The fabric of space-time

Discussion in 'Physics & Math' started by Saint, Feb 12, 2020.

  1. Q-reeus Valued Senior Member

    Messages:
    4,083
    Seems I'm the only one willing to call out repeated errors here.
    A fairly balanced perspective on what is speculation - like 'it all began at t = 10^-43 seconds' - vs what is reasonably well understood re initial BB phase:
    https://www.einstein-online.info/en/spotlight/big_bangs/

    Back in #2, this bold font assertion was made:
    The concept of spacetime follows from the observation that the speed of light is invariant.
    In #10 it was explained why that is simply false. Here again is the main article exploding that misinfo:
    philsci-archive.pitt.edu/13227/1/cst2.pdf

    And lately we are directed to an article purporting an infinitely old, infinitely large, infinitely dense, yet spatially flat universe that by an impossible miracle decided to undergo a perfectly synchronized BB-style expansion everywhere, after waiting an infinite time to do so. Ned Wright tries to make sense of that using simple pictorials.
    Thankfully, it now seems almost certain that bizarre notion is wrong. Recent analysis of Planck data strongly indicates a finite sized universe after all:
    https://arxiv.org/abs/1911.02087
     
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  3. paddoboy Valued Senior Member

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    If only!
    No wrong q-reeus. The BB model simply only goes back as far as t+10-43 seconds. Nothing I said refers to any beginning, except of course the logical beginning of space and time [as we know them] when extrapolated back to t. The rest we need a validated QGT to describe with any sort of confidence.
    No q-reeus, just a simple assertion as in line with GR.
    The assertion stands as far as I am concerned and in line with GR.
    Nothing bizzare about it q-reeus and as far as I am aware it still holds with the main accepted view. And of course "the everywhere occurrence of the BB" is in relation to the observable universe as far as I am aware.
    Yep, nice paper q-reeus, but one paper does not a Summer make.
    You have in the past offered up other papers that were supposedly destined to wreak havoc and invalidate GR.You do realize and accept that all that has failed so far q-reeus? They also have failed, or at least have just faded into oblivion and lost in cyber space.
    Again according to latest data, cosmologists are still not yet able to determine whether the universe is finite or infinite, particularly when possible exotic topologies are considered.
    On face value though, a flat universe seems to indicate one that is infinite.
    Hope that helps.
     
    Last edited: Feb 18, 2020
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  5. Q-reeus Valued Senior Member

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    Hahaha. Counterargument by either bald assertion or deflection. No-one else seems to care for truth and accuracy here, so just carry on. It's mostly idle entertainment at SF after all is said and done.
     
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  7. paddoboy Valued Senior Member

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    Like I said q-reeus, you have been quoting and linking to papers that supposedly have invalidated GR for years now and havn't made any dint. Why is that? Is this to do with metaphysics and your personal beliefs in ID?
    Many other such fanatics also rail against accepted science for similar reasons...being the top rung on the ladder so to speak, to rip that out would be pretty impressive. The same applies to going against science as far as Aliens and UFO sightings are concerned, and the ultimate craziness of such beliefs is more often then not also entailing and encompassing silly conspiracy nonsense, like supposed 9/11 cover ups for example.
     
  8. Q-reeus Valued Senior Member

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    4,083
    What nonsense. GR and ID have absolutely nothing in common. As for GR being inherently flawed, that was covered numbers of times elsewhere.
    And btw, VTG, which I never adopted as gospel, is far from 'dead': https://arxiv.org/abs/1802.01193
    Let's see if James R picks you up for engaging in outlandish trolling here. I doubt it - evidently some kind of uneasy truce has been worked out. Charmed life continues.
     
  9. paddoboy Valued Senior Member

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    27,534
    The only things so far inherently flawed, is your total opposition to GR, including your failures elsewhere to convince. And your link does not invalidate the general consensus.
    It's still on life support though!

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    The only things so far inherently flawed, is your total opposition to GR, including your failures elsewhere to convince.
    Actually quite a connection and far from trolling.
     
    Last edited: Feb 18, 2020
  10. paddoboy Valued Senior Member

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    Again, we have as yet no firm data to suggest an infinite or finite universe, other then WMAP, Boomerang and Maxima pointing to a flat universe and infinite in extent, if exotic topologies are excluded.
     
  11. Saint Valued Senior Member

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    4,139
    i can imagine the fabric of time-space in 2D, but we know the world is 3D, does it mean a 3D world consists of multi-layers of 2D fabric stacked together?
     
  12. geordief Valued Senior Member

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    1,480
    Yes ,you can peel off the sole of your shoe and that is one of the layers.
    Hens are also good layers and ,obviously they are 3d layers.
    Plenty of other examples .Duvet covers are both layers and fabric.
     
  13. Write4U Valued Senior Member

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    15,852
    When speaking of "fabric" of space, time is not a required property.

    Three-dimensional space
    https://en.wikipedia.org/wiki/Three-dimensional_space

    However, the way the fabric of space unfolds is a mathematical function, proposed by Renate Loll et al, named Causal Dynamical Triangulation (CDT)
    https://en.wikipedia.org/wiki/Causal_dynamical_triangulation

    Note that in this process time has not prior existence and emerges only as a result of the chronology and duration of the unfolding fabric of space.
     
    Last edited: Mar 7, 2020
  14. Asexperia Valued Senior Member

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    1,615
    The concept of space-time originates from multiplying time times the speed of light turning time into distance. Time is a dimension of space in the Theory of relativity.
     
  15. paddoboy Valued Senior Member

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    27,534
    Actually space has three dimensions and time is the fourth.
    The terminology "fabric" is an analogy that can be misleading particularly to those with an agenda.
    As our descriptive model, the BB, tells us, space and time [as we know them] evolved/expanded from a hot dense state, at 10-43 seconds. As space evolved, so to did time: As time evolved, so to did space. Or putting that another way, within GR space and time are interchangeable within the multi dimensional framework we call spacetime.
    GR tells us that clocks tick at different rates depending on there position in curved spacetime [a gravity well] ....the further down, the slower a clock will appear to tick to someone further up.
     
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  16. Asexperia Valued Senior Member

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    1,615
    Is space-time something physical (distances) or something mathematical ?
     
  17. paddoboy Valued Senior Member

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    Obviously space, time, or spacetime are not physical...no one ever inferred that they are, but that does not make them any the less real.
     
  18. arfa brane call me arf Valued Senior Member

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    So what is physical? Are metres and seconds physical?
     
  19. Write4U Valued Senior Member

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    Something mathematical......

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    https://en.wikipedia.org/wiki/Spacetime
     
  20. paddoboy Valued Senior Member

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    What is physical? Something pertaining to materialism.
    Metres and seconds are physical measurements, generally pertaining to something material. The measurements are real enough, depending on one's definition of "real"

    By the same token spacetime can be bent warped, lensed twisted etc, plus are interchangeble with the possibility of your time and space being different to my time and space. That is also real enough. But it aint physical.
     
  21. arfa brane call me arf Valued Senior Member

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    So are you trying to distinguish between physical measurement and 'something material'?
    Well, again, it's hard to see how spacetime can be bent or stretched and so on but "aint physical". If gravity is physical and gravity can bend or curve something that isn't physical, that's quite the thing, I say.

    So it depends on whether you can say spacetime is material, or isn't.
     
  22. paddoboy Valued Senior Member

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    Again, it gets down to the nitty gritty of how one defines "real"
    Space is what exists between you and I...it is real. Time is what stops everything from happening together...and without time, there is no space. Space is real. There is no absolute FoR...space and time are not fixed...there is no universal "now" ...space and time are also interchangeble and effectively two sides of the same coin...without spacetime there is no location...spacetime can be bent, warped, twisted in the presence of mass/energy. Spacetime is real. But none of those are physical material objects.
    https://www.dictionary.com/browse/physical
    of or relating to that which is material:the physical universe; the physical sciences.
    noting or pertaining to the properties of matter and energy other than those peculiar to living matter.
    pertaining to the physical sciences, especially physics.
    """""""""""""""""""""""""""""""""""

    Yes, spacetime certainly is a mathematical framework against which we locate events and describe the relationships between them in terms of spatial coordinates and time, as well as the geometry of the universe. While it is not physical we are still describing something which is the geometry of said spacetime.
    That geometry and structure is real.
    I fail to see any problem with those obvious definitions and properties.
    There are some nice summations in the following.... [and one or two questionable statements] https://www.quora.com/Is-spacetime-a-real-thing-or-just-a-mere-concept#:~:text=“ there is no absolute frame,yeah space-time is real.
     
  23. arfa brane call me arf Valued Senior Member

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    7,150
    Quite. Actually what the word real means was debated by the ancient Greeks; and not just them.

    But spacetime can have energy in it; indeed, curvature due to mass energy is locally experienced (i.e. measured) as gravity. Gravitational waves change the geometry, hence the local energy, in regions of spacetime as they propagate.
    Well, once again, you need something here that explains how the geometric ("real") properties of spacetime are distinct from spacetime itself. Or, when does an object become distinct from its properties?
     

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