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½==Herbert Dingle article== First, glad to see you now have a username. It's hard to tell people apart when there are several IP names at one time. You may wish to put something (anything will do) on your user page, and then the links to your name will appear in blue instead of red.

Due to the high noise to signal ratio on the Dingle talk page at the present time, I'll say a few things here. To your question "is time dilation under inertial motion symmetric or asymmetric?", the answer is that it is symmetric, with the caveat that the question isn't very precisely phrased, though I think I know what is being asked. It is true that ${\displaystyle \left({\frac {\partial t'}{\partial t}}\right)_{x}=\left({\frac {\partial t}{\partial t'}}\right)_{x'}}$ to use the phrasing in the detested mathpages article. However, it doesn't follow that special relativity is inconsistent due to that reciprocity. Dingle was in error on that last point (as per vast majority of physicists and per my own understanding of special relativity, linear algebra and group theory). How exactly that fits into the historical debates between Dingle and McCrea, I can't say, because I haven't read them. It's silly that some have labeled this an issue of editors taking sides between Dingle and McCrea, as the article is about Dingle. His claim is clearly wrong. Anyway, enough about that; I don't intend to get into a drawn-out debate.

Yes, there are plenty of details of Dingle's life that should be included in the article. Some of the current wording should also be changed. I agree that the sentence talking about the "commonsense" method is totally unclear. Even the statement that the Dingle-McCrea debates are well-known isn't entirely accurate either, but I couldn't think of a quick way to improve it in my last edit.

Happy editing and try not to take any of it too seriously. Tim Shuba 03:16, 29 July 2007 (UTC)

My reply Herbert Dingle Article Tim,

Thanks for your reply

The question "is time dilation under inertial motion symmetric or asymmetric?", seems pretty straightforward to me, I have taken the wording more or less directly from the wiki article on time dilation, what is it you dont understand? The exact wording there is: "Time dilation is symmetric between two inertial observers", would you prefer that wording?

Unfortunately, I cant find any mention of the equation, you quote, in Einstein's 1905 paper, Dingles book, or McCrae's replies, so I don't how it is relevant. Do you have a reference for this equation so I can see where Dingle used it? However, since we are dealing with a logical inconsistency/contradiction, it cannot be answered by a mathematical proof or by experiment.

The exchange between Dingle and McCrae, should have been straightforward, except that Dingle made the mistake of answering the mathematical irrelevancies put forward by McCrae. In my experience, this is quite a common ploy with mathematicians in an attempt to win an argument. I cant recommend Dingles book as a good read, he does go on a bit, but it does give you an idea of how his argument was dismissed out-of-hand without actually being answered satisfactorily. I'm a bit surprised that you twice state that Dingle was wrong, and yet you havent read letters that passed between him and McCrae. Dingle was not a random crackpot who picked up Einsteins paper one day and decided he knew better, he wrote and collaborated on several textbooks on relativity and wrote the Encycopaedia Britannica section on the subject. He was clearly well respected in this area, over a long period of time. He even discussed it with Einstein, I believe. I would think the least you could do is read what he had to say.

In the meantime, let me summarise briefly, Einsteins paper of 1905 performs a calculation on a 'stationary' clock and a 'moving' clock, and produces the result that the 'moving' clock is ACTUALLY running slower than the 'stationary' clock. This is not just the appearance that it is running slower from the point of view of the 'stationary' clock, but actually showing an earlier time when they are brought together. Dingle's point was simply that, according to the postulate of relativity, either one of the clocks could be considered to 'stationary' and the other 'moving'. Then identical calculations could be performed with the clocks reversed, producing exactly the same result, but now it is the other clock that is running slow. Obviously they cant both be running slower than the other one. This is why I said that no mathematics need be used to disprove this, since before you do any calculating, you have to decide which clock you consider to be stationary and which moving. Einstein calculated the slowing of only one of the clocks but not the other with the roles reversed. Dingles question was simply, why did he pick only one of them? what distinguished this clock from the other? What also has to be borne in mind is that in the section of the paper on length contraction of moving rigid bodies, he stated that this particular effect was reciprocal!, I think you would have to agree that there is an inconsistency there. McCrea in his replies maintained that Einstein's 1905 paper was correct and that slowing of the clock was ACTUAL and asymmetrical, and produced large quantities of equations and spacetime diagrams, to show why the situation was asymmetrical. The current view as I have said before appears to be that the 'moving' clocks only appear to slow down when viewed from the 'stationary' system and that this effect is symmetric. A point, apparently, that Einstein conceded in a book in 1922, although I dont have a reference for this book. This last bit I find baffling, since Dingle didnt mention this book of Einsteins throughout the debate, it surely would have convinced McCrea. Anyhow, I would like to hear your views on this, and also get rid of the mathpages article which I hope you can now see is irrelevant and insulting. BTW do you know who wrote it?

Swanzsteve 05:50, 29 July 2007 (UTC)

Here is a quick follow up to that equation you quoted from the mathpages, this is a quote from McCrea himself: "Dingle has not made any mistake in the algebra..." That doesnt really square with the mathpages, does it? Where did that equation come from?

Retrieved from "http://en.wikipedia.org/User_talk:Tim_Shuba"

The equation shows the symmetry of time dilation, and by the careful use of the variable held constant (x or x'), also shows why there is no contradiction due to a clock running "absolutely faster and slower" as is nonsensically claimed by some. The "moving clocks run slow" maxim is a great source of confusion for many, quite likely Dingle himself, from the quotes I've seen. There is an asymmetry in the paths of the clocks in the 'clock paradox' or 'twin paradox', but that is a different issue.

I recall that the mathpages author used the name Kevin Brown at some point. There were a couple of guesses as to who that might be, but it's a rather common name. Could be a pseudonym as well, I have no special information. It is certainly someone with a good grasp of mathematics and physics, and some knowledge about the histories of those subjects. Tim Shuba 03:42, 30 July 2007 (UTC)

Tim, This is the first time I have seen anyone claim that there is no contradiction in a clock ACTUALLY running both faster and slower at the same time, this is an incredible claim. It was certainly not said by ANYONE during Dingles life. I dont think that the mathpages article even makes this claim. Dingle certainly argued for the symmetry of time dilation, and that if it was symmetrical (in line with the first postulate), and it was an actual effect this would lead to the contradiction of a clock both running faster and slower than the other one. The current interpretation appears to be that both clocks only appear to run slow from the point of view of the other one. Dingle considered this option himself, and concluded that if this were the case, then the theory says nothing physical and was of little use in practice. I think you you should stop for a minute and consider what you have said there, and try to imagine the impossibilty of a clock running faster AND slower than the other clock. You say it is a nonsensical claim that this is a contradiction, I would say the opposite is true. In fact, if you can find ANY reliable reference source which makes this claim, then I will give up on this completely, but I dont think you will find such a source. I can only think that I have misunderstood your claim, in some way, please let me know if this is the case.

As to the mathpages equation, it clearly implies that Dingle has made some elementary error in his algebra, you say the author was "certainly someone with a good grasp of mathematics and physics", McCrea (head of the mathematics department at the Queen's University of Belfast.) as I said before, stated "Dingle has not made any mistake in the algebra...", this statement is from a reliable reference source (Nature) and as far as I know, has never been challenged. There is a serious discrepancy here, I think again you should provide a reliable reference source which confirms the mathpages claim that Dingle has made a mathematical error. Since this equation only appears on the mathpages, and is produced by someone with a clearly non-neutral point of view on Dingle, it should be removed.

As I have said before mathematics cannot be used to disprove a LOGICAL contradiction, you now appear to be taking a different approach and say that there is actually no contradiction in the physical impossibity of a clock running both faster AND slower than another clock. I look forward to your reply backing up this claim (Swanzsteve 14:23, 30 July 2007 (UTC))

My own comment may have been slightly ambiguous. I was trying to say that the claim that a clock runs "absolutely faster and slower" is nonsensical. There is no logical contradiction because the argument you keep repeating, perhaps influenced by Dingle's confusion, introduces a false premise. Your idea that a clock experiences an "actual physical change" of rate is not to be found in Einstein's writings and is in direct violation of relativity principle. Do you really think that Einstein was saying that by moving away from a clock, we can influence something intrinsic about the clock?

I can see no mention in the mathpages article about Dingle's algebra at all, just a concise explanation of Dingle's conceptual error in claiming a logical contradiction in special relativity. Tim Shuba 16:06, 30 July 2007 (UTC)

Tim, I'm glad you cleared that up, I was beginning to think you had taken leave of your senses:-)

But I'm now a bit confused about your next statement:

"Your idea that a clock experiences an "actual physical change" of rate is not to be found in Einstein's writings"

That is not my idea, that is EXACTLY what Einstein says in his 1905 paper - read the bit about clock A moving to clock B.

you then say: "and is in direct violation of relativity principle" again this is correct and this was EXACTLY Dingle's point.

this next bit: "Do you really think that Einstein was saying that by moving away from a clock, we can influence something intrinsic about the clock?" - he didnt put it this way around, he said that when a clock moves it runs slower.

Throughout the Dingle/McCrea debate, they were talking about clocks actually, physically running slower (or faster), not just the appearance of them running slower(or faster).

Dingle wasnt confused about this point, but you appear to be.

your next statement: "I can see no mention in the mathpages article about Dingle's algebra at all, just a concise explanation of Dingle's conceptual error in claiming a logical contradiction in special relativity" - again I would have to disagree strongly with this, to quote from the mathpages:

"In a nutshell, Dingle considers two systems of inertial coordinates x,t and x',t' with a relative velocity of v, and then considers the partial derivative of t' with respect to t at constant x, and the partial derivative of t with respect to t' at constant x’. He notes that these partials are equal, and declares this to be logically inconsistent for any v other than 0. Needless to say, Dingle’s “reasoning” is incorrect, because partial derivatives cannot be algebraically inverted"

It is clearly saying that his reasoning is incorrect, because he didnt realise that " partial derivatives cannot be algebraically inverted", this then would be an algebraic error, wouldnt it? - I would repeat that McCrea, a considerably more distinguished mathematician, than the person who wrote the mathpages article, considered that "Dingle has not made any mistake in the algebra..." - I find it hard to believe that McCrea would not have pounced on such an 'error' had this been the case. Apart from this, the argument used to discredit Dingle in the mathpages article has the look of a 'homebrewed' argument. If it has not been published elsewhere and peer-reviewed, it should not be included.

FYI - here is the relevant paragraph from SRT 1905 (available at: http://www.fourmilab.ch/etexts/einstein/specrel/www/)

"From this there ensues the following peculiar consequence. If at the points A and B of K there are stationary clocks which, viewed in the stationary system, are synchronous; and if the clock at A is moved with the velocity v along the line AB to B, then on its arrival at B the two clocks no longer synchronize, but the clock moved from A to B lags behind the other which has remained at B by ½tv²/c²(up to magnitudes of fourth and higher order), t being the time occupied in the journey from A to B."

Note: the effect of acceleration is not considered, the clock retardation is supposedly caused, purely by the inertial motion.

Correct me if you think I'm wrong, but it seems to me that the source of confusion is that you think the clock retardation predicted by Einstein is not a REAL effect.

Indeed, if this were not an "actual physical change of rate", as you put it, how could somebody try to measure it experimentally?

{Swanzsteve 02:58, 31 July 2007 (UTC))