4 ms·

Nah, dark matter is the real deal. It's got way more evidence for it, and even the alternatives like MOND (which is something closer to a layman would argue as

Nah, dark matter is the real deal. It's got way more evidence for it, and even the alternatives like MOND (which is something closer to a layman would argue as "maybe we understand the theory wrong") do need dark matter to explain some measurements. Dark energy, on the other hand...

thereddaikon 5y ago
Dark matter isn't really a theory, its the name of an observation. Not sure how it can be any more or less legit. The name doesn't try to explain what's happening. Its just describing the weirdness of the observations. One thing that annoys me is the common description of dark matter as a single coherent theory of extra matter that can't be detected. Even wikipedia makes this mistake at the very beginning. But there are a lot of theories that try to explain it. None of which actually work yet. Once a theory that stands up is formed then the name will change.
- Maursault 5y ago
  Dark matter is not a theory, to be sure. It is a hypothetical.
  - ben_w 5y ago
    Dark matter is a set of observations; we have a dozen or so hypotheses to explain those observations that we cannot yet rule out.
    - Maursault 5y ago
      No, dark matter is not a set of observations, but instead it's a hypothetical form of matter, invisible and weakly interacting except with gravity, employed to explain a set of observations.
      - 8note 5y ago
        I don't think the weak interaction is required? Theres both theories for dark matter that include the weak force and that don't iirc? The only thing we know for sure is that we can define a field of masses that corrects for the difference between the observed behaviour and predicted behaviour of the cosmos vis a vis general relativity.
        Maursault 5y ago
        "Weakly interacting " does not mean the Weak Nuclear Force specifically. Dark matter only interacts with ordinary matter through gravity and does not interact through (or is vanishingly weakly interacting through) electro-magnetism, strong nuclear or weak nuclear forces.
  - thereddaikon 5y ago
    No its not a hypothetical. The measurements are there. Something unexpected is happening and nobody knows for certain what. The problem is someone picked the misleading name "Dark Matter" and then pop science, and actual scientists talking to laymen did the massive disservice of wording the explanation in such a way as to make it sound like there is a real theory that proposes there is some matter that interacts with gravity yet is invisible and undetectable in literally every other way called dark matter. I only learned the distinction in college when another student pointed out that dark matter as described was unscientific because it was an unfalsifiable, not to mention generally useless anyways. That led to patient explanation that it wasn't a hypothesis or theory and it was just what they called the observations. Would have been nice if anyone had bothered to start with that. There are a lot of hypothesis about what it really is. Neutrinos, WIMPS, SIMPS (heh), MOND etc etc. Personally I lean towards the got gravity wrong bit although not any specific explanation. I'm not a physicist but history and logic would suggest that while relativity is a pretty good explanation its far from complete. And I see no reason why forces necessarily have to work the same on the small scale and grand.
    - Maursault 5y ago
      Dark matter first gained notoriety when hypothesized to explain observations of galaxy rotation curves. Since the late 1930's, there have been a number of observations unrelated to galaxy rotation curves that couldn't be explained with contemporary science, so... it's dark matter! A lot that can't be explained got shoved into the dark matter hypothesis. Once enough things that couldn't be explained were lumped into dark matter, it became a part of the science paradigm. Once you understand paradigms, you'll understand why it seems like all of science is convinced that dark matter exists. But this is not actually the case, it is merely that dark matter has not been disproven. The luminiferous ether, another famous hypothesis, was once also embedded in the paradigm of science, and it only took one experiment to prove it did not exist to dislodge it. Dark matter is going to stick around until disproven, that is the nature of paradigms. As it turns out, dark matter is absolutely unnecessary to explain galaxy rotation curves, which can be simply explained and demonstrated accurately with a toy model without needing anything remotely like dark matter nor even Modified Newtonian Dynamics, but just the ordinary Newtonian physics. I suspect as time goes on, more and more of the stuff unrelated to each other that dark matter is employed to explain will be explained without the need for dark matter. There are no direct observations of dark matter, none whatsoever. And by definition, there never will be. It can't be seen! What there is instead are observations that don't have immediate explanations, so dark matter is hypothesized to explain it. That makes dark matter a hypothesis.
- gizmo686 5y ago
  Dark matter is not merely an observation. It is a class of theories to explain that observation. Specifically, if your explanation for the underlying observation is of the form "there is some matter-like stuff with mass that is causing the observed effects through standard G.R. gravity. We haven't otherwised observed it because X", then you have a dark matter theory. Typically X involves week to non-existant interactions through other forces. If your explanation for the observation involves saying "General Relativity is wrong", or positing the modification or addition of some other force, it may account for the observation behind dark matter; it may even be correct; but it is not a dark matter theory. Assuming some dark matter theory is proven correct, we will probably stop calling it dark matter when it is discovered. Although we still call nuclearly bound protons and neutrons with electrically bound electrons an "atom", even though we have since disproven the hypothesis that such objects are atomic. If the answer ends up not being a dark matter theory, we will probably just call it "gravity".
GuB-42 5y ago
The problem with dark matter is that it is a bit too easy to predict where it is. That's why so many people are looking for galaxies without dark matter. We sometimes find them, but I am not sure if there is an instance where we have confirmed that it is not a fluke of observation. The reason why it is a problem is that if you can reliably predict where dark matter is, then you can turn these predictions into equations and get away with dark matter as a form of matter. That's the idea behind modified gravity.

thereddaikon 5y ago

Dark matter isn't really a theory, its the name of an observation. Not sure how it can be any more or less legit. The name doesn't try to explain what's happening. Its just describing the weirdness of the observations. One thing that annoys me is the common description of dark matter as a single coherent theory of extra matter that can't be detected. Even wikipedia makes this mistake at the very beginning. But there are a lot of theories that try to explain it. None of which actually work yet. Once a theory that stands up is formed then the name will change.

Maursault 5y ago
Dark matter is not a theory, to be sure. It is a hypothetical.
- ben_w 5y ago
  Dark matter is a set of observations; we have a dozen or so hypotheses to explain those observations that we cannot yet rule out.
  - Maursault 5y ago
    No, dark matter is not a set of observations, but instead it's a hypothetical form of matter, invisible and weakly interacting except with gravity, employed to explain a set of observations.
    - 8note 5y ago
      I don't think the weak interaction is required? Theres both theories for dark matter that include the weak force and that don't iirc? The only thing we know for sure is that we can define a field of masses that corrects for the difference between the observed behaviour and predicted behaviour of the cosmos vis a vis general relativity.
      - Maursault 5y ago
        "Weakly interacting " does not mean the Weak Nuclear Force specifically. Dark matter only interacts with ordinary matter through gravity and does not interact through (or is vanishingly weakly interacting through) electro-magnetism, strong nuclear or weak nuclear forces.
- thereddaikon 5y ago
  No its not a hypothetical. The measurements are there. Something unexpected is happening and nobody knows for certain what. The problem is someone picked the misleading name "Dark Matter" and then pop science, and actual scientists talking to laymen did the massive disservice of wording the explanation in such a way as to make it sound like there is a real theory that proposes there is some matter that interacts with gravity yet is invisible and undetectable in literally every other way called dark matter. I only learned the distinction in college when another student pointed out that dark matter as described was unscientific because it was an unfalsifiable, not to mention generally useless anyways. That led to patient explanation that it wasn't a hypothesis or theory and it was just what they called the observations. Would have been nice if anyone had bothered to start with that. There are a lot of hypothesis about what it really is. Neutrinos, WIMPS, SIMPS (heh), MOND etc etc. Personally I lean towards the got gravity wrong bit although not any specific explanation. I'm not a physicist but history and logic would suggest that while relativity is a pretty good explanation its far from complete. And I see no reason why forces necessarily have to work the same on the small scale and grand.
  - Maursault 5y ago
    Dark matter first gained notoriety when hypothesized to explain observations of galaxy rotation curves. Since the late 1930's, there have been a number of observations unrelated to galaxy rotation curves that couldn't be explained with contemporary science, so... it's dark matter! A lot that can't be explained got shoved into the dark matter hypothesis. Once enough things that couldn't be explained were lumped into dark matter, it became a part of the science paradigm. Once you understand paradigms, you'll understand why it seems like all of science is convinced that dark matter exists. But this is not actually the case, it is merely that dark matter has not been disproven. The luminiferous ether, another famous hypothesis, was once also embedded in the paradigm of science, and it only took one experiment to prove it did not exist to dislodge it. Dark matter is going to stick around until disproven, that is the nature of paradigms. As it turns out, dark matter is absolutely unnecessary to explain galaxy rotation curves, which can be simply explained and demonstrated accurately with a toy model without needing anything remotely like dark matter nor even Modified Newtonian Dynamics, but just the ordinary Newtonian physics. I suspect as time goes on, more and more of the stuff unrelated to each other that dark matter is employed to explain will be explained without the need for dark matter. There are no direct observations of dark matter, none whatsoever. And by definition, there never will be. It can't be seen! What there is instead are observations that don't have immediate explanations, so dark matter is hypothesized to explain it. That makes dark matter a hypothesis.
gizmo686 5y ago
Dark matter is not merely an observation. It is a class of theories to explain that observation. Specifically, if your explanation for the underlying observation is of the form "there is some matter-like stuff with mass that is causing the observed effects through standard G.R. gravity. We haven't otherwised observed it because X", then you have a dark matter theory. Typically X involves week to non-existant interactions through other forces. If your explanation for the observation involves saying "General Relativity is wrong", or positing the modification or addition of some other force, it may account for the observation behind dark matter; it may even be correct; but it is not a dark matter theory. Assuming some dark matter theory is proven correct, we will probably stop calling it dark matter when it is discovered. Although we still call nuclearly bound protons and neutrons with electrically bound electrons an "atom", even though we have since disproven the hypothesis that such objects are atomic. If the answer ends up not being a dark matter theory, we will probably just call it "gravity".

GuB-42 5y ago

The problem with dark matter is that it is a bit too easy to predict where it is. That's why so many people are looking for galaxies without dark matter. We sometimes find them, but I am not sure if there is an instance where we have confirmed that it is not a fluke of observation. The reason why it is a problem is that if you can reliably predict where dark matter is, then you can turn these predictions into equations and get away with dark matter as a form of matter. That's the idea behind modified gravity.