First test of rival to Einstein’s gravity kills off dark matter

As others have mentioned, Lubos Motl is no longer in academia. He seemed to have spent more time criticizing others (and not just their works) than on actual physics. His appointment at Harvard was not reviewed.

I'm frankly surprised New Scientist bothered to quote him.

It does seem unfair to fault one theory for making up terms but to ok the invention of dark matter and its placement wherever needed. Perhaps dark matter will be like vulcan: a big chunk of mass invented and placed so as to confirm an outdated model. The new model described a new force, mooting the need for the mass.

I like Ethan Siegel's explanation of the Verlinde's paper much more than the article with the "kills off" in the title:

http://www.forbes.com/sites/startswithabang/2016/11/12/ask-e...

"The hope is, with the right assumptions, a full theory of gravity, That's the big hope, and what Verlinde is working towards. (Others are also working towards it independently.) This paper is an update on how it's going. So, how's it going?

"There are some successes given very specific assumptions, but there are a lot of problems. The largest problem, quite simply, is that one needs to make a multitude of seemingly arbitrary "interpretation" decisions to wind up with something other than nonsense. For example: the full motivation for this approach is based in anti-de Sitter space (or space with a negative cosmological constant), but our Universe is observed to have a positive cosmological constant (i.e., de Sitter space), and the mathematics of the two spaces have very different properties. For another, you need the entropy to obey a strict area-based law to get the Einstein equations out, but you don't get a cosmological horizon out if you do. (And our Universe has one.) And finally, if you make all the assumptions you need to in order to get the gravitational acceleration for galaxies out, you destroy all of General Relativity's successes on larger-than-galaxy scales. (Verlinde, on pp. 39-40, makes the argument that it could succeed, but the observations of colliding galaxy clusters completely undermine his line of thought.)"

There's even more discussion in the Ethan's article, which is much more balanced.

And another take on Verlinde's paper by Sabine Hossenfelder:

http://backreaction.blogspot.co.at/2016/12/can-dark-energy-a...

"General Relativity is a rigorously tested theory with many achievements. To do any better than general relativity is hard, and thus for any new theory of gravity the most important thing is to have a controlled limit in which General Relativity is reproduced to good precision. How this might work in Verlinde’s approach isn’t clear to me because he doesn’t even attempt to deal with the general case. He starts right away with cosmology."

"I'd say he takes inspiration from models that are best understood in AdS." but "he starts with de-Sitter space which means he assumes dark energy. It doesn't make sense to say that this is a source of dark energy, it's the same thing, period."

He's not exactly a crank, but he's not a working physicist either, afaik.

You can also have the idea that there are one-way interactions between the normal-matter universe and the dark-matter universe.

It isn't too difficult to formulate a mathematical system where two subsets are completely identical when considered in isolation, but when interacting, one subset operates as if the other doesn't exist, while the other is easily perturbed by any values in the mirror subset. I'm not sure if you can do it without at least one dimensional basis unit that squares to zero, though.

Imagine, if you will, that there are dark-matter people. We have no evidence whatsoever that they exist, any they are constantly annoyed by all the real-matter people that wander between their dark-couches and dark-televisions, and the real-matter bicyclists that pedal through their dark-bedrooms at the worst possible times.