Known physics defeated by simple puzzle?
in [Relativity]
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From: Ste on 7 Apr 2010 23:32 On 8 Apr, 02:41, PD <thedraperfam...(a)gmail.com> wrote: > On Apr 7, 8:21 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > On 7 Apr, 22:45, PD <thedraperfam...(a)gmail.com> wrote: > > > > But it does. Closing velocity is also frame dependent. > > > Suppose you have objects A and B, and you have observers Jack (at rest > > > relative to A), Larry (at rest relative to B), Mary (moving relative > > > to both A and B such that A and B have equal speeds relative to Mary), > > > and Nancy (moving relative to A, B, and Mary). > > > I must admit I've no clear picture at all about this scenario. > > Try making a sketch. No, what I meant was that there isn't sufficient information for me to confidently build a mental sketch. You don't describe how anything is moving relative to anything else, or where anything is positioned relative to anything else. And there are six (linguistic) objects in total positioned and moving in non-specified ways, and also it is not clear whether the observers should participate as real objects, or merely oversee as God-observers. Of course, I could make assumptions about these things, but if it comes to a disagreement, I don't want to be arguing over a scenario of which there is no shared comprehension. > > > Then what will be true > > > is that the closing speeds between A and B will have the same answers > > > for Jack and Larry, but that number will be different than the closing > > > speed between A and B according to Mary, and all of those different > > > than the one according to Nancy. > > > No, I reject this. The closing speed between A and B is universal, no > > matter how the observers move around relative to A and/or B. > > I don't care whether you reject it or not. It is experimentally the > case, according to measurements. By what right do you say that > something is true, despite being counter to measurements? We're back > to unconfirmable solipsism if you so insist. The accusation is that the observations are being misinterpreted, not that I'm simply pretending the observations don't exist.
From: paparios on 7 Apr 2010 23:32 On 7 abr, 23:05, Ste <ste_ro...(a)hotmail.com> wrote: > On 8 Apr, 00:13, "papar...(a)gmail.com" <papar...(a)gmail.com> wrote: > > > On 7 abr, 17:39, Ste <ste_ro...(a)hotmail.com> wrote: > > > > Like I said, the equations of audio Doppler predict that the received > > > frequency will change depending on your velocity to the source. But it > > > does not *explain* why this happens, and nor does it state whether the > > > source frequency changes or not. All it describes is what you will > > > observe, without *any* physical explanation at all. One must look > > > *beyond* the mere maths of audio Doppler, in order to *physically > > > explain* the effect. > > > On the contrary, the mathematical model on that case does explain what > > IT IS OBSERVED IN NATURE. > > But maths tells us nothing about what is real. It simply quantifies > observations - it does not explain them. > And that is precisely what a scientist is looking for, that is, a mathematical model which is good enough to make predictions which closely corresponds with observations...period. > > You don't ask why the Earth, together with > > the rest of the planets, move in a determined direction and not in the > > opposite direction. > > I don't see why I wouldn't ask that. > Because that answer is, for all practical purposes within our solar system, quite irrelevant. Miguel Rios
From: Ste on 7 Apr 2010 23:40 On 8 Apr, 02:46, "Inertial" <relativ...(a)rest.com> wrote: > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > >> > But you still don't get it. "Fitting" is not a relationship between > >> > obsever and ladder. It is a relationship between ladder and barn. Why > >> > on Earth would the observer's presence and circumstances affect the > >> > fitting of these two objects, that are totally independent of the > >> > observer? > > >> To help you understand this, I'd like for you to give me a very > >> precise definition of what you mean when you say that one object A > >> will "fit" inside object B, when A and B are relatively moving. > >> Depending on the quality of your definition, I may probe it with some > >> additional questions and scenarios to see if it works. > > > It's relatively straightforward. "Fitting" is when the ladder is of > > such length > > which is a frame-dependent notion > > > that it would be possible to close both doors on the barn, > > implicitly simultaneously, which is a frame-dependent notion > > > and for the ladder to be contained completely inside. > > So it is a frame dependent notion. Yet you insist it be absolute and > invariant. Sorry, but you cannot impose your will on nature or physics.. But I do have a right to specify how my own hypothetical experiments will be carried out. And in particular, I have a right to determine that my own definition of simultaneity will be used, and what is simultaneous according to my definition may not be what you consider simultaneous. > >> > > > but that's not materialism - it's going > >> > > > back to saying that the tree falling in the forest only makes a > >> > > > sound > >> > > > if an observer heard it. > > >> > > Nonsense. You are the one who above pointed out the with the object > >> > > moving > >> > > at 50km/hr and 100km/hr you have to consider the objects you are > >> > > measureing > >> > > relative to (ie the frame of reference). > > >> > Yes. But you only have to reference two objects to describe a closing > >> > speed. You don't say "objects A and B were closing at 100kmh according > >> > to Jack" and "objects A and B were closing at 50kmh according to > >> > Jill", because that would be contradictory (assuming that the > >> > definition of "kmh" is itself common between Jack and Jill). > > >> > You could say "objects A and B were closing at 100kmh according to > >> > Jack" and "objects A and B were closing at 100kmh according to Jill", > >> > but since the observer has no bearing on the measurement, why > >> > reference him at all? > > >> But it does. Closing velocity is also frame dependent. > >> Suppose you have objects A and B, and you have observers Jack (at rest > >> relative to A), Larry (at rest relative to B), Mary (moving relative > >> to both A and B such that A and B have equal speeds relative to Mary), > >> and Nancy (moving relative to A, B, and Mary). > > > I must admit I've no clear picture at all about this scenario. > > Its not that hard. Here's a more concrete example. Two relatively moving > spaceships A and B. Jack is in one of them, Larry in the other, and Mary is > in a space station half way between them. Nancy is in another rocket ship > moving relative to all of them. So we'll just say there are four observers, each occupying real spaceships. Let's just call them A, B, C, and D. We have A, B, and C, on a common axis, in that order. A is travelling to the left of B. C is travelling to the right of B. A and C are travelling away from B at the same speeds (hence the speed between A and C is twice what is is between A and B). D we can have travelling perpendicular to the axis at B's location, again at the same speed as between A and B. Is that agreed?
From: Ste on 7 Apr 2010 23:43 On 8 Apr, 02:47, PD <thedraperfam...(a)gmail.com> wrote: > On Apr 7, 8:40 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > I doubt that after writing "It cannot fit and not fit at the same > > > > > time" you really understand this gedanken at all. > > > > > It depends what you mean by "understand". If you mean "have grasped > > > > its tenets, and can reason the conclusion from those tenets", then I > > > > understand it totally. If you mean "accept that length contraction > > > > really occurs", then the answer is no. And I suspect at this point the > > > > real problem is not my lack of understanding of the paradox, but your > > > > lack of understanding of what I mean by "real". > > > > Real is what can be verified by a measurement. > > > No it isn't. This is a fundamental difference between us. I dare say > > there are lots of things that cannot be verified by measurement, but > > only by inference from other measurements. > > Not that are of scientific interest, no. It certainly *ought* to be of scientific interest. > > > If you believe that reality has certain traits but that those traits > > > are unverifiable through measurement, because the measurement is > > > always obscured, then one has to ask on what basis you would believe > > > reality has those traits in the first place. > > > Indeed, you would have to ask that. > > Yes, and appropriately so. I notice you snipped the next line, which I > here repeat: > =============================== > If you then say, "Because > it makes sense to me that it would," then you have simply slipped into > subjective solipsism that is divorced from scientific investigation. > =============================== > And so there we are. Yes. I was simply saying that you are entitled to ask on what basis I hold that reality has certain traits, and I must be willing to explain why I hold that. This we agree on, surely?
From: Sue... on 7 Apr 2010 23:50
On Apr 7, 11:09 pm, "Inertial" <relativ...(a)rest.com> wrote: > "Sue..." <suzysewns...(a)yahoo.com.au> wrote in message > > news:541c6f6d-a61d-4ea7-bf46-0c8e404289ec(a)11g2000yqr.googlegroups.com... > > > > > On Apr 7, 5:24 pm, Ste <ste_ro...(a)hotmail.com> wrote: > >> On 7 Apr, 15:49, "Inertial" <relativ...(a)rest.com> wrote: > > >> > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > >> >news:cf5cd01b-0da3-41b0-88b5-69b2e678a011(a)z7g2000yqb.googlegroups.com.... > > >> > > On 7 Apr, 05:08, "Inertial" <relativ...(a)rest.com> wrote: > >> > >> "Ste" <ste_ro...(a)hotmail.com> wrote in message > > >> > >> >> > Again, hidden in the meaning here is 100km/h > >> > >> >> > *relative to what*. An object cannot travel at *both* 100km/h > >> > >> >> > *and* > >> > >> >> > 50 > >> > >> >> > km/hr *relative to me*. > > >> > >> >> I didn't say it could. But we are talking about things being > >> > >> >> real.. > >> > >> >> you > >> > >> >> claim that all observers have to agree about the value for it to > >> > >> >> be > >> > >> >> real. > > >> > >> > Yes, I do say that! > > >> > >> So velocity is not real, momentum is not real, kinetic energy is not > >> > >> real, > >> > >> length is not real, time is not real etc etc. > > >> > >> Is that REALLY what you want to be saying? > > >> > > But I'm not saying that, am I? > > >> > By implication, yes, you are > > >> > > You're the one putting these words in > >> > > my mouth. > > >> > No .. I am applying your definition. > > >> > If that is NOT what you want to be saying, then you should change yoru > >> > definition > > >> No Inertial, you're not applying my definition, because you don't even > >> understand my definition. > > > We can't use your definition because Einstein's > > definition puts the ballistic light that > > W. deSitter never found on an imaginary axis. > > Umm .. no. There's no ballistic light required for SR. Only the time > between light being emitted at the source and arriving at its destination > gives a speed of c for all inertial reference frames. How it gets there is > not really a matter for SR .. it is propagation method agnostic. That is what I meant that you don't need SR except to remove Newton's Coupuscles. It is in the narrative. Theorem of the Addition of Velocities If he had not suggested source dependent light speed in the narrative, the trick with stipulations and definitions and simultaniety would be unnecessary. I think you will find the modern Fitzpatrick text gets by just fine without all that. > > OMG> Sue makes a quote that is actually on topic.... > > > <<There is only one demand to be made of the > > definition of simultaneity, namely, that in > > every real case it must supply us with an > > empirical decision as to whether or not the > > conception that has to be defined is fulfilled. > > That my definition satisfies this demand is > > indisputable. That light requires the same time > > to traverse the path A �> M as for the path B �> M > > is in reality neither a supposition nor a hypothesis > > about the physical nature of light, but a stipulation > > which I can make of my own freewill in order > > to arrive at a definition of simultaneity.�>> > >http://www.bartleby.com/173/8.html > > Of course, to be useful, such a 'stipulation' for simultaneity needs to be > consistent, reflexive etc. It is just for the corpuscle fans. > > Also note that the equal time required is indeed a direct consequence of the > second postulate. That correctly synchronized clocks show those equal times > as equal is almost self-evident. I think it may only be a good approximation. The below feels a bit like curve-fitting. A maths major could probably spot it if if is. ;-) <<According to the Galilean transformation, the *apparent* speed of propagation in S' is c-v, which violates the relativity principle. Can we construct a new transformation which makes the velocity of [ballistic] light invariant between different inertial frames,>> http://farside.ph.utexas.edu/teaching/em/lectures/node109.html Anyway, It is good enough to constuct a space-time and unnecessary to resolve the two postulates because ballistic light is not real. > > > The ballistic light only *appears* for people > > of his time that applied Newtons mechanics to > > light particles. > > >http://en.wikipedia.org/wiki/Emitter_theory > > > In the formal statement the ballistic > > property vanishes. > > >http://www.bartleby.com/173/17.html > > There was (and is) no need for ballistic light in SR. You seem confused > that it ever did. Blame Einstein, not me. "Theorem of the Addition of Velocities" http://www.bartleby.com/173/13.html Modern version is much easier. < 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... |