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Second postulate content

Harald88 -

I am loathe to accuse other editors of vandalism but in this case I am getting very tempted to. Perhaps this is a case of "a little knowledge is dangerous", but in any case I am not amused by your reducing the second posulate to

The speed of light is independent of the motion of the light source.

The aether theories are compatible with this posulate. In fact, it was to explain this observation in terms of classical mechanics that the aether theories were created. Rindler states the second posulate as

The rectilinear speed of light is the same in all directions, in all inertial frames of reference, and at all times.

Note that the source invariance is not noted explicitly here. Instead it is implied in the overall constancy of the speed of light. It is that constancy that forms the operative part of the second posulate, not the source invariance. Please respect that. --EMS | Talk 15:31, 16 May 2006 (UTC)

EMS, please consider the following quotes from a recent article in the American Journal of Physics:

"In the years immediately preceding 1905 and in Einstein's seminal paper, the phrase 'the constancy of the speed of light', meant only that the speed of light is independent of the source's velocity"

and

"Banesh Hoffmann, who worked with Einstein in the 1930s, put the matter neatly in his book, Relativity and Its Roots:

The second of the two principles in Einstein’s paper said that the motion of light is not affected by the motion of the source of light. Nothing, it

would seem, could be more orthodox and obvious. For if a source of light generates light waves in the ether, once the waves are launched they are no

longer linked to their source; they are on their own, moving at the rate set by the elastic properties of the ether….

If it was so obvious, though, why did he need to state it as a principle? Because, having taken from the idea of light waves in the ether the one aspect that he needed, he declared early in his paper, to quote his own words, that “the introduction of a ‘luminiferous ether’ will prove to be superfluous.”

We see in all this the working of an extraordinary intuition. The beautiful thing about Einstein’s cunningly chosen pair of principles is that each by itself seems harmless, yet the two together form an explosive mixture destined to rock the very foundations of science."

--Alfred Centauri 21:48, 16 May 2006 (UTC)

Those quotes actually state what I am trying to say: Source independce alone admits the aether theories. After all, that was the accepted state of theorizing on the behavior of light before 1905. What Einstein did was to say that

light is always propagated in empty space with a definite [speed] c which is independent of the state of motion of the emitting body

(bolded emphasis mine). Without the bolded words, which declare the global invariance of c (as opposed to the invariance existing only in the aether frame), you are not constrained to the special theory of relativity. It amazes me that I have to teach people who are active editors of this page about that very fundamental fact. --EMS | Talk 22:11, 16 May 2006 (UTC)

EMS, it's not allowed to let your personal opinions overrule the sources. Simply disregarding Pauli etc. and deciding to impose your own view isn't appropriate. And it amazes me that you both don't understand and deny that since Pauli the LT are derived without any need for your bolded words. Harald88 23:33, 17 May 2006 (UTC)

Let's see --

• From Rindler, Wolfgang (1991). Introduction to Special Relativity (2nd edition ed.). ISBN 0-19-853952-5. {{cite book}}: |edition= has extra text (help):

  First postulate: The laws of physics are identical in all inertial frames.

  Second postulate: Light signals in vacuum are propogated rectilinearly, at the same speed c, at all times, in all directions, and in all inertial frames.

• From Ellis, George F. R. (1988). Flat and Curved Spacetimes. ISBN 0-19-851169-8. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help):

  First postulate: The laws of physics are the same for all non-accelerating observers.

  Second postulate: The speed of light in empty space is the same for all observers, independent of the motion of the source and of the observer.

• From Bowler, M. G. (1976). Gravitation and Relativity. ISBN 0-08-020408-2.:

  ... we can obtain the [Lorentz] transformations by abstracting from Maxwell's equations one property: that the velocity of light is a universal constant.

Tell me Harald88: If Pauli's opinion is one that words I bolded are not needed, and if that opinion has been operative since 1921, then how is it that these three authoritative and much more modern sources all make reference to c being the same for all observers? Perhaps for you the most damning of all for you is M. G. Bowler's statement, which references only the constancy of the speed of light, and leaves the first postulate implied by the word "universal". As best I can tell, you are basing your view on Alfred Centauri's noting that Pauli says that the second postulate outrules the emission theories and the first postulate outrules the aether theories. But have you read that book yourself? I have found the relevant parts, and find that quoting from Pauli's book (Pauli, W. (1921). Theory of Relativity. ISBN 0-486-64152-X.) will help to clarify the issue:

[Einstein] showed that only the following axiom in electrodynamics need be assumed: The motion of light is independent of the motion of the light source. ... There is no question of a universal constancy of the velocity of light in vacuo if only because it has the constant value c in Galilean frames of reference. On the other hand its independence of the state of motion of the light source obtains equally in the general theory of relativity. ...

So it turns out that Pauli chose his second postulate with the general theory in mind, not the special theory alone. To obtain the special theory, Pauli still has to assert the constancy of c in "Galilean frames of reference", and does so.

I hope that this is the end of this issue. --EMS | Talk 04:06, 18 May 2006 (UTC)

EMS, we can certainly end this issue as this page is not the place for a discussion that isn't related to the current editing process. Thus I won't elaborate eventhough I disagree with your arguments and you chose to ignore the modern references that were discussed earlier; suffices to point out that a non-constancy of c is in conflict with the first postulate. BTW, above I quoted from the (text only) online version of Pauli's book: http://www.questia.com/PM.qst?a=o&d=88787417 Harald88 20:05, 18 May 2006 (UTC)

Einstein's version of the 2nd postulate does not declare the global invariance of c. Don't take my word for it - read it for yourself. Einstein's version of the 2nd postulate asserts that the the speed of light will be measured to be c in a frame of reference - the stationary frame of reference. I've said this before in earlier comments in which you more or less agreed. It is only in combination with the 1st postulate that the speed of light is declared to be globally invariant as you have put it. From my perspective, the quotes above do not support your assertion that the 2nd postulate must rule out aether theories. It is my understanding and, I believe the intent of the quotes above, that the 2nd postulate rules out emission theories and the 1st postulate rules out the notion of an absolute aether frame of reference. Alfred Centauri 23:05, 16 May 2006 (UTC)

Alfred, that is exact; thanks for doing a better job of explaining this than I did (note that it's good to mention that with "stationary" Einstein probably simply meant the chosen inertial frame). Harald88 23:33, 17 May 2006 (UTC)

I will stand somewhat corrected here. However, without the words "with a definite speed c" [or "The speed of light in vacuum is taken to be a universal constant (c)" as it now reads in the article], you do not have the key ingredient for relativity: The invariance of c. The second posulate must assert the constancy of c so that the first postulate can extent that to all inertial frames of reference. --EMS | Talk 23:32, 16 May 2006 (UTC)

With the caveat, that this is far too specific for this main article, but may be usable for the History article, I'd like to add one observation (which needs substantial sourcing, before being fit for Wikipedia):

Did Einstein, in his early expositions of the subject, give this very specific anti-Emission-theory postulate (which would be included anyway, by "just" asserting Maxell's E. to be true) because of his own attempts re Emission theory?

Note that a lot of very, very dubious stuff turns up, when googling for Einstein "emission theory", but there seems to be some beef in it, see for example: [1], [2], [3]. Einstein's, "Über die Entwicklung unserer Anschauungen über das Wesen und die Konstitution der Strahlung", Physikalische Zeitschrift 10, 817-825 (1909), need to be read on this topic. Does anybody have a link to an online version?

Pjacobi 16:34, 17 May 2006 (UTC)

The description of Einstein's inspiration is sitting right there in the first paragraph of On the electrodynamics of moving bodies. FWIW, I can tell you from personal experience that in any fruitful investigation that turns up an important but unexpected result, there is a moment of absolute inspiration such that your view of and understanding of the subject is very different afterwards than it was before. (In my own work on an alternative theory to GR, I have had two such moments). It is obvious that Einstein sometime in late 1904 or early 1905 had such a moment. One moment there was a set of contradictions before him, the next moment he realized that the contradiction was not real, and the path to special relativity was laid out before him. In others words, the second posulate is not the result of a conscious decision but instead of the realization that there was no other reasonable way to explain the existing observations. --EMS | Talk 17:59, 17 May 2006 (UTC)

---

Harald88, you can't seriously think that Einstein's "stationary system" meant just one particular frame. Which frame might that be, the one that is at rest relative to the "aether"? ;-)

(Note: probably Cadwgan confused me with Alfred Centauri) Harald88 23:33, 17 May 2006 (UTC)

You must have overlooked Einstein's quotes around his word "stationary."

But I see from your above that you do indeed seriously believe this, so here is a direct quote from Einstein - from a mere 2 pages after your cited part:

[from Einstein's 1905 SR paper:] "We now imagine space to be measured from the stationary system K by means of the stationary measuring-rod, and also from the moving system k by means of the measuring-rod moving with it; and that we thus obtain the co-ordinates x, y, z, and 'e', 'n', and 'k' respectively. Further, let the time t of the stationary system be determined for all points thereof at which there are clocks by means of light signals in the manner indicated in § 1; similarly let the time of the moving system be determined for all points of the moving system at which there are clocks at rest relatively to that system by applying the method, given in § 1, of light signals between the points at which the latter clocks are located."

We can also look at it this way: If you wish to invoke the first postulate, then you must copy exactly everything from the "stationary" frame to the "moving" frames, and, as Einstein noted above, this means copying his definition of clock "synchronization," but a definition is not a law of physics, so this cannot be copied via the first postulate, which, in turn, means that the first postulate cannot apply in this case.

But, as Einstein noted, the first postulate is not involved. All it takes is his definition of synchronization in each frame.

Einstein's version of the 2nd postulate does declare the global invariance of c (if only via a definition). Cadwgan Gedrych 20:25, 17 May 2006 (UTC)

Very good again, Cadwgan. Just one quibble: As the definition of synchronization is built on the second postulate (which is a law of physics under relativity), it is carried forward to the "moving" frame by the first postulate. Other than letting your bias sneak in at that one place, the above is an excellent and informative posting. --EMS | Talk 20:56, 17 May 2006 (UTC)

(1) Yes, it appears, Cadwgan addressed his comments to Harald88 in error.

(2) Of course, when I use the the term stationary system in this context, I use it as Einstein did - as a label for a coordinate system in which the equations of Newtonian Mechanics hold good.

I strongly advise ditching the word "Newtonian". Other than that, this item OK. --EMS | Talk 16:26, 18 May 2006 (UTC)

(3) I disagree with both Cadwgan (surprise!) and EMS. Consider that the specification of Einstein synchronization in both the stationary frame and the moving frame only ensures OWLS isotropy in the moving coordinate system. One still needs to invoke the 1st postulate to assume the speed of light is c in the moving system. Don't forget that I am basing my claim on Einstein's original version of the 2nd postulate. Work it out for yourself using the same steps Einstein did in his 1905 paper until you get to the part where he says:

"With the help of this result we easily determine the quantities ξ, η, ζ by expressing in equations that light (as required by the principle of the constancy of the velocity of light, in combination with the principle of relativity) is also propagated with velocity c when measured in the moving system."

At this point, replace ξ = cτ with ξ = f(v)cτ and then proceed with the derivation. Guess what? One gets OWLS isotropy in both frames but different propagation speeds for light. Alfred Centauri 23:56, 17 May 2006 (UTC)

Alfred - You are saying much the same thing as myself, and it also is what Cadwgan is seeing but does not want to accept as being real.

BTW - Einstein did consider the case of ξ = f(v)cτ in ON THE ELECTRODYNAMICS OF MOVING BODIES [although he used Φ(v) instead of f(v)]. Towards the end of § 3, he concluded that f(v) = 1 is required to have a self-consistent theory. --EMS | Talk 16:25, 18 May 2006 (UTC)

EMS, the f(v) I have stipulated above is not the same as Einstein's a or slightly later, his φ(v). Please reconsider what I have said above. Einstein sets the speed of the ray of light (that has speed c in the 'stationary system') to c in the moving system. In my comments above, I say to instead set the speed of the ray of light to 'f(v)c' in the moving system. You'll find that this does not contradict Einstein's version of the 2nd postulate but instead, violates his version of the 1st postulate. Further, you will find that the transformation resulting from this indeed preserves the isotropy of speed of light in the moving frame but the speed is 'f(v)c' in this moving frame, not c. This result refutes Cadwgan's assertion that "Einstein's version of the 2nd postulate does declare the global invariance of c (if only via a definition)." Once again, don't take my word for it. Work it out just like Einstein did except to ignore the 1st postulate at the point where he invokes it as I outline above.

BTW, why would I want to ditch the word 'Newtonian' when that is precisely the word Einstein used? Allow me to quote Einstein: "Let us take a system of co-ordinates in which the equations of Newtonian mechanics hold good. ...we call it the 'stationary system.'". Yes, I'm aware of the fact that Einstein goes on to show that in fact, Newtonian mechanics do not hold good because they must be replaced with relativistic mechanics. Is this the point you are making? Alfred Centauri 17:37, 18 May 2006 (UTC)

Without the first postulate, all sorts of things become possible. So I see what you are up to and agree with your point. Just be advised that:

1. Cadwgan was assuming the validity to the first posulate. (His argument can be condesnsed to "the second posulate cannot be valid because the first postulate cannot possibly transfer it another inertial frame of reference". Yet his description of what results, which he considers to be a refutation of SR, is in fact an apt description of what SR is.)
2. This thread is getting OT, if not OR.

--EMS | Talk 18:09, 18 May 2006 (UTC)

While your parenthetical statements are intriguing and while I'll certainly continue to ponder their meaning, I find it difficult to reconcile the idea that this was Cadwgan's point with what he said here:

"But, as Einstein noted, the first postulate is not involved. All it takes is his definition of synchronization in each frame.

Einstein's version of the 2nd postulate does declare the global invariance of c (if only via a definition)" [emphasis is mine].

So, if I am mistaken when I understand these statements to mean that Einstein's version of the 2nd postulate alone declares the global invariance of c..., then I stand corrected. Alfred Centauri 19:36, 18 May 2006 (UTC)

Alfred - Here is the situation as I understand it:

• The second postulate declares the invariance of c for an observer.
• The first postulate extends that invariance to all inertial observers.

So you are correct that the global invariance of c is not due to Einstein's second postulate alone. (However, that invariance has to be asserted within a frame or else it cannot be extended by the first posulate. Hence my argument with Harald88.) My comments to Cadwgan are due to his false claim that the first posulate cannot transfer Einstein's definition of synchronization to other inertial frames of reference. It can and does. (If it did not, the whole edifice of relativity would collapse. Then again, that is what Cadwgan wants.) --EMS | Talk 04:08, 20 May 2006 (UTC)

Alfred (not Harold88 ;-), except as an aside), the first postulate pertains only to laws. However, the "time" of light's flight in the second postulate is given purely by definition. It is not a measured time. It is not experimental. It is not a law. Therefore, the first postulate cannot pertain to the second postulate.

The problem is, there are two entirely different versions of the first postulate, as well as two entirely different versions of the second postulate.

Above, Alfred gave this quote: (as required by the principle of the constancy of the velocity of light, in combination with the principle of relativity)

Here we have both "bogus" versions. "The constancy" here refers only to light's speed through space (as in Maxwell's equations). It is not a clock-measured (or coordinate) speed. And the "principle of relativity" here is Einstein's prime rule, Null results always, even in optics.

As I have mentioned, he used this "bogus" version of the PR to create his definition of clock "synchronization" (which - by design - follows the Null results always rule to a "T" by making sure that all frames get one-way null "results").

Given this definition of "time," we then have the real version of the second postulate, the one which says All clocks in all frames will find - by definition - light's one-way "time" to be x/c, where x is the distance from the origin/emission clock (which started on zero).

But this - as history shows clearly* - does not pertain to a law, so the the real first postulate does not pertain to the real second postulate. (*no one has ever performed the one-way, two-clock experiment.) Cadwgan Gedrych 19:46, 19 May 2006 (UTC)

EMS, correct if I am wrong, but Cadwgan's argument, as I now understand it, is that the principle of relativity applies to 'laws' but not definitions. The principle of the constancy of the speed of light is not a law but is a definition instead. Thus, the principle of relativity does not apply to the principle of the constancy of the speed of light.

The problem I see with this argument is that, IMHO, it is not the 'laws are the same' portion of the PR that transfers the synchronization method from one coordinate system to another thus rendering Cadwgan's point moot. Instead, it appears to me that it is the 'uniform translatory motion' portion of the PR that accomplishes this. Indeed, without defining the relationship between the clocks that label the time coordinate within a frame of reference, the notion of relative motion between coordinate systems is itself ill-defined.

To elaborate, whenever we actually get down to the business of using math instead of words to state the PR, we ultimately have to say something like 'the origin of the primed system moves with constant velocity v in the unprimed system' in equation form. Clearly, this velocity is a one-way velocity and so the value of this velocity is meaningless without also specifying how the clocks are related in the unprimed system. However, by the PR, the origin of the unprimed system moves with constant velocity -v in the primed system but this requires that the relationship between the clocks in the primed system is the same as in the unprimed system.

To summarize, it is my opinion that the principle of relativity has no operational meaning without specifying a clock synchronization method to be used in all inertial frames. Einstein defined a method for synchronizing clocks in a frame and so, by the PR, this method must be used in all other frames 'in uniform translatory motion'. In other words, the transfer of a defined synchronization method in an inertial frame occurs by invoking the PR alone - no 2nd postulate needed. Alfred Centauri 04:44, 21 May 2006 (UTC)

Alfred, the PR has nothing whatsoever to do with clock synchronization. The PR pertains only and directly to physical laws, laws given only and directly by experiment. For example, the PR was fully and properly invoked in the case of the Michelson-Morley experiment (note the key word "experiment") to transfer the experimental result of nullness in one frame to (experimental) nullness in all other frames prior to Einstein's definition of synchronization; so, contrary to Alfred's above conclusion, the PR certainly has full operational meaning sans a clock synchronization method, because no such method existed in 1887.

So EMS is simply incorrect in saying that "we can transfer whatever … using the PR." The PR transfers laws and only laws, and this means experimental results, and nothing else.

Here is Einstein's 1905 statement of the PR:

"The laws [note the key word "laws"] by which the states of physical systems undergo change are not affected, whether these changes of state be referred to the one or the other of two [or more] systems of coordinates in relative translatory motion."

The "relative translatory motion" part merely refers to inertial frames, which can be detected quite well without using a definition of synchronization. (All that is needed are accelerometers.) Cadwgan Gedrych 20:52, 22 May 2006 (UTC)

The gist of your statement is correct. As a practical matter, we can transfer whatever we want between all frames of reference using the PoR. To have SR, we must also use the PoR to have the speed of light be uniform and isotropic in all frames of reference. However, you are correct in that the simultaneity definition transfers without the second postulate (and in fact as Einstein stated that definition it implies the second postulate anyway). --EMS | Talk 15:25, 21 May 2006 (UTC)

Actualy, that's erroneous: Doppler detection with one clock suffices to determine speed - as you may have found out when you received a speeding ticket. Interestingly, the first direct experimental verification of time dilation was done with Doppler (Ives and stillwel). Those conventions are not essential for the theory; instead it's the theory that states that they are a matter of convention. It is similar with the system origin that you mentioned and which is also free to choose. Harald88 17:17, 21 May 2006 (UTC)

Harald88, does not doppler detection of velocity require knowledge of the propagation speed of the wave? But, to define that, we must still specify how the clocks are related. Another way to look at it is that if we can use doppler detection to detect the speed of the origin of the primed system in the unprimed system with just one clock, haven't we just specified how the clocks are related in the unprimed system?. After all, whether we use doppler detection or two clocks, the velocity result we get would have to agree, wouldn't they? Alfred Centauri 18:01, 21 May 2006 (UTC)

Alfred, I must have been tired as my comment was wrong, sorry about that! Relative speed between objects is frame dependent indeed, following the used convention. If you meant that for a comparison of the laws of nature as determined in two frames, the same measurement conventions must be used, obviously that is very correct.

What I had in mind to point out (but for some reason didn't): The predicted effects don't depend on the conventional assumption that our frame is resting in space (making OWLS isotropical), just as those effects don't depend on our choice of origin. We are free to choose the inertial reference frame that we define to be in rest; and contrary to what Cadwgan seems to suggest, that doesn't invalidate SRT nor does it affect its predictions. Harald88 23:49, 21 May 2006 (UTC)

Alfred - Harald88 is quite confused here. After all, we are discussing theory here, not practical mechanics. Also, how a radar gum operates in using the Doppler effect has nothing to do with determining the speed of the radar waves. *Sigh*. Let me put it this way, I am happier to help someone else sort out the falacies in Cadwgan's writings (although I will not argue with him directly), than in dealing with Harald's well-meaning confusion. --EMS | Talk 20:41, 21 May 2006 (UTC)

Cadwgan said: "Alfred, the PR has nothing whatsoever to do with clock synchronization". I disagree. I'm well aware that the PoR pertains to laws but it also pertains to coordinate systems that are related by uniform translatory motion. The claim that no such method of synchronization existed prior to Einstein's insight into the nature of time is objectively false. The synchronization procedure implicity defined for the PoR before Einstein's procedure makes use of instantaneous signals to synchronize clocks.

That what I say is objectively true can be ascertained by examining the coordinate transformation equations that result from just the following assumptions:

(1) Space is isotropic (and therefore homogeneous)

(2) Time is homogeneous

(3) The PoR

The resulting class of transformations show that the clocks in a frame are synchronized by signals propagating at a frame invariant speed. In the limit as this invariant speed goes to infinity, the transformation tends to the Galilean transformation. Setting the invariant speed to c gives the Lorentz transformation.

This is the end of this debate as far as I'm concerned. Alfred Centauri 22:56, 22 May 2006 (UTC)

You have hit the nail on the head, and I concur with ending this thread. I suggest archiving this business soon, and leaving Cadwgan alone for now. --EMS | Talk 23:50, 22 May 2006 (UTC)

The PR does not call for or produce an invariant light speed. Isotropic space does not call for or produce an invariant light speed. Homogeneous time does not call for or produce an invariant light speed.

As I said before, the PR allows Einstein's w = c ± v in all frames, and this is a variable light speed.

And there was no experimental or operational definition prior to Einstein. The PR would apply (if it applies at all) only to actual definitions, not flights of fancy (such as your infinite-speed signals).

Also, what would happen if, as you claim, the PR somehow pertains to even the fanciful "definition" with its infinite-speed signals? How would clocks be set by such signals? How would such clocks differ from those set per Einstein's definition?

If one does not know the simple difference between 
Einstein's and Galileo's clocks, then one cannot grasp 
the difference between the Galilean transformation 
equations and Einstein's transformation equations.

But let's return to the goal here - that of producing a proper second postulate section in the article.

As anyone should know, a physical postulate must pertain to something physical - specifically, a future experiment. To which future experiment does the 2nd postulate pertain?

Given that the 2nd postulate pertains to light's speed, we can use the process of elimination to get rid of light's raw speed through space (per Maxwell's equations) and light's round-trip speed (Michelson-Morley experiment).

Therefore, the 2nd postulate must pertain to light's one-way speed.

What does the postulate say about this speed?

As everyone knows, it claims that it is invariant and isotropic.

But there is no experiment that could possibly show this.

Thus it appears that the 2nd postulate is not a scientific postulate because it does not predict the result of a possible scientific experiment.

The alleged "experiment" has never been performed.

In fact, no one has even shown on paper how to perform it, using the ideal clocks and ideal rulers of theoretical physics.

This fact can also be applied to the first postulate (the PR), as follows:

Name one IRF in which light's one-way speed is invariant and isotropic.

Since there has not been even one such frame, it is clear that the PR does not apply to the one-way, light speed case.

Not only has no frame found one-way invariance/isotropy, but it is physically impossible for this to happen experimentally.

Where is this simple fact mentioned in the article?

Einstein gave this fact by stating that it is impossible to have any sort of time involving more than one clock unless one uses a definition, with no one-way experiment involved.

No one has shown the Lorentz invariance of light's one-way speed per two clocks in the same frame, and no one can do this. It is simply not possible.

Does this sound like something that should be left out of an section about the second postulate (or the first postulate)?

How does one go about transferring a blank page (the lack of a one-way experiment) from one frame to another using the PR (as EMS mentioned)?

How does one postulate about nothing? Cadwgan Gedrych 20:20, 23 May 2006 (UTC)

Latest version of the second postulate

I like Harald88's latest rewrite of the second postulate, although I have tweaked it by removing the weasel words "taken to be". I hope that this can be the end of the discussions on this matter. --EMS | Talk 23:50, 16 May 2006 (UTC)

Looks good to me too. The a vacuum is a nice touch. Alfred Centauri 00:18, 17 May 2006 (UTC)

That is something that Einstein was very specific about but which had gotten lost in the shuffle with this article. I thank Harald88 and DAG for restoring it. --EMS | Talk 04:11, 17 May 2006 (UTC)

As to the weasel words, that may have been my fault, as he might have taken a suggestion of mine above and tweaked it a bit. If so, sorry about that. I was just being wordy, at least speaking for my suggestion.

But I think it's otherwise not loaded or any such. Other comments? DAG 00:37, 17 May 2006 (UTC)

Indeed I took your suggestion and it still looks fine to me after EMS's tweeking. With a little luck we can now spend our editing time on more constructive matters. :))

Anyone here who wants to contribute to a short section on the light speed debate, in particular by providing sourced quotes from which we can make a selection? Harald88 23:17, 17 May 2006 (UTC)