Let me ask you something, Mac, that may clear things up a little. ALL clocks on ALL satellites HAVE to remain synchronized with EACH OTHER for the system to work, they have to keep the SAME time and they have to know their position at all times for the system to work. When a receiver takes a reading from 4 satellites to determine its (the receiver's) location, the readings MUST correlate to at exact moment in time for each of the satellites and the satellites position in orbit. The receiver can synchronize itself to the satellites time, but all satellites MUST have the same time. Satellite orbits are in different planes, one equatorial and then spread out every 55% for a total of six orbital planes. THAT is the problem for any theory that uses relative velocity for time dilation. GR is not effected because it is not based on relative velocity, but from a location in a gravity well. In some orbital planes, one satellite may be approaching another at a angle and receeding from another at an angle, but all have to have have the exact same time or the system doesn't work. How do you synchronize THOSE clocks on the satellites between each other? They are the ones that matter, the earth clock is not much more than a set of algorithms used to triangulate readings and synchronize itself with the satellite's clock. The satellites can even synchronize their own clocks between each other without contact from a ground controller for up to 180 days if they need to. How do the satellite clocks synchronize between each other if relative velocity between themselves leads to time dilation? The Earth based clocks are not really important, they only use quartz clocks much like an inexpensive watch, the signals they recieve from the satellites is what is important.
It is a complex system to say the least. I don't think I could do justice trying to describe it. The one link I provided shows 15 algorithums going into the system. But basically as I understand it they don't compute relative velocity between satellites. Each satellite communicates data referenced to the earths axis and a Sagnac signal. That is each clock is kept relative to the referance frame and not between each other.
No, Mac, you are only thinking of the main ground controller. The signal the satellites send to the GPS RECEIVER is what is important. That signal is encoded to give the satellites exact position in its orbit at an exact moment in time. Just knowing the distance the signal travels doesn't let the GPS receiver determine its own location on Earth. The GPS receiver has to triangulate signals from at least three satellites that send their own position in orbit at the exact same instant in time. The signal from the 4th satellite is used to synchronize the GPS reciever clock with ALL the satellites clocks. The satellites are not geostationary, they are orbiting the Earth in very precise orbits every 12 hours (actually less, as a sidereal time orbit is used, based on star-based orbit time instead of sun-based). Light will travel over 300 meters in one microsecond, so the measured time has to be accurate in nanoseconds. The GPS clocks are not that accurate, the time is actually transmitted by the satellites themselves, encoded in the 'pulse.' But the satellite clocks themselves have to be accurate between themselves to just a few nanoseconds. 7.2 microseconds would be a huge error, amounting to over 2100 meters. But the thing to remember is the satellite clocks themselves and how they keep such accurate time between themselves when they have DIFFERENT RELATIVE VELOCITIES to each other. Synchronizing their time with an Earth pole does not eliminate this concern, that only helps with the main control station, not the GPS recievers themselves. GPS works because there is no such thing as time dilation due to relative velocity, the only timing difference is due to position in the gravity well, the 38.4 microseconds per day that is precalibrated into the satellite clocks that let them run at the same rate as an Earth clock. The satellite clocks themselves could stay synchronized with each other with NO precalibration, but they would run at a different rate as an Earth clock and screw up the time and distance measurements of the GPS reciever and be out of synch with the main control station. This ECI frame James R spoke of is really nothing more than Newtonian mechanics in disguise, it is the same as your 'earth axis frame' also. In my humble opinion.
I thought of another way I might explain what I see as the problem. We will use just two satellites and one ground observer. If the two satellites were both traveling at identical speed to cause a 7.2 microsecond delay between their time and the Earth observers time, the satellites clocks could be recalibrated so that their clocks would match the Earth observer's clock, each running 7.2 microseconds 'fast.' They would be in synch with the Earth clock according to the Earth observer's 'view.' But what about each other? If they were traveling side by side, they would see no dilation between them because their was no relative velocity between them. If the were traveling meeting each other, there would be a doubling of their relative velocity between each other compared to the 'Earth view.' Having the satellites synched to the Earth clock DOES NOT synch them to each other's clock. In the GPS system, they MUST be synched to EACH OTHER for the system to work. They have to be synched to a matter of a few nanoseconds. In the true GPS system, there are 24 satellites that have to be synched to each other even though they fly different orbits and have different relative velocities WRT each other. So, the way I see it, there can be no time dilation due to RELATIVE VELOCITY and still have the system work. Gravity, no problem. Edit: tried to make it clearer
Two points: 1 - I would like to agree that there is no relative velocity affect but I think that would be incorrect considering our observations. 2 - I do not think the GPS ever uses the relative velocity between satellites. That is why it is an LR system not SR system. All referances are to the preferred frame, the earth's axis. Triangulation and Sagnac and the many algorithums brings it all together. But the SR view of relative velocity without a preferred frame is not applied in the GPS.
(1) What observations, Mac? (2) Oh, but they CAN coordinate their time between themselves. I have pointed it out several times. It is called AUTONAV, in which the satellites can coordinate their clock time and their position in orbit among themselves for up to 180 days with NO degradation of service. You keep forgetting the precision necessary for the system to work. Each satellite clock has to have exact UTC time and their exact position in orbit in the signal they broadcast to the GPS receivers. They each broadcast two types of signals, one containing the exact UTC time and positional information, along with other information that pertains to accuracy, such as atmospheric effects and even effects caused by the solar wind, for instance. The other signals broadcast by the satellites are the psuedo random signals which the GPS reciever uses for the actual synchronization of clocks and determing distance to each satellite, the receivers don't actually measure distance by 'timing the delay', they match the PRC signals with one contained within the receiver in a manner somewhat like how a interferometer (sp) works, matching frequencies. EDIT: That sounded confusing, interferometers match frequencies, but GPS recievers don't match frequencies, they match random 'humps and bumps' within the same frequency in a somewhat similar method for time sync. But when four satellites are used, you guessed it, all four satellites have to be synchronized in time before the system will work. By the way, I have had my AHA! moment, a big one. I know how GPS is also falsifying GENERAL RELATIVITY! It will take a while to explain when I have more time, I just ran across some information last night and when I awoke today, AHA! It hit me. I was right, time is based on gravity alone, the equivalence of gravity and acceleration is not true, and the speed of light changes according to the intensity of the gravitational field it is in! Later.
Perhaps you should think before responding? I said "No, I admit that different tick rates will be seen.... as in LR." Are you now saying that LR says the sat's clock ticks slower, but the Earth clock will appear to be fine to the sat? I don't think so.... hence nothing was wrong with the statement.
My comment was directed at your closing comment: It does appear that there exists a dilation of clock ticks (that may not indicate a change in time however). The point I believe however is that this is computed through the common rest frame of the earth's axis. That is they calculate distance, Sagnac, signal inbound and out bound time, etc to determine orbit speed and position. From that one can compute relative velocity of satellites. But to my knowledge there is no SR adjustment for that relative velocity. That has been the point. The LR referance frame eliminates even considering the SR affect between orbiting clocks. What counts is the time between the satellite and the earth bound UTC clocks. Each satellite stays synchronized to that. If you start trying to play around with SR between 24 satellites with different velocities and motion angles you now have clocks that are giving you 24 different readings which are constantly changing. (and that would be just from one satellite view). I am not a mathematician but the possible combinations of satellite views could be someting on the order of 24<sup>24</sup>! I can agree with this paragraph altough I am not as familiar as you appear to be with the process details. But note nowhere has these satellites been concerned nor calculate the affect on time regarding their vbelocity to other satellites. Each is synchronized to the UTC, not to each other. Interesting. I have been holding back until this issue was fully resolved but I have already found test data showing radar tests of mercury, venus and mars, that showed additional delay if the beam passed near the sun. Please Register or Log in to view the hidden image! One consideration was that this result could indicate light had slowed down in the higher gravity field. (Hint: Light velocity may not actually be invariant).
I guess I am not understanding your position. Using the earth's axis as a local absolute rest frame and orbiting clocks being calibrated (net slow down of 38.+ micro-seconds/day), they become synchronized to the UTC clocks. The surface clocks have no relative velocity to the earth axis referance frame. They are then viewed as synchronized from orbit. The SR arguement that from orbit that the UTC surface clocks must run slower doesn't hold true in physical reality. That if SR was valid earth clocks would need to appear to run slow from the perspective of the orbiting clocks. But they don't. That in contrast to what James R claimed regarding my "Monitor Clock" calibrations where he claimed I could not synchronize clocks, such calibration does indeed synchronize clocks which supports my view and not SR as has been claimed. Relativity of Simultaneity is indeed eliminated by offset calibration of the moving clock. Slowing down that clock has the same affect as speeding up the other clock such that when you take the opposing view they remain synchronized. A = 36,000 B = 15,692 A viewed from B was 6,840, as per James R. My B's calibrated monitor clock of A. A = 36,000 B = 15,692 A viewed from B = 6,840 MA = 36,000 I argued that this calibration defeated simultaneity and SR and would remain synchronized. James R and you along with the others all argued against that view. But GPS is nothing more than my MA clock. This is made possible by picking a referance which is unchanging and not the changing relative velocity between clocks on the rotating surface vs the orbiting clocks. It worked in my clock string because it too was an unchanging relationship of constant relative velocity.
MacM: Of course it requires different synchronisation to synchronise the clocks in a different reference frame. What did you expect? It is only your incorrect assumption of the existence of an absolute reference frame which makes this a problem for you. This is an assertion your repeat over and over again, with nothing to back it up. Give it a rest, or at least try to back it up with something. Well, yes. That is what "time dilation" means, silly. Yes you can. You just compensate for it with a mathematical calculation, if you need the orbit view. Or, if you want to perform the calculation in orbit, you take into account that you are using that frame. Re-read my statement. You must learn to read more carefully, so you don't keep stumbling into these straw man comments. If GR is true, so is SR. SR is contained within GR. This is only your opinion, nothing more. Who cares what you think? You're wrong all the time, anyway. Show me why. No unsupported assertions, please. I argued that it would only work in one frame of reference. You can calibrate for one frame, but not more than one, since doing so would require an absolute universal time, which does not exist. I realise that this point went completely over your head. What understanding? It is clear you know next to nothing about relativity. Because of the MacM "reciprocity" principle, right? The same one which is not a part of Einstein's theory. Please provide a link which supports this statement. Why would they need to calculate relative velocity between satellites? The only relative velocity which is relevant is the relative velocity between the ground-based receiver and the satellite. ---- I notice you are now dragging yet another thread across into this one - the one on your 2-clock experiment. Please keep that discussion in that thread in future. Your method was useless in calibrating the clocks, for reasons I explained in detail in the appropriate thread. I will not repeat myself here. Because it was wrong. See the relevant thread. Re-read it. Your MA clock was claimed to do much more than what GPS does, but that is another topic.
Which confirmed the predictions of General Relativity. Another triumph for Einstein! (Start a new thread if you want to discuss this further validation of relativity.)
James R, wouldn't the 'delay' suggest a slowing down of the speed of light physically, as opposed to relatively? Geistkiesel?
That has been my point. They will only accept those interpretations which favor their advocated view. Other equally valid interpretations are ignored. The ignored interpretation invalidates their theory. Their chance of being correct is only 50/50 as in all the other interpretations they elect to accept. When data clearly invalidates their theory they simply blow it off and claim it is shoddy work or crap from a Crackpot and never attempt to verify the finding.
by James R: "Of course it requires different synchronisation to synchronise the clocks in a different reference frame. What did you expect? It is only your incorrect assumption of the existence of an absolute reference frame which makes this a problem for you." =========================================================== But there IS an absolute reference frame, James R. It is the Earth Centered Inertial frame. Let me see if I can explain a little of the geometery of the GPS system in simple terms. The best way I can think of is to use a globe of the Earth mounted in a frame in which the globe can be rotated. There are several reference frames in use in the GPS system, not one. The absolute reference frame, the ECI frame, can be compared to the frame which holds the globe of the Earth. It uses the center of the Earth, or globe, as one point in the reference frame. The center of the Earth is a point defined as the intersection of two lines, one running through the Earth from pole to pole along the axis of rotation, the other running through the Earth equator to equator extending to the vernal equanox. The vernal equanox is an imaginary point in space where the Sun crosses this line in the spring, on the way from its orbital plane south of the equator during a northern hemisphere winter to an orbital plane north of the equator during a northern hemisphere summer. The two reference points for the Earth Centered Inertial frame is center of the Earth and the vernal equanox and it is an absolute, non-rotating frame of reference in the GPS system, the same as a point attached the the frame holding the globe of the Earth in that example. The Earth rotates within this frame, but the frame does not, it is an absolute reference point. The next frame of reference to consider is the Earth-Centered Earth-Fixed frame. Again, the center of the Earth is one point of reference, but the other point is different. A mathematical model is constructed to represent the surface of the Earth from this center point, a sphere in other words, the surface of the globe in my example. This frame rotates, the same as spinning the globe within the frame holding it. The ECEF frame rotates within the ECI frame, and both have one point in common, the center of the Earth. An 'X' is placed on the mathematical surface of the ECEF (Earth-Centered Earth-Fixed) frame, the Control Center at Schriever AFB in the GPS system. And then, of course, you have the frame of the GPS satellites themselves in another frame, in which the satellite constellation is one 'point' and the center of the Earth is the other. They have no relative velocity wrt the center of the Earth. They have no relative velocity wrt each other the way the GPS system is set up. The only relative velocity to consider is relative to the constellation's orbit around the mathematical surface of the ECEF frame. That is where the measurements are taken by the GPS receiver vs. the individual satellites it uses for triangulation and time synch. The NAVSTAR satellites carry extremely accurate atomic clocks and broadcast coherent SIMULTANEOUS signals. It is necessary for the GPS receiver to know exactly where each of the satellites are in their orbits and at exactly the same instant in time for the system to work. There is no time dilation due to relative velocity accounted for in the system, only the preset rate change due to the satellite clocks running at a faster rate in a decreased gravitational field. Time dilation due to relative velocity is NOT preset before launch or the satellite clocks would accumilate this 7 microseconds per day over a years time and be 2555 microseconds off from the ECI frame each year. That doesn't happen, the satellites are off by one second due to the 'slowing' of the Earth's rotation each year.
No that hasn't been your point, and if it was you are more wrong then previously thought. A slowing down of light IS seen due to the atmosphere. This however would not and could not explain a continuous increasing delay as would be seen in GPS. This isn't that they are 2 seconds slower, this is that they are X% slower.
OK, Mac, now we will get to the point I made in an earlier post about explaining how to make a clock run faster using your bent trajectory for light diagram. Remember the Earth Centered Inertial frame does not rotate in the GPS system, it is fixed between the center of the Earth and the vernal equanox, near the sun. Place the moon on the same side of Earth as the sun and also place one of the GPS satellites on this same side. The speed of light is a fixed amount between the satellite clock and the GPS receiver in this arrangement of participants. Now let the satellite orbit to the opposite side of the Earth while keeping the moon and sun in the same location. Modelling of the GPS system over an extended period of time shows the speed of light to INCREASE when the satellite is on the opposite side of Earth as the moon and the sun. How do you draw your lines to represent this increase in the speed of light in this INERTIAL frame of reference? GR is not a factor. The gravitational field was more intense on the side of Earth when the moon and the sun were together than it was on the opposite side of the Earth. The speed of light increased when in the less intense gravitational field opposite the sun and moon. As I have said before, I believe the gravitational field is the key to time and the speed of light, light propagates through a gravitational field, the speed of light and time changes according to the intensity of this field. An observer measures the speed of light as a constant according to his location in the field, but the speed of light there is not the same relative to someone in a more or less intensive gravitational field. Time dilation due to relative velocity is only an 'observational' effect, it would not one twin to actually age less than the other when they were reunited. Differences in age could occur due to differences in gravitational fields, but the effect would be small unless one were to spend considerable time in a very high gravity area. Just my thoughts and opinion and why I think as I do.
Gibberish. Don't pretend to know what my point has been. You clearly do not know or if you do you deliberately distort it for your own arguementative purposes. "2 seconds.....X%"??????? Show me where any such comments have been made. I make a general observation that the delay may be from one of two sources. 1 - Greater distance due to curved space. 2 - Decreased light velocity in a gravity field and light velocity is not invariant as claimed.
2Inquisitive, My only comment about your posts above is that there does seem to be a slowing of clocks due to relative velocity. The 7.2 micro-seconds/day in GPS is adjusted for. That adjustment is a rate of tick adjustment and it does have an accumulative offset in the pre-launch calibration. However, that velocity affect is not between surface clocks and the orbiting clock. I am unclear as to what it actually is but I assume it has to do with orbit velocity.
Can you be more specific on this adjustment matter particularly about "accumulative offset in the pre-launch calibration"? What does that mean? Does it mean the clocks were calibrated by giving them an X seconds faster or slower (than those on earth) before they were put on orbit?
