User talk:Pdn~enwiki

Tesla Coil

Hi! I noticed your edit on the Tesla coil page about its use in Kirlian photography. I've never heard of electrophotography made with a TC. TV HV flybacks are often used however. Could you please provide a source showing the (non-marginal) use of TC for that kind of art? Thanks in advance. Glaurung 07:28, 24 Jan 2005 (UTC)

Glaurung - I am not sure how to reply - clicked on some things but found no e-mail for you.

Anyway, I will reply here. The "Kirlian photography" page in Wikipedia itself that I linked to mentions Tesla coils. It is relatively easy to probe the Web for such connections. For example, some links I got are given below but there are dozens. Just take any good ole search engine and stick in Kirlian and Tesla. Example:

[1]

[2]

[3]

[4]

[5]

Hello again. On Wikipedia, we don't use e-mail. When someone writes something on your talk page, you reply either on your own talk page, or on her/his talk page if you want to be sure the other person noticed your reply. So back to the subject of interest. On all the page you listed the one concerning the use of a Tesla coil for Kirlian photography all linked to the same webpage [6]. There, two example are given : A "commercial" voltage source which is said to be a TC, but which probably is only a flyback, and pictures of the streamers of a TC, which is not really Kirlian photography (many coilers take pictures of the output of their coils, but the term Kirlian photography is never used). Anyway, I am not really convinced of the real use of TC for Kirlian photography (I mean for the pictures of corona discharge on objects), except maybe a few marginal examples. But we might as well keep its mention in the TC article. Glaurung 07:56, 25 Jan 2005 (UTC)

• I moved your comment about Kirlian photography in the popularity section. I think it stands better on its own than squeezed in the hazard paragraph as it was before. Glaurung 08:12, 25 Jan 2005 (UTC)

---

Fine - you are clearly the expert here and delete or move as you please. I do not know how to access your talk page - you could reply here or to pdnoerd@yahoo.com if you like to explain the steps, if you have time. When I click on your link I only see to beware of you.

What we have here is probably a situation where popular names are not scientifically accurate. For example, long focus lenses are popularly called "telephoto" lenses, but the latter term should be reserved for a design that compresses the length of the barrel by combining positive and negative components, with the negative nearest the film plane - i.e. it's kind of like a Galilean telescope that is focused so as to produce converging ray bundles rather than parallel ray bundles. And then, today they speak of using "the carrot or the stick" as if to possibly hit the donkey if the carrot doesn't work, but the original cartoon had a less punitive usage of both; an occupant of the towed wagon was to hold the carrot out in front of the donkey using the stick and some string, urging the animal painlessly, though tantalizingly, forward.

It was quite interesting to learn from your entry (I assume it was at least mostly yours) that Tesla coils can't be treated as lumped element circuits. I looked at more references on that, as well.

Peter

• Here is how you can access a user talk page : If you click on a user link, you arrive on its page where he/she describes him/herself (In my case I only put a link to the real Glaurung). But at the top of the page, as for any Wikipedia page, you have the tab named discussion, which is the user talk page. But you can directly access someone's talkpage with the syntax : User_talk:Glaurung (for example).
• About Tesla Coil : The article on Wikipedia is not mine at all, I've been watching it for quite some time, but I didn't edit it, except a few minor changes. I am keeping an eye on it because a user promised a complete rewrite, but he somehow disappeared. As for lumped element, you can find a lot of information on the impossibility to model Tesla Coil with lumped element if you want to get accurate results on the web. See for instance [7] Glaurung 07:32, 26 Jan 2005 (UTC)

---

Hi. I am probably the wrong person to ask, since this is not my specialty - try one of the actual contributors to the article, which you can see at http://en.wikipedia.org/w/index.php?title=Support_%28mathematics%29&action=history . I'm sure that those who have contributed extensively to the article would be able to answer your request. Don't forget the talk page of the article, which is just suited for these purposes.

If you have any other questions about how things work on Wikipedia, don't hesitate to ask me. Dysprosia 04:44, 20 Feb 2005 (UTC)

---

You can sign by typing four tildes, ~~~~, to get Dysprosia 23:36, 20 Feb 2005 (UTC)

Hang time

"Hang time" is the amount of time a punt stays in the air, allowing the kick coverage team time to get downfield and surround the kick returner. More is better. The best NFL punters get hangtime of over 4 seconds -- 4.3 or 4.4 seconds is considered very good.

Obviously hang time is the result of a high powerful kick. Yale Lary was one of the best.

Tesla Coil

Hi! I noticed your edit on the Tesla coil page about its use in Kirlian photography. I've never heard of electrophotography made with a TC. TV HV flybacks are often used however. Could you please provide a source showing the (non-marginal) use of TC for that kind of art? Thanks in advance. Glaurung 07:28, 24 Jan 2005 (UTC)

Glaurung - I am not sure how to reply - clicked on some things but found no e-mail for you.

Anyway, I will reply here. The "Kirlian photography" page in Wikipedia itself that I linked to mentions Tesla coils. It is relatively easy to probe the Web for such connections. For example, some links I got are given below but there are dozens. Just take any good ole search engine and stick in Kirlian and Tesla. Example:

[8]

[9]

[10]

[11]

[12]

Hello again. On Wikipedia, we don't use e-mail. When someone writes something on your talk page, you reply either on your own talk page, or on her/his talk page if you want to be sure the other person noticed your reply. So back to the subject of interest. On all the page you listed the one concerning the use of a Tesla coil for Kirlian photography all linked to the same webpage [13]. There, two example are given : A "commercial" voltage source which is said to be a TC, but which probably is only a flyback, and pictures of the streamers of a TC, which is not really Kirlian photography (many coilers take pictures of the output of their coils, but the term Kirlian photography is never used). Anyway, I am not really convinced of the real use of TC for Kirlian photography (I mean for the pictures of corona discharge on objects), except maybe a few marginal examples. But we might as well keep its mention in the TC article. Glaurung 07:56, 25 Jan 2005 (UTC)

• I moved your comment about Kirlian photography in the popularity section. I think it stands better on its own than squeezed in the hazard paragraph as it was before. Glaurung 08:12, 25 Jan 2005 (UTC)

---

Fine - you are clearly the expert here and delete or move as you please. I do not know how to access your talk page - you could reply here or to pdnoerd@yahoo.com if you like to explain the steps, if you have time. When I click on your link I only see to beware of you.

What we have here is probably a situation where popular names are not scientifically accurate. For example, long focus lenses are popularly called "telephoto" lenses, but the latter term should be reserved for a design that compresses the length of the barrel by combining positive and negative components, with the negative nearest the film plane - i.e. it's kind of like a Galilean telescope that is focused so as to produce converging ray bundles rather than parallel ray bundles. And then, today they speak of using "the carrot or the stick" as if to possibly hit the donkey if the carrot doesn't work, but the original cartoon had a less punitive usage of both; an occupant of the towed wagon was to hold the carrot out in front of the donkey using the stick and some string, urging the animal painlessly, though tantalizingly, forward.

It was quite interesting to learn from your entry (I assume it was at least mostly yours) that Tesla coils can't be treated as lumped element circuits. I looked at more references on that, as well.

Peter

• Here is how you can access a user talk page : If you click on a user link, you arrive on its page where he/she describes him/herself (In my case I only put a link to the real Glaurung). But at the top of the page, as for any Wikipedia page, you have the tab named discussion, which is the user talk page. But you can directly access someone's talkpage with the syntax : User_talk:Glaurung (for example).
• About Tesla Coil : The article on Wikipedia is not mine at all, I've been watching it for quite some time, but I didn't edit it, except a few minor changes. I am keeping an eye on it because a user promised a complete rewrite, but he somehow disappeared. As for lumped element, you can find a lot of information on the impossibility to model Tesla Coil with lumped element if you want to get accurate results on the web. See for instance [14] Glaurung 07:32, 26 Jan 2005 (UTC)

---

Hi. I am probably the wrong person to ask, since this is not my specialty - try one of the actual contributors to the article, which you can see at http://en.wikipedia.org/w/index.php?title=Support_%28mathematics%29&action=history . I'm sure that those who have contributed extensively to the article would be able to answer your request. Don't forget the talk page of the article, which is just suited for these purposes.

If you have any other questions about how things work on Wikipedia, don't hesitate to ask me. Dysprosia 04:44, 20 Feb 2005 (UTC)

---

You can sign by typing four tildes, ~~~~, to get Dysprosia 23:36, 20 Feb 2005 (UTC)

Hang time

... is the amount of time a punt stays in the air, allowing the kick coverage team time to get downfield. More is better... 4.3 or 4.4 seconds is excellent. Yale Lary was one of the best.--Pmeisel 03:54, 6 Mar 2005 (UTC)

Polarization of light

Please see my reply to you on my talkpage. You may also want to work on polarization of starlight, which I created using your comment to me. -- The Anome 15:36, Mar 17, 2005 (UTC)

Camel slogan

Hi Peter,

I have no doubt that your edit to the Camel cigarettes slogan in N.W. Ayer & Son is accurate... but one of the listed references includes that slogan, minus the "mild, mild" ([15], see #46). Is there anywhere you could reference your change from? A google search of "I'd walk a mile for a Camel" comes up with 933 hits, but "I'd walk a mile for a mild, mild Camel" only has 7. Not to say that's definitive, but if we're to contradict a listed source, we should have another source that shows the version you are familiar with. Thanks! - Bantman 06:32, Mar 18, 2005 (UTC)

Hi Peter, thanks for looking into this. From [16], it looks like the "mild, mild Camel" you remember was part of the radio jingle, but not necessarily the slogan itself. Regardless, it appears that N.W. Ayer & Son was responsible for the original slogan "I'd walk a mile for a Camel", and if there are other variations, maybe those too... I think the article as it now stands is accurate for as much as it is trying to say.

Also, when posting a comment to a user's page, it is preferable to post to the user's "discussion page" (i.e. "talk page") rather than the main user page. Thanks! - Bantman 22:28, Mar 21, 2005 (UTC)

Inventor of the Knudsen number

Do you think the Knudsen number was originated by the Jens Martin Knudsen you knew? There is no link between pages. Pdn 04:48, 18 Mar 2005 (UTC)

I don't know; I tried googling, but I can't find any references as to who invented the Knudsen number. Thue | talk 09:20, 18 Mar 2005 (UTC)

I received a reply indirectly from Denmark that it must have been a different Knudsen - possibly Swedish Pdn 21:07, 28 Mar 2005 (UTC)

Polarization in astronomy

I've nominated polarization in astronomy for Wikipedia:Collaboration of the week. COTW articles become the centre of community collaboration, and generally greatly improve in quality as all the experts come out from their hiding places to polish that week's collaboration article to a telescope-mirror like sheen. To qualify, it needs votes... Please vote for it! -- The Anome 17:16, Mar 28, 2005 (UTC)

Monsieur Hulot

I think you misinterpreted my remark about pronounciation. Its not that French is hard to pronounce, it is that "Mounsieur Hulot" is French, and so has a silent H, but holiday is English so it has a spoken H, which makes it hard. I think thats why the US release didnt have that title... Justinc 10:27, 9 Apr 2005 (UTC)

Wikipedia:Naming conventions (military units)

Hi. My watchlist shows that you were interested enough to work on a military-topic article, so I wanted to make sure you were aware of the new Wikipedia:Naming conventions (military units) project, in case you didn't see any of the announcements. — B.Bryant 22:33, 17 Apr 2005 (UTC)

Why did you want to have Huscarl separate from Housecarl???

Dear Pdn, would you please tell me in what way huscarls were different from housecarls?--Wiglaf 20:48, 14 May 2005 (UTC)

I meant that after I had made the Huscarl into a redirect to Housecarl you restored it.--Wiglaf 21:23, 15 May 2005 (UTC)

Against the Anti-Science Agenda Setters

Just wanted to say thank you for your comments on my talk page. I will be keeping a close eye on the creationism and 'intelligent design' articles in future to make sure they maintain their critical perspective, and that they do not succomb to agenda setters such as salva. Thanks for the encouragement, and I'm really glad that people such as yourself are on wikipedia sharing your knowledge freely with other people just for the love of it :-) Aaarrrggh 00:03, 18 May 2005 (UTC)

Regarding covariant and contravariant

I read your comments on my talk page: perhaps the best way out of this is to make both covariant and contravariant into disambiguation pages, so we can treat the two meanings differently. Perhaps two main articles, Contravariant and covariant components and Contravariant and covariant transformations, with covariant transformation etc. etc. pointing to the right places, too? -- The Anome 08:23, May 20, 2005 (UTC)

Hi, I added some paragraphs to covariant to define the other meaning of covariant that you were alluding to, but I did not at first pick up on. Does this look more reasonable now? linas 01:37, 23 May 2005 (UTC)

Re: Easy Street

I think an "Easy street (disambiguation)" page would be a good idea. The idiom itself ought to appear on Wiktionary, but that does not mean that there could not be an encyclopedia article with regards to the history of the term, etc. Related movies and other works almost certianly deserve their own encyclopedia articles (and yes, an article regarding the movie would capatalized). Thanks for your commment. Ryan Prior 18:31, May 28, 2005 (UTC)

I often feel the same way about science on Wikipedia. I've been expanding some scientific articles in my areas of knowledge, but I don't really touch the controversial ones - like you say, it takes a lot of time and stress to fight the promotion of ideas like intelligent design. However, being a student of physics (we all are, right?), just think of this - matter is so very, very complex that, on a detailed level, its behaviour is mind-boggling. Does that ever make you step back for a second and say, "There is no way this all just happened randomly!" I'm not a proponent of intelligent design and I wouldn't mix creationism and science, but if science one day finds out that some god-like creator really did make everything, I wouldn't be too surprised. =D Keep up the good work. Ryan Prior 23:27, May 28, 2005 (UTC)

A J Ayer

Thanks for pointing out my error. I didn't have extensive familiarity with him, but was somewhat aware of his philosophic standing in Britain (I did most of the Gifford lectures article, and he gave one series). Perhaps it slipped through as a confusion of the possessive form. Anyway, I suspect only someone above administrator, maybe even a steward could edit the history. It is like an audit trail and thus should have restricted access.

PS. I see you worked on the Tesla article. I haven't read it yet, but find him fascinating. I did read Cheney's biography of him some years ago, and while I never got around to building a Tesla coil, I did get a 15 kV transformer and built a Jacob's ladder while in high school. Very cool. And I have done some work on commercial lightning protection. --Blainster 23:41, 29 May 2005 (UTC)

αβγ

Are you sure about the Alpher, Bethe and Gamow paper? That seems to contradict Gamow's account. He said that Bethe did not contribute until the final stages of preparation of the paper. Of course, it could be apocryphal, but every account I've seen or heard gives the same story, although I've never read Alpher's accounts. –Joke137 22:43, 30 May 2005 (UTC)

Wow, thanks for doing all this checking in response to my little comment!–Joke137 18:46, 2 Jun 2005 (UTC)

Now you've really piqued my curiosity. –Joke137 19:16, 4 Jun 2005 (UTC)

welding

Here's what the article says now about safety: "Additionally, the brightness of the weld area leads to a condition called arc eye in which ultraviolet light causes the inflammation of the cornea and can burn the retinas of the eyes. Goggles and helmets with dark face plates are worn to prevent this exposure, and in recent years, new helmet models have been produced that feature a face plate that self-darkens upon exposure to high amounts of UV light. To protect bystanders, transparent welding curtains often surround the welding area. These curtains, made of a polyvinyl chloride plastic film, shield nearby workers from exposure to the UV light from the electric arc, but should not be used to replace the filter glass used in helmets". In what ways do you think this should be improved?

Sorry - the welding article is for the most part excellent on safety; it is the Electric arc piece that fails to warn. I suppose that can be left alone, but I am not expert on Wiki policy - perhaps there ought to be a brief note there referring (a second time) to welding. It is up to you. There is one missing safety item, however (again my eye may miss something). When using or storing gases under pressure in typical metal cylinders, it is important to strap them to the wall, or a steel or strong wood column, or the like. If such a bottle falls over, it can suffer its neck breaking off, in which case it becomes a rocket that can be very destructive. I have heard of a case where an oxygen cylinder in a laboratory went through a thick cinderblock wall, reversed on striking an obstacle in the next room, and returned through a different part of the wall. Maybe such a warning belongs in a separate article on compressed gases however (???) I am too busy or lazy to learn enough wikilore to know where to put such a warning.Pdn 18:39, 1 Jun 2005 (UTC)

As for the oxygen/acetylene thing, is not the source of the energy in gas welding the combustion of acetylene in oxygen? They are both required for combustion to take place, and thus, the mixture of the two is what provides the flame and therefore the energy for welding. That's what I'm trying to say in the lead of the article when I say that an oxygen-acetylene gas mixture provides the energy for welding. Do you disagree? --Spangineer ∞ 18:05, Jun 1, 2005 (UTC)

The mixture is not a mixture until inside the nozzle. I suppose it is insane to assume a beginner would find a way to premix the gases, put the mixture through a hose and nozzle, and light it where it emerged, but if there is a fool born every second (even before the population explosion) there is an idiot born every millisecond. I mean, even kids read this kind of stuff. Hope you do not find my edit unacceptable. Thanks for all your responses. Pdn 18:39, 1 Jun 2005 (UTC)

What if we simply said "acetylene gas" – that would eliminate the gas mixture thing, and since it should be generally known that hydrocarbons combust in air, we don't need to include oxygen. I'd prefer not to have it say "oxyacetylene torch" because for one thing, the torch isn't made out of oxyacetylene, things like "electric arc" and "ultrasonic" refer to the actual physical/chemical/whatever things that are providing the energy, not the equipment that directs the energy. So to be consistent, I think it's best to refer to the actual substance, not the tool used. --Spangineer (háblame) 19:35, Jun 1, 2005 (UTC)

Well, you're right on the "made of" thing; that was rather silly of me =). I'd still much prefer a parallel structure (i.e. with "acetylene" or "oxygen-acetylene gas mixture"), but I suppose I'll defer on this one. Also, the page oxyacetylene torch redirects to oxyacetylene, and looks like it's trying to be the article on oxyfuel welding, not the tool itself. I've half a mind to just redirect the whole thing to oxyfuel welding and forget it. But if that was done, that link to oxyacetylene torch would be pretty useless, since it would go to the process itself, which is entirely unlike all the other links in that sentence in the lead of the welding article. --Spangineer (háblame) 11:56, Jun 2, 2005 (UTC)

Heh heh. I just realized something pretty funny. Sometimes, the fuel used isn't acetylene. So really, all this is a waste of our time. I think it would be better to include all gas welding procedures by just changing the "oxyacetylene torch" part to "flame". Nice, simple, consistent with the other things in that sentence, and no worries about when and where the gases mix, etc. I like this idea alot, but I won't make the change until you comment. Sorry to keep kicking this horse that probably should have died awhile ago =). --Spangineer (háblame) 19:25, Jun 2, 2005 (UTC)

Polar Motion

Hey Pdn. Sorry for being so bold about removing the phrase but remember this is an encyclopedia; criticising a document in a rather informal manner on an article that is not directly related to the document itself is not fitting. Instead, it is better to provide an acurate document and explain that one. For example, in an article about mergesort, you wouldn't put an incorrect diagram and say "this is a bad diagram of how mergesort sorts a given input". Phils 15:30, 5 Jun 2005 (UTC)

Ok, I've also sent the IERS webmaster a mail to see if we can just put the picture over here, so people can check it while reading without switching windows or tabs. Phils 15:39, 5 Jun 2005 (UTC)

edit war on geodesics

Glad you liked that comment on tangent vectors of material particles being timelike. I'm not sure how to do that "revert to version" thing, but I'll find out just now and get back to you soon Mpatel 17:04, 6 Jun 2005 (UTC)

reverting pages

Ok , I've discovered how to do that "revert to version" thing :

• Click on history.

• Click on the time and date of the version you want to revert to (not 'cur' or 'last').

• Click on edit this page.

• Once you see the warning at the top of the page, click save.

• Voila !

I found all this from the main page: click on 'Help/contact us' then 'How to revert a page'. Hope that helps. Mpatel 17:16, 6 Jun 2005 (UTC)

Geodesics

Sorry about the geodesics revert, maybe I was having a bad day. I admit I misread the statements about timelike; a different set of neurons popped in my head. On the other hand, I completely failed to understand what you were trying to say about the spacelike geodesics .. that they're "graphs of filaments"? My brain fritzed at that point.

Anyway, peace; although maybe its time to start a new article, say, geodesic (general relativity) ? Since the current geodesic article is getting long, and the GR stuff is kind of buried at the bottom. There's lots of interesting things that can be said about GR geodesics, and that article isn't really structured to say them. The current article could continue to stand as the "math formalities" of geodesics. linas 23:42, 6 Jun 2005 (UTC)

Hi, re; your discussion, I know what killing vector fields are; if you look, you'll notice I made the last few edits to that article (even if they are trivial edits). I have never heard the term "filament" applied in a geometry context before, be it gravitation or anywhere else in math/physics; except on the TV show "Star Trek" where I think it meant "cosmic string". I just looked in Misner-thorne-wheeler, it doesn't list "filament" in the appendix. The closest I can find on wikipedia is Filament_(astronomy). So when I saw the word "filament" I assumed it was some overly-eager star-trek fan and reverted the edit.

(It didn't help that I misread your statements about timelike geodesics, which I misread as world-lines. I misread the passage as saying that massive particles could have world-lines that aren't timelike. For that I apologize).

If you do re-edit, be sure to take some time in explaining what a "filament" is; I really haven't tripped across this concept before (and I have heard about a lot of things). It might be worth an article of its own if its dense enough. And do consider making geodesic (general relativity) a distinct article. linas 05:07, 7 Jun 2005 (UTC)

Evolutionism

The term "evolutionism" was used by supporters of evolution long before it was used by modern Creationists, and the fact that it makes modern scientists uncomfortable (in part because of its use by Creationists) is well noted on the page. To say that it is simply a term made up and used by Creationists is not true. In modern language it clearly implies a notion of belief, but the negative connotation only comes because many people today automatically disassociate belief with facts. (I think this is falsely done -- we all "believe" in our facts at some level, even if some people have better reasons to believe than others!) Now I'm not sure what your POV problem is about -- that it doesn't mention more strongly that some people now oppose the usage of the term? That a history of evolutionary thought be put under the heading? Or what? --Fastfission 15:35, 9 Jun 2005 (UTC)

Hi there. The page at http://evolutionist.biography.ms/ says at the bottom of it, "The Wikipedia content included on this page is licensed under the GFDL" -- that is, it is a mirror of the Wikipedia page (something which is allowed with Wikipedia content, but can be very confusing sometimes!). I'm not sure I understand your problem with the external links -- two of them are pro-evolution sites (Talk.Origins and NCSE), another is a court ruling, and the only Creationist articles are well-labeled as such (so nobody will get confused as to their source, validity, etc.). --Fastfission 20:48, 9 Jun 2005 (UTC)

A few other quotes:

"Nothing can give a better idea (in small compass) of the growth of Evolutionism and its position at this time, than a quotation from Mr. Huxley* :— "[17]

(Francis Darwin, Life and Letters of Charles Darwin)

"In France, the influence of Elie de Beaumont and of Flourens-the former of whom is said to have "damned himself to everlasting fame" by inventing the nickname of "la science moussante" for Evolutionism,* -to say nothing of the ill-will of other powerful members of the Institut, produced for a long time the effect of a conspiracy of silence; and many years passed before the Academy redeemed itself from the reproach that the name of Darwin was not to be found on the list of its members."[18]

(Ibid)

"It is satisfactory to hear so capable an anatomist, and so embittered an opponent of evolutionism, admitting even the possibility of either of his first propositions."[19]

(Charles Darwin, The Descent of Man)

I just came across those searching through the text on the British Library's collection of Darwin's works. What seems worth wondering to me is not whether the term was ever used, but whether the entry should 1. be about the term itself, and 2. whether or not the information currently on the page is just a duplicate of the article History of evolutionary thought. I am feeling that any useful information should be merged with the latter article and the Evolutionism article should be somewhat more devoted to the term, or redirect to the "history" article and have an entry at Wikitionary. Anyway, I don't care very much abotu this particular dispute, there's no need to argue with me directly on it... --Fastfission 20:59, 9 Jun 2005 (UTC)

Physical space

Yes, I completely agree that the writer kinda lost hold of his goggles when he moved into relativity. This can be solved by deleting that crap from the article. I think it's a good topic for an article and undoubtedly one day could be a very good one. I may tackle it myself. I tend to adopt the stance that an article shouldn't be deleted if it's salvageable. Meanwhile we can delete crap, stick "totally disputed" stickers etc on it, and wait for someone to come and clean it up (or do it ourselves). There are others who would say better to delete it and start again, but there may never be an "again". it's salvageable so I'll give it time. --Tony Sidaway|Talk 18:01, 14 Jun 2005 (UTC)

Quite large parts of Wikipedia were written by people only identified by an IP number. Scary but true! :) --Tony Sidaway|Talk 18:14, 14 Jun 2005 (UTC)

Re: Reflections of relativity

Pdn -

You don't like that reference, and I think that you have been dealing with it a lot more than I have. It seems to be a set of essays and not really a single coherent work anyway. My advice it to delete it and see it anyone comes to its defense. The other option is to drop Chris Hillman a line and see if you can get him to rule on it. My guess is that he will either yank it or justify it's presense after that.

As for black holes: My point is that the status of these so-called black holes is not a given. There is a counter-current against them being black holes, and against the black hole concept itself. However, new physics is required for these objects to not be black holes. Just be aware of the facts in the last two sentences. For NPOV reasons, I am largely staying away from black hole articles. My focus instead is on the foundations of GR, where I think that it is sound and on which any new physics will be built. --EMS | Talk 02:51, 17 Jun 2005 (UTC)

P.S. Einstein's view of the black hole was "a good theory does not behave like that. This is a good theory. Therefore it does not behave like that". That Einstein was wrong in that regard was proven two years after his death. --EMS | Talk 02:51, 17 Jun 2005 (UTC)

FYI - I decided to place a more detailed response to your response to this in my talk page, and start keeping this thread together. --EMS | Talk 04:16, 18 Jun 2005 (UTC)

Reflections on relativity by Kevin Brown

Hi Pdn,

My name is Cleon Teunissen. I would like to support inclusion of Reflections on relativity among the references of the General Relativity article. I agree that Kevin Brown's treatment is idiosyncratic. It's not semi-popular, Kevin Brown uses a lot of math, and he is very detailed. Reflections on relativity is mostly an in-depth discussion of both special relativity and general relativity. In that sense it is a book about philosophy of physics (and specifically relativity) rather than a textbook.

Kevin Brown is, as far as I can tell, an especially gifted mathematician. In the early 90's he often posted essays on Usenet groups about mathematical subjects. Later he set up mathpages.com to present his work. Initially the site mathpages.com showed his name, but later he removed all mention of his name from mathpages.com

My impression of Kevin Brown is that he is exceptionally intelligent, en that he is exceptionally meticulous in his research. Check out his contributions in a Usenet discussion of the philosophy of mathematical proof.

I have done a lot of digging for information about relativity, and I do not know of any source that comes even close to the depth and thoroughness of Kevin Brown. Kevin Brown does not simplify the physics to accommodate people with little physics background, he goes for exhaustive treatment; Reflections on Relativity is clearly written for an audience of people who already have a firm understanding of relativity.

I am aware that Kevin Brown is not necessarily reporting scientific consensus, he is writing down his personal musings, so the reader must be aware that what Kevin Brown writes should not be swallowed unthinkingly. (Also, Kevin Brown discusses interpretation of relativity at length, and that is a subject on which scientific consensus does not apply, because one just cannot prove the validity of one interpretation over the other.)

Kevin brown clearly likes the format of essays, much as he wrote them in the Usenet days. On the whole my impression is that the book Reflections on relativity was from the start written to be published as a single coherent work.

For me, the reading of Kevin Brown's work was very stimulating and thought-provoking. I think it is a good reference to maintain in the references section of the General Relativity article. --Cleon Teunissen | Talk 11:23, 17 Jun 2005 (UTC)

I think that you have done more to indict this entry than an validate it. "Reflections" is under the heading "Web courses". It obviously is not a web course since it cannot be used to gain an understanding of GR. It seems to me that the question is now one of what to do with it. It cannot stay where it is. --EMS | Talk 04:29, 18 Jun 2005 (UTC)

Your recent edit in Creationism

Most scientists and educators would view such decisions as impairing the ability of people,

you begin your sentence with a logical fallacy -- Appeal to majority, to be exact. Then you are doing some wishful thinking and you're being a bit emmotional there, by writing in second person instead of third. I understand why you put the paragraph back, i just think you should rephrase it a bit more to look NPOV. Thanks :) Project2501a 22:05, 17 Jun 2005 (UTC)

MC Hawking: "The creationists want to have their bullshit taught in public class. Stephen Jay Gould should put his foot right up their ass."

Reflections on Relativity by Kevin Brown (2)

I do not find the link stale: [20]. [...] Well, there are some odd remarks:"The real content of Einstein's principles is that light is an inertial phenomena (despite its apparent wavelike nature). " Pdn 02:59, 19 Jun 2005 (UTC)

Hi Pdn,

In the context that that remark is made, it can be seen that it is refers to standard relativistic physics.

What Kevin Brown is referring to is a property of moving inertially. Here is how I understand Kevin Brown:

In a spaceship that is moving inertially, space is seen to be isotropic for acceleration of objects: if you have, say, two marbles of equal mass with a spring in between, and you release the spring so that the marbles are ejected in opposite direction, then the two marbles will be seen to move away with the same velocity as seen from that spaceship. This is isotropy of space for acceleration: no matter in what direction you apply a force to a particular object, the amount of inertia is always the same. (By contrast, in an accelerating spaceship, inertia of objects is not isotropic with respect to the accelerating spaceship.)

Parallel to that: in a spaceship that is moving inertially, space is seen to be isotropic for propagation of light. No matter in what direction you measure the speed of propagation of light the speed you find is always the same. (By contrast, in an accelerating spaceship your measuring results will be consistent with an interpration that the speed of light is non-isotropic with respect to the accelerating spaceship.)

As I understand it, it is Kevin Browns way of formulating that the following two properties always coincide: isotropy of acceleration, and isotropy of propagation of light. Kevin Brown chooses to formulate that in that form because it emphasizes the importance of the parallel of a state of moving inertially and isotropy of space. He wants to emphasize that the relativistic equivalent of Newtons third law, conservation of momentum, is a crucial axiom of special relativity.

As I said, Kevin Brown is the most thorough thinker I have encountered on the web. It's not easy, his stuff, it's not readily accessable, but I find studying it quite rewarding. Kevin Brown is exceptionally good at noticing parallels between things that reveal the typical interconnectedness of relativity. --Cleon Teunissen | Talk 14:53, 19 Jun 2005 (UTC)

Isotropy of inertia

Isotropy of inertia

You can easily detect by a variety of means that your spaceship is either accelerated or at rest in the launching dock under the influence of gravity, Pdn 22:10, 19 Jun 2005 (UTC)

Yes, that is the interesting thing about physics.

Reading your response I am once more confronted with the perennial problem of discussing physics without eye-contact, without body-language. We both have the same standard relativistic physics in mind, its just that idiosyncrasies in phrasing and expressions can lead to misunderstandings.

What I have in mind is the following: let there be three inertially moving spaceships, moving in Minkowski space, in linear formation. These three, let's call them 'the greens' have zero relative velocity, so they can set up a procedure with exchanging lightpulses to monitor that they maintain a synchronized fleet time. Say the middle ship emits (simultaneously) pulses towards each of the outer ships, and the outer ships respond on reception of each pulse. As long as the transit time of the signals remains the same the mutual distances are known to remain the same. If both the outer ships are equally far away from the center ship, then the returning pulses arrive simultaneously at the center ship.

Special relativity describes that a synchronisation procedure that uses messengers that travel at a speed slower than light will yield results that are consistent with the lightpulses procedure. If for example the ships of the green fleet use probes with atomic clocks onboard, shuttling between the ships of the green fleet to disseminate time-keeping, then the overall pattern of time dilation and other relativistic effects will be such that the outcome of the time dissemination procedure using shuttling probes will be consistent with dissemination of time with the help of lightpulses. Of course, that is all just straightforward relativity of inertial motion.

And of course, when the green fleet as a whole is accelerating in Minkowski space by using rocket engines, then measurements will not yield isotropy, and of course the greens then can assess how hard the ships are accelerating with respect to an inertial frame of reference by measuring the magnitude of the anisotropy.

Let's return the the initial quote:

Well, there are some odd remarks:"The real content of Einstein's principles is that light is an inertial phenomena (despite its apparent wavelike nature).

What Kevin Brown is referring to is straightforward, standard special relativity. He is saying: if you are in a spaceship, and you look at your onboard accelerometer and it reads zero, then invariably any measurement of the speed of propagation of light with respect to the spaceship will yield isotropy with respect to the spaceship. In other words, an inertial frame of reference has the property that inertia is isotropic and the speed of propagation of light is observed to be isotropic; those two always coincide. (Back in 1905 nobody expected those two to always coincide, that the two coincide is quite a surprise.)

Particle/wave duality

Kevin Brown observes that Minkowski space-time geometry allows aspects of particle/wave duality in a natural way. Wave-nature of light demands that light should always be seen to propagate at the same velocity through its medium, and that is exactly what is seen. Particle-nature of light demands that no matter the velocity of some foton-emitter, the emitter should always see the fotons propagating away from itself with the speed of light, and measurement are consistent with that.
Of course, the latter observation, that Minkowski space-time geometry allows aspects of particle/wave duality in a natural way is an audacious one, and it may not be a significant observation at all, who knows? But I quite like that sort of original, lateral thinking. --Cleon Teunissen | Talk 00:43, 20 Jun 2005 (UTC)

You say, "And of course, when the green fleet as a whole is accelerating in Minkowski space by using rocket engines, then measurements will not yield isotropy, and of course the greens then can assess how hard the ships are accelerating with respect to an inertial frame of reference by measuring the magnitude of the anisotropy." but it is difficult to define things so that a fleet as a whole accelerates uniformly; that's frame-dependent. And what is the use? The place to look for the problems with accelerated, rigid reference frames are references to Born-rigidity (after Max Born) and the Herglotz-Noether theorem. [21] or Saltzman and Taub, Phys Rev 95, 1659 (1954) or [22] or [23] The basic result is that a rigid body in special relativity has only three degrees of freedom (in Newtonian/Galilean theory it has 6). Anyway you can see it is a thorny problem, so to introduce it is a way to draw the reader into a thicket, and not a way to clarify anything (in my view). You might find a way around this by assuming the observers all accelerate in the same direction for an agreed time and then coast, whereupon they re-establish their separations and assure that there is no relative velocity among them. Operationally, one is already in some trouble (as always happens in relativity) with the words "agreed time," but if you make that short and follow it by a long coast, you might find a way to do it - have fun.

Returning to your idea that photons somehow differ from material particles in terms of some kind of isotropy, I suggest you look at the redshifts and blueshifts of the photons. Ignoring the problem of sensibly defining a rigid framework of accelerated observers, one still sees that the photon going in the direction of acceleration becomes redshifted in the frame of the accelerated system, while the one traveling back is blueshifted. So you can detect acceleration with photons (as Pound and Rebka did, as did Pound and Snyder).Pdn 01:11, 20 Jun 2005 (UTC)

sharing an isotropy

Returning to your idea that photons somehow differ from material particles in terms of some kind of isotropy, [...] Pdn 01:11, 20 Jun 2005 (UTC)

My understanding is that motion of material particles and photons shares an isotropy, rather than differing.

If you are in a spaceship, and you look at your onboard accelerometer and it reads zero, then invariably any measurement of the speed of propagation of light with respect to the spaceship will yield isotropy with respect to the spaceship. In other words, an inertial frame of reference has the property that inertia is isotropic and the speed of propagation of light is observed to be isotropic; those two always coincide. (Back in 1905 nobody expected those two to always coincide, that the two coincide is quite a surprise.)

It appears that you ascribe ideas to me that are opposite to my actual ideas.
--Cleon Teunissen | Talk 07:19, 20 Jun 2005 (UTC)

Avoiding ambiguities

And of course, when the green fleet as a whole is accelerating in Minkowski space by using rocket engines, then measurements will not yield isotropy, --Cleon Teunissen | Talk 00:43, 20 Jun 2005 (UTC)

[...] but it is difficult to define things so that a fleet as a whole accelerates uniformly; that's frame-dependent. Pdn 01:11, 20 Jun 2005 (UTC)

I'd like to point out that I did not stipulate that the fleet maintains Born rigidity when they start accelerating, you added that detail into the picture. I do admit that the phrasing 'as a whole' was somewhat suggestive of an intention to maintain Born rigidity. This illustrates how alert one must be to avoid all possible ambiguities, and also how alert the reader must be to avoid projecting things into a text.

My intention was to refer to the contrast: if the fleet is moving inertially in Minkowski space-time, and there is no relative velocity between the ships of the fleet, then a standard fleet time can be maintained. By contrast: if the individual ships of the fleet are firing their rocket engines equally hard, so that the proper acceleration of each ship is the same, then there is still no self-consistent procedure to maintain a standard fleet time.

Of course, I would not mention these things in an article aimed at introducing special relativity to novices. I mentioned it to explain how I understand Kevin Brown. Reflections on Relativity is written for an audience of people with a firm understanding of relativity. --Cleon Teunissen | Talk 08:12, 20 Jun 2005 (UTC)

the Michelson-Morley experiment, the Sagnac effect, and inertial frames of reference

The isotropy of the velocity of light holds in inertial and non-inertial frames (e.g. the Michelson Morley experiment showed that). Pdn 13:19, 20 Jun 2005 (UTC)

To my knowledge, the 1887 Michelson-Morley experiment took place in what was effectively an inertial frame of reference. (Given the level of sensitivity of the experimental setup.)

I will second that. The Michaelson interferometer used in that experiment was too small to locate any non-isotropy due to gravitation, and I believe that it was done on a table top (perpendicular to the acceleration due to gravitation) anyway (although later variations did use all possible orientations).

The propagation of light must be isotropic in the instantaneous interital frame of its emission (at least in a flat spacetime). However, in the view of an accelerating observer, there comes to be Shapiro delay effects such that isotropy around yourself is quickly lost given an extended enough experiment. --EMS | Talk 21:14, 20 Jun 2005 (UTC)

This is a pretty complicated situation. Here is how I see the physics of the 1887 Michelson-Morley experiment:

The experimental setup was located on Earth and the propagation of the light in the experimental setup was parallel to the surface of the Earth.
The experimental setup was located on the surface of the Earth, so the experimental setup was moving along a circular trajectory with resepect to the axis of rotation of the earth.

The size of the 1887 Michelson-Morley experimental setup was modest; I think the light covered a distance in the order of meters. So the transit time of the light was in the order of nanoseconds. The motion of the surface of the Earth during those nanoseconds time-interval is effectively indistinguishable from motion in a straight line.

Theoretically, if the 1887 Michelson-Morly experiment would have been conducted on one of the geographic poles of Earth, then the rotation of Earth would have been more certain to not distort the measurments. Michelson and Morley did not bother to travel to one of the geographic poles, because they had calculated that their setup was insufficiently sensitive anyway to pick up on the motion of Earth around its own axis.

If the 1887 Michelson-Morley experiment was to yield any result, it would be the velocity of Earth with respect to the luminiferous ether, the velocity of Earth of its orbit around the Sun.

The 1887 Michelson-Morley experimental setup had the light moving parallel to the surface of the Earth, they were not interested in effects from the gravitational field of the Earth. By contrast: the Pound and Rebka experiment (the Harvard tower experiment) was specifically aimed at finding an effect of the Earth's gravitational field, so the propagation of the photons in the Harvard tower experiment was set up to be perpendicular to the surface of the Earth.

Conclusions

There are profound differences in the aims and capabilities of the 1887 Michelson-Morley experiment and the Harvard tower experiment.

Michelson and Morley were confident that the acceleration due to the gravitational field of Earth (and the acceleration due to the gravitation of the Sun) would be below the detection threshold of their experimental setup, so there was no danger that it would compromise the experimental results. Michelson and Morley were confident that if their setup would measure something, it would be a velocity (a velocity with respect to the luminiferous ether.)

Pound and Rebka (and later Pound and Snyder) were confident that they would not pick up anything due to velocity, since relativity predicts that you never will. They hoped (and were vindicated) that their setup would be sufficienly sensitive to pick up the difference in gravitational potential over the 22 meter height difference of their setup.

(By the way, it is of course evident that the Harvard tower setup can be used in space-crafts to serve as an accelerometer. Acceleration can be measured in all sorts of ways: kinematically, interferometrically, and all types of measurement will yield mutually consistent results.)

The Sagnac Effect

My personal opinion is that the proper way to interpret the physics of the Sagnac effect is to look at the physics from the perspective of the local inertial frame of reference. I prefer the perspective of the local inertial frame of reference because that is the most symmetrical point of view.

By contrast: as seen from a point of view that is accelerating the speed of light appears to be non-isotropic, and I am rather suspicious about that.

I very much doubt that describing physics from an accelerating point of view has any meaning at all. EMS insisted that in the Sagnac effect article the physics should also be described as seen from a rotating frame of reference. I tend towards the opinion that describing physics from the point of view of a rotating frame of reference does not carry any physical meaning.

I assure you that the physics as viewed in a rotataing/accelerated frame of reference has meaning, even if the bottom line is that the same results are obtained in either case. The ability of use an accelerated viewpoint is especially important in GR, where you can be in a spaceship moving intertially, but the effects of gravitation are such that the objects distant from you are being accelerated, and effects such as gravitational time dilation and red/blue shifting are none-the-less revealing themselves.

Relatitivy fundamentally is about how perceptions of the same events are changed by virtue of being in different frames of reference. In essesnse, changing frames of reference is a gedanken is nothing more than putting yourself is someone else's shoes. In that regard their state of motion (be it inertial or not) should not matter. --EMS | Talk 21:08, 20 Jun 2005 (UTC)

The local inertial frame of reference

Usually I abbreviate to singular; I usually just mention: 'the local inertial frame of reference'. Of course, it is actually a class of reference frames. The class of all inertial reference frames together constitutes a symmetry group, and I usually abbreviate the entire class of all (local) inertial reference frames to: 'the local inertial frame of reference'.

In the case of the Sagnac effect the natural choice of inertial reference frame is the frame that is stationary with respect to the center of rotation of the sagnac interferometer.
--Cleon Teunissen | Talk 15:51, 20 Jun 2005 (UTC)

LIGO

The LIGO experiment is an exceedingly sensitive, very very large scale Michelson-Morley interferometer. I rather suspect that LIGO measuments need to be corrected for all sorts of local effects, due to the fact that the LIGO setup is constantly being accelerated. I suspect that the signals that are sought after (gravitational waves from beyond the solar system) are much weaker than the locally caused effects on the LIGO measurements.
--Cleon Teunissen | Talk 16:08, 20 Jun 2005 (UTC)

Re: wrong page?

I was trying to respond to Cleon with frames of reference, and to you with the MMX. Perhaps I was being too lazy there.

Do keep in mind that the MMX is not a rotational experiment, and it was intended to detect a fringe shift based on the motion of the Earth through the aether. In principle, the MMX could have been done on a rocket in free space traveling interially wrt the aether, and a fringe shift would be detected if the aether existed and the universe was Newtonian. Sagnac is a very different experiment. --EMS | Talk 04:32, 21 Jun 2005 (UTC)

The procedure of the 1887 Michelson-Morley experiment

I will think more about the Michaelson-Morley experiment as related to acceleration. But the idea was to detect differences in the "aether drift" as the apparatus turned (with the Earth). Pdn 00:41, 21 Jun 2005 (UTC)

Here is how I understand it.
Michelson and Morley would position the interferometer in a particular orientation, and they would do a measuring run. (Possibly such a measurement run would last only minutes, I don't know). Then they suspended the measuring, and they rotated the platform over an angle of 90 degrees, and resumed measuring.

I assume that the two perpendicular orientations of the measuring runs were meant for calibration purposes.

It is my understanding that Michelson and Morley wanted to avoid picking up effects due to the rotation of Earth around its axis. The 1887 Michelson-Morley experiment was aimed at eliminating or averaging out any effects stemming from the rotation of the Earth around its axis.

Michelson and Morley worked hard to set the experiment up in such a way that they would home in on measuring a velocity, the velocity of Earth with respect to the luminiferous ether in the Earth's orbit around the Sun. If the Michelson-Morley measurements would have been affected by acceleration too, then Michelson and Morley would have considered their measurement results as polluted results, polluted by side-effects.

Why did Michelson and Morley use a rotatable platform? Constructing the rotatable platform was a tremendous task, for during the measurement runs the platform had to be vibrationless, because of the sensitivity of the interferometry. The rotating platform was a huge slab of stone floating in Mercury. My understanding is that Michelson and Morley put in a huge effort to average out any effects due to the rotation of Earth around its axis.
--Cleon Teunissen | Talk 09:21, 21 Jun 2005 (UTC)

WikiProject Physics

Hi, Please consider joining Wikipedia:WikiProject Physics, and invite credible friends as you wish. linas 13:35, 21 Jun 2005 (UTC)

Planetary orbits

I think that you left a message on my talk page that was intended for someone else. However, curiously, I can answer it. Planetary orbits fall into the mathematical category of the gravitational N-body problem. Best of my knowledge, the gravitational 3-body problem is chaotic, and unstable, even for one large (solar) mass orbited by arbitrarily small masses. We need to define what "stable" means to continue the conversation. Clearly, taking various valid approximations, one finds the solar system is stable; its just that "absolute" stability is another thing. As to lyapunov exponents, orbits are weird; its not that simple. Things diverge,but then you wait longer, there's Poincare recurrence. See KAM torus for these kinds of stability discussions and some insight. Gotta run. linas 15:04, 21 Jun 2005 (UTC)

oh, sorry, I was confused; I see now what happened; you edited my user page instead of my talk page. I didn't see those comments so I was responding a bit out of context. I am reading those comments now, and will try to respond more approriately. linas 23:05, 21 Jun 2005 (UTC)