• NocturnalMorning@lemmy.world
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    1 day ago

    We have never detected dark matter. Dunno what you’re talking about. It’s existence was posited because of differences in observed velocities at the edge of galaxies vs what we expected to see.

    • i_love_FFT@jlai.lu
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      24 hours ago

      What is your definition of “detected”? If only direct interaction using the EM field is required, then we have never detected anything…

      There are lots of gravitational lensing images of dark matter, we can even see some structures in its shape and distribution.

      Check this out: https://en.wikipedia.org/wiki/Bullet_Cluster

        • i_love_FFT@jlai.lu
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          4 hours ago

          How do you explain the mounting evidences of double images and observing the same event twice (or more) with exactly the expected delay by grav lensing?

          Anyhow, no new physics ever went against the old math, it always just adds corrective terms. Any new mathematics will need to be able to make the same predictions as GR in the limited cases of whatever this new limit will be (small distance or something?)

          The old saying that “Einstein proved Newton was wrong” is a gross misunderstanding. A nevessary base principle for GR to be accepter was that it reduces to Newtonian mechanics at low speeds.

      • someacnt@sh.itjust.works
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        18 hours ago

        I really don’t get the prevalence of the attitude “If we don’t see it with light, it does not exist”. Is it that improbable that there is some matter which does not interact with light? imo, similar argument could be made to deny existence of atoms - we cannot see it directly.

        • FooBarrington@lemmy.world
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          15 hours ago

          A big argument for “not all matter must necessarily interact electromagnetically” is that we know of particles which don’t interact with the strong force - why should that fundamental force be special?

      • NocturnalMorning@lemmy.world
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        17 hours ago

        Read your source. There’s lots of criticism in the source itself. If gravitational lensing was proof of dark matter, many someone’s would already have a Nobel prize for it. They don’t.

        • Soulg@ani.social
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          23 hours ago

          What are you talking about? We know for a fact dark matter exists. We just have absolutely no idea what it is.

          • skibidi@lemmy.world
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            20 hours ago

            What we know is that general relativity fails to explain gravitational interactions at very large scales for the matter we can see in telescopes.

            The simplest answer for this conundrum is that there is extra matter that we can’t see in telescopes - aka it is ‘dark’ matter. This substance doesn’t appear to interact at all outside of gravity - which is a property we haven’t observed anywhere else. Further, in order to explain the motions we see, it would have to outweigh all the visible matter in the universe by a factor of 5, which seems to strain credibility given that - again - we have never seen anything like it.

            Another answer for the observations is we are wrong about gravity, that it behaves differently at very large scales. This doesn’t require a massive amount of invisible magic substance conveniently spread throughout the universe, but to date no theory has been able to explain all the strange observations - and Dark Matter remains the moderate consensus view.

            This doesn’t mean dark matter absolutely exists, it is just a hole in our current understanding. We’ve been looking for it for nearly a century and have yet to find direct evidence. In fact, there isn’t even one theory of Dark Matter because it also has difficulty explaining every available observation.

            In summary: we have mountains and mountains of evidence that our current theory of gravity fail to explain the big stuff, we have exceedingly little evidence as to what the disconnect with reality is.

              • i_love_FFT@jlai.lu
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                4 hours ago

                The tone of your messages come off as a bit confrontational, that’s probably the reason sorry!

                Anyway, like many other situations before, there is probably no single fix to dark matter.

                There’s probably a huge swath of cold hydrogen that still goes undetected that would explain part of the small scale stuff (bullet cluster and such), and then some quantum gravity or modified gravity to explain the very low range stuff.

                Also, there are papers out there about how large scale simulations assume smooth distribution of matter, but then when computing with the actual distribution of matter, the some dark matter phenomenons tend to disappear.

                Anyhow, exiting stuff to get new physics to learn about!

          • NocturnalMorning@lemmy.world
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            23 hours ago

            Right, we don’t know what it is, where it is, how it interacts. We only know that our observations don’t match, so it must be there 🙄

    • Björn@swg-empire.de
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      1 day ago

      Dark matter can be detected through gravitational lensing. Rotation curves was just the first way we detected it.