• wax
    301
    Does mass cause space-time curvature, or does space-time cause the presence of matter?

    Or another option, they have root causes, but are not directly causally linked...?
  • TogetherTurtle
    344
    These seem to be questions about the very nature of the universe that can't (currently) be observed in any way, and observation is necessary for determining these things.

    We can examine that time slows down the closer you are to the center of mass of an object, but there are no rules as for why or which is a result of which. Unless we discover a new part of the universe that we didn't know existed (a new sense, akin to sight or smell, or something that tools can sense like UV radiation) I don't think we can solve this. Or there is some way to look at what we already have that we just haven't gotten to yet.
  • wax
    301


    one thing I just remembered reading is that, space-time curvature doesn't behave like..like the sound of a jet as the jet travels along; there is no bunching up of the space-time curve for fast moving objects...I think it is supposed to stretch out ahead of the matter(eg planet|)...this could indicate that the space-time curve and the matter are not directly linked, but have root causes instead, maybe...
  • tim wood
    3k
    there is no bunching up of the space-time curve for fast moving objects...I think it is supposed to stretch out ahead of the matterwax
    Could you try again at this? I don't understand it as written.
  • TogetherTurtle
    344
    one thing I just remembered reading is that, space-time curvature doesn't behave like..like the sound of a jet as the jet travels along;wax

    So no doppler effect for space-time? Interesting.
  • wax
    301
    Could you try again at this? I don't understand it as written.tim wood

    take a planet in this diagram moving at a uniform velocity from left to right.

    Untitled.jpg

    I would maybe think if mass caused space-time curvature, you'd get the curve represented in a.

    and maybe if space-time curvature caused mass; you'd get b.

    But from what I have read, we get c.

    Which indicates to me that space-time and mass are not causally linked, but that they perhaps have a root cause.
  • Andrew M
    711
    Does mass cause space-time curvature, or does space-time cause the presence of matter?wax

    Perhaps of interest, John Wheeler's pithy summary of GR was "Spacetime tells matter how to move; matter tells spacetime how to curve."
  • tim wood
    3k
    Hmm. Pretty interesting. It does seem to me that mass interacts with space, i.e., gravity, at the speed of light. As most mass moves really slowly, space would "smooth out."

    I'd guess with you option a, but space would "adjust" very quickly. I'd really like to know the right answer though. I suspect your word "cause" is correct in mass causes curvature, but incorrect in curvature causes mass. If the curvature is prior, then what causes it?
  • andrewk
    2.1k
    Objects move through space, not through space-time. To move through space-time would require an additional time dimension with respect to which that motion was measured. So we'd need five dimensions all up.

    Rather, the motion of an object is represented as a fixed curve in the 4D spacetime manifold.
  • wax
    301
    Perhaps of interest, John Wheeler's pithy summary of GR was "Spacetime tells matter how to move; matter tells spacetime how to curve.Andrew M

    yes, I've heard that before...and it was referenced in the Hitchhiker's Guide to the Galaxy . :)

    but if taken seriously, that implies a causal relationship...which comes first, space-time telling matter how to move, or matter telling space time how to curve?

    if there is a non-zero time between that communication then there should be a time delay, and that would mean that curvature was transmitted through the system over time, but that doesn't seem to be the case, as far as I can tell.

    If there is instant communication between matter and space-time, then the two don't seem to be linked causally, but might have a common root.
  • wax
    301
    Rather, the motion of an object is represented as a fixed curve in the 4D spacetime manifold.andrewk

    yes, that makes sense.
  • Terrapin Station
    12.4k
    Space and time aren't "things in themselves," they supervene on matter and its relations.
  • wax
    301
    Space and time aren't "things in themselves," they supervene on matter and its relations.Terrapin Station

    yes, maybe.

    But if you could somehow see space-time...but couldn't see matter, could you put it the other way, ie
    'matter isn't a thing in itself, it just supervenes on space-time and its relationships' ?

    or maybe separating space-time into space and time:
    'matter and time aren't things of themselves, they just supervene on space and its relationships'?

    just a thought.
  • Terrapin Station
    12.4k
    But if you could somehow see space-time...but couldn't see matter, could you put it the other way, ie
    'matter isn't a thing in itself, it just supervenes on space-time and its relationships' ?
    wax

    I don't know how that would make sense, though. I can't make sense of there being anything that's not matter or some relation of matter.
  • Marchesk
    2.8k
    Space and time aren't "things in themselves," they supervene on matter and its relations.Terrapin Station

    That's one view. But matter might supervene on fields that also make up space and time. Consider the earliest point in the universe right at the Big Bang. Did matter exist then, or did it form because of how things went down with symmetry breaking and inflation or what not?
  • Marchesk
    2.8k
    I don't know how that would make sense, though. I can't make sense of there being anything that's not matter or some relation of matter.Terrapin Station

    What about fields and energy? What makes matter more primary?
  • Terrapin Station
    12.4k


    As anything independent of matter and relations, I can't make any sense of them (and I don't believe that's my flaw)
  • Marchesk
    2.8k
    But then what about cosmology? Was matter there at the beginning?

    As for not understanding, we have math to help with that. Why should we expect to understand something so far removed from everyday experience? It's not like we evolved to be physicists or philosophers.
  • Marchesk
    2.8k
    So was it a quark soup?
  • Terrapin Station
    12.4k


    I don't believe that anyone has any idea what the universe would have been like at the start of time, or even if there was start. Current theories centered on the big bang are primarily the result of reifying mathematics.
  • Marchesk
    2.8k
    Current theories centered on the big bang are primarily the result of reifying mathematics.Terrapin Station

    That does raise the question of what matter is. Tegmark has a point about physical properties being mathematical.
  • Terrapin Station
    12.4k
    That does raise the question of what matter is. Tegmark has a point about physical properties being mathematical.Marchesk

    Matter = "chunks of stuff" basically. I'm an antirealist on mathematics (and all abstracts period).
  • Marchesk
    2.8k
    So chunky stuff all the way down?

    I go back and forth on the reality of mathematics.
  • Terrapin Station
    12.4k
    So chunky stuff all the way down?Marchesk

    Yes. I don't believe that the idea of an existent that isn't something (a la a chunk of something) makes any sense. The idea of "disembodied properties" doesn't make any sense.
  • Metaphysician Undercover
    6k
    But if you could somehow see space-time...but couldn't see matter, could you put it the other way, ie
    'matter isn't a thing in itself, it just supervenes on space-time and its relationships' ?

    or maybe separating space-time into space and time:
    'matter and time aren't things of themselves, they just supervene on space and its relationships'?
    wax

    This is an interesting thought experiment. Let's say that we "see" space-time with our minds, in the sense that we apprehended it only with the mind. And matter is somewhat unintelligible so we do not "see" matter with the mind. Now, we have observed the existence of objects, and their movement, and from this we have apprehended with the mind, the conception of space-time. However, something is missing here, and that is the substance, what gives reality to the objects which are observed to be moving. So we posit "matter" as that substance, the reality of the objects which are moving.

    So, would you agree on this? Our understanding of "matter" is dependent on our understanding of space and time, which itself is based in observations of moving objects. Now, if our concepts of space and time change, due to changing empirical data, so must our concept of matter. However, let's say that space, time, and matter all refer to something real, and this is what we observe as objects and their movements. We need to disentangle these three aspects of objects in motion (which forms our empirical data) in order to properly answer your questions.
  • TheMadFool
    3.8k
    Does mass cause space-time curvature, or does space-time cause the presence of matter?

    Or another option, they have root causes, but are not directly causally linked...?
    wax

    Interesting question.

    What do the scientific equations say?

    If space-time curvatures cause matter (mass) instead of the other way round (matter causing space-time curvatures) then shouldn't objects be popping into existence around massive objects like stars and blackholes, afterall it's these regions that experience maximum space-time deformations right?
  • wax
    301
    If space-time curvatures cause matter (mass) instead of the other way round (matter causing space-time curvatures) then shouldn't objects be popping into existence around massive objects like stars and blackholes, afterall it's these regions that experience maximum space-time deformations right?TheMadFool

    funny you should mention black holes. I don't believe the mainstream view of them and think that event horizons don't form, but Hawking Radiation is based upon the idea that particles do get created just outside of the event horizon. One falls back in and the other radiates away....this particle creation isn't limited to black holes, but the falling back in, and the radiating away can happen near them.
  • TheMadFool
    3.8k
    So your theory is plausible. Spacez-time deformations can produce mattee???
  • wax
    301
    So your theory is plausible. Spacez-time deformations can produce mattee???TheMadFool

    no, I'm not sure if one causes the other, only that they have root causes, and always exist together.
  • TheMadFool
    3.8k
    Oh I see. Are you familiar with the equations? Are they symmetrical?

    One problem I see is we can't test your theory. We need matter to deform space-time and in the event that matter is produced (you mentioned particle formation by black holes) you wouldn't be able to know if it was the black hole mass or the space-time deformation that produced the particles.

    Unless we can deform space-time without matter.
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