Comment by acqq | Hacker News Reader

Comment by acqq | Hacker News Reader

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> Dark Matter

> Superfluid Dark Matter

As far as I see, from three theories you listed, two are the dark matter theories. The only "alternative" from your list is MOND and as far as I know it has more problems than it can solve:

https://medium.com/starts-with-a-bang/theres-a-debate-raging...

"The tests on the largest scales give us the best tests for dark matter. And these are the ones that dark matter not only universally passes, but that MOND has failed spectacularly for, on every account, for the past 35 years. Among cosmologists*, there is no debate, because there is no alternative to dark matter that reproduces the observed successes."

https://arxiv.org/abs/1112.1320

"The biggest challenge facing MOND today is the shape of the matter power spectrum. The shape depicted in Fig. 1 is related to the acoustic oscillations observed in the CMB. If the Universe is dominated by dark matter, these matter oscillations, dubbed Baryon Acoustic Oscillations (BAO), are highly suppressed as the baryons fall into the potential wells created by dark matter, leaving only percent level traces of the primordial oscillations. In a no-dark matter model, on the other hand, the oscillations should be just as apparent in matter as they are in the radiation. Indeed, Fig. 1 illustrates that – even if a generalization such as TeVeS fixes the amplitude problem – the shape of the predicted spectrum is in violent disagreement with the observed shape."

I'm just a layman, so I may have misunderstood Sabine's explanation, but to my knowledge Dark Matter, as a theory, is fundamentally different from Superfluid Dark Matter. In the latter, there's a new kind of force explaining why MOND, in certain cases, works. She notes at the end of the third video I listed above that Superfluid Dark Matter should be considered a combination of both Dark Matter and MOND. I would recommend taking a look at her video, it's short (about 6 mins) and I found it quite clear. Anyway, this is far from a solved problem, and no theory is sufficiently developed to be the last word on the subject.

> to my knowledge Dark Matter, as a theory, is fundamentally different from Superfluid Dark Matter.

To to be able to fit with the CMB measurements, at that scale this theory behaves exactly like a normal dark matter, so there is still 5 times more dark matter than a baryonic matter.

So it's just "more complicated" at the galaxy level than a normal dark matter, to fit with these measurements "better" too: it involves an "additional force" there. That also means, considering everything together, it's nothing that should make happy those that consider the normal dark matter "unintuitive."

Dark matter is a supersolid that fills 'empty' space, strongly interacts with ordinary matter and is displaced by ordinary matter. What is referred to geometrically as curved spacetime physically exists in nature as the state of displacement of the supersolid dark matter. The state of displacement of the supersolid dark matter is gravity.

The supersolid dark matter displaced by a galaxy pushes back, causing the stars in the outer arms of the galaxy to orbit the galactic center at the rate in which they do.

Displaced supersolid dark matter is curved spacetime.

In the Bullet Cluster collision the dark matter has not separated from the ordinary matter. The collision is analogous to two boats that collide, the boats slow down and their bow waves continue to propagate. The water has not separated from the boats, the bow waves have. In the Bullet Cluster collision the galaxy's associated dark matter displacement waves have separated from the colliding galaxies, causing the light to lense as it passes through the waves.

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