XPost: sci.physics, sci.math   
   From: PointedEars@web.de   
      
   squalk wrote:   
   > The Starmaker wrote:   
   >> Thomas 'PointedEars' Lahn wrote:   
   >>> Ruben Safir wrote:   
   >>>> One of the concepts that have bothered me the most is the idea that the   
   >>>> universe is ever exapanding.   
   >>>   
   >>> [_expanding_]   
   >>>   
   >>> We do not know that.  We know that our universe is expanding now and has   
   >>   
   >> "We"???? you mean me, myself and I?   
      
   Astrophysicist/cosmologists.  The scientific community.   
      
   >> I'm flabgastted that people till this day are testing Positive for   
   >> Stupid in these sci newsgroups.   
   >>   
   >> The UNIVERSE IS *NOT* EXPANDING! It *never* has expanded. It remains the   
   >> same size it always has been since it existence.   
      
   Observationally falsified.   
      
   >> The Big Bang was the 'expansion' of ...space, not the expansion of the   
   >> universe.   
      
   The Big Bang _is_ the expansion of the space of our universe.  AFAWCS it is   
   ongoing.   
      
   >> Space is expanding, not the universe.   
      
   Our universe is to good approximation well described by spacetime,   
   particularly the FLRW metric   
      
     ds^2 = -dt^2 + a(t)^2 [1/(1 - k r^2) dr^2 + r^2 (d Omega)^2],   
     (d Omega)^2 = (d theta)^2 + sin^2(theta) (d phi)^2,   
      
   where a(t) is the scale factor at the cosmological time t -- which is   
   currently increasing --, and r, theta and phi are spatial (spherical)   
   coordinates.  So our universe and space are inseparable concepts: When we   
   say "space" in cosmology, we mean the space *of our universe* (at least the   
   observable one).   
      
     [Notice that this is different from colloquial use where "space" often   
      is a shorthand for "outer space", i. e. the space of our universe outside   
      Terra's atmosphere.]   
      
   > Space is space, it dosen't expand.   
      
   Wrong, too.  We can *observe* the expansion and evolution of our universe   
   because we can observe galaxies as they were in the past: The light that   
   they emitted takes time to get to us.  The farther an object is away, the   
   earlier the light was emitted that reaches us now:   
      
      
      
   --   
   PointedEars   
      
   Twitter: @PointedEars2   
   Please do not cc me. / Bitte keine Kopien per E-Mail.   
      
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    * Origin: you cannot sedate... all the things you hate (1:229/2)