tag:blogger.com,1999:blog-22973357.post2426036674549850412..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: Henri PoincaréSabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger20125tag:blogger.com,1999:blog-22973357.post-8446176495810280232007-05-15T06:45:00.000-04:002007-05-15T06:45:00.000-04:00The rate that my children grow up and my hair turn...<I>The rate that my children grow up and my hair turn grey is undeniablly a measure of time.</I><BR/><BR/>Thanks. The example you give may indeed be a measure of time. But your hair does not measure time. My hair may be greying faster than yours, does that mean that time is running faster? And someone whose hair is not greying would tell us that time is not changing. Same with any oscillator. By Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-9872961692676297802007-05-15T05:42:00.000-04:002007-05-15T05:42:00.000-04:00Pioneer1,The rate that my children grow up and my ...Pioneer1,<BR/><BR/>The rate that my children grow up and my hair turn grey is undeniablly a measure of time.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-19110837851757298412007-05-12T13:00:00.000-04:002007-05-12T13:00:00.000-04:00Hi Bee,For practical purposes it is sufficient to ...Hi Bee,<BR/><I>For practical purposes it is sufficient to treat time naively as what is measured by a clock.</I><BR/><BR/>To me physics is an experimental science. I would not teach a known falsehood for "practical purposes." If time is not a measurable quantity and if some physicists are claiming to have measured it by using oscillators, then, this reduces physics into magic. If physicists Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-38670096637542125022007-05-11T08:44:00.000-04:002007-05-11T08:44:00.000-04:00Whereas I agree that time is what a clock measures...Whereas I agree that time is what a clock measures, things become more subtle when you take quantum mechnics into account. Let me quote from <A HREF="http://www.arxiv.org/abs/quant-ph/0303106" REL="nofollow">quant-ph/0303106</A>:<BR/><BR/>"Time is widely recognized as a parameter in quantum mechanics, and no one emphatically asserts this conviction in recent times more than Sakurai’s assertion inAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-57600131029633101392007-05-10T10:18:00.000-04:002007-05-10T10:18:00.000-04:00Pioneer,I just wanted to say that my quote was tak...Pioneer,<BR/><BR/><I>I just wanted to say that my quote was taken from lecture notes from University of Illinois and represents the official view of time in physics. </I><BR/><BR/>I just wanted to say that your idea of an 'official view' in physics is bullshit. If there was one, you'd definitely not find it by googling for somebody's lecture notes.<BR/><BR/><I>I believe that your view on time is Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-78095689317274042322007-05-08T23:47:00.000-04:002007-05-08T23:47:00.000-04:00I just wanted to say that my quote was taken from ...I just wanted to say that my quote was taken from lecture notes from University of Illinois and represents the official view of time in physics. That time is what clocks measure is taught to students in the physics classroom. I believe that your view on time is an unorthodox one. This is not surprising to me since this is what Perimeter Institute is about.<BR/><BR/>The fact that some physicists Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-67760596366822636292007-05-06T19:38:00.000-04:002007-05-06T19:38:00.000-04:00Hi Pioneer,But this is the accepted definition of ...Hi Pioneer,<BR/><BR/><I>But this is the accepted definition of both time and clock in physics as explained here (note 1) </I><BR/><BR/>I couldn't care less what some guy writes in his notes that you found somewhere in the web, and I doubt very many of my colleagues would agree that this is 'an accepted definition of both time and clock in physics'. I have tried to point out that indeed many Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-10713874264376509972007-05-06T18:58:00.000-04:002007-05-06T18:58:00.000-04:00Hi Bee,it's a meaningless statement unless one cla...Hi Bee,<BR/><BR/><I>it's a meaningless statement unless one clarifies what a clock is.</I><BR/><BR/>I agree with your assessment that this is a meaningless statement. It is a double definition like Newton's definition of force with mass and mass with force. But this is the accepted definition of both time and clock in physics as explained <A HREF="http://www2.ling.su.se/staff/hartmut/uhr.htm" RELAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-59124162281055859262007-05-04T09:37:00.000-04:002007-05-04T09:37:00.000-04:00Hi Pioneer,What is my theory?Well, I don't know wh...Hi Pioneer,<BR/><BR/><I>What is my theory?</I><BR/><BR/>Well, I don't know what 'your theory' is. My sentence was supposed to say 'this is what the theory one wants to test needs to predict'. Sorry for being sloppy with the wording. Also, I have to apologize, please keep in mind: I am not a native speaker. I do my best, but its not always sufficient.<BR/><BR/><I>I cannot agree with your statementSabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-33062165258603158682007-05-04T00:29:00.000-04:002007-05-04T00:29:00.000-04:00Bee, thank you for your reply.I cannot agree with ...Bee, thank you for your reply.<BR/><BR/>I cannot agree with your statement that "the idea is not to measure 'time" itself..." In physics time is defined as "time is what clocks measure." http://www.pitt.edu/~gbelot/Courses/06-1/0610/3slides.pdf Do you agree with this definition?<BR/><BR/>I am unable to agree with your statement that "time only appears in intermediate steps but not as an entity byAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-72464775726019624952007-05-02T21:19:00.000-04:002007-05-02T21:19:00.000-04:00Hi Pioneer,the idea is not to measure 'time' itsel...Hi Pioneer,<BR/><BR/>the idea is not to measure 'time' itself (I too wouldn't know how to do it), but to measure observables against observables, that is relations in which time only appears in intermediate steps but not as an entity by itself. (There is a name for that but I forgot, sorry, will let you know if it comes to my mind.) To give you an example: you measure the redshift of an object (Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-25435114550042846722007-05-02T21:09:00.000-04:002007-05-02T21:09:00.000-04:00Hi Stefan, thanks for your reply. I may be confusi...Hi Stefan, thanks for your reply. <BR/><BR/>I may be confusing Poincare with Mach. I think it was Mach who said that time was an abstraction.<BR/><BR/>But I question, regardless of Poincare's belief, that "clocks measure time."<BR/><BR/>How do physicists test if a quantity is measurable?<BR/><BR/>There was a physicists at MIT, the story goes, who was trying to duplicate Big Bang in his basement. Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-13478850562785213822007-05-01T21:05:00.000-04:002007-05-01T21:05:00.000-04:00Pioneer,I strongly doubt that your doubt that Poin...Pioneer,<BR/><BR/><BR/>I strongly doubt that your <I>doubt that Poincare would have believed that clocks measured time</I> is justified...<BR/><BR/>I am not an expert on Poincaré, but just about time and simultaneity, in all his writings he emphasizes the role of conventions to establish these very concepts. <BR/><BR/>So, would you not agree that the statement that exact clocks measure stefanhttps://www.blogger.com/profile/09495628046446378453noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-23334406802165726412007-05-01T20:54:00.000-04:002007-05-01T20:54:00.000-04:00changcho,thank you for reminding us of Poincar&eac...changcho,<BR/><BR/>thank you for reminding us of Poincaré's discovery of deterministic chaos! Somehow, that's more apart from the physics I have been in touch with lately, so I nearly forgot about it... but indeed, I first heard of Poincaré in relation with <A HREF="http://www.cg.tuwien.ac.at/~helwig/diss/node30.htm" REL="nofollow">Poincaré sections and Poincaré maps</stefanhttps://www.blogger.com/profile/09495628046446378453noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-9811929735306832662007-05-01T20:37:00.000-04:002007-05-01T20:37:00.000-04:00Thomas,Poincaré has written several semi-po...Thomas,<BR/><BR/>Poincaré has written several semi-popular books, which seem to have been quite well-known and much read at the time. The book you mention could have been a translation of his 1902 "La Science et l'Hypothèse", which contains a description of Lorentz theory. The french text is available from the <A HREF="http://www.univ-nancy2.fr/poincare/" REL="nofollow">Archives stefanhttps://www.blogger.com/profile/09495628046446378453noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-12042311187837663582007-05-01T20:07:00.000-04:002007-05-01T20:07:00.000-04:00Frank,I don't understand a word of what you try to...Frank,<BR/><BR/>I don't understand a word of what you try to say ;-)... the "prosaic formulation", however, is probably too easy to be correct. For example, Poincaré writes in "La Science et l'Hypothèse" (1902), as cited in the Darrigol paper: <BR/><BR/><I>It matters little whether the ether really exists; that is the affair of the metaphysicians. The essential thing for us is that stefanhttps://www.blogger.com/profile/09495628046446378453noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-43863708010703644282007-04-30T21:37:00.000-04:002007-04-30T21:37:00.000-04:00I like Poincare's essays. But in the link that you...I like Poincare's essays. But in the link that you posted to the book Einstein's Clocks, Poincaré's Maps http://www.fas.harvard.edu/~hsdept/bios/galison-einsteins-clocks.html the first sentence is "True time would never be revealed by mere clocks--of this Newton was sure." Then it goes on to imply that clocks measure time or that "Times" replace "time".<BR/><BR/>I doubt that Poincare would have Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-16333103325163864542007-04-30T20:33:00.000-04:002007-04-30T20:33:00.000-04:00I became familiar with Poincare's achievements mor...I became familiar with Poincare's achievements more through his work in the three-body problem, rather than his work in relativity. Indeed, it seems Poincare may have been the first person to get the earliest glimpse of chaos theory. <BR/><BR/>changchoAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-35021595456053024942007-04-30T09:34:00.000-04:002007-04-30T09:34:00.000-04:00A couple of years ago I found a book by Poincare i...A couple of years ago I found a book by Poincare in my father-in-law's library. In this book, printed in 1911 (Swedish translation printed in 1911, didn't say when French original was printed), Poincare discusses Lorentz' modifications of ether theory with great enthusiasm and in great length, whereas he never mentions Einstein.<BR/><BR/>On a related note, ether theory was alive, if not well, Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-39449432896731038272007-04-29T19:03:00.000-04:002007-04-29T19:03:00.000-04:00In a recent conversation me and a friend hit upon ...In a recent conversation me and a friend hit upon the role deconstruction playsin physics. Within the language of structuralism, it is clear that empiricsmprovides us with a center for our structures. They are not in free play, however the inversion characteristic in deconstruction, that reversal of hierarchies in which that which was to be deduced becomes the new center from which the original Frankhttps://www.blogger.com/profile/07530630846648786816noreply@blogger.com