Known physics defeated by simple puzzle?
in [Relativity]
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From: Peter Webb on 2 Apr 2010 23:11 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:a168cfa4-a989-4fd2-b361-993bcc6919d4(a)x12g2000yqx.googlegroups.com... > On 3 Apr, 01:27, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > wrote: >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> >> > Yes, but it involves no change in the frequency generated by the >> >> > source. >> >> >> The frequency of the sound depends entirely on the reference frame in >> >> which >> >> it is measured. >> >> > No, the *received* frequency of sound depends on the reference frame. >> >> How can you measure a frequency without receiving it? What is this >> supposed >> to mean? > > You could measure the emitted sound frequency, in this case, by using > an electromagnetic (i.e. something like LADAR) measurement of the > vibration of the source (and it is that vibration that we know to be > the generator of the sound). In this way, we measure the frequency of > the sound source, without receiving any sound. > Well, you aren't measuring the frequency of the sound, you are measuring the frequency with which an object vibrates. That will allow you to work out the frequency of the sound in the rest freame of the emitter, but so what? You could just as easily do this with a microphone and an oscilloscope next to the speaker, and measure the frequency directly. The same principle applies in SR, by the way. You can look at an atomic clock in some other reference frame and work out the rate at which it is ticking in its rest frame. If you are trying to develop an argument that there is some special reference frame for measuring frequency in which it is invariant, then you are completely correct. Exactly the same applies in SR; there is a reference frame for measuring length in which it is invariant, and that is the rest frame of the object. > > >> > As a human receiver, one can change the *apparent* frequency by >> > changing one's own circumstances (i.e. changing velocity relative to >> > the source), and this *apparent* change does not involve any change in >> > the generating mechanism of the source, and nor does it affect the >> > frequency received at any other receiver. >> >> No the change in frequency is real, not apparent. It doesn't just "sound >> like" a higher frequency, it rerally is a different frequency, as you can >> verify with a microphone and oscilliscope. > > I know Peter. The same applies to non-human receivers also, there was > really no significance to my use of the words "human receiver" except > to allow me to structure the sentence off-the-cuff in the way that I > did. > > > >> > At the nub of this is the fact that the audio source, if it is >> > oscillating at say 500Hz a second, continues to do so *no matter what* >> > its relative velocity (at least if we disregard relativistic effects >> > at high velocities for now, for the simplicity of the argument which >> > applies nevertheless). >> >> Yes. >> >> Similarly, an atomic clock travelling at 0.9c continues to tick at >> exactly >> the same rate in its own inertial frame of reference. > > Lol. No no no. The sound source continues to oscillate at 500Hz > according to *all* observers, no matter what speed they are travelling > at. (For the sake of this argument, we are confining possible speeds > to within the speed of sound). "Sound source" ? Do you by that mean the frequency of the sound measured by an observer stationary with respect to the train? If so, the same applies in SR. If "sound source" does not mean that, what does it mean? > > > >> >> Changing the relative speed of the train definitely changes the >> >> frequency >> >> of >> >> the sound. >> >> >> You can easily verify this yourself. >> >> > You clearly still don't understand the significance of my argument, >> > which is that the *apparent* frequency, as measured by a receiver, can >> > be affected by the receiver's *own* circumstances, as much as by an >> > actual change of frequency at the source. >> >> That is correct, except that the effect is not just "apparent", it is >> real, >> as can be easily verified by measuring it. >> >> A tone which is emitted in a moving trains reference frame at 100 Hz >> might >> be measured in a stationary frame as being 120 Hz. This is as real as a >> tone >> of 120 Hz directly emitted from a stationary train. There is not test >> which >> can tell them about; none. > > You mean except a test that measures the oscillation of the sound > source with light instead of sound? You lack imagination Peter. > No. I mean a test of the frequency of the sound that is received. > > >> > It is significant, to any >> > scientific investigation or understanding, to establish what the >> > *cause* is of the change of received frequency. >> >> Relative motion. We all know that already. > > Yes, but with sound it's easy to understand (in common sense > mechanical terms) *why* relative motion causes Doppler shifting, and > it's also clear (at least to me) that the effect is apparent, and does > not involve a change in the frequency of the source. Its not just "apparent", its also real. As I keep saying - and is easily verified - the frequency of the sound really does change. You can measure the frequency using an oscilloscope and easily verify this for yourself. Of course, the change in frequency is a function of the frame in which you measure it. Just like in SR. > The problem with > SR is I keep getting told that there *is* an actual change at the > source. > I don't know what other people have told you, and I would be saddened if anybosy used these exact words, as they are so vague as to be meaningless. What you *should* have been told is that: 1. Length is a relative concept, as it depends upon the frame of reference in which it is measured. 2. Frequency is a relative concept, as it depends on the frame of reference in which it is measured. > > >> >> >> > My question with SR remains the same: is it >> >> >> > "real", or is it an apparent effect. >> >> >> >> Like the Doppler shift, it is both real and apparent. >> >> >> >> As I said already. >> >> >> > It is not "real" in the sense that it involves a change in the >> >> > attributes of the source - it is "apparent" in the sense it involves >> >> > a >> >> > change in the relationship between the source and receiver. >> >> >> That is not what "apparent" vs "real" means, at least in common usage. >> >> > I concede in this particular analogy that the words are not entirely >> > apt, but it is really a sideshow to the real question about "length >> > contraction", where I think it's perfectly reasonable to ask "is the >> > contraction real, or merely apparent". But if you prefer, I can phrase >> > it as "is the contraction mechanical, or visual". >> >> Mechanical. It does not depend on visually observing objects. The twin >> who >> stays at home ages faster; its not some optical illusion they have >> wrinkles >> when the travelling twin does not. Every day SR is tested in particle >> accelerators; AFAIK none of these depend upon "seeing" a particle being >> emitted and "seeing" it smash into a target and then measuring the >> difference in time of visual observations. They use mechanical >> processes - >> eg interactions with physical matter - to measure times. > > Yes, but I'm still not sure this is true, not least because you either > don't understand what I mean by the difference between "real" and > "apparent", or at any rate you don't see the significance of the > question. > Correct. I don't understand what you mean by "real" and "apparent". My "apparent" height - as measured at rest with a tape measure - is 178 cms. What is my "real" height? How is it different? > > >> >> The frequency of a sound generated by a moving train definitely does >> >> really >> >> change as its speed changes. Measure it for yourself if you don't >> >> believe >> >> it. >> >> > The frequency generated doesn't change - an observer onboard could >> > attest to that. >> >> The frequency in an inertial frame is constant. Same as lengths and times >> in >> SR. >> >> > It is the frequency *received* that changes, depending >> > on the circumstances of the observer. >> >> Yes. Frequency depends on the frame of reference in which it is measured. > > No, the *received* frequency depends on the relative velocity. The > *source* frequency doesn't. The length of an object in SR in its rest frame doesn't vary either. The length in other frames does. How is this different to the frequency of a sound?
From: Sue... on 2 Apr 2010 23:11 On Apr 2, 10:31 pm, Ste <ste_ro...(a)hotmail.com> wrote: [...] _______________________________ > > > I would ask whether you are referring to the color as seen through a filter > > or not seen through a filter. Your question is ambiguous. > ================== > <rolls eyes> Then let me ask you another question. Look around you > now. Do you see a lot of men in white coats? Here is a clue. Peter_Webb doesn't want to take credit for moving mile-markers to save to reduce fuel consumption in his community so there is some glimmer of intelligence. Possibly enough intelligence to realise he has painted himself into a corner by conflating LET with Einstein's relativity. Since he is resorting to obfuscation and debating tactics, your time is a small price to pay to save face by mudding the water. If you are having fun, enjoy the game. But don't confuse it with a discussion about physics. Sue... > > Or perhaps let me adapt the original question further. You are looking > at the sky on a television monitor, by way of a camera pointed at the > sky. I then use special effects to add a UFO to the video feed to the > monitor, so that it appears to be in the sky. Now, is the UFO really > in the sky, or is it merely apparent?
From: Peter Webb on 2 Apr 2010 23:12 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:b491f63f-ca40-44ee-80f9-48771bb4a437(a)10g2000yqq.googlegroups.com... > On 3 Apr, 01:34, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > wrote: >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> news:1731685b-72c2-42d2-8f33-ca477d13affc(a)5g2000yqj.googlegroups.com... >> On 2 Apr, 16:05, "Inertial" <relativ...(a)rest.com> wrote: >> >> >> >> >> >> > "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> >news:aa6d8cc5-8343-40fb-b960-2693aa6ff4d0(a)z4g2000yqa.googlegroups.com... >> >> > > On 2 Apr, 02:02, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> >> > > wrote: >> > >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> > >> >> > And just to move to an easier analogy, I don't care how much >> > >> >> > you >> > >> >> > can >> > >> >> > accurately quantify something like acoustic Doppler shifting >> > >> >> > with >> > >> >> > an >> > >> >> > equation, my question would be this: is the Doppler shift a >> > >> >> > product >> > >> >> > of >> > >> >> > the change of interaction between source and receiver, or is >> > >> >> > the >> > >> >> > source "really" changing frequency by some unknown mechanism? >> > >> >> > The >> > >> >> > answer, of course, is that the Doppler effect is apparent - >> > >> >> > there >> > >> >> > is >> > >> >> > nothing inherent about the source that needs to change in order >> > >> >> > to >> > >> >> > explain the phenomenon. >> >> > >> >> The Doppler shift is real. Frequencies really do change. >> >> > >> > Yes, but it involves no change in the frequency generated by the >> > >> > source. >> >> > >> The frequency of the sound depends entirely on the reference frame >> > >> in >> > >> which >> > >> it is measured. >> >> > > No, the *received* frequency of sound depends on the reference frame. >> > > As a human receiver, one can change the *apparent* frequency by >> > > changing one's own circumstances (i.e. changing velocity relative to >> > > the source), and this *apparent* change does not involve any change >> > > in >> > > the generating mechanism of the source, and nor does it affect the >> > > frequency received at any other receiver. >> >> > > At the nub of this is the fact that the audio source, if it is >> > > oscillating at say 500Hz a second, continues to do so *no matter >> > > what* >> > > its relative velocity (at least if we disregard relativistic effects >> > > at high velocities for now, for the simplicity of the argument which >> > > applies nevertheless). >> >> > >> Changing the relative speed of the train definitely changes the >> > >> frequency >> > >> of >> > >> the sound. >> >> > >> You can easily verify this yourself. >> >> > > You clearly still don't understand the significance of my argument, >> > > which is that the *apparent* frequency, as measured by a receiver, >> > > can >> > > be affected by the receiver's *own* circumstances, as much as by an >> > > actual change of frequency at the source. It is significant, to any >> > > scientific investigation or understanding, to establish what the >> > > *cause* is of the change of received frequency. >> >> > >> >> > My question with SR remains the same: is it >> > >> >> > "real", or is it an apparent effect. >> >> > >> >> Like the Doppler shift, it is both real and apparent. >> >> > >> >> As I said already. >> >> > >> > It is not "real" in the sense that it involves a change in the >> > >> > attributes of the source - it is "apparent" in the sense it >> > >> > involves >> > >> > a >> > >> > change in the relationship between the source and receiver. >> >> > >> That is not what "apparent" vs "real" means, at least in common >> > >> usage. >> >> > > I concede in this particular analogy that the words are not entirely >> > > apt, but it is really a sideshow to the real question about "length >> > > contraction", where I think it's perfectly reasonable to ask "is the >> > > contraction real, or merely apparent". But if you prefer, I can >> > > phrase >> > > it as "is the contraction mechanical, or visual". >> >> > >> The frequency of a sound generated by a moving train definitely does >> > >> really >> > >> change as its speed changes. Measure it for yourself if you don't >> > >> believe >> > >> it. >> >> > > The frequency generated doesn't change - an observer onboard could >> > > attest to that. It is the frequency *received* that changes, >> > > depending >> > > on the circumstances of the observer. >> >> > >> Of course, the frequency that you measure is a function of the >> > >> reference >> > >> frame in which you measure it. In this respect, the "frequency" of a >> > >> sound >> > >> is not a precisely defined concept. The normal use is that the >> > >> frequency >> > >> is >> > >> tacitly assumed to be that which is measured at rest. Same as length >> > >> in >> > >> SR. >> > >> When you want to compare frequencies in two different reference >> > >> frames, >> > >> this >> > >> definition breaks down as there are two different possible base >> > >> frames >> > >> for >> > >> measurement, and you have to be specific about which reference frame >> > >> you >> > >> are >> > >> measuring frequency in. Same, again, as for length in SR. >> >> > > You know, I could explain this same point to a child by saying "the >> > > frequency measured depends upon your speed relative the source". >> >> > It is not just 'apparent'. The frequency REALLY IS DIFFERENT for each >> > observer. >> >> Then consider another example. I give three people a photographic >> filter each, all different colours, and they hold it front of their >> eyes. I ask them to look at the sky, and they each comment that the >> sky has changed colour. I now ask them "has the sky really changed >> colour?". Now how would you interpret my question, and how would you >> answer that question? >> >> _____________________________________ >> >> I would ask whether you are referring to the color as seen through a >> filter >> or not seen through a filter. Your question is ambiguous. > > <rolls eyes> Then let me ask you another question. Look around you > now. Do you see a lot of men in white coats? > > Or perhaps let me adapt the original question further. You are looking > at the sky on a television monitor, by way of a camera pointed at the > sky. I then use special effects to add a UFO to the video feed to the > monitor, so that it appears to be in the sky. Now, is the UFO really > in the sky, or is it merely apparent? Apparent.
From: Peter Webb on 2 Apr 2010 23:30 "Sue..." <suzysewnshow(a)yahoo.com.au> wrote in message news:877fa310-17d8-4dd9-a09e-8bbd283c9b0e(a)n34g2000yqb.googlegroups.com... On Apr 2, 10:31 pm, Ste <ste_ro...(a)hotmail.com> wrote: [...] _______________________________ > > > I would ask whether you are referring to the color as seen through a > > filter > > or not seen through a filter. Your question is ambiguous. > ================== > <rolls eyes> Then let me ask you another question. Look around you > now. Do you see a lot of men in white coats? Here is a clue. Peter_Webb doesn't want to take credit for moving mile-markers to save to reduce fuel consumption in his community so there is some glimmer of intelligence. ____________________________ Because I never talked about it at all, as I keep saying you are confusing me with some other poster (quite possibly yourself; you are the only person I have noticed talking about it). Possibly enough intelligence to realise he has painted himself into a corner by conflating LET with Einstein's relativity. ___________________________ Again, that must have been somebody else. If you think it was me, you should dig up the quote from me. I am happy to defend what *I* say in this newsgroup, but I cannot be held responsible for things I didn't say. Since he is resorting to obfuscation and debating tactics, your time is a small price to pay to save face by mudding the water. If you are having fun, enjoy the game. But don't confuse it with a discussion about physics. Sue... _____________________________ I take it you have no more questions regarding SR?
From: Sue... on 2 Apr 2010 23:43
On Apr 2, 11:30 pm, "Peter Webb" > Again, that must have been somebody else. If you think it was me, you should > dig up the quote from me. I am happy to defend what *I* say in this > newsgroup, but I cannot be held responsible for things I didn't say. We will entertain the possibly that someone else is smart enough to know the difference in moving a grocer and moving mile-markers on the road to the grocer but the difference escapes you. That is consistent with your misrepresentation of Einstein's relativity. << Einstein's relativity principle states that: All inertial frames are totally equivalent for the performance of all physical experiments. In other words, it is impossible to perform a physical experiment which differentiates in any fundamental sense between different inertial frames. By definition, Newton's laws of motion take the same form in all inertial frames. Einstein generalized[1] this result in his special theory of relativity by asserting that all laws of physics take the same form in all inertial frames. >> http://farside.ph.utexas.edu/teaching/em/lectures/node108.html [1]<< the four-dimensional space-time continuum of the theory of relativity, in its most essential formal properties, shows a pronounced relationship to the three-dimensional continuum of Euclidean geometrical space. In order to give due prominence to this relationship, however, we must replace the usual time co-ordinate t by an imaginary magnitude sqrt(-1) ct proportional to it. Under these conditions, the natural laws satisfying the demands of the (special) theory of relativity assume mathematical forms, in which the time co-ordinate plays exactly the same rôle as the three space co-ordinates. >> http://www.bartleby.com/173/17.html << where epsilon_0 and mu_0 are physical constants which can be evaluated by performing two simple experiments which involve measuring the force of attraction between two fixed charges and two fixed parallel current carrying wires. According to the relativity principle, these experiments must yield the same values for epsilon_0 and mu_0 in all inertial frames. Thus, the speed of light must be the same in all inertial frames. >> http://farside.ph.utexas.edu/teaching/em/lectures/node108.html Sue... |