Einstein's Relativity: Examining Simultaneity Theory

[solarflare]

just to clarify - i am not anti relativity - i just want the truth to be taught and the truth is that C is not constant - it may be constant within a set reference frame - or set of reference frames in a certain scenario but it is not constant with regards to how light propagates through the universe.

 

[solarflare]

Section 23 - Behaviour of Clocks and Measuring-Rods on a Rotating Body of Reference

Hitherto I have purposely refrained from speaking about the physical interpretation of space- and time-data in the case of the general theory of relativity. As a consequence, I am guilty of a certain slovenliness of treatment, which, as we know from the special theory of relativity, is far from being unimportant and pardonable. It is now high time that we remedy this defect; but I would mention at the outset, that this matter lays no small claims on the patience and on the power of abstraction of the reader.

here he admits that he has not stuck to his own rules of general relativity.

 

[Doc Al]

just to clarify - i am not anti relativity - i just want the truth to be taught and the truth is that C is not constant - it may be constant within a set reference frame - or set of reference frames in a certain scenario but it is not constant with regards to how light propagates through the universe.

You need to learn a bit about relativity before having an opinion about it. You are confusing the invariant speed c ≈ 3 x 10⁸ m/s (which happens to be the speed of light in a vacuum) with the phase velocity of light through some medium.

 

[solarflare]

when we see him tell us that certain things he said in the past were not accurate - should we not listen?

 

[Doc Al]

when we see him tell us that certain things he said in the past were not accurate - should we not listen?

Do you realize how overwhelmingly that relativity has been supported by experimental evidence? (Despite Einstein's charming modesty.)

 

[Nugatory]

just to clarify - i am not anti relativity - i just want the truth to be taught and the truth is that C is not constant - it may be constant within a set reference frame - or set of reference frames in a certain scenario but it is not constant with regards to how light propagates through the universe.

The speed of light IN A VACUUM is constant in all local reference frames, regardless of relative velocities.

No one has seriously claimed, hinted, suggested, or said that the speed of light IN A NON-VACUUM MEDIUM is constant, and relativity doesn't claim that it will be. So what's the truth that's not being taught?

 

[solarflare]

Section 27 - The Space-Time Continuum of the General Theory of Relativity is not a Euclidean Continuum

In the first part of this book we were able to make use of space-time co-ordinates which allowed of a simple and direct physical interpretation, and which, according to Section 26, can be regarded as four-dimensional Cartesian co-ordinates. This was possible on the basis of the law of the constancy of the velocity of light. But according to Section 21 the general theory of relativity cannot retain this law. On the contrary, we arrived at the result that according to this latter theory the velocity of light must always depend on the co-ordinates when a gravitational field is present. In connection with a specific illustration in Section 23, we found that the presence of a gravitational field invalidates the definition of the coordinates and the time, which led us to our objective in the special theory of relativity.

 

[solarflare]

the speed of light changes due to gravitational forces

 

[solarflare]

form wikipedia

Some aspects of the data are statistically unusual for the Standard Model of Cosmology. For example, the greatest angular-scale measurements, the quadrupole moment, is somewhat smaller than the Model would predict, but this discrepancy is not highly significant. A large cold spot and other features of the data are more statistically significant, and research continues into these. ( WMAP )

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"This was the method I adopted: I first assumed some principle, which I judged to be the strongest, and then I affirmed as true whatever seemed to agree with this, whether relating to the cause or to anything else; and that which disagreed I regarded as untrue." ( plato )

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note the deflection away from parts of the information that do not fit the theory as being "not highly significant" or as plato would have said "untrue".

 

[solarflare]

cherry picked data that fits with a theory will of course make that theory seem correct

 

[harrylin]

the problem is that einstein came up with a theory where he said C is constant.

then later on he realized that it was not and stated so in other papers. i believe it was from 1911 onwards but do not have the info to hand.

but when everyone reads his works they take everything he said as true - even after he said himself he was wrong.

That's not a problem but scientific progress; science is not dogmatic like religion.

However, nothing of these things have to do with the topic. So, start your own thread. Continuing here is against the rules (so I won't reply here anymore, and to others also: don't feed the trolls!):

"Do not hijack an existing thread with off-topic comments or questions--start a new thread."

 

[ghwellsjr]

That's not Einstein's second postulate. He didn't say that the speed of light is measured to be equal to c, he said the propagation of light is defined to be c. So when you have two clocks and you measure how long it takes a flash of light to go from the one to the other, and you divide the distance between them by the measured time difference between the two clocks and you calculate the speed of light to be something other than c, you tweak one of your clocks and repeat until the calculation comes out to be c. You're not measuring the propagation of light, you're defining it.

This is what I read in the 1905 paper.
Par.1, he is defining time for the purpose of simultaneity by clock synchronization using light signals. He refers to experience as a reason for the speed of light in space as a universal constant. In par.2, he defines the reflected signal as composed of equal path lengths out and return, avoiding the current impossibility of timing light for a unidirectional path, which would require separated clocks, which leads back to par.1.
The clock synch procedure only makes it appear that the out and back signal paths are equal, producing a relative synchronization. At the end of par.2, using a second observer B moving at a different speed, he shows on the basis of absolute speeds (c±v),that B does not consider the first clocks as synchronized. What the observer does measure is the round trip time, and due to length contaction and time dilation, his distance and time are scaled by the same factor 1/gamma, thus light speed is constant.

This is in complete agreement with what I said. When Einstein refers to experience, he is talking about measuring only the round-trip speed of light as you can see by his equation for determining the value of c which he affirms is a universal constant. But he never says that we can measure the one-way speed of light, we can only define it. And that is what is second postulate does.

Keep in mind that when Einstein wrote his paper, no one believed that the propagation (one-way) speed of light was c for every inertial observer even though they all agreed that the measured round-trip value of the speed of light was the universal constant c. They believed that light propagated at c only in the absolute ether rest state. Einstein is stating something revolutionary when he postulates that light also propagates at c even for an inertial observer moving with respect to the presumed ether. Lorentz, et al, claimed that it was the contraction of the ruler and the dilation of time on the clock for the moving inertial observer that resulted in his measurement of the round-trip speed of light coming out the same as it would if he were stationary in the ether where there would be no length contraction or time dilation. It never occurred to them that even for a moving observer, they could define length to be what his ruler measures and they could define time to be what his clock measures and they could define the one-way speed of light to be equal to his measured two-way speed of light and come out with "a simple and consistent theory", as Einstein put it in his introduction.

 

[harrylin]

[..] he never says that we can measure the one-way speed of light, we can only define it. And that is what is second postulate does.

It does more than that, as explained in posts #23, 26. We discussed that earlier here:
https://www.physicsforums.com/showthread.php?t=517105

Keep in mind that when Einstein wrote his paper, no one believed that the propagation (one-way) speed of light was c for every inertial observer [..]

Astronomers already used the postulate that light has a constant velocity, and in particular that its velocity is the same in all directions. And the issues with that were already explained here: http://en.wikisource.org/wiki/The_Measure_of_Time

and we also had a similar discussion here:
https://www.physicsforums.com/showthread.php?t=518005