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Did Big Bang stretch space?

  1. Jun 9, 2014 #1
    I watched a BBC video - Wonders of the Universe where the scientist explains that the Big Bang stretched the universe and created space. Is it true?

    If the above assumption is true, is the space within atom (distance between nucleus and electron) stretched as well?
     
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  3. Jun 9, 2014 #2

    HallsofIvy

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    I will agree that space itself was created at the Big Bang but I don't know what "stretched the universe" could mean!
     
  4. Jun 9, 2014 #3

    phinds

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    The whole concept of space as a "fabric" that can be bent or stretched is often discussed on this forum. The consensus is that it is a totally useless concept with no real meaning. Google "metric expansion" and/or see the link in my signature.
     
  5. Jun 9, 2014 #4

    Bill_K

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    I agree, it's a misleading oversimplification of what really occurs. But unfortunately, so is "metric expansion"! :wink:
     
  6. Jun 9, 2014 #5

    phinds

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    What is misleading about metric expansion? I've always seen it mentioned on this forum as a solid explanation.
     
  7. Jun 10, 2014 #6

    timmdeeg

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    In this context stretching doesn't mean creation of space, but most probably the enormous expansion of the universe by a factor > 10^30 (depending on the model) during the period of inflation. As was said already expansion should be understood as metric expansion.
     
  8. Jun 10, 2014 #7
    The BBC video was produced by Prof. Brian Cox. According to him, the space that we inhabit is the same space that existed at Big Bang.
     
  9. Jun 10, 2014 #8

    phinds

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    You would really do better to get your physics from somewhere other than pop-sci TV programs. Sometimes they get things right but they NEVER get everything right.

    The "big bang" really has two meanings. First the "big bang singularity" and second the "big bang theory". The "singularity" is just the name for WHATEVER it was that happened before the big bang theory takes over. We don't know what that was. The big bang theory is a pretty well understood description of what happened AFTER the singularity, starting at about one Plank time after it.

    So saying that
    is fine if you mean that it is the space that existed AFTER the singularity
     
  10. Jun 10, 2014 #9
    Is my conclusion that spacing between nucleus and electron proportionally lower just after the Big Bang singularity?
     
  11. Jun 10, 2014 #10

    phinds

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    No, spacing of objects below the level of galactic clusers (that is, galaxies, solar systems, atoms, etc) is not affected. I say AGAIN:
     
  12. Jun 10, 2014 #11
    the big bang singularity is a point in which our knowledge of physics can no longer explain what is going on this is prior to 10-43 seconds. The Hot big bang model, doesn't predict how the universe started, it only explains that the universe started at a hot dense state of unknown size and origin.
    Space in and of itself is only geometric volume, it has no physical properties or energy to be warped, twisted stretched, etc. the statements curves space etc is misleading in that regard as it implies space has some separate property.
    The geometric volume of space is filled with the existing energy mass contents of the universe as expansion occurs. So nothing is created, as space expands only the volume has changed
    How particles and forces influence each other have mathematical geometric relations of influence, as the particles etc being measured occupy the volume of space, GR will use the term space-time curvature. Which describes how gravity influences the matter residing in space. (not that space itself has a property)

    Universe geometry is the same in that the shape of the universe is a mathematical descriptive of the energy-density relations of all contributors,(matter,dark energy,gravity, etc) will have positive or negative pressure relations with one another, if the total energy-density is the same as or close to the critical density then the universe is flat. This is essentially a pressure distribution relation.

    see here for more detail on Universe geometry
    http://cosmology101.wikidot.com/universe-geometry p
    page 2
    http://cosmology101.wikidot.com/geometry-flrw-metric/

    As expansion occurs there is simply more volume, the rate of expansion depends on the energy density relations as per above, energy-density of a type (radiation, matter, dark energy etc) has a corresponding energy-density to pressure relations is determined by its equation of state.
    http://en.wikipedia.org/wiki/Equation_of_state_(cosmology)
     
  13. Jun 10, 2014 #12
    Thanks, makes sense. Some mysterious thing pulls all objects which are unbound by gravity or nuclear forces. So, does not apply to atoms.
     
  14. Jun 10, 2014 #13
    as to this question, in the early universe the temperatures was too high for atoms to form with stability, any atoms that did form would quickly decouple. Essentially all particles are in a state of thermal equilibrium. As the volume of space increases, the temperature drops in accordance to the ideal gas laws. So does the overall density. (atoms could not form until after inflation)

    PV=nRT.

    http://en.wikipedia.org/wiki/Ideal_gas_law

    when the temperature drops enough different particles will drop out of thermal equilibrium. stable reactions of those particle species will start to form. However they drop out at different temperatures depending on which particle species etc. more details can be found in these two articles

    http://arxiv.org/pdf/hep-th/0503203.pdf "Particle Physics and Inflationary Cosmology" by Andrei Linde
    http://www.wiese.itp.unibe.ch/lectures/universe.pdf :" Particle Physics of the Early universe" by Uwe-Jens Wiese Thermodynamics, Big bang Nucleosynthesis

    when you study cosmology in detail, it doesn't take long to realize that many of the metrics involved include the perfect fluid aspects and relations of thermodynamics in their equations. The FLRW metric and Einstein field equations included.
     
    Last edited: Jun 10, 2014
  15. Jun 10, 2014 #14
    by mysterious thing pulling on things you might be referring to the cosmological constant or dark energy. The energy-density of the cosmological constant is easily overpowered by the strong force and gravity. Its influence is only at extremely large scales, (such as the regions between galaxy clusters).

    expansion only influences the regions of space not gravitationally bound or the strong force. Its energy density per volume is too small to overcome gravity or the strong force.
     
  16. Jun 10, 2014 #15
    .... You can generalized it that way. It just that the thing that drove the expansion of space is very diffuse in proportion to let say an atom. It doesn't have a continuous work against the other forces that affects or binds an atom but it can be interpreted this way. The accelerated expansion can have a very small constant, a negative force between electron and nucleus that makes an atom slightly bigger than an atom in a non-accelerating universe model. However, Dark energy is treated as constant vacuum energy and it would a appear that atom already as it is.
     
  17. Jun 11, 2014 #16
    If gravity according to GR is the warping of space, and even the earth can exhibit frame dragging, then why is it incorrect to talk about the fabric of space? It seems to violate common sense, but then so does QM. And metric expansion seems like a proxy phrase.
     
  18. Jun 11, 2014 #17
    the warping of space in GR is often misunderstood, the term spacetime has special meaning in physics

    "In physics, spacetime (also space–time, space time or space–time continuum) is any mathematical model that combines space and time into a single interwoven continuum".

    In other words the warping is simply a mathematical descriptive used in GR to describe the geometric relations between gravity and matter.(including light paths,etc) Not space itself, GR does not state that space has a fabric or substance.

    any form of physics deals with mathematical relations, even particle physics. Most of the equations used in particle physics are in actuality differential geometry equations.
     
  19. Jun 11, 2014 #18

    Drakkith

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    Mordred is correct. GR is a theory of geometry. In GR space-time is not represented by a "fabric", but with a mathematical description known as a tensor that describes how the geometry of space-time will affect objects, and how objects will affect the geometry of space-time. In other words, it describes how objects interact with each other by changing the geometry of space-time.

    Note that there is NO description of a fabric, sheet, or anything else analogous to a physical object. It's pure geometry.
     
  20. Jun 13, 2014 #19
    I know the Einstein GR equation is a tensor equation, and what tensors are. But GR must describe something physical , not just abstract differential geometry. If it changes the interaction of objects by changing the geometry of spacetime, then spacetime is something physical whose geometry can be changed. Of course the equation(s) do not mention fabrics, rubber sheets, or warping. Its a bunch of equations, or if you like G=T. Those are how physicists, including some very first-rate ones, have tried to explain GR to the lay public.
    If GR is a theory of geometry, it belongs to math, not physics. This is the first time I've heard it described as a theory of geometry.
     
  21. Jun 13, 2014 #20

    Drakkith

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    That depends on what "physical" means in this context, but I don't want to get into an argument over the meaning of words.

    When I say that GR is a theory of geometry, I mean that it uses geometry to describe real, observable phenomena. The theory makes predictions that can be tested, and these tests have been verified. The theory accurately describes gravity, no one can argue this. As such, it is not a theory of math, it is a physics.
     
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