• Tlaloc_Temporal@lemmy.ca
    link
    fedilink
    English
    arrow-up
    0
    ·
    2 days ago

    Not thinking of cosmic expansion as a volume expanding is an interesting thought.

    It does imply that the changing distance only happens at large distances though. “Faster-than-light” expansion is already non-local (I think), but all expansion being non-local is consistent with it being driven by vacuum energy. That kinda makes the rasin bread analogy stronger, as the rasins don’t expand at all.

    I wonder if we could detect frame-dragging at large distances. If expansion causes frame-dragging, then it’s actually a change in space, not just distance.

    I wonder if linear motion can even cause frame-dragging, or if it’s just rotation that causes it. I do not know enough about the math to say.

    • wholookshere@lemmy.blahaj.zone
      link
      fedilink
      English
      arrow-up
      0
      ·
      edit-2
      2 days ago

      So it does happen on a small local scale though. It happens on ALL scales.

      But everything is expanding from everything. Meaning the observer is always centred of the expansion. This is because volume is constant. The rasins themselves do expand, but locally it’s such a small scale (10^-23 m/s for our solar system).

      This also works for how we understand the change in density. Volume is constant, but we’ve gone from infinitely dense to almost nothing.

      • Tlaloc_Temporal@lemmy.ca
        link
        fedilink
        English
        arrow-up
        0
        ·
        2 days ago

        We went over this, we observe the distance between galaxies increasing, but the distance between atoms has not.

        The expansion happens everywhere, but subatomic forces massively overpower the expansion, so atoms don’t expand.

        Likewise, raisins are strong enough to not get pulled apart by the expanding bread. There may be slight force on them, but the bread expanding by a factor of 2 leaves the raisins the same size.

        I don’t understand how you think a change in distance can be detectable by light between galaxies, but not detectable by like between ends of a metre bar, or between electrons.

        • wholookshere@lemmy.blahaj.zone
          link
          fedilink
          English
          arrow-up
          0
          ·
          2 days ago

          You are correct that the raisins would have other constraints to keep it from infitatly expanding into nothing. Not because it’s not expanding but because it has external constraints like gravity keeping it there.

          They do have expansion applied to them, but gravity and other things effecting space time would be keeping it on place.

          As for attoms, I think you picture something solid. But there’s not. The electrons are getting further from the nucleas, but it’s still bound quantum mechanically to the attoms regardless of its position.

          But then the nucleas isn’t soldi either. It’s made of smaller things yet, and so on and so forth. So inside would also be expanding. But again other forces at play would bind things together.

          The expansion is also not a force. It can’t overcome other forces so it keeps things in line.