Known physics defeated by simple puzzle?
in [Relativity]
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From: Inertial on 10 Apr 2010 02:40 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:33423b93-1593-4334-bcf6-14e113bcdeba(a)v20g2000yqv.googlegroups.com... > On 10 Apr, 07:11, "Inertial" <relativ...(a)rest.com> wrote: >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> news:da85279f-24ef-481b-93d0-287ce74db45d(a)y14g2000yqm.googlegroups.com... >> >> > On 10 Apr, 04:49, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> >> > wrote: >> >> > I do wish you'd stop framing the issue as "you're either with us or >> > against us". There is obviously some validity to SR - and I've said it >> > a million times. >> >> It cannot be only partly valid >> >> [...] >> >> > Incidentally, I >> > seem to remember that Terrell (of the "Terrell effect") commented that >> > a lot of scientists even in his time (i.e. 50 years after relativity >> > had been formulated) still had huge misconceptions about SR. And even >> > Newtonian mechanics has not been thrown out - merely reinterpreted to >> > show that it gives the correct answers only to certain circumstances >> > (which is not how it would have been interpreted in its heyday). >> >> It is approximately correct .. that is all. It is never completely >> correct >> except when there is no motion involved (which is rather pointless) > > Indeed, but the point is that Newtonian mechanics has "some > validity" (even if a mechanics without movement is useless in > practice). It is only valid in the degenerate case when it agrees with SR. Your pedantic arguments are noted, and just make you look foolish.
From: Inertial on 10 Apr 2010 02:41 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:597cffaa-f845-4f85-aa98-4a58f90f9789(a)x12g2000yqx.googlegroups.com... > On 10 Apr, 06:15, "Inertial" <relativ...(a)rest.com> wrote: >> "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote in message >> >> news:4bc0072f$0$5523$afc38c87(a)news.optusnet.com.au... >> >> >> >> >> >> >> >> > "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >news:e1d473d9-bd92-4373-ac6c-4ec08f157f25(a)z6g2000yqz.googlegroups.com... >> > On 10 Apr, 02:26, "Inertial" <relativ...(a)rest.com> wrote: >> >> >> > Incidentally, if you have two clocks a certain distance apart, >> >> > synchronised (obviously, accounting for propagation delays), >> >> >> Yes .. that is always assumed. >> >> >> > and >> >> > stationary relative to each other, >> >> >> Yes >> >> >> > what happens when you accelerate >> >> > them towards each other. Does the distant clock appear to slow down, >> >> > or speed up? >> >> >> Acceleration complicates things uncesssarily .. so lets assume no >> >> acceleration for simplicity. >> >> > Well, I asked the question precisely because I wanted an answer to >> > *that* scenario. If the clocks are already moving (and don't stop >> > before passing each other), then that really tells me nothing about >> > what I wanted to know. The purpose of having the clocks stopped at the >> > beginning and end is that it allows a 'simple' correction for any >> > propagation delay when testing for synchronisation. >> >> > _______________________________________________ >> > For SR, you can assume that the change in speed is instantaneous, eg >> > the >> > speed goes from V to 0 or -V in zero time. While physical objects can't >> > do >> > that, reference frames certainly can. Contrary to what I suspect you >> > believe, the "twin's paradox" is *not* caused by acceleration of the >> > travelling twin directly; it is caused by changes in the reference >> > frame >> > in which the elapsed time is measured, as any non-crank site on the >> > twins >> > paradox will explain. So you can assume that changes in velocity are >> > instantaneous. >> >> >> An equivalent set up is this, with no acceleration invovled, where A, >> >> B, >> >> A' >> >> and B' are all clocks. >> >> >> A'->v B'<-v >> >> A o B >> >> >> Let A and B be our mutually-at-rest, synchronized clocks (as you >> >> mentioned) >> >> >> Let A' and B' be moving at the same speed (but opposite directions) >> >> relative >> >> to A and B. >> >> >> As A' passes A and B' passes B (at the same time according to A and >> >> B), >> >> we >> >> copy the reading from A clock to A' clock, and copy the reading from B >> >> clock >> >> to B' clock. A' and B' keep moving and arrive together at o, where >> >> there >> >> times are compared. >> >> > As I say, I'd also like to discuss the specific scenario that I >> > raised. Because at least in my scenario, we can agree that they are >> > both synchronised at the start, and at the end, and that we have >> > accounted for propagation delays when testing for synchronisation. So >> > the question is how to interpret what happens in the middle, but >> > obviously I need you to describe what happens. >> >> > ____________________________________________ >> > As I understand your experiment, when the clocks are separating they >> > each >> > see the other clock as running more slowly, >> >> Ticking at the same rate, but see a later time. That is an illusion,of >> course >> >> > and when they are approach they see the other clock as ticking faster, >> >> There is some optical illusion of that, the actual measurement is slower. >> >> > and the percentage change is the same as that given by the formula for >> > the >> > Relativistic Doppler Shift. You can confirm that when you add the >> > outbound >> > and inbound changes together, they are both re-synchronised when they >> > meet >> > again, as a simple symmetry argument requires. >> >> Yeup > > So which part of this setup is *not* due to an "optical illusion"? I already explained and answered .. read. learn. Instead of playing pedantic games. If you have genuine questions, ask.
From: Peter Webb on 10 Apr 2010 02:44 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:da85279f-24ef-481b-93d0-287ce74db45d(a)y14g2000yqm.googlegroups.com... > On 10 Apr, 04:49, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > wrote: >> I have some sympathy for your problem. I have no sympathy for the fact >> that >> instead of trying to understand how the Universe actually works, your >> position is that SR is wrong and/or Inertial, PD and I am wrong because >> we >> agree with SR and SR is wrong. > > I do wish you'd stop framing the issue as "you're either with us or > against us". There is obviously some validity to SR - and I've said it > a million times. For us to argue about what explanation underlies SR, > or how to interpret it, is not to say SR is "wrong". But you do say SR is wrong, all the time, because you argue with its predictions. Lets see, for the record, whether you believe SR is wrong. Here are two specific predictions of SR. Tell me if you think they are correct: 1. Two twins - one travels to a start 1 light year away at 0.9c, turns around and returns at 0.9c. The travelling twin ages less than the stay at home because of relativistic time dilation. True of False? 2. 40 foot ladder moves into 20 foot barn at 0.9c. When the midpoint of the ladder is at the midpoint of the barn, the doors at each end are closed simultaneously (in the barn's frame of reference), a photo is taken, and the doors are quickly re-opened. The photo will show the ladder entirely within the barn. True or False? These are two quite specific predictions of SR. If you believe either of them is false, you don't believe SR is a true theory. So, do you or don't you believe these predictions of SR?
From: Ste on 10 Apr 2010 03:38 On 10 Apr, 07:38, "Inertial" <relativ...(a)rest.com> wrote: > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > > The point is simply to talk in qualitative > > terms about what happens to "simultaneity" between the points at the > > start and at the end at which we agree that the clocks are > > synchronised. > > It changes Will you quantify this change? > > So, whether it "appears" slow or is "really" slow, the question is > > does it slow down or speed up (whether really or apparently) > > Two different questions .. two different answers I didn't notice two questions, and I was the one who wrote it. > > depending > > on whether it is approaching or receding? In other words, if we moved > > the clocks in the opposite direction (starting near, and then receding > > to a point in the distance)? > > The clocks always tick at the correct rate .. they are neither fast nor slow > in their own frames. Yes, that went without saying. It's like saying a "clock is never slow relative to its own rate". > A frame moving relative to a clock will measure the clock as ticking slower. > Less elapsed time will show between an pair of events for the relatively > moving clock than an at-rest clock. That is independent of the direction of > the relative motion. > > I had though we agreed to ignore illusions due to propagation delays. Indeed, but when you started talking of the clocks "speeding up", that caused me confusion. > The illusion due to propagation delays is that a clock moving away from you > will look like it is running a bit slower, because it takes longer and > longer time for the light to reach you. > > The illusion due to propagation delays is that a clock moving toward you > will look like it is running a bit faster, because it takes short and > shorter time for the light to reach you. Indeed. But, I take it from your other statements above, correcting for these ilusions would leave a small remainder of slowing, based on the relative speed between the clocks? (and not based on the direction of relative movement?)
From: Ste on 10 Apr 2010 03:40
On 10 Apr, 07:44, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > news:da85279f-24ef-481b-93d0-287ce74db45d(a)y14g2000yqm.googlegroups.com... > > > On 10 Apr, 04:49, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > > wrote: > >> I have some sympathy for your problem. I have no sympathy for the fact > >> that > >> instead of trying to understand how the Universe actually works, your > >> position is that SR is wrong and/or Inertial, PD and I am wrong because > >> we > >> agree with SR and SR is wrong. > > > I do wish you'd stop framing the issue as "you're either with us or > > against us". There is obviously some validity to SR - and I've said it > > a million times. For us to argue about what explanation underlies SR, > > or how to interpret it, is not to say SR is "wrong". > > But you do say SR is wrong, all the time, because you argue with its > predictions. > > Lets see, for the record, whether you believe SR is wrong. > > Here are two specific predictions of SR. Tell me if you think they are > correct: > > 1. Two twins - one travels to a start 1 light year away at 0.9c, turns > around and returns at 0.9c. The travelling twin ages less than the stay at > home because of relativistic time dilation. True of False? True, because there is a "real" slowdown of the astronaut twin. > 2. 40 foot ladder moves into 20 foot barn at 0.9c. When the midpoint of the > ladder is at the midpoint of the barn, the doors at each end are closed > simultaneously (in the barn's frame of reference), a photo is taken, and the > doors are quickly re-opened. The photo will show the ladder entirely within > the barn. True or False? It is unclear how to interpret this prediction. |