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>"The galactic center shines too brightly, like the glow of a metropolis at night where maps show only a town. [...] The new study, along with two others that c

• nonbel 7y ago
  I am serious. This is what I have seen: Galactic rotation curves exactly as predicted: explained by dark matter Galactic rotation curves not as predicted: explained by dark matter Area of sky brighter than predicted: explained by dark matter Area of sky dimmer than predicted: explained by dark matter.
  • yorwba 7y ago
    X exactly as predicted (by a theory that includes dark matter): explained by dark matter X not as predicted (by a theory that doesn't include dark matter): explained by dark matter Not exactly contradictory if you add the context of how the predictions are made.
    • nonbel 7y ago
      I never said it was contradictory. I think what they've done is set up a system to filter out all theories except those that are flexible enough to be consistent with all possible observations. Specifically, they measure some value for each galaxy: x +/- e. Where e is calculated for a 95% (or whatever) statistical interval. In each paper they study another galaxy and check whether the prediction is within x +/- e, if they find one that is not there are two branches: 1) If it is a flexible theory: they adjust the theory, arbitrarily fit some parameters, etc. 2) If it is a very exact theory that cannot be adjusted: they reject the theory. Obviously this practice is flawed because the 95% interval says if you look at 100 galaxies and the theory is correct you should expect 5 of them to be outside your interval.
      • mirimir 7y ago
        This bothers me too. Theories with too many adjustable parameters aren't really testable. And so, following Popper, I don't see how they can actually be scientific.
        • nonbel 7y ago
          Check out Imre Lakatos. "Falsifiability" is too strict since "every model is wrong". Lakatos calls that Popper0, which is not what Popper ever advocated. In a nutshell: The real thing going on is you are supposed to use Bayes' rule, where you normalize how well your explanation explains the observations ( p(H[0])p(H[0]|D) ) to the sum of all known explanations ( p(H[0:n])p(H[0:n]|D) ). Thus if you have a vague explanation that can fit anything, it won't be much better than a million other possibilities so who cares. We only care when someone comes up with an accurate prediction that would be otherwise surprising. There are many more interesting ideas too (eg, "degenerating research programmes"). Edit: I should also emphasize that my main point above is that there is a misuse of statistics going on though.
          • mirimir 7y ago
            Yeah, I know Lakatos. > We only care when someone comes up with an accurate prediction that would be otherwise surprising. Sure. But the problem is when predictions don't pan out, parameters just get tweaked. Or new perturbations are introduced. Theories just keep getting more and more complicated.
            • nonbel 7y ago
              Yes, that is called a "degenerating research programme". The theory lags the observations.
          • nonbel 7y ago
            Typo: ( p(H[0])p(D|H[0]) ) to the sum of all known explanations ( p(H[0:n])p(D|H[0:n]) ).
        • XorNot 7y ago
  • Avshalom 7y ago
    Not entirely sure what you'r referring to by area of the sky but as to rotation curves it's: -Galactic rotation curve not as predicted by relativity: explained by dark matter -Galactic rotation curve exactly as predicted by relativity: allowed by dark matter, not explained by theories that propose a different uniform law of gravity that also explains case A.
    • nonbel 7y ago
      This is not my point here, but the galaxy you refer to is consistent with MOND: https://tritonstation.wordpress.com/2018/04/04/the-dwarf-galaxy-ngc1052-df2/ https://tritonstation.wordpress.com/2018/04/04/the-dwarf-gal...