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> While dark matter is currently our best explanation, it is deeply flawed Calling it deeply flawed is focusing on just one aspect of it. The name just refers

> While dark matter is currently our best explanation, it is deeply flawed Calling it deeply flawed is focusing on just one aspect of it. The name just refers to the darkness in our knowledge about what it is. We don't know. It might be a form of matter, it might be a new factor in our equations or something completely different.

dnautics 5y ago
there's definitely some weird shit going on with "conventional dark matter theories". For example, aside from the fact that both are mysterious, there is no a priori reason for "the same phenomenon" to explain - matter chunkiness at the universe-size scale - rotational discrepancies at the galaxy-scale yet it seems to be taken as gospel that lambda-CDM explains both. Please correct me if I'm wrong about this.
- NZGumboot 5y ago
  You're right that there could be multiple things which separately explain the things that dark matter explains (not just the two you listed, but the others as well: gravitational lensing, galaxy cluster motion, etc). But the strength of the dark matter model is that it can explain all of these phenomena; which is why most physicists prefer dark matter over other theories. It's very easy to come up with a theory which explains a single phenomena, but very hard to come up with one that simultaneously explains multiple phenomena.
  - dnautics 5y ago
    To play devil's advocate, the strength of a model alone is not sufficient: I could say: Well, how can we be certain "gravitational waves" detected by LIGO aren't random dark matter density ripples and not GW from events we haven't correlated (n=1 on independent correlations). In other words, the dark matter model is too strong, because there is a arbitrarily parametrizable density field... Hell, there are people postulating Sagittarius A* is a very dense ball of DM and not a black hole. At that rate you can explain anything with dark matter. I have no logical or philosophical basis for this but in general when this sort of thing starts happening I start doubting the validity of a concept, not gaining confidence in it.
- trhway 5y ago
  >- rotational discrepancies at the galaxy-scale that discrepancy only exists if one thinks that : 1. the 6th grade formula for total gravitational force and resulting orbital velocity for 2 spherical balls (one having mass of the galaxy, the other - our target star) at large distances accurately describes the gravitation and orbital velocity of a star inside the disk. Well, it is not. One has to integrate/sum over all the stars and matter in the galaxy (though each star's and remote gas region's contribution into the total force toward our target star can be calculated using that 6th grade formula, so no MOND or the likes is needed) to calculate the gravitational force of the whole galaxy acting upon our target star. The disk shape results in the significant "discrepancy" from the "2 spherical balls" model predictions. The thinner the disk the larger the "discrepancy" - more DM as its proponents claim. 2. the galaxies are fixed rotating bodies, and the stars orbit the Bulge on fixed orbits. They aren't. The galaxies evolve with the disk becoming wider and thinner with time (more and more DM/"discrepancy"). Just like a spiral wheel firework. That is exactly what happens when stars' velocity is higher than would be needed to maintain fixed orbit (i.e. what the 6th grade formula would suggest). Btw, that also means that 2 billion years ago when the life appeared on our planet the Solar system was much closer to the Bulge, not in the deserted suburbia that we're right now.

dnautics 5y ago

there's definitely some weird shit going on with "conventional dark matter theories". For example, aside from the fact that both are mysterious, there is no a priori reason for "the same phenomenon" to explain - matter chunkiness at the universe-size scale - rotational discrepancies at the galaxy-scale yet it seems to be taken as gospel that lambda-CDM explains both. Please correct me if I'm wrong about this.

NZGumboot 5y ago
You're right that there could be multiple things which separately explain the things that dark matter explains (not just the two you listed, but the others as well: gravitational lensing, galaxy cluster motion, etc). But the strength of the dark matter model is that it can explain all of these phenomena; which is why most physicists prefer dark matter over other theories. It's very easy to come up with a theory which explains a single phenomena, but very hard to come up with one that simultaneously explains multiple phenomena.
- dnautics 5y ago
  To play devil's advocate, the strength of a model alone is not sufficient: I could say: Well, how can we be certain "gravitational waves" detected by LIGO aren't random dark matter density ripples and not GW from events we haven't correlated (n=1 on independent correlations). In other words, the dark matter model is too strong, because there is a arbitrarily parametrizable density field... Hell, there are people postulating Sagittarius A* is a very dense ball of DM and not a black hole. At that rate you can explain anything with dark matter. I have no logical or philosophical basis for this but in general when this sort of thing starts happening I start doubting the validity of a concept, not gaining confidence in it.
trhway 5y ago
>- rotational discrepancies at the galaxy-scale that discrepancy only exists if one thinks that : 1. the 6th grade formula for total gravitational force and resulting orbital velocity for 2 spherical balls (one having mass of the galaxy, the other - our target star) at large distances accurately describes the gravitation and orbital velocity of a star inside the disk. Well, it is not. One has to integrate/sum over all the stars and matter in the galaxy (though each star's and remote gas region's contribution into the total force toward our target star can be calculated using that 6th grade formula, so no MOND or the likes is needed) to calculate the gravitational force of the whole galaxy acting upon our target star. The disk shape results in the significant "discrepancy" from the "2 spherical balls" model predictions. The thinner the disk the larger the "discrepancy" - more DM as its proponents claim. 2. the galaxies are fixed rotating bodies, and the stars orbit the Bulge on fixed orbits. They aren't. The galaxies evolve with the disk becoming wider and thinner with time (more and more DM/"discrepancy"). Just like a spiral wheel firework. That is exactly what happens when stars' velocity is higher than would be needed to maintain fixed orbit (i.e. what the 6th grade formula would suggest). Btw, that also means that 2 billion years ago when the life appeared on our planet the Solar system was much closer to the Bulge, not in the deserted suburbia that we're right now.