tag:blogger.com,1999:blog-22973357.post5044011768483814444..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: Hans-Christian Ørsted and electromagnetismSabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger15125tag:blogger.com,1999:blog-22973357.post-14141806137449497702007-08-16T20:00:00.000-04:002007-08-16T20:00:00.000-04:00Hi Santo,thank you very much for the reference!Hi ...Hi Santo,<BR/><BR/>thank you very much for the reference!<BR/><BR/><BR/><BR/>Hi Neil,<BR/><BR/>the theory of electromagnetism is a wonderful topic to tackle with the calculus of forms - that's what Hag and Bee have mentioned. If you do this, you can work out how the magnetic field (components of a two-form, which corresponds to a pseudovector in three space dimension) would "look like" in more stefanhttps://www.blogger.com/profile/09495628046446378453noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-80753958481829716412007-08-16T19:36:00.000-04:002007-08-16T19:36:00.000-04:00Hi changcho,I suppose there are no hints of any on...Hi changcho,<BR/><BR/><I>I suppose there are no hints of any one else noticing this before Orsted?</I><BR/><BR/>I am not really an expert on this, and would have to check out more closely - but according to this <A HREF="http://www.ampere.cnrs.fr/parcourspedagogique/zoom/oersted/decouvertehasard.php" REL="nofollow">French website about Oersted</A>, it had been known before that thunderstorms and stefanhttps://www.blogger.com/profile/09495628046446378453noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-22136045128568665652007-08-16T14:39:00.000-04:002007-08-16T14:39:00.000-04:00Hi All,A very nice analysis of Oersted's discovery...Hi All,<BR/><BR/>A very nice analysis of Oersted's discovery, explaining the erroneous use of symmetry arguments that cost him years of frustration, is found in Chapter 1 of the book <BR/><BR/>Icons and Symmetries<BR/><BR/>by Simon Altmann. The chapter also contains some interesting historical information. <BR/><BR/>All the best,<BR/>Santo D'AgostinoSanto D'Agostinohttps://www.blogger.com/profile/11280408850964096420noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-41566142907798717292007-08-16T09:42:00.000-04:002007-08-16T09:42:00.000-04:00Well, my main point was about another issue of phy...Well, my main point was about another issue of physical consistency and not magnetic field generalization at all, but thanks for the helpful discussion. I got different points mixed up in one post, and my statement about magnetic field was separate. First: Sure, B and the familiar effects can be generalized to N-dimensional space, and has to be. For example, a current in 2-D is surrounded by a Neil Bateshttps://www.blogger.com/profile/04564859009749481136noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-62409789929071988132007-08-16T09:07:00.000-04:002007-08-16T09:07:00.000-04:00Hi Neil,I agree with Hag above. If you understand ...Hi Neil,<BR/><BR/>I agree with Hag above. If you understand electrodynamics as a U(1) gauge group, there's nothing special with having 3 spatial dimensions (unless you consider self-duality or something), so one can write down a Lagrangian. # of possible photon polarizations changes however, e.g. in 1+1 there's no way a field can be orthogonal to another, so it's kind of a weird construction - I Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-34173826767128502952007-08-16T06:47:00.000-04:002007-08-16T06:47:00.000-04:00Tks Stefan, I will google for the original Danish ...Tks Stefan, I will google for the original Danish text.<BR/><BR/>So the vacumcleaner works on virtual photons! ...<BR/><BR/>This explains why my wife is always bitching about my cleaning up the apartment ;-)<BR/><BR/>Best<BR/><BR/>KlausAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-81466375439900984032007-08-16T00:05:00.000-04:002007-08-16T00:05:00.000-04:00First of all, Bee, I just wanted to say I am a big...First of all, Bee, I just wanted to say I am a big fan of your blog. <BR/>Secondly, in response to Neil', (Bee probably knows this stuff better than I do), the formulation of electromagnetism through differential forms is applicable to any dimension. In it however, (after a 3+1 split) the magnetic field is not a vector field, but a two-form (which can be transformed into a one form by using the Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-26485786987650376652007-08-15T18:22:00.000-04:002007-08-15T18:22:00.000-04:00Stefan, thanks for the interesting article. It is...Stefan, thanks for the interesting article. It is good to remember that it was only in 1820 that a connection was first noted serendipitously by Orsted between electric & magnetic phenomena. <BR/><BR/>I suppose there are no hints of any one else noticing this before Orsted?<BR/><BR/>changchoAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-9407142641304165652007-08-15T18:00:00.000-04:002007-08-15T18:00:00.000-04:00Dear Klaus,Is the word "electromagnetism" really a...Dear Klaus,<BR/><BR/><I>Is the word "electromagnetism" really a good word to discribe the phenomena? Or does the name itself influence our thinking, because the very word dictates unity?</I><BR/><BR/>hm, maybe it "dictates" unity for us today, since we are used to it - but I would not go so far as to insist on "dictate".<BR/><BR/>Moreover, Ørsted himslf used his notion "electromagnetic" instefanhttps://www.blogger.com/profile/09495628046446378453noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-45298434724061020032007-08-15T12:58:00.000-04:002007-08-15T12:58:00.000-04:001) No unfunded discovery is allowed.2) Proposal fu...1) No unfunded discovery is allowed.<BR/>2) Proposal funding is denied absent PERT charts and project conclusions.<BR/>3) All the world's ills are thereby Officially eliminated.<BR/>4) Adventitious discovery is a star chamber capital offense consistent with professional management canons.<BR/><BR/>Galileo and Oersted need not have happened. Galileo and Oersted need never happen again. A severe Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-18867707313251525682007-08-15T12:33:00.000-04:002007-08-15T12:33:00.000-04:00If space wasn't three-dimensional, how would EM wo...If space wasn't three-dimensional, how would EM work out? I am fascinated by extrapolation of EM (and other physical laws) to other dimensions. One note: we can have magnetic fields with big-dimensions N <> 3, just need a math adjustment. B isn't a vector anymore, but then again, angular momentum can't be either.) I explored this issue, and summarized in the linked blog. Basically:<BR/>The Neil Bateshttps://www.blogger.com/profile/04564859009749481136noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-68997227586879231702007-08-15T09:33:00.000-04:002007-08-15T09:33:00.000-04:00Hi There,Apologies that our server is down again s...Hi There,<BR/><BR/>Apologies that our server is down again so some of the pics are missing. They should reappear soon.<BR/><BR/>Klaus,<BR/><BR/>The electric and the magnetic field belong together. They transform into each other under a Lorentz transformation. Saying a field is purely electric doesn't even make sense without specifying the reference frame. A moving electron causes a magnetic fieldSabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-15818704550931544702007-08-15T08:48:00.000-04:002007-08-15T08:48:00.000-04:00Klaus,Electromagnetism is indeed the good word, an...Klaus,<BR/><BR/>Electromagnetism is indeed the good word, and Oersted was the first, I think, to see a bit of the unity underlying the phenomena. Electricity and magnetism are two faces of the same phenomenon when you look at them from a physical standpoint.<BR/><BR/>The air gap of an electric motor is populated by by electromagnetic fields (as are the rotor and stator). The momentum tranmitted CapitalistImperialistPighttps://www.blogger.com/profile/17523405806602731435noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-47166334341353750902007-08-15T02:56:00.000-04:002007-08-15T02:56:00.000-04:00Waves, and Reimann's succession to the world of th...Waves, and Reimann's succession to the world of the abstract perhaps.<BR/><BR/> The move to the non-euclidean world.<BR/><BR/> <A HREF="http://www.bartleby.com/173/f04.gif" REL="nofollow">Gaussian Geometrics</A>Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-85461033281050568132007-08-15T01:58:00.000-04:002007-08-15T01:58:00.000-04:00Hi All,Indeed I wonder about the relations between...Hi All,<BR/><BR/>Indeed I wonder about the relations between magnetism, the electric field, and EM radiation.<BR/><BR/>Is the word "electromagnetism" really a good word to discribe the phenomena? or does the name itself influence our thinking, because the very word dictates unity?<BR/><BR/>What is in fact transmitted in the air-gab of a common electric motor? It is not a transmission of Anonymousnoreply@blogger.com