Ok_Meat_8322 t1_iwi6qzv wrote
Reply to comment by InTheEndEntropyWins in Most cosmologists say dark matter must exist. So far, it’s nowhere to be found. Examining the philosophy of science behind two rival theories can explain why. by ADefiniteDescription
>I'm soo confused why they keep talking about the standard model in relation to gravity.
The standard model of cosmology (as opposed to particle physics) is the lambda-CDM model, where "CDM" stands for "cold dark matter" (and "lambda" denotes a positive cosmological constants, aka "dark energy").
>I think the main issues is that MOND by itself simply doesn't explain everything we see. So last I herd was that the only feasible MOND theories left were "MOND + dark matter" theories. I wasn't even aware that there were any major theories that didn't include dark matter of some kind.
From my own understanding (i.e. as a hobbyist with a background in philosophy, not physics), the entire purpose of MOND is to avoid having to invoke dark matter- the rough idea being that gravity works differently on the scale of galaxies/galaxy clusters, and that correcting for this explains the discrepancy between the observed rotational velocities of galaxies and galaxy clusters vs. their apparent mass without having to invoke a new type of matter.
InTheEndEntropyWins t1_iwigw5v wrote
There are lots of different types of observations that dark matter explains.
Even if MOND perfectly explained the rotational speed in galaxies it couldn’t explain the other observations. So you still need dark matter.
> The most serious problem facing Milgrom's law is that it cannot eliminate the need for dark matter in all astrophysical systems: galaxy clusters show a residual mass discrepancy even when analyzed using MOND
The fact that some form of unseen mass must exist in these systems detracts from the adequacy of MOND as a solution to the missing mass problem, although the amount of extra mass required is a fifth that of a Newtonian analysis, and there is no requirement that the missing mass be non-baryonic.
Ok_Meat_8322 t1_iwik6sj wrote
>There are lots of different types of observations that dark matter explains.
Sure, and the entire purpose of MOND is to account for these observations without having to invoke dark matter. So being forced to accept "MOND + dark matter" would completely defeat the purpose of proposing MOND in the first place.
ConsciousLiterature t1_iwiifqg wrote
MOND so far has been unable to explain all the phenomena dark matter does. I think most scientists see it as a failed effort.
Ok_Meat_8322 t1_iwikmts wrote
That's certainly my impression as well. But it wasn't a self-evidently crazy idea or anything, and probably adds some value to the conversation even if it is a failed effort (nothing wrong with trial and error, after all).
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