The fact that SOME galaxies are inconsistent with the theory of Dark Matter actually strengthens that theory.

If the difference in rotation curves, the usual signature of dark matter at the galaxy level, from what GR predicts based on the mass of luminous objects was due to a modification in the way gravity works, then that should apply to ALL galaxies. Modified Newtowian Dynamics (MOND) (or the relativistic TeVeS models) should work the same for all galaxies, at least all of roughly same mass and same depth of the gravitational potential.

The fact that we can find similar sized and aged galaxies that behave like they have different amounts of dark matter is therefore NOT caused by the way gravity works. The next best explanation is that most galaxies contain dark matter, but some loose it through their evolution history, e.g. due to interaction with other galaxies.

To be clear, they're not inconsistent with the theory of dark matter, they're inconsistent with those galaxies specifically having dark matter. The author was wording that in a confusing way.

That's right they are inconsistent with the combination of 1.) dark matter is the correct theory and 2.) they have the usual amount of dark matter for a galaxy of that size.

Surprisingly this is does not make the theory of dark matter (#1) less likely, but actually makes it more likely. Because the alternative is #1b "gravity works differently than we think". But that would have to hold for all galaxies.

To be even more clear, "dark matter" isn't a theory. It is a name for something we need theories about.

I wish the article had made that apparent.

Dark matter is a hypothesis, and one that makes pretty strong predictions, several of which have come true, so it's not inappropriate to call it theory.

The phenomenon of galaxies demonstrating significanty more mass than their sum of normal matter is the observation that is explained by dark matter.

Sorry but that’s an intellectual dodge. A verbal fiddle. Saying it is a “name for something” doesn’t make the fact that it’s a hypothesis disappear. One is simply positing the need for more “Russian dolls” inside the Russian doll one has hypothesised to begin with.

The way I understood it, they are not inconsistent with anything, they just happen to have no DM in them.

I found the authors' points about reports from the past several months disingenuous, since he's advertising a book that was clearly written and edited well before those announcements. It's valid to talk about those points in the context of arguments from the book, but leading with those points implies those arguments are a result of those points.

For some reason edits are silently failing, but an addendum to

> Big bang was only the accepted paradigm from the 60s (post CMB observations). We have had DE since Einstein in 1917 and DM since Zwicky in the 30s.

Admittedly the DE from Einstein is for very different reasons than the DE today, but we again had the big bang and no DE from the 60s until the 90s (observations from https://en.wikipedia.org/wiki/Supernova_Cosmology_Project) so they don't go hand in hand.

I've rarely seen more spectacular agreements with a theory than those of a Lambda-CDM fit of Planck's 2015 data. That can't be wrong (but as I've never worked on it, this statement is just some guy's personal impression based on his physics instinct). What's your take on those results?

> > Today's space telescopes provide no direct view of anything

> I have no idea what that means. They literally observe the sky...

Seriously! At this point they're just spitballing.

I was maybe a bit too cavalier here. I think I understand what the author means - the data that they gather is understood in the context of the model that we think is best.

But, it isn't as if cosmologists are rigidly holding to the model. Here's a paper looking at extensions to lambda CDM https://arxiv.org/abs/1512.05356. As I mentioned, changing GR is being looked at as an alternative to DE http://www.resceu.s.u-tokyo.ac.jp/workshops/resceu08s/presen...

People aren't challenging some things though - I don't think anyone is seriously working on cosmologies that don't include a big bang, because without one I can't imagine how you explain the CMB.

Sorry but I’d have to disagree: There are plenty of people working on cosmologies that don’t include the Big Bang, or that do include it but only as one facet of a larger theoretical framework.

As for not being able to imagine how you explain the CMB without the Big Bang, well, there are plenty of good arguments being made here that put to paid that “limitation.” As well, think of the Michelson-Morley experiment. In that era, no one could imagine how light could propagate through space without the presence of a medium permeating that space.

I’ll venture one step further. Dark Matter is to current cosmology what the aether was to 19th century cosmology.