Hossenfelder's Deceitful Babbling Close Nighttime Matter, A Mond Killer

One of the things that convey e'er driven me upwards the wall most the postmodern would-be scientific media was their constant advertisement of people who were or are absolutely self-evident hacks, crackpots, together with scammers every bit if they were skillful scientists. Sabine Hossenfelder is ane of the greatest examples I know.

In her newest rant she screams

No, that galaxy without night affair has non ruled out modified gravity

and attacks the recent newspaper "A galaxy lacking night matter" (TRF, Nature, arXiv). That newspaper has just observed a (rather small) galaxy where objects look to displace exactly every bit full general relativity predicts: at that spot is no involve for MOND or night affair inwards that galaxy.




Now, if the dark-matter-like effects predicted for that small-scale galaxy were rigid plenty to last observable, the determination is totally clear: Dark affair explains this Einstein-friendly galaxy good just because each galaxy could convey either kept its night affair or gotten rid of it – the presence of night affair is independent of the presence of visible matter.

On the other hand, the choice models without night affair – MOND or modified gravity – convey a occupation because when gravity is said to last modified, you lot can't plow these modifications off, together with then the conduct of each galaxy is predicted to disagree alongside full general relativity. Of course, the occupation is "how much". But let's believe the authors of the newspaper that the dark-matter-like effects are rigid inwards that galaxy, every bit good – Hossenfelder doesn't focus on this possible objection, anyway.




The authors of the Nature newspaper hash out this occupation that their run poses for MOND, of course:

...In theories such every bit MOND [27] together with the late proposed emergent gravity epitome [28] a “dark matter” signature should e'er last detected, every bit it is an unavoidable effect of the presence of ordinary matter. In fact, it had been argued previously [29] that the apparent absence of galaxies such every bit NGC1052–DF2 [our novel galaxy without night affair effects] constituted a falsification of the touchstone cosmological model, together with evidence for modified gravity...

The declaration is clear. Imagine that native American scientists investigate (and disagree) whether bras on the European women are a genetic mutation of the women from a unlike continent; or something that may last added. Once a European adult woman showed the kickoff strip tease for the audience of native Americans, the native American scientists knew: bras are just pieces of clothes, non a genetic aberration.

How stupid make you lot convey to last non to larn this elementary point? Look at Backreaction:

...It is beyond me why together with then many astrophysicists believe that modified gravity is somehow magically unlike from particle night matter, or indeed all other theories nosotros convey ever heard of. It’s not.

For both modified gravity together with particle night affair you lot convey additional degrees of liberty (call them fields or telephone telephone them particles) which involve additional initial conditions...

Wow, together with then it's similar a bra combined alongside the woman's mightiness to alter her deoxyribonucleic acid – together with then that sometimes the bra mutation is at that spot together with sometimes, it isn't there.

Hossenfelder – because she has written several crappy papers most MOND – tries to defend the indefensible. MOND isn't inwards trouble, she writes, because similar night matter, "it also has novel degrees of freedom".

No, it doesn't. MOND or modified gravity is withal gravity, together with then it's some collection of Newton-style or Einstein-style fields or forcefulness laws that influence the motion of pre-existing masses. In other words, MOND is withal gravity – massive objects displace inwards a way that is calculable from the distribution together with speed of other masses (i.e. from the stress-energy tensor produced yesteryear visible matter)!

You may utilisation extra fields but every bit long every bit your theory may last classified every bit "modified gravity", those don't allow you lot to plow the effect on or off – just similar ordinary Newton's gravity which also cannot last turned on or off. They're just a deeper formalism that allows you lot to calculate the modified Newton-style force.

The claim yesteryear that spherical bastard (if I utilisation Zwicky's clever dark-matter-inspired technical terminology) that MOND comes alongside extra "fields which may convey diverse initial conditions" together with this claim supposedly allows the effect to last turned on or off is just consummate hogwash. Even modified gravity withal has to last a long-range forcefulness – the arrive at is interplanetary space or basically interplanetary space relatively to particle physics scales, comparable to the size of galaxies or longer. It agency that the dispersion relations for the waves are those of the massless (or almost exactly massless, relatively to the particle physics masses) particles.

In other words, whatsoever "lump" that you lot could add together to these fields every bit a business office of the initial weather instantly flies away yesteryear the speed of lite – or yesteryear some speed that is extremely about the speed of light. No "lump" could rest within the portion occupied yesteryear the galaxy for millions permit lone billions of years. The entirely possible "lumps" that convey the mightiness to rest inwards the galactic portion are "lumps" enabled yesteryear the presence of the galactic matter, presence of the stars. The profile of these "static lumps" is fully dictated yesteryear the surrounding visible matter.

So later millions together with particularly billions of years, the dependence of the weather inwards the galaxy on the initial weather of the "new MOND fields" is guaranteed to convey completely faded away – or flown away. If some "lumps" were capable of sitting within the galaxy for billions of years, every bit good every bit flight away if they want, they would convey to last called affair (matter is something that tin give notice sit, something that has a residual frame and/or a depression speed). If they were invisible inwards optical telescopes, these "lumps" would last non just matter, they would convey to last called night matter. That's genuinely what night affair means. Theories of night affair for sure don't tell that the night affair particle cannot last described every bit a "lump" (e.g. a soliton). Dark-matter-like effects may last explained yesteryear some effects involving a really lite axionic field but last certain that Edward Witten together with collaborators telephone telephone such a province of affairs a theory of night matter.

The whole betoken together with motivation of MOND or modified gravity is that you lot don't involve to brand the additional assumptions most the presence or distribution of night affair – novel materials – inwards each galaxy. MOND is "more predictive" – it genuinely predicts that the dark-matter-like effects are e'er at that spot together with cannot last turned away because they're laws of physics – modifications of Newton's gravitational formula (that may last extracted from Einstein-style novel fields or not, that plays no purpose for the verification of the predictions). MOND says that the distribution of the visible affair is everything you lot involve – you lot must just utilisation improve (deformed) forcefulness laws than the master Newton's or Einstein's laws. So MOND is or was genuinely to a greater extent than predictive i.e. easier to falsify – together with indeed, that agency that nosotros may forget most it when a galaxy without the new, dark-matter-like effects is observed.

In the comment section, Andrew Thomas – who may last a night affair cosmologist inwards Adelaide, Commonwealth of Australia – politely points out that Hossenfelder's claims brand no sense. She continues to repeat her demagogic meaningless fog inwards several comments inwards that section, too. It's genuinely frustrating. It's evidently impossible to hash out modern scientific query alongside the likes of Ms Hossenfelder. But it's impossible to aid them, either, they're just every bit good pompous fools for that.

You know, this is non just some terminological disagreement. This is a give-and-take most validity of item theories together with diverse papers – Milgrom's, Verlinde's (and peradventure a newspaper yesteryear Hossenfelder) etc. – that convey been called MOND. The papers convey genuinely said something, promoted some ideas, some novel universal laws which brand predictions. If together with when the predictions are falsified, you lot can't alter the rules of the game together with pretend that MOND meant something different. Only total idiots may last fooled inwards this way.

Now, every at to the lowest degree slightly decent cosmologist or theoretical physicist understands perfectly good that Hossenfelder's comments are just land garbage. But most of them won't betoken this fact out clearly because they don't desire to last seen every bit discriminating against women. Sorry, you lot are throwing your scientific integrity to the toilet, comrades.