RitterSport, you are missing the point, whether deliberately or not I do not know. The satellites’ clocks are adjusted to match each other. That is it - no adjustment is needed to synchronise with any place on Earth. They are adjusted (synchronised is a better word) so that they are all, well, synchronised. Now all that your GPS Rx has to do is compare the timestamps from eg four satellites and it knows (to use the bathetic principle) where it is.
Tom Hollings.
Frances Vaughan, RTFB.
That’s true (maybe? They are in different orbits, so that might be a problem anyway), but if they didn’t have the adjustment, they would have the wrong actual time. They are adjusted so that they have the correct time, and to match the US time standard in Colorado. They have extremely accurate atomic clocks – why do you think they need to make that adjustment to match the clocks on earth?
Frances Vaughn, I am not providing any mathematical structure. A faster than light speed test for a physical object has never been done, except for a proton in a particle accelerator, which is being pushed along the PA by an electro magnetic force which is itself constrained to lightspeed and therefore not a valid test. A valid test is to use a rocket ship with its internal rocket motor (and of course a very large amount of fuel, or use a Bussard Ramjet). It cannot be tested by using a light sail powered vehicle.
The analogy which I use for the PA is a row of hockey players stationary on the ice. Lets say the players can swing their sticks so the tip speed is 50mph (use any unit you want), and further assume that the ice is frictionless. The first player swings his stick and hits the stationary puck at 50mph. The puck is accelerated by the stick and moves off at 50mph and reaches the next player. He swings his stick (also at 50mph), so even if he times his stroke perfectly so the stick is in contact with the puck, it cannot speed the puck up, it is still moving at 50mph. This applies all the way down the line of players. The puck will go past the last player with a speed of 50mph.
Swap electro magnetic force for hockey stick , and you have the reason why the proton in the PA cannot be accelerated faster than lightspeed.
If one theory can explain an observed phenomena, it does not mean that no other theory can explain it.
I have already matched that in the form of a thought experiment. The rocket ship with its internal rocket motor accelerates away. I place the observer in the rocket exhaust (or reference frame 1 if you prefer). You may have seen it on this thread. If not, I can put it on again. Do not forget that ALL Einstein’s reference frames are equal, so there is no reason why I cannot use that one.
I started with the MMX (or maybe it was just a step on the route) many years ago. The MMX null result can be explained very easily by lightspeed being c/n in the atmosphere. Which it is, there is no dispute about that. so what is c/n with respect to? The atmosphere of course!
Tom Hollings.
Andy L, very clever, Einstein would have been proud of you. Or perhaps not. By changing your starting point for the perpendicular lines, you changed reference frames. Did you hope I wouldn’t notice? Don’t bother answering, as I won’t read or reply to any of your comments any more.
Tom Hollings
If this is true and if a rocket can go faster than the speed of light then the increase in speed can be described by math. Please do so.
You have just made a factual statement (that the clocks don’t have to be synchronized to match the clocks in Colorado). Every other poster in this thread knows this claim is false. Since this is GQ, I challenge you to come up with a cite. Or else desist.
Thank you.
And thank you. I didn’t mean to humiliate you by pointing out your errors, and I wish you the best in your effort to ignore facts that you don’t like. I am relieved to have the responsibility for your education lifted off my shoulders.
Just to complete the analogy. If the rulers remain straight and intersect at only one point, you can take the fact that a person using ruler A as the definition of length will see ruler B as reading too high, and a person using ruler B will see ruler B as reading too high, as simply a matter of appearances, just as the fact that two people traveling at a constant relative velocity will each see the other’s clock as reading slow. But if you bend one ruler (say, ruler B) so that it intersects ruler A at a second point, the rulers will have different values for the same point (of course they will, since ruler B traveled further) – this is perfectly analogous to the “twin paradox” in which the twin who turns around to come home will be seen to have aged less than the twin who stayed home (the bending of Ruler B is analogous to the acceleration of the traveling twin when he heads back home) - except for the fact that in SR, the analog to distance is “interval” which has that pesky negative sign.
Yeah, looking at this, if you extend a perpendicular line from each inch marking on both rulers, both rulers ‘measure’ each other as wrongly scaled; both of them observe the same change in scale for each other (or to put it another way, from the reference of each ruler, both rulers think the other ruler is wrong, in exactly the same way).
I thought it was quite a good analogy for two observers each seeing the same distortion from their own reference frames. Tom’s complaint ‘you changed reference frames’ is the most absurd thing yet, since the subject of discussion was how two different reference frames would see each other.
You can’t win this argument. He’s not even paying attention.
Thanks.
In fact, the two-rulers analogy is so close of an analogy that it almost isn’t even an analogy at all. It’s exactly like that, except for that pesky negative sign.
That is both unnecessarily rude and useless.
You don’t have a cite. I’ll take it as confirmation that you don’t.
I very much doubt you have ever read anything written by Einstein and actually have no clue what special relativity is.
One, spell my name correctly please.
Two, you most certainly are providing a mathematical structure, but you just don’t realise it. You are directly contradicting a result of special relativity. I think you think you are agreeing with special relativity but don’t realise that this implies a mathematical structure that you are claiming a variation of. Special relativity is a mathematical structure. You are claiming a physical reality that is at variance with that structure. That requires mathematics. Hand waving assertions are not physics.
I’ve explained once already how this isn’t true, and you didn’t get it. Again, this is still not true. The travelling wave of the field intensity can trivially exceed the speed of light. The analogue with the swinging hockey players isn’t how accelerators work.
So if the arms of the interferometers are in vacuum, you claim the result will be different?
That is a testable experiment. Very good. You know, that is such an important and trivially testable experiment that if you can perform the experiment with a vacuum in the arms and get the result you claim, I absolutely guarantee you will get the Nobel Prize.
Now off you go.
Agreed.
He’s devoted most of the lifetime of the Internet to making the same arguments in literally the same language, while real-world physicists have done thousands of experiments, each one falling to disprove relativity. He essentially dismisses them as Big Physics, who have an incentive to lie about the big truth he’s spotted.
If all of reality fails to make a dent, I think we can be assured that no attention is being paid to our arguments or questions. The only audience is those of us who appreciate the time and care real-world physicists put into enlightening the interested laypeople here.
Hari Seldon (I see you are an Asimov fan), The satellites’ clocks do not have to be synchronised with anywhere on Earth for GPS to function. There is however the synchronisinging of ground-monitoring stations to be done. There are six monitoring stations located roughly along the equator and these need to be kept in-synch with each other. They are therefore synchronised with the satellites, but that synchronisation has nothing to do with the day to day operation of the GPS in locating a user’s position.
If you want to be pedantic, “no adjustment is needed to synchronise with any place on Earth” can be changed to :- “during normal operation no adjustment is needed to synchronise with any place on Earth .”
Tom Hollings.
Francis Vaughan, do not make assumptions. I learned relativity in about 1970, and for a while was a believer. Doubts began to creep in though, especially about the clock paradox. I challenge you to answer this question set by Professor Dingle many years ago :-
“Two exactly similar clocks, A and B, are in uniform relative motion. Einstein’s special relativity theory requires (1) that the motion is wholly relative, i.e. it belongs no more to one dock than to the other; (2) that the clocks work at different rates, i.e. one works faster than the other. My question is: what, consistently with the theory, determines which clock works the faster?
Suppose the relative velocity is 161,000 miles a second. Then, according to the theory, the time according to one clock (A, say) between the readings 1.0 and 2.0 o’clock of B is 2 hrs., so that A works twice as fast as B. This is a particular case of a general result obtained by Einstein in 1905 and universally accepted. But, similarly, the theory requires that the time according to B between the readings 1.0 and 2.0 o’clock of A is 2 hrs., so that B works twice as fast as A. (Einstein did not consider this case). These results are clearly contradictory.
My conclusion is that the theory must be false, since it demands that each of two clocks works faster than the other, which is impossible. Otherwise, something must determine which clock really works the faster. What is that something? I ask authorities on the subject either to identify it in terms intelligible to anyone who can understand the question, or else to acknowledge that the theory is false.”
Science at the Crossroads page 55.
They aren’t you know.
What you are missing is that you have not compared the clocks when they come together. Whilst the clocks are moving relative to one another each observes the other as slower. This is not contradictory.
In order to brings the clocks together in order to compare the times on the clocks in the same reference frame you must accelerate one or both clocks. It is this acceleration that bridges the gap. One or both cease to be in an inertial frame of reference for the time needed to accelerate the clocks into the same reference frame. During that time the rates of the clocks is not one where each sees the other as slower.
For the most part this is a version of the twin paradox.
I assume your Professor Dingle intended for you to work out what the missing step is - that acceleration step, and work out for yourself how to resolve the seeming paradox.
This is one of the well know common issues with people understanding special relativity. They miss that critical point about getting back to a common reference frame. You are hardly alone in this, thousands of undergraduate physics students get caught by the same conundrum until it is pointed out to them.
Actually, Dingle’s relationship with relativity was complicated. He started off as a person who wrote popular accounts of relativity. Later, after he retired, he first claimed that relativity did not predict different ages for the twins in the “twin paradox” - but he seems to have figured out that mistake, and then moved on to the misconception that relativity is self-contradictory. In the typical fashion of cranks, he claimed to be “suppressed” after his criticisms were publicly discussed and refuted in prestigious science journals. It’s a sad story, actually. Dingle had been an accomplished scientist before this point.