dark matter - the new epicycle?
I think many people would be happy (myself included) if there is theory that wouldn't require dark matter and dark energy. But at the moment there is none and to me (and many astrophysicsts) the universe with dark matter is the best description we've found so far of what we observe.
Kepler and Newton's models produce better predictions over a long period than Ptolemaic models, which is great. But it's a bit of delusion to think that necessarily means they are analogous to the cosmological mechanisms that produce orbital mechanics.
this was my point with the initial epicycle comparison
I do think dark matter is tantalizing because it hints strongly that our model needs a fundamental change in understanding at some other level. It just feels like too much wall paper to be adding to the model in an attempt to cover the holes.
Doesn't mean I find any of the current alternatives more viable then our current models.
This isn't to say that is a bad thing, it is a great thing.
But I think what you mean that you treat some theories as axioms (temporarily, I hope). It's a great aid in thinking but a great source of confusion for newbies as well.
It's incredibly hard to know until we've either observed DM particles or made good alternative hypothesises which also fit the data.
It's popular to look for types of Dark Matter that interact very weakly with forces other than gravity (WIMPs). That's a lot like the joke of the man searching for his keys under a street light even though he dropped them away from the light, because the light is better there. It's perfectly possible that Dark Matter ONLY interacts gravitationally, and so will never be detected by any of the current approaches. Detecting the gravitational force of an elementary particle is ridiculously difficult, well beyond the sensitivity of any current detectors. Even if we could, there would be a huge noise floor from all the normal matter around!
The reason we teach the Michaelson-Morley experiment in basic Physics classes is because it's a bedrock example of Science functioning correctly. The reason people believed in the ether theory is because in the wake of Maxwell's revolutionary work, there needed to be an explanation of how light propagated that could be reconciled with Newton's mechanics which had been laid out 200 years earlier. In hindsight, we credit Einstein with finding the way out, but in the late 1800's it was in no way obvious that it was going to work out that way.
Going back to my Einstein example, there were other Physicists who contributed to Relativity (Lorentz, Minkowski, Poincaré, Fitzgerald) but we give Einstein the most credit because he had the right idea, that it's not enough to treat the speed of light as a constant in your math, you actually have to believe the Universe works that way. One of the stories that gets told is the reason Einstein never got a Nobel prize for Relativity is because the Nobel committee just wasn't ready to give it up and credit Einstein with discovering a new, fundamental truth about the Universe.
Another story that gets told is that when Einstein was an undergrad at the ETH in Zurich, Minkowski was one of his professors and he dismissed Einstein for being a "Lazy Dog" because the math never came easy to him. But he looked at how Physics was taught at the time and knew something had to change. And he was right about that.
I'll just leave this here, Feynman explained it better than I ever will.
I mean, i imagine its difficult because we can't really conduct direct experiments, but i don't see any reason that its non-falsifiable.
The aether makes specific predictions. Like the fact that we're all traveling through it because it is a background medium. These were clearly refuted.
Fields are not aethers. Fields do not have a reference frame.
I don't think that's case, at least to me it seems that the basic objection is some vague discomfort with the idea, not an issue with the falsifiability. And dark matter is clearly falsifiable, it has already survived many observations.
The CMB power spectrum would look entirely different if there was no dark matter.
Gravitational lensing in certain areas in the sky wouldn't look as strong as it does without dark matter either.
Dark matter, on the other hand, is not a conceptual necessity but an empirical one. Whereas aether was something people clung to because they couldn't imagine a world without it, dark matter is something scientists have been forced into even though the world would be more conceptually elegant without it.
I don't know which aspects you think dark matter shares with miasma. Dark matter fits all the data; miasma doesn't.
the fact that dark matter is widely accepted without proof, and that the current model continues to encounter new anomalies, puts it about on the same level as strings for me—very cool and i hope it's real, but likely to be explained away when we better understand quantum physics and higher dimensions
And dark matter is not accepted without proof. It fits the data extremely well. That is the proof. It explains many unrelated phenomena and isn't ruled out by anything; just like gravity. The fact that we can explain why things fall down, why the moon orbits around the earth, why the earth orbits around the sun, why stars form, why planets form and a whole bunch of other phenomena with one force is the proof; we haven't seen a gravity particle, but that doesn't matter, because that's not how proof works in science.
It's not about thinking it's cool and hoping it's real either. It's simply the only explanation we have for a whole bunch of stuff, and it's a damn good explanation that's extremely simple.
That's not to say it's necessarily correct. It's just the only explanation we have, and we have no reason to believe it not to be correct.
> we can explain why things fall down
that's pretty new too! and it's not semantically correct, but was considered so for quite a while. this is a pretty good analogy for why i'm skeptical of dark matter
Suppose you had six frames of a ball moving in a parabolic trajectory. A sixth order polynomial would fit the data incredibly well, but I don't think you would accept it as a good model for the motion of the ball.
You can't say "it isn't ruled out by anything":
EFE rules out LCDM. Galaxies are redshift >~ 7 rules out LCDM (we now have galaxies at redshift > 13).
DM's failures are more numerous, and it has to be extended with new assumptions to account for other observations. MOND's predictions fair better as favourable evidence actually [1].
[1] From Galactic Bars to the Hubble Tension: Weighing Up the Astrophysical Evidence for Milgromian Gravity, https://www.mdpi.com/2073-8994/14/7/1331/htm
More to the point, since epicycles are just a Fourier decomposition, they're actually perfectly correct. The problem, though, is that they are a nightmare to compute with unless you have a modern computer.
Once Kepler decided to use an ellipse to model solar orbits; however, things were vastly easier to compute. At that point, the epicycle model got swiftly pushed aside.
The reason why LCDM gets called epicycles is that there is charitably one free parameter per galaxy (dm: bm ratio -- but actually more, because it's an arbitrary distribution)... So the fact that it has high explanatory power is unsurprising. And what's should be dismaying is the number of things it can't explain, given just how many free parameters you're allowed to have in a DM model.
Where we run into trouble is by assigning too much credence (or too little skepticism) for that which has not been proven yet. This can be counter-productive as it may stifle research into other areas (in this case gravity). When we take the "best current theory" and deride skeptics of it to the point that it discourages other areas of investigation, that's a bug, not a feature.
Our current understanding of gravity is woefully inadequate, as shown by our inability to reproducibly measure the gravitational constant as well as we should be able to with current technology. The flyby anomaly is another example where DM does not help. I hope that the current popularity of DM does not stifle research into gravity.