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Author Topic: Distant galaxies are moving away, but at what speed?  (Read 3067 times)

Offline RealEarthling

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I hear a lot about the expanding universe and recent reports tell us that some galaxies are moving away even faster than before (meaning acceleration).  But I never hear anything about actual speed or, for that matter, Velocity (V).  I suppose there would be many different values for different galaxies, but I just wonder about order of magnitude (.2c, .5c, .7c??? - c! ?)   Larry


 

Offline PhysBang

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Distant galaxies are moving away, but at what speed?
« Reply #1 on: 19/04/2010 23:51:11 »
A really good review of the expansion is here: http://lanl.arxiv.org/abs/astro-ph/0310808

"Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the universe" Tamara M. Davis & Charles H. Lineweaver

That might provide more info than you want, though.

In general, the recession, v, of a distant galaxy from our position is  v = cz, where c is the speed of light and z is the measurement of the redshift of the galaxy. This approximation holds for redshifts of appreciably less than 0.5. At about redshift 1.5, a galaxy is, at present, moving away from us at the speed of light and more distant galaxies are moving away from us faster.

 

The Naked Scientists Forum

Distant galaxies are moving away, but at what speed?
« Reply #1 on: 19/04/2010 23:51:11 »

 

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