A constant speed of light in all reference frames? Surely you can't be serious.
in [Relativity]
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From: Ste on 27 Feb 2010 22:20 On 27 Feb, 13:00, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > news:2726fc2b-b860-4c84-96a9-3776df684de4(a)e7g2000yqf.googlegroups.com... > > > > > > > On 27 Feb, 07:02, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > > wrote: > >> "Ste" <ste_ro...(a)hotmail.com> wrote in message > > >>news:f1c82fe9-c833-4262-9bca-d62d9181c8b0(a)i39g2000yqm.googlegroups.com... > >> On 26 Feb, 12:52, "Inertial" <relativ...(a)rest.com> wrote: > > >> > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > >> > > Of course I'm not claiming to know anything profound about the solar > >> > > system. The conceptual model has been accepted for centuries, and I'm > >> > > not pretending to add anything new to it. The point I was making > >> > > about > >> > > it is that the conceptual model is required to give any real meaning > >> > > to the equations. > > >> > We already have such model .. that's the whole POINT of physics .. it > >> > is > >> > modeling reality. How reality behaves is the meaning to the equations > >> > .. > >> > they describe what is going on. > > >> Then show the equations to a child. Ask him if he understands what is > >> going on. And remember, you're not allowed to mention the conceptual > >> aspect, or appeal to sensory perception. You must only use the > >> equations. If these equations alone describe what is going on > >> meaningfully, then the child ought to understand immediately. > > >> ___________________________________ > >> Why a child? > > >> Why not try and explain the equations of SR to a nematode worm? If they > >> really do encompass SR, then the nematode worm should understand SR > >> immediately. Or so your logic would suggest. > > > No, my logic wouldn't suggest that. My logic says that these equations > > are meaningless without a conceptual model that gives them meaning. > > What's wrong with Minkowski space-time? It gives me and lots of other people > a very clear conceptual model of SR. > > > > > > > > >> Here are the facts. To fully understand SR, you need to be reasonably > >> intelligent, have a basic maths ability, and have some knowledge of > >> physics. > > >> A child, a nematode worm, and yourself all miss out on some or all of > >> these. > > >> If you want to understand SR, you are going to need to learn some maths > >> and > >> physics. Some things actually require work. Sorry. > > > You can teach the child maths. But you can't tell him anything about > > the nature of the universe (because otherwise you're providing the > > conceptual model by the back door, when it is your argument that this > > is not necessary to understand physics, only the maths is required). > > That was not my argument. Then can we revise, what is your argument? As I understood your argument, it was that the mathematical descriptions which account for what is observed is to paraphrase the "full extent of physics", and that anything else to do with the conceptual basis is "just philosophy". > But I still don't get what your problem is with the conceptual model of SR > provided by Minkowski space-time? It is isomorphic to SR, uses only simple > geometry, and all the key equations of SR become simple geometric > constructs. Minkowski contributed nothing to SR except a superb conceptual > model, apparently exactly the thing you want. > > So why not learn it? Because you still don't seem to fully comprehend my plain words, that a mathematical model of SR is quite different from a physical model. You repeat over that "Minkowski is a physical model", but it isn't according to the requirements of what I (and of course, many others in society) hold to be "physical". Minkowski doesn't rest on physical concepts. It doesn't lay any claim as to what "time" is, for example, in a qualitative sense. Nor does SR explain qualitatively what electromagnetic radiation is, or what its effects are. It necessarily doesn't, as a purely mathematical theory, detail whether what you are seeing is "reality", or whether it is merely an optical illusion, or whether SR is a combination of "real" effects and optical illusions. These are all significant questions to anyone with a sensible view of "physics". After all, there are mathematical models that will describe what you see in a curved mirror, and yet according to your argument there is no need to go further in detailing whether you are seeing "reality" or merely an illusion. Indeed it seems to me that, according to your argument, the question of whether a curved mirror causes an optical effect, or whether there is really another copy of my body inside an alternate universe, is a question of "mere philosophy". Of course, I await correction on my interpretation of your arguments, but you can see just how spectacularly obtuse and narrow-minded it is to say (if indeed you are saying) that the physical nature of various observations are "a question of philosophy, not physics".
From: Ste on 28 Feb 2010 00:22 On 27 Feb, 15:44, PD <thedraperfam...(a)gmail.com> wrote: > On Feb 26, 6:34 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > The fact that this conceptual model in a raw form > > > > can permit predictions that are so permissive as to make almost no > > > > prediction at all, does not mean they are not an essential component > > > > to scientific enquiry and advance. > > > > No testable predictions = not science. Possibly philosophy, possibly > > > fiction, possibly drug induced free association speech, possibly gibberish, > > > possibly an incredibly profound insight into human emotions, possibly > > > masturbation. But not science. Science makes testable predictions. (Note > > > that this is a necessary but not sufficient condition. Astrology also makes > > > predictions, just very poorly). > > > I think you're attributing an absurd definition to "science". Paul > > Draper probably had a more tenable argument when he said that string > > theorists are scientists doing science, but that they do not yet have > > a "scientific theory". But I know from talking to him that he > > attributes a very contorted meaning to the phrase "scientific theory", > > that would condemn a lot of scientific knowledge, both historical and > > current, as being "unscientific". > > Examples, please. In physics I would raise the same old example: string theory . But there are certainly more. We have things like "dark matter". Or even Newton. Or Galileo. And more broadly, in biology we have evolution, and in economics, rational choice theory. All managed to fail your previously stated requirement of a "scientific theory", which (amongst other things) is being falsifiable (in a practical rather than just notional sense), not ad-hoc, and predicting observations that are not already accounted for.
From: Ste on 28 Feb 2010 00:23 On 27 Feb, 15:46, PD <thedraperfam...(a)gmail.com> wrote: > On Feb 26, 6:46 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > On 26 Feb, 12:52, "Inertial" <relativ...(a)rest.com> wrote: > > > > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > > > > Of course I'm not claiming to know anything profound about the solar > > > > system. The conceptual model has been accepted for centuries, and I'm > > > > not pretending to add anything new to it. The point I was making about > > > > it is that the conceptual model is required to give any real meaning > > > > to the equations. > > > > We already have such model .. that's the whole POINT of physics .. it is > > > modeling reality. How reality behaves is the meaning to the equations .. > > > they describe what is going on. > > > Then show the equations to a child. Ask him if he understands what is > > going on. And remember, you're not allowed to mention the conceptual > > aspect, or appeal to sensory perception. You must only use the > > equations. If these equations alone describe what is going on > > meaningfully, then the child ought to understand immediately. > > I'm not sure I buy the argument that anything should be fundamentally > understandable to a child. The point was to explain the theory to someone who hasn't already implicitly internalised the conceptual model on which the equations rest. This is, after all, the test of whether the equations are a complete description of reality, as Paul contends. You could substitute uneducated adults, or even foreign cultures, for the child, but that would probably attract the criticism that the problem is one of language, inherent (lack of) ability, or cultural incompatibility to account for the failure of those others to comprehend the meaning of the equations. Whereas, if we start with a child, we at least assume that they speak the same language, have a similar level of exposure to our culture (but are not yet educated in science), and have a reasonable amount of ability.
From: Peter Webb on 28 Feb 2010 01:25 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:00434686-8fca-4ca5-a321-8f68700d1e41(a)o3g2000yqb.googlegroups.com... > On 27 Feb, 12:53, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > wrote: >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> news:f47fb4af-7f73-420b-b61b-73a4ce42b1e5(a)q15g2000yqj.googlegroups.com... >> >> >> >> >> >> > On 27 Feb, 06:55, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> >> > wrote: >> >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> >>news:2268f44a-518e-43b4-a3f8-a610f4e89e89(a)o30g2000yqb.googlegroups.com... >> >> >> > On 26 Feb, 12:31, "Peter Webb" >> >> > <webbfam...(a)DIESPAMDIEoptusnet.com.au> >> >> > wrote: >> >> >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> >> >> About this gravity thing. I am having a great deal of difficulty >> >> >> forming >> >> >> a >> >> >> mental picture of how it is supposed to work. >> >> >> > At a fundamental level, I do too. >> >> >> >> If the planets are separated >> >> >> by vacuum, how could one object possibly pull on another object >> >> >> when >> >> >> there >> >> >> is nothing between them? For that matter, how does one particle >> >> >> manage >> >> >> to >> >> >> pull on every other particle in the Universe at the same time? Are >> >> >> you >> >> >> positing some array of invisible springs, 10^160 of them, >> >> >> connecting >> >> >> the >> >> >> 10^80 particles in the Universe? >> >> >> > I think a more credible argument is that there *is* in fact >> >> > something >> >> > in between the objects. >> >> >> >> Frankly, I find the suggestion that each time I move my finger to >> >> >> type >> >> >> these >> >> >> invisible gravity springs cause every other particle in the >> >> >> Universe >> >> >> to >> >> >> move >> >> >> ludicrous. Apart from anything else, how is this spooky action at a >> >> >> distance >> >> >> supposed to work, physically? Springs and levers? What is gravity >> >> >> supposed >> >> >> to be, physically? >> >> >> > I don't find it hard to believe that every movement of the finger >> >> > could have an effect on every other particle of the universe. In >> >> > terms >> >> > of what gravity is and how it works, that remains to be explained. >> >> >> Ohhh, so your mental model of the solar system contains "gravity", yet >> >> your >> >> mental model of the solar system provides no physical explanation of >> >> what >> >> it >> >> "really" is. >> >> >> Funny, you complained about SR and Minkowski for having components for >> >> which >> >> you have no physical model. Yet your own theory of the solar system >> >> contains >> >> concepts such as gravity which have no physical explanation at all >> >> within >> >> the model. >> >> > Yes, but I readily concede this, and accept that there needs to be >> > work done to find out what gravity actually is. For the time being, I >> > have a model that operates at a macro level, where gravity is assumed >> > to be a fundamental manifestation of reality. Yet you speak as though >> > I've let the cat out of the bag or something. >> >> So you have no *physical* idea of what gravity really is, but that >> doesn't >> stop you using it in a model. >> >> Funny, the fact that SR contains things which you have no *physical* >> explanation of was a huge problem for SR, but the same problem doesn't >> worry >> you for your own model. > > How on Earth have you drawn that conclusion? On the contrary, I hold > that it *is* a problem that there is no apparent physical explanation > for gravity (in terms of what it is, how it is mediated, how it > relates to other forces, etc). I am demonstrating that you are inconsistent in your requirement that explanations be physical. You claimed that you had a physical model "in your head" of how the solar system rotates - involving orbits, masses and "gravity". But your model has no physical explanation for gravity. It is no more a physical description of the solar system than Minkowski is of SR - both models contain things which have no physical explanation (according to you, anyway). Yet you accept these in your model of the solar system (as did Newton in his model), but reject them for SR. You may well have an intuition as to what gravity is, but no intuition as to what SR predicts. That's only because you live inside a gravity well, but planes don't fly at 0.9 c. Reverse these and you would have an excellent intuition as to SR, but none as to gravity. Your intuition is a comment only on your personal experience, and not on what happens when objects are accelerated to near the speed of light. The great and interesting thing about science and maths is how often intuition is completely wrong. These are the experiments which really test a theory. If intuition was always right, we wouldn't need science, we would just use our intuition when we decide how big the magnets have to be in a particle accelerator, and not bother discovering SR at all.
From: Ste on 28 Feb 2010 01:54
On 27 Feb, 15:54, PD <thedraperfam...(a)gmail.com> wrote: > On Feb 26, 6:54 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > On 26 Feb, 17:34, PD <thedraperfam...(a)gmail.com> wrote: > > > > On Feb 25, 9:05 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > I also doubt one exists at the moment, but I see that as a problem. > > > > It's utterly irreconcilable, within any conceptual framework that I > > > > know of, to have situations where, for example, a large ladder can end > > > > up in a smaller barn according to an observer stationary in the barn, > > > > but not according to an observer riding the ladder. > > > > Why? And here we can systematically trace back to the assumptions you > > > are making and then question them. In this case, you have a firm > > > belief that length is definable in such a way that it is intrinsic to > > > the object and frame-independent, and that physical "fitting" is a > > > function of the *intrinsic* lengths of two objects (or an object and a > > > container). > > > My only contention is that it is *not realistic* to say that from the > > barn frame frame the ladder contracts and fits inside, while saying > > that from the ladder frame it is the barn that contracts and the doors > > actually never shut simultaneously. It is simply not realistic. > > I don't know what basis you have for judging whether something is > "realistic". I must admit I can't quite put my finger on it myself. > I'm guessing that it means that it is consistent with > your intuition, and that your intuition tells you that something > cannot fit in one frame and not fit in another, or that two events are > simultaneous in one frame and not simultaneous in another. If this is > accurate, then I would ask on what basis you trust your intuition. Or, > even more aptly, why do you trust your intuition so much that you rule > out other possibilities as real if they conflict with your intuition? Because on the one hand my physical (i.e. practical-mechanical) intuitions are well-developed and highly consistent with my experience of reality, and secondly it is not readily apparent that SR is inconsistent with these intuitions. In the face of people who suggest the two are inconsistent, obviously I've got to first consider whether there's a language difference between me and the opponent (i.e. no common apprehension of verbal meaning), and secondly whether the opponent is confused or simply wrong (i.e. no common apprehension of the evidence). The ultimate resolution of this question seems to be confounded firstly by the degree to which there is no shared language, secondly the degree to which opponents seem to be unclear about the conceptual/ qualitative basis of SR, and thirdly the preconceptions and psychological style of many posters. > > If > > such a thing appears to happen, then it is obviously an artefact of > > subjective observation. > > I disagree. In science, if there is a conflict between experimental > observation and intuition, then it is *intuition* that becomes > suspect, not the experimental result, especially if the latter is > confirmed independently and by complementary means. I'm afraid there is no room for a discrepancy between intuition and observation. Intuition is supposed to account for observation, and there is no question of observation taking a back seat to intuition. So that in that way we agree. But this is not the same as crude observationalism. > > > > > Your disbelief of SR stems from the fact that you don't understand it. > > > > > My disbelief, really, stems from the blatant lack of conceptual > > > > understanding of the theory. I mean, as I repeatedly point out, I > > > > don't know a single equation of relativity, and yet I can root out the > > > > conceptual contradictions immediately when people here have a crack at > > > > making meaningful qualitative statements in SR. The classic example, > > > > of course, was Paul's contention that "what is simultaneous in one > > > > frame can never be simultaneous in another", which of course isn't > > > > true according to SR. > > > > I'm sorry? It is very much true in SR that two spatially separated > > > events that are simultaneous in one frame are not simultaneous in > > > another frame moving relative to the first. > > > But I contradicted that when I pointed out that two observers can be > > moving relative to each other, and yet undoubtedly events can be > > simultaneous for both. > > Not spatially separated ones, no. I'm confused, because I thought we previously agreed that two observers travelling along the same axis, maintaining equidistance from both events at all times, would both report each event as simultaneous with the other event. And moreover, if they not only both maintained equidistance from both events, but if they maintained a separation which was equal for both observers (which, if both observers are moving relative to each other, requires either a collision course between observers, or travel in diametrically opposite directions), then there is no question that the signals are received simultaneously. Illustration: E1 -------- E2 The line represents the line between events E1 and E2, along which the observers may move while always reporting both events to be simultaneous. |