Known physics defeated by simple puzzle?
in [Relativity]
|
From: Inertial on 7 Apr 2010 01:19 "Sue..." <suzysewnshow(a)yahoo.com.au> wrote in message news:6db9453e-2e8f-4738-94c8-5f87db3d3e65(a)o30g2000yqb.googlegroups.com... > On Apr 7, 12:09 am, "Inertial" <relativ...(a)rest.com> wrote: >> "Sue..." <suzysewns...(a)yahoo.com.au> wrote in message >> >> news:e4994a4b-93da-4ece-bd88-077ab91ec886(a)r27g2000yqn.googlegroups.com... >> >> >> >> > On Apr 6, 9:39 pm, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> >> > wrote: >> >> <SNIP> >> >> >> > Any change in velocity involves acceleration, because that is what >> >> > acceleration is. >> >> >> >>> >> > Indeed, a bullet that flies past >> >> >>> >> > your ear undergoes a dramatic change of relative velocity to >> >> >>> >> > you >> >> >>> >> > as >> >> >>> >> > it >> >> >>> >> > passes (it approaches and then recedes), >> >> >> >>> >> No .. it doesn't >> >> >> >>> > I would argue that it does, >> >> >> >>> And you'd lose. It has the same velocity the whole time (unless >> >> >>> you >> >> >>> include >> >> >>> slowing due to air-resistance, and acceleration due to gravity .. >> >> >>> but >> >> >>> I >> >> >>> don't think that is what you meant) >> >> >> >> I don't see how this can be true. >> >> >> > Then thingk >> >> >> >> The bullet changes angle, distance, >> >> >> > You get that because it is moving .. not because of acceleration >> >> >> >> and speed, and direction, relative to the head as it passes. >> >> >> > No .. it doesn't. It has the same velocity and direction the whole >> >> > time >> >> > in the head's frame of reference. it is moving at a constant speed >> >> > in >> >> > a >> >> > straigh line (we are ignoring air reistance and gravity here) >> >> >> >> Are you sure we aren't arguing over the difference between >> >> >> "velocity >> >> >> relative to a coordinate system" (which I think is what you mean), >> >> >> and >> >> >> "velocity relative to each other, with no coordinate system in >> >> >> play" (which is what I mean - if indeed I'm using the right words >> >> >> to >> >> >> describe it)? >> >> >> > No .. we are arguing over your completely misunderstanding the >> >> > motion >> >> > of a >> >> > bullet. >> >> >> No, the problem is that Ste does not understand basic concepts like >> >> acceleration, and hence basic Newtonian physics. >> >> > ==================== >> >> >> A pre-requisite, I would have thought, for understanding SR. >> >> > Actually, if one never learns of Newton's light-corpuscles >> > SR isn't needed to unlearn them. >> > ============== >> SR does not depend on whether light is corpuscular or not > > <<Consider a light wave which propagates along > the x-axis in S with velocity c. According > to the Galilean transformation, the > > --> apparent speed <-- > > of propagation in S' is c-v, which violates the > relativity principle.>> > http://farside.ph.utexas.edu/teaching/em/lectures/node109.html Yeup .. do you see how it is described as a wave there? Not as corpuscular. Probably not. > Would you care to elaborate how the speed > of light could acquire the *apperance* > indicated by the formula? You think waves cannot have speed? That only corpuscles can? SR doesn't depends on any particular means of propagation for light .. only that the speed at which it does so between any two points where you measure it is c.
From: Ste on 7 Apr 2010 03:01 On 7 Apr, 05:08, "Inertial" <relativ...(a)rest.com> wrote: > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > >> > Again, hidden in the meaning here is 100km/h > >> > *relative to what*. An object cannot travel at *both* 100km/h *and* 50 > >> > km/hr *relative to me*. > > >> I didn't say it could. But we are talking about things being real.. you > >> claim that all observers have to agree about the value for it to be real. > > > Yes, I do say that! > > So velocity is not real, momentum is not real, kinetic energy is not real, > length is not real, time is not real etc etc. > > Is that REALLY what you want to be saying? But I'm not saying that, am I? You're the one putting these words in my mouth. > >> As different observers disagree about what the velocity of any object is, > >> that means its velocity isn't real. > > > No. As I just explained, "an object cannot travel at both 100km/h and > > 50 km/hr relative to me." > > Velocity is measured by each observer relative to his own frame of > reference. That's the whole point. No, the whole point is that the "frame dependence" of the measurement is because, in reality, we're actually measuring the speeds relative to two different objects. As I said, it is perfectly consistent with the laws of physics to say that an object is travelling at 100kmh relative to observer A, and 50kmh relative to observer B - that is not contradictory, and both observers agree on both statements. It is however contradictory to say that "the ladder fits in the barn" and "the ladder doesn't fit in the barn", provided that we're talking about the same ladder and barn in both cases (which we are). > > The question, then, is how when we're *definitely* talking about the > > same two objects throughout, the ladder and the barn, we can possibly > > say that "the ladder fits the barn" and "the ladder doesn't fit the > > barn". > > Because 'fitting' is a frame dependent value. > > By your silly definition, it is not 'real' in just the same way that > velocity, and momentum, and kinetic energy are not 'real'. > > You tried to get around this by saying the everyone agrees about the speed > wrt that an some object moves (even though in SR they do not). Similarly, > everyone would agree that (assuming you are at rest wrt the barn) you > measure the pole as fitting in the barn. The problem here Inertial is that you've slipped back into merely reaffirming the bald truth of your statements about SR. I've explained how the language used to describe relative velocity is not self- contradictory in the way that it is contradictory to say that "the ladder fits and doesn't fit". I've also explained that, with relative velocity, all observers agree on all measurements. I've also discussed how audio Doppler works, and how the "apparent" change of received frequency involves no change of source frequency - hence, it does not entail a "real" slowing of the source vibration, but is an "illusion". Again, with a proper level of interpretation (i.e. an awareness of the Doppler effect), all observers agree about the invariance of the source frequency. I've even discussed how a "real" simultaneous slowing of two stationary, space-separated clocks can, with a sufficient amount of naive reasoning, lead one to conclude (wrongly) that a distant clock has fallen out of synchronisation. I've also pointed out that, if these clocks are moving, then trying to ascertain the reality of whether the clocks are synchronised or not becomes even more confounded. Indeed, if we hold axiomatically that 'c' is always constant, then it follows that either time must have suddenly slowed down locally, or the distances between the local and distant clock must have suddenly "contracted". The fact that I can discuss all these examples, and not get a response along the lines of "Yes, I know exactly what you mean Steven, and you're quite right about how you describe these effects/scenarios. But with SR, there is more, on top of those effects you've already described, and it works like this ...", and for no one to be able to give an explanation that incorporates the points already raised and which does not resort to simple affirmations of the truth of their assertions, leads me to believe that I might be asking the blind to lead the blind. > > And to be clear, your analogy to relative speeds is an illogical > > analogy, > > No .. its not > > > because with relative speeds, you are actually talking about > > different reference objects. > > And so are yoiu when saying that some observers say the pole fits in the > barn in their frame and others say it does not. No we aren't. The property of "fitting" is a relationship between the ladder and the barn. We are talking about the same ladder and barn in all cases, in a way that we are *not* when we discuss relative velocity between observer and object, where there is an implicit change in the observer being referred to in the measurement. > > Here, we are not saying "the ladder fits > > barn A, and does not fit barn B", or "the barn accomodates ladder A, > > but does not accomodate ladder B". > > Neither, when we are talking about an object having speed of both 50km/hr > and 100km/hr, are we talking about two different objects having that speed. *Yes*, Inertial, we are. We are talking about the object in question having a speed of 50kmh relative to one object, and a speed of 100kmh relative to a *different* object than the first. There are, essentially, three objects being referred to here. If we go back to the coin-on-plane scenario, the three objects are: firstly, the coin; secondly, the plane/the passenger; and thirdly, the Earth/the man on the ground. And for any two of those three objects, there is an invariant velocity that all observers agree on. > What we are saying is that 'the ladder fits between the barn doors > simultaneously according to A, but does not fit between them simultaneously > according to B' .. because 'simultaneously' is frame dependent (ie you would > say it is not real) > > > Whereas, when we talk of relative > > velocity, we are saying "the ladder travels at 100km/h relative to > > observer A, but travels at 50km/h relative to observer B". > > The ladder fits in the barn according to A and does not fit according to B' > Same thing. No it isn't, because the two objects to which the property of "fitting" applies, namely the ladder and barn, are referenced in both measurements. Unless you're saying that the *observer himself* must be referenced in the measurement, but that's not materialism - it's going back to saying that the tree falling in the forest only makes a sound if an observer heard it. > > And indeed, > > we would both recoil at the suggestion that "the ladder travels at > > 100km/h relative to observer A, but also travels at 50km/h relative to > > observer A" - we would both agree that this statement would be absurd. > > yes .. just as we would if we said that the barn-frame observer says the > pole both fits and doesn't. But, despite you obfuscation and trying to > distract from what is actually being discussed .. that is not the case It's not obfuscation. My arguments are perfectly reasonable. And my question is this: "does the ladder fit with both doors shut, or not?". It cannot fit and not fit at the same time. There are only two objects, ladder and barn. You can't say "according to the barn, it fits, but according to the ladder, it doesn't", because then you have two objects that disagree about their relationship with each other, and indeed make mutually exclusive and contradictory statements about their relationship.. > >> >> All pitch is apparent. > > >> > But the source frequency isn't. > > >> We are talking about pitch of sound (a wave in a medium). Not the rate > >> at > >> which something vibrates (that causes the sound). > > >> The rate of vibration of the source is the same for all observers > >> (ignoring > >> relativistic effects). The frequency of sound is not. So, according to > >> you, the pitch you hear is not real. > > > But if you want to become pedantic about it, then what do *you* mean > > by frequency? > > Look it up > > > Don't you really mean the "vibration of the receiver"? > > The number of cycles of the wave that travel past a given point in a given > time. > > This will correspond to the vibrations of a receiver at rest at that point. > > It will not correspond to the vibrations of the source if the source is > moving But nor will it correspond to the vibrations of the receiver if the receiver is moving. > > After all, if the "vibration of the source" is not synonymous with > > "the frequency of sound", > > no .. it isn't > > > then why is the "the vibration of the > > receiver" supposedly synonymous with "the frequency of sound". > > Because it is at rest in the frame of reference in which we are determining > the frequency. Lol! It sounds like you're giving the receiver an unnecessarily privileged position here. > > And > > indeed, if the "frequency of sound" corresponds to neither the source > > vibration or the receiver vibration, then what on Earth is the > > frequency, and how was it ascertained? > > See above > > > That said, the question is not about the "frequency of the > > sound" (however we define it). The real question is how a vibration of > > the source translates into a vibration of the receiver - and to > > explain why those vibrations are not equal in certain circumstances. > > That's very easy to explain > > > With that in mind, I stand by my earlier definitions of talking about > > the "source frequency" and "received frequency", and that is precisely > > why I began at the outset by qualifying the word "frequency" with > > either "source" or "receiver". > > You can happily talk about those. Source frequency is frame independent > (ignoring SR for now) and receiver frequency is frame dependent. Right so we agree. And now you understand that, behind every apparent frequency, is the "real" invariant source frequency? And you understand that when I ask whether the frequency has "really" changed, I mean "has the source frequency of the sound changed"? > Receiver frequency for an at-rest receive is the same as the wave frequency > in a given frame of reference This is besides the point - I already know all the ins and outs of sound. The important point is that we've established the meaning of "source frequency" and "received frequency", and established that a change in the received frequency does not necessarily entail a change in the source frequency - the change in the frequency of the sound originating from the source can be merely "apparent" change. > > Indeed, as shown above, it is probably meaningless to talk about "the > > frequency of sound" without making reference (implicitly or > > explicitly) to either the actual source of the sound, the receiver of > > sound, or both, because in order to ascertain the frequency, you must > > specify the object against which the "frequency" is being measured. > > > And finally, just to refresh our memories, my point here was that a > > change of received frequency involves no "real" change of any part of > > the source mechanism, and in the same way, a change of apparent length > > involves no real change, and a change in apparent time or simultaneity > > involves no "real" change (or, at least, does not *necessarily* > > involve any real change). > > It is two different things being measureed. There is no problem that a real > difference in receiving frequency can correspond to NO difference in source > frequency. They are NOT measurements of the same thign. I agree. > >> >> >> The timing of the doors is PART of the scenario. It states that > >> >> >> they > >> >> >> shut > >> >> >> (briefly) at the same time according to any observer (or observers) > >> >> >> at > >> >> >> rest > >> >> >> wrt the barn. The pole fits between them when they are > >> >> >> simultaneously > >> >> >> shut > > >> >> > Yes, but that depends on simultaneous *according to whom*, > > >> >> It is frame dependent > > >> > No, as I explained in a previous post, there are two definitions of > >> > simultaneity. > > >> I'm not reading your previous post .. please exaplin you own particular > >> notion of simultaneous > > > I explained that events are "simultaneous" if the events would have > > appeared to occur simultaneously if information could propagate > > instantly across space (which, of course, it doesn't in reality). > > Then it is the same notion, and is frame dependent, and so not 'real' Eh? There is no frame dependence in my definition of "simutaneity". An event that occurs at a certain time, occurs at the same time at every corner of the universe. And if certain clocks disagree about the timing of that event, then the problem is that the clocks themselves are not synchronised, and may well be measuring different rates of time (or more accurately, differents rates of change). > >> > I pretend that information travels instantaneously. > > >> That has nothing to do with differences in simultaneity. You are > >> confused > >> and think it has something to do with transit times of information about > >> clocks (ie just an illusion .. like how you can see lightning before > >> hearing > >> the thunder) > > > Yes, I certainly am confused. That's why we're having this discussion. > > Then you really should do more listening than arguing. And ask questions > rather than assert things (and people who understand better than you) are > wrong. I do ask questions. My latest spate of posts are an exercise in hammering out the meaning of words, so that you can understand my questions and I can understand your reponse. > >> >> > and because > >> >> > (as Paul Draper has noticed) I use a different definition of > >> >> > "simultaneous" to "most of the physics community". > > >> >> Then that is your problem. And you should NOT use a word like > >> >> 'simultaneous' that has a different meaning to you than it does to the > >> >> rest > >> >> of the world (not just physics). Pick a different word (or phrase) > > >> > Let's call it "Steven-simultaneous" then. OK? > > >> Please explain this fanciful notion > > > Lol. As above. > > It is the same notion then, and you are simply wrong that it is 'real' (your > word for frame independent). No, my concept of simultaneity is not "real" - that is, it doesn't exist anywhere in nature, because as far as we know, information does not propagate instantly in nature. The point about my concept of simultaneity, however, is that it allows to talk about what is *really* happening, without confounding the question with concerns about propagation delays. To remind you of the value of such a conception of simultaneity, I refer back to my "breakfast time" analogy, where the importance of the question is not when you received information of the breakfast being eaten, but at what time the breakfast was actually eaten. > >> > And what is more, I'm saying that whatever I said previously, > >> > I can tell you're still attributing a non-shared meaning to the word > >> > "real". > > >> That is your problem. I have already told you the appropriate terms to > >> use > >> to disambiguate. > > > But the problem with "frame dependent" and "frame independent", which > > were your suggested replacements for the words "apparent" and "real", > > They are the correct physics terminology. You should use them. But they don't *mean* the same things as what I mean by "apparent" and "real". > > is that I'm still no clearer about whether something that is "frame > > dependent" is "apparent" in the way that the spaceship on the monitor > > is, or whether it is "real". > > The image is 'real' on the monitor, it only 'apparent' in the sky to someone > looking at the monitor instead of directly at the sky. But the question was not "what do you see on the monitor". The question was "is the spaceship really in the sky". And you are right, it is apparent to the person looking at the monitor - that we all agree on. The question was "is it real, or is it merely apparent", given that I'm not asking you to say verbatim what you see, and nor am I asking you to describe the state of the pixels on the monitor, I'm asking you to give me information about the objects depicted on the monitor (the spaceship and the sky). > > And > > yet, when I ask you "has it contracted mechanically" (in other words, > > similar to the compression that a spring would undergo), you say > > "yes" > > No .. I didn't. Stop lying about what I say. > > I said the distance (ie length) between the atoms is smaller (they are > closer together). > > And that is also frame dependent. Perhaps someone else said "yes" to the mechanical question, but in any event you're describing exactly the same situation - that of atoms being "closer together" in one direction. And as I've said, if the atoms are *really* closer together, then this would show up as stress and strain in the material, and also circular bearings/nuts and bolts would either no longer rotate or would rapidly work-harden and fracture when rotated. > > - whereas, by definition, if it has contracted mechanically, > > then it would be frame independent. And, for example, if the ladder > > had nuts and bolts attached to the side of the ladder, then this > > mechanical contraction would mean that the bolts would no longer turn > > in the nuts, because they would now have an ellipsoid profile. > > Yes .. the nuts and holes really do become shorter in diameter in one > direction than the other. That is frame dependent. > > That doesn't mean they cannot turn. It does if they have "really" moved closer together. > > Or even > > if the bolts did turn, the stresses in the metal would be overwhelming > > as a result of the severe deformation involved in maintaining the same > > ellipsoid profile relative to the direction of travel as the bolt > > turned (like rolling blu-tac between squeezed fingers). And of course, > > the opposite to a "mechanical" explanation is a visual one - that is, > > an explanation that involves describing how things interact > > electromagnetically, and showing how those electromagnetic principles > > lead something to *visually* appear different, without any change at > > the source (like how the audio Doppler effect describes a change of > > received frequency with no change of source frequency). > > It is not just visual. if it was, then the pole would not fit within the > barn doors .. it would be just an illusion. Indeed. > That is NOT what SR says it is. But does it say this, or does it merely say this is what will *appear* to happen? Indeed, does the maths of SR say anything *at all* about the real nature of what is observed, or does it merely quantify something that we know we observe, but are not quite sure how to interpret? > > There is no ability, on > > your part, or anyone else's part here, to translate from the > > specialised language that they've acquired to an everyday vocabulary, > > in order to discuss what is happening in a meaningful way. > > No .. the problem is your insistence on using terms incorrectly, and lying > about what is said. I did not lie Inertial. > > This suspicion is reinforced even more when you have the likes of Paul > > Draper, who is a physics teacher, saying things like "what is > > simultaneous in one frame is never simultaneous in another", > > Which in general is correct .. in some specific cases it is not. It's not correct at all. It's completely false. To say it is "correct most of the time" is ludicrous reply for self-professed "experts" to make towards someone they're ridiculing as having "no understanding", and whom they are supposed to be teaching! Indeed, it is about as incorrect as saying "the audio frequency measured by one receiver is never the same as that measured by another receiver" - and it is no excuse to say "well, it's correct most of the time, except for the specific circumstances in which the relative velocity is the same between source and the two or more receivers in question". > > and I'm > > able to correct him despite not knowing a *single* equation of > > relativity. > > A minor pedantic point. Which you keep going back on as if it was some sort > of victory for you. Yes, because it *reinforces* the very argument that I've been making from the start, that not only can you understand relativity without the maths, but the complexity of the maths involved actually leads people to believe that relativity is more complex than it really is. > > And my point is not to show Paul up for a careless > > mistake, > > Yes .. it is My only reason for mentioning it is to attack the pretensions that abound here. Not least to show that the "experts" here have a significant problem with communication. > > but to show just *how little* mathematics I needed to know > > (i.e. none) in order to immediately identify a situation where his > > statement would be false, and he had to concede that I was, in fact, > > correct. > > Your lack of understanding is far more profound. that you fluked getting > something right doesn't alter that. Lol! It wasn't a fluke. All it required was to reason that, in all the examples Paul was giving, the relative movements were asymmetrical, whereas I pointed out the situations where the relative movements were symmetrical, and hence proved to myself that at least some of the explanation for non-simultaneity lay simply in how events and observers are moving in relation to each other, and how that affects the electromagnetic interaction between them. > >> Who said they were closer together in EVERY frame ? > > >> You just can't seem to cope with the notion that different observers > >> measure > >> different lengths. you are happy that they measure different velocities > >> nad > >> momenum nad energy etc. Why do you have a stumbling block about length? > > > For the reasons already detailed. > > So you do admit it is a stumbling block .. first step to making some > progress I admit it is a stumbling block - for whom, non constat. > > Hence, since > > length is really just a instance of a distance measurement between two > > points, I'm naturally resistant to the idea that observers can > > disagree on the distance of separation between the same two points. > > Because you 'naturally' think SR must be wrong and classical mechanics must > be right? No it's simply because your account of SR has not been made out convincingly, whereas classical mechanics is fairly straightforward and long-settled as a theory. > > Or, > > the "clear" answer, that the source vibration is "really" changing for > > some unknown reason by some unknown mechanism, would be the wrong > > answer. > > That is why one needs to study and understand the physics, and not draw > incorrect conclusions out of ignorance. Indeed. The question is whether ignorance is manifesting itself when certain people insist that length contraction means "the atoms really move closer". > > - indeed, the head cannot have absorbed more energy > > in one frame than another, otherwise you're saying that the damage > > inflicted by the blow is frame dependent. > > The difference in kinetic energy of the hammer before and after the blow is > frame dependent. > > Do you want to see the math? Its very simple Like a hammer blow to the head I want. But yes seriously, I'm interested how the head supposedly suffers a different force of impact depending on the frame.
From: Peter Webb on 7 Apr 2010 03:49 and for no one to be able to give an explanation that incorporates the points already raised and which does not resort to simple affirmations of the truth of their assertions, leads me to believe that I might be asking the blind to lead the blind. ________________________________ I said I wouldn't respond to you, as you have already said you are not learning anything. But what you say above just offensive: 1. It is not "the blind leading the blind". Inertial clearly understands SR, and his explanations are correct. If you can't see it, it is because you are blind. 2. What Inertial has told you is absolutely orthodox SR. The pole really will fit inside the barn if it is moving fast enough, and the travelling twin really will return younger. These are direct predictions of SR. They are not optical illusions or explained by propagation delays. 3. You have to decide which one of the following is true: (a) SR is not a correct theory. If you believe that is the case, then you are saying that pretty much every physicist in the world is wrong about the predictions of SR. Coming from somebody who doesn't even know what "acceleration" is, let alone has ever studied SR, this is a pretty bold claim. (b) SR is a correct theory, but you don't understand it. If that is the case, then the problem is entirely yours and blaming other people for your own lack of comprehension won't help. You don't know *any* physics, yet you accuse people who obviously do know a lot about physics as being bad teachers, and the only evidence you provide of this is that you don't understand the subject matter. Pathetic.
From: Sue... on 7 Apr 2010 06:23 On Apr 7, 1:19 am, "Inertial" <relativ...(a)rest.com> wrote: > "Sue..." <suzysewns...(a)yahoo.com.au> wrote in message > > news:6db9453e-2e8f-4738-94c8-5f87db3d3e65(a)o30g2000yqb.googlegroups.com... > > > > > On Apr 7, 12:09 am, "Inertial" <relativ...(a)rest.com> wrote: > >> "Sue..." <suzysewns...(a)yahoo.com.au> wrote in message > > >>news:e4994a4b-93da-4ece-bd88-077ab91ec886(a)r27g2000yqn.googlegroups.com.... > > >> > On Apr 6, 9:39 pm, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > >> > wrote: > >> >> <SNIP> > > >> >> > Any change in velocity involves acceleration, because that is what > >> >> > acceleration is. > > >> >> >>> >> > Indeed, a bullet that flies past > >> >> >>> >> > your ear undergoes a dramatic change of relative velocity to > >> >> >>> >> > you > >> >> >>> >> > as > >> >> >>> >> > it > >> >> >>> >> > passes (it approaches and then recedes), > > >> >> >>> >> No .. it doesn't > > >> >> >>> > I would argue that it does, > > >> >> >>> And you'd lose. It has the same velocity the whole time (unless > >> >> >>> you > >> >> >>> include > >> >> >>> slowing due to air-resistance, and acceleration due to gravity ... > >> >> >>> but > >> >> >>> I > >> >> >>> don't think that is what you meant) > > >> >> >> I don't see how this can be true. > > >> >> > Then thingk > > >> >> >> The bullet changes angle, distance, > > >> >> > You get that because it is moving .. not because of acceleration > > >> >> >> and speed, and direction, relative to the head as it passes. > > >> >> > No .. it doesn't. It has the same velocity and direction the whole > >> >> > time > >> >> > in the head's frame of reference. it is moving at a constant speed > >> >> > in > >> >> > a > >> >> > straigh line (we are ignoring air reistance and gravity here) > > >> >> >> Are you sure we aren't arguing over the difference between > >> >> >> "velocity > >> >> >> relative to a coordinate system" (which I think is what you mean), > >> >> >> and > >> >> >> "velocity relative to each other, with no coordinate system in > >> >> >> play" (which is what I mean - if indeed I'm using the right words > >> >> >> to > >> >> >> describe it)? > > >> >> > No .. we are arguing over your completely misunderstanding the > >> >> > motion > >> >> > of a > >> >> > bullet. > > >> >> No, the problem is that Ste does not understand basic concepts like > >> >> acceleration, and hence basic Newtonian physics. > > >> > ==================== > > >> >> A pre-requisite, I would have thought, for understanding SR. > > >> > Actually, if one never learns of Newton's light-corpuscles > >> > SR isn't needed to unlearn them. > > > ============== > >> SR does not depend on whether light is corpuscular or not > > > <<Consider a light wave which propagates along > > the x-axis in S with velocity c. According > > to the Galilean transformation, the > > > --> apparent speed <-- > > > of propagation in S' is c-v, which violates the > > relativity principle.>> > >http://farside.ph.utexas.edu/teaching/em/lectures/node109.html > > Yeup .. do you see how it is described as a wave there? Not as corpuscular. > Probably not. > > > Would you care to elaborate how the speed > > of light could acquire the *apperance* > > indicated by the formula? > > You think waves cannot have speed? That only corpuscles can? > > SR doesn't depends on any particular means of propagation for light .. only > that the speed at which it does so between any two points where you measure > it is c. Consider a remedial reading course so you won't be answering questions that were never asked. Sue...
From: paparios on 7 Apr 2010 09:03
On 7 abr, 03:01, Ste <ste_ro...(a)hotmail.com> wrote: > On 7 Apr, 05:08, "Inertial" <relativ...(a)rest.com> wrote: > > > > yes .. just as we would if we said that the barn-frame observer says the > > pole both fits and doesn't. But, despite you obfuscation and trying to > > distract from what is actually being discussed .. that is not the case > > It's not obfuscation. My arguments are perfectly reasonable. And my > question is this: "does the ladder fit with both doors shut, or not?". > It cannot fit and not fit at the same time. There are only two > objects, ladder and barn. You can't say "according to the barn, it > fits, but according to the ladder, it doesn't", because then you have > two objects that disagree about their relationship with each other, > and indeed make mutually exclusive and contradictory statements about > their relationship.. > Again, your problem (as anybody else here and everywhere clearly understand the gedanken) is that you misunderstand basic physics. "A nuclear blast happens" is the description of an EVENT. when you affirm "It cannot fit and not fit at the same time" you are clearly wrongly reading and understanding the gedanken. For it is quite clear that, from the point of view of the 20 meters pole, it is impossible that it fits inside a 4.37 meters barn. You see, the relevant events, which have to be consistent, are the barn doors closing and opening. In the barn frame of reference (FOR), both barn doors close at the same time and they open at the same time (they are closed for 1 nanosecond). In that condition the contracted 8.37 meters pole is, for a brief lapse of time, inside a closed 10 meters barn. In the pole FOR, the 20 meters pole sees the barn approaching at 0.9c and the back door of the 4.37 meters barn closes and opens, just a brief instant of time BEFORE the front of the pole reaches that location (the 20 meters pole is at that time 4.37 meters inside the barn). After that, the 20 meter pole sees the 4.37 meters barn front door closing and opening, just a brief instant of time AFTER the back of the pole just passed through that location (the 20 meters pole has at that time 15.63 meters of its length outside the barn and its back 4.37 meters inside the barn. In both FOR, the 10 meter barn doors closed and opened and the 20 meters pole did not touch any part of the barn. Nice and easy. Miguel Rios |