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Is space materialistic?

  1. Oct 13, 2013 #1
    I've tried to google the answer but either I'm not reading it clearly or there is no actual answer, but is space materialistic? I know there are various analogies but is there an actual answer? Is 'empty' space itself an object?

    From what I understand stars and galaxies rest on the 'fabric' of space which causes it to dip thus producing gravity, but is space fabric even a real thing? If not then gravity itself doesn't really exist, it's just an effect of warped space and if the universe had no matter in it, there would'nt be any gravity?

    Someone please clear this up for me, if there is a common theory or something which is most likely the case but isn't confirmed yet please tell me what that might be.
     
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  3. Oct 13, 2013 #2

    Student100

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    There is no such thing as "empty space."

    I don't understand how you say that gravity doesn't really exist depending upon how it comes into existence. Gravity is definitely very real, regardless of the underlying mechanism behind it.

    If the universe had no matter in it, there wouldn't be a universe now would there?

    I'm not sure I entirely understand the question or what materialistic is.
     
  4. Oct 13, 2013 #3

    UltrafastPED

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    There are multiple answers to your question depending upon what you mean.

    For example classical physics treats space as having "nothing" in it - like an empty graph, but without the lines.

    General Relativity tells us that the graph does have lines, but that they may not be straight - and that the lines may change with time.

    Quantum mechanics tells us that "empty space" is filled with virtual particles which are due to "quantum fluctuations".

    Actual measurements tell us that space is never empty - that there are photons (cosmic background radiation) in every cubic meter, as well as other particles, especially neutrinos. Only the density of stuff changes.

    And these are only the standard theories!
     
  5. Oct 13, 2013 #4

    Chronos

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    Einstein posited space has 'no ponderable properties'. The 'fabric' of spacetime is an analogy that generally serves to confuse, rather than clarify.
     
  6. Oct 13, 2013 #5
    Then how is it possible that an object with x mass can curve space if there is nothing to curve? How can space curve if space isn't materialistic?

    I know this is only an analogy but surely you can appreciate how there needs to be some physical material to warp in the first place?

    http://www.messagetoeagle.com/images/spacetimeshockwave.jpg [Broken]

    Of course there would be. Take away all the galaxies including light and you have still the universe.
     
    Last edited by a moderator: May 6, 2017
  7. Oct 13, 2013 #6

    Nugatory

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    Take three small objects, not all located on the same line. They're real solid material objects.

    Stretch strings between them. These strings are also real solid material objects, and they form a triangle.

    Measure the internal angles of that triangle. Do they add to 180 degrees? If not, our three objects are set in a curved space... And I worked this out without ever having to consider whether the space is a material object.
     
  8. Oct 13, 2013 #7
    And you didn't answer anything relating to my question. I know space is curved... I accept it as fact but my question was: Is space itself materalistic?

    I know space is curved, but again I ask, how can something which isn't materalistic curve, bend, warp, stretch, contract whatever you want to call it.
     
  9. Oct 13, 2013 #8

    Nugatory

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    What we know and observe are material objects and the geometrical relationships between them. If the interior angles of the triangle added to 180 degrees, we wouldn't jump to the conclusion that space is a material object that happens to be flat; so if they don't add to 180 degrees we don't have to conclude that space is a material object that happens to be curved.
     
    Last edited: Oct 14, 2013
  10. Oct 13, 2013 #9

    Student100

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    You're stuck on this whole curving of space thing.

    Okay, taking away all matter is different than taking away ordinary matter. Taking away all ordinary matter will get you get a de sitter, radiation only type universe.
     
  11. Oct 14, 2013 #10

    Bandersnatch

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    Ask yourself whether you find it equally confusing that someting that isn't materialistic can have distance measured across it.
     
  12. Oct 14, 2013 #11
    Of course not because distance isn't a real physical thing. It's just a method of determining how far away two locations are. It doesn't require a physical medium.

    But for space to have characteristics such as being curved and warped it must have some kind of physical presence.

    A lot of the answers you guys have provided are similar to the ones I found from my Google search, there doesn't really seem to be a proper scientific answer. Is it just the case that we don't know?

    What would we see if we took an electron sized region of 'empty' space and magnified it to planck scale or further, would some sort of material start to emerge? If space isn't materalistic, then I'm just finding it hard to accept that something which technically is nothing, can have characteristics.
     
  13. Oct 14, 2013 #12

    Nugatory

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    And curvature is a property of the relationships between these distance measurements, such as whether the distance between two parallel lines is the same everywhere. Where's the real material thing there?
     
  14. Oct 14, 2013 #13
    The Michelson-Morley experiment demonstrated that there is no fabric of space. It surprised them, and the rest of the scientific community too.
     
    Last edited: Oct 14, 2013
  15. Oct 14, 2013 #14
    Thanks. I'll have a read of that in a minute. Still my question stands though, if 'empty' space has no structure, there is nothing to bend.
     
  16. Oct 14, 2013 #15

    WannabeNewton

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    You are using a very naive picture of curved manifolds based on the terrible analogies of "warping" and of "bending", both of which only make sense if the space-time manifold is embedded in a higher dimensional manifold; in GR we care only about the intrinsic curvature of space-time and this is not something you can picture in the above manner. Nugatory has already given a better reply than I can give so I just want to say that this is hinging on philosophy rather than physics.
     
  17. Oct 14, 2013 #16
    Thanks. I'll think about that later. Still my question stands though, if there is nothing pushing down on us, why do we stick to the ground?
     
  18. Oct 14, 2013 #17

    Nugatory

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    You might want to start a new thread in the relativity section for that question.... I don't mind taking a shot at answering it (actually, pointing you at some of the answers already out there) but it feels off-topic in a a thread about spacetime and materialism.
     
  19. Oct 14, 2013 #18

    Chalnoth

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    I think the clearest way to resolve this is to look at the fact that empty space can carry energy and momentum, in the form of gravitational radiation.

    And incidentally, there are a number of empty space-time manifolds which, nevertheless, have curvature.
     
  20. Oct 14, 2013 #19
    does space have any effect on matter or energy? Is the warping of space only a presumption?
     
  21. Oct 14, 2013 #20

    marcus

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    The paths that rays of light take, that is the effect of spacetime geometry. We see the effect of curvature in gravitational lensing of light (which is energy, if you like).

    When you drop something it falls. That is the effect of geometry being curved. The curvature is not "just a presumption".

    The paths free particles take are geodesics. Geodesics in a curved geometry (like the great circle routes over the Earth's surface that airplanes take) are the analogs of straight lines in flat space. Planets follow geodesics in the solar system's geometry.

    So yes, space (or more generally space-time) geometry DOES have an effect on matter and lightwaves. The effects are highly visible and evident.

    You might re-read Nugatory posts #6, 8, and 12. Having curvature does not mean that geometry (whether spatial or 4d) is a MATERIAL SUBSTANCE. We have learned that a bunch of geometric relationships can be physically real (somewhat like the lines of force of a magnet you might have played with as a kid) without being a material substance.
     
    Last edited: Oct 14, 2013
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