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Why does light have invarient speed? 
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#55
Jan708, 05:45 PM

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P: 4,087

Ming,
The postulate is supported by the fact that the laws of physics require it to avoid contradictions. Also, is the Wiki really the best source you have ? I must say I find your arguments incomprehensible but I don't think you understand relativity at all. 


#56
Jan708, 06:11 PM

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What I am talking about is this: 


#57
Jan708, 06:20 PM

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#58
Jan708, 08:06 PM

P: 421

If the theory is based on the first and second postulates, then the speed of light 'c' is guaranteed, but the abstract mathematical manipulations will not reveal the 'how' or 'why'. The purpose of the theory is to produce numbers that agree with measurements/perceptions by the observer. To explain 'why', you have to analyze the behaviour in terms of physical processes. There is an answer to this, just as there is for time dilation.



#59
Jan708, 10:06 PM

P: 65

My original question is about the (physical) mechanism/process, not philosophy/abstractmath. 


#60
Jan708, 10:10 PM

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#61
Jan708, 10:17 PM

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#62
Jan808, 12:57 AM

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#63
Jan808, 10:05 AM

P: 1,521

Note that the case v1 = c cannot however studied in SR because v1 is the speed of the moving ref. frame S' with respect to the stationary ref. frame S (v2 is the speed of the object with respect to S') and we know that no ref. frame with that speed can exist. 


#64
Jan808, 09:45 PM

P: 91

The solution, Einstein explained, lay in a reconception of the idea of time. 


#65
Jan2008, 11:43 AM

P: 91

I'd say the underlying properties of spacetime is a byproduct of the invariance of the speed of light which is a postulate of SR 


#66
Jan2008, 11:53 AM

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#67
Jan2008, 12:47 PM

P: 91

It was Minkowski who pointed out how important the geometry of spacetime was. Einstein himself did not at first seem to think geometrically about spacetime. 


#68
Jan2008, 12:52 PM

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Einstein used the invariant speed of light to deduce how space and time behaved. (It's not just a "trick of light".) That's his huge contribution. True, the full modern view of the geometry of spacetime came later.



#69
Jan2508, 12:05 PM

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#70
Jan2508, 12:18 PM

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I don't think I expressed myself very well before. My point was that relativity itself is more fundamental than just a strange consequence of the behavior of light. (Some folks argue that relativistic effects are just illusions due to the strange nature of light. They are wrong.) 


#71
Jan2508, 04:28 PM

P: 91

This is a result of time dilation. The faster you travel in space, the slower you travel in time. Nevertheless, the length of 4velocity of any inertial observer is always c 


#72
Jan2508, 04:50 PM

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