Merged Relativity+ / Farsight

[Reality Check]

As I said I've provided the evidence in the NIST optical clocks and the Shapiro delay etc.

That is a lie, Farsight: The " NIST optical clocks and the Shapiro delay etc" are evidence for General Relativity with its curved spacetime as described in Einstein's 1915 paper and every textbook in almost a century.
They are not evidence for any fantasy that space is inhomogeneous or the delusion that this fantasy can match the above observations with no calculations.

This is from section 22 of the 1916 book Relativity: The Special and General Theory and does not mention your fantasy, Farsight - no mention of inhomogeneous space !
The book contains 2 instances of "homogenous" and no instances of "inhomogeneous".
This is standard GR - the speed of light is not constant in an non-inertial frame of reference.

Quoting this book with no mention of inhomogeneous space shows that this is your theory, Farsight.

Being unable to answer simple questions about your terms with references to the relevant scientific literature shows that this is your theory, Farsight:
Farsight: (4 August 2014): What is the scientific definition of "inhomogeneous space" in physics?

Farsight: (4 August 2014): What does this "inhomogeneous space" have to do with galaxy halos (specifically the Milky Way halo which is a collection of stars and globular clusters)?

 

[Kwalish Kid]

...The 1920 English translation uses the word velocity, but...

Again, you only use textual analysis of a limited set of texts. This is not evidence given the criteria you laid out, "Evidence consists of experimental results and observations". Until you can show us a theory that makes predictions of light slowing with position for some other reason than spacetime curvature, you have nothing for which we can get evidence.

Every time you resort to an attempt at textual analysis in order to dodge a question of evidence is another mark against your reputation.

 

[tusenfem]

actually, "geschwindigkeit" can mean both "speed" and "velocity" and in physics it is often the latter meaning

 

[Farsight]

actually, "geschwindigkeit" can mean both "speed" and "velocity" and in physics it is often the latter meaning

Only when Einstein used it, he was talking about the limitations of the SR postulate. He was talking about speed. Here's some English translations. Unfortunately the word velocity used instead of speed:

1911: "If we call the velocity of light at the origin of coordinates c₀, then the velocity of light c at a place with the gravitation potential Φ will be given by the relation c = c₀(1 + Φ/c²)”.

1912: "On the other hand I am of the view that the principle of the constancy of the velocity of light can be maintained only insofar as one restricts oneself to spatio-temporal regions of constant gravitational potential".

1913: "I arrived at the result that the velocity of light is not to be regarded as independent of the gravitational potential. Thus the principle of the constancy of the velocity of light is incompatible with the equivalence hypothesis".

1915: "the writer of these lines is of the opinion that the theory of relativity is still in need of generalization, in the sense that the principle of the constancy of the velocity of light is to be abandoned".

1916: “In the second place our result shows that, according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity and to which we have already frequently referred, cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position”.

There's a myth that he tried out a varying speed of light in 1911 then abandoned it. But he didn't abandon it.

 

[Kwalish Kid]

Only when Einstein used it, he was talking about the limitations of the SR postulate. He was talking about speed.

That statement is an interesting, since the speed of light in the special theory of relativity is determined relative to a system of coordinates in which Newtonian mechanics held as a first approximation. In the general theory of relativity, any system of coordinates can be used, so many general claims cannot be upheld.

Einstein did careful work to establish what did and did not hold in acceptable systems of coordinates. He was very careful to establish that the speed of light was the same at any point of spacetime. This is very important and required for the mathematics of his theory to be correct.

There's a myth that he tried out a varying speed of light in 1911 then abandoned it. But he didn't abandon it.

There is no myth. It seems that the only person saying that there is a myth is Farsight. Those who study the theory note that there is a definition of the speed of light that applies to infinitesimal distances and there is a coordinate speed that varies and that we can use meaningfully in physics because the constant speed of light at every point allows us to reliably do physics in any system of coordinates thanks to a set of translations that we can use from one coordinate system to another.

 

[Farsight]

All: beware of insincere posters. See for example post #1966 where I advised Kwalish Kid of the Baez website which backs me up:

"Einstein talked about the speed of light changing in his new theory. In his 1920 book "Relativity: the special and general theory" he wrote: "... according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity [...] cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity [Einstein means speed here] of propagation of light varies with position." This difference in speeds is precisely that referred to above by ceiling and floor observers..."

He's also fully aware that Professor Ned Wright's deflection and delay of light backs me up too:

"In a very real sense, the delay experienced by light passing a massive object is responsible for the deflection of the light..."

 

[Reality Check]

All: beware of ...

All: beware of obsessive behavior from posters where they keep on linking to a web site that is clearly understandable as if every other poster in the forum could not understand it!

Farsight's statement that the speed of light varies in GR is basic GR. The speed of light is only constant in inertial reference frames. GR is primarily about non-inertial reference frames.
Propagation of light in non-inertial reference frames

The description of motion in relativity requires more than one concept of speed. Coordinate speed is the coordinate distance measured by the observer divided by the coordinate time of the observer. Proper speed is the local proper distance divided by the local proper time. For example, at the event horizon of a black hole the coordinate speed of light is zero, while the proper speed is c.[1] The coordinate speed of light (both instantaneous and average) is slowed in the presence of gravitational fields. The local instantaneous proper speed of light is always c.
In an inertial frame an observer cannot detect their motion via light signals as the speed of light in a vacuum is constant. This means an observer can detect when their motion is accelerated by studying light signals.

N.B. the last sentence does not mean that an observer can always tell if they are in a gravitational field. Locally a gravitational field looks the same as a constant acceleration. So if an observer is in a small room they cannot tell the difference between that room being on a planet and that room being an elevator.

What Kwalish Kid stated in Those who study the theory note that there is a definition of the speed of light that applies to infinitesimal distances and there is a coordinate speed that varies and that we can use meaningfully in physics because the constant speed of light at every point allows us to reliably do physics in any system of coordinates thanks to a set of translations that we can use from one coordinate system to another. is a bit confusing but true.

 

[Reality Check]

There's a myth that he tried out a varying speed of light in 1911 then abandoned it. But he didn't abandon it.

Dear me, Farsight, now you are citing myths !
Then making up a fantasy about the myth which is extremely ridiculous.

You seem ignorant of the fact that Einstein's publications were ... published!
For 1911 we have the following on SR and the development of GR:
On the Influence of Gravitation on the Propagation of Light (PDF)
The Theory of Relativity (Naturforschende Gesellschaft, Zürich, Vierteljahresschrift, 56, 1–14)
On the Ehrenfest Paradox (Physikalische Zeitschrift, 12, 509–510)

The varying coordinate speed of light in GR has never been "abandoned". It has existed in General Relativity for 99 years now .

 

[Reality Check]

Here's some English translations. Unfortunately the word velocity used instead of speed:

What has a translation error of old papers have to do with the science as we understand it today, Farsight?

However light does have a velocity!
So On the Influence of Gravitation on the Propagation of Light

If we call the velocity of light at the origin of co-ordinates c₀, then the velocity of light c at a place with the gravitation potential Φ will be given by the relation ...

is correct as stated. It is the non-standard usage of "c" as denoting a velocity that may be an issue.

Replacing "velocity of light" with "speed of light" makes the text look better from the modern perspective. No one at the time had a problem with "velocity of light". Only a few crackpots concentrating on semantics have had a problem with "velocity of light" since then. They really go crazy when they realize that Einstein used "V" for the speed of light until 1907 !

 

[Kwalish Kid]

All: beware of insincere posters. See for example post #1966 where I advised Kwalish Kid of the Baez website which backs me up:

"Einstein talked about the speed of light changing in his new theory. In his 1920 book "Relativity: the special and general theory" he wrote: "... according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity [...] cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity [Einstein means speed here] of propagation of light varies with position." This difference in speeds is precisely that referred to above by ceiling and floor observers..."

He's also fully aware that Professor Ned Wright's deflection and delay of light backs me up too:

"In a very real sense, the delay experienced by light passing a massive object is responsible for the deflection of the light..."

Again, you turn to textual analysis (a clearly dishonest textual analysis). You refuse to address the physics that Einstein wrote and the physics that Baez and Wright use in their papers. Even though you have admitted that you cannot produce a single example of a place that Einstein used the variable speed of light as a cause of a physical phenomena.

You ignore the key insights of the general theory of relativity that allow one to write descriptions of physical systems using any coordinate system. Please show us how to describe a physical system using your variable speed of light, inhomogeneous space, and motion instead of time theory.

 

[Reality Check]

Please show us how to describe a physical system using your variable speed of light, inhomogeneous space, and motion instead of time theory.

Which reminds me - what use is a theory if the author cannot even define key terms in it?
Farsight: (4 August 2014): What is the scientific definition of "inhomogeneous space" in physics?

What use is a theory if the author makes up unsupported claims about these undefined terms:
Farsight: (4 August 2014): What does this "inhomogeneous space" have to do with galaxy halos (specifically the Milky Way halo which is a collection of stars and globular clusters)?

This is the equivalent of claiming that space is wobbly and because there is wobbly space anything Farsight wants to be explained is explained by wobbly space !

Even standard terms in physics cannot be explained or understood by Farsight:
Farsight: (29 July 2014) What is the scientific definition of space?

Farsight: (29 July 2014) What is the scientific definition of a field in physics? And the follow-on: How does this make What a field in physics really is by W.D.Clinger wrong?

 

[ctamblyn]

You'll be waiting a long time for that reply, RC. John Duffield, aka Farsight, has been banned for breaching the terms of his probation.

 

[ben m]

End of an era!

 

[ctamblyn]

End of an era!

And of an error.

 

[Guybrush Threepwood]

Oh Bollocks, I suppose he was wearing a bit thin, and it was inevitable, but I thought the mods had lost all their powers recently so I'd hoped he'd last a while longer.

Wheel on the next nutcase.

 

[Daylightstar]

And of an error.

Very well put.

 

[Darwin123]

What has a translation error of old papers have to do with the science as we understand it today, Farsight?

However light does have a velocity!
So On the Influence of Gravitation on the Propagation of Light

is correct as stated. It is the non-standard usage of "c" as denoting a velocity that may be an issue.

Replacing "velocity of light" with "speed of light" makes the text look better from the modern perspective. No one at the time had a problem with "velocity of light". Only a few crackpots concentrating on semantics have had a problem with "velocity of light" since then. They really go crazy when they realize that Einstein used "V" for the speed of light until 1907 !

You are wrong. Einstein used "V" for the speed of light back in 1905. He never uses 'v' to designate 'c'.

I have in front of me an English translation of the article:
'On the Electrodynamics of Moving Bodies' by Albert Einstein,
The German version of it written in 1905. My translation has equations
which I assume were unchanged in the English translation. Just in case
someone wants to challenge me who has the German version, the original
article was
'Zur Elektrodynamik bewegter Körper,' written in 'Annalen de Physik 17 (1905).


Einstein, in this article, designates 'c' for the speed of light in a vacuum. The Maxwell equations that he writes are for a vacuum only, so it makes no sense to discuss the speed of light in glass. He designates 'v' and 'w' for speeds less than the speed of light. He sometimes capitalizes 'V'
when he adds velocities. In section 5, which is page 50 in my edition, he writes the formula for addition of velocities which is:
V = (v+w)/(1+vw/c^2)


I can only address the way he uses English in this translation. However, scientific translators rarely change the variable names in the translation. So if "V" is used to designate a speed less than light in this translation, there is a high probability he used it the same way in the original English article.


I can only address the issue of English words as used by physicists today. I think what Einstein meant was very clear to most physicists in 1905 in the context of the article. However, the physics jargon of the time has since evolved so one can express it clearer.

English speaking physicists usually reserve the word 'velocity' to designate a vector. In conversation they will interchange speed and velocity when the context makes it clear what they are talking about. They use the word 'speed' to designate the magnitude of a 'velocity' vector. In the most rigorous, formal usage of the word 'speed', speed can not be negative. A canonical speed is greater than or equal to 0.

Clearly, 'c' can not be a vector. So calling 'c' the 'velocity of light in a vacuum' is formally wrong. Also, GR shows that the speed of light can vary over large distances in a nonzero gravitational gradient. So in GR, it is only the local speed of light that is invariant.

The variables 'u' and 'v' represent a projection (i.e., a component) of a velocity vector on a designated axis. In the article, the projection is on the 'x-axis'. The quantities 'u' and 'v' can be negative. Therefore, I think that it would be inappropriate to call them speeds. It is probably just as valid to call them velocities. There is a direction simplicity in the values of 'u' and 'v', so they are not really raw 'speeds'. So I propose that Einstein was using the word velocity correctly when he designated 'u' and 'v'.

However, 'c' can not be a vector. So it usually shouldn't be called a velocity. In the context of most equations in the article, 'c' is a speed. It is used this way on page 51, where 'c' designates a vector with the magnitude 'c'.
V = (c+w)/(1+cw/c^2)
so,
V=c

Here, c is any velocity with a magnitude equal to the speed of light in a vacuum. However, c is a vector in this formula! So it is a velocity! The word 'velocity of light' is valid in the context of this expression.

I think this is obvious to educated physicists, who know what a vector is. However, a lot of people criticizing Einstein obviously don't know what a vector is.

There is a simple way to avoid this ambiguity in modern physics classes. I propose the following.

I believe to be 100% consistent with absolutely no ambiguity, 'c' should be designated 'the local speed of light in a vacuum'. The word local excuses the effect of a large gravitational gradient. If you look on a small enough length scale, gravitational gradients are insignificant even in GR!


So the most important postulate in relativity should be stated as follows.

The local speed of light in a vacuum does not vary with reference frame of the observer doing the measurement.

This statement is correct both in GR because it includes the word 'local'. However, it is also valid in SR. So I think that if the postulate is expressed this way, some misunderstandings can be avoided.

 

[Reality Check]

You are wrong. Einstein used "V" for the speed of light back in 1905. He never uses 'v' to designate 'c'. ....

The V in

Only a few crackpots concentrating on semantics have had a problem with "velocity of light" since then. They really go crazy when they realize that Einstein used "V" for the speed of light until 1907 !

is a upper case V not a lower case v.

 

[Darwin123]

The V in

is a upper case V not a lower case v.

Uhh, sorry. That was a misprint. 'I meant to say that: 'V' is
never explicitly used as the speed of light in a vacuum. Einstein only uses c to
designate the local speed of light in a vacuum. The 'speeds'
u and v designate components of the velocity vector projected on
a coordinate axis.

'V' is used as the relativistic sum of two velocities. There is an upper limit to the magnitude of 'V', however, If one of the two velocities has a magnitude equal to the speed of light 'c', then 'V' will have a magnitude equal to the speed of light 'c'.

Einstein in his 1905 paper show how |V| approaches c when |v| approaches c. |V| is always less than or equal to c.

The velocity components u, w and V are never used by Einstein to designate the local speed of light, c. However, all three have an upper limit of 'c'.

 

[Reality Check]

Uhh, sorry. That was a misprint. ...

Speed of light:

Einstein used V in his original German-language papers on special relativity in 1905, but in 1907 he switched to c, which by then had become the standard symbol.[6][7]

The German version:
Zur Elektrodynamik bewegter Körper has V as the symbol for the speed of light.

Wir setzen noch der Erfahrung gemäß fest, daß die Größe
... = V
eine universelle Konstante (die Lichtgeschwindigkeit im leeren Raume) sei.

However the 1923 English translation On the Electrodynamics of Moving Bodies has

In agreement with experience we further assume the quantity
... = c
to be a universal constant—the velocity of light in empty space.

So it looks like the translation was from German and an outdated symbol to English and a modern symbol.