
#1
Feb810, 02:51 PM

P: 32

why did they have to be the same speed? do you think that this speed was somehow set as a standard speed for such things, i don't know maybe there are other things that are also in the speed of light.. so the speed of light isn't so rare..




#2
Feb910, 01:05 AM

Sci Advisor
PF Gold
P: 9,182

GR sets a universal speed limit on 'communication' between objects in the universe. That limit happens to be the speed of light.




#3
Feb910, 12:07 PM

P: 173

If graviton is never confirmed to be real, then your question  why gravity propagates at speed of light  is very good question. Simply stating that GR forbids FTL communication, doesn't explain anything, because question is why speed of gravity propagation is exactly same as the speed of light propagation, not why gravity is not faster then light. 



#4
Feb910, 03:43 PM

P: 2,045

what is the relation between gravity and light?
I think the "speed of gravity" can be worked out using GR...and it turns out to be c...but I've no idea how. :P




#5
Feb1010, 12:48 AM

Sci Advisor
P: 2,194

http://www.physicsforums.com/showthread.php?t=369420 Edit: Also, on the grounds of dimensional analysis, we expect to get c. The only other really conceivable option would be for gravity to propagate instantaneously. 



#6
Feb1010, 02:11 AM

Sci Advisor
P: 1,883





#7
Feb1010, 02:16 AM

Sci Advisor
PF Gold
P: 9,182

Instantaneous speed of gravity has been thoroughly debunked AFAIK.




#8
Feb1010, 09:58 AM

P: 32

could you please explain what you meant by "GR" and "FTL" ? 



#9
Feb1010, 10:02 AM

Sci Advisor
HW Helper
P: 8,961

FTL = faster than light 


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