4 ms·

> like MOND because philosophically it is quite nice, and also tend to draw in people with minority/anti-etablishment habitus MOND is a non-relativistic theory

> like MOND because philosophically it is quite nice, and also tend to draw in people with minority/anti-etablishment habitus MOND is a non-relativistic theory. It's not even able to explain the orbit of mercury, gravitational lensing or black holes. It's the equivalent of hot gluing jet engines to a roman quadriga, it won't fly.

ars 2y ago
> MOND is a non-relativistic theory. Well obviously, it's literally in the name. A relativistic version of the theory is: https://en.wikipedia.org/wiki/Tensor%E2%80%93vector%E2%80%93scalar_gravity https://en.wikipedia.org/wiki/Tensor%E2%80%93vector%E2%80%93...
GuB-42 2y ago
Not really a problem, relativistic effects are negligible at the very low accelerations MOND is about. Should MOND work with galaxies, a theory that say "if the force is less than a threshold, use MOND, otherwise, use general relativity" is not pretty, but good enough to match the observations, and that's the important part. There are more elegant ways of doing it (ex: TeVeS), but before looking at the best way to reconcile general relativity and MOND, something we know is possible, it is important to make sure that MOND works at the scales it is supposed to work with. Currently, it doesn't, but dark matter doesn't either. More research is needed, as they say.
- kuschku 2y ago
  Disclaimer: Personal Opinion: Personally, I don't think MOND will be the solution. But I don't think it's going to be dark matter either. 1. We don't have a a way to unify relativity and quantum mechanics yet 2. Dark matter and MOND effects show up at extremely low accelerations. I have a hunch it's going to need a theory of quantum gravity to properly solve this. A century ago, quantum mechanics was initially formalized to explain the uktraviolet catastrophe of blackbody emissions. The difference between the classical emissions curve and the quantum based emissions curbe is very similar to the correction factor applied by MOND. I don't think that's a coincidence.
orwin 2y ago
I never said it was correct, but people smarter than me work on this and I do not have the scientific baggage to say they're wrong. To me they are as right as people working on lambdaCDM or dark fluid, as long as none of those theory is able to predict anything.

ars 2y ago

> MOND is a non-relativistic theory. Well obviously, it's literally in the name. A relativistic version of the theory is: https://en.wikipedia.org/wiki/Tensor%E2%80%93vector%E2%80%93scalar_gravity https://en.wikipedia.org/wiki/Tensor%E2%80%93vector%E2%80%93...

GuB-42 2y ago

Not really a problem, relativistic effects are negligible at the very low accelerations MOND is about. Should MOND work with galaxies, a theory that say "if the force is less than a threshold, use MOND, otherwise, use general relativity" is not pretty, but good enough to match the observations, and that's the important part. There are more elegant ways of doing it (ex: TeVeS), but before looking at the best way to reconcile general relativity and MOND, something we know is possible, it is important to make sure that MOND works at the scales it is supposed to work with. Currently, it doesn't, but dark matter doesn't either. More research is needed, as they say.

kuschku 2y ago
Disclaimer: Personal Opinion: Personally, I don't think MOND will be the solution. But I don't think it's going to be dark matter either. 1. We don't have a a way to unify relativity and quantum mechanics yet 2. Dark matter and MOND effects show up at extremely low accelerations. I have a hunch it's going to need a theory of quantum gravity to properly solve this. A century ago, quantum mechanics was initially formalized to explain the uktraviolet catastrophe of blackbody emissions. The difference between the classical emissions curve and the quantum based emissions curbe is very similar to the correction factor applied by MOND. I don't think that's a coincidence.

orwin 2y ago

I never said it was correct, but people smarter than me work on this and I do not have the scientific baggage to say they're wrong. To me they are as right as people working on lambdaCDM or dark fluid, as long as none of those theory is able to predict anything.