Talk:Introduction to special relativity/Archive 2

Summary of previous talk
The archived talk is largely a debate about whether this article is sufficiently non-technical. There was some debate about whether it is actually possible to create an article that does not mention that SR is a modification of Pythagoras theorem yet still transmits the idea of relativity. (It should be noted that the article on Pythagoras theorem is not without maths). The resolution to this problem is probably to produce an entirely non-technical intro to SR to complement this current article. There is room for both a "less technical" and a "non-technical" approach.

Purpose of this article
This article gives a clear explanation of the statement on the first few pages of most modern, advanced textbooks on relativity: the space-time interval is invariant under rotations in space and time. If students can understand this statement they can understand relativity. The history of relativity and the, nowdays, pointless debates about the ether and light propagation are unnecessary here. Worse still, for this article they are a diversion and should be removed whenever anyone adds them. The purpose of this article is solely to introduce the modern reasoning behind the theory.

The maths of the modern theory is unimpeachable. Physicists have determined that this maths describes the classical physics within the scope of the theory. It is possible in the future that experiments will show that the maths is a simplistic description or even an incorrect description of the world, when this happens a new mathematical description will be applied and science will advance a further step. The only issue confronting the scientist is whether the modern theory fits the physical data - not whether "Einstein was wrong" - the modern theory is actually rather different from Einstein's original work although it produces the same net result in the form of the same Lorentz transformations. Geometer 12:49, 11 April 2007 (UTC)

Failed GA nomination
I am failing this GA nomination for several reasons:
 * 1 (a) The writing is unclear at many points and hard to follow (e.g. "the thing" is a very abstract description of line h in figure 1.1); in some places, it is simply grammatically incorrect (e.g. sentence fragments).
 * 1 (b) The structure of the article is overly complex. Most "introductions" to special relativity, such as those in The Elegant Universe, begin with reference frames, a much easier idea to understand. Even the special relativity article itself begins with that.
 * 1 (d) I found the graphs difficult to interpret (e.g. Figure 2a - is that a 3D box?). It has been suggested to me as well that it is strange to include a graph with a left-handed coordinate system in a physics article.
 * 2 While this article is written about a topic of generally accepted scientific knowledge, it still needs to provide references to a few textbooks or other reliable sources not only to back up its explanations but also to bolster wikipedia's reputation and to offer readers additional resources if they are curious to learn more.
 * Finally, on a personal note, I want to add that I found this page very difficult to follow and I am a well-educated, avid reader of popular science books. When there are two separate pages on a topic, one ostensibily labelled as an "introduction," it does not make sense for both of them to be highly technical and confusing to the lay reader. I want to make it clear that I am not failing the page on these grounds, as that would be inappropriate according to GAC; I just think that the editors need to rethink their audience. Awadewit 00:26, 17 April 2007 (UTC)


 * At last, a considered and neutral set of comments about this article!
 * The readability of the text should be improved.
 * The graphs should be replaced.
 * References need to be expanded.


 * (b) and the final note are related comments. The purpose of the article is to introduce the modern approach to relativity.  The old approach that begins with reference frames and Galileo, moves on to the MM experiment and finishes with Einstein misses the modern approach altogether.  Furthermore studies show that the old approach fails to explain relativity theory  See Student understanding of time in special relativity: simultaneity and reference frames by Scherr et al. This failure to explain relativity is not a trivial matter. Students genuinely think there is something wrong with the theory after being exposed to the old approach.  Quite rightly they believe that simply assuming that the speed of light is constant is outrageous and seek other explanations in revivals of aether theories etc. If they start with the modern approach they are unlikely to fall into the same trap. Geometer 09:57, 17 April 2007 (UTC)


 * "...We have in the special theory of relativity the Minkowskian geometry of a flat 4-space with indefinite metric... Unfortunately, it has been customary to avoid this geometry, and to reason in terms of moving frames of reference, each with its own Euclidean geometry. As a result, intuition about Minkowskian space-time is weak and sometimes faulty...."J.L. Synge, \Intuition, geometry, and physics in relativity," Annali di Matematica pura ed applicata, 54, 275-284 (1961).


 * "Many textbooks2 3 4 5 6 introduce proper-time by analyzing the propagation of a light in a light clock,1 7 8 9 10 11 which consists of a pair of mirrors that face each other and are separated by a proper distance L. One tick of this clock is the duration of one round trip of a light ray bouncing back and forth between these mirrors. The analysis is usually done in the context of a simpli¯ed Michelson-Morley apparatus12 whose arms may be regarded as light clocks. Unfortunately, most of these presentations2 3 5 work in moving frames of reference without making the connection to the space-time formulation, ¯first introduced by Minkowski13 in 1907 and later extended by Einstein.14"Roberto B. Salgado Visualizing Proper Time (2001)


 * etc. etc. The old approach is a mistake. Geometer 11:25, 17 April 2007 (UTC)

Improving the article
Its good that you have offered to help on this. The problem with teaching modern relativity is that there is a shared misunderstanding of the topic. Academic research has identified that this misunderstanding originates in the standard approach to teaching the subject (reference frames, Galileo, MM, Einstein etc.) - see Talk:Introduction to special relativity. Sixty six percent of physics undergrads get relativity wrong. Basically if Wikipedia goes for the old approach we will just be providing large numbers of extra contributors to newsgroups who are convinced that "Einstein was wrong". Einstein's assumption of the speed of light as a constant without reference to the way that this is a feature of spacetime seems absurd to most students and they go away thinking this is just a "fix". Worse still some of them waste their time trying to work out how a 3D Euclidean universe could give the illusion of a constant speed of light. A simple intro to the invariance of the space-time interval ("proper time") in a flat Minkowskian spacetime will prevent these misunderstandings from the outset. This sounds complicated but its just a minor extension to Pythagoras' theorem. Geometer 15:33, 17 April 2007 (UTC)


 * It is interesting that I was probably one of those undergrads who misunderstood SR for a long time. It wasn't until I started studying General Relativity and so had to go back over the development of SR that I really understood it - but there's so much of that when studying science. It's not that the teaching is bad or that the students are incapable, it's just that, often, you have to understand something far more complex to be able to properly understand the thing you're being taught. So, basic chemistry is still taught in terms of electron energy levels even though that is a flagrant simplification of the true situation.


 * So, we have a dilemma. We don't want to teach SR using over-simplifcations because that would be wrong. However, we can't teach SR properly because that gets too complicated. My initial thinking as to how to resolve this dilemma is to avoid entirely the article's current approach of trying to "teach" SR and instead just "explain" SR. To explain what I mean by this: idiot's guides on all sorts of topics and most basic self-learning books for computer programming are based around presenting lots of examples to the reader. They don't try to teach the fundamental building blocks, because those blocks are actually trickier to understand than the overall concept.


 * I think a similar approach might work on the SR article - trying to choose some examples to illustrate and explain SR that are devoid of mathematics and pythagorean theory. For those who are able to grasp those initial concepts, we can then build on that understanding by introducing some of the mathematics. This means that we would end up with a tiered article which ends up explaining SR at several different levels - but level one must be completely absent of mathematics in my view. I need to think about this further, but hopefully will be able to drop by at the article itself in a couple of weeks and try some edits. GDallimore (Talk) 16:20, 17 April 2007 (UTC)


 * Sounds good. I contemplated this but is it possible to explain Pythagoras' theorem (the metric of 2D euclidean flat space) without any maths at all? The challenge of explaining Minkowski spacetime is similar but worse.... Geometer 16:47, 17 April 2007 (UTC)


 * That's the thing - at it's most basic level you shouldn't need to explain any of that stuff. Those are the building blocks that SR are built on, not SR itself. They can be brought in later in the article, but they should not be the starting point. GDallimore (Talk) 17:17, 17 April 2007 (UTC)


 * You're right, of course, there must be a way to explain this subject without too much complexity. Our problem is that all those beginner's guides to relativity have cribbed from each other and perpetuated the wrong approach so we are left with trying to explain the subject from scratch.


 * It might help to revisit the real origins of the theory. Einstein studies Maxwell and realises that "c" is frame independent and proposes that physical laws are invariant.  He derives the Lorentz transformation (LT) and realises that the equations contain nothing but spatiotemporal quantities.  Therefore no aether.  Minkowski, who has studied non-euclidean geometry, realises that the purely spationtemporal content of the equations means the LT is about geometry hence Minkowski's metric and, with Noether's insight into invariance and physical laws, the modern approach is born. Einstein's original proposal that physical laws are invariant looks like a guess although it is probably based on Galileo's ship analogy.


 * Curiously, given Einstein's original opposition to Minkowski, there is a quote somewhere by Einstein where he says that he cracked SR after realising that time was to blame (I can find the quote if need be).


 * There is a lot of crud on the periphery of this story in the form of attempts to explain the aether by Lorentz, Fitzgerald, Lamor, Poincare etc. Einstein himself says that he had not even considered the MM experiment when he derived SR. Some people say this is impossible but MAXWELL + GALILEO = SR whichever way you look at it. So is the desire to weave the history of the aether into SR due to latent three dimensionalism in those 66% of physicists who dont get SR? Geometer 10:13, 18 April 2007 (UTC)


 * Galileo does look to be a good starting point since everyone would understand that, even if they don't know what Galilean/classical relativity is. The more I think about this, though, the more I realise I need to refresh my memory of some of the intricacies. Sigh... the more I learn, the more I forget... :) Sorry I can't respond more carefully to your detailed thoughts yet, but it has been a while since I've considered all these things myself. Will get back to this soon, though. GDallimore (Talk) 10:48, 18 April 2007 (UTC)


 * Here is an interesting ref: http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1972Obs....92..102J&amp;data_type=PDF_HIGH&amp;whole_paper=YES&amp;type=PRINTER&amp;filetype=.pdf It shows that this problem was around years ago. Geometer 14:01, 18 April 2007 (UTC)

Second Application for GA status
I hope you will forgive me for putting this article back in for GA nomination but the previous critique was excellent and has led to numerous changes. However, if the history of the article is inspected it will be seen that these changes are largely changes in presentation and style, not changes in content. Geometer 13:20, 20 April 2007 (UTC)

Comparison of clock readings at different places in a reference frame
If an observer has two synchronised clocks at two different places in his inertial frame of reference they read the same time. Time is not position dependent within a given frame of reference. It is only when clocks are compared between frames of reference that position dependence occurs. Please do not remove the text that describes this. Geometer 10:42, 25 April 2007 (UTC)


 * The standard time dilation equation Dt = DT / sqrt(1-v^2) is only valid for pairs of events that satisfy DX = 0. Just look at the Lorentz transformation. DVdm 10:53, 25 April 2007 (UTC)


 * "Just look at the Lorentz transformation" is not an argument. Please give the exact reasoning why the time interval reported for an observer for a clock on his lap will differ from the time interval reported by the same observer for a different clock a mile away. Your contention when you say that DT at X=0 is not the same as DT at X=1500 is that clocks in a given frame of reference are not synchronous. Please justify this. Geometer 11:06, 25 April 2007 (UTC)


 * Lorentz transformation equation Dt = (DT + v DX) / sqrt(1-v^2) reduces to time dilation equation Dt = DT / sqrt(1-v^2) if and only if DX = 0. If you have two events that are not colocal in the (T,X)-frame, then the time between these events in the (t,x)-frame is Dt = (DT + v DX) / sqrt(1-v^2). This is pretty elementary, I'd say. DVdm 11:42, 25 April 2007 (UTC)
 * Geometer, I have split the section into two parts, to assure that the idea of the Caveat does not interfere with your agenda. DVdm 12:00, 25 April 2007 (UTC)

Sounds like confusion over the meaning of "reads the same time" to me and that both of you are right depending upon the interpretation of that phrase. In any event, neither of you are putting in proper inline citations to any of the stuff you're doing so it's not a surprise that you're arguing over the content.

In my view, there is no way that this article currently meets GA status without more inline referencing when the topic is this complex. A DVdm, remember that this is an introduction. I think that some of your edits are a bit jargon-heavy. GDallimore (Talk) 12:38, 25 April 2007 (UTC)


 * GDallimore, some of my edits a bit jargon-heavy? Almost everything you see is Geometer's edits. He rewrote the entire article. The only edit you see from me is the one under the caveat, and it has been around since a long time. The only problem with it, is that it doesn't fit into what Geometer is trying to make from this article. He clearly has not understood what it is about. DVdm 14:41, 25 April 2007 (UTC)


 * Yes, I rewrote the article to try to make it GA. If there is jargon lets get rid of it. The article is a breath of fresh air in this field because it goes straight for spacetime, no messing. But can we do it justice. Geometer 16:25, 25 April 2007 (UTC)


 * DVdm, your equation derived from the Lorentz transformation shows where we differ. The Lorentz transform for time is:


 * $$t = \frac{t^' + (v/c^2)x^'}{\sqrt{(1 - v^2/c^2)}} \,$$


 * http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/ltrans.html#c2


 * For a difference between two times is:


 * $$t_1 - t_2 = \frac{t_1^' + (v/c^2)x^' - t_2^' - (v/c^2)x^'}{\sqrt{(1 - v^2/c^2)}} \,$$


 * See http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/tdil.html#c2


 * The important thing to note is that the clock is at the same position $$x^'$$ in its own reference frame.


 * The result is that:


 * $$t_1 - t_2 = \frac{t_1^' - t_2^'}{\sqrt{(1 - v^2/c^2)}} \,$$


 * Now, what you have done is assumed that the clock changes position in its own frame during the measurement of the interval:


 * $$t_1 - t_2 = \frac{t_1^' - t_2^' + (v/c^2)(x_1^' - x_2^')}{\sqrt{(1 - v^2/c^2)}} \,$$


 * (ie: Dt = (DT + v DX) / sqrt(1-v^2)) This is not the standard treatment. The clock can be anywhere in its own frame $$x^'=1000, x^'=100000$$ so long as it stays there during the interval measurement. Your contention that time dilation only applies for clocks located at the origin (X=0) is unnecessary. The illustration showing the correct analysis should be restored.


 * Geometer, it seems that you completely missed the point again. I don't talk about clocks located at the origin (X=0). I talk about clock ticks being colocal, which is expressed by $$\Delta X = 0$$. Try reading what is under the heading Caveats and interpreting it independently of your agenda. The Deltas are differences between two events. In the case of a moving clock, these events are colocal in their own rest frame, expressed by $$\Delta X = 0$$. In the case of the moving rod, the events must be simultaneous in the frame in which the rod is moving, expressed by $$\Delta t = 0$$. In the original format, there were no Deltas present, because one of the events was taken to be at the origin. DVdm 14:41, 25 April 2007 (UTC)


 * This brings us to two issues:


 * 1. Perhaps it was deleted as part of a general "reversion" of the paragraph but the illustration that demonstrates that time intervals occur between planes of simultaneity at a given point in a reference frame has been removed. Given that the text above is merely confirming this we should reintroduce the picture (with appropriate text).


 * Introduce all you want, it was irrelvant in the Caveats section. You still haven't got the point. DVdm 16:42, 25 April 2007 (UTC)


 * 2. The old issue of deriving length contraction from time dilation. Obviously, for the speed of light to be constant, this must be a valid operation. If the time taken for a light ray to bounce back from a mirror in one frame is "t" the time for this same event in another, relatively moving, frame will be the time dilated "T". The two intervals refer to the same events (the emission, bouncing off mirror and receipt in the first frame) and the length of the light paths will be related by the length contraction equation. There is no doubt that c=DX/DT and that c=Dx/Dt and that, as it is an event that is in common between the frames Dt = DT/ sqrt(1-v^2)). It is hence mathematically valid in this specific case to write that DX/DT = Dx/Dt and so get the length contraction equation. Using a light path as a measuring rod is standard relativity. All we are saying is that if Bill gets t for the time taken for light to bounce off a mirror John will get the time dilated T and this T can be used by John to calculate the length of the light path in his own frame. In other words your warning is unnecessary provided the setup by which length contraction is derived from time dilation is carefully described.Geometer 16:12, 25 April 2007 (UTC)


 * Of course this equation DX/DT = Dx/Dt can only be valid for two events that take place on a light signal, in which case both sides reduces to c. That is trivial. In the caveats section o.t.o.h. I warn about directly and erroneously deriving this equation from the equations for time dilation and length contraction. The way DX, DT, Dx and Dt are measured is entirely irrelevant. Use light signals or measuring rods or whatever you fancy. In these equations the Deltas are differences between coordinates of events. As the Lorentz transformation equations should make trivially clear to you, both equations can only be valid together if DX = DT = Dx = Dt = 0. DVdm 16:42, 25 April 2007 (UTC)


 * Please could you either quote a reference for the assertion that "both equations can only be valid together if DX = DT = Dx = Dt = 0." or show the full mathematical derivation of this statement. Geometer 08:11, 26 April 2007 (UTC)


 * A reference... Duh. You must be joking :-)
 * Here is A Full Mathematical Derivation:
 * Lorentz transformation valid for any pair of events with coordinate differences Dx and Dt in (x,t)-frame, corresponding to DX and DT in (X,T)-frame:
 * DT = g ( Dt - v Dx )  [eq1]
 * DX = g ( Dx - v Dt )  [eq2]
 * Dt = g ( DT + v DX )  [eq3]
 * Dx = g ( DX + v DT )  [eq4]
 * where g = 1/sqrt(1-v^2) and we use units with c=1 (and obviously v <> 0).
 * Time dilation equation for clock at rest in (X,T)-frame:
 * Dt = g DT    [eq5]
 * Length contraction equation for rod at rest in (X,T)-frame:
 * Dx = 1/g DX    [eq6]
 * Lower highschool algebra:
 * [eq3] and [eq5] ==> DX = 0    [eq7]
 * [eq2] and [eq6] ==> Dt = 0    [eq8]
 * [eq5] and [eq8] ==> DT = 0
 * [eq6] and [eq7] ==> Dx = 0
 * So, taking equations [eq5] and [eq6] together for one pair of events ==> DX = DT = Dx = Dt = 0.
 * I told you before: you have to understand the physical meanings of the variables before you mess around with the equations: physics is not a branch of mathematics.
 * DVdm 10:02, 26 April 2007 (UTC)

(reset indent)

The problem here is that you are not using the definition of a reference frame as a collection of comoving observers each with their own synchronised clock.

Your point that Dt = g DT is constrained for DX=0 is not strictly correct.


 * I think the main problems are
 * (1) that you have a severe reading comprehension problem. Nowhere do I say that X = 0.
 * (2) that you have no idea what you are talking about. Read my lips: you have to understand the physical meanings of the variables before you mess around with the equations: physics is not a branch of mathematics.
 * Remainder ignored (unread). DVdm 15:44, 26 April 2007 (UTC)


 * This was simply a typo. "You have no idea what you are talking about" is not an argument, it is an insult. Geometer 21:37, 26 April 2007 (UTC)


 * If it was not a typo, it makes it even worse. It shows that you have no idea what the Lorentz transformation does. It shows that you don't know the meanings of the variables. It shows that you don't know what events are. It shows that you have no idea about analytic geometry. It shows that you have no idea about the very basics of special relativity. You don't get the point of the remark and for some reason unknown to me, you drag in al sorts of irrelevancies.
 * Don't take this as an insult. It is not meant a such. I don't think I can help you, sorry. DVdm 09:34, 27 April 2007 (UTC)

Yes, for a GIVEN clock: Dt = g DT when DX is 0

But for two clocks separated by n metres in frame X,T

Dt = g DT(1)

Dt = g DT(2)

Because although each individual clock must stay in place during a measurement two separate clocks will give the same interval for a given event. ie:

DT(1) = DT(2)

So DX=0 is only a constraint for a particular clock.

Now, in a given frame of reference clocks are synchronised, they dont just give the same intervals, they give the same absolute readings.

In a given frame intervals can be determined within AND between clocks:

If DT(1) = D12 - D11

and DT(2) = D22 - D21

Then DT= D12 - D21

and DT=DT(1)=DT(2)

So why does the Lorentz transformation contain the phase term vx/c^2? If an observer in a relatively moving frame reports that DT=DT(1)=DT(2) why does an observer in another frame disagree?

The reason for this is that the Lorentz Transformation compares the absolute time in one frame with that in another for a single observer. The use of synchronised clocks at different positions in the moving frame will be perplexing to the stationary observer because it will appear to him as if they have all been artificially set out of sync by the amount of the phase term.

Thus the use of synchronised clocks is consistent with the LT but instead of Dt = g (DT + v DX) we have Dt = g (DT - vDX + vDX), the extra phase term being introduced in the synchronisation procedure.

Given this, how can we measure the length of a rod? Suppose we place a mirror at one end and time how long light takes to go to the end and back:

DX = cDT (where T is half the overall time interval)

This works because the rod, the timing device and the mirror are in the same frame of reference. Only the light moves, v is 0 so g is 1 and vx/c^2 is 0.

We can do the same thing for a moving rod in its comoving reference frame:

Dx= cDt

But can we do it BETWEEN frames? Can we measure the length of a rod that is stationary in one frame from another, moving frame?

The definition of a reference frame is a collection of comoving observers each with their own synchronised clock. All we need to do is observe the reading on the clock that is adjacent to front end of the rod when the light is emitted and then read the clock that is adjacent to the front end of the rod when the reflected light returns.

We can then use Dx=cDt to determine the length of the rod as measured from the moving frame.

Clearly then x/t = X/T can be used to compare the two lengths.

Your objection, based on the LT for a single observer, does not take into account the synchronisation procedure between clocks in an inertial frame of reference. Geometer 14:01, 26 April 2007 (UTC)

Incidently, the derivation of length contraction from time dilation is the standard method:

http://www.cosmo.nyu.edu/hogg/sr/sr.ps

http://physics.ucr.edu/~wudka/Physics7/Notes_www/node79.html

http://www.pa.msu.edu/courses/2000spring/PHY232/lectures/relativity/contraction.html

http://www.drphysics.com/syllabus/time/time.html

etc....

Geometer 16:00, 26 April 2007 (UTC)


 * GDallimore please could you put citation notices on the text. Geometer 13:01, 25 April 2007 (UTC)


 * This brings us to the second point, with the use of a mirror it is possible to measure the interval required for a light ray to traverse a given distance with a single clock. It is also possible for synchronised clocks in the same frame of reference to give the same result. The existence of these possibilities means that it is valid to use the time dilation equation plus the constancy of the speed of light to derive the length contraction result. Geometer 13:33, 25 April 2007 (UTC)

A Failing in Wikipedia
As can be seen above, someone with a particular viewpoint can just block an article in Wikipedia. The section on "Caveats" is non standard and unreferenced. It has been shown to be incorrect but it must remain. The common reasoning where length contraction is derived from time dilation has also been blocked. I will remove the application for GA and stop bothering with this article now. Geometer 21:42, 26 April 2007 (UTC)


 * I think the fact that two people who both appear to know what they're talking about to an exernal observer who's only vaguely following the discussion illsutrates that the topic under discussion is not an introductory issue. I have therefore remove the entire section as being inappropriate for this introductory article. I'm sure the discussion would be better received and more widely discussed on the main Special relativity article. GDallimore (Talk) 09:43, 27 April 2007 (UTC)
 * In fact, I've moved it there myself. GDallimore (Talk) 09:46, 27 April 2007 (UTC)


 * Although it is extremely basic and entirely correct, it's a good idea to move the section to the main article. As a matter of fact, I was planning to do it myself, since this introduction seems to have become Geometer's private project anyway, and for obvious reasons I don't feel like revising it. DVdm 12:42, 27 April 2007 (UTC)

Much improved, but still needs work
This article is now very much imporved. It is much more direct and readable. However, some failings still remain. There is no discussion of why SR was developed and what it achieves. The postulates are not discussed. The effects are not summarized at the start. So I strongly adivse keeping what Geometer has done, but get it "packaged" in supproting text that helps to orient a reader to what is going on.

This is a topic that is going to be in need to development and enhancement for some time to come. I believe that there is a good way to orient people to what SR is about and that this is the place to do so. However, figuring out how to do it is a serious issue, and it seems to me that this puzzle has not been properly figured out yet. --EMS | Talk 15:32, 27 April 2007 (UTC)


 * With all due regard to Geometer's careful edits, I fully agree and think EMC has hit on a number of important points which I had doubts about myself. These articles take time. Let's not rush it. I mean, Einstein isn't going to care if it takes a little while longer... GDallimore (Talk) 15:45, 27 April 2007 (UTC)

Common misconceptions
This item has the misconception itself that mass increases with speed. It also fails to mention other misconceptions. Ems57fcva saw that I edited it and reverted without discussion. I think this is not good form and represents vandalism. To Ems57fcva: please either discuss here what you object to or put back my version. Thanks. Edgerck 10:32, 22 May 2007 (UTC)

BTW, my edit is available here Edgerck 10:36, 22 May 2007 (UTC)


 * The NPOV flag is crazy, the article talks about relativistic KINETIC ENERGY as the source of Newtonian physics and is correct in this sense. The use of "mass" in this context is arithmetically correct but is indeed a bone of contention amongst some physicists. Wikipedia is a place where articles should agree with most textbooks and the note on relativistic mass and Newtonian physics does indeed agree with most textbooks. It is clear that Edgerck loves the relativistic mass debate but this introductory article is hardly the place to indulge it! 86.11.125.124 09:45, 28 May 2007 (UTC)


 * I'm no expert but I think this depends on how you define mass: you can either define it so it remains constant, then momentum = gamma * mass * velocity, or you can define mass so that it changes with speed (relative to the observer, of course) and keep the non-relativistic definition of momentum. I believe some sources use one convention and some another.  Can anyone confirm this? Bistromathic 16:27, 25 May 2007 (UTC)

Richard Feynman in The Character of Physical Law wrote "The energy associated with motion appears as an extra mass, so things get heavier when they move." This POV is outdated and not used in physics today. I am sourcing this, according to WP:RS, to (inter alia) Mass. Thank you for your comment. Edgerck 19:28, 25 May 2007 (UTC)


 * Take this debate to the main article on relativity. Why are you indulging it here? 86.11.125.124 09:46, 28 May 2007 (UTC)

Because the current version of THIS page section says otherwise. The POV expressed by the current section is not mainstream for more than 50 years in research and more than 30 years in textbooks, and therefore, does NOT belong in WP -- much less in an introductory article. See the mainstream references (it is easy to find even more):


 * 1) Lev Davidovich Landau and Evgenii Mikhailovich Lifshits, (1987) Elsevier, ISBN 0750627689.
 * 2) Lev Okun, The Concept of Mass, Physics Today, June 1989.
 * 3) "Does mass change with velocity?" by Philip Gibbs et al., 2002, retrieved Aug 10 2006
 * 4) Edwin Floriman Taylor, John Archibald Wheeler, Spacetime Physics: introduction to special relativity, W.H.Freeman & Co Ltd (1992), ISBN 0716723271.
 * 5) Lev Borisovich Okunʹ, The Relations of Particles, (1991) World Scientific, ISBN 981020454X, p. 116-119, 127.
 * 6) Usenet Physics FAQ
 * 7) Gary Oas, On the Abuse and Use of the Relativistic Mass, 2005.
 * 8) "Does light have mass?" by Philip Gibbs, 1997, retrieved Aug 10 2006.
 * 9) "What is the mass of a photon?" by Matt Austern et al., 1998, retrieved Aug 10 2006
 * 10) William S. C. Williams, Introducing Special Relativity, CRC Press (2002), ISBN 0415277620
 * 11) "Ouch! The concept of `relativistic mass' is subject to misunderstanding.  That's why we don't use it.  First, it applies the name mass--belonging to the magnitude of a four-vector--to a very different concept, the time component of a four-vector.  Second, it makes increase of energy of an object with velocity or momentum appear to be connected with some change in internal structure of the object.  In reality, the increase of energy with velocity originates not in the object but in the geometric properties of space-time itself.", in Edwin Floriman Taylor, John Archibald Wheeler, Spacetime Physics: introduction to special relativity, op.cit.

Therefore, to avert a dispute and restore what is correct under WP:NPOV and WP:RS, and continue the dialogue and editing from what is WP correct, I leave it in the editor hands who reverted from my previous edit, available here, please revert back. Thanks. Edgerck 21:12, 28 May 2007 (UTC)


 * From my observation it's Edgerck who is doing the POV pushing here. As some of the references he has been citing actually confirm, the notion of relativistic mass has been used, and was never a misconception or an error, but simply a different use of language and a different bookkeeping method. Yes, it's an unfashionable one currently, and I'm happy to defer to the physicists on the point that there are good reasons for that -- but a misconception it is not. It is not WP's function to enforce linguistic uniformity; we should report these usages neutrally, and also report which ones contemporary physicists prefer. --Trovatore 21:20, 28 May 2007 (UTC)

I agree with Trovatore if he means that "relativistic mass" should be in the historical notes, because so it was in my edit. But "relativistic mass" should not be used to explain anything, as that is known to be confusing  (see Wheeler quote above). BTW, this is what Jimbo had to say about this:


 * 1) If a viewpoint is held by a significant minority, then it should be easy to name prominent adherents;
 * 2) If a viewpoint is held by an extremely small (or vastly limited) minority, it does not belong in Wikipedia (except perhaps in some ancillary article) regardless of whether it is true or not; and regardless of whether you can prove it or not.

The case is that we cannot find any prominent adherents to the case of "relativistic mass". So, it should properly be in the history notes and not in any functional way, or as minority view today.

BTW, I have seen that often a call for POV neutrality is followed by an argument that the person making the neutrality call is pushing a point. Yes, this is true in this case. I'm pushing for neutrality. There should be no compromise in this point either. Thanks. Edgerck 21:29, 28 May 2007 (UTC)
 * It does appear that in this particular case I misguessed what the dispute was, and I apologize for not having looked beforehand. The apology is limited to this one instance and should not be taken as buying your claim that you are promoting a neutral POV. --Trovatore 07:50, 30 May 2007 (UTC)

Ed Gerck is testing reliance on information in WP
See here. Count Iblis 17:20, 3 June 2007 (UTC)


 * This is a really really bad idea. But it does explain a lot. I don't know that his credibility will ever recover after a stunt like this, though. --Trovatore 17:23, 3 June 2007 (UTC)


 * There was NO incorrect information inserted in my edits. My experiment rules make this absolutely clear.


 * Regarding WP purpose's, I edited exactly those articles that were NOT neutral. All my edits are documented and explained.


 * All my edits represented an honest attempt to improve neutrality of the articles, which were biased to use outdated information. If, because I am not perfect and the volume of my edits was very large, any of my edits contain material that is found to be incorrect, that can be taken into account as I explain in my experiment's conditions for impartiality.


 * Further, I did not take an anonymous identity exactly so people would understand that this is an honest attempt to 1) improve some WP's "eye-sore" articles; and 2) see how long that improvement would last, be improved more, or just disappear. Thank you. Edgerck 17:39, 4 June 2007 (UTC)

Edits by User:Loom91
We had Edgerck banging a drum about mass and now User:Loom91 has got a bee in his bonnet about real and imaginary time and wants to suppress and change history. Of course the modern idea of SR is real time but Minkowski didnt believe this and Einstein in his little guide to relativity has a whole section on imaginary time http://www.bartleby.com/173/a2.html. Loom91 just reverts the truth about how SR evolved through Pythagoras to a truly non-euclidean form, depriving the reader of anything to fill the gap.


 * I'm quite aware of the history, thank you. But this is not an article on the history of Special Relativity. It is intended to be an introduction, and we don't need to clutter it by introducing the outdated concept of imaginary time. Writing -1 as i^2 does not help the reader understand anything, and may inconvenience readers who don't know about complex numbers. This article is not about the evolution of SR, nor does it concern itself with exactly what Minkowski said. It only concerns itself with giving the reader an accessible introduction tot he modern geometric formulation of SR, surely that is evident from the title of the article. I also recommend that you get a free Wikipedia account. It's difficult discussing a dispute with an editor behind an ever-changing dynamic IP. Loom91 12:32, 19 July 2007 (UTC)


 * You incorrectly assigned the real time interpretation of SR to Minkowski then, when this was corrected, simply reverted back. The article is indeed about the history, it goes from Pythagoras, through a pseudo-euclidean space to a non-euclidean spacetime. This is SR, a replacement for Pythagoras' theorem. Do you really think that jumping straight into the maths of bilinear forms is going to be more accessible to readers than Pythagoras with imaginary numbers?

NPOV
User:Loom91 is simply suppressing the true role of Minkowski in SR because of some passionate belief that all mention of imaginary time should be suppressed. This is a biassed POV, the truth should be included in the article.
 * Please take this to History of special relativity. The material can be in a footnote or section in special relativity, dealt with in full at History of special relativity, and a clear, brief layout of the history should be left here for those not wanting the full details. Carcharoth 13:02, 19 July 2007 (UTC)


 * Are you genuinely sayinmg that Pythagoras' view of the world as a 3D Euclidean space should be included in this article but Minkowski's pseudo-euclidean approach should be purged? Are you really saying that Minkowki should be described as being responsible for the real time approach when he wasn't?  What is going on here????


 * I've put the material in a footnote to stop diverting from the flow of the text. Though it does not seem appropriate in this article even as a footnote. As Carcharoth says, it should be in the history article. It does not help in introducing SR to the reader. Loom91 13:09, 19 July 2007 (UTC)


 * I have changed the text to be true to the development of the subject
 * I think a footnote is more appropriate. Carcharoth 13:41, 19 July 2007 (UTC)

Specifically Introduction to special relativity (actually labelled number 5). Please focus on the accuracy of that, keeping it brief, and add long and detailed explanations at special relativity or history of special relativity. Carcharoth 13:42, 19 July 2007 (UTC)

This is an odd debate. Minkowski did actually propose a pseudo-euclidean spacetime and the necessity of real time is actually a requirement of GR, not orthonormal SR:

" One approach, often used in elementary textbooks [and also used in Goldstein's (1980) Classical Mechanics and in the first edition of Jackson's Classical Electrodynamics], is to set $$x^0 = it$$, where $$i = \sqrt{-1}$$ and correspondingly make the time basis vector be imaginary,... When this approach is adopted, the resulting formalism does not care whether indices are placed up or down; one can place them wherever one's stomach or liver dictate without asking one's brain. However, this $$x^0 = it$$ approach has severe disadvantages: (i) it hides the true physical geometry of Minkowski spacetime, (ii) it cannot be extended in any reasonable manner to non-orthonormal bases in flat spacetime, and (iii) it cannot be extended in any reasonable manner to the curvilinear coordinates that one must use in general relativity. For this reason, most advanced texts [including the second and third editions of Jackson (1999)] and all general relativity texts take an alternative approach, which we also adopt in this book. This alternative approach requires introducing two different types of components for vectors, and analogously for tensors: contravariant components denoted by superscripts, and covariant components denoted by subscripts." Blandford & Thorne (2004)."

One of the reasons that imaginary time stirs up such passion is that Feynman and others used it too freely in the development of QED (initially beyond Wick rotations). Textbooks have often used imaginary time in their intros and from what I saw of the previous article it did this then gave the correct approach.

I think the article before the recent changes was a much clearer intro than this one, the text was more direct and it had a historical persepective. Robinhw 15:14, 19 July 2007 (UTC)


 * The main argument is that most modern texts don't use imaginary time anymore and it does not provide any noticeable improvement to understanding. The concept of imaginary time is not easier to understand than a modified distance formula. This article is supposed to serve as an accessible intro to the more technical and extensive main article, not give an historical perspective. Could you give some specific examples where you think the previous version was more understandable? Loom91 12:05, 20 July 2007 (UTC)


 * No, this is scandalous. Gilbert and Borel's work is being called Minkowski's!!! Wikipedia is a pile of rubbish if editors don't bother to read the references. Minkowski had a pseudo-euclidean theory and this was central to the development of SR.You know you are wrong because you are using Minkowski's name everywhere but missing out the truth about his contribution.


 * Before you continue this rant, read the article. Read the footnote. See, don't assume, what is attributed to whom. Loom91 12:05, 20 July 2007 (UTC)

I agree with Loom91, Robinhw and others, and disagree with the unsigned comments. Please sign your comments with four tildes. This article is no place to discuss the out-of-date and confusing conecpt of imaginary time. Timb66 22:51, 20 July 2007 (UTC)


 * You missed the whole point. I am simply trying to be historically correct.  Physics has gone from pythagorean to pseudo-euclidean to non-euclidean in its treatment of spacetime.  This is fascinating and has been used by numerous authors of textbooks of SR to show how views have changed. Why you are all trying to suppress history is beyond me. Its like a desire to stop people having "wrong thoughts". Its creepy the way you gang up as well.


 * I wasn't going to say anything in this debate, but am aggrieved by the constant accusations of bad faith that you are making. It has been previously discussed, and I happen to agree with the conclusion, as do several other editors, that this article would best serve the title of "introduction" by avoiding discussion of the changing views of SR over the 100 years of its history. As has already been pointed out to you, there are other articles which deal with said history. Nothing is being suppressed, nothing is being ignored, it is just that right here is not the appropriate place for everything you want to add. This article needs work, but pushing it in that direction is repeating work done elsewhere and not improving this "introductory" article. Please also sign your posts with four tildes ~ to make reading of the debate easier. Thanks. GDallimore (Talk) 10:56, 24 July 2007 (UTC)


 * And another one jumps on top! All I am saying here is that the comment in the text is true, all that relativity says is that the universe is composed of four dimensions with a signature ---+ . The article should say that this was discovered by moving from 3D +++ to 4D ++++ to (3+1)D +++- (or ---+).  This is all there is to a full understanding of special relativity. Real time is the current idea of spacetime. The metric of spacetime has a negative coefficient in the metric tensor.  The coefficients of the metric tensor are differentials expressing the deviation from the tangent plane to a surface. In the case of real time +++- they indicate that the differentials describing the curvature of space against time are negative.  Real time means time exists and it really interacts with space, real time is scarcely different from imaginary time if the spacetime is flat.  So why the rampant fundamentalism?  Why are you all so keen to deny what Minkowski really thought?  A bit of extra knowledge isn't going to ruin anything.


 * This article is explaining that all that relativity says is that the universe is composed of four dimensions with a signature ---+ it says Pythagoras had a 3D universe then it simply jumps to the modern approach. The article is about the progression from Pythagoras to the modern approach so why does it include Pythagoras and exclude Minkowski?  It seems to me that everyone has got some sort of bee in their bonnet about imaginary time but why be afraid of it? Is it because they dont understand that real time +++- is even more emphatically describing the intertwining of space and time? Minkowski is just an intermediate step. Its not history, its an essential part of an explanation of the progression of concepts on spacetime. Since the "politically correct" movement it is interesting to see how censoring the past has become popular in all walks of life. If one person says "its better that they dont know this" everyone jumps on anyone who disagrees. (OK Ive got an account). Jumpedon 12:41, 24 July 2007 (UTC)


 * This article does not need to explain everything to be complete and certainly does need to explain the entire history of SR. It is supposed to be a simple introduction. This is the point you are missing. Imaginary time is not suitable for an introduction to special relativity. There are other articles where this subject matter would be suitable and welcomed. Stop trying to make this article more complicated than it already is and than it needs to be, thus moving it away from its intended purpose and instead work on improving related articles than can stand the complexity of imaginary time. Pythagoras is mentioned because that is something that most people will have experienced at school and might give them a head-start into understanding SR. Throw in imaginary time and people will give up. I personally think that pythagoras can be dropped as well, but haven't yet worked out how...


 * Perhaps if everyone disagrees with you, we have a point. In any event, article structure is created by consensus and you are making no progress in obtaining any consensus by being belligerent, accusing people of fundamentalism and political correctness, whatever that means in this context. GDallimore (Talk) 12:52, 24 July 2007 (UTC)


 * No, you don't have a point just because there are lots of you. For instance, I bet most of the correspondents think that real time discriminates time from space whereas imaginary time doesn't - if you look at the derivation of the metric the reverse is actually true! The reason imaginary time is not favoured, even though it separates out time in the formalism of complex numbers, is that it cannot deal with the spacetime curvature in GR properly, spacetime does not contain a proper bilinear form.


 * Imaginary time is not particularly complicated - many readers will have heard of the "square root of minus one" and all of them will have heard of Pythagoras. It is much less complicated than the gaussian theory of surfaces and curvature that underpins the real time interpretation!


 * And now you want to get rid of Pythagoras. The article says "With the statement of the Minkowski metric, the common name for the distance formula given above, the theoretical foundation of special relativity is complete." This was put in by the real time guy. I agree with it.  If you get rid of Pythagoras you will have missed the whole point of special relativity. SR is a theory of spacetime, if the reader doesn't get that they don't understand it. Explaining SR is the same as explaining the metric and its consequences. Do you think that SR is a theory of spacetime?   Jumpedon 13:14, 24 July 2007 (UTC)

While I agree that SR is about geometry and to drop Pythagoras will be counter-productive, imaginary time does not help the reader understand. That is the start and finish of it. Other editors agree with me. I respect your opinion, but you must understand that in Wikipedia articles reflect the consensus of editors. Loom91 19:39, 24 July 2007 (UTC)

Jumpedon, I teach SR at university and I can assure you that bringing in tensors and metrics does not make for a good introduction to special relativity. Please listen to the arguments: such concepts do not belong in an introduction to SR. Timb66 06:24, 25 July 2007 (UTC)


 * Snap. Of course it helps to tell students that SR is the assumption of a Minkowski metric. If you dont tell them that then they end up doing arithmetic about trains and light rays and most of them come out without any idea about the subject and even believe that there is something wrong with SR. Studies show that way over half of physics students come out of SR courses without any understanding. Take a look at "Student understanding of time in special relativity: simultaneity and reference frames" http://arxiv.org/abs/physics/0207109 which is a famous paper on this subject that most lecturers on SR will have read. It shows that most teachers of SR are crap.  I came upon this page a couple of weeks back and thought "at last, a good intro to SR" then I looked again and it had almost gone. Wikipedia is rubbish on complex subjects because it uses consensus. Jumpedon 10:25, 25 July 2007 (UTC)

This article does not show that most teachers of SR are crap. It shows that students have tremendous difficulties in grasping the concepts and that, in their struggle to understand, many construct a framework that is internally inconsistent. It may help a tiny minority of students to tell them about the Minkowski metric in an introductory course/article, and perhaps you are one of them, but I have not seen evidence to suggest that it helps the majority. Keep It Simple, Stupid!. If you disagree, I suggest you contact the authors of the paper at U Washington. Timb66 00:02, 27 July 2007 (UTC)


 * Minkowski spacetime is a big word for something very simple. Read what's left of this article, Minkowski spacetime makes the idea of the constancy of the speed of light and time dilation into a trivial problem. I am surprised that you label this as "difficult". I have found that there is often an agenda behind the rejection of the derivation of SR on the basis of Minkowski spacetime by older students. The majority of students were not taught the truth and feel very uneasy when confronted by the actual assumptions underlying SR so reject them or suppress them. It is also the case that some people (who were badly taught) have spent years believing that SR is wrong because they have applied Euclidean ideas to Einstein's insights and find the rigorous approach to be a loss of face. There are also people who are pushing a process approach to physics and want to suppress a geometric approach entirely. Which are you? Jumpedon 10:15, 27 July 2007 (UTC)

I am very skeptical of any assertion that something "makes the idea of the constancy of the speed of light and time dilation into a trivial problem." Those ideas are highly non-trivial and highly counter-intuitive. That is why it took so long for them to be discovered. There is no getting around the fact that SR is "weird" and we should not try to hide it. To answer your question: I have never believed SR is wrong, nor am I pushing any particular approach, except to insist that an introduction to SR should be kept as simple as possible, but without hiding the fundamental difficulty of the material. Timb66 05:46, 29 July 2007 (UTC)

Where has the article gone?
This was a really good article once. Dypteran 21:58, 24 September 2007 (UTC) Like someone said above this really is a problem for Wikipedia because the people who wrote the first version were proper physicists who knew what they were talking about and now the article is messed up with stuff from popular science books. Minkowski did start with imaginary time and the new way of doing SR does really have less separation between time and space than the imaginary formulation. In the new way of doing SR time really does affect space but in the old way you could always say that imaginary time was somehow separate. I think the people who changed this article didn't understand this. Dypteran 22:45, 24 September 2007 (UTC)
 * What exactly is your concern? Loom91 06:59, 25 September 2007 (UTC)
 * Dypteran, I agree that some parts can and should be rewiewed. I had a quick look and made some obvious changes. Feel free to do the same. If in doubt, use this page to propose.
 * I don't really see you point about "the imaginary formulation". It is clearly mentioned in the Notes section. Do you think it needs more attention, or less? DVdm 10:24, 25 September 2007 (UTC)


 * I am a little bit uneasy about the changes. The previous article clearly said that SR is the physics of Minkowski spacetime but now it says there is Galilean relativity, frames of reference etc.  I can see trains and platforms popping up at any moment.  It does seem odd to me that you can talk about Galilean ideas as valid history but Minkowski's imaginary time is banned because it might pervert the reader.  So long as there is a section that says that Minkowski's imaginary time is history there should not be a problem. Feynman used imaginary time in his introduction to SR and I can remember contemporaries at uni saying "I get it!" about SR. What imaginary time does is bridge the gap between a Euclidean, Newtonian approach and a non-Euclidean, metrical approach.  It alerts people to the idea that "its the geometry, stupid". SR is not an amendment to Euclidean ideas, its a total replacement of world geometry and this needs to be explained. If this is not explained the students will just think that physicists are stupid, changing the whole of physics just because light rays give an odd result in the MMX. Robinhw 16:52, 26 September 2007 (UTC)


 * Indeed, keeping the plus-signs-format of Pythagoras' theorem intact, imaginary time bridges a little gap between Euclidean and Minkowskian, but doing so it creates a much bigger gap between special relativity and general relativity, the generally non-Euclidean geometric theory par excellence. See the comment in The geometry of space-time in the main article on special relativity. Anyway, we are supposed to discuss the article here (not the theory), and it is a fact that imaginary time has become out of fashion in special relativity, and as good as never used in the general relativity literature. You see that reflected in these articles. The concept is still mentioned in remarks and notes sections because there are still physicists and mathematicians around who were educated the old-fashioned way, you and I being two of them :-)
 * On the side, also note that "imaginary time" tends to scare off beginners and the general public. Many already go berserk over the mere mathematical concept of "imaginary numbers". How do you think they feel when they are offered "imaginary time"?
 * DVdm 18:21, 26 September 2007 (UTC)


 * How can we teach SR so that the reader gets its essence? Modern SR is Minkowski spacetime plus Noether's theorem and the original form of this article made this clear. If the reader can be taught this they dont need to know about reference frames or Galilean relativity, trains, platforms or even vectors.
 * It is a sad fact that popular science books confuse students because they all take Einstein's early route into SR. Students ask "how could the speed of light be constant?" and seek various adjustments within Euclidean space and electromagnetism to account for this. The amendments to the article have moved it back onto this path. This is a shame because unless students understand from the outset that SR is about a different world geometry most of them will miss what is probably the greatest intellectual achievement in human history.
 * How do we show that the idea of space and time went from Pythagoras to the present concept? Should we be true to history and report the ideas of Minkowski as a historical step? Can anyone formulate the current concept of world geometry in terms that can be understood by a 16 year old?
 * Well, I am sure this is all very difficult but I am also sure that the standard way of teaching SR to general students creates more skeptics than people who understand the theory. Well, food for thought anyway. Robinhw 15:49, 27 September 2007 (UTC)


 * Yes, food for thought, I agree. But as this is an encyclopedia, it is intended -(you might say doomed)- to closely reflect this "standard way of teaching SR", even if indeed SR was never intended (and is never used) to help us understand and model the kinematics and dynamics of macroscopic objects like trains and platforms :-) DVdm 16:23, 27 September 2007 (UTC)


 * This is an interesting problem because modern physics textbooks for those specialising in relativity frequently start with the statement "assume spacetime is described by the Minkowski metric" or similar and then derive the LT etc. using matrix algebra or tensor maths. Unfortunately "Relativity for idiots" starts with trains and leaves the reader none the wiser. What has happened is that those working in the field have not given enough time to the problem of explaining it to laymen. They moved on from Einstein's trains in 1909 but left the rest of the population on the platform. Robinhw 18:22, 27 September 2007 (UTC)

From my experience of teaching SR at university level, I think it is unlikely that most students would find it easier to grasp the subtle ideas of this theory if it were presented as "Minkowski spacetime plus Noether's theorem". Those who have been thinking about the subject for a while can see the links (and they are indeed beautiful), but I claim that a newcomer is very unlikely to find the geometrical approach easier to understand. If you are passionate about this, I suggest a separate article. Timb66 03:28, 28 September 2007 (UTC)


 * I must agree with Timb66 on this. I have never seen that geometric approach as being anything other than a fancy way of losing people.  It's introduction here is quite useful, but staying within it produced a one-dimensional presentation which was no more accessible than the main special relativity article is.
 * This is not to say that I do not have my own complaints here. Minkowski is in all sorts way elevated above Einstein here.  Minkowski's picture is on the left side of the top instead of Einstein's, putting him in the position looked at first.  Minkowski's name is mentioned over and over again but Einstein's barely at all.  I don't want to belittle Minkowski's contribution, but at the least an explanation should be given of why they are being given minkowski's viewpoint at the start instead of Einstein's.  Another complaint is that the relativity of simultaneity is buried in the article.  That is a central concept and is needed to get any kind of a good grasp on relativity theory.  It is not for nothing that Einstein presented the train-and-embankment exercise (which demonstrates the relativity of simultaneity) fist in his article introducing special relativity. --EMS | Talk 19:13, 28 September 2007 (UTC)


 * Modern relativity is the Minkowski version. If you teach Einstein's 1905-1909 version you end up with people mucking about with dynamical explanations for why light has a constant velocity in Euclidean space. They make up silly answers or cant get the answer and end up just thinking relativity is not a proper theory and will be replaced by quantum physics or something. That was a really interesting comment by EMS when he said "I have never seen that geometric approach as being anything other than a fancy way of losing people".  All advanced textbooks use it as THE approach see for instance Carroll's lecture notes: http://nedwww.ipac.caltech.edu/level5/March01/Carroll3/Carroll1.html . Dypteran 19:59, 28 September 2007 (UTC)


 * Please look at what you just wrote: "All advanced textbooks use [the geometric approach] as THE approach".  This is meant to be a non-technical introduxtion to special relativity, accessible to any reasonably educated individual and not just to physics majors!  This is not to say that the geometric approach is not useful here, but it needs to be one of several ways of showing people what SR is and is about.  This article has tended to be almost as technical as the main special relativity article, and not a good introduction.  The exclusive use of the geometric presentation created a highly mathematical article which required strong methematics abilities to follow.  Is that really what we want from an intrductory article?  I think not.  Instead we need somthing the maps out in as accessible a fashion as reasonably possible what SR is, how it differs from Newtonian physics, and what phenomena it calls for. --EMS | Talk 20:21, 28 September 2007 (UTC)


 * Its only Pythagorean theorem. SR is a replacement for Pythagoras. Thats the truth. Thats what the main article doesnt have the space or time to introduce. Dypteran 10:35, 29 September 2007 (UTC)

Why is Minkowski being given so much prominence in this article? He is mentioned more times that Einstein! In its current state, I would not see this article as a good introduction to SR. Why not just rename it as "The Minkowski version of Special Relativity"?! And the lecture notes by Carroll referred to above are about as far from an introduction to SR as it is possible to get! Timb66 23:08, 28 September 2007 (UTC)


 * EMS, Timb66, in one of my yesterday test edits I also had swapped the two pictures - Einstein to the left and Minkowski to the right. But I immediately rejected this because this way they both "look away" from the text and from each other. That's a classic ugly lay-out error. I thought albout keeping Einstein on the left, but vertically mirror both pictures "internally". As this would destroy the authenticity of the pictures, I have swapped them again, but put Einstein "on top".
 * I also agree that the "new" version (or was this some very old one from way back?) had much too great an emphasis on Minkowski. DVdm 09:05, 29 September 2007 (UTC)

Looking at the comments I get it. There are some people who think SR is about the speed of light being constant and there are some people who think that the speed of light being constant is evidence for Minkowski space. Its a century since Einstein, the second group have the right idea. MMX etc are evidence for Minkowski space. The right way to present SR is now to propose that Minkowski space exists and then look at the evidence, not to propose that the speed of light is constant and look for the evidence. The constant speed of light is just evidence for Minkowski space, not a proper theory on its own. Readers will never get QED or GR or modern physics if they think the world is 3D with adjustments to make the speed of light a constant. The way SR is explained here is right. Incidently, GR is just a field of Minkowski patches governed by a guiding metric due to mass such as Schwartzchild's so once you get SR you get GR and QED is just a sum over possible paths in space and time so once you get SR you get quantum field theory. Dypteran 10:31, 29 September 2007 (UTC)

Someone keeps removing Minkowski's statements as if they were subversive or POV. This is amazing. I cannot find a single textbook on relativity that does not credit Minkowski with the correct formulation of the theory. Obviously some editors of Wikipedia know better. 86.14.3.60 12:30, 29 September 2007 (UTC)


 * The statement can be found on the articles Hermann Minkowski and Minkowski spacetime. This is just an introduction to special relativity, not to Minkowski. DVdm 12:55, 29 September 2007 (UTC)


 * There you have it in one. Special relativity is none other than the physics of flat Minkowski spacetime. Fail to explain this and you have explained nothing about relativity. Robinhw 15:33, 29 September 2007 (UTC)


 * Sure, no argument on that. But this is supposed to be a "generally accessible introduction to" special relativity, not a Minkowski fanclub manifest :-) DVdm 16:14, 29 September 2007 (UTC)


 * Well, it is generally accessible in that Minkowski spacetime is just an extension of Pythagoras. Minkowski spacetime is mentioned 20 times for every mention of Einstein in the average book on relativity. Robinhw 17:20, 29 September 2007 (UTC)


 * Pytharoras refers to a simple equation expressing a property of Euclidian space. I think that Minkowski spacetime is *not* "just an extension of Pythagoras". Minkowski spacetime is a radical extension of Euclidian space. It is radical because it includes a time-dimension on par with the 3 space dimensions to characterize the "points" of the space. More importantly, it is also radical because the "distance" between two of its points is no longer calculated with the Pytharogas rule from Euclidian space. The distance between points of this space being zero, does no longer imply that the points coincide.
 * Agreed with your second statement, provided you change "average book on relativity" eihter into "average advanced book on relativity" or by extenstion into "average book on general relativity" - and again, this is clearly a "generally accessible introduction to special relativity". I think EMS already elaborated on this earlier... DVdm 20:24, 29 September 2007 (UTC)