DOES GPS NEED SR/GR???

Discussion in 'Pseudoscience' started by Zeno, Apr 9, 2023.

  1. Zeno Registered Senior Member

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    From what I have read the atomic clocks onboard the GPS satellites are adjusted to run 38 microseconds slower per day prior to being launched into space. After the adjustments the satellites are launched into space and the clocks stay synchronized with each other and with clocks on the ground. Since the satellites are in motion relative to each other shouldn't the clocks fall out of synch with each other due to special relativity?
     
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  3. DaveC426913 Valued Senior Member

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    Well, the paths of orbiting sats are essentially symmetrical, just out of phase over time, so any tiny discrepancy over a partial orbit is self-correcting each orbit. No clock will get ahead of or behind any other more than a few nanoseconds before it is reversed, and the effect is not cumulative.

    As for drift between ground and orbit, yes, they compensate for that in the software. Both GR and SR effects need to be accounted for.
     
    Last edited: Apr 9, 2023
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  5. TonyYuan Gravitational Fields and Gravitational Waves Registered Senior Member

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    Anyone who understands the working principle of satellite navigation system positioning knows that the current satellite navigation system uses the pseudo-range difference method to achieve positioning for ground users.
    Pseudorange means that the measured distance data also includes error items, and these errors are the same for each satellite. In practical applications, the satellite navigation system will use 4 satellites to measure 4 pseudo-ranges, and then make a difference to offset the same error term, and finally obtain the user's final positioning coordinates.

    In fact, accurate positioning is guaranteed, as long as the atomic clocks of all satellites in orbit are synchronized. This is because the more precise the time measurement, the more accurate the position calculation, given the speed at which the signal travels (the speed of light) is known. The atomic clock used by my country's Beidou has sufficient accuracy and stability, with an error of only one second in 3 million years. In addition, the ground measurement and control will perform routine secondary time-frequency corrections every day.

    In addition to achieving precise positioning, the same is true in the field of school time. The method of pseudo-range difference is also used to realize the clock synchronization of the ground user and the system time synchronization of the satellite navigation system.

    In other words, whether it is from the positioning angle of the satellite navigation system or the timing angle of the satellite navigation system, the deviation proposed in the "relativistic correction" can be eliminated through the principle of pseudo-range difference. No matter whether the relativistic effect exists or not, the existing satellite navigation system can be canceled in the process of measuring pseudo-range and difference.

    Therefore, it can be said that the "relativistic effect" of the satellite navigation system can be discussed, but the satellite navigation system does not need to make special corrections to the theory of relativity, let alone use the application of the satellite navigation system to prove or deny the theory of relativity.
     
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  7. TonyYuan Gravitational Fields and Gravitational Waves Registered Senior Member

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    Astronomer Wan Franton once worked at the US Naval Laboratory, mainly engaged in consulting work on the Global Positioning System. He once said that he discovered a dirty secret: According to Einstein's theory, moving objects produce a "time delay" effect. Therefore, the time on the GPS satellite needs to be constantly adjusted to synchronize with the users on the earth. . But that's not the case, and GPS programmers don't need relativity. "They've basically given up on Einstein," he said.

    Song Jian, academician of the Chinese Academy of Sciences and former president of the Chinese Academy of Engineering, said: "The question of whether GPS can test the existence of the shrinkage factor has caused headaches for people who develop GPS." "Current aerospace technology, whether it is rocket thrust or orbit calculation and Experiments are all based on Newtonian mechanics." "Aerospace technology has begun to abandon the technical foundation of Einstein's special theory of relativity."
     
  8. Tiassa Let us not launch the boat ... Valued Senior Member

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    Is there a technical paper on this? Presently, you're the only mention of "Wan Franton" turning up in cursory searches. And there is no other available source, right now, for what Song Jian said.

    It's kind of a thin pretense for two threads in separate subfora.

    What is the actual source for those quotes, so others might be able to review what else was said?
     
  9. TonyYuan Gravitational Fields and Gravitational Waves Registered Senior Member

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    I also looked up this astronomer. Like you, I only found his Chinese name in the official Chinese newspaper "Yangcheng Evening News". I still don't know what his English name is (Wan Franton is my translation).
     
  10. TonyYuan Gravitational Fields and Gravitational Waves Registered Senior Member

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    Here is an email from a physicist in the United States:

    My personal experience is this: I did my entire education at MIT:
    SB Physics, SM EE, PhD in Physics.
    My doctoral thesis was about using quaternion algebra in SRT.
    Then I got a job at Draper Lab, then part of the MIT Aero Dept.
    There, they were working on the Apollo program to the moon.
    Draper nobody believes in SRT. They are right!
    SRT does have one big problem.
    When I told my PhD thesis advisor, he apologized profusely!
    He suspects that physics does have some big problems.
    But he thinks at least SRT is safe!
     
    Last edited: Apr 10, 2023
  11. TonyYuan Gravitational Fields and Gravitational Waves Registered Senior Member

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    Now the hardline relativists such as Sabine Hossenfelder start to change their tone, very reluctantly though.......

    Hossenfelder in her recent video (https://www.youtube.com/watch?v=9-jIplX6Wjw) jogged a huge circle and provided tons of excuses why people have thought in relativistic ways, and finally reached with a very tiny and even hard to capture voice that SR is wrong and that was why GR was needed, and GR is wrong because it could not provide a quantum gravity......

    As one of relativity's most steadfast loyalists, she was so shy to even make this feeble voice about the problem of relativity straight.....so that she needed to borrow the Extraterrestrial Alien theory which she had openly and firmly denied.

    In this new video she supposed that Aliens are real (which was something she appeared to hate so much even not long ago) so that the speed of light must not be the upper limit....so that relativity has problem.....

    Once you watch her new video, you can sense her pain, and the pain of all the steadfast relativists......
     
  12. billvon Valued Senior Member

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    I figured eventually aliens, the Lizard People or the Illuminati would make an appearance.

    Mods, I guess we know where to move this thread to now.
     
  13. TonyYuan Gravitational Fields and Gravitational Waves Registered Senior Member

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    What are you afraid of? Hossenfelder is a famous professor of astrophysics in the United States, does her video make you feel uncomfortable?
     
  14. billvon Valued Senior Member

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    And Andrew Wakefield was a famous doctor who wrote a study claiming vaccines cause autism. Then we found out he was being paid by the defendants in a court case to say that. The defendants were suing a vaccine manufacturer. It has since become one of the most famous cases of scientific fraud of the last few decades.
     
  15. mathman Valued Senior Member

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    Latest issue of American Scientist has an article by Norwegian chemists describing how special relativity effects properties of elements - gold color, mercury liquid at room temp.
     
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  16. exchemist Valued Senior Member

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    12,370
    True, though it is something I was taught at university in the mid 1970s, so it is not news.

    Have the authors come up with any new findings or models for this, or is it just a general article about the already established science? (I might go and get a copy.

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  17. mathman Valued Senior Member

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    I am not a chemist. It seems to be a general review work from Dirac on. They refer to work involving radioactive elements.
     
  18. SalvatoreLing Registered Member

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    Yes, that is correct. Because of Einstein's special theory of relativity, which accounts for the effects associated with relativity of motion and gravity, the clocks on GPS satellites must be out of sync with each other and with the clocks on Earth. This is because the satellites orbit the Earth at a significant rate and time flows slower on board the satellite than it does on the Earth's surface. Also, because of the Earth's gravitational field, time on board a satellite flows faster than on the surface of the Earth. However, the clocks on the GPS satellites are adjusted and corrected to account for these effects and to maintain synchronization with the clocks on Earth.
     
  19. billvon Valued Senior Member

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    Relative motion - no, since they see just as much motion towards them as away from them (they are all prograde orbits.)
    Ellipiticity - sort of. As they rise in orbit the error gets worse (flatter space) but the error correction already takes that into account.
    Orbital adjustments - yes, this causes minor changes
    Mascons (mass concentrations within the Earth) - yes, but again all satellites see a similar mass profile since they are all orbiting the same planet
     
    Last edited: Apr 12, 2023
  20. billvon Valued Senior Member

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    Nope. Not a time delay; a change in the rate of time flow between two frames that are moving relative to each other. Sounds like Wan Franton doesn't understand relativity.
    Nope. That correction is built in, so no constant adjustments are needed.
    GPS programmers took relativity into account. Specifically, special relativity is a factor because the satellites are moving relative to the ground. That means that, each day, the satellite's clock sees a -7.2us error. And general relativity is also a factor, since the satellites are much farther from Earth's gravity well, and are in flatter space. This causes an error of +45.8 μs per day. The total error is therefore 38.6 us a day. Fortunately scientists understood this, and built in a 38.6 us per day correction - so the resulting time reference is accurate. In practical terms, the satellite's time base is set to 10.22999999543 MHz before launch instead of 10.23 MHz, thus accounting for errors caued by both SR and GR.

    If GPS had not been adjusted for relativity, it's accuracy would have so degraded it would be effectively useless.
     
  21. TonyYuan Gravitational Fields and Gravitational Waves Registered Senior Member

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    GPS seems to be produced by your family.

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  22. billvon Valued Senior Member

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    Nope. Just an engineer who has worked with it - a lot.
     
  23. exchemist Valued Senior Member

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    OK thanks. Do you have the title of the article? I've had a look online and can't find it.

    I'd like to read it, as the rather superficial treatments of this I am familiar with talk in terms of "relativistic mass". Presumably that is to enable the standard Schrödinger equation to be used with a simple correction, but it is a concept that makes modern physicists wince, so I'd like to see if they explain it without resorting to that.
     

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