Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

New Theory of Space

  1. Nov 5, 2008 #1
    Space is expanding. In other words, space is moving, or changing.While we continue to think of relativity in terms of masses moving with regard to themselves in space, thereby generating time, there is a limitation to this.
    Since space is moving. Suppose a body A and a body B hover in space such that their movement is governed by the movement of space only. Than we have model in here where two things can happen.
    1. A and B can move further from each other as space expand
    2. A and B can move coser to each other as space contract
    How do we perceive this kinds of movement? Do they still obey relativity - both SR and GR? We must consider the fact that at some point SR and GR must relate to energy either expended or consumed to obtain a specifc relativistic observation of the universe. In here, no energy is expended or consumed by either A or B to bring them together or remove them further apart. How can we relate A and B to the 'dynamic' space instead of each other?
    Last edited: Nov 5, 2008
  2. jcsd
  3. Nov 5, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The wavelength of light that's emitted by one of the objects gets stretched out by the expansion of space too, so when it reaches the other object, it has been redshifted.

    Note that the redshift and all other signs of expansion would be unobservable if we and our measuring devices had been expanding too. They aren't, at least not enough for it to be a concern. Their expansion is many orders of magnitude slower than the expansion of the universe. The same thing is actually true for solar systems, galaxies, and maybe small clusters of galaxies. It's only on really large scales that the expansion obeys Hubble's law.

    They do, but you have to keep in mind that there's nothing in either theory that e.g. prevents the time derivative of the distance between them be >c. What the local Lorentz invariance says about the speed of light is that the relative speed of two objects right next to each other can't be >c.

    I don't understand the question.
  4. Nov 5, 2008 #3
    You can't...the mechanism of expanding space is not understood. Right now dark energy is a presumed source of energy powering the cosmological constant but where that comes from is unknown...We only have a grasp of protons/neutrons etc that make up things like A and B in your example....the rest of the stuff is largely a mystery: Wiki sez:


  5. Nov 5, 2008 #4
    It is interesting that there hasn't been much physics on the dynamics of space itself. It is obviously something and yet we treat it as nothing, just vacuum. It can expand, it can contract and it can propagate waves.

    Anyways I think it doesn't follow GR or SR, and one of the reasons why we can see the early universe (such as the early stars following the big bang) is because space expanded faster than the light coming from those early stars to our part in the universe today. So in fact space itself expanded faster than c whilst each particle on its own kept their velocities < c.

    Now this is mostly speculation that ive picked up here and there and i wouldnt be surprised if it were pure garbage. I believe this was his main question, if anyone else has some knowledge on what we've talked about please divulge. However if it were true it does give hope for faster than light travel in space for our future generations.
  6. Nov 5, 2008 #5

    No ...it is real, it is something, it is central to relativity. Space is real enough to curve mass, energy, pressure. It can be visualized as Penrose spin networks, nodes equate to interger areas, links to integer areas. Or as strings and membranes.

    Not one of those phrases matches theory...but it's only theory.
    Space cannot expand faster than the speed of light. Inflation, if that's what you were addressing, occured before space as we know it existed..At the time 11 dimensional spacetime was likely reconfiguring to the four we observe today. There are many inflation theories, Guth's being extremely well known.

    Sorry but also incorrect, you have it reversed: with distant galaxies already receding at superluminal velocities how do you propose to catch them....we have already lost the race and we did not even start.!!!
  7. Nov 5, 2008 #6
    Then how is it possible that we can see the early universe when the time it would have taken the early universe to expand to our position in space now, coalesce into the sun and earth and develop life to observe the sky when in that time the light travelling from those parts wouldve long passed us now.
  8. Nov 6, 2008 #7


    User Avatar
    Gold Member

    In GR cosmology the best model of this is the Friedmann-LeMaitre-Robertson-Walker (FLRW) theory. In this, the universe is describe by a space-time metric in which the spatial part has a scale factor that depends on time. If we assume that the unverse has energgy which we can express as an energy density, it is possible to relate the expansion factor to the energy density ( Friedmann equations). It's done quite well at Wiki.

  9. Nov 6, 2008 #8


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The universe didn't "expand to our position in space". It was space that expanded (and it's still expanding). The distance between any two points in space has been increasing for 13.7 billion years. A lot of light from the early times passed us a long time ago, and a lot of light from the early times hasn't reached us yet.
  10. Nov 6, 2008 #9
    you are basing your questions on assumptions not consistent with well known theory. That's not a criticism, we all start that way....but getting snippets here and there on a forum like this is an inefficient way to learn fundamentals...You'd be far better off to read some books on cosmology (for issues pertaining to the universe) to get a foundation...

    Two good, non mathematical and popular books to try are Michio Kaku's PARALLEL WORLDS and THE STATE OF THE UNIVERSE BY Pedro Ferreira. Used ones are cheap at Amazon or other sources of your choice...

    When the inflationary expansion ended in the first few millionths/billionths of a second...or whatever time period it was....the universe was already billions of times larger than we can ever have observed...akin to looking at a grain of sand and trying to see our entire solar system today..."expansion" was not IN space but before space/time...in fact, I guess the universe was already "infinite" at that point if that's the model used...
  11. Nov 6, 2008 #10
    If we are to move in the same direction as the space is expanding, and at the same rate as the expansion of space,then we would be moving at a speed where all observations would appear constant. We would be moving at the speed of light, would we?
    You are implying that light is not a universal constant, then, are you?

    Relativity is true only when objects are moving. Movement requires energy. How can we speak of such movements as is here in terms of relativity when neither of them are consuming or expending energy? Their movement is based on a different inertial system - that of space and hence, the universe. I hope I make myself clear.
  12. Nov 6, 2008 #11


    User Avatar

    Staff: Mentor

    You're speaking gibberish here. Space expands in all directions, we can't move at the speed of light, light is a universal constant, and Relativity most certainly works when objects are stationary.

    This is not a place for mental vomit. Thread locked.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook