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This article is not very good. It conflates disproving specific models that use dark matter with disproving dark matter itself.

horsawlarway 4y ago
I would place this comment in the same bucket :P You can't "prove" that something doesn't exist. And dark matter is simply a big fat "????" inserted into our math to make our equations match what we see. I think it's fair for them to state that dark matter doesn't exist, in the same way that I can fairly confidently state that "The christian god" does not exist. Doesn't explain how we got here, or what actually needs to change to make our equations match our observations, but it's a reasonable stance to encourage folks to stop spending time on an unlikely solution (even if it so far produces the best model we have).
- ziddoap 4y ago
  >an unlikely solution (even if it so far produces the best model we have). If it is consistently producing the best model, why is it an unlikely solution? What would be more likely than the model which produces the best match to what we observe?
  - horsawlarway 4y ago
    Well - I would say this article is trying to discuss why it would be unlikely - Namely, most of the experiments we can find to experimentally test for dark matter fail. Just because a model fits our current data doesn't make it correct (honestly - my strong stance is no model is correct, but some models are useful, and some more useful than others). Epicycles were a fantastic explanation for the timing and movements of planets appearing in the sky - They were the best model we had for hundreds of years, but the model was also utterly incorrect. It wasn't until an almost rock solid assumption (that earth was the center of everything) was assaulted by Copernicus that we developed much more robust models. I find it fairly interesting that epicycles were also an attempt to explain a observational data that was very hard to fit into current models. There's a fairly straight parallel to dark matter here. I find it very compelling that we have a foundational assumption in our current model that isn't true, and that's why we're offsetting everything with dark matter to make the math line back up with reality.
    - ziddoap 4y ago
      I understand what you're saying, despite not necessarily agreeing with everything you are saying. It's just really odd to say: "X produces the best model we have" But also say: "X is an unlikely solution". If it produces the best model we have, it's the most likely solution at this time. That doesn't guarantee it will ultimately be the correct solution, sure.
      - horsawlarway 4y ago
        Totally fair. But we're in that weird spot where we've been trying to find a concrete example of dark matter (testable hypothesis that would apply) and so far we're not coming up all that hot. So I guess "unlikely" is probably too strong even in my opinion. I just think it hints that we have a structural problem in the house, and continuing to add wall paper is probably not going to fix the issue, we need a shift in understanding somewhere else.
- yccs27 4y ago
  > You can't "prove" that something doesn't exist You could definitely prove that something doesn't exist in any meaningful quantity. Happens all the time: The experiments searching for new particles end up proving that if they do exist, they interact too weakly to be detectable. Similarly you could make observations which place an upper bound on the dark matter density, possibly low enough that it cannot explain the galaxy rotation curves etc. anymore.
- hannasanarion 4y ago
  Dark matter isn't a mathematical invention, it is directly observed: the visible matter of galaxies and the bulk of their gravitational mass can be in different places. Any attempt to "disprove" dark matter that doesn't address the hard observational fact that gravitational mass and visible mass are separable is invalid. https://www.wikiwand.com/en/Bullet_Cluster https://www.wikiwand.com/en/Bullet_Cluster
  - horsawlarway 4y ago
    I really don't think we're disagreeing. You're just saying, very clearly: Our observational data does not match our mathematical models for gravity, and our alternative models don't account for this case (bullet cluster) I'm not disagreeing with you, and I'm not proposing MOND or derivatives are a valid solution, I'm just saying that you're still just positing: "we saw thing X that doesn't work with our current model, or with our modified model, so there must be some mysterious "dark" matter that we have to add to bring our math back to matching what we observe." So far, though - no experiment to actually find or record it, or make valid guesses about how or why it's distributed from a theoretical view, rather than as "glue" to hold our model back together, has been found (at least that I'm aware of). So I guess I am disagreeing - It's not "directly observed" in any sense other than "something is wrong here and we can't explain why".
    - magicalist 4y ago
      > It's not "directly observed" in any sense other than "something is wrong here and we can't explain why". That's not disagreeing, that's literally an observation, in this case via photons coming from things we can see possibly interacting with things we can't. That's as direct an observation as you're going to get for most things in the universe.
      - horsawlarway 4y ago
        > That's as direct an observation as you're going to get for most things in the universe. It is decidedly not. It's a clear sign that points at "Our models don't work well here", but simply noting that we're seeing an unexpected result is FAR different than being able to declare "we have observed dark matter". Basically - if you're saying that the bullet cluster is good evidence against MOND, welp... we agree. If you're saying the bullet cluster is direct observation of dark matter... I don't agree at all. It's just proof that both models are broken for the cases where we see galactic collisions. The fact that you can wallpaper over this in models with dark matter is... the point of dark matter in the first place: A handy escape hatch for cases like this.
- croes 4y ago
  Does a number exist that's greater than 2 but smaller than 1?
  - horsawlarway 4y ago
    yes... :P https://imgur.com/a/gAU89Qc https://imgur.com/a/gAU89Qc that 3 is greater in value than the number 2, yet smaller in size than the number 1. But more seriously - you're conflating a mathematical model with the reality we're observing. Our number systems (all the varieties of math) are subject to foundational contradictions and paradoxes, and proofs within them can be incredible tools - but they are not objective truths. We assume that the universe we experience and model is the same as the universe far, FAR away - and that's a reasonable and logical assumption - but it's STILL an assumption.
    - croes 4y ago
      You didn't distinguish between model or reality you just wrote you can't "prove" that something does not exist. And even in reality you can disprove things, you just need to define the environment. You can't disprove non existence in reality things universally and at all times.
    - croes 4y ago
      Good reply btw

horsawlarway 4y ago

I would place this comment in the same bucket :P You can't "prove" that something doesn't exist. And dark matter is simply a big fat "????" inserted into our math to make our equations match what we see. I think it's fair for them to state that dark matter doesn't exist, in the same way that I can fairly confidently state that "The christian god" does not exist. Doesn't explain how we got here, or what actually needs to change to make our equations match our observations, but it's a reasonable stance to encourage folks to stop spending time on an unlikely solution (even if it so far produces the best model we have).

ziddoap 4y ago
>an unlikely solution (even if it so far produces the best model we have). If it is consistently producing the best model, why is it an unlikely solution? What would be more likely than the model which produces the best match to what we observe?
- horsawlarway 4y ago
  Well - I would say this article is trying to discuss why it would be unlikely - Namely, most of the experiments we can find to experimentally test for dark matter fail. Just because a model fits our current data doesn't make it correct (honestly - my strong stance is no model is correct, but some models are useful, and some more useful than others). Epicycles were a fantastic explanation for the timing and movements of planets appearing in the sky - They were the best model we had for hundreds of years, but the model was also utterly incorrect. It wasn't until an almost rock solid assumption (that earth was the center of everything) was assaulted by Copernicus that we developed much more robust models. I find it fairly interesting that epicycles were also an attempt to explain a observational data that was very hard to fit into current models. There's a fairly straight parallel to dark matter here. I find it very compelling that we have a foundational assumption in our current model that isn't true, and that's why we're offsetting everything with dark matter to make the math line back up with reality.
  - ziddoap 4y ago
    I understand what you're saying, despite not necessarily agreeing with everything you are saying. It's just really odd to say: "X produces the best model we have" But also say: "X is an unlikely solution". If it produces the best model we have, it's the most likely solution at this time. That doesn't guarantee it will ultimately be the correct solution, sure.
    - horsawlarway 4y ago
      Totally fair. But we're in that weird spot where we've been trying to find a concrete example of dark matter (testable hypothesis that would apply) and so far we're not coming up all that hot. So I guess "unlikely" is probably too strong even in my opinion. I just think it hints that we have a structural problem in the house, and continuing to add wall paper is probably not going to fix the issue, we need a shift in understanding somewhere else.
yccs27 4y ago
> You can't "prove" that something doesn't exist You could definitely prove that something doesn't exist in any meaningful quantity. Happens all the time: The experiments searching for new particles end up proving that if they do exist, they interact too weakly to be detectable. Similarly you could make observations which place an upper bound on the dark matter density, possibly low enough that it cannot explain the galaxy rotation curves etc. anymore.
hannasanarion 4y ago
Dark matter isn't a mathematical invention, it is directly observed: the visible matter of galaxies and the bulk of their gravitational mass can be in different places. Any attempt to "disprove" dark matter that doesn't address the hard observational fact that gravitational mass and visible mass are separable is invalid. https://www.wikiwand.com/en/Bullet_Cluster https://www.wikiwand.com/en/Bullet_Cluster
- horsawlarway 4y ago
  I really don't think we're disagreeing. You're just saying, very clearly: Our observational data does not match our mathematical models for gravity, and our alternative models don't account for this case (bullet cluster) I'm not disagreeing with you, and I'm not proposing MOND or derivatives are a valid solution, I'm just saying that you're still just positing: "we saw thing X that doesn't work with our current model, or with our modified model, so there must be some mysterious "dark" matter that we have to add to bring our math back to matching what we observe." So far, though - no experiment to actually find or record it, or make valid guesses about how or why it's distributed from a theoretical view, rather than as "glue" to hold our model back together, has been found (at least that I'm aware of). So I guess I am disagreeing - It's not "directly observed" in any sense other than "something is wrong here and we can't explain why".
  - magicalist 4y ago
    > It's not "directly observed" in any sense other than "something is wrong here and we can't explain why". That's not disagreeing, that's literally an observation, in this case via photons coming from things we can see possibly interacting with things we can't. That's as direct an observation as you're going to get for most things in the universe.
    - horsawlarway 4y ago
      > That's as direct an observation as you're going to get for most things in the universe. It is decidedly not. It's a clear sign that points at "Our models don't work well here", but simply noting that we're seeing an unexpected result is FAR different than being able to declare "we have observed dark matter". Basically - if you're saying that the bullet cluster is good evidence against MOND, welp... we agree. If you're saying the bullet cluster is direct observation of dark matter... I don't agree at all. It's just proof that both models are broken for the cases where we see galactic collisions. The fact that you can wallpaper over this in models with dark matter is... the point of dark matter in the first place: A handy escape hatch for cases like this.
croes 4y ago
Does a number exist that's greater than 2 but smaller than 1?
- horsawlarway 4y ago
  yes... :P https://imgur.com/a/gAU89Qc https://imgur.com/a/gAU89Qc that 3 is greater in value than the number 2, yet smaller in size than the number 1. But more seriously - you're conflating a mathematical model with the reality we're observing. Our number systems (all the varieties of math) are subject to foundational contradictions and paradoxes, and proofs within them can be incredible tools - but they are not objective truths. We assume that the universe we experience and model is the same as the universe far, FAR away - and that's a reasonable and logical assumption - but it's STILL an assumption.
  - croes 4y ago
    You didn't distinguish between model or reality you just wrote you can't "prove" that something does not exist. And even in reality you can disprove things, you just need to define the environment. You can't disprove non existence in reality things universally and at all times.
  - croes 4y ago
    Good reply btw