Known physics defeated by simple puzzle?
in [Physics]
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From: Raymond Yohros on 3 Apr 2010 22:30 On Apr 3, 6:11 pm, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > You may have noticed that the less I know > about a subject the more confidence I have, > and the more new light I throw on it. > yeah, i think that can be true in a topic like this one? r.y
From: Peter Webb on 3 Apr 2010 22:46 "Sue..." <suzysewnshow(a)yahoo.com.au> wrote in message news:ec501c21-c553-4da6-b4c9-4e08b74a9d13(a)y17g2000yqd.googlegroups.com... On Apr 3, 10:12 pm, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > "Sue..." <suzysewns...(a)yahoo.com.au> wrote in message > > news:0e0454c7-85ca-4783-b10d-2e5372612f9c(a)n34g2000yqb.googlegroups.com... > On Apr 3, 9:54 pm, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > wrote: > > ================== > > > > > Well, if you visit a particle accelerator, its pretty obvious that > > relativistic effects do occur. > > I believe a new record was set on 30 March 2010. > Would you happen to have the relativistic calculations > that show the energy? > > _________________________________ > No. But if you know the mass of the particle and its speed, I can work out > its energy in the frame of reference in which you measure the speed by > plugging it into a very simple formula. Is this what you need? proton mass = 1.67262158 � 10-27 kilograms relative speed 1.999999982 times the speed of light. ___________________________________ "Relative" speed, relative to what? It is simply impossible for one object in a laboratory to have a speed relative to another object of greater than c, so you have obviously screwed up. More to the point, how about giving the link to the original article. Particle accelerators are rated according to the energy that they add to a particle with unit charge (in all Particle accelerators that I am aware of this is essentially an invariant, ie in theory does not depend on the mass of the particle), I am sure the original link provides exactly the answer you are looking for. If you provide the link, I will show you where it states the energy of the particles or allows these to be very easily worked out.
From: Ste on 3 Apr 2010 23:39 On 4 Apr, 02:54, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > > I think I can finally be sure that you're someone who subscribes to > > the philosophy that "a tree does not make a sound if there is no one > > around to hear it", but that's not materialism, it's clearly an > > idealistic approach. > > No, I don't subscribe to that philosophy. I think you do, although it's possible that you don't realise it. > >> 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. > > > Indeed, but the important thing here is that the LADAR measurement is > > *invariant* under changes of velocity, and so we can clearly say that > > if the receiver changes relative velocity, it is *not* the source that > > has changed frequency. > > The frequency clearly does change depending on the frame in which you > measure it. This is observational fact. > > The frequency at rest is an invariant; the frequency observed in this frame > therefore does not change. No, I was talking about two different concepts: that of the "source frequency"; and that of the "received frequency". Which are you talking about when you refer to "the frequency"? > > Indeed, one can exceed the speed of sound > > completely, and therefore by your logic the source is no longer making > > a sound at all, > > No. I didn't state or imply that at all. You implied it, because by definition the microphone would clearly record silence (and your post is riddled will reasoning of this kind). And if the microphone records silence, then surely the measured frequency has dropped to 0Hz, and therefore the source is not making a sound at all? > > Ironically, I was expecting you to react harshly to my "spaceship on > > the monitor" question, but in the event you accepted that what appears > > on the monitor is not necessarily a representation of "real objects" > > with "real attributes", but is a cunning visual trick which merely > > makes it *appear* that a spaceship is in the sky. > > Glad I could answer your question to your complete satisfaction. Must be the first time! ;) > >> > 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? > > > The "frequency of the sound source" means "the frequency of > > oscillation at the source". The beauty with a sound source is that we > > can measure the oscillations (and hence, the "sound source frequency") > > with light instead of sound. > > > (And to hedge my bets for the umpteenth time, at relativistic speeds, > > even the LADAR method would fall down, because electromagnetic > > propagation delays would also start to become dominant. But the point > > of the argument is merely to illustrate that what is "apparent" is not > > the same as what is "real".) > > Huh? > > Are you saying that the frequency of a sound does not depend on the relative > motion of the emiter and receiver? No, I'm saying the frequency of the sound *source* does not depend on relative motion. > Try standing next to a train line and measure the frequency of the sound. > You will rapidly see that it *does* depend on relative motion; this is an > observed fact. But not if you measure the oscillation of the sound source with LADAR. > >> >> 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. > > > But we're not interested in what is received, because what is received > > is a product of more than one variable. What we are interested in is > > ascertaining the sound source frequency, and isolating it as an > > invariant. If we know that the sound source is invariant, then we know > > that the cause of the Doppler shifting is the propagation delay. > > No, you know the reason that the frequency is different is because the > frequency is a function of the relative speed. > > There *is* an invariant, which is the frequency measured in the rest frame > of the emitter. But it can be measured outside the rest frame, using LADAR. In any event, it is a tautology to say that a variable is invariant whenever the variable is invariant. The variable in this case is the relative velocity. You say that "if we measure the frequency from the rest frame, then the frequency is invariant". But this is true of every other frame, even moving ones. If you take a measurement in any frame, then that measurement is always invariant within that frame. > There *is* an invariant, which is the rate at which the clock ticks measured > in the reference frame of the emitter. As above. > > But if we *didn't* know that the sound source was invariant, then the > > apparent Doppler shifting > > Doppler shift is not "apparent". It is "real". The frequency really does > change depending on your speed relative to the emitter. The received frequency changes, yes. But the source frequency doesn't. > > it could just as easily be (the usual kind > > of) Doppler shifting, or it could easily be a change in the source > > frequency caused by some unknown mechanical interaction between the > > source and receiver that causes the source to change frequency when > > the receiver moves. > > You should Google "doppler shift" if you really don't know the cause of the > frequency change. Don't be foolish. > > Or to put it another way, imagine I am stood at the side of the road > > singing. You are approaching me in a car at a constant speed. You > > notice that on your approach, my voice has a certain tone. But as you > > pass, the tone drops. Now, did the tone of my voice "really" drop, > > The frequency depends on the frame in which you measure it. The received frequency does. The source frequency doesn't. And you didn't answer the question. How can you tell whether you were just going very fast, or whether I intentionally dropped the tone of my voice as you passed? > > But when I ask "does the length *really* contract?", I keep getting > > told either "yes", or I keep getting asked "what do you mean 'real'?". > > I don't know exactly what other people have told you. You post here often enough to see Peter. > > And when I speculate that, in SR, the time dilation and length > > contraction effects are a product of propagation delays (like they are > > with sound), I keep getting told "no, no, no, it is nothing to do with > > electromagnetic propagation delays". > > Its not. So you say. > >And indeed, some posters have > > even gone as far as saying that an 80 foot ladder would fit in a 40 > > foot barn with both doors closed (and again, they insist that it is > > not an optical illusion, it *really* would fit inside). > > It does. No Peter, it doesn't. > > So, I'm sure you can understand my confusion. > > Yes, you don't understand SR. Indeed, and I suspect it's because I'm asking people who themselves don't actually understand. > >> 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? > > > No, your *real* height is 178cms, and it is mechanically invariant. > > However your apparent height, measured visually (i.e. > > electromagnetically), can be manipulated in all sorts of ways. If I > > step back from you, you appear to shrink. If one of us lies down on > > the floor, you appear to shrink. If your image goes through a > > refracting lens, your apparent height can change in all sorts of ways. > > > Indeed, I recall hearing the other week that a handful of blind people > > who have been given rudimentary brain implants that give them sight > > for the first time, struggle at first because they are not accustomed > > to correcting for the "apparent" effects of perspective, as objects of > > fixed size appear to visually grow and shrink. > > Perhaps if you were to give a definition of "real" vs "apparent"? I've been giving you one since we began. And we agreed that, despite being able to see the spaceship on the monitor, it is not "real". So you accept that seeing and measuring is not necessarily believing. > >> >> >> 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? > > > It isn't different from sound, as far as I can tell. The point is that > > it's real length does not change at all, and hence the 80 foot ladder > > *never* fits in the barn with both doors *really* closed, although it > > can be made to *appear* to do so. > > Gee, again, your argument seems to hinge on what is "real" vs what is > "apparent"; you better define those terms or there is enormous scope for > misunderstanding. I've explained the barn paradox before, in terms of the doors not shutting simultaneously, so that one door re-opens before the other has even shut, and the ladder sails through in the normal way. However, an observer watching could be made to believe that the doors had shut simultaneously. You could actually perform a similar setup with speakers and microphones, where you have real doors, a real ladder, and the shutting of the doors is signalled by a countdown emitted by an audio speaker at each door. As measured by a microphone outside the barn, the doors will appear to shut simultaneously while the ladder is inside (and each speaker will count down in unison as measured at the microphone), but in fact the separation between the doors means that what appears to be simultaneous at the microphone, was in fact not simultaneous at all (as can be expediently proven by watching the doors instead of listening to the countdown).
From: Sue... on 4 Apr 2010 02:01 On Apr 4, 12:25 am, "Peter Webb" > >But this is true of > > every other frame, even moving ones. If you take a measurement in any > > frame, then that measurement is always invariant within that frame. ==================== > > But its not invariant across frames. > > In the reference frame of the train, the tone is *always* 100 Hz. > > In other reference frames, the frequency depends upon the relative motion.. That is clocks (plural) Write this on the back of your hand so you can tell when you have broken your experiment: << 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. My egg takes 3 min to boil flying north. Your egg takes 3 min to boil flying south. 2 eggs. 2 clocks. Sue...
From: Peter Webb on 4 Apr 2010 02:52
"Sue..." <suzysewnshow(a)yahoo.com.au> wrote in message news:af2773f5-640d-4e4b-a490-cc091d6d2912(a)z7g2000yqb.googlegroups.com... On Apr 4, 12:25 am, "Peter Webb" > >But this is true of > > every other frame, even moving ones. If you take a measurement in any > > frame, then that measurement is always invariant within that frame. ==================== > > But its not invariant across frames. > > In the reference frame of the train, the tone is *always* 100 Hz. > > In other reference frames, the frequency depends upon the relative motion. That is clocks (plural) Write this on the back of your hand so you can tell when you have broken your experiment: << 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. My egg takes 3 min to boil flying north. Your egg takes 3 min to boil flying south. 2 eggs. 2 clocks. Sue... __________________________________ You should see a doctor. You are babbling nonsense. |