6 ms·

Perhaps we could call that thing: "dark matter" for now. In seriousness, we can observe the effect, and even map the distribution of the stuff.

• drewg123 8y ago
  That assumes that it is "matter". Maybe there is something we just fundamentally don't understand about gravity.
  • improbable22 8y ago
    This is another possibility, and would be exciting. But it's very very hard to come up with plausible models for such modified gravity. There are lots of people trying, and their ideas tend to break all sorts of other things we know. For example (IIRC) lots of candidates gave a slightly different speed for gravitational waves, and were ruled out by recent detections where we also saw X-rays from the same event.
  • _ph_ 8y ago
    Sure, but all data we have rather points out to some undetected matter than problems with the theory of gravitation. The article shows several measurements which would be well explained with particles we did not detect yet.
  • dTal 8y ago
    They've thought of that: https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics It doesn't really work. Overwhelmingly the evidence points to mass, which is gravitationally affected by other mass, and nothing else. I know the mind rebels against the notion of invisible matter, but is it really so much more implausible than the invisible spookiness of gravity to begin with? If the scientific evidence points that way, your monkey-brain intuitions do not provide a reliable veto.
    • auntienomen 8y ago
      Of course, neutrinos are invisible, and no one seems to have much of a problem with them anymore.
    • bmiranda 8y ago
      MOND does work a lot better than Lambda Cold Dark Matter (L-CDM)... but only for explaining the rotation of galaxies. It can explain this rotation almost perfectly given only the mass distribution: no tuning is required. Dark matter, on the other hand, has issues with dwarf galaxies and has no predictive power: you just fit the dark matter to the results you observe (Which is why you end up with some dwarf galaxies that are almost entirely composed of dark matter, and ones that almost have none. With MOND it just works). Of course MOND can't really explain the third peak of the cosmic microwave background radiation, so it isn't perfect either. It is also phenomenological, with no underlying physical theory at the moment. Still, it's surprising that it does work at all. I should also mention that the bullet cluster, which is touted as proving dark matter, causes issues for dark matter as well as MOND. The velocities involved in the collision are higher than can be explained by the current dark matter models. MOND kind of sucks at dealing with clusters, as well. TL;DR MOND is a lot better than LCDM at explaining galaxy dynamics, LCDM is a lot better than MOND at explaining the cosmic background radiation. Both aren't that great at dealing with clusters (but you can also make dark matter work with enough fiddling). https://tritonstation.wordpress.com/2018/09/04/dwarf-satellite-galaxies-and-low-surface-brightness-galaxies-in-the-field-i/ https://tritonstation.wordpress.com/2018/09/04/dwarf-satelli...
  • gbrown 8y ago
    That's not impossible, but I tend to believe the experts when they say it's not likely (and have explicitly ruled out several such explanations).
• sonnyblarney 8y ago
  "In seriousness, we can observe the effect, and even map the distribution of the stuff." No, we can measure the dissonance between our best theories and reality. And make a conjecture about 'stuff'.
  • gbrown 8y ago
    I'm not a physicist, but my basic understanding of the state of the science tells me you're simply incorrect. We can observe the effect of dark matter via gravitational lensing, and folks much smarter than me have devised studies to exclude differential behavior of gravity at classical and galactic scales. Give me a recent and well supported study indicating that dark matter may be something other than matter, and I'll happily read it. My understanding is that the existence of dark matter is uncontroversial among physicists, and that the best bet is some sort of WIMP.
    • tylerjwilk00 8y ago
      This assumes that we are 100% certain that our understanding of gravitational lensing is accurate _AND_ that only mass affects gravitational lensing.
      • gbrown 8y ago
        Nothing in science is assumed with 100% certainty. I would argue that working from our best available theories (while always looking for ways to falsify them) is perfectly reasonable.
    • reitanqild 8y ago
      As a non-physicist I assume the physicists have thought really hard about this. But it feels very strange to accept something that: - is a particle - doesn't interact with other normal particles (except through gravitation) - doesn't interact with particles of its own kind
      • roywiggins 8y ago