Is Length Contraction in SR physical??
in [Relativity]
|
Prev: Simultaneous events and Einstein's absolute time
Next: New Theory --- The Theory of Quantum Wave Sources
From: kenseto on 5 Feb 2010 17:12 On Feb 5, 10:44 am, "papar...(a)gmail.com" <papar...(a)gmail.com> wrote: > On 5 feb, 01:29, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > On 5 Feb, 02:37, "papar...(a)gmail.com" <papar...(a)gmail.com> wrote: > > > > In the "real world" there are some that say that the source of the Big > > > Bang could bechosen as an absolute reference, but it is the same case > > > of you aboard the space ship, that is we don't know if the Big Bang > > > was sitting still or moving with respect to something else. At the end > > > it does not matter at all!!! An absolute frame of reference is not > > > needed nor an abosulte time is needed. > > > It doesn't matter mathematically, but it does matter physically. > > > As I've said, if an absolute reference frame can be discerned that > > would allow us to discern the movement of the universe itself, then > > good. Otherwise, the absolute reference frame can simply encompass the > > whole universe (which rules out any question of what the big bang - > > and the universe - is moving relative to). > > What it is known is that no absolutes are needed, in order to predict > what the results will be on a given physical experiment. Take GPS, for > instance, where clock corrections on satellites, one based on SR and > the other based on GR, are enough to ensure the necessary precision of > the satellites clocks, by which the entire GPS system can perform as > predicted. Those corrections do not need or care of some absolute > reference frame located somewhere, far in the deep universe. Local > frames of reference do quite well and work like a charm. The GPS uses absolute time to synch the satellite clock with the ground clock as follows: The GPS second is redefined to have 4.15 more periods of cs 133 radiation than the ground clock second. This redefinition of the GPS second is designed to make the GPS second contain the same amount of absolute time as the ground clock second. Ken Seto
From: paparios on 5 Feb 2010 17:18 On 5 feb, 19:12, kenseto <kens...(a)erinet.com> wrote: > On Feb 5, 10:44 am, "papar...(a)gmail.com" <papar...(a)gmail.com> wrote: > > > What it is known is that no absolutes are needed, in order to predict > > what the results will be on a given physical experiment. Take GPS, for > > instance, where clock corrections on satellites, one based on SR and > > the other based on GR, are enough to ensure the necessary precision of > > the satellites clocks, by which the entire GPS system can perform as > > predicted. Those corrections do not need or care of some absolute > > reference frame located somewhere, far in the deep universe. Local > > frames of reference do quite well and work like a charm. > > The GPS uses absolute time to synch the satellite clock with the > ground clock as follows: > The GPS second is redefined to have 4.15 more periods of cs 133 > radiation than the ground clock second. This redefinition of the GPS > second is designed to make the GPS second contain the same amount of > absolute time as the ground clock second. > > Ken Seto- Now, can you back up this assertion of yours by pointing out to the exact page of the official GPS technical documentation, where it says that absolute time is used? No???..... Oh...but We knew that you can't!!! Just go back to your graveyard!!! Miguel Rios
From: eric gisse on 5 Feb 2010 19:33 kenseto wrote: [...] > The GPS uses absolute time to synch the satellite clock with the > ground clock as follows: > The GPS second is redefined to have 4.15 more periods of cs 133 > radiation than the ground clock second. This redefinition of the GPS > second is designed to make the GPS second contain the same amount of > absolute time as the ground clock second. > > Ken Seto And how is absolute time 'absolute' when it changes?
From: Ste on 5 Feb 2010 21:03 On 5 Feb, 15:47, PD <thedraperfam...(a)gmail.com> wrote: > On Feb 4, 3:21 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > And here is the result: > > > 1. The detector in X is midway between the events and so the distance > > > traveled by the signals are equal, as confirmed by an independent > > > measurement. > > > 2. The speed of the signals is equal, as confirmed by an independent > > > measurement. > > > 3. The signals arrive at the detector in X at the same time. > > > > Therefore the original events are simultaneous. > > > Ok, I think I can agree so far. > > > > 1'. The detector in Y is midway between the events and so the distance > > > traveled by the signals are equal, as confirmed by an independent > > > measurement. > > > 2'. The speed of the signals is equal, as confirmed by an independent > > > measurement. > > > 3'. The signals arrive at the detector in Y at different times. > > > Therefore the original events are not simultaneous. > > > I can conceive of a situation where this will be true, but I need you > > to specify the velocities. > > The visualization will come with Einstein's distillation, but I'll > toss in some numbers here so that you can make a sketch. > > Suppose events A and B are 10,000 m apart. The detectors X and Y are > obviously 5,000 m from each event. Detectors X and Y are in motion > relative to each other at a constant speed of 100,000 km/sec, along > the line that includes A, B, X, and Y. > > Now that you have some numbers, are you ready to proceed with the > discussion as I've outlined? So you have A, B, and X, all on a common axis, and Y moving along this axis relative to X at 100,000km/s? > > > Thus, depending on X or Y, the events are simultaneous or not > > > simultaneous. And since the same procedure is used in both, there is > > > no obvious way to determine which of these is "true" and why the other > > > is not "true". > > > The answer to this will have to turn on a specific discussion of the > > evidence. > > Actually it doesn't depend on the details of the evidence. We have > already determined that the procedure determines simultaneity or > nonsimultaneity unambiguously. No we haven't! If X and Y are moving in such a way as to be approaching one event and receding from the other, and if they are moving in *opposite* directions (relative to each other - they may in fact be both approaching one event and both receding from the other), then there will be no simultaneity at all, because there has to be a time interval for the measurement to take place, and if they are moving in opposite directions along an axis in common with A and B, then there is *no way* they can maintain equidistance for the whole of that time interval. The fault, therefore, lies in saying that X and Y are "midway between the events", when in fact they are not. > If the procedure is trustworthy in > frame X, then it is trustworthy in frame Y. If the two frames are > otherwise equivalent, there is no reason to say, "But the answer > arrived at in X is right and the answer in Y is wrong." We've already > agreed this procedure works. The procedure is not trustworthy. The two frames are not equivalent, because X and Y do *not* remain midway between the events for the entirely of the time interval (and, more importantly, the deviations from the midpoints are not symmetric).
From: Ste on 5 Feb 2010 21:04
On 5 Feb, 15:55, PD <thedraperfam...(a)gmail.com> wrote: > On Feb 4, 8:34 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > On 5 Feb, 01:12, artful <artful...(a)hotmail.com> wrote: > > > > On Feb 5, 11:49 am, kenseto <kens...(a)erinet.com> wrote: > > > > > On Feb 4, 6:04 pm, mpalenik <markpale...(a)gmail.com> wrote: > > > > > > On Feb 4, 5:59 pm, "kens...(a)erinet.com" <kens...(a)erinet.com> wrote: > > > > > > > It it does violate the PoR. You made the contradcictory claims that > > > > > > the pole can fit into the barn physically (materially) an at the same > > > > > > time you claim that the pole cannot fit into the barn physically > > > > > > (materially)......that a violation of the PoR. > > > > > > No. The doors are not closed simultaneously in the pole's frame, nor > > > > > are the two ends of the pole simultaneously in the barn in the pole's > > > > > reference frame. In the barn's frame, the two ends of the pole are in > > > > > the barn simultaneously and the doors shut simultaneously. In the > > > > > pole's frame, the two ends of the pole are in the barn at different > > > > > times and the doors shut at different times. > > > > > Sigh..You are making the contradictory claims: > > > > 1. The pole can fit into the barn with both doors close > > > > simultaneously. > > > > In the frame of the barn > > > > > 2. The pole cannot fit into the barn with both doors close > > > > simultaneously. > > > > In the frame of the pole > > > > Two different meanings for 'simultaneously'. So they are not > > > contradictory > > > > You really are not very good at thinking or arguing logically. > > > He seems perfectly reasonable to me. > > > He's saying that, if one stands in the middle of the barn equidistant > > from the doors on each side, and one closes the doors simultaneously > > (i.e. what I would call "absolutely simultaneously", but which for > > conveience we'll say "simultaneous according to an observer standing > > equidistant from each door), then is it possible that both doors can > > appear closed while the ladder is observed to be inside the barn. > > > It's a simple question, and the answer is "no!". > > Your conclusion "no" is in conflict with experimental measurement. > When intuition conflicts with experimental measurement, then it is > intuition that must give way. I checked Paul before I gave this answer. Length contraction has never been experimentally tested. So my intuition does *not* conflict with experimental evidence. |