User talk:Stevenj/Archive 1

Hello and Welcome! I hope you like the place. --mav

Personal question
I have a question: how to request a block for somebody who contrubites abuses against me? Cautious 00:37, 29 Dec 2004 (UTC)

Older comments
Hi, I have a hard time understanding two of your additions to Quaternion and Pauli matrix:


 * In quantum mechanics, the 2x2 matrices that multiply b/c/d, times i, are called the Pauli matrices (plus the identity matrix for a). Moreover, this representation of a quaternion corresponding to a spatial rotation is equivalent to the rotation operator for spin-1/2 particles.

What do you mean when you say "this representation of a quaternion as a spatial rotation"? We didn't represent it as a spatial rotation, we represented it as a 2-by-2 complex matrix. I don't think you can represent quaternions as spatial rotations; the unit quaternions of course give rise to spactial rotations, but even this representation isn't faithful.


 * Together with the identity matrix I (which is sometimes written as &#963;0), the Pauli matrices form a basis for the set of 2 × 2 complex Hermitian matrices. This basis is equivalent to quaternion numbers, and when used as the basis for the spin-1/2 rotation operator it is the same as the corresponding quaternion rotation representation.

In which sense is this basis "equivalent" to quaternion numbers? What "quaternion rotation representation" are you referring to here?

Thanks, AxelBoldt 01:24 Apr 28, 2003 (UTC)

Hi Axel, part of the misunderstanding here is that you are misquoting me. I didn't say "this representation of a quaternion as a spatial rotation," I said "this representation of a quaternion corresponding to a spatial rotation." What I meant was basically the opposite of what you're thinking: I'm referring to the representation of a rotation by a quaternion, not the other way around. Less succinctly:

Suppose you take a rotation and represent it by a quaternion, which in turn is represented in the 2x2 matrix form. Alternatively, take the same rotation and represent it by the spin-1/2 rotation operator (a 2x2 matrix). The statement is that these two matrices are, in fact, the same. See also e.g. http://www.nyu.edu/classes/tuckerman/quant.mech/lectures/lecture_5/node4.html


 * slight correction: they are slightly different, corresponding to a 90-degree coordinate rotation x -> y, y -> -x. They are the same if you modify the 2x2 matrix formula in the quaternion page to use the Pauli matrix mapping described below.

I think that if you parse my original sentence carefully, the meaning is correct, but perhaps we should rephrase it to be more clear. =)

Regarding the equivalence of the quaternions and the Pauli matrices, I meant that if you take the quaternion a + bi + cj + dk, and map it to the matrix a * sigma_0 - b * i * sigma_1 - c * i * sigma_2 - d * i * sigma_3, you get an isomorphism. That is, you make the identification (1,i,j,k) <-> (sigma_0, -i sigma_1, -i sigma_2, -i sigma_3).


 * this representation is slighly different from the 2x2 matrix representation on the quaternions page; the two are related by the isomorphism b -> c, c -> -b.

The basic point is that there is a deep connection between the algebras of quaternions and Pauli matrices, and between the use of quaternions to represent rotations and the rotation operator for spin-1/2 particles.

- Steven G. Johnson, Wed May 28 20:34:39 EDT 2003

Ah I see you spotted my "spinning particle" reference on magnetic field. Call it my little bit of rebellion -- I'm inclined to think the difference between QM spin and mechanical spin is rather exaggerated. BTW Griffiths calls B the magnetic field and H the "auxillary field", hence the article title. -- Tim Starling 02:10 10 Jun 2003 (UTC)

Hi Tim. There is an important difference between QM spin and a (classical) spinning particle: the axis of a spinning particle is a 3-vector, whereas QM spin is not (there is an observable difference in how they transform under rotations). Regarding the term magnetic induction for B, it is a historical thing. Jackson uses magnetic field initially for B, but switches to magnetic induction when he starts talking about H. It's one of those rules that's observed more in the breach, but it's important to mention. -- Steven G. Johnson, Mon Jun 9 22:31:50 EDT 2003

Just saw your home page... do you know anything about quantum many body techniques, or ab-initio quantum chemistry? -- Tim Starling 02:38 10 Jun 2003 (UTC)

Some, although it's not my speciality (my work more involves solid-state physics applied to classical electromagnetism, not quantum mechanics). -- Steven G. Johnson

Damn. I thought you might be able to help me with my PhD project, because my supervisor seems to be incapable. Your comment about spin hit my misconception dead-on -- let's just say I was rather humbled. You must be a very good lecturer, not to mention an exceptional physicist. Don't waste too much time hanging around Wikipedia, okay? -- Tim Starling 03:11 10 Jun 2003 (UTC)

-

Hi there. What's the the handedness of the universe? (seen on Pseudovector) -- Tarquin 20:29 12 Jun 2003 (UTC)

You can't really define an absolute "handedness". If you want a left-hand rule for cross-products, you just slightly change your definitions of things like the magnetic field. The real question is whether the laws of physics are invariant under inversion; for classical physics they are, but for weak interactions they are not. To take a more simplistic example, suppose that some observable quantity depended upon the sum E+B (assuming compatible units). After inversion, this becomes B-E, and this is not just a change of definitions because Maxwell's equations (which are invariant) also relate E and B...so an experiment measuring that quantity could determine whether the inverted or non-inverted version was correct, but you can still always define things to use a right-hand rule. -- Steven G. Johnson

Regarding your cross-product edit on handedness: does that mean that in a LH system, a ^ b is still defined as a RH triple? I know of at least one programming language where that is not the case. -- Tarquin 09:01 13 Jun 2003 (UTC)

-

Howdy ....

I am writting you concerning the Maxwell equations.

... as you are a post-doctoral associate in theoretical physics, I'd appreciate it if you's locate and read:

T. W. Barrett, "Electromagnetic Phenomena Not Explained by Maxwell's Equations," in A. Lakhtakia (ed.), Essays on the Formal Aspects of Electromagnetic Theory, World Scientific, River Edge, NJ, 1993, p. 6-86.

... also .... Doug sweetser explains quaternions .... [something that Gibbs and Heaviside did not understand or neglected to address]

http://world.std.com/%7Esweetser/quaternions/intro/scalarsvectors/scalarsvectors.html


 * There is the electromagnetic potential, which has a scalar field phi and a 3-vector potential A.


 * To do calculus with only information contained in events requires that a scalar and a 3-vector form a field. According to a theorem by Frobenius on finite dimensional fields, the only fields that fit are isomorphic to the quaternions .... requirement and an identical solution.  This is the logical foundation for doing physics with quaternions.

http://world.std.com/%7Esweetser/quaternions/EandM/gauges/gauges.html

-- It's not hard to understand the quaternion notation that Maxwell used, it's quite simple. I'm sure Gibbs etc. was able to follow it. They just didn't like it. User:Stevenj


 * In the quaternion representation, the gauge is a scalar generated in such a way as to not alter the 3-vector.

http://world.std.com/%7Esweetser/quaternions/classical/sho/sho.html

-- Maxwell originally (even before quaternions), chose to use the vector potential explicitly, and he picked a particular gauge (the Coulomb gauge I believe, div A = 0). Nothing special here; people use vector potentials and pick gauges all the time in modern notation as well. User:Stevenj


 * In fact, the four Maxwell equations appear to be one nonhomogeneous quaternion wave equation, and the structure of the simple harmonic oscillator appears in the Klein-Gordon equation.

... mabey more later ...

Thanx for reading .... reddi 03:23 7 Jul 2003 (UTC)

Thought you might find this useful: User:Tim Starling/Reddi watchlist -- Tim Starling 02:25 27 Jul 2003 (UTC)

I'm not certain which "Russian school" is referred to in the "real number" discussion page, but it's probably something about constructivism, which is a philosophy that holds that an existence proof is not valid unless it "constructs" the object whose existence is to be proved. For example, if you were to deduce a contradiction from the proposition that every even number greater than 2 is a sum of two primes, that would not be taken by constructivists to be a proof of the existence of a counterexample. Michael Hardy 00:19, 22 Oct 2003 (UTC)

I have made some minor changes to Curie point, with the aim to incorporate your ideas in a user-friendly description. I noticed you altered my earlier description of the Curie point to make it read (now) as if it were an infinitely abrupt change to paramagnetism. That is not my understanding of the Curie point. Would you mind if I altered your words slightly in this regard? Cheers, Humanist 08:59, 14 Nov 2003 (UTC)


 * If you define a paramagnet as having a spin-based magnetization in response to an applied field, but no spontaneous magnetization in the absence of an applied field, then indeed the material suddenly becomes a paramagnet at the Curie point. Below the Curie point, the spontaneous magnetization increases continuously from zero (although the slope is discontinuous at the Curie point).  Of course, even below the Curie point, an applied magnetic field will have an effect on the magnetization, but this magnetization follows a hysteresis curve, unlike a paramagnet.  On the other hand, the mechanism for the magnetic field to affect the magnetization is the same both above and below the Curie point, so in that sense there is paramagnetism everywhere (becoming weaker as temperature goes to zero and the hysteresis increases). Steven G. Johnson 19:12, 14 Nov 2003 (UTC)

Responding to your changes on the pages African-American and Role of women in Judaism, I must reply that I did not make these changes. My dad did it because I wouldn't let him get on to check his E-mail. Sorry. MattSal 23:22, Nov 18, 2003 (UTC)

Thanks for your additions to Laocoon and his Sons. My only problem with them is that your reference to "some accounts" makes it sound like a news story, whereas it is a mythological event described by various ancient authors. Can you identify which sources attribute the sending of the serpents to which gods? Adam 04:49, 4 Feb 2004 (UTC)


 * Apparently, the various ancient authors/storytellers were not very consistent. Virgil sort of  implies that Athena did it, but he's not very explicit; my memory of that made me look around on the web and found agreement in things like Bartleby.  Various accounts are quoted here.  The version blaming Apollo is attributed to Euphorion here.  It's also given in Hyginus' account here.  I'm anything but an expert on the subject, though; I'd love to see a well-researched description in the Laocoon article of who said what and when. Steven G. Johnson

Well done on your work on making Linux halfway readable. I just went the hack on Linux distribution, but I think I've died of bad writing fatigue. It's got some content, it just needs severe editing ... want a go? - David Gerard 12:26, Feb 5, 2004 (UTC)

-

Steven,

Nearly all of the litigation material you removed was mine. I agree that there are overlaps with the SCO v IBM article, but my intent in modifying the existing litigation text here was distinguishable, and I thought, useful to readers. Your impulse toward optimal parsimony is admirable, but not in a legal / user quandry context, I fear. Perspective is important in the WP, especially in considering the expected reader. This is, after all, an article of first reference, and for many will be an article of last reference as well. Its treatment should be commensurate.


 * Encyclopedia articles should be summaries, with side topics as pointers to other articles. It doesn't hurt people to click on a link if they want more information, but it does hurt to have a deluge of stuff about one set of events in 2003/2004 overshadowing an article about an operating system that spans decades. Moreover, it makes no sense to have the same material duplicated in two articles. Steven G. Johnson

I meant to summarize the legal situation in terms understandable to the ordinary user considering Linux (hence the location in the Linux article), and to do so in such a way that the history (the source of SCOG's claim) is not left entirely opaque (as it almost is to those of us who have been following the Unix genetic tree with special interest since the '70s). Furthermore, I attempted to bring out -- in a technical programming sense -- the cross pollination of algorithms, code fragments, public domain material, etc for the technically inclined new_to_Linuxer. And for those more concerned with the commercial side of things, to bring some of that out not overly opaquely as well. That I was unable to do so in so brief a paragraph as you have left is a function of the underlying messy reality, I think. I necessarily made many choices in the text I left, and many of them were conscioulsy to avoid leaving out stuff that was (1) understandable to a non-lawyer, (2) potentially significant to someone who might be considering where the litigation left him/her/them as a Linux user or potential user, or (3) useful in understanding the damage IP litigation can cause. I didn't want to 'dumb it down' too much.

As the article is currently, a reader of the Linux article -- perhaps coming to the WP to make some sense of (the nearly always incompetent journalistic coverage) what appears to be a Big Deal in regard to Linux -- is left with what is, to my eye, far too little and that little appearing, and too some extent, being, too legally technical. The linked article is, in my view, 'too legal' altogether.


 * Then fix the linked article.

Accordingly, I would suggest returning the material (or some version of it -- this being a Wiki my immortal prose is hardly the final say) to this article.

My minor edits to the existing paragraph on FUD were intended for more or less the same purpose. FUD exists and has existed and is $ignificant in the marketing of many things. Computers and computer software are the most commercially significant of these, I suppose. Some anti-Linuxers have been caught spreading FUD (ie, financing bogus research reports and issuing peurile press releases) and that is a fact those new to Linux should at least be told. It is not POV (or anti any particular vendor -- and surely we all know the vendor who's most prominent in this matter) to say so in a non accusatory way. Even if some of the accusation has been publicly demonstrated. Political correctness, as I remember it developing, was intended to reduce personal pain, to 'proactively' avoid hurt feelings. Since commercial interests don't have feelings, being persons only in legal fiction, it shouldn't be, in my view extended to them. I would retain the FUD paragraph as I last edited it.


 * General accusations of FUD, without citations or quotations or facts, are advocacy, and/or are so vague as to be meaningless. Nor do long analyses of particular Microsoft etc. statements belong in the article. Steven G. Johnson

On to other points.

I remember a post from the early '90s (and I cannot find it after a brief search) from Linus, or Lars, attributing world domination to Tux. Thus you may conclude that that also was my contribution. I would argue it is not POV to explain something that resulted from the POV (in this case, a disdain for MS and its practices and engineering quality) of the players involved. Besides, it's funny. Recall that Linus has spoken and posted at some length on the espression that Tux is supposed to have -- fat and happy after a (burp!) large meal of herring. It may help to have a Scandinavian approach on this -- lutefisk is popular in Norway and I don't get that either. But so it goes...


 * That quote is not widely attributed to the mascot. It is a common joke among Linux users, but this would be better expressed via a direct quote.  And even then, inside jokes don't really belong in the introductory paragraph about an OS.  Nor should the encyclopedia text itself be making snide obscure references to Microsoft as "a certain large software company". Steven G. Johnson

As for 'around some words' as opposed to "around others", the subject of one of your edits, I use ' ' in my writing as a marker for something that I am not "quoting directly", but am stressing an unusual use of. A usage "...up with which I will not put.", if we can extend one of Winston's peeves a bit. In short, it's a warning to the reader not to take 'this material' exactly straight. In my case it's usually a marker of irony or sardonicism (if this is not a 'word', I apologize.) To wit, I really abhor 'proactive', hence its flagging above. Miss Fidditch surely didn't like ee cummings, nor probably archie the cockroach either, and she gave me some grief too. But since I ditched school and don't have to listen to her anymore, I've found the language's clothes a comfortable fit, including this instance. Our rules, in this shared anarchy that is and has been English, aren't (shouldn't be?) too tight for such comfort. Do you think they should be tighter than I would wear them?


 * Double-quotes to indicate special usage or irony are the standard punctuation in English, not single quotes. Gratuitous substitution of one glyph for a nonstandard one is distracting and unnecessary.  (I'm a fan of cummings, too, but that doesn't mean that I think encyclopedia articles should be written like he wrote his novel Eimi, which is nevertheless a remarkable work.) Steven G. Johnson

Reactions?


 * Please continue discussions on Talk:Linux if you feel it necessary.

ww

PS: Congratulations -- too long delayed -- on the Wilkenson. I'm not current with numerical software, and so learned about it from your home page. Good work!

Could you check Maxwell's equations article. Somebody changed a 90 degrees out of fase to in phase for E & M waves, and I'm ashamed to say that I do not recall (and don't have time to derive) which one is correct. --AstroNomer 21:12, Mar 18, 2004 (UTC)


 * The current version is correct: the electric and magnetic fields are in phase for a plane wave. (From Maxwell's equations, the spatial derivative of one must equal the time derivative of the other, so e.g. they have to be both cosine or both sine curves.) &mdash;Steven G. Johnson 22:37, 18 Mar 2004 (UTC)

Hello, Steven. Please have a look at Talk:Trigonometric function where I'm challenging you etymology of the word sine in English. &mdash;Herbee 20:57, 2004 Mar 25 (UTC)

Thanks for taking the time to explain; it really is an interesting story. I have made a slight update to the Trigonometric function article to prevent future confusion about the issue. &mdash;Herbee 11:23, 2004 Mar 26 (UTC)

Greetings! I have nominated you for adminship; please visit RfA to accept or decline the nomination. +sj+ 22:22, 2004 Apr 10 (UTC)

Hi! I posted a question on Talk:Haversine formula, so I thought I'd drop a line here to let you know. --Delirium 08:53, Apr 12, 2004 (UTC)

Steven, I am sorry to inform you that I have listed you at Quickpolls. Reddi was listed there for a reversion war today, and when I looked at the evidence, I saw that you too had violated the three-revert rule today. I have listed you there because I think, in an edit war, we need to be fair and list both participants if both break the rules. I have no idea who started what, or what you felt justified your actions: if you want to discuss anything with me, I'm more than open-minded about this, having almost no familiarity with the situation. Thanks. Jwrosenzweig 21:08, 16 Apr 2004 (UTC)
 * I forgot to clarify -- you may post any comments you like for your Quickpoll, but you are not allowed to vote. I suppose that's common sense, but policy suggests I let you know about this.  Thanks. Jwrosenzweig 21:13, 16 Apr 2004 (UTC)

I totally support you on being listed on a quickpoll. The users on wikipedia, the wikipediaholic cabal, don't care about content, scientific integrity, and accuracy. They care about the rules and a stict adherence to them in every situation, no matter how right you are.

They pretend like uncommon subjects such as the ones Reddi typically butchers will be fixed by the wikiprocess when in reality it's something only someone with an interest or real knowledge in that field writes about where they are few and far between. Honestly, the pages you tried to fix WERE butchered, and you did the right thing, no matter how silly the rules are. They don't care, however. Not a drop. It's become more of a "let's play government" then "let's make an accurate and reliable free, online encyclopedia!".

I recommend you to be extremely wary, or, preferably, to ditch this site as soon as possible. If you want to see why I'm so incensed, just go here:

http://en.wikipedia.org/wiki/Wikipedia:Quickpolls/Archive#Reddi_and_Lord_Kenneth

Also, scientific_skepticism is something you should see, as it's what got me involved with our mentally ill friend Reddi in the first place. - Lord Kenneth 05:10, Apr 17, 2004 (UTC)

FYI
The NPOV dispute notice you placed on the Property damage article has been removed by another user, in case that interests you. -- Decumanus | Talk 02:06, 18 Apr 2004 (UTC)


 * Thanks. In retrospect, I should have posted an explanation on the talk page, but I was just "passing through" and it seemed obvious that the article contained advocacy of a particular point of view, and I never visited back to see that people were confused.  I've posted an explanation there now.  &mdash;Steven G. Johnson 19:54, Apr 18, 2004 (UTC)

Sysop
Congratulations! You are now an administrator after getting 100% support on RfA. You should read the relevant policies and other pages linked to from the administrators' reading list before carrying out tasks like deletion, protection, banning users, and editing protected pages such as the Main Page. Most of what you do is easily reversible by other sysops, apart from page history merges and image deletion, so please be especially careful with those. Good luck. Angela. 20:01, Apr 18, 2004 (UTC)


 * Congratulations, Stevenj! Cribcage 20:29, 22 Apr 2004 (UTC)

Fellow MIT person
We should hang out. moink 22:34, 16 May 2004 (UTC)


 * Sure...it will be interesting to see how many MIT folk come to the Boston get-together. Of course, MIT people can be pretty lame about attending social events, so the sample may be skewed.  =)  &mdash;Steven G. Johnson 08:17, May 17, 2004 (UTC)

Equation arrays
On Four-vector you said "don't use nbsp; for formatting kludges". Okay, but what's the right way? I've tried various things (see User:Wwoods/math alignment). In that particular case, I still think the line should be broken somehow; as it is, it's too wide for the page.--wwoods 06:20, 2 Jun 2004 (UTC)


 * The right thing to do is to wait for Wikipedia to support \begin{eqnarray}; pestering the developers about this couldn't hurt. &mdash;Steven G. Johnson 16:41, Jun 2, 2004 (UTC)

Hfastedge 20:31, 12 Jun 2004 (UTC)
re the b/e condensate, just check out original quote from the version where i just added the image. You may want to bring back this text that echoes both of our concerns. re the copyright concern, no i will not engage you or anyone about _concerns_ unless the concern is from a court of the country i live in.


 * I don't understand what you are saying; please see your talk page for additional comments. &mdash;Steven G. Johnson 20:47, Jun 12, 2004 (UTC)

Also, i want to know the difference between a fock and hilbert space. Hfastedge 20:31, 12 Jun 2004 (UTC)


 * A Fock space is a specific example/kind of a Hilbert space. &mdash;Steven G. Johnson 20:47, Jun 12, 2004 (UTC)

"What links here" broken for images?

 * from the pump

I've noticed recently that clicking on "What links here" for an Image: page lists nothing, even though pages do link to the image. For example, click on the image from Bose-Einstein condensate, and then click on the image's "What links here" &mdash; it says that nothing links to it. Am I doing something wrong, or is this a bug? Thanks. &mdash;Steven G. Johnson 20:56, Jun 12, 2004 (UTC)
 * The switch to 1.3 created this issue. It's been reported multiple times on the bugs page. &rarr;Raul654 21:45, Jun 12, 2004 (UTC)

Trigonometry, Fourier, etc.
Perhaps you can contribute to What is trigonometry used for?, especially the sections on Fourier transforms and Fourier series? Michael Hardy 18:22, 25 Jun 2004 (UTC)


 * PS: The target audience is the students in a trigonometry course quoted near the beginning of the article. (But that's not necessarily written in stone.) Michael Hardy 18:24, 25 Jun 2004 (UTC)

X Window System
I've just added a metric shitload of stuff on history, common criticisms and links to this, as per objections on WP:FAC - if you have time, please go the hack on it - David Gerard 13:49, 30 Jun 2004 (UTC)

GNU/Linux naming controversy
Removing that material again was innapropriate. Just because it is not attributed does not mean it needs to be deleted. It is a fallacy to think that the only good point can be made is one that can be attributed to someone else. It can be attributed later if need be. Deleting good material from an article is not necessry. instead suggest improvements for it. Re-reverting the deletion was especially innapropriate. You made your point, others disagreed. Bring it to the talk page before re-reverting. - Taxman 01:27, Jul 10, 2004 (UTC)

Steven is relentless in reverting edits without providing an adequate reason. It's too bad. I've seen sub-par contributions made by anonymous visitors preserved but transformed by creative Wikipedia writers resulting in a worthwhile and lasting contribution. This is the mark of a true Wikipedia editor. I wish Steven would be inspired by these acts. Knee-jerk reverting of edits (thus disbarring other Wikipedia users from improving the contribution) is probably not the best way to contribute to Wikipedia.

--66.82.9.80 18:15, 14 May 2005 (UTC)

Discrete Fourier transform
Thanks for your corrections on discrete fourier transform. You were correct in using e instead of exp. The e notation provides more information. What do you think about my rewrite ? Did it make the definition clearer ? MathMartin 21:56, 5 Aug 2004 (UTC)

List of Fourier analysis topics
Hello. You are perhaps better qualified than most of us to help expand this now very stubby new page. Michael Hardy 23:36, 21 Aug 2004 (UTC)


 * Shouldn't this just be a category of some sort? &mdash;Steven G. Johnson 20:40, Aug 22, 2004 (UTC)

Interesting question. Look at list of lists of mathematical topics (not to be confused with list of mathematical topics). Should all of those be just categories too? I think that list began before categories existed. I'm not yet accustomed to thinking in terms of categories on Wikipedia. What difference between list of combinatorics topics and the categories called Combinatorics explains the difference in purposes between categories and such lists, if any? Michael Hardy 23:09, 22 Aug 2004 (UTC)


 * My impression is that most of the list of pages pre-date categories, and that categories were intended to (largely) replace them. (The only exception might be list of pages that have some kind of informational content in addition to simply the list.) &mdash;Steven G. Johnson 04:48, Aug 23, 2004 (UTC)


 * Lists are also used for the value of the red links - a list can be more complete than the category. See Categories, lists, and series boxes - David Gerard 17:40, 23 Aug 2004 (UTC)

Categories in their present form fail to replace lists for the following reason. A list item may look like this:


 * This topic

The reason for the invisible link to the discussion page is so that when you click on "related changes", the edits to discussion pages will be included. This device is used in list of mathematical topics, list of physics topics, list of religious topics, and lots of others. (But not yet in list of Fourier analysis topics, and not yet in lots of the mathematics subtopics lists.) This doesn't work with categories; I just tested it. Michael Hardy 18:02, 27 Aug 2004 (UTC)


 * You should probably file a bug report for the categories, then. &mdash;Steven G. Johnson 19:01, Aug 27, 2004 (UTC)

Could be. But here is yet another thing that topics lists can do that categories cannot. Perhaps this one is a substantial advantage only in lists of intermediate size, and not in very short or very long lists. I strongly suspect list of mathematical topics is by far the longest, and thus too long for this, and list of Boolean algebra topics too short (last I checked). And that is what happens in list of combinatorics topics and list of probability topics and list of geometry topics and some others: they can organize the list into various subtopics. Michael Hardy 20:11, 27 Aug 2004 (UTC)


 * ... so categories seem to lack flexibilty whereby a topics list can be adapted to its subject matter in various ways. In their present form, anyway. Michael Hardy 20:13, 27 Aug 2004 (UTC)


 * ...and another thing: As far as I can tell you can't move a badly named category.  All you can do is edit every page that links to it, thereby creating a new category with a different name.  These are really very much inferior to topics lists. Michael Hardy 00:41, 2 Oct 2004 (UTC)


 * ... and another: I just read that "There are 1 subcategories to this category." Whoever created these "categories" should be sentence to Cruel and Unusual Punishment. Michael Hardy 00:44, 2 Oct 2004 (UTC)

Note
I've left a moderately lengthy reply to your posting on the Village pump. I thought I'd let you know, as I'm sure it's an important issue to you. Look over my response at your leisure, and please don't hesitant to contact me if you would like clarification or further thoughts. Thanks, and please keep up the good work -- I appreciate your expertise and your even temper, and am glad you devote time to us here. Jwrosenzweig 23:54, 25 Aug 2004 (UTC)

Quantum Superposition
Hi would you agree that the single split experiment you mentioned in quantum superposition was a slip of the pen? I'm not a physicist, but it seems to me that this should be double-slit experiment. Erik Zachte 02:15, 30 Aug 2004 (UTC)


 * Actually, there are both single- and double-slit experiments, for both electrons and photons, and both illustrate interference from the superposition of waveforms (in the single slit experiment, it comes from the slit having finite size, and you therefore get a sinc pattern in the far field). But I agree that a double-slit experiment is probably better to cite here as it is more familar and intuitive, not to mention having a nice Wikipedia article; "single-slit" was probably a mistake on my part, I don't remember.  &mdash;Steven G. Johnson 07:55, Aug 30, 2004 (UTC)

Data Management Wiki Committee
Thank you for your contribution to one, or more, articles that are now organized under Data management.

Because of your previous intrest, you are recieving an invitation to become a founding member of the Data Management Wiki Committee.

The members, of course, will form and solidify the purpose, rules, officers, etc. but my idea (to kick things off) is to establish a group of us who will take responsiblity to see that the ideas of Data management are promoted and well represented in Wikipedia articles.

If you are willing to join the committee, please go to Category_talk:Data_management and indicate your acceptance of this invitation by placing your three tilde characters in the list.

KeyStroke 01:29, 2004 Sep 25 (UTC)

Prof. Joannopoulos
PS: Please say "hi" to Prof. Joannopoulos from me. He won't remember me; I was merely one undergrad amongst the many unwashed whom he was sentenced to teaching many aeons ago as a newly-minted professor. (I honestly can't even remember what the course was now - I don't think it was 8.012 or 8.022, but I can't figure out what else I would have taken that he would have been a recitation instructor for). However, I distinctly remember him (and it's a pleasant memory, too, in case that sounded ominous :-). Noel 02:42, 29 Oct 2004 (UTC)

Style guide
Thanks for your help with the style guide article. We have resolved our dispute. Maurreen 22:57, 31 Oct 2004 (UTC)

Boston gathering
I'm hoping for another meeting the weekend of the 20th. Will you be around then? Cheers, +sj +  21:13, 3 Nov 2004 (UTC)


 * Probably. I've added a note to your page. &mdash;Steven G. Johnson


 * Great. Let's meet in Harvard square tomorrow night; see Meetup/Boston.  Any chance of getting mihai to come this time?  +sj +

Cheung1303
Thanks for your message. I've started a request for comment on him, to see what we can do about this. If you're willing to certify this RfC, that would be appreciated. --Michael Snow 05:56, 5 Nov 2004 (UTC)

Article Licensing
Hi, I've started a drive to get users to multi-license all of their contributions that they've made to either (1) all U.S. state, county, and city articles or (2) all articles, using the Creative Commons Attribution-Share Alike (CC-by-sa) v1.0 and v2.0 Licenses or into the public domain if they prefer. The CC-by-sa license is a true free documentation license that is similar to Wikipedia's license, the GFDL, but it allows other projects, such as WikiTravel, to use our articles. Since you are among the top 1000 Wikipedians by edits, I was wondering if you would be willing to multi-license all of your contributions or at minimum those on the geographic articles. Over 90% of people asked have agreed. For More Information:
 * Multi-Licensing FAQ - Lots of questions answered
 * Multi-Licensing Guide
 * Free the Rambot Articles Project

To allow us to track those users who muli-license their contributions, many users copy and paste the " " template into their user page, but there are other options at Template messages/User namespace. The following examples could also copied and pasted into your user page:


 * Option 1
 * I agree to multi-license all my contributions, with the exception of my user pages, as described below:

OR
 * Option 2
 * I agree to multi-license all my contributions to any U.S. state, county, or city article as described below:

Or if you wanted to place your work into the public domain, you could replace " " with "  ". If you only prefer using the GFDL, I would like to know that too. Please let me know what you think at my talk page. It's important to know either way so no one keeps asking. -- Ram-Man (comment| talk)

Special Relativity
Steven, I saw your comment on the "no original research" draft policy page, looked you up, and saw you are a physicist. There's a debate brewing over at Special relativity regarding the claim in the article that the second postulate has been "experimentally verified." The article was nominated for Featured Article status at Featured article candidates. An anonymous editor wrote in saying that the second postulate has not been experimentally verified, and that this makes the article fundamentally flawed. His argument seems to be that it cannot be tested, therefore cannot be falsified and, therefore, is not scientific. The same editor also wrote a complaint about the article on the WikiEN-l mailing list. I'm not in a position to judge whether this minority view (assuming that's what it is) is "respectable" or not. If you have the time or inclination, it would be very helpful to have a physicist take a look at the issue; of course, if you have neither, please don't worry about it. See Talk:Special relativity for the objecting editor's latest explanation of his concern. Best, Slim 00:20, Dec 14, 2004 (UTC)
 * Steven, thanks for looking at the SP page. Do the other person's views count as "original research" in your view, or are they the kind of views you'd find in a peer-reviewed journal (even as a minority view)? I'm afraid I'm not in a position to judge. Slim 04:17, Dec 15, 2004 (UTC)

Re the location of metadata
Hi Steven. I noticed you moved back the template on sources from the Manifest Destiny talk page to the article page itself. Note we already warn readers that Wikipedia is not perfect by linking to a disclaimer page on every single page. To splatter some templates across the top of the article page does not help readers - as you are only too aware literally hundreds of thousands of articles on Wikipedia do not effectively cite sources. To single out a few of them leaves the reader with a false impression that other pages have been sourced correctly. As such information for editors really should go on the editor's (i.e. the talk) page.

Yes I know that NPOV and disputed tags amongst others often go on the article page. I don't think they should and I am trying to build a consensus about when it is appropriate to use the article page - I think it is appropriate to have vfd tags on the article page for example. See Template messages/Disputes and its talk page for more. Pcb21| Pete 18:27, 2 Jan 2005 (UTC)


 * I think you are in the minority about having these tags go in talk. Yes, there are lots of pages that don't cite sources, but some stand out more than others.  In particular, Manifest Destiny has lots of interpretive statements that cry out for sources (or to be removed as original research). &mdash;Steven G. Johnson 01:19, Jan 3, 2005 (UTC)


 * The talk page is not "under the rug". I am not sure about being "in the minority", the relevant talk pages seem mostly empty - where is the meat of the discussion on this point. I can't believe the top of the article, sometimes with colours, sometimes with boxes, sometimes in italics, all methods of emphasising editor information ahead of actual content would be the consensus view if there was a broad discussion on it. For now I will leave Manifest Destiny as the odd-one-out. Pcb21| Pete 01:58, 3 Jan 2005 (UTC)


 * I think the basic point of departure between us lies in your description of tags like or  as "editor information".  A warning that there is a specific reason to doubt the accuracy of a particular article (as opposed to the general disclaimer that applies to all Wikipedia) is tremendously important for readers, not just editors. &mdash;Steven G. Johnson


 * Furthermore, putting it on the talk page is "under the rug" because (a) most readers don't look at it and (b) most editors' exposure to most pages is to the article, going to the talk page only if there are complaints and (c) even when editors do read the talk page, it is often to scroll to the end to add their own comments, and they can easily miss a tag at the top. &mdash;Steven G. Johnson

Moving tags to Talk: pages
How funny! I dropped in to leave you that pointer, and I see you've already been in communication with the person who's doing it! Anyway, they got the page name (above) slightly wrong (I have now fixed it); you can see their comment (from before they started this process) at Wikipedia talk:Template messages/Disputes. Noel (talk) 03:26, 5 Jan 2005 (UTC)


 * Thanks. From the link, it looks more like one person's unilateral campaign than a "movement", though.  Sigh.  &mdash;Steven G. Johnson 04:40, Jan 5, 2005 (UTC)

The images on Neoplan Centroliner
Thanks for updating voters about the Cheung/Jeffery situation on WP:FAC, Steve. I think it's important to mention this new light on the situation on the RfC page on Cheung, too. Or maybe even better, to delete the whole thing. I read it through before posting on WP:FAC, and I never realized the information wasn't current. I looked at Cheung's and Theresa's talk pages, too (I didn't have the intuition to look at Jefferry's, apparently the only location that would have helped—I've found it now). There's no retraction on the RfC page, where you yourself call for a permanent ban on the grounds of malice, sockpuppetry, transparent deception, etc, and other editors say similar things. It's a "live" RfC as far as anyone can tell, there's a link to it from the main RfC page, and now you tell me it's completely out of date and merely records "suspicions" that have since been resolved? That's not exactly fair to Cheung or Jeffery. I don't feel so good myself about looking like a fool on WP:FAC, either. :-(--Bishonen | Talk 23:43, 5 Jan 2005 (UTC)


 * I've added a note to RfC that the Jefferry situation has been resolved (actually, the RfC already included comments by myself and others expressing second thoughts about the Jefferry suspicions). The rest of the text on that page, about Cheung1303's persistent uploading of copyvio images even after the RfC, is still valid.  The only thing that seems to have gotten through to him is when we started deleting his uploads on sight unless they were clearly sourced and properly tagged. &mdash;Steven G. Johnson 22:20, Jan 6, 2005 (UTC)

Mac Web
Nice job on the MacWeb article, thanks! --User:RoySmith 00:38, 16 Jan 2005 (UTC)

illates
Yeah, it was obscure, but it wasn't gratuitious. I was going to use "infers", which is a more correct synonym, but "illates" implies the process of developing the conclusion brings facts in from outside the system, while "infers" implies that the facts are immanent in the system itself. And in this case it's necessary to collect the facts from many sources outside the system. So I had to go with "illates". Linking it to the wiktionary might have been a better course. I may do that. Blair P. Houghton 05:49, 18 Jan 2005 (UTC)


 * It was gratuitous because "relates to" was synonymous to "illates" in this context and is not obscure.  "infer" is equally infelicitous in this context because it clashes with a more common usage of the same word in modern English to mean an act of reasoning (as opposed to simply an implication), compared to something unambiguous like "leads to".   &mdash;Steven G. Johnson 06:07, Jan 18, 2005 (UTC)

Well there's part of the problem. I meant brings in more than leads to, which is why I couldn't avoid illates (without degrading the tone). I didn't see anything wrong with making the reader reach for a dictionary, either. I mean, if they have enough time to go spelunking in the crannies of the abortion debate, they might as well learn something... Blair P. Houghton 17:06, 18 Jan 2005 (UTC)

Response from MITAlum
You wrote: "I noticed that you uploaded several images to the MIT article, and I'm concerned that you are inaccurately describing their copyright status. For example, you described Image:MIT.gif and Image:MIT-brassrat.jpg as being "licensed under the terms of the Wikipedia copyright" when they most certainly are not GFDL. Please realize that, if you find an image somewhere on the web, by default it is not licensed under terms usable by Wikipedia, unless you find an explicit statement to the contrary.  (And even in this case you should link to the source of the image and to its license statement.) You also uploaded several images copyrighted by "Jackson Frakes".  I have marked these as "unverified" because of your other copyright confusions.    Can you give us more information about where you got them and why you believe them to be usable by Wikipedia?  (Are you Jackson Frakes?)."

My response: 1. Yes, I am Jackson Frakes. Please remove the unverified tags on those images. 2. I think I was just cutting and pasting without thinking on the other MIT images -- those images should be copyright MIT, but I'm sure they're OK for use on Wikipedia the same way other university logos as presented. Thanks,

-MITalum 21:49, 21 Jan 2005 (UTC)

Need a higher quality math font
Can you help push for a higher quality math font? My website needs the smoothest integrals on the net.

http://www.exampleproblems.com/wiki/index.php?title=PDE8

-Thanks -Todd

Bessel function
Thank you for your recent edits to that page. The anon after which you cleaned up recently, has vandalised some pages in the last several hours. I would suggest that you scrutinize all the edits that person did on Bessel function (I took a passing look, that person did not exactly insert meaningless things, but I would not take anything by that person in good faith). Thanks a lot. Oleg Alexandrov 05:37, 12 Mar 2005 (UTC)


 * Thanks for the heads-up. All he really did was to insert the power-series expansion of the Bessel function $$J_\alpha$$, which I believe is correct (I checked it against another web page, anyway). &mdash;Steven G. Johnson 01:06, Mar 13, 2005 (UTC)


 * Great. That person was indeed very strange, putting correct changes on some pages and vandalizing others at the same time. Eventually, last night one admin blocked him/her indefinitely. That might be a lesson for that person. Oleg Alexandrov 01:18, 13 Mar 2005 (UTC)

History of South Africa images
I replied to your comments about the images on South Africa, but the South African government released a lot of images that it felt were most related to the apartheid-era, or they are from the UN and are clearly marked as such on Commons. The UN released the apartheid era images at the request of the South African government and the Truth and Reconcilliation Committee. Páll 22:01, 24 Mar 2005 (UTC)


 * The images from the UN were clearly marked as such; that's not the problem. However, I went to the UN web page and I couldn't find any clear statement of the copyright on the images or whether they were PD...there was only a note saying to contact them if you wanted to use the pictures, which seemed like a bad sign to me.  &mdash;Steven G. Johnson 03:18, Mar 25, 2005 (UTC)

I did contact them, and according to South African law, all images taken by public organisations pertaining to abuse under apartheid no longer have copyright. Páll 03:19, 25 Mar 2005 (UTC)
 * Please include the email or the reference to the relevant law under each image as support for marking it PD. &mdash;Steven G. Johnson 03:29, Mar 25, 2005 (UTC)

OK, done, I indicated that they fell under the South African Intellectual Property Laws Amendment Act 38 of 1997. Páll 03:45, 25 Mar 2005 (UTC)

Two questions
1. Meetup Sunday, at Asmara in Central Sq. Come, come! Discussions of MediaWiki hacking, April Fool's, and the birth of Spring.

2. Would you be willing to help out with some article evaluation at the end of the month? For a little contest...

Cheers, +sj  +  11:50, 25 Mar 2005 (UTC)

Swastika
I believe I have addressed your concerns about this article's FAC. Perhaps you could check back and re-evaluate your vote. Cheers, Smoddy (tgeck) 23:16, 25 Mar 2005 (UTC)

Luminiferous ether
Hi Steven, In the current luminiferous ether article it is stated:
 * The main reason for his rejection stemmed from the fact that both men could apparently only envision light to be a longitudinal wave,

I have a problem with that statement. (I haven't looked up who wrote that, I write to you because you reverted to that.) Huygens and Newton are known for being extremely proficient at envisioning, I think it is a mistake and a lack of respect to suggest they couldn't envision transversal waves. (And I think that if a wikipedian decides to speculate about what they were apparently thinking, then the speculation should be in admiration rather than in disdain.)

Transversal waves that are propagating as undulations of a medium can only propagate in a solid because shearing must be elastically opposed. In my opinion it is far more likely that Huygens did not consider transversal waves since that hypothesis is ludicrous.

The assessment that if light is a wave phenomenon it must be propagating undalations in a medium is the scientific assessment. To hypothesize that a wave phenomenon can propagate without medium goes against insightful physics expectation, scientists did not consider that until all other avenues were exhaustively explored.

The reason I get annoyed is that in the current article Newton and Huygens get faulted for not being aware of the 300 years of scientific discoveries of the 17th, 18th and 20th century. That is like mocking the captain of the Titanic for not using radar equipment.

In the current article it is stated that Thomas Young was the first to consider the possibility that light consists of transversal waves. I think that is an extremely unliky account of history. I think Thomas Young traded one absurdity for another. The evidence available at the time was conflicting, at the time it was simply not possible to frame an hypothesis that was consistent with all available evidence. Quantum Electrodynamics was the first self-consistent theory that is consistent with all available evidence.

In my opinion, when a historical account is given, the performance of the scientists of the time should be measured against the scientific evidence that those scientists actually had. I think history is presented in a distorted way if scientists of the past are judged for how good they are in agreeing with modern insights. --Cleon Teunissen | Talk 05:49, 10 Apr 2005 (UTC)

I have downloaded the PDF with the 1718 edition of the Opticks. I don't know whether I will have the time to see for myself whether Newton discusses a wave hypothesis at all. Until I'm better documented, I will not edit the Luminiferous ether article. --Cleon Teunissen | Talk 05:49, 10 Apr 2005 (UTC)


 * The statement that you complain about was paraphrased directly from the preface to my Dover edition of the Opticks, written by a historian I believe. Nor, if you read the Opticks, will you find any mention of transverse waves&mdash;and Newton explicitly criticizes Huygens' wave theory precisely because longitudinal waves cannot have two "sides".  (I have no doubt that Newton was aware of transverse waves, e.g. on a stretched string...however, he didn't seem to consider them as a possibility for light.) &mdash;Steven G. Johnson 16:22, Apr 10, 2005 (UTC)

It seems to me you have missed my point. It is part of science that scientists don't bother to consider preposterous suppositions. The fact that neither Huygens nor Newton discuss transversal waves as a candidate for propagation of light indicates fine scientific judgement on their part. Through the 19th century physicists tried to make transversal waves propagating in a luminiferous ether work, and the stuff just became more and more magical, so the absurd luminiferous ether had to go. In modern times, the idea of light as transversal waves has been dropped, in quantum electrodynamics light is not mechanical waves. I think it is wrong that Huygens and Newton get faulted for not considering a supposition that was a dead end anyway. (I am aware that during the time that Maxwell developed the Maxwell equations, he was immersed in theories to make the luminiferous ether work, and it is not clear whether he would have been able to develop the Maxwell equations without his visualisations of the physics of the luminiferous ether. The Maxwell equations are everlasting physics, the luminiferous ether was a dead end.)--Cleon Teunissen | Talk 17:48, 10 Apr 2005 (UTC)


 * If you want to speculate about what Newton thought but did not write down anywhere, go ahead, but it doesn't really belong in Wikipedia. (By the way, I beg to differ: modern science still counts light as a transverse wave phenomenon, just not a mechanical one in a medium.)  Note that the Wikipedia article does credit Newton for writing that even Huygens' longitudinal waves in an aether are hard to reconcile with the motion of celestial bodies; he was a shrewd fellow.  (Though absurd mechanical properties weren't what finally doomed aether theories in the 20th century.)  &mdash;Steven G. Johnson 04:28, Apr 11, 2005 (UTC)

I agree that I should not speculate (and in my edit I did.) I would like to propose that there should be no speculation whatshowever in the article. The current article makes a statement about what Huygens and Newton apparently overlooked. I propose to not mention transversal waves at all together with Huygens and Newton, so as to avoid speculation about what their thoughts on the matter were.


 * Since I was taking that statement directly from a published source, in particular a preface by a historian who presumably knows more about the subject than you or I, I think we should leave it the way it is. &mdash;Steven G. Johnson

As far as I can tell, Newton assessed that even the medium for longitudal waves would hamper Celestial motion, so I speculate that from his point of view all waves were equally unlikely candidates.


 * Apparently not, because he didn't discuss all kinds of waves. &mdash;Steven G. Johnson

Newton argues especially a difference between light and sound. Sounds are never seen to travel in directed beams. Travelling sound bends all over the place; light displays extremely little bending. Therefore argues Newton, light cannot possibly be a wave phenomenon. Actually, Newton did overlook something there, that (theoretically) he could have figured out with the knowledged available at the time. Huygens hypothesis could be reconciled with light casting rather sharp shadows, if light is assumed to have extremely short wavelengths. --Cleon Teunissen | Talk 06:34, 11 Apr 2005 (UTC)


 * Newton was aware that light bent at obstacles, but he was misled by (I think) some interference effects into thinking that light bent away from shadows instead of into them (as e.g. water waves do, an example he explicitly mentions). I didn't mention this additional reason for rejecting Huygens as I'd have to look more closely to figure out exactly what Newton was observing and thought, and I haven't had time for that.  The abovementioned preface specifically highlighted the birefringence as Newton's main reason, so I went with that (maybe there are letters and other materials by Newton that shed more light on the matter).  &mdash;Steven G. Johnson

Visualising the propagation of light
(By the way, I beg to differ: modern science still counts light as a transverse wave phenomenon, just not a mechanical one in a medium.)   &mdash;Steven G. Johnson 04:28, Apr 11, 2005 (UTC)


 * To my knowledge: according to Quantum Electrodynamics photons are not transverse waves. In the case of unpolarized light the individual photons are uncommitted to any plane of polarisation. As individual photons interact with a birefringent crystal, there is a 50/50 statistical distribution of interacting with the crystal in either of the two possible ways to be refracted. Prior to interacting with the birefringent crystal, individual photons were not polarized. After interaction with the birefringent crystal, there is a bias in how the photons will interact in situations where polarisation matters.
 * In classical wave dynamics, the square of the amplitude is a measure of the energy of the wave. In QED the square of the amplitude of the wave function is a measure of the probability of an interaction occurring.
 * There are strong parallels between the statistics of the behavior of photons, and the statistics of the behavior of transversal waves. The behavior of transversal waves serves as a good approximation to the propagation of light. This does not imply that modern science counts light as a transverse wave phenomenon. I think that modern science has learned to not impose human imagery on what photons "really" are. --Cleon Teunissen | Talk 08:20, 11 Apr 2005 (UTC)

First, if it has a polarization, even a polarization wavefunction amplitude, then it is essentially a transverse wave (even if not mechanical). At some point, though, we're just arguing terminology, though: yes, photons are spin-1 particles, where the spin relates to the polarization state (spin +/- 1 are the quantum analogues of left/right circularly polarized), so no, the polarization at the single-photon level is not quite a classical vector anymore (except as an aggregate of many photons). Second, it is not true that photons are always in a 50/50 statistical superposition of the two polarizations (this is true for randomly-polarized sources, like sunlight, but is not required of light by quantum mechanics). It is perfectly possible to have a completely polarized state, even for a single photon, which corresponds to a pure eigenstate of the polarization operator (or a particular superposition of +1 and -1 spin states), so that when you put it through an ideal polarizer 100% of the light is transmitted. &mdash;Steven G. Johnson 16:54, Apr 11, 2005 (UTC)


 * I guess I prefer the 'its not a classical vector' interpretation, which, I agree, is mostly a matter of taste/terminology. --Cleon Teunissen | Talk 16:29, 12 Apr 2005 (UTC)

Equivalence principle of relativistic physics
Hi Steven,

Is it OK with you if I consult you on the following physics matter? It is about the embryonic form of the Principle of Equivalence.


 * The breakthrough came suddenly one day. I was sitting on a chair in my patent office in Bern. Suddenly the thought struck me: If a man falls freely, he would not feel his own weight. I was taken aback. [...] A falling man does not feel his weight because in his reference frame there is a new gravitational field, which cancels the gravitational field due to the Earth. In the accelerated frame of reference, we need a new gravitational field. (Translation of a talk that Einstein had given in Japan in 1922, published in the aug.1982 issue of Physics Today, p. 45-47)


 * Just as is the case with the electric field produced by electromagnetic induction, the gravitational field has similarly only a relative existence. (A. Einstein, manuscript written in 1919, quoted from G. Holton, Thematic Origins of Scientific Thought, Harvard Univ. Press, 1973, 364.)

I'm not very familiar with classical electrodynamics. When a charged particle is being accelerated by an electrostatic field, does electromagnetic induction then generate (locally) an electric field that (locally) cancels the overall field? (Maybe it doesn't make sense to think in terms of classical electrodynamics when particles are concerned, but relativity is non-quantum.)

I am also intrigued by the analogy between inductance and inertia. A current circuit with a coil with self-induction does not resist current strenght, but it does resist change of current strength, much as inertia doesn't resist any velocity, no matter how large, but it does resist change of velocity. In the case of inductance classical electrodynamics offers a mechanism: change of current strength induces a changing magnetic field that opposes the change, so the rate of increase in current strength is proportional to the applied electric potential.

By the way, I have contributed to the Sagnac effect article. The sagnac effect and the Twin paradox involve the same physics, as far as I can tell. What they have in common is the element of time dissemination. I intend to add a section to the sagnac effect article that discusses the underlying connection to the Twin paradox. I love the Usenet Physics FAQ meta-discussion of the Twin paradox. I don't think it can be surpassed. --Cleon Teunissen | Talk 18:53, 12 Apr 2005 (UTC)


 * I recommend that you read Basic Concepts in Relativity by Resnick and Halliday, which is a fine general introduction to the topic and discusses the relation of classical electrodynamics and special relativity. In general, there are many excellent textbooks out there on these subjects, and the online material is usually only a pale shadow of what you can find in print.  Online material can also be distorted because there is no editorial filter to prevent people from writing about subjects that they only marginally understand; caveat lector. &mdash;Steven G. Johnson 21:35, Apr 12, 2005 (UTC)

Is it correct to talk about EM interaction with non-charged matter
You wrote: the equations can include interactions with non-charged matter as well (e.g. spin effects), although in any case epsilon and mu have to come from experiment (or quantum theory) and aren't given by ME
 * Interesting point. In classical (pre-quantum) mechanics there is no spin, any magnetic moment is associated with moving charges. QED basically shows the same for the magnetic momentum of electron, especially for amomal one.
 * My only point was to stress the fact that not any kind of matter will interact with EM fields. The property which differentiates kinds of matter is called charge. Well, particles usially have magnetic momentums... For me is better to think about momentims as caused by moving charges (in QFT terms) then to talk about EM interaction with non-charged matter. --GS 23:00, 27 May 2005 (UTC)


 * Every kind of matter interacts with EM fields. It's just that some kinds interact more strongly than others.  =)  (Of course, some things like the dipole moment of a neutron are predicted to be so weak that they still haven't been observed experimentally.)  (Even classically, note that &mu; represents an interaction with a material where there need never be any net charge, although normally one has microscopic + and &minus; charges of course.)  All in all, I think it's better to keep the introduction to the article general, and leave such details for later.  &mdash;Steven G. Johnson 18:31, May 28, 2005 (UTC)

Greetings
Hi Steven. I think I intersected with you before, a bit higher on this page. But now I also realized I met you in person, this June at Snowbird. The world is a small place. :) Oleg Alexandrov 03:24, 19 July 2005 (UTC)


 * Thanks for the note, Oleg, I hadn't made the connection at Snowbird! &mdash;Steven G. Johnson 03:38, July 19, 2005 (UTC)

Re: Inline Citations
rv long-winded additions that are redundant and/or questionable (e.g. simple bracketed URL references are already described and are somewhat suboptimal; and reference templates are controversial))

OK then, you shot down my solution to this problem, so you come up with a solution to it. TomStar81 04:40, 19 July 2005 (UTC)


 * Um, the Cite sources already describes how to do inline citations. Three ways, in fact: Harvard referencing, bracketed URL links (somewhat suboptimal), and footnotes (somewhat controversial).  &mdash;Steven G. Johnson 04:48, July 19, 2005 (UTC)

Steven - (as the one who recommended Tom merge his tutorial into that page) I agree that the additions weren't perfect - you're right that they are a bit verbose - but I think that they could be pruned down to something more concise rather than simply reverted. &rarr;Raul654 04:43, July 19, 2005 (UTC)


 * Perhaps he should have proposed his additions in the Talk page first? &mdash;Steven G. Johnson 04:48, July 19, 2005 (UTC)


 * Sorry about my earlier comment; its late here, I am tired, and I tend to be more sensative to what I percive as nasty comments to me under those circumstances. Please accept my apology if I offended you, that was not my intention. As for you suggestion about the talk page, I can go for that, and about you comment on inline citations being already on the cite sorces page, that really wasn't any help to me when I addressed the inline ciation issues for the page USS Missouri (BB-63). The inefeciency of the cite sorces page was the motevation behind me creating the Inline Citation page. TomStar81 04:55, 19 July 2005 (UTC)


 * I'm not offended, I just really don't understand the problem you are trying to solve&mdash;what information do you think is missing from the Cite Sources page?  It clearly recommmends that you should add complete reference info after ==References== and in addition (when needed) add inline pointers via (Author, Year) Harvard-style referencing.  It also describes bracketed-URL references and footnotes.  If you want more detail on bracketed-URL links, see Manual of Style (links) (I've added a link to this to Cite Sources). &mdash;Steven G. Johnson 05:15, July 19, 2005 (UTC)

PS. Please do not check the "This is a minor edit" box for major additions like this. You should only check that box for things like grammar/spelling/punctuation fixes and adding wikilinks. &mdash;Steven G. Johnson


 * I guess the problem is that there are no tutorials or explainations for the placements of Inline Citations off the Cite Sorces page that make sense. I suppose what I wanted was to created a page that explained how to cite sources directly from the encyclopedia page in stead of having to scroll down to the reference section. Perhaps if we retitled the page something like Wikipedia: Inline Citation Placement Tutorial or something like that, then we might more closely hit what I was aiming to fix. TomStar81 03:15, 21 July 2005 (UTC)
 * PS- sorry about the minor edit, since most of my editions are minor edits I often forget to uncheck the minor edit box for major edits. 'my bad.


 * The problem is that you don't cite sources directly from the page as opposed to scrolling down to the References section&mdash;you seem to fundamentally misunderstand the citation guidelines. The only exception is the bracketed URL style which is already described...but this style is deprecated compared to Harvard (author, year) pointers + full citation information (i.e. title/author/year, not just the URL) in the References section.  &mdash;Steven G. Johnson 04:13, July 21, 2005 (UTC)


 * Why don't we just delete the page and be done with it. I assume that the information presented in it is not factual, and there doesn't seem to be any place for it on Wikipedia. Futher discussion about it would most likely resulted in you and I wasting are time trying to resolve the issue. In the extremely rare chance we wind up needing the page again someone else can always rewrite it, but at this point I think it best just to forget about merging it and move on. TomStar81 05:34, 21 July 2005 (UTC)


 * Better, replace it with a redirect to Cite Sources. &mdash;Steven G. Johnson 05:53, July 21, 2005 (UTC)

Linux
Many of your recent edits to the article Linux are pushing POV.

&mdash;Pengo 02:29, 18 August 2005 (UTC)


 * Um, realize that the old version of the intro was agreed upon after much discussion. Or are you referring to some other edit? &mdash;Steven G. Johnson 02:59, August 18, 2005 (UTC)

"Wikipedia: Cite Sources"
I just now noticed that you reverted my edit to the Cite sources/example style article, and was wondering why. I still think that my example was better, for the reasons I gave in my description of the change: "replaced example citation with one that better illustrates all capitalization rules (don't capitalize every noun, capitalize after a colon, etc)". But you're the MIT professor; what'd I do wrong? --zenohockey 17:37, 31 August 2005 (UTC)


 * The only additional capitalization rule that your change illustrated was capitalizing words after a colon, and I thought the old example was more entertaining.

Boston!
I'm trying to round up people interested in having Wikimania in Boston next year... see User:Sj/WMB6 :-) +sj  +

Fourier transform
Hi Steven. You removed my section on involutory fourier transform, claiming that it is well known and that it belongs to the DFT article. However it is not found in the DFT article or elsewhere. Where is it well known ? Bo Jacoby 06:54, 22 September 2005 (UTC)


 * I added it to the discrete Fourier transform article. I also expanded the DFT article to give several well-known tricks to compute the inverse DFT from the forward DFT&mdash;what you called the "involutary transform" is an expression of a standard conjugation trick.  In fact, it is actually related by a factor of 1+i to the discrete Hartley transform, which is well known to be involutary.  On the other hand, I can't find outside use of the term "Involutary Fourier Transform" (or the corresponding expression) so I don't think we should highlight this particular term as if it were widespread.  Moreover, conceptually it doesn't really change the features of the transform, it is just a consequence of the fact that the forward and inverse transforms are so closely related. &mdash;Steven G. Johnson 15:30, 22 September 2005 (UTC)

'This is a minor edit'
There's a checkbox labeled 'This is a minor edit' above the 'Save page' button. Just so you know. :p &brvbar; Reisio 03:42, 24 September 2005 (UTC)


 * I take it back - good old MediaWiki must've just decided to not show me the m's that time. &brvbar; Reisio 04:03, 24 September 2005 (UTC)

Hi Steven,
About time we start talking about the Cite sources reverts I think. I start a topic at Wikipedia talk:Cite sources --Francis Schonken 19:26, 24 September 2005 (UTC)

Barnstar
Fir e  Fo  x  17:24, 5 October 2005 (UTC)


 * Thanks! &mdash;Steven G. Johnson 17:38, 5 October 2005 (UTC)

Dispersion
I have a question for you at talk:dispersion (optics). --Bob Mellish 18:09, 5 October 2005 (UTC)

Fourier Series
Thanks for your work on Fourier series! &mdash;User:Mike1024

EMF
What's wrong with having the symbol for EMF in the article? porges 22:24, 10 October 2005 (UTC)
 * Nothing, but there is no reason to put it in a large font. In any case, the most common symbol I've seen is a script $$\mathcal{E}$$, not a Roman-font E.  &mdash;Steven G. Johnson

please vote
Hello. Please vote at Featured list candidates/List of lists of mathematical topics. Michael Hardy 01:18, 15 October 2005 (UTC)

Vibronic coupling
Out of curiousity, have you done any research in vibronic coupling in the context of solid state photonic systems? --HappyCamper 01:23, 15 October 2005 (UTC)


 * I'm not entirely sure what you mean. "Vibronic coupling" usually refers to electronic states, as I understand it (although I don't come across the term much). The photonic analogue would be acousto-optic interactions, which I've run into a few times but have never done serious research on. &mdash;Steven G. Johnson 04:44, 15 October 2005 (UTC)

Image tagging
Hi. I'd uploaded Image:Bombaycitydistricts.png on 2005-02-23, and released it under GFDL. On 25 March, you changed the licence to unverified ) with the comment how is this GFDL?. Today, I received a message saying that it was going to be deleted. I consider it pretty rude that you changed the licence from GFDL to unverified without consulting me. Please do not repeat this in the future. Regards, =Nichalp «Talk»=  18:53, 17 October 2005 (UTC)


 * (a) Common Wikipedia practice does not require the initial author of a page to be explicitly notified for every change, primarily because (b) it is assumed that most people add pages they care about to their Watchlist and (c) the image would't be deleted without querying your talk page first, since (d) is only a marker that sufficient source information was not given&mdash;and it is important to quickly tag questionable images even if someone (me) doesn't have time to immediately go and initiate a conversation with the uploader.  This is the whole point of the robot that posted the notification on your Talk page&mdash;you were notified (eventually).  &mdash;Steven G. Johnson 19:38, 17 October 2005 (UTC)


 * Common Wikipedia practice does not, but what you did does require the author to be notified to clarify the issue, instead of having the issue pending. If the case is geniune, WP has a free image immediately. b) Images are hardly put on ones watchlist, since they rarely attract comments, and new uploads over it do not appear in them. If I upload 50 images, IMO, I'd be adding 50 white elephants to my watchlist. I was notified eventually, but the "unverified" tag remained for 6 months! I don't thinks its too much of a hassle to inform the uploader, especially since you're already taking the trouble of retagging the image. It also tells a newbie to be more cautious with their images, and you'd probably end up with less work in the future from their side. I too do the same work you do, but I do inform all uploaders about their image status. The map in question was one of my first drawings, so therefore the lack of information. (Most of my images these days are well sourced and are in commons.) =Nichalp «Talk»=  20:15, 17 October 2005 (UTC)


 * Oh, I agree that it is ideal to tag + notify immediately, and I do this when I have time, but this is a non-ideal world with time constraints...it is preferable to tag and wait for the eventual robot notification vs. not tagging at all. Having an image tagged as "unverified" for a few months, after all, doesn't really impact its usability to readers.   I think you're going overboard in complaining about "rudeness," though.  &mdash;Steven G. Johnson 20:24, 17 October 2005 (UTC)

Featured list candidates/List of lists of mathematical topics
Hello. Several of your suggestions after your vote have been addressed in recent edits to this page. Someone added introductory paragraphs to all (or nearly all?) sections of the list. This raises the question of whether your vote or your comments on that page should get updated. Michael Hardy 00:39, 23 October 2005 (UTC)

Hollow earth
I hope you didn't feel like you were being played around with. I do wonder about these things. My dad taught physics and college. I am sometimes thingking of making this a thesis in Masteral Physics even if it is outrageous or goes against the mainstream.--Jondel 05:29, 30 November 2005 (UTC)

Transform vs transformation
As our Fourier guy, you might want to comment on Talk:Laplace transform on whether the process is called Laplace transform or Laplace transformation. -- Jitse Niesen (talk) 17:19, 13 December 2005 (UTC)