“IF” there is “Dark Matter”, then, yes.
But if there is no dark matter, then gravity wouldn’t constitute an explanation since there is no matter present to exert it.
Okay, but there is no ‘known’ scientific experience or observation where gravity is exerted apart from the presence of real matter, therefore it must first be established that dark matter is indeed real matter before we can offer an explanation that the effects we are observing is indeed gravity.
To conclude that there is gravity without first establishing that there is real matter (which experience tells us must be present to exert gravity) is to make an assumption with no empirical evidence to support it. I can also assume God did it.
I get the impression that some forms of science is not about what is necessarily true, but about what is assumed to be true based on pass observations and experiences. If it quacks like a duck, then it is a duck. If it quacks like gravity, then it is gravity, even though the presence of real matter has not been empirically verified to cause it to quack.
I don't think that gravity constitutes an explanation if it has not been confirmed that there is real matter present to exert it. Hypothetical dark matter has never been observed to exert gravity, and it never will.
I fear you still don´t understand what I am talking about, hung up as you are on the existence or non-existence of dark matter as you are.
It does not
matter if dark matter exists or not. It does not have to be a
correct explanation. It is possible / likely that other explanations exist... even your beloved plasma cosmology presents an explanation.
But these options
have explanatory value, because there exists a mechanism, a causal relationship between the object and the effect.
Mass -> force.
Electromagnetic field -> force.
Now it is left to the observers, the experimentors, the testers to divise a way to find out the
correct explanation. To search for dark matter. To find an observation to exclude electromagnetic fields. OR VICE VERSA... it does not matter!
Yet...
God -> ?
There is no mechanism, no causal relationship. There isn´t even an idea of such a thing. It is deliberately left vague... "with God, all things are possible". If everything is possible, you cannot make any distinctions. No way to keep right from wrong.
"God did it." has the same explanatory value as "blue caused it".... none at all.
Hypothetical dark matter has never been observed to exert gravity, and it never will.
This is where you are wrong, and this is the mistake at the very basis of our misunderstandings here. Hypothetical dark matter does not need to be observed to exert gravity. It will, by the simply fact of being what it is.
You seem to assume that, because "dark matter" has not been observed, and it´s effects not measured, it could behave completely different. But that is wrong. If I have a hypothetical cube/die in my hand, and hypothetically throw it, I can with certainty say that it will land on one of its six sides... and not on the eighth. Simply because even hypothetical cubes - even if they don´t exist - have only six sides.
A quite good example for such an "hypothetical dark matter" would be the planet Neptune. It wasn´t (primarily) found by direct observation, but by the (gravitational) effect it had on the other planets (specifically Uranus). So here you have it: hypothetical matter that has been observed to exert gravity.