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	Special relativity was one of the Natural sciences good articles, but it has been removed from the list. There are suggestions below for improving the article to meet the good article criteria. Once these issues have been addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake.
Article milestones Date Process Result December 16, 2004 Featured article candidate Not promoted January 1, 2005 Good article nominee Listed February 12, 2006 Featured article candidate Not promoted October 30, 2006 Good article reassessment Kept August 26, 2009 Good article reassessment Delisted Current status: Delisted good article

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Edit request: lede is factually wrong.

The lead contains the following false claim:"As of today, special relativity is the most accurate model of motion at any speed." It should be obvious that for macroscopic motion (that is, where.when quantum mechanics isn't needed) that GENERAL relativity is the "most accurate model of motion" (at all possible speeds).71.29.172.222 (talk) 15:39, 3 July 2016 (UTC)

 Not done. Special relativity can handle all possible speeds—see the article: "The theory is "special" in that it only applies in the special case where the curvature of spacetime due to gravity is negligible. In order to include gravity, Einstein formulated general relativity in 1915. Special relativity, contrary to some outdated descriptions, is capable of handling accelerated frames of reference."

References

1. Koks, Don (2006). Explorations in Mathematical Physics: The Concepts Behind an Elegant Language (illustrated ed.). Springer Science & Business Media. p. 234. ISBN 978-0-387-32793-8. Extract of page 234
2. Steane, Andrew M. (2012). Relativity Made Relatively Easy (illustrated ed.). OUP Oxford. p. 226. ISBN 978-0-19-966286-9. Extract of page 226

- DVdm (talk) 18:07, 3 July 2016 (UTC)

• I agree that it is factually wrong. For example, the motion of a very heavy body in the neighbourhood of another very heavy body is not correctly predicted by special relativity, whereas it is correctly predicted by general relativity. An example would be two neutron stars. Hence special relativity is less accurate than general relativity in this case, meaning that special relativity is not the most accurate model of motion. The text could be changed to "special relativity is the most accurate model of motion at any speed when gravitational effects are negligible". I don't think the statement by DVdm addresses this issue. Ian Hinder (talk) 12:42, 20 May 2017 (UTC)

No problem with that: . My objection was to the wording of the request. - DVdm (talk) 13:15, 20 May 2017 (UTC)

Wrong answer in the section "How far can one travel from the Earth?"?

I got ${\displaystyle v\approx 0.72c}$, not ${\displaystyle v=0.77c}$, given this equation and these variables ${\displaystyle v(t)={\frac {at}{\sqrt {1+{\frac {a^{2}t^{2}}{c^{2}}}}}},\quad a=9.81\,\mathrm {m} /\mathrm {s} ^{2},\quad t=3.1536\,10^{7}\,\mathrm {s} }$. Am I missing something? Anyone else got the same result?

Ximalas (talk) 20:40, 21 February 2018 (UTC)

Yep. Feel free to change. This kind of thing should have a good source. - DVdm (talk) 21:11, 21 February 2018 (UTC)

Thought experiments

In his popular and semi-popular writings, Einstein was well-known for illustrating basic concepts of relativity with the aid of thought experiments.

Am I simply missing it, or does there not exist an article in Misplaced Pages devoted to "Special relativity thought experiments"?

Would creation of such an article be desirable? Or would such an article violate wp:NOTTEXTBOOK?

Prokaryotic Caspase Homolog (talk) 03:24, 5 April 2018 (UTC)

I think that it would be a good article to have, if it is framed as an article about the history of relativity and limited to sourced thought experiments devised by Einstein himself. JRSpriggs (talk) 04:24, 5 April 2018 (UTC)

Definitely it needs to be a sourced article. If we wish to make it an historical article strictly about Einstein's unique approach to conceptualizing complex scientific ideas, then the article name could be "Einstein's thought experiments", that would describe the ones that he devised not just for special relativity, but also ones that he devised for general relativity and for quantum mechanics. Prokaryotic Caspase Homolog (talk) 10:11, 5 April 2018 (UTC)

@JRSpriggs: I have created Einstein's thought experiments. I hope you find it decent. Prokaryotic Caspase Homolog (talk) 17:14, 28 April 2018 (UTC)

Yes, thank you. JRSpriggs (talk) 01:39, 29 April 2018 (UTC)

Measurement versus visual appearance

Triggered by recent edits ... While I have no (perceived) problem in the original, probably terse version of identifying the "measured shape" of an object as a collection of 3d-space-coordinates, obtained from a section of spacetime coordinates, and appropriately associated to corresponding object-inherent coordinates, revealing the length contraction in the direction of the velocity, I am unsure about the term "snapshot" in the current version. I think "snapshot" is "taking a picture", and induces inherently propagation of light, which is carefully excluded in "observing", i.e. taking spacetime coordinates.

I must admit that the notion of "visual appearance" is a bit bewildering to me in both versions. I think this is now about taking a "snapshot", which involves a central projection, including dependencies on distance between the object and the observer, the direction of the velocity, and what not.

I think that the presented material is excellent, but the presentation is not fully rigorous and sufficiently explicative, and I am unsure, whether the edits constitute an improvement. 12:29, 10 September 2018 (UTC)

Can you suggest a better wording? Now that you bring it up, I can see the problem that you might have with the word "snapshot" as a means of describing the "measured shape" of an object. Prokaryotic Caspase Homolog (talk) 02:14, 12 September 2018 (UTC)

I am sorry, but my reservations, and only sometimes direct suggestions for marginal improvements, are all I can provide. I am an intuition-less non-expert in STR, heavily suffering from the total collapse of the concept of rigid body in STR already in 1 dimension (rockets with string). Additionally, I disagree with certain adhered to concepts (necessity of talking about moving observers vs. light sources) claiming to be based on Einstein, and I do not feel adequately versed in the use of this non-native tongue, to express such delicate matters. Purgy (talk) 08:02, 12 September 2018 (UTC)

Hmmm... You bring up a variety of issues unrelated to your original concern. Born rigidity and Bell's spaceship paradox are not covered in the article as presently written, but one could argue that they need to be covered. One could also argue that coverage of those topics would represent unnecessary digressions, given the article's other deficiencies. The collective authorship paradigm that Misplaced Pages follows, while very good for developing articles in history, biography, etc. has not proven itself very well adapted to the development of technical articles like special relativity. In common with most other technical articles, the current article is a hodgepodge of parts with widely differing levels of difficulty. It needs a thorough overhaul by a person with a clear vision of how the article should be structured and what the target audience is supposed to be.

However, giving this article a thorough overhaul is beyond my competency. I can only focus on the little bits and pieces that I myself have added. The best that I can promise is that I'll continue to think about the points that you raised. Maybe somebody else will find a better wording. Prokaryotic Caspase Homolog (talk) 23:39, 12 September 2018 (UTC)

I really had no intention to bring up these topics as issues of this article (in need of covering), but only as prominent in causing me troubles in developing a good intuition about STR. I feel quite similar to the description of your last paragraph, just additionally handicapped by the necessity to use a non-native language.

Triggered by your remarks, I want to mention a thorough attempt -not too long ago- to deal with this article in the perspective you mentioned, which seems to have failed the target, but certainly has brought about significant improvements. BTW, I strongly object to the collective authorship paradigm being any good for questionable articles in history or biography. All the best, Purgy (talk) 07:13, 13 September 2018 (UTC)

This article? The last really major revamping that I recollect was the decision in mid-2015 to delete Introduction to special relativity as being an even worse hodgepodge than the main article. Prokaryotic Caspase Homolog (talk) 07:52, 14 September 2018 (UTC)

I am deeply concerned by me sloppily mixing up this article with Spacetime, which encountered heavy efforts of targeted improvement in 2017. My attention here was by far too focused on the "snapshooting" of "spacetime vectors", i.e., just on the local changes, being related to STR. Pardon! Purgy (talk) 09:36, 14 September 2018 (UTC)

The strength (and weakness!) of Spacetime as currently written was the principal editor's determination to adhere, as much as possible, to a purely geometric approach to presenting the material. There are neither trains nor lightning bolts in Spacetime. For the most part, the geometric demonstrations are logically presented, but by their very nature, the demonstrations are somewhat divorced from intuitive understanding. Most people, including myself, are rather more comfortable with a kinematic approach, i.e. with railway cars and spaceships. The problem is, how to add this introductory material? Most "Introduction to" articles get only a few percent of the readership of their associated main articles. Instead of trying to resurrect Introduction to special relativity (which needs to stay dead), I wonder if such material could be added as an extended introductory section to the current article? Against this idea would be the following objections:

1) Such material could very easily violate wp:NOTTEXTBOOK.

2) Such an introductory section could easily double the size of this article.

3) A featured wikibook exists on Special Relativity which has the merits of being principally authored by a single knowledgeable editor. It has a consistent presentation and relatively clear focus, and as a wikibook, it was allowed to take on textbook aspects. Despite this, I'm not very happy with it. Could somebody like myself do any better? Absolutely not.

Thoughts? Prokaryotic Caspase Homolog (talk) 15:17, 14 September 2018 (UTC)

... thinking ... Purgy (talk) 08:35, 15 September 2018 (UTC)

I take back part of what I said about the wikibook. I'm very unhappy with it. If you're going to write a textbook on special relativity, you need problems with solutions, or at least lots of example scenarios. Prokaryotic Caspase Homolog (talk) 11:10, 15 September 2018 (UTC)

To start with the result of my thinking: I have none. I agree on your verdict the wikibook not making me happy, I do not cling to the WP:NOTTEXTBOOK beyond not allowing for collections(!) of examples (paradigmata are a core necessity in WP! imho), yes, the danger of doubling the length is dangling, and finally, given my engagement and eruditeness on this matter, I am convinced I could not do half as good as you.

As an aside, I am very skeptical about the usual intuition on kinetics. All this rubbish about "moving observers" stems imho from "intuitively" "observing" TWO reference frames, thereby silently introducing a third frame, leaving the uninitiated confused.

Sorry, I think the best I can do, is commenting from the off sometimes. Please, do never assume any malevolence from my side. Purgy (talk) 07:36, 18 September 2018 (UTC)

Rearranging the sections, and now I'm stuck

I've been rearranging the sections of this article so as to put them into a more rational order, and now I'm stuck.

There are a variety of approaches to teaching relativity:

• The dominant approach found in most college textbooks is begin with the "two postulates" (almost always starting with a stronger, less intuitive form of the second postulate than that adopted by Einstein in his 1905 paper) and to proceed through relativity of simultaneity, time dilation, length contraction etc. to the Lorentz transformations. While traditional, this principle-based approach has many issues. As Miller has noted, "Teaching STR that way is especially problematic because, unlike the case of classical thermodynamics which is also taught as a principle theory, the two postulates or principles in the case of STR are strongly counterintuitive when taken together."
• Several textbooks begin with Minkowski spacetime as the central focus, often approaching Minkowski spacetime through constructive arguments. This, for instance, is the approach adopted by Taylor & Wheeler's Spacetime Physics. The article Spacetime attempts consistently to follow this approach, how successfully, I'm not sure.
• Some authors advocate beginning with the Lorentz transformations as the first principle. I know of no introductory college textbook that teaches special relativity this way.

This article starts off as if it were following a two-postulates presentation, and then suddenly switches over to presenting the Lorentz transformations as the first principle, from which everything else derives.

How should I go from here? Any suggestions? Prokaryotic Caspase Homolog (talk) 08:53, 28 October 2018 (UTC)

I think that I've managed a kludgy fix by adding some transitional commentary about different approaches to presenting special relativity. Prokaryotic Caspase Homolog (talk) 10:00, 28 October 2018 (UTC)

I personally am not happy with basing special relativity on the single postulate of universal Lorentz covariance, but that's the way the article appears to have been written. Prokaryotic Caspase Homolog (talk) 15:36, 28 October 2018 (UTC)

I need help here

Does this section really provide a comprehensible explanation of why FTL is impossible? All it does is state that "one can show" that causal paradoxes can be constructed. Prokaryotic Caspase Homolog (talk) 03:24, 29 October 2018 (UTC)

It makes sense to me. It explains how FTL travel would violate causality. There’s no proof of causality but it’s intuitively very appealing as without causality paradoxes arise, so is widely accepted as being true. And if you accept causality then FTL travel must be impossible.--JohnBlackburne_deeds 03:47, 29 October 2018 (UTC)

Causality and prohibition of motion faster than light

In diagram 2 the interval AB is 'time-like'; i.e., there is a frame of reference in which events A and B occur at the same location in space, separated only by occurring at different times. If A precedes B in that frame, then A precedes B in all frames. It is hypothetically possible for matter (or information) to travel from A to B, so there can be a causal relationship (with A the cause and B the effect).

The interval AC in the diagram is 'space-like'; i.e., there is a frame of reference in which events A and C occur simultaneously, separated only in space. There are also frames in which A precedes C (as shown) and frames in which C precedes A. If it were possible for a cause-and-effect relationship to exist between events A and C, then paradoxes of causality would result. For example, if A was the cause, and C the effect, then there would be frames of reference in which the effect preceded the cause. Although this in itself will not give rise to a paradox, one can show that faster than light signals can be sent back into one's own past. A causal paradox can then be constructed by sending the signal if and only if no signal was received previously.

Therefore, if causality is to be preserved, one of the consequences of special relativity is that no information signal or material object can travel faster than light in vacuum. However, some "things" can still move faster than light. For example, the location where the beam of a search light hits the bottom of a cloud can move faster than light when the search light is turned rapidly.

Even without considerations of causality, there are other strong reasons why faster-than-light travel is forbidden by special relativity. For example, if a constant force is applied to an object for a limitless amount of time, then integrating F = dp/dt gives a momentum that grows without bound, but this is simply because ${\displaystyle p=m\gamma v}$ approaches infinity as ${\displaystyle v}$ approaches c. To an observer who is not accelerating, it appears as though the object's inertia is increasing, so as to produce a smaller acceleration in response to the same force. This behavior is observed in particle accelerators, where each charged particle is accelerated by the electromagnetic force.

References

1. Tolman, Richard C. (1917). The Theory of the Relativity of Motion. Berkeley: University of California Press. p. 54.
2. Ginsburg, David (1989). Applications of Electrodynamics in Theoretical Physics and Astrophysics (illustrated ed.). CRC Press. p. 206. ISBN 978-2-88124-719-4. Extract of page 206
3. Wesley C. Salmon (2006). Four Decades of Scientific Explanation. University of Pittsburgh. p. 107. ISBN 978-0-8229-5926-7., Section 3.7 page 107

Primary sources

1. G. A. Benford; D. L. Book; W. A. Newcomb (1970). "The Tachyonic Antitelephone". Physical Review D. 2 (2): 263. Bibcode:1970PhRvD...2..263B. doi:10.1103/PhysRevD.2.263. {{cite journal}}: Unknown parameter |last-author-amp= ignored (|name-list-style= suggested) (help)

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