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Violation of Universal Speed Limit

  1. Apr 3, 2007 #1
    We all accept that the universe is expanding and that expansion is accelerating. So what exactly are the speeds of those far off galaxies with respect to an earth observer. And if the universe is destined to continue this expansion forever, then wont the speeds of far off galaxies eventually violate Einsteins postulate that 'c' is the universal speed limit.. Hubble's law is linear and thus I would assume in a finite amount of time, mass will exceed the speed of light. How is this being handled with, or am I missing something?
  2. jcsd
  3. Apr 3, 2007 #2


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    lots of stuff we observe is receeding at speeds like 3c and 4c

    this is not forbidden by Special Relativity

    IIRC there was an article in Scientific American about this, maybe March 2005, by Charles Lineweaver and Tamara Davis. It dealt with common misconceptions people have. They also have a separate article called "Expanding Confusion" which tries to dispell popular misconceptions like this.
    Would you like a link? The SciAm article is written very understandably with lots of good diagrams and little or no math!

    If we could get everybody together who thinks recession speeds are limited by c, we could have a tutorial and deal with the problem all at once.
    I am talking mainstream cosmology---there are minority schools of thought where people disagree with the mainstream view, but my advice would be to at least learn the majority consensus picture of cosmology and then if you want explore fringe elements.
    Last edited: Apr 4, 2007
  4. Apr 4, 2007 #3


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    Recession speed tutorial started

    Hybird, I started a thread that can serve as a recession speed discussion/questions/tutorial thread.

    If you have questions about superluminal recession speed, how light can reach us from objects receding at greater than c, and other related matters

    then you are invited here

    there is a neat recession speed calculator, which I urge you to check out and play around with
  5. Apr 5, 2007 #4
    Ghost story

    Do you know animated ghost story?
    The curved spacetime assumption (i.e. GR) is like a ghost. In fact, people do derived its animated story: time travel, wormhole, reversal time travel, dead into living, etc.

    The nature of ghost is that it can not testified. Curved spacetime can not be testified because there is no global reference frame. When you live in a curved spacetime, no coordinate system is direct distance, angle, or time. If we want to find these quantity, we need to use metric form to be integrated along the geodesic line concerned. However, when confronting curved spacetime assumption to real data (e.g., GPB data), relativists never bother to calculate such integration. Instead, they denote some coordinate by the symbol, other by \phi, other by t and naively say those are spatial distance, angle and time respectively. Do you believe that there is a Cartesian coordinate system on curved space which has direct meaning of spatial distance?
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