I don't know if I am one of your 'anti-relativists' or not, but I consider myself pro science. If I were capable of becoming a physicist, I suppose I would have to be an experimentalist instead of a theorist. I firmly believe if there is a discrepancy between theory and empirical evidence, evidence should rule. Einstein may have been a brilliant physicist, but mother nature is smarter. James R, you and funkstar are talking strictly theory. Funkstar's post is assuming that because a 'time stamp' from a earth clock (st_e) arrives at the earth-synched SV clock (t_gps), everything is in synch in THAT FRAME (earth) and the system works properly. You, James R, said 'that's right' and then brought up the SRT prediction that simultaneity would keep the two frames from being synchronized in the satellite frame of reference by this explaination. You are correct, James R, Special Relativity DOES predict that. Now, the empirical evidence, AGAIN. The evidence you avoid addressing. The 'time stamps' are NOT sent from earth to satellite. They are sent from the satellites to the earth surface clocks, many of them, located at all latitudes. They are from the SATELLITE constellation frame of reference to the Earth- surface frame of reference. The clocks were synchronized in the EARTH frame, not the satellite frame. According to STR, the SV clocks will not be synchronized with Earth surface clocks in this frame of reference. But they ARE James R. ALL satellite clocks are synchronized with ALL atomic clocks, UTC clocks, everywhere on the surface of the Earth, equator or north pole. THIS is what you avoid addressing. If I seem anti-relativity (not anti-relativist, there is a difference), there are reasons.
I've read that the effect of latititudinal velocity directly factors out with the change in gravitational redshift by being slighter longer from the center of the earth by the flattening around the rotational axis. So all sea level clocks are beating synchronously. I'm not certain it is true. That's what I did. The issue at hand is velocity time dilation. First of all, I directly stated that I didn't care about the gravitational redshift because it's easy to keep the clocks synchronized across this effect by lengthening the SV second by gamma_g. Second of all, The gravitational redshift shortens the SV proper day as seen from earth by 45 microseconds a day, but the SV clocks is only calibrated to tick slower by 38 microseconds a day. Ignoring the contribution from gravitational redshift then amounts to the SV defined day having having been shortened by 7 microseconds. Just as I said. The satellites are synchronized in the ECI frame, as far as I've read... Of course, but the issue was synchronization so we have to switch between frames. And I explained, very carefully, why time stamps from the earth to the SV will match perfectly, and why time stamps from the SV to the earth will match perfectly. From the SV's point of view, a time stamp st_gps, sent to arrive at the earth clock at exactly time st_gps gps seconds in the satellite frame will be viewed from earth as arriving at time gamma * st_gps (in gps seconds). That's the Lorentz transforms. That's how you switch between frames. Now, 1 gps second is 1/gamma standard seconds long, so time gamma * st_gps (in gps seconds) = st_gps (in standard seconds). That is, from the earth the time stamps are arriving perfectly. This does not imply that mutual time dilation isn't taking place, and in fact corroborates it. The Lorentz transforms explain it fully. Please do. I don't seem to be able to see how you can claim "true" synchronicity without switching between frames. I know you're not, but you still seem to have missed that the satellites are synchronized to the ECI frame.
2inquisitive: I agree 100%. If there is a clear discrepancy between theory and observation, observation wins and the theory must change. Again, I agree. The GPS system is set up to work in the Earth frame. And it does. ... in the Earth frame.
I agree too but one thing you fail to point out is that there could be more than one theory for a particular observation. Each theory could be equally valid in explaining the observation, especially when the theories are based on a set of postulates or assumptions which are impossible to prove conclusively. It's just that relativity is based on the postulate that speed of light is constant to all observers and as this APPEARS to be the case up to now, it is virtually impossible to derive another theory. But if ever the speed of light being constant and time dilation is ever proved to be a false observation, do you think we could develop alternative theories?
Many physicists right now are looking for a better theory than Einstein's relativity. In particular, they are trying to find a quantum theory which matches the observations as well as Einstein's theory. When we have such a theory, then we can throw away our current best theory: relativity. Of course, rather than relativity being thrown out completely, it is much more likely that it will be found to be an approximation to the new, more accurate and complete theory, whatever it is - just as Newtonian physics was found to be an approximation to the more accurate theory of relativity.
janus58, The observer on the plane and the activities of James R and MacM are simultaneous. The plane observer merely receives thje information later. Assume the plane observer knows the fundamental laws of physics at least to the level that the transfer of information is necessarily greater than zero. The plane observer is not ready to construct an ersatz physical structure just because he receives information delayed wrt to what JamesR and MacM perceive. Janus58, you seem to reject the reality that there is activity on the "other side of the universe" occuring at this very second, the second, the instant you are reading this post. The fact that the information is delayed and even for the fact that the determination of the exact time of some event far yonder is technologically improbable does not mean that events way over yonder are not simultaneous, right now! I type this post knowing you are not going to read it for some mintutes, at the very least, but that does not mean that you aren't engaged in some activity right now as I type: eating, typing, sleeping, whatever. Your misuse of the word "simultaneity" is deceptive. You know good and well that events, in fact the vast and overwhelming number of activities occuring in the universe at this very minute as well as every minute of your existsence, before, during and after, are occuring and you have absolutely no information about those activities what so ever. Do you deny the universe is active even though beyond your observation? However, the very trivially small number of activities that you do measure, with the intrinsic time delay (in most of the activities) are motivation to construct some scientific structure of "relativity of simultaneity"? What is simultaneous in inertial frame A moving wrt inertial frame B is not simultaneous in the B inertial frame for the trivially obvious reasons that information does not transfer instantaneously (EPR entanglement activities the exception)from A to B or from B to A? The AE gedanken where lightning strikes at equal distances form the train observer who is colocated with the midpoint between the lightning strikes is deemed non-simultaneous from the observer on the train. Why? Because the observer sees the light coming from in front before she sees the light coming from behind, and the observer has assumed she is at rest wrt the embankment moving from her front to her rear. AE claimed that all passengers on the train must conclude as the observer. However, AE does not discuss the fact that there are some passengers that are colocated with the arrival of the light at the midpoint in the stationary frame, simultaneously. AE does not discuss that observers on the train co-located with the lightning strikes fore and aft both measure the same emission time of the lightning they having synchronized clocks. AE does not discuss that the observer, by virtue of AE's "equivalnce of frames postulate" can just as well be justified in assuming she is moving and the embankment is stationary; that the train is the only entity in the two frame system that accelerated and achieved the intrinsic speed that unambiguously accounts for 100% of the relative motion. For this kind of scientific analysis those objecting to the conclusions of "relativity of simutaneity" are chastised for rejecting the "counter intuitive". AE does not discuss that the Observer, one passenger actally, determined the conditions "measured" that ultimnately resulted [erroneously] in the loss of simultaneity, and the loss of absolute time and space. AE didn't discuss that the passengers weren't consulted, nor allowed to be involved in the decision of whether they considered the lightning strikes occuring simultaneously in the moving frame. For AE's gedanken to have any value as a scnetific construct look at all the data discarded and unconsidered before during and after the train accelerated out of the previous station. Look at how consciously blind the observer has to be inorder to give any justification for her conclusions? The arrival times of the photons at the position of the observer located at her unique postion on the train can be analyzed using train clocks that explains all the so called sequential arrival times of the light at the observer's position. Let us use another similar gedanken only the lights are generated at the midpoint of mirrors [where the lightning strikes occurred in the former experiment, only now the mirrors are on the train as well as the embankment colocated when the lights were emitted] just as the observer passes through the midpoint. Here, the observer will say the lights were emitted simultaneously as the observer saw them emitted at the same time and place, as did the stationary observer. Again, she does this by rejecting the option of seeing herself in motion and the embankment stationary, a most unscientific choice. She will also say the lights arrived at the mirrors on her frame simultaneously though the staionary observer sees the lights arriving sequentially. If the mirrors are also clocks that record the arrival times then there is no way there can be two different times recorded by the clocks for one event. Even if the stationary frame and moving frame clocks are not sycnchronized, the frame clocks are synchronuized and from symmetry considerations the clocks will indicate sequerntial arrival times of the lights. Janus58, it is only from the conscious discarding of data and observations that the structure of realtivity of simultaneity is produced and fed to an unsuspecting public both scientific and general population alike. Geistkiesel Please Register or Log in to view the hidden image!
As I have pointed out many times the general gamma calculation seems justified. It is some of the assumptions which lead to reciprocity where SRT is flawed. The absolute view results in the same general functions as SRT but without the impossible and unsupported recipocal predictions of SRT. There is simply no justification to disregard the possibility of an absolute space.
Now why on earth would I do that? Please Register or Log in to view the hidden image! Just when the falicy of your view is being exposed. You (and SRT you support) claims spatial distance contracts for a moving observer. A--------------------------->B with "A" at rest = 1 lyr. A-------------->B with "A" moving at 0.866c = 0.5 lyr, making the trip in 0.5773 years. The above claim is assinine on its surface and only exposes the lack of physical reasoning on your part and others. To make the claim of spatial contraction you ignore the fact that the proper time tick rate is claimed to be reduced to 50% of that of its tick rate at rest. Hence it is more valid to believe that the moving observer merely sees the trip taking less time or having a higher velocity: A---------------------------->B at 0.866c goes 1 lyr distance in 0.5773 years means moving observers compute a higher velcity than stationary observers. In this case it would appear to the moving observer that he had achieved a velocity of 1.73c. You cannot simply disregard the FACT that the moving clock is ticking slower. which accounts for the travel time with no change in spatial distance. v = d/t Your SRT prediction is based on falsely equating each proper time as having the same tick rate when it is known and recorded fact that the moving clock ticks slower. Taking that into account there is no room in physics for a changing spatial dimension. PS: None has ever been observed nor recorded.
i.e. this is the view in A's rest frame. i.e. this is the view in B's rest frame. Two different frames - two different results. Of course, you can't cope with the existence of more than one frame. You think there is only one. Neither A nor B's "proper tick rate" is reduced, ever. In fact, it never changes, ever. But "reciprocity" demands that if I see you travelling at 0.866c, then you see me travelling at 0.866c. Right? Or don't you believe in "reciprocity" any more? Flip flop. The moving clock only ticks slower in the stationary clock's frame, not in its own frame. There is no recorded instance of a clock at rest ever ticking slower, anywhere.
Pardon my bluntness but horseshit. To reduce this issue to something a bit more understandable. Take two clocks A and B with observers in seperate cars. Arbitrarily calibrate B clock to run at a tick rate of 0.5 ticks per tick of the standard monitor clock A. Now take a drive, go 30 miles at 60 miles per hour according to the standard clock. Clock A takes 30 minutes according to that clock. Clock B takes 15 miutes to make the same trip according to his clock. Are you gong to argue that the distance changed or that absolute velocity changed? Hell no. But B would calculate that he had traveled 120 Mph not 60 Mph. That is precisely the same situation with time dilation at relavistic velocities. You ignore the clock tick rate differential when you claim length contraction. It does not happen.
ARGH!! These arguments are pointless (I am not singling you out James R, MacM included). You guys have been arguing this point for as long as I can remember (ok, I haven't been here that long, and part of the time the forum was down). But neither of you are accepting the same premises and arguing that your respective versions are correct. There is MacM's premise: time-dilation only and James R's premise: Einstein's postulates. This situation leaves the two of you attacking the same problem in a different way and coming to different conclusions. There is no point in arguing these conclusions, neither can be proven! I've not seen experimental evidence for length contraction or reciprocity - but that is not enough for me to say they don't exist and agree with MacM. Maybe you two just can't get through the day without arguing with each other.
Sorry you find this frustrating AER but the physics are on my side. James R can only recite theory. Until he admits that I will continue to debate his posts. Now you say you are not prepared to accept my conclusion. I am curious as to why you reject the simple fact that time dilation accounts for the differenace in trip time and therefore leaves length contraction as bogus. Especially since time dilation is recorded fact and length contraction is only hypothetical ignoring the time dilation of the clock measuring the trip.
What you've done here is to prove that length contraction is as real as time dilation. B would not calculate that he travelled at 120Mph. In order for him to see that he travels at 60Mph, there has to be a length contraction. And, if there is no length contraction, the velocity of light would be different for different observers. So you're saying that the Michelson-Morely experiment and all the other experiments were not able to measure a relative velocity with respect to light, because they were all dummies, and that you've conducted experiments which prove that length contraction is only an illusion which fools us stupid relativists. You're saying that if I observe you to be moving at 60 Mph, then you would see me moving at 120 Mph. Okay, how do you decide which observer measures the higher velocity? Oh wait! I know. There's the 'velocity history' to consider. (I've looked at the entire Reference Frames post). So, there's someone up there who remembers your velocity history and makes sure you observe a higher velocity. Since time dilation isn't mutual, I believe. If that were so, then wouldn't we be able to determine our absolute velocity? Why hasn't anyone done this? Oh yeah, they didn't know about the great MacM Effect of Biased Velocity. Please conduct the experiment and get back to us when you determine the absolute velocity of Earth. Man, I can't believe this guy.
I did not say that I accepted or rejected either. Note that your interpretation would require a local ether around massive bodies (This would be the postulate you would have to assume in any type of derivation).
MacM: That is: B takes the drive while A remains stationary, I assume. That is: B takes 30 minutes for the trip, according to clock A. Well, approximately, ignoring relativistic effects. Yes, but we know B's clock is set to run slow, so B is incorrect. No, because at relativistic speeds, time dilation occurs. No I don't. You wouldn't know physics if it danced naked on a piano singing "look at me, I'm physics!"
