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> Personally, I wouldn't be surprised that when we get the real theory of quantum gravity, if we ever do, that a lot of these "oh, look at this solution for gen

> Personally, I wouldn't be surprised that when we get the real theory of quantum gravity, if we ever do, that a lot of these "oh, look at this solution for general relativity!" obscurities go away In particular, I've thought dark matter is in this category of "bad theory rounding error" since I learned about general relativity and quantum mechanics in high school.

random314 5y ago
Why did you think that? How does dark matter invalidate general relativity?
- manwe150 5y ago
  I think they mean the reverse: since dark matter gives a possible solution to some of the unexpected observations resulting from the current theories, so if the theories later change, they are hoping the dark matter/energy terms will vanish. I likely have about the same physics knowledge as them, so I don’t speak from authority. But dark energy is not just a small fudge factor, so current theories seem unlikely to change by that much. As mentioned in the article, we have some measurements now also consistent with the existence of dark energy being pervasive, not just the appearance of it in theories.
- sam0x17 5y ago
  Because I was taught at a young age to assume everyone is fallible and question assumptions, and it seemed an awful lot like a rounding error to me at the time. As people have mentioned, there is apparently now more substantial support for it, but back then it was posited based on equations only, and seemed a lot more like trying to explain away a theory not fully matching reality
  - rmah 5y ago
    Um, as I understand it, dark matter was not posited by equations but by how observations differed from the the equations. And essentially, this is still the state of things. To wit, the standard model doesn't match observation unless there is this "dark matter" out there. We have no idea what it is. It's just what we call a particular type of ignorance. Current work is either a) assume that the theory is correct and that "dark matter" actually exists so they try to figure out what it is or b) assume that current theory is wrong and so try to come up with a better theory. Or c) a combination. And essentially the same thing for "dark energy".
    - sam0x17 5y ago
      I recall that back in the day my thought was that "Or our model of gravity is just wrong and what we're observing is correct (as in, visible matter is causing this behavior), we just don't understand how gravity works at massive scales because there are variables we aren't taking into account" but honestly it's been so long I forget all the basic info on this.
  - random314 5y ago
    > Because I was taught at a young age to assume everyone is fallible and question assumptions It is generally a good idea to have some familiarity (or better still, expertise) with a topic and knowing what the actual assumptions are before questioning them. I was very surprised that you had that kind of expertise in high school. For eg, did you know about the electromagnetic field theory and Maxwell's introduction/invention of displacement current in high school? Or reimannian geometry?
wongarsu 5y ago
"We just don't understand gravity well enough" is one of the top approaches physicists try to solve the mystery about dark matter, but so far it doesn't seem overly likely. Especially galaxies without dark matter [1] are hard to explain without labeling the majority of dark matter as some kind of particle or field. 1: https://www.nasa.gov/feature/goddard/2021/mystery-of-the-galaxys-missing-dark-matter-deepens https://www.nasa.gov/feature/goddard/2021/mystery-of-the-gal...
doliveira 5y ago
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.

random314 5y ago

Why did you think that? How does dark matter invalidate general relativity?

manwe150 5y ago
I think they mean the reverse: since dark matter gives a possible solution to some of the unexpected observations resulting from the current theories, so if the theories later change, they are hoping the dark matter/energy terms will vanish. I likely have about the same physics knowledge as them, so I don’t speak from authority. But dark energy is not just a small fudge factor, so current theories seem unlikely to change by that much. As mentioned in the article, we have some measurements now also consistent with the existence of dark energy being pervasive, not just the appearance of it in theories.
sam0x17 5y ago
Because I was taught at a young age to assume everyone is fallible and question assumptions, and it seemed an awful lot like a rounding error to me at the time. As people have mentioned, there is apparently now more substantial support for it, but back then it was posited based on equations only, and seemed a lot more like trying to explain away a theory not fully matching reality
- rmah 5y ago
  Um, as I understand it, dark matter was not posited by equations but by how observations differed from the the equations. And essentially, this is still the state of things. To wit, the standard model doesn't match observation unless there is this "dark matter" out there. We have no idea what it is. It's just what we call a particular type of ignorance. Current work is either a) assume that the theory is correct and that "dark matter" actually exists so they try to figure out what it is or b) assume that current theory is wrong and so try to come up with a better theory. Or c) a combination. And essentially the same thing for "dark energy".
  - sam0x17 5y ago
    I recall that back in the day my thought was that "Or our model of gravity is just wrong and what we're observing is correct (as in, visible matter is causing this behavior), we just don't understand how gravity works at massive scales because there are variables we aren't taking into account" but honestly it's been so long I forget all the basic info on this.
- random314 5y ago
  > Because I was taught at a young age to assume everyone is fallible and question assumptions It is generally a good idea to have some familiarity (or better still, expertise) with a topic and knowing what the actual assumptions are before questioning them. I was very surprised that you had that kind of expertise in high school. For eg, did you know about the electromagnetic field theory and Maxwell's introduction/invention of displacement current in high school? Or reimannian geometry?

wongarsu 5y ago

"We just don't understand gravity well enough" is one of the top approaches physicists try to solve the mystery about dark matter, but so far it doesn't seem overly likely. Especially galaxies without dark matter [1] are hard to explain without labeling the majority of dark matter as some kind of particle or field. 1: https://www.nasa.gov/feature/goddard/2021/mystery-of-the-galaxys-missing-dark-matter-deepens https://www.nasa.gov/feature/goddard/2021/mystery-of-the-gal...

doliveira 5y ago

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.