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   XPost: sci.physics.relativity, alt.astronomy   
   From: ggherold@gmail.com   
      
   On Apr 16, 12:45 am, RichD  wrote:   
   > How do astronomers know our galaxy is rotating, how do   
   > they measure the velocity?   
   >   
   > And, how do they measure the rotational velocity of other galaxies?   
   >   
   > --   
   > Rich   
      
   Well this is mostly speculation... but you can google as well as I   
   can.   
      
   First if our galaxy wasn't rotating then all the stars would fall to   
   the center.   
   Second I think we can see the galactic motion as part of the   
   correction in the CMB.. the proper motion of the earth.   
      
   For the other galazies I assume they look at doppler shifts of   
   spectral lines for stars near the rim... with an edge on galaxy.   
      
   George H.   
      
   --- SoupGate-Win32 v1.05   
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