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Space expansion in our perspective? 
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#37
Jun1110, 02:19 PM

P: 25

Is there physical evidence that space is expanding or is it just a result of the math? 


#38
Jun1210, 05:05 PM

Sci Advisor
P: 1,910

For example, in special relativity you may have heard that it's tricky to add velocities that different observervers heve measured. In cosmological coordinates, you add them without correction nonetheless. That's easy and appropriate, but the result definitely has nothing to do with "velocity" in the SR sense. Especially, v<c does not apply. That's just the effect of an unusual coordinate system. Then, in GR, matter determines geometry. You don't even have that static background on which to base your misunderstandings. Is distance changing, or is the light we took to measure distance delayed by some matter that intervened? There's not way to decide such questions. 


#39
Jun1310, 12:44 AM

P: 25

Thank you Ich.
My curiosity is temporarily satisfied. :) 


#40
Jun1310, 04:49 AM

Sci Advisor
PF Gold
P: 9,478

Expansion is a pathetically weak 'force' compared to the other forces of nature  gravity, nuclear and electroweak. It is overwhelmed by these forces until until things become so vastly distant their effects become negligible.



#41
Jun1310, 01:28 PM

P: 302

Nobody knows the correct answer to this question....



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