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  • None of the questions like these will ever be answered unless we can figure out what the rest of the matter in the universe is, be it dark matter itself or dark energy. We are at the point where our current level of understanding cannot make a step forward without that
  • That article was so dumbed down it was useless.  It may as well just have said, "because magic, dummy".
  • Unsung_Hero: That article was so dumbed down it was useless.  It may as well just have said, "because magic, dummy".


    A statement that's true for almost every pop-sci article about modern physics and astronomy.
  • Walls in space? Like at the galaxy's edge?

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  • According to that model, small galaxies should be distributed in messy orbits around larger galaxies. However, most small galaxies orbiting larger galaxies are arranged in thin flat planes. These planes, or disks, look similar to the rings of Saturn. Almost as if there is some invisible wall in space that the galaxies arrange along.

    The Solar system exists in more or less a single flat plane because it condensed out of a single cloud of spinning dust and gas.  Shouldn't galaxy clusters evolve more or less the same way?  Why need an exotic explanation?
  • That's because the universe isn't real

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  • Mouser: According to that model, small galaxies should be distributed in messy orbits around larger galaxies. However, most small galaxies orbiting larger galaxies are arranged in thin flat planes. These planes, or disks, look similar to the rings of Saturn. Almost as if there is some invisible wall in space that the galaxies arrange along.

    The Solar system exists in more or less a single flat plane because it condensed out of a single cloud of spinning dust and gas.  Shouldn't galaxy clusters evolve more or less the same way?  Why need an exotic explanation?


    Individual galaxies, sure.  But on the multi-billion year scale, galaxies grow by absorbing other galaxies during collisions, and smaller galaxies can be created by this process or pulled into orbit around the larger structure.  There's no particular reason that galaxies produced by a merger or captured due to proximity should be in the same plane.
  • lifeslammer: None of the questions like these will ever be answered unless we can figure out what the rest of the matter in the universe is, be it dark matter itself or dark energy. We are at the point where our current level of understanding cannot make a step forward without that


    We figure that out by observation and testing predictions of the various models, which is what TFA is talking about. The only known interaction of dark matter is via gravitation. We see its effects. Exactly what causes those effects is still up in the air. They are slowly excluding possibilities as predictions fail.
  • BolloxReader: lifeslammer: None of the questions like these will ever be answered unless we can figure out what the rest of the matter in the universe is, be it dark matter itself or dark energy. We are at the point where our current level of understanding cannot make a step forward without that

    We figure that out by observation and testing predictions of the various models, which is what TFA is talking about. The only known interaction of dark matter is via gravitation. We see its effects. Exactly what causes those effects is still up in the air. They are slowly excluding possibilities as predictions fail.


    We assume it's a particle because that' all we have to work with.  It's almost as if we don't know what space and time are made from.
  • Marcus Aurelius: We assume it's a particle because that' all we have to work with


    Well, no, we assume it's a particle because it interacts with fields, and particles are the thing which carries field interactions. Thus the electromagnetic field can produce photons. It's sort of a tautology, but not in a bad way. Dark matter interacts with gravitational fields, thus there must be a particle that carries this effect.
  • In solar systems like ours and galaxes, bodies tend towards a plane around the central object (all the planets are in the same plane and most of the gas and asteroids), Why wouldn't satelllite galaxies do the same and tend towards the same plane like a middle aged man's belly fat?

    I'm not a scientist, nor do I play one on the web, but I don't think you need a new partical to explain mere mechanics.
  • Angular momentum. The conservation of, unless I am very mistaken. And I could well be, but prove me wrong.
  • brantgoose: In solar systems like ours and galaxes, bodies tend towards a plane around the central object (all the planets are in the same plane and most of the gas and asteroids), Why wouldn't satelllite galaxies do the same and tend towards the same plane like a middle aged man's belly fat?

    I'm not a scientist, nor do I play one on the web, but I don't think you need a new partical to explain mere mechanics.


    Nope. A solar system is bound to its star, which is why everything always forms on the same plane as the stars rotation. A star is 99.9999999% of the mass in a solar system.

    A galaxy is not bound to its central black hole. Even our own galaxy, which has a central black hole of 6.5 billion solar masses. While that sounds like a really big and hefty number (and it is), the total mass of the galaxy is estimated to be 1.2 to 1.9 trillion solar masses, likely closer to the larger side. So even if we call it 1.5 trillion, Sag A (our central black hole) only makes up .0043% of the total galactic mass. It doesnt have nearly enough mass to influence the entire galaxy.

    We have no idea about the process of galactic formation, because its such a stupidly long timescale and we have not yet been able to see enough of how other galaxies are to make a decent theory on it. What we know is a drop in a bucket compared to what we dont know on this. The only part of galactic knowledge we really have is a puzzle: All the stars rotate the central black hole at the same rate, like the arms on a clock. We theorize its because dark matter holds it all in place somehow, because otherwise the stars closer to the center would be moving insanely fast compared to the stars on the edge, much like how planets rotate around a star. But they dont.

    We still have a very long way to go on our path of understanding the universe. Its ok, its fun to take the path. But something like this is probably an answer we cant get until we can understand the how and why of galaxy formation in all its forms
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