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#61 madmac

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Posted 22 February 2017 - 08:13 AM

Tim88 post#50.

Thanx for the link to Tom Roberts' & Siegmar Schleif's website re What Is The Experimental Basis of Special Relativity.

I refer to their wording in their Section 3 re Einstein's second postulate......... Any speed of light moves in the "stationary" system of coordinates with determined velocity c, whether the ray be emitted by a stationary or by a moving body.

 

I like this wording (compared to other wordings that i have seen). It is of course itself made up of two postulates, hencely we should talk of three postulates not two, the third being that the velocity of the emitter does not affect the determined velocity c.

 

But i want to mention the second postulate -- which now becomes simply.......

Any speed of light moves in the "stationary" system of coordinates with determined velocity c.

 

Here it is clear to me that Einstein doesn't say that light moves with velocity c -- he says that light moves with determined velocity c.

That makes sense to me.

SR & GR are models, & in these models u have rules for determining the velocity of c (& other things). Then u continue to follow the rules & u determine other numbers. And u relate these numbers to numbers determined by others using the same model. And everyone lives happily ever after.

Re the real velocity of c -- who cares?? It is unlikely to worry anyone unless they have a very accurate clock.


Edited by madmac, 22 February 2017 - 08:24 AM.

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#62 Strange

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Posted 22 February 2017 - 08:22 AM

Here it is clear to me that Einstein doesn't say that light moves with velocity c -- he says that light moves with determined velocity c.

 

 

1. You mean "what Roberts and Schleif say"

 

2. What is the difference between "velocity" and "determined velocity"? Do you think light can move at a different speed than we measure?


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#63 madmac

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Posted 22 February 2017 - 10:44 AM

Strange.

Wiki says ....... "As measured in any inertial frame of reference..." etc.......... which is similar.

 

Yes, the velocity c must depend on the method of measuring (determining). If one uses a special method of measuring based on a special model then that might be ok for some applications.

But if it doesn't give true c then eventually a problem will arise, in which case science will investigate & discover new knowledge (benefiting mankind) , or, science will fudge & the fudge will be rewarded with a Nobel (benefiting one man).


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#64 Tim88

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Posted 22 February 2017 - 01:01 PM

Tim88 post#50.

Thanx for the link to Tom Roberts' & Siegmar Schleif's website re What Is The Experimental Basis of Special Relativity.

I refer to their wording in their Section 3 re Einstein's second postulate......... Any speed of light moves in the "stationary" system of coordinates with determined velocity c, whether the ray be emitted by a stationary or by a moving body.

 

I like this wording (compared to other wordings that i have seen). It is of course itself made up of two postulates, hencely we should talk of three postulates not two, the third being that the velocity of the emitter does not affect the determined velocity c.

 

But i want to mention the second postulate -- which now becomes simply.......

Any speed of light moves in the "stationary" system of coordinates with determined velocity c.

 

Here it is clear to me that Einstein doesn't say that light moves with velocity c -- he says that light moves with determined velocity c.

That makes sense to me.

SR & GR are models, & in these models u have rules for determining the velocity of c (& other things). Then u continue to follow the rules & u determine other numbers. And u relate these numbers to numbers determined by others using the same model. And everyone lives happily ever after.

Re the real velocity of c -- who cares?? It is unlikely to worry anyone unless they have a very accurate clock.

 

First of all, their translation may make you read something in there that wasn't intended. The German word "bestimmten" merely means "certain" or "definite", as also so translated here: http://fourmilab.ch/etexts/einstein/specrel/www/  (in the intro)

Further, as you can also see in the intro of Einstein's paper, that whole phrase is the second postulate; it simply characterizes light as a wave. A wave has a certain or constant speed c, as it is independent of the speed of the source.

 

Nevertheless you are right that the "speed of light" as defined in SR, following Einstein's lead, is a "determined" speed based on a measurement convention - as specified in §1. And according to the theory, even accurate clocks cannot help to change that.


Edited by Tim88, 22 February 2017 - 01:03 PM.

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#65 Strange

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Posted 22 February 2017 - 01:50 PM

But if it doesn't give true c 

 

 

Why wouldn't it?


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#66 madmac

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Posted 22 February 2017 - 09:33 PM

Strange.

Einstein doesn't need a true c. And, he has an infinite number of possible c's, or at least only limited by the number of observers. And Einsteinians obviously get goodish answers lots of the time.

If there is a true c (ie only one truly stationary frame) then SR & GR cannot be correct (as he knew), or not 100% correct, or only correct in certain instances (whatever).

We hear of lots of things that prove Einstein correct, forgetting that there is no limit to the number of theories that can accord with any experimental result.

 

Tim88.

Yes, i see that in the intro they don't use the word determined nor the word measured. Although i notice that in Section 2 the wording of the postulate (called principle at this stage) is similar or identical to the wording i mentioned earlier, ie using the word determined.

 

I see that the intro also says -- "The introduction of a "luminiferous ether" will prove to be superfluous....... " -- which accords with the statement i often make that Einstein didn't rule out an aether, he merely made it redundant. Which sort of resonates with my above comments to Strange.

 

Tim88.

U say..... A wave has a certain or constant speed c ......

This reminds me that i need to start a new thread in Speculations. Your statement depends on the definition of a wave.

I already knew of the problem (that i thought of, i didn't read it anywhere), but it surfaced again (i say again because i first saw it when i read Hicks' calibration of M&M)(1905) when i read an article using one of your links (or someone else's here), where it said that Einstein took Newton's 0.87 arcsec to 1.75 arcsec mainly by using the bending of light (as it passed the Sun) by virtue of redshift. But i wont go into it now. I am just flagging that your seemingly simple wave statement (& Einstein's redshift methodology) might not be so simple. And this has nothing to do with aether.


Edited by madmac, 22 February 2017 - 10:14 PM.

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#67 Strange

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Posted 22 February 2017 - 09:57 PM

And, he has an infinite number of possible c's, or at least only limited by the number of observers. 

 

 

No. There is only one. That is the whole point.

 

 

 

Einsteinians 

 

There is no such thing. Just because your worldview is dictated by your religious beliefs, doesn't mean that others are similarly gullible.

 

 

 

get goodish answers lots of the time.

 

In other words, the theory works.

 

 

 

If there is a true c (ie only one truly stationary frame)

 

There is no truly stationary frame. That is a complete non sequitur.

 

 

 

We hear of lots of things that prove Einstein correct

 

I don't think Einstein performed any experiments to test SR or GR.

 

And nothing is ever proved correct in science.

 

 

 

there is no limit to the number of theories that can accord with any experimental result.

 

Nonsense.

 

 

 

Einstein didn't rule out an aether, he merely made it redundant.

 

At which point Occam's Razor comes into play. Bye bye aether.


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