Talk:Introduction to special relativity/Archive 4

It's time to restucture this article.

First item: I notice that Loom91 redid the lead so that it once again made this sound like the start of a college seminar on MInkowski spscetime instead of being a introductory encyclopedia article on special relativity. Even worse is that Loom91 removed my discussion on the relativity of simultaniety on the basis that it makes the lead too long. I assure those who support the Minkowski spacetime approach that I do understand its significance -- After all, my primary reason for being here is the general relativity article, and that is a theory that would not have come into being without Minkowski's contribution. However, I have no doubt that it is totally over the heads of the intended audience, namely those who cannot understand SR without additional introductory material being provided! I really should not have to keep stating this over and over and over again!

The loss of the discussion about simultaneity I find to be especailly egregious! In general, noone likes to talk about it because it is so counter-intuituve and is harder to express than the more popular time dilation and length contracton phenomena. However, as I try of state in my text, it is the linchpin of relativity theory! Without it, the other pheonmena make no sense, and the various "paradox"-es put forward make relativity look like an obviously incorrect theory! IMO, that "heads up" is totally required of any introduction. What this text needs is more discussion of the relativity of simultaneoty, not less.

Overall, I am lead to the need to come up with a totally new structure for this article, possibly one in which that section on Minkowski spacetime is not present at all! Minkowski spacetime is useful only once you understand the surrounding issues, including the pieces that it is fits together. IMO, its being the presented here is something akin to trying to teach a student who has not yet studied algebra about calculus.

My suggestion for an outline is:

• The lead.
• Newtonian concepts used in special relativity
  • frames of reference
  • coordinate systems
  • coordinate transformations
  • vector and scalar quantities and how they are related.
  • velocity verses speed and the addition of velocities.
• Fundamental concepts of relativity
  • How the time of an event is determined. (i.e. observer time - distance/c).
  • Closing rate verses observer velocity/speed.
  • Four-vectors. (Sort of a breif back-door intro to spacetime, but I don't want Minkowski's name mentioned here.)
• The inconsistency between SR and Newtonian physics (why the speed of light cannot be a constant in Newton's universe).
• The primary effects of relativity
  • The relativity of simultaneity
  • Time dilation (including the light clock)
  • Length contraction
  • The equivalence of matter and energy
• The Lorentz equations (This may seem to be an odd place for them, but the effects can be described without refering to then, although in the end the Lorentz equations are the mathematical foundation of special relativity.) —Preceding unsigned comment added by Ems57fcva (talk • contribs) 03:51, 8 October 2007 (UTC)
• Experimental evidence
  • Michelson-Morley experiment
  • Fizeau experiment
  • Particle accelerators
  • The detection of muons create in the upper atmosphere at the surface of the Earth.
• Applications.
• maybe an intro to Minkowski spacetime.

IMO, these are the issues that this article should deal with. --EMS | Talk 22:02, 7 October 2007 (UTC)

EMS, special relativity is the physics of spacetime. Your introduction to this article is replacing the nature of the theory with the story of its development. Much of your suggestions above stem from this basic confusion between substance and evidence. An introductory article should say what the subject is about and THEN, PERHAPS, introduce the evidence. What you are saying is that you consider the substance of SR, the relationship between space and time and the (3+1)D world, to be too complicated to explain to our readers! Geometer 09:15, 8 October 2007 (UTC)

EMS, you are claiming that the article can not be understood by a student who has not studied algebra. That is unquestionably true, but I don't believe that's an audience we ae aiming at. The level of algebra and geometry presupposed in this article is covered by the eighth grade. I don't think this is the place to explain SR to an even younger audience. Taking the traditional approach to SR leads to confusion, particularly when we have limited space. The Minkowski formalism is more economic, more natural and, *gasp*, easier to understand! Also, an article on SR is not the place to explain what vectors mean (they are not used anyway in the article). Maybe you should think about writing Introduction to Newtonian mechanics. Loom91 12:27, 8 October 2007 (UTC)

Many high school students do not study algebra, and even fewer deal with geometry. Also, this article is being advertised as a non-technical introduction to the topic. Instead it is a math-filled essay centered on a very technical concept. I also take strong issue with such statements as "the theory was reformulated by Minkowski" or the Einstein's work is an "early version of the theory". I see Minkowski's work as an elaboration on Einstein's work, not a replacement of it. Also, you need to tell a reader what the theory is in terms that they can understand, and saying that this is a "theory of spacetime" only defines it in terms of something else that they do not understand.

I am willing to deal with the confusion issue, but even then you all need to describe where you are going with the spacetime cocept and why. Instead you just throw is out raw! If I look at that article critically as someone educated in the topic, I see your hitting the main points in good order. However, if I set aside that training and consider how I would have treated this article even as a freshman in 1975 who had not been taught SR using the spacetime cocept, I would have been totally befuddled by it at first.

Once again, that thesis that Geometer held up as being the defining work on how to teach SR makes it clear that "a strong grounding in Newtonian kinematics is needed". You all are making the classical mistake of assuming that grounding. You all also need to realize that a reader may come here having no idea about time dilation, length contraction, or even being good at algebra. I want then to walk away with some good idea of what SR is about and why is claims what it claims. Instead you all wnat to shove Minkowski spacetime down their throats. As a result, this article does not inform people, but in instead confuses them completely! --EMS | Talk 15:55, 8 October 2007 (UTC)

Loom91's Introduction

Loom91, we are basically in agreement on the introduction section. However, I feel that it is important to start it with: Special relativity is a theory in physics that.... In this case we need to summarise modern textbooks in comprehensible language so rather than saying "that describes the properties of flat Minkowski spacetime" I have simplified it to "Special relativity is a theory in physics that explores the physical consequences of the relationship between space and time within a four dimensional universe". Readers can look up four dimensional or read on for the explanation in the text of the article. Geometer 13:15, 8 October 2007 (UTC)

Comments on the lead

I'm not getting into the present dispute about the focus of this article. I just have some comments on the lead as it is now:

Special relativity is a theory in physics that explores the physical consequences of the relationship between space and time within a four dimensional universe[1][2][3].

I find this a strange sentence, as it doesn't contain any useful information about what special relativity is. I mean, one can also regard classical mechanics as a four dimensional theory. So, one must mention a few of the key ingredients that makes special relativity different from classical mechanics.

An early form of the theory was developed by Albert Einstein in 1905 to deal with issues raised by classical electrodynamics and the failure of experimental physicists to detect the luminiferous aether (which was postulated to be the medium through which light travels) "[4] (see History of special relativity for a detailed account).

Ok.

Einstein built his theory on two postulates which contradict Newtonian mechanics. Most importantly, he postulated that the speed of light is the same for all observers, whatever their relative speed with the source. This approach is explored at special relativity.

The first postulate does not contradict classical mechanics. Classical mechanics is valid in all inertial frames...

Count Iblis 13:41, 8 October 2007 (UTC)

Like Iblis, I feel that Geometer's first sentence does not do the job. Is Minkowski space the only possible formulation of SR? No, it's simply the most convenient one. It is quite possible to formulate SR without mentioning spacetime, so it is not fundamentally a theory of spacetime (unlike GTR). Also, the sentence is too technical. It does not convey any information not given only a paragraphs later, but unlike that paragraph it does not have the space to explain what it means to say. We really don't want to frighten a reader by throwing terminology at him in the very first sentence. Since it is not possible to explain what sort of a theory SR is in a single sentence, it's best to say itt's a physical theory and leave detailed explanation for the next few sentences. Loom91 13:55, 8 October 2007 (UTC)

We need a simple statement of the nature of SR. In the form that is widely accepted and is the subject of this article it is indeed a theory of spacetime. This page is stacked full of references to SR as the physics of spacetime being the conventional idea. Einstein himself (grudgingly) considered that SR was a theory of spacetime - see http://www.bartleby.com/173/17.html . I have taken account of your point that the introductory sentence is not sufficiently explicit. That said, the whole point of spacetime is that space and time are interrelated so the comment under the name of Count Iblis, that "the relationship between space and time" does not convey any information peculiar to SR is not really true - length and time are related in SR but not in a 3D universe with an independent time. Geometer 14:06, 8 October 2007 (UTC)

It's still too technical. The nature of a theory like SR can not be stated simply in a single sentence, so I don't think it's useful to try. The sentence you write does convey meaning, but only to someone who already knows what is under discussion. It's like starting the article real numbers with "The real numbers are the ordered Dedekind-complete field." It's meaningful, it's accurate, and it may well be what discussions of the real numbers will start with in a certain type of textbook, but it's not helpful as the first sentence of an encyclopedia article. Loom91 14:19, 8 October 2007 (UTC)

Poll on the lead

I just want to know what people think of the two types of lead that we have here. "Type 1" is my prefered version of 17:19, October 7, 2007. "Type 2" is the Geometer/Loom91 type of 10:11, October 8, 2007. Let's just say that I want to see it there is any consensus for one type of approach versus the other. --EMS | Talk 16:01, 8 October 2007 (UTC)

I don't care for either of them. We already have no less than three separate articles promoting the fiction that special relativity is based of two postulates, though at least the third article does hint that it is not the full story. Linking to an incoherent and misinformative article such as luminiferous aether is a disservice to the reader, and claiming that the very odd history article is a "detailed account" is nearly as bad. Unless this article is just a scratch pad for the main article, I can't see much value in Type 1, although coming up with a decent structure might eventually help to correct some of the many problems with both articles. The type-2 approach is closer to the original intent of this article, and I have some sympathy for it, but it has never been written in anything close to an introductory presentation. I believe it would be possible to have a useful intro that would focus on symmetry, discussing the relativity principle, simultaneity, energy and momentum conservation, and modern theories. Tim Shuba 15:28, 9 October 2007 (UTC)

Type 1 (version of 17:19, October 7, 2007)

• EMS | Talk
• Timb66 23:05, 8 October 2007 (UTC)
• DVdm 10:45, 9 October 2007 (UTC)
• Count Iblis 13:41, 9 October 2007 (UTC)

Type 2 (version of 10:11, October 8, 2007)

Have you driven everyone away?

I have just received a message from User:Geometer about driving him away from this article. Looking at the edit summary for this article I would have to agree. Your poll is meaningless, you (with the exception of User:timb66) seem to have driven all the other contributors away! You should be ashamed of yourselves. I have just been looking at the Wikipedia Simplified_Ruleset. Most important violations of the rules are:

Particularly, don't revert good faith edits. Reverting is a little too powerful sometimes, hence the three-revert rule. Don't succumb to the temptation, unless you're reverting very obvious vandalism (like "LALALALAL*&*@#@THIS_SUX0RZsammygoo", or someone changing "4+5=9" to "4+5=30"). If you really can't stand something, revert once, with an edit summary something like "(rv) I disagree strongly, I'll explain why in talk." and immediately take it to talk.

you guys just revert, revert and revert again. I have not seen you explain anything, you, all of you (presuming you are multiple) always demand that the other guy explains why your revert/change is not right.

Verifiability. Articles should contain only material that has been published by reliable sources. Editors should cite reliable sources for any material that is challenged or likely to be challenged, otherwise it may be removed by any editor. The obligation to provide a reliable source is on the editors wishing to include the material, not on those seeking to remove it.

Those who have questioned the way that the article is being taken away from Minkowski spacetime have given copious references to support their case. The others have just said they dont want it and reverted any changes.

Anyone who is not expert in SR will probably think that the article is being returned to a comfortable, widely accepted format. But experts will see immediately that those who have a philosophical conviction that time is independent of space have got their claws into this article and wont let go. The crazy thing is that Einstein, for other reasons, shared your belief that SR was a mistake, and said that it postulates a background spacetime that he could not defend. But Einstein had the academic rigour, even in his popular book, to report SR faithfully. He even stresses that SR could be described using imaginary time but GR requires a non-euclidean geometry.

Being a philosopher of science it always amazes me how far people will go to defend the idea of independent or non-existent time. There are obvious connections in Augustinian theology but it is still incredible that there are people who will haunt articles such as these to suppress a truthful portrayal of physical theory. SR does have a background spacetime, many people think this is wrong but surely it is better to tell it how it is and let the reader learn about GR, LQG etc. ? Dypteran 12:16, 9 October 2007 (UTC)

BTW, User:timb66, I can appreciate why you would favor the electrodynamic approach to SR. But is this a faithful portrayal of the theory? The theory of SR is different from GR because it is the arena of an extended, flat, Minkowski spacetime and the very existence of such a thing is questionable. But should we really alter the description of a historical physical theory to avoid dissonance, isnt it better to properly explain the theory of SR to get the students questioning? Remember, Feynman applied a very eccentric mix of old style SR and Lagrangian physics to make QED. Dypteran 13:19, 9 October 2007 (UTC)

Dypteran - You have lost all credibility with me with your claim that "Einstein [believed] that SR eas a mistake". Maybe if you provided a reference so that I could see what the "other reasons" you refer to are I may be in some kind of agreement with that statement, but to just plain say that Eintein felt that SR was a mistake is so abviously false that it is laughable.

Everyone who has studied Einstein's contribution to GR knows that he regretted the formulation of SR in terms of a background spacetime, as I said, "it postulates a background spacetime that he could not defend". In Einstein's GR the field supecedes any background geometry. Einstein regretted being misled for a few years by a purely geometrical interpretation. I would look up the ref but everyone knows this. I would stress that I have not said that SR is wrong in its domain of applicability, just that Einstein was a fine philosopher who felt that it's substantivalism had been an obstacle to his later work. Dypteran 18:51, 9 October 2007 (UTC)

Interesting. I had not been aware of that, and was only peripherially aware that Einstein had been looking for a background spacetime initially. Certainly is it correct that GR as formulated by Einstein does not support a backtground spacetime. (I have been working on a theory of gravitation that does utilize a background spacetime, but what I have discovered about it only serves to strengthen that case the GR cannot support a background spacetime.)

Beyond that, I fail to see how a concern related to GR should dictate how SR is taught, especially to a non-technical audience. --EMS | Talk 20:09, 9 October 2007 (UTC)

I will admit that Einstein realized the value of Miknowski's work as soon as he saw it, and understood that he had been trumped. (His comment was "I should have paid more attention in his classes", since Minkowski was one of his college professors.) However, the placing of SR on the foundation of spacetime does not in any way make SR itself a "mistake".

My big problem is that this article is not a non-technical introduction to SR. Instead, it is one that presupposes a very high level of knowledge of math and science. If you want a reference, see Einstein's book "Relativity: The special and general theories". In that book, he avoided talking about Minkowski spacetime until the end of the part of SR for the same reason that I want to avoid it here: This is not an introductory concept, even if it is an excellent way to teaching SR to physics majors as part of a weeks-long discussion of SR. Like it or not, we can't put that material in a weeks-long course here, nor is a "non-technical introduction" something that should be uniquely aimed at physics majors.

I keep saying that this article throws the reader to the wolves. I can see where it is going and how, and as someone else who had Minkowski spacetime be the key to putting special relativity into a coherent whole I appreciate that. However, as-is this article sails over the heads of the uninitiated! You almost need to already know the material here to understand it, and that is totally un acceptable in a "Introduction ..." article.

My lead is intended to say what special relativity is in terms that an average man on the street can grasp. After all, Wikipedia is an encyclopedia, not a college seminar. --EMS | Talk 15:04, 9 October 2007 (UTC)

One of the big problems with this type of article is that editors are mostly anonymous. The pro-Minkowski group, if I might call them that, are asserting that SR is easier to understand by their method, but they have not presented any references, textbooks or other sources. (The work by Scherr, with which I am familiar, says that many students don't understand SR -- not a big surprise -- but does not even mention the Minkowski formulation as an alternative). In a specialised area such as this, people are all claiming to be experts, but it is impossible to check. Dypteran, you imply that you are an expert, so would you like to give some details on your experience? I know this is not a requirement for Wiki, but it might help your case. Otherwise, you need to find sources to back up what is, in my view, an unconventional viewpoint. By the way, please do not insert comments into other people's comments. Timb66 23:58, 9 October 2007 (UTC)

On the subject of relinquishing anonymity, you must be kidding!

On the subject of Minkowski spacetime and teaching relativity, there is a paucity of good work in this area. However, there are some publications of interest. Certainly the first step is to describe what sort of theory is represented by SR. There can be no doubt from the literature that it is the physics of flat Minkowski spacetime. There are two excellent online books that stress this:

Kip Thorne and Roger Blandford in their Caltec physics notes say: "Special relativity is the limit of general relativity in the complete absence of gravity; its arena is flat, 4-dimensional Minkowski spacetime."

Sean Carroll says: "..it makes sense to think of SR as a theory of 4-dimensional spacetime, known as Minkowski space." You will no doubt be familiar with Carroll. His approach is excellent for undergrads specialising in this area.

There are countless hardcopy books that say the same thing: SR is the physics of flat Minkowski spacetime.

The second step is to decide how to teach this truth. There are two options.

1. You can tell students that SR is the physics of flat Minkowski spacetime, give an overview of what is meant by Minkowski spacetime then derive some results.

2. You can start the students on classical electrodynamics, talk about Newton, Galileo, aether, reciprocity, Einstein and MMX then, having used the LT to derive the Minkowski metric say that all the results that we have been talking about are explained by assuming that Minkowski spacetime exists.

The second approach is widely used in introductory texts with bad results. The first approach, exemplified by Carroll, is general in advanced texts. There are two problems with using the second approach. The first is that when questioned students cannot say what SR actually is, if you ask them hardly any will say "its the physics of flat Minkowski spacetime". If you dont know what you have learnt then have you really learnt it? Secondly, and not surprisingly given the first point, the students have a poor understanding of the predictions of the theory. Scherr et al point out that there is a failure to understand simultaneity amongst students. This concurs with my experience and probably concurs with yours. You are quite right that Scherr et al are short on answers to this problem. However, the answer is quite clear, given that this is a geometrical problem the students should use a geometrical construction. Look at Figure 1(b) in Scherr's article. If the students are taught to draw the line of simultaneity between the two eruptions (the x axis of the ground frame as viewed from the spacecraft) they cannot fail but to see the answer to the problem. What do Scherr et al actually say? Their conclusion is reproduced below:

"This investigation has identified widespread difficulties that students have with the definition of the time of an event and the role of intelligent observers. After instruction, more than 2/3 of physics undergraduates and 1/3 of graduate students in physics are unable to apply the construct of a reference frame in determining whether or not two events are simultaneous. Many students interpret the phrase “relativity of simultaneity” as implying that the simultaneity of events is determined by an observer on the basis of the reception of light signals. They often attribute the relativity of simultaneity to the difference in signal travel time for different observers. In this way, they reconcile statements of the relativity of simultaneity with a belief in absolute simultaneity and fail to confront the startling ideas of special relativity."

If the students understand that they are dealing with the geometry of Minkowski spacetime rather than the properties of light signals the problem is much easier. They simply draw orthogonal coordinates to represent a chosen "stationary" observer and superimpose on this the coordinates of the other reference frame with an appropriate lean on the time axis for time dilation and rise on the x axis for relativistic phase. Job done, its then obvious that Mt Rainier and Mt Hood erupt successively for one observer and simultaneously for the other. This is just a geometrical method of applying "the construct of a reference frame in determining whether or not two events are simultaneous".

Incidently, its not surprising that students "fail to confront the startling ideas of special relativity" when most lecturers fail to tell them what SR actually is (ie: the physics derived from the assumption of a Minkowskian (3+1)D universe). Dypteran 10:42, 10 October 2007 (UTC)

==> Yes, excellent point, but do see here. - DVdm 10:58, 10 October 2007 (UTC)

Dypteran - How nice. We are to tell people that "special relativity is the physics of Minkowski spacetime". So tell me, how do we tell a high school student what Minkowski spacetime is? As best I can tell, we have replaced the non-intuitive with the incomprehensible with this approach. Would I use the classical approach instead of the spacetime approach if I was teaching an SR course? No way! However, this is not a college-level course! Instead it is an encyclopedia article which by its own charter should be accessible to the lay public! IMO, you all can (and probably should) rewrite the main SR article to use the Minkowski spacetime approach (but please don't let it make Einstein look like some ancilliary character in the history of SR like this article did at one time). However, there is no way that I can see of presenting to a lay reader the meat of the issue with the Minkowski spacetime approach: Under it, you are assuming a knowledge base that the reader cannot and should not be assumed to have.

I am still working on this, but you may want to look at User:Ems57fcva/sandbox/Introduction to special relativity‎, which is where I am drafting a rewrite of this article. Note that the first thing that I do is to list the concepts that people need to be familiar with if they are to be able to deal with SR at all. For a college level course, I would assume this familiarity, but you can't do so here. I also am hoping to describe the primary effects of relativity theory without the use of math, but instead with illustrations. That does not mean that the article will not progress on to bring in the math, but the longer it holds off on doing so, the more people will follow it further. --EMS | Talk 15:09, 10 October 2007 (UTC)

The case is simple: SR is the physics of Minkowski space, students taught in the old way dont get it (66% of undergrads dont get it), all modern textbooks for undergrads upwards treat SR as the physics of Minkowski space. Our task is to summarise the modern approach in language suitable for an encyclopedia article. This means avoiding all the stuff that EMS is packing into his revised article because it misleads the reader and simply telling SR as it is. I'm giving up now, I cant edit the article because all edits are reverted. Its up to the editors who occupy this article space to show academic integrity. Dypteran 09:15, 11 October 2007 (UTC)

Prerequisites

I think this is a fundamental issue that needs to be cleared before anything else. Wikipedia is not written solely for Americans. In most countries of the world, both algebra and geometry are compulsory for all students. For example, in India even if you drop math at the first chance, you would still have to learn Euclidean geometry in its entirety (including the Pythagoras's theorem, of course) and basic algebra of real numbers including solution of quadratic equations and systems of linear equations. Many (around half) would go on to learn topics such as complex algebra, matrices and determinants, real calculus (single and multi-variable), differential equations etc. In physics, studying Newton's laws of motion are compulsory too. All this is done in high-school. Assuming that this article is aimed no lower than 10th grade finishers, the level of presupposed physics and mathematics is not too much. Loom91 17:45, 10 October 2007 (UTC)

I can only be amazed at the level of both education and comprehension you want to assume here. This so-called introduction is so high-level that you almost need to know the subject to be able to follow it! Item: It calls that Lorentz transformations a "rotation". Until I edited the article just now, there was no statement that three of those "rotations" are manifested as changes in velocity! IMO, that really illustrates what is wrong here: This article is constantly assuming things that it should be stating. --EMS | Talk 04:02, 11 October 2007 (UTC)

Loom91 is a bit cutting about Americans but anyone of average or above average intelligence will have met Pythagoras' theorem at school. Pythagoras' is actually an empirical physical theory (all "proofs" actually assume the theory) that is only an approximation. Minkowski pointed out that the true theory needs another dimension. This is the fundamental content of SR, it cannot be reduced further. The previous introduction due to Geometer explained this in simple terms without introducing excess baggage http://en.wikipedia.org/w/index.php?title=Introduction_to_special_relativity&oldid=161994469 . Dypteran 09:09, 11 October 2007 (UTC)

Honestly, you people don't have the first clue on how to make complex physics accessible to the public. You think you know better than all the physcis teachers and all the physics writers over the past 100 years. Yes, many university students don't understand SR. But here's something you would also know if you had read physics education literature: many students also don't understand most of physics. Newton's Laws, for example. So you understand SR. Good for you. Now please go away and write an article for people like you (and me), and leave alone those of us who are trying to make it accessible. Knowing Phythagoras' theorem is almomst zero help in understanding invariant intervals. The difficulty in SR does not lie in the maths. The maths is trivial. The difficulty is in the counterintuitive, weird effects that are observed when objects travel close to c. Saying that "The case is simple: SR is the physics of Minkowski space" is unhelpful and arrogant. Timb66 11:54, 11 October 2007 (UTC)

Your continual reference to myself and others as purveyors of a completely new approach is absurd. Just read any modern introductory university text on SR. It is this approach that we are advocating. The role of an encyclopedia is to simplify this for the intelligent public, not to repeat historical approaches. This version http://en.wikipedia.org/w/index.php?title=Introduction_to_special_relativity&oldid=161994469 is not extravagantly complex. I notice that although you have demanded documentary proof from myself and others, you have offered no proof that a description of SR as a reprise of evidence for why a theory such as SR is required is any better. Incidently, it has been pointed out that relativistic frames of reference should be introduced after the relativity of simultaneity because the reason why they are defined is the clock problem, it has been pointed out that special relativity cannot be defined as the "evidence" for SR (or the failure of Newtonian physics), it has been pointed out that 66% of undergrads (95%(?) of lay people) dont get SR using the electrodynamics approach but you have not answered any of these points and just say bugger off and EMS, DVdm and Loom91 just revert edits. Now, of course I will leave this article to you - if 95% plus of Wikipedians dont understand SR my view doesn't stand a chance and those who guard these articles just revert any changes. Its pointless staying but when there was a perfectly good introduction in place it seems tragic that it is being changed to a pedestrian repeat of past mistakes. Dypteran 13:17, 11 October 2007 (UTC)

We are not calling your approach new. We are calling it inappropriate, and for the purposes of Wikipedia useless. Your lead would make a wonderful openning for a textbook. Wikipedia is not a collection of textbooks. That is what wikibooks is for. Wikipedia is an encyclopedia.

I rewrote the lead to tell the reader in a nutshell what special relativity is. See WP:LEAD, which says amongst other things that the lead should be able to stand alone as an overview of the subject. The lead in your prefered version cannot stand alone as it is constantly refereing to other articles and even the body of the article itself. It is even misleading as it treat SR as being more the work of Minkowski and Noether than that of Einstein. It also is assuming a familiarity with concepts such as "spacetime" and "invaiance" that this article should be introducing!

As for the body of the article: It just dives into a bunch of highly technical material without even attempting to put it into a context for an introductory reader. You say that "Minkowski pointed out that the true theory needs another dimension. This is the fundamental content of SR, it cannot be reduced further." I have news for you: I am not trying to reduce it further. Instead I am trying to give the reader a context for understanding it in the first place! The questions to ask here is "what does the reader need to know?" and "How can I create a coherent description of this material for someone who lacks my training"? Those of you who are hyping the Minkowski apprach are not even trying to answer those questions. --EMS | Talk 15:35, 11 October 2007 (UTC)

Please read the article carefully before charging in with your claims. "there was no statement that three of those "rotations" are manifested as changes in velocity" - this is clearly untrue. It was specifically mentioned that Lorentz transformations correspond to transformations of reference frame. Loom91 18:35, 11 October 2007 (UTC)

The article is fine, it introduces the subject with a concise sentence and has links for any items that are to be found elsewhere. It then explains the Lead in the text. I am speechless that EMS does not recognise Minkowski's contribution. I have a score of SR textbooks, including freebies, and all of these are centred on Minkowski's formalism. I cannot waste any more of my time on this issue. Dypteran 18:42, 11 October 2007 (UTC)

I've streamlined the lead, removing a lot of extraneous details present in both the competing versions. It now describes why SR is significant, and what the nature of the two formulations are. Any detailed discussions of the postulates of either formalism should be left to the article. I've also removed a ridiculous POV statement on the need to understand relativity of simultaneity. This is an encyclopedia, not a textbook. Loom91 18:56, 11 October 2007 (UTC)

In order to be able to explain my own original research to experienced relativists, I had to learn how to turn off my own knowledge on a topic and step back to look at how my writing would appear to someone coming at my work cold. I assume you all that I am well aware of Minkowski's contribution. However, when I turn off my knowledge of SR, I see in the old version a text that goes "MINKOWSKI! NEOTHER! INVARIANCE! PHYTHAOGEAM THEOREM! SPACE-TIME INTERVAL!", etc. If I was a novice on SR, I would drop that damned version like a hot potatoe before I was done with the first section!!! You have not introduced the concept of a rereference frame. You have not introduced the concept of a coordiante system. You have not introduced the concept of a coordinate transformation. You have not introduced the issue of how an observer measures space and time. You have not at all put the discussion of four dimensions into a real-world context. Even now, the text fails to explain to the reader where it is going and why. It just throws concepts at you one after the after the other. It's little wonder that the much of Talk:Introduction to special relativity/Archive 1, which covers over two years of discussion, is mostly composed of people complaining about how difficult to understand this article is!

I am putting together a rewrite at User:Ems57fcva/sandbox/Introduction to special relativity, and I think that it is time to start getting some comments on it. It is not at all the same and in fact is meant to show a reader who knows little math what relatvity is all about. There is no way to teach a novice relativity through Minkowski spacetime without introducing a large number of concepts that are alien to them. Instead, the classical appraoch is what will allow the reader to have the effects of relativity illustrated to them. --EMS | Talk 23:23, 11 October 2007 (UTC)

What you are actually suggestig is that SR be explained from a purely phenomenological perspective, with no reference to the actual theory. I don't think that's a good idea, because it does not help the reader understand. It just gives him a bag of very counter-intuitive facts. Being told that clocks tick at different rates for different people and moving rods get shorter without any background will alienate readers more than having to wade through some very basic math. Loom91 10:31, 12 October 2007 (UTC)

As best I can tell, this article is already doing a fine job of alienating people. Your math may be "basic" but the concepts are anything but basic, and there are many people around who are "allergic" to math but would love to know something about relativity theory. So a presentation of the phenomenology first with little reference to the math is IMO a very good idea. That is not to say that I want to leave out the math altogether, but I want to show the reader what this theory does, and then present the Lorentz transformations and say "Now look here: Each piece of these equations corresponds to one of the effects the we just discussed". Then even bring up Minkowski spacetime as the enabling geometry of SR.

If I was coming here with only a hazy knowledge of SR, I would want to know how the phenomenology arises. I would not need the math at first. Instead I would want to know the mechanism. Now to be complete, we need to present the math, but even so do be advised that this is article calls itself introduction to the theory. It needs only to present the theory to a novice reader, and give them an outline that will hopefully aid in later learning of the theory (if they should want to learn more afterwards). You cannot hope to truly teach this theory in a single article unless you truly believe that 10 pounds of you-know-what can fit into a 5-pound bag. --EMS | Talk 15:51, 12 October 2007 (UTC)

You say that you would want to know "how the phenomenology arises". But what you propose is discussing simply what the phenomenology is, postponing discussions of how it arises. This is like putting the cart before the horse, not a sound logical course. There is already brief discussions of the phenomenology in the lead, more detailed discussion will be of little use unless the theoretical machinery is introduced first. However I'm willing to see if you can make such an approach work. But I'm definitely opposed to introducing the LT before Minkowski space.Loom91 09:58, 14 October 2007 (UTC)

I am looking to have this be a well-laid-out and informative article. You can declare to your heart's content how soundly logical it is, but for a novice on relativity, this article is all bur unreadable! Presenting the facts in what to you is the "right order" is no good if the intended audience cannot follow the narrative. The goal here is to inform the reader, not to show how smart we are. --EMS | Talk 16:04, 14 October 2007 (UTC)

Invariance of length: the Euclidean picture

Why not start in one dimension and explain that in two dimensions you need Pythagoras' theorem to calculate the length? I think that's much easier to follow for lay people who do know about Pythagoras' theorem.

About the article in general: The current approach could be in principle better than the historic approach, however, things are not explained well enough yet. That's why I voted for Type 1, because that version is a better introduction. Count Iblis 20:14, 11 October 2007 (UTC)

Frankly, I don't think a reader who doesn't know a basic thing like Pythagoras's theorem will be able to understand SR, no matter how it is presented. You may tell him that "A moving rod shortens" and he will say "well, if you say so". He will never really believe it. Loom91 10:09, 12 October 2007 (UTC)

I agree but even if we focus on readers who are familiar with Pythagoras, we still have to be careful with how we present things here. For most of us it wouldn't realy matter that much and we are inclined to choose the way it looks best to us. Now, what I've learned during my teaching experience is that it is far more effective to explain the concept by using things they already know as an example.

So, I would suggest that instead of first explaining how to generalize Pythagoras to 3 dimensions, we simply say that a rod of a certain length in two dimensions that is not alligned with the x-axis will seem to have a shorter length if you only look at the x-axis and that the full length must be computed using Pythagoras and that the generalization to higher dimensions works in a similar way.

You can't reason like: "People already know about Pythagoras, so we'll go straight to the things they don't know". Then every sentence contains a new concept and the article becomes unreadable. No teachers teach like that, no physicists give presentations at conferences like that. You always stay firmly into the territory the audience is familiar with and peek into the new territory from there. Count Iblis 13:35, 12 October 2007 (UTC)

So what you are basically saying is that instead of starting with how to move from 2 to 3 dimensions, we start with how to move from 1 to 2 dimensions. I've no problem with that. Loom91 14:24, 12 October 2007 (UTC)

Loom91's edits to the lead

Overall, I like them. They are moving the process of refining this article forward. My one disagreement is in the removal of

The relativity of simultaneity is one of the hardest aspects of special relativity to grasp, but it is an essential element of this theory: Without it, many of the other predictions of special relativity cannot be part of a self-consistent theory.

I personally see this as a highly important fact. Many of the misunderstandings involving relativity are centered on a refusal to accept the relativity of simultaneity. Indeed, most popular introductions prefer to sweep it under the rug rather than attack it head-on. Obviously, my preference is to red-flag it up front.

I have heard that defense lawyers will as a rule make the case for a lightet sentence during the verdict part of a death-penalty case so that when they get to the penalty part of the case (if they do), the jury will already have some familiarity with the issues that those lawyers want them to consider. Similarly, I feel that saying up front that the relativity of simultaneity is important will cause the reader to pay more attention to that material when he or she gets to it rather than just shrugging it off as something difficult and moving on. --EMS | Talk 00:15, 12 October 2007 (UTC)

I also think the lead is much improved. I have tweaked it further, adding a flag that SR effects become apparent at speeds close to c. Timb66 09:16, 12 October 2007 (UTC)

EMS: when we are writing an article it would not be reasonable to consider the case that the reader simply does not believe us. We have stated what RoS is, and if the reader refuses to believe that, there's little we can or should do. This is not a textbook.

Timb66: the counter-intuitiveness of SR is not limited to high velocities. That time may go at different rates for two persons, even very slightly different, is itself counter-intuitive. Also, talking about velocities close to c immediately begs the question "velocity of what?". Such questions are better avoided in the lead, which should be concise. Loom91 10:19, 12 October 2007 (UTC)

The reason SR was not discovered before Einstein is because the observable effects only become apparent when things move fast. This is a crucial point and should appear in the lead. Timb66 11:49, 12 October 2007 (UTC)

What is important to note is that relativistic corrections are typicaly of order (v/c)^2 and not (v/c). The fractional deviation of some prediced effect using classical mechanics of an object moving at 30 km/s (think of an asteroid or planet) is not of order 10^(-4), which would have been detectable to 18-th century astronomers, but it is of order 10^(-8). Count Iblis 13:49, 12 October 2007 (UTC)

It still begs the question "the velocity of what?". Also, words like 'usually' are not very meaningful without further context. Loom91 14:29, 12 October 2007 (UTC)

First of all to Timb66: I must agree with Loom91 that the effects of relativity are present at all speeds even if they are totally miniscule at everyday speeds and accuracies of measurement. Please consider that we need to choose our battles in the lead. We have a whole article in which to discuss the details of relativity (or at least the significant ones). Even with my desire to preach on the significance of the relativity of simultaneity in the lead, I also realize that the lead is almost a big as it can currently stand to be.

To Loom91: There is not too much that I think that we can do about the reader who refuses to believe. Certainly anyone who has made up their mind that SR is a bunch of crock is a lost cause. My concern is about the people who come here with little or no knowledge of relativity. As Ms. Scherr's thesis shows, the expectation of absolute simultaneity is so ingrained in most people that they don't even know they are assuming it. I know that even with my idea of red-flagging it that many people will still walk away without "getting it", and to be honest with you the current section on the relativity of simultaneity is so technical that an introductory reader has little hope of figuring it out from that text. Unfortunately, the current relativity of simultaneity article not much better, but a couple of aniamted GIFs illustrating the thought experiment in that article would help tremendously. I assure you that the relativity of simultaneity is a major stumbling block to figuring out relativity, and it is going to be there no matter how one chooses to present this theory. --EMS | Talk 15:18, 12 October 2007 (UTC)

Loom91, by not being extremely rigorous right from the start you can actually gain a lot by making the look article much more interesting to lay people. E.g. by saying that relativistic corrections are of order (v/c)^2 you can already point out that the kinetic energy formula of classical mechanics is just the relativistic correction to the rest energy E = m c^2 in the introduction. Most people know about the formula E = m c^2, they know about the kinetic energy formula 1/2 m v^2, so we are just explaining how relativity connects the things they know about without going into the details. Count Iblis 15:44, 12 October 2007 (UTC)

Suggested compromise

Concerning the article as a whole, I have a suggestion: take the preferred "Minkowski" version (which I think we all agree is a good article for those with a background in maths and physics) and rename it as a new article with the title "Special Relativity as Flat Minkowski Spacetime", or similar. That would leave Intro to SR to be something accessible to the layperson, with links to the new article. Timb66 09:16, 12 October 2007 (UTC)

The current article does not need a background in math and physics beyond what is provided in a compulsory high-school education (in almost all European and Asian countries, at least). All new concepts used are thoroughly explained so that the article stays accessible to laymen, and ways in which it could be made more accessible are always under discussion.

Besides, seeing that many WP editors are opposed to even one introductory article, having two will cause an uproar! Loom91 10:26, 12 October 2007 (UTC)

The point is that the current article is not an introduction. It is a very good description of "Special Relativity as Flat Minkowski Spacetime". And when I say a background in maths and physics is required, I mean a particular way of thinking that comes with that training. I know that every educated person know's Pythagoras' theorem. That is not the difficult part. The hard thing for a layperson is to grasp the concepts (geometry of spacetime, relativity of simultaneity, etc.). Timb66 11:53, 12 October 2007 (UTC)

What you mean is that the article requires the reader to actually think about what he's reading, instead of letting it wash over him. Well, that's the way physics is. Loom91 14:27, 12 October 2007 (UTC)

:-( I must admit that I am not impressed by the idea that physics should be hard to grasp. I will admit that SR is not an easy theory to deal with in any case, but that is not an excuse for saying "I am going to require you to be able to understand a very advanced concept because you would need to do so in a college level course for physics majors". Wikipedia is not a university. It is our job to come to the reader, not for the reader to come to us. We cannot "dumb down" the presentation so much that an idiot could understand it because all that would be left is a poor caricature of SR, but all the same we should not expect the readers of this article to have graduated from high school with A's in math and science either. --EMS | Talk 16:02, 12 October 2007 (UTC)

I believe that the concepts presented in this article can be understood by any reasonably interested layman if he is guided carefully and the points are explained thoroughly. The fundamental concept is that the Minkowski metric is invariant, not the length. Everything following that is basic algebra. It's this point that needs to be put across carefully and intuitively. Thus the attempt to introduce invariance of length and then proceed to invariance of intervals. Loom91 09:53, 14 October 2007 (UTC)

I see neither careful guidance or thorough explanation being given in this article, and most especially not in the earlier version which we keep citing above. I also find your demand that people know and love algebra to be especially arrogant. You act like the phenomenology is of secondary importance, when for many reader that is what they want to know about. Even now, this article gives that reader relatively little real-word context before throwing Minkowski spacetime at them full-blown. I have tried to soften the rough edges by adding a paragraph explaining why geometry is being covered at all, but I still feel that this article throws the reader to the wolves rather than offering them a thoughtful, readable, and educating article. --EMS | Talk 15:51, 14 October 2007 (UTC)

Wording on accuracy

Timb66 -

I do not think too much of this edit. First of all, I do not see it as being totally true. One example of a strongly sub-luminal prediction of SR is that of magnetism. More importantly, I do not see that as a statement that needs to be made in the lead. If anything, it mutes the message of experimental verificaion rather than explaining it: It makes it sound like special circumstances are needed to achieve confirmation rather that makng note of the correspondence which exists between SR and Newtonian physics at low speeds. --EMS | Talk 13:47, 17 October 2007 (UTC)

I concur. This detail, which is confusing unless explained in more detail, is not necessary iin the lead. Loom91 21:07, 17 October 2007 (UTC)

Sorry, but I don't think it is confusing at all. The weird effects of SR are not apparent in everyday life, which explains why people find it counter-intuitive and why it took so long for the theory to be discovered. What is confusing about that? I think it helps understanding to know these facts. Timb66 07:43, 20 October 2007 (UTC)

Sorry that I have not responded sooner, but I have been on vacation and had limited internet access.

Timb66 - You are not saying what you think you are saying. If you want to note that SR closely corresponds to Newtonian physics, then you should do just plain do so. Putting that statement in the sentence on testing makes it sound like the testing of relativity is limited to high speed and exreme accuracy situations. As I said before, that is not true. --EMS | Talk 17:27, 26 October 2007 (UTC)

I am trying to convey the fact that the counter-intuitive predictions of SR (time dilation and length contraction, which many people will have heard about) are only measurable if the objects involved are moving at a substantial fraction of c. Timb66 11:02, 27 October 2007 (UTC)

That is a seperate fact IMO. It is usually inconveient (at best) to send out two different messages in one sentence, and often such an attempt garbles both messages. In any case, I have done an edit which I hope you will find acceptable. --EMS | Talk 12:44, 27 October 2007 (UTC)

Yes, looks fine to me. Thanks. Thanks for helping to make the lead accessible to the general public. A shame that the bulk of the article is not, but I can't see how to overcome the dogmatism that has been expressed here. Timb66 14:57, 27 October 2007 (UTC)

I'm working on a rewrite in my own space, and will try to get back to it soon. Once it is done I will propose it as a replacement for the current version, and try to bring in other interested editors on this issue. It will be a fight, but I think it is one that can be won. However, the first thing to do is to create a well-written article which is to put in this one's place: As bad as the current article is, it still is easy to do even worse. As for the "dogma" itself: I actually agree with it, but don't see the spacetime concept as being an acceptable way of telling the general public what SR is. OTOH, it could be the basis of a rewrite of the main SR article. --EMS | Talk 02:21, 29 October 2007 (UTC)

Comment on this discussion

WOw, high powered discussion. you guys are getting it right so far. Four dimensional spacetime is the truth about SR, the rest is just how you get the truth. Also anyone can do Pythagoras. —Preceding unsigned comment added by 200.69.255.114 (talk) 15:44, 25 October 2007 (UTC)

Reference frames and Galilean relativity: a classical prelude: tea slanted in a spaceship

The Article says:

"For example, if an astronaut moving in free space saw that the tea in his tea-cup was slanted rather than horizontal, he would be able to infer that his spaceship was accelerated."

If the tea was horizontal, wouldn't it imply that the space ship is accelerating upwards, since otherwise the tea would diffuse out of the cup? Ummonk (talk) 19:13, 1 February 2008 (UTC)

We are not considering statistical phenomena here. Loom91 (talk) 17:44, 2 February 2008 (UTC)

The point is that in free space there's no gravity, so putting the tea into the cup and then keeping it there would be non-trivial. If the tea is being held at the bottom of the cup, then it's not an inertial reference frame as either there's an acceleration or there's gravity. DAG (talk) 04:10, 3 February 2008 (UTC)

Yes, a teacup on a spaceship is a silly idea! I have changed it to be on a train. Timb66 (talk) 10:15, 4 February 2008 (UTC)

Help with formula derivation

Let the object move with velocity v when observed from a different reference frame. A change in reference frame corresponds to a rotation in M. Since the spacetime interval must be conserved under rotation, the spacetime interval must be the same in all reference frames. In proposition 1 we showed it to be zero in one reference frame, hence it must be zero in all other reference frames. We get that

$(vt)^{2}-(ct)^{2}=0\,$

Why is this? I cannot see where this is derived from – I understand the rest of that section perfectly, but struggle to justify that : $(vt)^{2}-(ct)^{2}=0\,$. 81.155.125.119 (talk) 21:24, 7 February 2008 (UTC)

This comes from the definition of the space-time interval in special-relativity:

$s^{2}=x^{2}+y^{2}+z^{2}-c^{2}t^{2}$

The value of $s^{2}$ is invariant between all inertial frames. That is $s^{2}$ will be the same no matter which inertial observer measures it. So, x, y, z, and t can change, but $s^{2}$ can't. So, if $s^{2}=0$ for one observer, it's zero for all inertial observers. And as for one observer:

$v^{2}t^{2}-c^{2}t^{2}=0$

This has to be true, then, for all observers. This has to be true no matter what t is. Thus the speed must be the speed of light for all observers.

There are some subtleties to this which are glossed over, but that's the main idea. DAG (talk) 00:46, 8 February 2008 (UTC)

Because v=c. Loom91 (talk) 20:15, 8 February 2008 (UTC)

No, that's not what I meant Loom91: I get that $|v|=c$ because $v^{2}t^{2}-c^{2}t^{2}=0$, but saying that $v^{2}t^{2}-c^{2}t^{2}=0$ because v=c is not justification, it is the outcome. It is OK, I understand this now, my mistake was that I read that v was the velocity of the second reference from relative to the first. Now I know it is the speed of the object I can understand where the said formula is derived. Thanks anyway – sometimes talking about something makes one realise the answer for oneself. =) 81.155.125.119 (talk) 20:46, 8 February 2008 (UTC)