Talk:Introduction to special relativity/Archive 3

message: This article has changed from a short tutorial in how SR is the physics of Minkowski space see http://en.wikipedia.org/w/index.php?title=Introduction_to_special_relativity&oldid=144699477 to a full competitor with the main article.  The main article is pretty good. Dypteran 16:35, 30 September 2007 (UTC)
replies: text: These sort of suggestions have been tried countless times in the past and have always been stricken down without exception. Recently the seal of community approval was reinforced by the featuring of Introduction to general relativity. This merge proposal doesn't have a snowball's chance in hell to succeed. Loom91 17:55, 30 September 2007 (UTC)
replies: text: The introduction to general relativity is different because the main article is far more complicated than special relativity.  The people who have edited special relativity have made it fairly simple.  What has happened in this case is that the introduction has been expanded recently by Loom91 to copy the main article. This is a pointless exercise and damages Wikipedia. Dypteran 14:35, 1 October 2007 (UTC)

text: Hmmm, I don't see much of a difference between the old and new versions. What we should do is write this article so that an interested lay person (e.g. a high school student) who knows nothing about special relativity can understand the basics so that he/she can more easily understand the main article.  Count Iblis 17:53, 30 September 2007 (UTC)
replies: text:  I think the current article can be understood by the interested high-school student. Loom91 17:55, 30 September 2007 (UTC)
replies: text: I agree, however, I do think that more results must be derived in this article. One can also write new wiki articles for this purpose and link those from this article to make room for that. E.g. a derivation of the Lorentz transformation using light signals, a derivation of the relativistic formulae for energy and momentum by considering collisions, etc. etc. All of this is high school level stuff... Count Iblis 18:06, 30 September 2007 (UTC)
replies: text: Surely an intro is a preamble to the main text rather than an amplification of it. Also, using light rays distracts the reader from the idea that SR is the physics of spacetime. Dypteran 14:35, 1 October 2007 (UTC)

text:  Since wikipedia is an encyclopedia and not a textbook, we do not include derivations or proofs unless they are particularly interesting, important or othewise of wide interest. As a general rule, we seek to describe rather than analyse. Loom91 18:18, 30 September 2007 (UTC)
replies: text:  Um, I *do* see two propositions complete with proof in the part that you restored earlier today. You might so some rewriting there ;-) - DVdm 20:32, 30 September 2007 (UTC)
replies: text:  Note the particularly interesting escape clause. Loom91 07:19, 1 October 2007 (UTC)

text: *I would vote for option (2). Dypteran 14:35, 1 October 2007 (UTC)

text: *Definitely vote for option (3). "An Introduction to" does not really belong in an encyclopedia. It can only cause redundancy and inconsistency, specially in a Wiki-environment with an unlimited number of authors and views. It is bound to confuse the casual and lay-reader. DVdm 17:10, 1 October 2007 (UTC)

text: * I find this list of choices to be very POV to me.  For option (1), I do not see this version as being a rehash.  Instead, the new section which is delving into reference frames and the relationship of SR and Newtonian mechanics is a very important way to introduce SR, and should be retained.  For option (2), I never saw that earlier version as being at all an introductory text.  Instead it was throwing relativiy novices to the wolves by immediately introducing a very advanced concept and rehashing the main points of the main article using that advanced mathematics.  Option (3) is not POV, but I do feel that this would clutter up the main article.This article should be mostly in plain English and introducing the issues which distinguish SR from Newtonian physics.  This is not the say that the concept of Minkowski space cannot be used here, but it must be part of a primarily English-based (instead of a primarily mathematically-based) article. --EMS | Talk 18:52, 1 October 2007 (UTC)
replies: text: Yes, there are two problems. The first is that some editors see SR as the physics of Minkowski spacetime. I am one of these.  I do not regard this as a POV but mainstream modern thought on the matter.  The trouble is that by 1909 Einstein was under heavy attack for the ontological basis of his theory. The "speed of light" is a compound constant (length/time) and the assumption that physical laws should be the same between reference frames is just an edict, not a self evident truth (the action is not invariant during Galilean transformations).  As Weyl pointed out, it was Minkowski who gave SR a respectable ontology. The original article uses the same level of maths as the article on the Pythagorean theorem. The main special relativity article is actually quite simple but doesnt explain Minkowski space.  Robinhw 08:47, 2 October 2007 (UTC)
replies: text:  The idea that Minkowski space is "easy" or "introductory" is what is getting to me.  It is not.  It requires a sense of space and an ability to read mathematical expressions that I have found to be less than natural.  As a result, Minkowski space makes for a lousy introduction to SR on its own.  IMO, the issue to be dealt with here is one of how does SR differ from Newtonian physics?  You need to first lay out the basics of what Newtonian physics is and how it was modified in SR.  Then you can bring in Minkowski spacetime as the paradigm that underlies SR, but to be honest with you the Lorentz Transformations are also needed. --EMS | Talk 16:46, 2 October 2007 (UTC)
replies: text: This sense of the role of space in physics is special relativity. If people don't understand it they don't understand SR.  The LT's are just a combination of gamma*time and gamma*phase, explain time dilation and phase and you have the LTs. The LT is not fundamental nowadays, it is the metric that is fundamental. Robinhw 09:21, 3 October 2007 (UTC)
replies: text: V good, thanks. Geometer 10:32, 3 October 2007 (UTC)

text: Robinw, I have seen quite some books on relativity, but never seen one where it is stated that "The LT's are just a combination of gamma*time and gamma*phase". Can you give a few relevant references for that? DVdm 11:09, 3 October 2007 (UTC)

text: * BTW I would vote for (2) but I am easy about (3). It is crucial to explain from the outset that SR is not an adjustment to Euclidean ideas or students will get the whole thing wrong. Robinhw 11:29, 2 October 2007 (UTC)

text: The debate here is about what should go in an introductory article. The approval of this type of article in Wikipedia is not an approval for introductory articles that duplicate the main text, so, yes, there is a need for debate.  Have your changes duplicated the main article? Does the main article explain the points that you duplicated (frames of reference, Lorentz transformations, Galilean vs Einstein relativity as clearly? That is the issue. I think the main text is clear and simple on these matters and does not need duplicating here. In the same way as EMS says that things in the intro would "clutter up" the main article I believe that these duplications clutter up the intro. Robinhw 09:21, 3 October 2007 (UTC)
thread_title: Merger

message: The current intro is a mistake. The ontology of modern SR is clear.  The universe is a Minkowski space with the conservation laws of physics dependent upon the symmetries of this space.  In other words SR is the physics of Minkowski space. The evidence for relativity depends on MMX, Einstein's work on electrodynamics etc.  
Count Iblis, Robinhw, Geometer and myself understand this distinction.
: ==> I'm not sure about Geometer (thinking that physics is just a branch of mathematics: "It is sufficient to understand Pythagoras' theorem to understand SR"), and I'm not sure about you ("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" remember?), but apart from that, most us understand the distinction pretty well. Straw man - DVdm 17:06, 6 October 2007 (UTC)
replies: text: ==> I have no problem with accepting the modern theory. No one here has that problem. Another Straw man - DVdm 17:06, 6 October 2007 (UTC)

text: ==> You are consistently over-making your point. You are also consistently over-forgetting that you are on the talk page of an introduction to a subject, targeted at a lay public. The quotes and references you give are excellent.  Carrol's book is superb, but alas, it is on a different subject and targeted at an entirely different public. You can safely stop embarrassing yourself now. Try to concentrate on improving the Minkowski spacetime article - see you there. DVdm 16:16, 6 October 2007 (UTC)
replies: text:  I will second these comments.  To be blunt about it, the main special relativity article is in need of a good rewrite: That article currently is a hodge-podge of all sorts of contributions that have never been put into a coherent, well through-out whole.  Perhaps it could start out with a breif introduction to Minkowski spacetime.  At the least, that would be a much better place for you to apply your insight, as that is the one that is intended to be the technically accurate article.   Even so, I also remind you that the Minkowski spacetime material does appear in wikibooks:special relativity, where I have no quibble with its presense; and that Ms. Scherr's thesis did not conclude that the use of Miknowski spacetime is the best way to teach students the fundamentals of SR. --EMS | Talk 03:31, 7 October 2007 (UTC)
thread_title: Confusing ontology with evidence

message: Nearly all twentieth century and twenty first century physics textbooks describe special relativity as the physics of flat, Minkowski spacetime. 
Einstein(1916):"It appears therefore more natural to think of physical reality as a four dimensional existence, instead of, as hitherto, the evolution of a three dimensional existence."
Roger Penrose (1998):
"The idea that the history of the universe should be viewed, physically, as a four-dimensional space-time, rather than as a three dimensional space evolving with time is indeed fundamental to modern physics."
Hermann Weyl(1918):"The adequate mathematical formulation of Einstein's discovery was first given by Minkowski: to him we are indebted for the idea of four dimensional world-geometry, on which we based our argument from the outset."
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."
Dypteran 14:57, 6 October 2007 (UTC)
replies: text: ==> You are consistently over-making your point. You are also consistently over-forgetting that you are on the talk page of an introduction to a subject, targeted at a lay public. The quotes and references you give are excellent.  Carrol's book is superb, but alas, it is on a different subject and targeted at an entirely different public. You can safely stop embarrassing yourself now. Try to concentrate on improving the Minkowski spacetime article - see you there. DVdm 16:16, 6 October 2007 (UTC)
replies: text:  I will second these comments.  To be blunt about it, the main special relativity article is in need of a good rewrite: That article currently is a hodge-podge of all sorts of contributions that have never been put into a coherent, well through-out whole.  Perhaps it could start out with a breif introduction to Minkowski spacetime.  At the least, that would be a much better place for you to apply your insight, as that is the one that is intended to be the technically accurate article.   Even so, I also remind you that the Minkowski spacetime material does appear in wikibooks:special relativity, where I have no quibble with its presense; and that Ms. Scherr's thesis did not conclude that the use of Miknowski spacetime is the best way to teach students the fundamentals of SR. --EMS | Talk 03:31, 7 October 2007 (UTC)
thread_title: Special relativity is the physics of Minkowski spacetime

message: Timb66 wrote that the second postulate is:
:... that the speed of light in vacuum [as] measured by an observer does not depend on the motion of the light source.
This is not a correct statement, and in fact when combined with Newtonian physics that statement is the basis of luminiferous aether theory.  A look at Einstein's initial SR article shows that he first presented the second postulate as being
:light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body.
So as stated by Einstein, both the fact that the speed of light is c and the fact that this speed is independent of the motion of the source are stated.  IMO, the constancy/invariance of c is the real issue here.  I have tried to create wording now that reflects this invariance (stating that the speed of light is the same for all inertial onbservers).  Hopefully that will prove to be a good/consensus way of representing the second postulate. --EMS | Talk 03:57, 7 October 2007 (UTC)
replies: text: I noticed that both you and Timb66 first had reinserted and then later removed the phrase "which is now defined as being 299,792,458 m/s". I think that this indeed should only be mentioned after a statement about the universally successfull testing of the theory, which is what I have done. DVdm 09:36, 7 October 2007 (UTC)
replies: text:  I concluded that the exact speed was superfluous in that context, and gather the Timb66 agrees.  I like the purpose of your edit, but did amend it somewhat. --EMS | Talk 16:07, 7 October 2007 (UTC)
thread_title:  The second postulate 

message: Perhaps adding this sentence to the end of the first paragraph of the lead may help things a bit:
: In special relativity, space and time are treated as being the interchageable aspects of a 4-dimensional continuum called Minkowski spacetime.
I worry that even this may be a bit too advanced for some readers.  OTOH, it does drop some good hints as to the real nature of SR.  Also, if a reader is enough "behind the 8-ball" when they come here they won't get much out of the rest of this intro anyway, in which case the extra text doesn't hurt things.  Comments or suggestions, anyone? --EMS | Talk 04:12, 7 October 2007 (UTC)
replies: text: I would rather keep that as an 8-ball opening line for the section The Minkowski formulation: introduction of spacetime. DVdm 09:44, 7 October 2007 (UTC)
replies: text:  Good enough.  I ended up doing this edit which I think makes a similar but much more accessible point.  At the least, the first paragraph needed to say something about the physical nature of SR, is essense turning it into the lead for the lead. --EMS | Talk 16:11, 7 October 2007 (UTC)
thread_title:  Suggestion for an extra sentence 

message: That section needs a bit more than merely mentioning GPS, which is an application of general relavity. At best special relativity can be used as a mere approximation for the calculation of a merely partial effect
Does anyone have references for the usage of relativistic equations in the design of cathode ray tubes? I'm sure I've seen it mentioned a few times but can't remember where. I've added this to the section with a  tag. - DVdm 12:07, 7 October 2007 (UTC)
thread_title:  Applications of special relativity