Timeline for Dark matter a medium for light propagation
Current License: CC BY-SA 3.0
18 events
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| Sep 3, 2014 at 13:41 | comment | added | user1247 | @anna v, yes, ridiculous that you have too much pride for scientific and pedagogic honesty. I can quote from Jackson or Landau all day: "one should properly speak of the electromagnetic field Fuv rather than E or B separately." The electromagnetic field is absolutely mandatory given relativity, and has nothing to do with QFT. That said, it is completely specious to say that QFT is not "necessary" for answering the question. There are no "classical" qualifications made here. The question is about nature, and if QFT tells us something relevant about nature then so be it. | |
| Sep 3, 2014 at 4:19 | comment | added | anna v | @user1247 This is getting ridiculous. We have a proverb in Greece "come grandfather let me show you your vineyards" . You are simply wrong that there exists a classical field for radiation in classical physics, which are self consistent theories until one hits dimensions of hbar. There exist electric and magnetic fields. And yes, you are carrying over a QFT definition of field which is unnecessary in answering this question. | |
| Sep 2, 2014 at 19:18 | comment | added | user1247 | @anna v, they don't need a source, are you aware of electromagnetic radiation? Do you know the definition of "field" when you say "electric field" and "magnetic field"? Of course these guys are frame dependent which is why one should even classically talk about the 4-potential and the EM-field rather than its frame-dependent components. This is stuff you should know, which is way this discussion is bizarre. Are you really trying to argue that "electromagnetic field" is a non-classical concept? | |
| Sep 2, 2014 at 4:46 | comment | added | anna v | @user1247 Classically there exist an electric field and a magnetic field, and they need a source. The electromagnetic manifestation is a wave propagating in space in specific loci. If I am being stubborn it is because I am defending the answer, which is a good and complete one with no need of invoking QFT . I searched "classical electricity and magnetism " by Panosfsky and Philips for "electromagnetic field" with 0 results. fisica.net/ebooks/eletricidade/… | |
| Sep 2, 2014 at 4:18 | comment | added | user1247 | @anna v, you are being stubborn and specious to no positive end. Even classically the EM field is a field, and fills all space by definition of "field," regardless of whether it has zero amplitude. | |
| Sep 2, 2014 at 3:48 | comment | added | anna v | @user1247 Sorry but this board is for answering specific questions so the questioner can learn something "Is dark matter a candidate to fill void left by luminiferous ether as a medium for light travel" this is completely within the classical framework and can be negated there. Introducing QFT in a nutshell is not necessary, imo . | |
| Sep 1, 2014 at 19:08 | comment | added | user1247 | @anna v, classical fields are not the background of the question. The question is about nature generically, which we know is not classical. | |
| Sep 1, 2014 at 18:50 | comment | added | anna v | @user1247 I was talking of classical fields which is the background of the question. Not of the QFT vacuum, which respects Lorenz invariance of course . | |
| Sep 1, 2014 at 16:53 | comment | added | user1247 | Yes, and light is understood to be ripples in the EM field that permeates all of space. It is of course a Lorentz invariant field in accord with the Michelson Morley experiment. | |
| Sep 1, 2014 at 16:32 | comment | added | dmckee --- ex-moderator kitten | In the usual understanding the field does permeate all space, but it may have value zero in much of it, indicating that there is "no electric field" in the language used in introductory courses. | |
| Sep 1, 2014 at 16:18 | comment | added | user1247 | @anna v, that is completely wrong, as you should know, by definition of field, by any knowledge of the Standard Model, and by experimental fact of vacuum polarization, casimir effect, etc. | |
| Sep 1, 2014 at 13:49 | comment | added | user56930 | I'm simply asking an isolated question. Is there anything to prevent the hypothesis that dark matter as it is currently conceptualized might propagate anything?...just received your kind answers. Thanks | |
| Sep 1, 2014 at 13:42 | comment | added | anna v | @user1247 the electromagnetic field is actually a varying electric and magnetic field with energy and momentum, not permeating all space either. | |
| Sep 1, 2014 at 13:40 | comment | added | anna v | Dark matter may propagate sound, i.e. pressure waves of some type. In general it has been hypothesized to fit the gravitational orbits of galactic clusters, so dark matter is not something permeating all space uniformly. | |
| Sep 1, 2014 at 13:38 | comment | added | user1247 | "Water waves are in water, sound waves are in air, therefore there must be something in which light propagates." ... There is something in which light propagates: the electromagnetic field. It just happens to be a field that is Lorentz invariant. | |
| Sep 1, 2014 at 13:29 | comment | added | user10851 | Things can only propagate stuff they interact with. Dark matter's sole reason for existing is that we see evidence of stuff that interacts via gravity and essentially nothing else. So it can have gravitational effects, but e.g. gravitational waves, like light, don't need a medium to propagate in. | |
| Sep 1, 2014 at 13:25 | comment | added | user56930 | Thanks for your time. I'm sure the void I speak of is the void in my own. understanding. Suffice to ask only: is there anything to prevent the hypothesis that dark matter might propagate anything as a medium. Perhaps my question is not a fair question. | |
| Sep 1, 2014 at 13:21 | history | answered | user10851 | CC BY-SA 3.0 |