A constant speed of light in all reference frames? Surely you can't be serious.
in [Relativity]
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From: Peter Webb on 1 Mar 2010 08:31 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:ae1e0767-bbd7-4260-9be9-c5ad9a92d17f(a)v20g2000yqv.googlegroups.com... On 1 Mar, 07:24, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > But clearly if the two *observers* are moving relative to each other, > then this is the definitive proof that events can be simultaneous when > measured from more than one reference frame. > > ____________________________________ > Can appear simultaneous, yes, of course. That is a standard part of SR. Not "can appear simultaneous". *Is simultaneous*. > And in some > circumstances, the simultaneity also aquires an "absolute" character, > in that the events would be observed to be simultaneous if the two > observers were able to synchronise their clocks by a form of > instantaneous communication. > > ________________________________ > "if the two observers were able to synchronise their clocks by a form of > instantaneous communication.", or if pigs could fly, or Star Trek > instantaneous teleporters existed, or I was the President of China. > > Show me how they can synchronise their clocks through instantaneous > communication and you have an argument. I'm not saying you can. I'm saying *if you could*. The definition of "simultaneous", for any sane person, is always going to be "if information could travel instantly". _____________________________ Which apparently it can't, or not in this Universe, anyway. But if you insist on relying only on real-world tests, _________________________ I don't, but experimental evidence is always great ... then you can always put a third observer equidistant from the two observers, and this person would receive a signal from both observers simultaneously. __________________________________ Yes you could. Indeed, you could set up bazillions of experiments. Got any that disprove SR? No? I thought not. Next!
From: Peter Webb on 1 Mar 2010 08:43 >> >> Haha! And these pillocks wonder why I won't go out and spend a grand >> in money and 6 months of time, working through their extensive reading >> lists! >> >> ________________________________ >> I don't wonder why don't learn SR. I think its because of two reasons. >> Firstly, you are lazy. Secondly, you have such a low opinion of your own >> abilities that you think you won't understand it anyway, so you think its >> a >> waste of time. > > Guffaw! OK, you tell us. It wouldn't cost you a "grand in money" as you said above. How long it takes you is a question of how far you want to get, and where you are now. To understand Minkowski spacetime you don't need calculus (though it obviously helps), but you do need to know what "imaginary numbers" are, and what vectors are. These are both taught in high school. If you understand both of these concepts, picking up what Minkowski is about is very easy. You can't expect to learn SR without making some effort.
From: Peter Webb on 1 Mar 2010 08:51 >> > Stop making me laugh Peter. I have surely forgotten more about >> > evolution than you'll ever know, because you typify arrogance and >> > closed-mindedness. >> >> I laughed when you first said what you thought evolution was about. >> >> You said it explained the origon of life (amongst other things). >> >> Evolution says nothing about that at all. > > Guffaw! "Evolution says nothing about the origin of life at all". I > wonder if Dirk van de Moortel would like that one for his "immortal > fumbles" page. > Interesting that you have forgotten more about evolution than I will ever know, because I can't actually recall Darwin's theory of evolution as saying anything at all about the origins of life. What do you think it says about the origins of life, exactly? (See. Like I said. You know even less about evolution than you do about SR.)
From: Jerry on 1 Mar 2010 09:15 On Feb 28, 11:20 am, Bruce Richmond <bsr3...(a)my-deja.com> wrote: > On Feb 27, 8:42 am, Jerry <Cephalobus_alie...(a)comcast.net> wrote: > > Spacetime Physics, by Taylor and Wheeler > > > The second edition can generally be picked up used for about $25. > > The first edition is frequently found on eBay with a "Buy it now" > > price of $5 to $10. > > > To Ste: > > I actually prefer the first edition. It is a relatively thin, > > large format paperback that is deceptively easy to skim through > > without understanding. It is not a book for skimming. It has lots > > of problems with solutions, and the only way to truly learn the > > subject is to WORK THE PROBLEMS!!! None of the problems uses > > advanced math. If you can work the problems and get the correct > > answers, only then will you really understand what relativity is > > all about. > > > As Peter pointed out, Minkowski spacetime is a superb conceptual > > model, and not at all difficult to understand provided that you > > take the time to learn it properly. > > > There is no shortcut to learning how to do the math. > > But the math is simple! > > IMO that book stinks for explaining SR. It presents the math but > doesn't provide the underlying reason for the math. To make matters > worse it sometimes assumes the reader knows things without stating > them. For example, in one of the first problems Billy (or whoever) > *sees* a rocket fly by. He sees a spark as it passes a door frame at > such and such a time. We then do some calculations. It was never > mentioned that the times Billy uses are coordinate times read from > clocks at the point where the event takes place, as opposed to the > time on Billy's watch, including travel time. BLATANT FALSEHOOD In my first edition, Taylor and Wheeler devote over five pages to the topic of measuring the coordinates of an event Starting on page 17, I read the section heading and subtopics: Chapter 1.4 The Coordinates of an Event Why use coordinates? Event defined Latticework of clocks Synchronizing clocks in lattice Latticework used to measure the four coordinates of event Lattice spacing depends on scale of physics under study Observer defined Clock records reveal motion of particle through lattice Verifying that lattice furnishes inertial frame Laboratory and rocket frames: axes coincide Laboratory and rocket observers record single event y coordinate of event is same in lab and rocket frames z coordinate of event is same in lab and rocket frames > Another thing I don't like is their constant repetition of how things > aren't what we expect because we aren't used to dealing with the > speeds involved. BLATANT FALSEHOOD I see exactly TWO instances, on page 5 and page 16, where Taylor and Wheeler mention the discrepancy between relativity and intuition. This is NOT constant repetition, unless you can't count beyond 1. > That's BS. Things aren't always what we expect > because we aren't used to switching pespectives. When you are driving > down the road the rain drops that fall straight down for the observer > on the side of the road fall diagonally. There is nothing strange > about that, it is just a different perspective. The goal here should > be to make sense of what you see, not to show how weird they are. A > good book for that is "Relativity And Common Sense" by Bondi. NOT A TEXTBOOK, DOES NOT FORCE READER TO CHECK THEIR UNDERSTANDING Bondi followed Milne in eschewing the two postulates, instead deriving special relativity by starting with the Doppler effect. This is perfectly fine, but the book is not structured as a textbook. It does not challenge the reader to check their comprehension by forcing them to apply the concepts that they have read, not necessarily with understanding. Jerry
From: PD on 1 Mar 2010 09:53
On Feb 27, 9:20 pm, Ste <ste_ro...(a)hotmail.com> wrote: > 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 classical mechanics explain what "space" is. Is that a fault? Nor does Newtonian mechanics explain what "energy" is. Is that a fault? > Nor does SR explain qualitatively what > electromagnetic radiation is, or what its effects are. Nor does the Lewis theory of acids and bases explain genetics. Why should it? > 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". |