Known physics defeated by simple puzzle?
in [Relativity]
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From: Ste on 2 Apr 2010 13:51 On 2 Apr, 16:12, "Sue..." <suzysewns...(a)yahoo.com.au> wrote: > On Apr 2, 10:34 am, "Peter Webb" > > > > > > <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > > "Sue..." <suzysewns...(a)yahoo.com.au> wrote in message > > >news:1a248a27-5cb8-46ea-b22a-76ab5e6b87c6(a)h27g2000yqm.googlegroups.com.... > > On Apr 2, 2:24 am, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > > wrote: > > > > t. >>http://www.bartleby.com/173/13.html > > > > > So it seems your favourite ~tests~ of > > > > Special Relativity actually predate Einstein's > > > > writing on the subject. > > > > > ______________________________________ > > > > Sure. And the observation that apples fall to the ground predates > > > > Newton's > > > > law of gravity. > > > > > I note the rest of your post asks why Einstein said some particular > > > > thing. > > > > > While I feel I know SR and the Universal Law of Gravity quite well, I > > > > don't > > > > the history behind the theories well, much less the motivation behind > > > > why > > > > the people who contributed to their development said the many various > > > > things > > > > they did through the course of their lives. I am a physicist, not a > > > > historian or psychologist. You can quote all the bits of Newton or > > > > Einstein > > > > writings you like, and ask me why they said those things, and the answer > > > > will be the same - I don't know. I simply don't know the history behind > > > > these, any more than I know the history behind the solution of a > > > > quadratic > > > > equation, or why the person who first solved the quadratic did so. These > > > > are > > > > questions of history and psychology, not questions about science or > > > > maths. > > > > > Of course, if you have any questions concerning the scientific aspects > > > > of > > > > SR > > > > or the Universal Law of Gravity, feel free to ask. But for historical > > > > information about SR and Newton's law of gravity, I'm not the person to > > > > ask. > > > > In the below post you are arguing against Einstein's > > > relativity and in favour of Lorentz ether theory on > > > a point that distinguishes them. > > > >http://groups.google.com/group/sci.physics.relativity/msg/603a9f54c1e.... > > > > ___________________________________ > > > > No, I'm not, you clearly don't understand what I said. Perhaps if you were > > > to quote the bit that you think is me arguing in favour of Lorentz over > > > SR, > > > I could clear up your misunderstanding of my remarks? As it is, I have > > > absolutely no idea how you could possibly have gained that impression.. > > "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > > > "It shouldn't have. The contraction is both real > > and apparent. Things really do get shorter, clocks > > run slower, the travelling twin does return younger > > and the 40 foot pole really does fit in the 20 foot > > barn. " > > > That is the prediciton of Lorentz ether theory.http://en.wikipedia.org/wiki/Lorentz_ether_theory > > > ______________________________ > > But it is not an argument against SR (as you claimed) in any way, shape or > > from. The predictions that apples fall to the ground is similarly consistent > > with lots of other possible laws of gravity (eg laws with force that varies > > with 1/r rather than 1/r^2), but the observation that apples fall tothe > > ground is *not* an argument for a force that varies with 1/r over one with a > > force that varies as 1/r^2. > > > Contrast with Einstin's statement: > > << 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 > > > _____________________________________ > > How is this possibly in conflict with what I said, and how could what I said > > possibly be an argument against SR when what I said above is exactly what is > > predicted by SR? > > It seems you make no distinction between > > A) Moving the grocer closer to your house > > and > > B) Moving the mile-posts on the road to the grocer. > > So if stil need further explanation I fear you will > need to consult with Alice and the Red Queen. Or Humpty Dumpty perhaps!
From: Ste on 2 Apr 2010 13:56 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?
From: Sue... on 2 Apr 2010 15:42 On Apr 2, 10:45 am, Ste <ste_ro...(a)hotmail.com> wrote: [...] ================ > > You know, I could explain this same point to a child by saying "the > frequency measured depends upon your speed relative the source". That would be a smart child, indeed. Consider an aeroplane moving at a significant fraction of light-speed wrt low pressure air. When its skin is illuminated by a radar beam, the interacting electrons are boosted closer to the speed of light in the air's frame of reference. That is a situation the electrons and their neighbors will resist and become measureably non-linear in their response to the illumination. <<The Doppler effect has in fact been tested at speeds high enough to distinguish between these two [sound and light] formulas. The possibility of such a test, based on observing the Doppler shift for canal rays emitted from high-speed ions, had been considered by Stark in 1906, and Einstein published a short paper in 1907 deriving the relativistic prediction for such an experiment. However, it wasnt until 1938 that the experiment was actually performed with enough precision to discern the second order effect. >> Doppler Shift for Sound and Light http://www.mathpages.com/rr/s2-04/2-04.htm ~Cherenkov radiation~ http://farside.ph.utexas.edu/teaching/em/lectures/node50.html http://en.wikipedia.org/wiki/Larmor_formula Sue...
From: Peter Webb on 2 Apr 2010 20:27 "Ste" <ste_rose0(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. How can you measure a frequency without receiving it? What is this supposed to mean? > 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. You correctly point out that somebody in some other intertial reference frame (eg the reference frame of the emitter of the sound) would hear a different frequency. That is because the frequency of the sound depends upon the reference frame of the observer. > 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. > > >> 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. They are identical in all respects; if one is "real", both are "real". > 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. > > > >> >> > 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. > > >> 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. Same as length and time in SR. > > >> 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". And yet, you cannot understand exactly the same point when applied to SR.
From: Peter Webb on 2 Apr 2010 20:34
"Ste" <ste_rose0(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. |