Known physics defeated by simple puzzle?
in [Relativity]
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From: Ste on 6 Apr 2010 23:14 On 7 Apr, 00:31, "Inertial" <relativ...(a)rest.com> wrote: > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > >> >> > 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 But it changes relative distance *at different rates* as it travels towards and then away from the head. Hence, even by your own reasoning, this is "acceleration". Incidentally, I just want to remark that I'd accidentally referred to impulse earlier as "absolute 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) But the relative *distance* between the bullet and head changes. Indeed, the bullet approaches and then recedes, and it approaches and recedes at different relative speeds, and at different angles of attack. > > 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. > > >> > A thing cannot fit and at > >> > the same time not fit, > > >> yes it can.. just as it can be travelling at 100km/hr and 50 km/hr at the > >> same time. > > > But that's not true. > > Yes .. it is. Every object travels at every possible speed at the same > time. > > > 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! > 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." 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". And to be clear, your analogy to relative speeds is an illogical analogy, because with relative speeds, you are actually talking about different reference objects. 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". 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". 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. > >> > otherwise that isn't materialism (and it isn't causal > >> > either). Or to repeat my earlier analogy, you can't hit a person over > >> > the head with a hammer, and merely daze him *at the same time as* > >> > cracking his skull wide open. > > >> That's right .. you can't. But that is no a valid analogy. > > > Indeed, because you're wrong about states (or speed, energy, or > > momentum) being subjective. > > I never said they were. Why do you lie about what i say .. is it the only > way you know how to argue? I'm not lying. You said those things were all frame-dependent. > >> > which then translates in different ways into a apparent > >> > received pitch. > > >> 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? Don't you really mean the "vibration of the receiver"? After all, if the "vibration of the source" is not synonymous with "the frequency of sound", then why is the "the vibration of the receiver" supposedly synonymous with "the frequency of sound". 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? 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. 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". 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). > >> >> 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). > > 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. > >> > 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 > >> > "apparent". I want to avoid discussing unrelated topics, especially > >> > when I can tell intuitively that when you use phrases like "do not > >> > have a real basis", > > >> That was what YOU said > > > No that was what *you* said. I did not write the sentence "So > > velocity, momentum etc do not have a real basis, according to your > > logic". > > I didn't say you said that. Stop lying to defend your position. You just did you fool! Let's go through this step by step: 1) *You* used in some long-ago post the phrase "do not have a real basis" - and I said that, intuitively, I could tell you hadn't grasped the meaning of what I meant by "real". 2) You then accuse me, above, of saying "do not have a real basis" - that is, you say that these are my words. 3) I correct you, by insisting that this phrase, (that is, the one quoted), was *your* turn of phrase. 4) Now you accuse me of lying. > > 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", 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". For example, we say that the ladder's length is "frame dependent". 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" - 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. 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). And this is what the real problem is here. 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. And so naturally, from my point of view, this creates a strong suspicion that you're talking the talk, in respect of a subject painstakingly learned by rote, so that you can perform calculations and give correct answers, and yet have no intuitive "deep" understanding of what is actually going on (which is really the kind of understanding that my questions are aimed at). 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", and I'm able to correct him despite not knowing a *single* equation of relativity. And my point is not to show Paul up for a careless mistake, 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. And don't get me wrong, I'm not necessarily saying that you don't have the understanding required to answer my questions, but I am suggesting that my overall experience here (not just from you, but from many other posters) has created a strong suspicion that this is the case, and that what comprehension of physics exists here comes from a strong command of formal mathematics, not an intuitive understanding of physics. Hence, any attempt to step outside of the mathematics and discuss things qualitatively with ordinary words, is apparently doomed to fail. > > But we both agree on those statements - we both agree that I am > > stationary relative to the car, and we both agree that you are not. > > Hence the car *really is* stationary relative to me, and *really is* > > moving towards you. > > Though, according to SR, different observers would measure a different speed > of the car relative to me. Ah, well we're back to presupposing the very thing in question, aren't we? > > If the atoms were *really* closer together, > > They are > > > then the ladder > > would contract in all frames, not just the barn frame. > > 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. Different observers do not measure different velocities between the same objects - at least not in classical mechanics. And nor do they measure different distances - a one meter separation between two objects according to one observer, is the same one meter separation according to another. 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. > >> > And although you insist the length contraction is real, until you > >> > indicate convincingly that you even know how to discern between > >> > appearance and reality, I'm not going believe you when you simply > >> > assert that the contraction is real. > > >> Then use 'frame independent' instead of 'real' .. as that is what you > >> mean. > > >> And use 'frame depenendent' instead of 'apparent' .. as that is what you > >> mean. > > >> If you are going to discuss physics, use the appropriate terms that have > >> well defined meanings. > > > But I am still not clear about whether what is "frame dependent" is > > real or not. > > Stop using words 'real' and 'apparent' .. it is not well defined and causes > confusion It's no better defined that "frame dependent" and "-indepedent", in relation to the questions I'm asking. > > Received audio frequency is "frame dependent", > > Yes > > > but it's > > not clear (rhetorically speaking) whether the change in frequency is a > > change of the *source* frequency or not. > > No .. it is very clear. I know. But if we *didn't know* about the Doppler effect, and we took our observations at face value, then it wouldn't be clear at all. Or, the "clear" answer, that the source vibration is "really" changing for some unknown reason by some unknown mechanism, would be the wrong answer. > > Let's return to what I said above in my previous post. Not only does > > the suns rays, when directed through a magnifying glass, become > > scorching, but the Sun also appears to shrink in size (at least if it > > is in focus). Do we say "the sun has *really* shrunk", or do we say > > "it merely appears to have shrunk"? And indeed, when we go to the > > surface of the sun, we find the sun is just as big as it ever was. So > > does it *really* shrink when you look through a lens, or does it > > merely *apparently* shrink, with no mechanical contraction at all? > > The apparent difference in size due to differences in distance etc are > illusions. Though what you are really measuring is an angle subtended at > the eye, and THAT is a real difference. That real difference causes the > 'illusion' when misinterpretted. Agreed, but all "illusions" are about misinterpretation. > >> > and if there is > >> > a different amount of energy and momentum in the hammer, > > >> There is > > >> > a therefore > >> > different amount of force applied to the skull, > > >> But there is also different momentum and energy in the skull > > > And let me guess. These "different" energies and momentums change in > > perfect proportion, so that the *relative* energy between skull and > > hammer is exactly the same? > > No. The difference in KE of the hammer before and after the strike is frame > dependent. It can't possibly be. The hammer cannot have spent more energy in one frame than another - 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.
From: Sue... on 6 Apr 2010 23:46 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. "Relativity principle" http://farside.ph.utexas.edu/teaching/em/lectures/node108.html Sue...
From: Inertial on 7 Apr 2010 00:08 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:954a413d-1067-4b01-ac45-1f0c0dffc876(a)r27g2000yqn.googlegroups.com... > On 7 Apr, 00:31, "Inertial" <relativ...(a)rest.com> wrote: >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> >> >> > 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 > > But it changes relative distance *at different rates* as it travels > towards and then away from the head. Hence, even by your own > reasoning, this is "acceleration". It does not change its velocity at all. So it is NOT acceleration. By your definition, if you spin a bucket around your head, it dose not move because the relative distance between your head and the bucket is the same. Velocity is NOT the rate of change in distance from a point over time .. it is the rate of change in position over time. You REALLY need to understand the very basics of terminology. > Incidentally, I just want to remark that I'd accidentally referred to > impulse earlier as "absolute acceleration". Didn't really notice. >> > 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) > > But the relative *distance* between the bullet and head changes. Yes it does. But its speed and direction in the frame of reference of the head is the same. > Indeed, the bullet approaches and then recedes, Yes it does. But its speed and direction in the frame of reference of the head is the same. > and it approaches and > recedes at different relative speeds, and at different angles of > attack. You seem to confuse closing speed with velocity. >> > 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. >> >> >> > A thing cannot fit and at >> >> > the same time not fit, >> >> >> yes it can.. just as it can be travelling at 100km/hr and 50 km/hr at >> >> the >> >> same time. >> >> > But that's not true. >> >> Yes .. it is. Every object travels at every possible speed at the same >> time. >> >> > 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? >> 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. According to you, velocity is not 'real'. Closing speed between you and the object is 'real' (if we ignore relativity) > 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. > 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. > 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. 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. > 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 >> >> > otherwise that isn't materialism (and it isn't causal >> >> > either). Or to repeat my earlier analogy, you can't hit a person >> >> > over >> >> > the head with a hammer, and merely daze him *at the same time as* >> >> > cracking his skull wide open. >> >> >> That's right .. you can't. But that is no a valid analogy. >> >> > Indeed, because you're wrong about states (or speed, energy, or >> > momentum) being subjective. >> >> I never said they were. Why do you lie about what i say .. is it the >> only >> way you know how to argue? > > I'm not lying. Then you don't understand what you're saying (which is more likely) > You said those things were all frame-dependent. Yes .. but I never said they were subjective. Frame dependent is NOT the same thing as subjective. They are all objective measurements that are frame dependent. >> >> > which then translates in different ways into a apparent >> >> > received pitch. >> >> >> 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 > 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. > 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. Receiver frequency for an at-rest receive is the same as the wave frequency in a given frame of reference > 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. >> >> >> 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' >> > 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. >> >> > 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). >> >> > it is >> >> > "apparent". I want to avoid discussing unrelated topics, especially >> >> > when I can tell intuitively that when you use phrases like "do not >> >> > have a real basis", >> >> >> That was what YOU said >> >> > No that was what *you* said. I did not write the sentence "So >> > velocity, momentum etc do not have a real basis, according to your >> > logic". >> >> I didn't say you said that. Stop lying to defend your position. > > You just did you fool! No Please, stop lying. > Let's go through this step by step: > > 1) *You* used in some long-ago post the phrase "do not have a real > basis" *YOU* used the phrase 'real basis'. I used the same phrase you used. You said "No, I'm insisting that observations/changes can have a "real" basis, or an "apparent" basis, at least for the purposes of this argument ." > - and I said that, intuitively, I could tell you hadn't grasped > the meaning of what I meant by "real". I understand what you mean .. its not a good use of that word. > 2) You then accuse me, above, of saying "do not have a real basis" - > that is, you say that these are my words. You said things (real things) can have a real basis or have an apparent basis > 3) I correct you, by insisting that this phrase, (that is, the one > quoted), was *your* turn of phrase. It isn't. You used the phrase 'real basis' about things that are real. > 4) Now you accuse me of lying. You are. Or at least being deliberately pedantic, deceptive and manipulative. >> > 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. > 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. Neither of those are uses of 'real' and 'apparent' correspond to frame dependent or frame-independent .. which is PRECISELY why you should not use 'real' and 'apparent' when you mean 'frame independent' or 'frame dependent'. The words 'real' and 'apparent' have other meaning. > For example, we say that the ladder's length is "frame dependent". It is > 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. > - 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. > 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. That is NOT what SR says it is. > And this is what the real problem is here. Yes .. yours > 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. > And so > naturally, from my point of view, this creates a strong suspicion that > you're talking the talk, in respect of a subject painstakingly learned > by rote, so that you can perform calculations and give correct > answers, and yet have no intuitive "deep" understanding of what is > actually going on (which is really the kind of understanding that my > questions are aimed at). The one without understanding here is you .. don't project your faults onto me > 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. > 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. > And my point is not to show Paul up for a careless > mistake, Yes .. it is > 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. > And don't get me wrong, I'm not necessarily saying that you don't have > the understanding required to answer my questions, but I am suggesting > that my overall experience here (not just from you, but from many > other posters) has created a strong suspicion that this is the case, no .. you are incapable of understanding the answers .. There is a big difference > and that what comprehension of physics exists here comes from a strong > command of formal mathematics, not an intuitive understanding of > physics. Hence, any attempt to step outside of the mathematics and > discuss things qualitatively with ordinary words, is apparently doomed > to fail. Yes .. you are doomed to fail if that is what you are doing. >> > But we both agree on those statements - we both agree that I am >> > stationary relative to the car, and we both agree that you are not. >> > Hence the car *really is* stationary relative to me, and *really is* >> > moving towards you. >> >> Though, according to SR, different observers would measure a different >> speed >> of the car relative to me. > > Ah, well we're back to presupposing the very thing in question, aren't > we? No >> > If the atoms were *really* closer together, >> >> They are >> >> > then the ladder >> > would contract in all frames, not just the barn frame. >> >> 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 > Different observers do not measure > different velocities between the same objects - at least not in > classical mechanics. I'm not saying they do. And in classical mechanics, simultaneity and length is NOT frame dependent. > And nor do they measure different distances - a > one meter separation between two objects according to one observer, is > the same one meter separation according to another. But we are not talking classical mechanics > 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? >> >> > And although you insist the length contraction is real, until you >> >> > indicate convincingly that you even know how to discern between >> >> > appearance and reality, I'm not going believe you when you simply >> >> > assert that the contraction is real. >> >> >> Then use 'frame independent' instead of 'real' .. as that is what you >> >> mean. >> >> >> And use 'frame depenendent' instead of 'apparent' .. as that is what >> >> you >> >> mean. >> >> >> If you are going to discuss physics, use the appropriate terms that >> >> have >> >> well defined meanings. >> >> > But I am still not clear about whether what is "frame dependent" is >> > real or not. >> >> Stop using words 'real' and 'apparent' .. it is not well defined and >> causes >> confusion > > It's no better defined that "frame dependent" and "-indepedent", in > relation to the questions I'm asking. Wrong >> > Received audio frequency is "frame dependent", >> >> Yes >> >> > but it's >> > not clear (rhetorically speaking) whether the change in frequency is a >> > change of the *source* frequency or not. >> >> No .. it is very clear. > > I know. But if we *didn't know* about the Doppler effect, and we took > our observations at face value, then it wouldn't be clear at all. But we do. > 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. >> > Let's return to what I said above in my previous post. Not only does >> > the suns rays, when directed through a magnifying glass, become >> > scorching, but the Sun also appears to shrink in size (at least if it >> > is in focus). Do we say "the sun has *really* shrunk", or do we say >> > "it merely appears to have shrunk"? And indeed, when we go to the >> > surface of the sun, we find the sun is just as big as it ever was. So >> > does it *really* shrink when you look through a lens, or does it >> > merely *apparently* shrink, with no mechanical contraction at all? >> >> The apparent difference in size due to differences in distance etc are >> illusions. Though what you are really measuring is an angle subtended at >> the eye, and THAT is a real difference. That real difference causes the >> 'illusion' when misinterpretted. > > Agreed, but all "illusions" are about misinterpretation. Pretty much >> >> > and if there is >> >> > a different amount of energy and momentum in the hammer, >> >> >> There is >> >> >> > a therefore >> >> > different amount of force applied to the skull, >> >> >> But there is also different momentum and energy in the skull >> >> > And let me guess. These "different" energies and momentums change in >> > perfect proportion, so that the *relative* energy between skull and >> > hammer is exactly the same? >> >> No. The difference in KE of the hammer before and after the strike is >> frame >> dependent. > > It can't possibly be. Wrong > The hammer cannot have spent more energy in one > frame than another of course it does .. it has different velocity > - 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
From: Inertial on 7 Apr 2010 00:09 "Sue..." <suzysewnshow(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 > "Relativity principle" > http://farside.ph.utexas.edu/teaching/em/lectures/node108.html Same old quote mining from Sue
From: Sue... on 7 Apr 2010 00:38
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 Would you care to elaborate how the speed of light could acquire the *apperance* indicated by the formula? Sue... > > > "Relativity principle" > >http://farside.ph.utexas.edu/teaching/em/lectures/node108.html > > Same old quote mining from Sue |