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> but isn’t there something depressing about this? Like, faced with an interesting anomaly out there in the world, we have to resort to tweaking the model of d
by biorach 2y ago
> but isn’t there something depressing about this? Like, faced with an interesting anomaly out there in the world, we have to resort to tweaking the model of dark matter that is already an invention to fit observational anomalies
This is unnecessarily negative. Physics progresses in fits and starts, with plenty of blind alleys and red herrings. Maybe we're in a phase akin to the aftermath of the Michelson–Morley experiment. Or maybe it really is that complicated out there.
- pantulis 2y ago> Maybe we're in a phase akin to the aftermath of the Michelson–Morley experiment. Loving this comparison, and I hope this is the case.
- horsawlarway 2y agoI don't really find it unnecessarily negative. I find dark matter seems to fit into the same pattern as epicycles. We can add additional complexity to the theory to make our models better match observational data, and that's useful but also strongly hints that something more basic about the model is fundamentally incorrect. That's depressing.
- mr_mitm 2y agoWhich additional complexity has been added to dark matter? I'm not aware of anything. A WIMP would still explain everything, no? I don't see the comparison to epicycles at all. Then again, almost no one with a formal education in cosmology or partical physics at the PhD level does. Curious how that works.
- horsawlarway 2y agoSee - now this... this I find needlessly negative. > Then again, almost no one with a formal education in cosmology or partical physics at the PhD level does. This is also just wrong. I think we're seeing a number of established voices starting to question the underpinnings of dark matter as a theory. As for >Which additional complexity has been added to dark matter? Let's start with the fucking article we're discussing, where we now need to have "self-interacting" dark matter, as a new spin on the theory to account for the forces needed to explain what we're observing...
- mr_mitm 2y agoWhich established voices do you mean? All I see is the usual suspects, i.e. McGaugh, Kroupa, etc. The article is also not adding complexity. We didn't get new evidence that required modification of DM. We got a phenomenon which has many potential explanations as the "fucking" article points out, one of which could be a subset of all DM theories. The final parsec problem isn't challenging DM at all, instead one particular flavor of DM could help explain the observation. If anything, it could constrain DM. Why wouldn't you explore this possibility?
- horsawlarway 2y ago> Any path—periodic or not, closed or open—can be represented with an infinite number of epicycles. This is because epicycles can be represented as a complex Fourier series; therefore, with a large number of epicycles, very complex paths can be represented in the complex plane. We didn't get any new evidence that required modification of epicycles! We got a phenomenon which constrains the epicycle theory by adding more circles! <-- you. > If anything, it could constrain DM. Why wouldn't you explore this possibility? You're the only one suggesting that we throw out DM as a model right now... at no point have I even hinted at not exploring it. You are bashing someone who is simply suggesting that this model might not be correct (how fucking dare I...). But the thing about models... no model is correct, but some models are useful. Again - I'm not contesting that DM is currently a useful model for explaining some of things we're seeing. I'm suggesting that it might also be worth considering alternatives (how fucking dare I...). Go back to trying to burn Galileo alive. It's the same energy.
- tsimionescu 2y agoDark matter models have different amounts and distributions of it for each galaxy we care to look at, so there is no predictive power, similar to how they had to add new epicycles to explain the motion of every new planet they observed.
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- Keysh 2y agoThat's not even remotely correct. Just today I heard a talk about people looking at stellar motions in ultra faint dwarf galaxies, because standard dark-model theories predict they should have centrally cusped dark-matter density profiles -- and fuzzy dark-matter models predict different profiles, which they could potentially discriminate between.
- tsimionescu 2y agoI exaggerated a lot when saying that it has no predictive power, you're right. However, it is very much true that different galaxies have different amounts and distributions of dark matter. There are many broad categories, and certain models about galaxy formation try to predict these, but not all galaxies fit these models. This has two effects: for one, for any galaxy with unexpected dynamics, you can fit a dark matter distribution to explain the dynamics (but! This is not unbounded, it still has to match certain other observations). The other effect is actually in favor of a dark matter approach: it means modifying parameters of our theories in a general way has little chance to reproduce the same properties, as each different galaxy is different.
- sebzim4500 2y agoDetecting objects by first detecting their gravitational influence has been successful in the past, see the discovery of Neptune for example.
- zmgsabst 2y agoMichelson-Morley worked; we call it LIGO. The period after the apparent failure to the present success has been incredibly fruitful.
- tsimionescu 2y agoThe two are quite unrelated. Michelson-Morley was looking for a difference in the speed of light reaching the Earth from the Sun depending on the direction of motion of the Earh. Gravitational waves are not related to that in any way.
- zmgsabst 2y agoThey’re not unrelated: they’re the same experiment, looking for an aether — because spacetime is an aether theory. When the original aether theory failed, they pointed out that you squish when moving in the aether, and so they detected aether waves rather than aether motion. With an upgraded version of the same device.
- drdeca 2y agoI don’t see any good reason to be attached to using the word “aether” to describe [actual things that have been found].
- zmgsabst 2y agoWell, because they’re aethers - pervasive “stuff” which is the substance of the traveling wave, eg those detected by LIGO. Wilczek for instance points out that modern theories are aether theories.
- drdeca 2y agoWhat makes it "stuff"? Stuff/substances, as I think of it, has/have a velocity, etc. . In this sense, spacetime isn't a "substance"/isn't "stuff". Stuff/substances is where you can talk about a chunk of it, and say where it is at some later time.
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- Anotheroneagain 2y agoOr, maybe we are not. The problem with cosmology is that it's based almost purely on theory and not data, to the point of speculation.