A constant speed of light in all reference frames? Surely you can't be serious.
in [Relativity]
|
From: Inertial on 3 Mar 2010 17:23 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:64d02f70-01e4-44a5-a5ab-41429bf37f71(a)q15g2000yqj.googlegroups.com... > I'm sure I said something about the ludicrous assertions that some > people here have made about the conceptual basis of SR. That is, > assertions that verge on meaningless, like "rotation into time" as an > explanation for length contraction. Or even observed time dilation (in > SR) being "real" as opposed to merely a function of propagation > delays. But none of this fundamentally challenges SR. Time dilation isn't anything to do with propagation delays .. they do NOT cause time dilation. It IS real in that it has been measured experimentally. Your denial of reality is another trademark of a crackpot.
From: Inertial on 3 Mar 2010 17:31 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:df834005-0692-42ba-88c7-b462ad4cd0b2(a)i25g2000yqm.googlegroups.com... > On 3 Mar, 12:30, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > wrote: >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> >> You say you are here to learn about SR. >> >> > I am here to learn more about the *conceptual basis* of SR. >> >> Minkowksi space time? > > No. > > >> >> Do you believe SR is true? >> >> > I accept it's mathematical form has some obvious truth, yes. >> >> Do you believe that it correctly predicts the results of every experiment >> that it claims to? That clocks run slower, > > No. In SR, clocks *appear* to run slower as you are increasing your > distance from the clock. The effect is entirely apparent in SR. WRONG Gees. .you just have no idea *what* you are talking about. That is NOT what time dilation is about. >> and 80 foot ladders can fit through 40 feet barns, > > It remains slightly unclear, but I'm inclined to say no, Then you do not understand or accept SR. > although it > can certainly be made to appear to happen in certain circumstances. So if you close the doors simultaneously on a barn and the rod is inside you think that means it is not REALLY inside? >> and that the speed of light is measured the same in >> every intertial frame of reference and this speed is independent of the >> speed of the emitter, receiver, and underlying medium of transmission? > > Yes. I think I've been able to reconcile this partially, but only > vaguely and within a definitely non-standard conceptual framework, and > it is forced to completely dispense with any corpuscular form of > matter, and instead relies wholly on fields. Unfortunately it's > probably the sort of thing that physicists spend their lives thinking > about and never quite put their finger on. > > > >> If you believe all of those things, then you are saying more than "SR has >> some obvious truths in its mathematical form" you are saying it is an >> accurate portrayal of reality - ie, what happens when you conduct those >> experiments, what physically and actually happens, is exactly as >> predicted >> by Relativity. > > I think we all agree that SR portrays reality, But you DO NOT KNOW WHAT SR SAYS .. and you have just denied that the things SR predicts happen. So you are inconsistent > but none of us seem to > be able to agree on what kind of reality it portrays. Nonsense .. it is just YOU who do not understand >> If, on the other hand, you do not believe in the twin "paradox" actually >> happening, you don't believe in SR. > > We resolved the twins paradox months ago. The astronaut twin undergoes > asymmetrical acceleration, and that is why he returns younger. > > > >> If you do believe the predictions of SR >> that one twin is older, then you believe that time dilation is more than >> some mathematical fiction, its what actually happens in the real world. > > On the contrary. The involvement of acceleration, which is the domain > of GR, makes me wonder why this is held to be a paradox in SR at all. SR handles acceleration just fine > And yes, the acceleration causes real effects for the astronaut twin. > > > >> So, when relativity predicts that one twin will age more than the other, >> is >> this just some mathematical truth, or is it what really happens as well? > > It really happens, due to acceleration. > > > >> So, do you believe that SR is correct in its prediction (for example) >> that >> if one twin were to be sent off into space at 0.9c for 10 years they >> would >> have aged less on their return than the twin that stayed at home? > > I'm not sure SR does predict this. Of course it does .. that is the twins paradox you just said you understnood !! > As I understand it, GR is required > to predict this effect. Wrong > The problem for SR was, as I understand it, > explaining why SR *doesn't* predict that effect. It DOES predict it. My god you are SO DAMNED IGNORANT of what you ponficiate about. >> Do you agree its correct when it says that an 80 foot ladder could fit >> inside a 40 foot barn? > > No, I'm not confident about that prediction. I think it's more likely > to be an apparent effect. What is only 'apparent' about shutting the doors on a barn simultaneously with a long rod fully ensloed between them? Do you think it is all done with mirrors? >> You seem to agree they are "mathematical truths". Do you also agree those >> equations correctly predict the outcomes of real world experiments, which >> means they are far more than simply "mathematical truths"? > > The question is of interpreting the mathematical predictions. As I say > above, there is a difference between what is real and what is merely > apparent.
From: PD on 3 Mar 2010 17:45 On Mar 3, 11:05 am, Ste <ste_ro...(a)hotmail.com> wrote: > On 3 Mar, 11:53, "Inertial" <relativ...(a)rest.com> wrote: > > > > > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > > > (a bit like how > > > Christians claim the Bible characterises the practice of their > > > religion). > > > They don't .. not if they know what they are saying. They may claim that > > concepts and principles that they chose to find in the bible are the basis > > for how they practice their religion .. but Christian religious practice > > (which varies considerably from denomination to denomination) is certainly > > never solely based on the bible. Indeed, much of what is practiced has no > > valid biblical basis, but is rather cultural and historical traditions. > > > However, as with most religions, there are a set of beliefs that one who is > > to be a member of a religion must hold to be true, whether or not there is > > any evidence or proof of those beliefs. > > Indeed. And the same is true of science! The "scientific method" is > about as correspondent with reality as the Bible. :>) I'm sure you wrote that to just get a reaction. One might argue that the Bible and science deal with very different aspects of reality. > > > > I'm not gloating because some here were proved wrong. > > > Not so much wrong, but the way they expressed what SR says was poor > > Yes, and more than one person managed to "express themselves poorly" > on more than one occasion, even despite my repeated corrections.
From: PD on 3 Mar 2010 17:59 On Mar 3, 11:52 am, Ste <ste_ro...(a)hotmail.com> wrote: > On 3 Mar, 12:30, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > wrote: > > > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > > >> You say you are here to learn about SR. > > > > I am here to learn more about the *conceptual basis* of SR. > > > Minkowksi space time? > > No. How about just spacetime, then, for which there is both a conceptual description and a mathematical description? > > > >> Do you believe SR is true? > > > > I accept it's mathematical form has some obvious truth, yes. > > > Do you believe that it correctly predicts the results of every experiment > > that it claims to? That clocks run slower, > > No. In SR, clocks *appear* to run slower as you are increasing your > distance from the clock. The effect is entirely apparent in SR. That's not the extent of what SR claims. Muons in a circulating ring exhibit time dilation, though they are not receding from the clock at all, for example. > > > and 80 foot ladders can fit through 40 feet barns, > > It remains slightly unclear, but I'm inclined to say no, although it > can certainly be made to appear to happen in certain circumstances. I would be cautious about inclinations. It is pretty easy to make the distinction between "appears to" and "does". For example, if I hold the doors of the barn open to admit the pole, and at a carefully chosen moment, briefly close both barn doors simultaneously and then open them again, in such a way that I can verify that the both ends of the pole had entered the barn before I closed both doors, then I can be pretty sure that the pole was wholly in the barn. I can also then check whether there were any strike marks on the barn doors where the pole would have struck them. If there are none, then this pretty well unambiguously tells you the pole WAS inside the barn, not just appeared to be inside the barn. If you think those events (no marks on the barn doors, both doors closed simultaneously after entry of the pole) can be observed while still maintaining the pole does not fit in the barn, you'll have to explain to me how this is. > > > and that the speed of light is measured the same in > > every intertial frame of reference and this speed is independent of the > > speed of the emitter, receiver, and underlying medium of transmission? > > Yes. I think I've been able to reconcile this partially, but only > vaguely and within a definitely non-standard conceptual framework, and > it is forced to completely dispense with any corpuscular form of > matter, and instead relies wholly on fields. Unfortunately it's > probably the sort of thing that physicists spend their lives thinking > about and never quite put their finger on. Aha. I hope you did not sprain your wrist while hand-waving. > > > If you believe all of those things, then you are saying more than "SR has > > some obvious truths in its mathematical form" you are saying it is an > > accurate portrayal of reality - ie, what happens when you conduct those > > experiments, what physically and actually happens, is exactly as predicted > > by Relativity. > > I think we all agree that SR portrays reality, but none of us seem to > be able to agree on what kind of reality it portrays. Do you believe there is more than one kind of reality? Namely, do you believe there is a reality that matches your expectations for the orderliness of that reality, and another reality that does not necessarily meet those expectations? > > > If, on the other hand, you do not believe in the twin "paradox" actually > > happening, you don't believe in SR. > > We resolved the twins paradox months ago. The astronaut twin undergoes > asymmetrical acceleration, and that is why he returns younger. Yes, but that is still very much the prediction of SR. > > > If you do believe the predictions of SR > > that one twin is older, then you believe that time dilation is more than > > some mathematical fiction, its what actually happens in the real world. > > On the contrary. The involvement of acceleration, which is the domain > of GR, makes me wonder why this is held to be a paradox in SR at all. This is incorrect. SR can handle acceleration just fine. What matters here, and what marks the difference between the twins, is the straightness of the path (a special term called "worldline" in physics) in spacetime. Straighter paths consume longer "proper time" (another specialized term in physics). > And yes, the acceleration causes real effects for the astronaut twin. Yes indeed, and it is remarkable that the effects are precisely in the quantity that is predicted by SR. > > > So, when relativity predicts that one twin will age more than the other, is > > this just some mathematical truth, or is it what really happens as well? > > It really happens, due to acceleration. SR predicts the amount, and yes it is due to the acceleration. > > > So, do you believe that SR is correct in its prediction (for example) that > > if one twin were to be sent off into space at 0.9c for 10 years they would > > have aged less on their return than the twin that stayed at home? > > I'm not sure SR does predict this. As I understand it, GR is required > to predict this effect. Then you do not understand it correctly. > The problem for SR was, as I understand it, > explaining why SR *doesn't* predict that effect. This appears to be made up from whole cloth, cementing the impression that you do not understand it correctly. > > > Do you agree its correct when it says that an 80 foot ladder could fit > > inside a 40 foot barn? > > No, I'm not confident about that prediction. I think it's more likely > to be an apparent effect. See above. > > > You seem to agree they are "mathematical truths". Do you also agree those > > equations correctly predict the outcomes of real world experiments, which > > means they are far more than simply "mathematical truths"? > > The question is of interpreting the mathematical predictions. As I say > above, there is a difference between what is real and what is merely > apparent. See above regarding the pole and the barn. In terms of the observations given, you'll have to explain to me how the pole would have really NOT fit into the barn (but only apparently) and been consistent with the observations noted.
From: Bruce Richmond on 3 Mar 2010 21:52
On Mar 3, 8:29 am, Jerry <Cephalobus_alie...(a)comcast.net> wrote: > On Mar 3, 6:28 am, Bruce Richmond <bsr3...(a)my-deja.com> wrote: > > > I understand it and think it is correct. > > > My position is that far more people would understand it if it was > > explained differently. > > It is generally accepted by most legitimate posters on these > newsgroups that Einstein's original two-postulates axiomatic > approach to the development of relativity is somewhat archaic and > difficult to follow, to judge by the numerous crackpots who > stumble at the very first steps in his derivation. Oh, and the crackpots catch right on to the newer methods? ;) > You prefer Bondi's presentation of Milne's derivation, which > goes "backwards" starting with the Doppler effect. I also like > Bondi's approach which is quite intuitive, but after rederiving > all of Einstein's famous results, the reader is left somewhat > dangling. How does one proceed from there? Bondi's approach is > still, at its core, a classic geometric development of the > subject. Actually I do not prefer Bondi. I suggested him for Ste only to give him a different perspective, and to steer him away from Taylor and Wheeler. > By analogy: One does not design a skyscraper using Euclid's > Elements, and one does not get to General Relativity through > either Einstein's original or Milne's "inverted" axiomatic > development of relativity. It's just too cumbersome a way to > get there. Since you like analogies, for a starting pool player it is better to go for the easy shot and make it than to try for a more difficult shot with a better leave and miss. Few of the posters here will go on to GR. I think the way Einstein presented SR in "Relativity" is probably the easiest way to understand, with a few clarifications added. It was the easiest way that he could see it. The new methods become clear with hindsight, but the new student doesn't have hindsight. > Proceeding forward means presenting Minkowski spacetime. The > Minkowski spacetime approach to relativity in essence replaces > the two postulates with a single assertion: "The geometry of the > universe is accurately described (in low gravity fields) by a > four dimensional manifold with properties as follows..." It still keeps the speed of light a universal constant c. > Taylor and Wheeler, which I like and you hate, start with this > single "postulate" and spend the rest of the book familiarizing > the reader with the implications of this visualization of the > universe. If the reader is diligent, by the time they finish the > book, Minkowski spacetime will have gone beyond mere mathematical > manipulation, but will have become a coherent, consistent, and > best of all, highly intuitive mental construct by which the > reader apprehends relativity. > > Your main objection seems to be that Taylor and Wheeler don't > bother trying to justify relativity. T&W just want the reader > to accept that the battle has been won. Relativity works, so > the reader should just get on with learning the most efficient > way to work with it, et cetera. > > You obviously don't like that attitude. > > Jerry No, I don't. That's just learning how to crunch numbers. |