct, it is a big event in science.
And true to the trend, DM theories failed repeatedly. Current DM theory is the result of repeated corrections in light of data that didn't previously fit.
Exercise. Classify these theories as either effective or derived.
1. Kepler's laws of motion.
2. Bohr's 2nd rule for the old quantum theory atom.
3. Relativistic time dilation
4. The aether
5. Newtons 2nd law of motion
6. Rayleigh jeans radiation law ( UV catastrophe )
7. Old quantum mutli electron atoms theory.
8. Planck's theory of radiation
9. De broglie hypothesis
10. 1st law of thermodynamics
I get 5 derived, 4 effective, and 1 intuitive
The point is just to show theories that are effective are amongst the most solid in physics, while hypothesis that are perfectly consistent with the rest of known physics can be wrong.
So it's only logical to suspect derived hypothesis, while being much more sure of effective ones. How Chronos has got them vice versa in his head, is beyond me, and to ponder how is a source of amusement, the world may never know how he's done it!