But armchair physicists love to shriek 'bullet cluster' every time because they aren't aware of the extent of their ignorance. Considering your HN bio I'd comfortably classify you as "knows just enough to be dangerous". Fair, given your generalization knowing nothing about me?
More reading for your benefit, from a working astrophysics professor specializing in ultra-diffuse galaxies:
Lots of ground between settled science and “no good reason is ever given.”
There are strong arguments for dark matter (broadly, not just Lambda CDM). They are inconclusive. The bullet cluster is less strong evidence for dark matter than good evidence against common armchair refutations. (I agree with your author that it doesn’t rule out MOND as is commonly claimed.)
The arguments inevitably and only boil down to "look, our model converged". The point is, dark matter is not a theory, just a supposition that can always be "proven" with conveniently arbitrarily flexible models (no one can see it so it might be anywhere!).
There is no positive theory that has been brought out to explain dark matter, only mere deductive hypothesis about where it would be. Deduction needs a culprit so people keep reaching for different kinds of particles. Jury's out on whether they exist but keeps the experimentalists employed, so at least it's worth that much.
There have been actually many positive theories trying to explain what particles dark matter could be, they've all been proven wrong.
To me dark matter came about from this,
"As we understand gravity we can postulate how galaxies rotate given an estimate on its mass, galaxies do not rotate like this"
In this statement there are three elements;
1) Our understanding of gravity
2) Our estimates of the mass of galaxies
3) Our ability to determine how galaxies rotate.
At one point in time this last 100 years, we had "solved" gravity with regards to our solar system, and we were finding so many new particles that #2 seemed like a great explanation. However, we are now left with no room in our understanding of particles, I think its time to look at the other elements.
Put it this way, if we had never observed the galaxy, but developed the standard model in isolation. Then we looked at the stars and tried to define gravity, I'm not sure we'd be so quick to introduce a new type of matter to define gravity.
> There have been actually many positive theories trying to explain what particles dark matter could be, they've all been proven wrong.
Not at all. Ordinary neutrinos and MACHOs (black holes, rogue gas giants, extremely faint dwarf stars) are mostly ruled out. Supersymmetry is not looking promising but certainly not proven wrong. Sterile neutrinos and axions are very much live candidates.
> However, we are now left with no room in our understanding of particles
There's plenty of room. Quantum gravity is obviously the elephant in the room, but even aside from that, and off the top of my head: the standard model doesn't account for neutrino masses ,matter/antimatter asymmetry, or why the lepton masses are related, and it gets the magnetic moment of the muon wrong. The existence of physics beyond the standard model is certain. We just don't know what it is yet.
>Quantum gravity is obviously the elephant in the room,
Isn't that just our understanding of gravity not being complete.
> the standard model doesn't account for neutrino masses ,matter/antimatter asymmetry, or why the lepton masses are related, and it gets the magnetic moment of the muon wrong. The existence of physics beyond the standard model is certain.
That seems to be a big leap, is not the existence of flaws in our understanding of gravity also certain?
> Isn't that just our understanding of gravity not being complete.
No. It's that, but it's not just that: if a QFT in 4-d spacetime has a coupling constant with a negative mass dimension, it has infinitely many free parameters, which means you can only use it below a given energy scale. We live in a 4-d spacetime, and the mass dimension of Newton's constant is -2, so either the true theory is not a QFT, or it's an infinitely complicated QFT we can never actually find.
> That seems to be a big leap, is not the existence of flaws in our understanding of gravity also certain?
Yes, both GR and the standard model are known to be incomplete.
> It's that, but it's not just that: if a QFT in 4-d spacetime has a coupling constant with a negative mass dimension, it has infinitely many free parameters, which means you can only use it below a given energy scale.
Huh.
Do you know of any videos that go into more depth? (My level is the "PBS Space Time" and Sabine Hossenfelder videos as I don't do this professionally).
Fair enough. I think it’s qualitatively different from SUSY, where I tend towards your conclusion of jobs programme masquerading as theory. (I’m much less convinced dark matter is a novel particle.)
But armchair physicists love to shriek 'bullet cluster' every time because they aren't aware of the extent of their ignorance. Considering your HN bio I'd comfortably classify you as "knows just enough to be dangerous". Fair, given your generalization knowing nothing about me?
More reading for your benefit, from a working astrophysics professor specializing in ultra-diffuse galaxies:
https://tritonstation.com/2016/12/23/crater-2-the-bullet-clu...
https://tritonstation.com/2017/03/06/lcdm-has-met-the-enemy-...
https://tritonstation.com/2016/07/30/missing-baryons/