Is Relativity 100% proven to all professional scientists satisfaction?

[Hazel M]

By receivers swansont means the equipment on the ground, not the actual people using the GPS.

 

The physics of GPS is sound and relies on relativity. This is quite independent of the your actual GPS machine in your hand always working.

Well, you didn't mean to do it but you've filled my head with another whole new puzzle. Are you saying that the GPS system "senses/knows" where these streets are and directs the driver from that using relativity? Are you saying information is not programmed into them by human beings? I won't even ask how relativity relates to GPS. Not today. Will say that other drivers with different brands or updated receivers were not getting these errors. And there were more than just the one I described.

[Ophiolite]

That's right. If there is an error it is an error of manufacture of operation, not of theory. That is the point the others are making. GPS works fine if the equipment is sound.

 

I'm not quite sure why you think GPS is a huge mistake. It is of great value in many ways. Did you have something specific in mind?

[Nicholas Kang]

Indeed - the fault is almost certainly with the receivers. The GPS signals are there (and robust from that viewpoint) but signals are somewhat easily lost or scrambled once they get to earth.

Who created cheap navigation system? Again, it is we, human. If there is nothing wrong with GPS, then why blaming on the receivers?

Receivers carry 2 meanings

1. We, human who use GPS

2. The receiver installed in your car

 

1. Why blaming on receivers-we, human. All of the members on SFN are human, so you are actually blaming yourself

2. This is the problem of poor advancement in technology, blame yourself if this was right.

[imatfaal]

Well, you didn't mean to do it but you've filled my head with another whole new puzzle. Are you saying that the GPS system "senses/knows" where these streets are and directs the driver from that using relativity? Are you saying information is not programmed into them by human beings? I won't even ask how relativity relates to GPS. Not today. Will say that other drivers with different brands or updated receivers were not getting these errors. And there were more than just the one I described.

 

Not really no. The GPS system uses timing from satellites to work out where it is (simplish trigonometry) and the computer chip attached as the other part of your GPS takes this position and looks at the maps installed by the producer or user and works out which street you are on.

[Hazel M]

That's right. If there is an error it is an error of manufacture of operation, not of theory. That is the point the others are making. GPS works fine if the equipment is sound.

 

I'm not quite sure why you think GPS is a huge mistake. It is of great value in many ways. Did you have something specific in mind?

I'm not sure to whom you are directing this question but I assure you I did not say - and do not believe - GPS is a mistake. I only said it doesn't always work right. As someone else said, perhaps the driver had cheap, unreliable equipment but it doesn't always work right. In other words, when we use our inventions, we need to stay in control. Right?

[swansont]

Whoever set up that particular system simply failed to learn that the street dead ends due a highway whizzing by. Nothing wrong with the system at all other than failure to check a map or take a walk around the neighborhood.

 

Am I wrong?

 

That's entirely the fault of the receiver's software and maps. Not with the GPS satellites, which simply broadcast timing and diagnostic signals. Anything not having to do with your current coordinates is definitely not an issue with satellite end of GPS.

[Ophiolite]

Most GPS works well most of the time. Of course the small number of failures of the material part of the system are ultimately a consequence of sub standard human actions: poor design, poor manufacturing, poor operation. So, in that respect you are correct, ultimately it is a human error, but that is irrelevant to the point in hand:

 

What is the source of failures in GPS? Is it the theory, or is it the equipment?

 

Answer: it is the equipment. (And it is unnecessary and irrelevant to point out that the equipment failed because of human error.)

I'm not sure to whom you are directing this question but I assure you I did not say - and do not believe - GPS is a mistake. I only said it doesn't always work right. As someone else said, perhaps the driver had cheap, unreliable equipment but it doesn't always work right. In other words, when we use our inventions, we need to stay in control. Right?

Sorry - this is a very active thread right now. I posted a direct response to Nicholas, but one or two posts got made while I was preparing it. I'm in general agreement with what you have said throughout.

[Nicholas Kang]

You mean human errors are negligible?

What do you mean by failures in GPS? Poor communication?

 

GPS are not wrong. They are designed to apllicate GR to prevent gravitational time dilation. GR or the theory benefits human. If they were wrong, they can`t benefit human and why should we use GPS then?

[swansont]

Who created cheap navigation system? Again, it is we, human. If there is nothing wrong with GPS, then why blaming on the receivers?

Receivers carry 2 meanings

1. We, human who use GPS

2. The receiver installed in your car

 

1. Why blaming on receivers-we, human. All of the members on SFN are human, so you are actually blaming yourself

2. This is the problem of poor advancement in technology, blame yourself if this was right.

 

The satellites aren't exactly cheap — it's a multi-billion dollar system, with millions more spent on upkeep every year. If you aren't being routed properly, or its indicated you're in the middle of a river instead of a kilometer away, that's an issue with the device in your car or being held in your hand, commonly referred to as the GPS receiver. These devices can be cheap.

 

I have nothing to do with the choice an individual makes in buying a GPS receiver or the manufacture thereof, the mapping data being used, or the algorithms used for routing people, so I reject your sentiment of blame.

[Hazel M]

Not really no. The GPS system uses timing from satellites to work out where it is (simplish trigonometry) and the computer chip attached as the other part of your GPS takes this position and looks at the maps installed by the producer or user and works out which street you are on.

Thank you. I am getting ready to go out. I'll have to come back to cogitate this. Meanwhile, what kind of error is this? In Kansas City - I think it was KC - I often rode a bus that used GPS. Well, all their busses did. But this particular bus's GPS was always off by about ten blocks. It lagged that much. When we were at our destination, it had us still back a long way from said destination.

 

Meanwhile, I like your explanation. I was forgetting those satellites. I think that explains why, when a driver goes too fast and passes a street before the system tells him to turn there immediately gets a correction from his GPS. "You missed that; let's try this." Thank you.

[Nicholas Kang]

Sorry for jumping the queue.

[imatfaal]

The relativity bit comes from the fact that the GPS Satellites have an atomic clock on board - this enables the timings to be good and the receivers to make an accurate trigonometrical calculation of its separation from a number of satellites and thus its position on the earth. However it was predicted in relativity that clocks in frames with a relative velocity will be seen from the observers rest frame as running slowly. It is also predicted by general relativity that clocks at a higher gravitational potential will run faster.

 

If we just ignored these predictions from relativity our GPS would not work - even the most accurate system would give incorrect answers. So we must adjust for two influences of the fact that the satellite is both in relative velocity with respect to the GPS receiver, and is at a higher gravitational potential. Special Relativity tells us, through simple sums, that the clocks on the GPS-Sats will run slower than earth bound by 7200 nano-seconds per day due to relative velocity . General Relativity tells us that the clocks on the GPS-Sats will run faster than earth bound by 45,900 nano-seconds per day. The net result is that we need to correct by 38,700 nano-seconds per day. We do this and the system works.

 

This is what we mean by saying that GPS provides evidence to support relativity.

[Nicholas Kang]

 

The satellites aren't exactly cheap — it's a multi-billion dollar system, with millions more spent on upkeep every year. If you aren't being routed properly, or its indicated you're in the middle of a river instead of a kilometer away, that's an issue with the device in your car or being held in your hand, commonly referred to as the GPS receiver. These devices can be cheap.

 

I have nothing to do with the choice an individual makes in buying a GPS receiver or the manufacture thereof, the mapping data being used, or the algorithms used for routing people, so I reject your sentiment of blame.

Sorry for misunderstanding. So, what are the failures of GPS? Are you discussing about who is responsible to be blamed on the GPS failures? Or about proving Relativity?

Edited June 26, 2014 by Nicholas Kang

[Hazel M]

The relativity bit comes from the fact that the GPS Satellites have an atomic clock on board - this enables the timings to be good and the receivers to make an accurate trigonometrical calculation of its separation from a number of satellites and thus its position on the earth. However it was predicted in relativity that clocks in frames with a relative velocity will be seen from the observers rest frame as running slowly. It is also predicted by general relativity that clocks at a higher gravitational potential will run faster.

 

If we just ignored these predictions from relativity our GPS would not work - even the most accurate system would give incorrect answers. So we must adjust for two influences of the fact that the satellite is both in relative velocity with respect to the GPS receiver, and is at a higher gravitational potential. Special Relativity tells us, through simple sums, that the clocks on the GPS-Sats will run slower than earth bound by 7200 nano-seconds per day due to relative velocity . General Relativity tells us that the clocks on the GPS-Sats will run faster than earth bound by 45,900 nano-seconds per day. The net result is that we need to correct by 38,700 nano-seconds per day. We do this and the system works.

 

This is what we mean by saying that GPS provides evidence to support relativity.

I've read that about the clocks. One on a higher floor of a very tall building will run faster. and that I understand because I understand gravity. Score one for my poor brain.

 

I have an old book in my library called "How everything works". It was great back when. I need a new one.

 

No problem about queue, Nicholas Kang. As was said, it's busy thread right now. I shall return to a good story I am sure.

[xyzt]

The relativity bit comes from the fact that the GPS Satellites have an atomic clock on board - this enables the timings to be good and the receivers to make an accurate trigonometrical calculation of its separation from a number of satellites and thus its position on the earth. However it was predicted in relativity that clocks in frames with a relative velocity will be seen from the observers rest frame as running slowly. It is also predicted by general relativity that clocks at a higher gravitational potential will run faster.

 

If we just ignored these predictions from relativity our GPS would not work - even the most accurate system would give incorrect answers. So we must adjust for two influences of the fact that the satellite is both in relative velocity with respect to the GPS receiver, and is at a higher gravitational potential. Special Relativity tells us, through simple sums, that the clocks on the GPS-Sats will run slower than earth bound by 7200 nano-seconds per day due to relative velocity . General Relativity tells us that the clocks on the GPS-Sats will run faster than earth bound by 45,900 nano-seconds per day. The net result is that we need to correct by 38,700 nano-seconds per day. We do this and the system works.

 

This is what we mean by saying that GPS provides evidence to support relativity.

To be exact, the difference in clock frequency is derived directly from the Schwarzschild solution to the EFE:

 

 

[math]\displaystyle \frac{f_1}{f_2}= \sqrt{\frac{1-r_s/r_2-\frac{(v_2/c)^2}{1-r_s/r_2}-(\frac{r_2 \omega_2}{c})^2}{1-r_s/r_1-\frac{(v_1/c)^2}{1-r_s/r_1}-(\frac{r_1 \omega_1}{c})^2}}[/math]

 

where the difference in frequency comes from:

 

1. gravitational potential difference , via the term in [math]\frac{r_s}{r_i}[/math]

2. radial speed difference (if it exists), via the term in [math]v_i[/math] (the sat trajectories are not circular)

3. angular speed difference, via the term in [math]r_i \omega_i[/math]

 

Traditionally, people say that there is an "SR component" and a "GR component" to the explanation. In reality, the whole explanation is purely GR.

Edited June 26, 2014 by xyzt

[Nicholas Kang]

I've read that about the clocks. One on a higher floor of a very tall building will run faster. and that I understand because I understand gravity. Score one for my poor brain.

 

I have an old book in my library called "How everything works". It was great back when. I need a new one.

 

I have read the same topic on Ira Mark Egdall`s Einstein Relatively Simple too. I don`t think I am lack of knowledge with gravity, though I should learn more about it.

[swansont]

Sorry for misunderstanding. So, what are the failures of GPS? Are you discussing about who is responsible to be blamed on the GPS failures? Or about proving Relativity?

 

I'm narrowing the source of the problem when someone's GPS unit gives them a bad indication. It's not the satellite, it's not relativity. "GPS doesn't work" is an issue of some sort with the receiver you possess.

[Hazel M]

I'm narrowing the source of the problem when someone's GPS unit gives them a bad indication. It's not the satellite, it's not relativity. "GPS doesn't work" is an issue of some sort with the receiver you possess.

Actually, swansont, it's a smiley comment grown big. Someone had used GPS as an example of something long forgotten and I smilingly wrote "GPS doesn't always work either" or some such. The rest is history but I'm enjoying it. I'd never given any thought as to how GPS works. Certainly didn't know that it involved relativity. Gee! Does everything?

[Strange]

Actually, swansont, it's a smiley comment grown big. Someone had used GPS as an example of something long forgotten and I smilingly wrote "GPS doesn't always work either" or some such. The rest is history but I'm enjoying it. I'd never given any thought as to how GPS works. Certainly didn't know that it involved relativity. Gee! Does everything?

 

Everything electronic depends on special relativity (the bit without gravity) as that is a part of quantum field theory and we use that to design semiconductor materials and devices.

 

(One of the challenges for GPS receivers is being able to receive a good signal from 4 or more satellites, particularly in urban areas where buildings can block signals or cause reflections. The radio signal at the receiver is lower than the background noise, so the receiver has to do a bit of searching to find them. )

[Hazel M]

Not really no. The GPS system uses timing from satellites to work out where it is (simplish trigonometry) and the computer chip attached as the other part of your GPS takes this position and looks at the maps installed by the producer or user and works out which street you are on.

This is what I wanted to come back to. If I am reading rightly, the only "programming" into the system done by a human is putting in maps? Then, if GPS takes wrong streets, the map has a mistake on it. Am I right? It isn't a big deal,I am sure but the fact is that all good (stress good) maps have mistakes on them - deliberate errors. The purpose being to prevent stealing of another company's map. It has been a long while since I read about this but the example given was an alleged town along a county road in Kansas. There is no town there. It was planted by the original map maker.

 

OK. GPS reads this map and coordinates its instructions based on that information plus the coordinates it reads via the satellite. Please tell me I have that right.

[swansont]

Satellites beam the information. The receiver does a fairly simple calculation and gets your position. Owing to experimental uncertainty, this is never going to be perfect, but is usually good to several meters.

 

Anything involving a map or directions is in the hands of the company who made the device.

 

I've read about the phantom towns used to prevent copying of maps. These days I'm guessing they would use steganography to encode a digital fingerprint to prove copying, rather than have a deliberate error in a map, which might lead to bad press.

[Hazel M]

Satellites beam the information. The receiver does a fairly simple calculation and gets your position. Owing to experimental uncertainty, this is never going to be perfect, but is usually good to several meters.

 

Anything involving a map or directions is in the hands of the company who made the device.

 

I've read about the phantom towns used to prevent copying of maps. These days I'm guessing they would use steganography to encode a digital fingerprint to prove copying, rather than have a deliberate error in a map, which might lead to bad press.

Stenography! "Word a Day". Wonder if that is what is messing up my emails. Hidden messages.

[studiot]

No, offence Hazel, but check the spelling in your post against swansont's

 

steganography

 

Stenography!

 

As to GPS, I'm surprised no one has mentioned that it is not possible to perfectly match 3D space coordinates, as used by satellites to the surface of the Earth, on a flat 2D map. This has to to with ordinary geometry and nothing to do with relativity.

Also transmission to the receiver is not perfectly known, and affected by conditions and the terrain. We used to call this 'ground swing' in the old days. You can find lots about it on google.

 

[Strange]

This is what I wanted to come back to. If I am reading rightly, the only "programming" into the system done by a human is putting in maps? Then, if GPS takes wrong streets, the map has a mistake on it. Am I right?

 

Errors in the map are one source of problems. The other is "meta information" about the streets: one way streets, narrow roads unsuitable for heavy vehicles, rough roads unsuitable for any vehicles, etc. Another problem is the route finding algorithms; how the system works out the best route from A to B. I have seen comparative reviews of GPS receivers which produce wildly different routes - sometimes just varying by a few miles, but in one case adding thousands of miles to the journey!

[Hazel M]

No, offence Hazel, but check the spelling in your post against swansont's

 

steganography

 

Stenography!

 

As to GPS, I'm surprised no one has mentioned that it is not possible to perfectly match 3D space coordinates, as used by satellites to the surface of the Earth, on a flat 2D map. This has to to with ordinary geometry and nothing to do with relativity.

Also transmission to the receiver is not perfectly known, and affected by conditions and the terrain. We used to call this 'ground swing' in the old days. You can find lots about it on google.

 

Oops! I was pronouncing it right. Guess I didn't check carefully. Haste made waste. Thanks.

 

GPS. At least it isn't as much of a mystery to me as some things. So much new has sprung up in the last forty/fifty years. Hard to keep up. Steganography.

Errors in the map are one source of problems. The other is "meta information" about the streets: one way streets, narrow roads unsuitable for heavy vehicles, rough roads unsuitable for any vehicles, etc. Another problem is the route finding algorithms; how the system works out the best route from A to B. I have seen comparative reviews of GPS receivers which produce wildly different routes - sometimes just varying by a few miles, but in one case adding thousands of miles to the journey!

What you call "meta information" would definitely be extra information that someone would need to program in, wouldn't it? That's what I was asking about earlier. Isn't some of this a matter of programming the GPS correctly. I recently read about a steep road that goes up a small mountain into a town in Wales. The road is barely wide enough for one-way traffic. The natives all know about it and take care but GPS does not give that information. There had been a few bad accidents caused by uninformed drivers relying on their GPS system. So, yes, "meta information" bears watching. Do the better systems have such information programmed in? It would take constant updating. "Road construction on route 77"?

 

Wildly different routes? Maybe some are measuring distance in time instead of miles or kilometers? I know you know the many people who now measure distance in time. Ask them how far something is and they'll say "Oh, about five minutes" or "Just two hours". Now, there's theory of relativity that I understand.

 

Anyway, on that point - get the math right? Maybe I am wrong but I'm still taking most of those errors back to a human who has to do some programming. GPS is a "computer", isn't it? It has to be programmed to do the job the right way. And the programming is more than just installing a map? Yes?