[lewdwig]

The problem with emergent theories like this is that they _derive_ Newtonian gravity and General Relativity so it’s not clear there’s anything to test. If they are able to predict MOND without the need for an additional MOND field then they become falsifiable only insofar as MOND is.

[dawnofdusk]

Deriving existing theories of gravity is an important test of the theory, it's not a problem at all. It's only a problem if you can only do this with more free parameters than the existing theory and/or the generalized theory doesn't make any independent predictions. Seems like in the article the former may be true but not the latter.

[cryptonector]

If such a theory makes no new predictions but is simple / simpler than the alternative, then it is a better theory.

[JPLeRouzic]

Please, how is the article related to MOND's theories?

[lewdwig]

In general, they’re not. But if the only thing emergent theories predict is Newtonian dynamics and General Relativity then that’s a big problem for falsifiability. But if they modify Newtonian dynamics in some way, then do we have something to test.

[westurner]

From https://news.ycombinator.com/item?id=43738580 :

> FWIU this Superfluid Quantum Gravity [SQG, or SQR Superfluid Quantum Relativity] rejects dark matter and/or negative mass in favor of supervaucuous supervacuum, but I don't think it attempts to predict other phases and interactions like Dark fluid theory?

From https://news.ycombinator.com/item?id=43310933 re: second sound:

> - [ ] Models fluidic attractor systems

> - [ ] Models superfluids [BEC: Bose-Einstein Condensates]

> - [ ] Models n-body gravity in fluidic systems

> - [ ] Models retrocausality

From https://news.ycombinator.com/context?id=38061551 :

> A unified model must: differ from classical mechanics where observational results don't match classical predictions, describe superfluid 3Helium in a beaker, describe gravity in Bose-Einstein condensate superfluids , describe conductivity in superconductors and dielectrics, not introduce unoobserved "annihilation", explain how helicopters have lift, describe quantum locking, describe paths through fluids and gravity, predict n-body gravity experiments on earth in fluids with Bernoulli's and in space, [...]

> What else must a unified model of gravity and other forces predict with low error?

[cryptonector]

u/lewdwig's point was that if an emergent gravity theory made the sorts of predictions that MOND is meant to, then that would be a prediction that could be tested. The MOND thing is just an example of predictions that an emergent theory might make.

[andrewflnr]

They both have to do with very weak gravitational fields.