GPS positioning systems.

[Bender]

 

I asked strange a question ref time dilation above, with reference to geostationary satellites and ground based clocks, also ground based clocks compared to those falling directly down in free fall towards a ground based clock. Do you have any thoughts or links that could cast light on this. I suspect that time dilation might speed up under these circumstances compared to the ground based clock.

It depends on how fast it is falling and how high it is. The time dilatation originating from the height can be found in the graph, since it is independent of the speed.

[swansont]

I am sure there is a thread somewhere discussing quantum entanglement in the speculation bin.

What you want is a thread in the physics section, so that there is no speculation to lead you astray.

 

I asked strange a question ref time dilation above, with reference to geostationary satellites and ground based clocks, also ground based clocks compared to those falling directly down in free fall towards a ground based clock. Do you have any thoughts or links that could cast light on this. I suspect that time dilation might speed up under these circumstances compared to the ground based clock.

Gravity probe A.

https://en.wikipedia.org/wiki/Gravity_Probe_A

 

(spoiler: it confirmed relativity)

[Handy andy]

What you want is a thread in the physics section, so that there is no speculation to lead you astray.

 

 

Gravity probe A.

https://en.wikipedia.org/wiki/Gravity_Probe_A

 

(spoiler: it confirmed relativity)

I keep getting posts from various physics forums which claim their latest findings(I think often for funding and advertisement purposes) and then go quite when they find they have made a blunder, or cant repeat their findings. I think a lot of it is speculative but is interesting to read.

 

Thanks for the link Gravity Probe A, from what I understood, I think it confirms what am thinking. Time as measured by accurate clocks can run faster in high geo stationery orbits and in free fall towards the earth, than it does on a stationery clock on earth.

 

Time measured on clocks when moving at speed against gravity or in parallel to it runs slower.

 

I am correct in saying, Gravity slows down the measured time, and in the absence of gravity or in free fall time appears to run faster, because the clocks are not affected by gravity so much?.

 

When satellites are redirected to different parts of the planet at different latitudes does this also affect the clocks slightly, as may gravitational anomalies and mountain ranges and the moon.

 

ref quantum entanglement it is not part of this thread but here is a link that is not relevant to this thread which is nearly easy reading for those that are interested. https://simple.wikipedia.org/wiki/Quantum_entanglement.

Edited May 9, 2017 by Handy andy

[Bender]

I am correct in saying, Gravity slows down the measured time, in the absence of gravity or in free fall time appears to run faster, because the clocks are not affected by gravity so much.

Yes for the gravity part. Whether or not you are in free fall has no influence.

[Handy andy]

Yes for the gravity part. Whether or not you are in free fall has no influence.

 

https://en.wikipedia...Gravity_Probe_A

 

IF I read the above link correctly, moving in the direction of the gravity well speeds up time measured on a clock. In free fall you are headed in the right direction, until you reach ground zero (splat)

[swansont]

https://en.wikipedia...Gravity_Probe_A

 

IF I read the above link correctly, moving in the direction of the gravity well speeds up time measured on a clock. In free fall you are headed in the right direction, until you reach ground zero (splat)

You are not reading it correctly, then. Being higher in a gravitational potential well is what speeds up clocks.

[Handy andy]

You are not reading it correctly, then. Being higher in a gravitational potential well is what speeds up clocks.

 

Yes I re read the link last night again. Thanks for that. How is the clock affected as it descends into the gravitational potential well?, I think this depends on the speed of descent, initially it will be going faster than the clock in the ground position, as it goes deeper into the gravitational potential well, how much does the clocks speed change with reference to the clock on the ground.

 

I had another thought around the question I was trying to ask ref clocks at the other side of the universe, which backfired.

Rather than using an analogy with wormholes. If two identical spaceships were to approach a central point between them at equal speed and acceleration through uniform none stretched space, the clocks on the space ships would read identical elapsed times when they reached the central point. Since they were travelling through space the clocks elapsed times will go slower than the stationery clock at the mid point. If the experiment is repeated with the midpoint being a potential well, time will again be slowed as the clocks approach the mid point in the potential well, if they turn around and accelerate against the potential well back to their respective starting point, at the same speed and acceleration will the elapsed times be longer on the return journey or less.

[swansont]

 

Yes I re read the link last night again. Thanks for that. How is the clock affected as it descends into the gravitational potential well?, I think this depends on the speed of descent, initially it will be going faster than the clock in the ground position, as it goes deeper into the gravitational potential well, how much does the clocks speed change with reference to the clock on the ground.

 

 

It depends on ø/c^2, where ø is v^2/2 for motion and GM/r for gravitation (near the surface of the earth the difference in potential is approximately gh)

[Handy andy]

From above

 

 

If two identical spaceships were to approach a central point between them at equal speed and acceleration through uniform none stretched space, the clocks on the space ships would read identical elapsed times when they reached the central point. If they did a return journey to their respective starting points at the same speed and acceleration, The outgoing journey elapsed times would equal the incoming journey elapsed times.

 

If the experiment is repeated with the midpoint being a potential well, time will again be slowed as the clocks approach the mid point in the potential well, if they turn around and accelerate against the potential well back to their respective starting point, at the same speed and acceleration will the elapsed times be longer on the return journey or less. ?

 

The question above is to try and establish if space is flowing into a gravity well or is stationery.? It affects how the stretching of space causes gravity.

................................................................................................................

The question below, is a separate question, but again related to time dilation, and is a question of understanding or definition of what time dilation is caused by.

 

Photons of light create a gravitational disturbance

 

Photons of light compress the space in front of them and stretch it behind them causing waves, the double slit experiment works with both electrons and photons, the effect in space is therefore the same. The track of photons in a gravitational field is bent by gravity (the stretching of space) An electron orbiting an atom in a radioactive clock will be affected by its movement in a gravitational field. Can time displacement not more correctly be explained by instrumentation error. If not why not?

 

Is time dilation and time travel not like the kings new clothes.

Edited May 11, 2017 by Handy andy

[swansont]

 

The question above is to try and establish if space is flowing into a gravity well or is stationery.?

 

 

Neither. Space is not a substance (and is certainly not made of paper)

[Handy andy]

 

 

Neither. Space is not a substance (and is certainly not made of paper)

 

How can the answer be neither,?

 

My first questions were

 

"If two identical spaceships were to approach a central point between them at equal speed and acceleration through uniform none stretched space, the clocks on the space ships would read identical elapsed times when they reached the central point. If they did a return journey to their respective starting points at the same speed and acceleration, The outgoing journey elapsed times would equal the incoming journey elapsed times.

 

If the experiment is repeated with the midpoint being a potential well, time will again be slowed as the clocks approach the mid point in the potential well, if they turn around and accelerate against the potential well back to their respective starting point, at the same speed and acceleration will the elapsed times be longer on the return journey or less. ?

"

[swansont]

 

How can the answer be neither,?

 

My first questions were

 

"If two identical spaceships were to approach a central point between them at equal speed and acceleration through uniform none stretched space, the clocks on the space ships would read identical elapsed times when they reached the central point. If they did a return journey to their respective starting points at the same speed and acceleration, The outgoing journey elapsed times would equal the incoming journey elapsed times.

 

If the experiment is repeated with the midpoint being a potential well, time will again be slowed as the clocks approach the mid point in the potential well, if they turn around and accelerate against the potential well back to their respective starting point, at the same speed and acceleration will the elapsed times be longer on the return journey or less. ?

"

 

 

 

The question I was answering is whether "space is flowing into a gravity well or is stationery"

 

Space is not a substance. It does not flow. Stationery is writing paper.

 

What does this have to do with GPS, anyway?

[Strange]

 

How can the answer be neither,?

 

 

If the question involves a category error. For example: "Is love green or banana-flovoured?"

[Handy andy]

 

 

 

The question I was answering is whether "space is flowing into a gravity well or is stationery"

 

Space is not a substance. It does not flow. Stationery is writing paper.

 

What does this have to do with GPS, anyway?

 

What I am getting at is, does the direction travelled up or down into a gravity well affect the time dilation more in one direction than the other.

 

I am trying to understand exactly how the time on satellite clocks is affected by gravity, before moving the thread onto, such things as how does the atmosphere affect propagation delays or how the ionosphere affect the accuracy of GPS.

 

I have been lead to believe that time dilation is massively significant when looking at the accuracy of GPS. If it wasn't taken into account the GPS would not work, as well as it does today.

[Strange]

 

What I am getting at is, does the direction travelled up or down into a gravity well affect the time dilation more in one direction than the other.

 

 

It is purely a function of the difference in gravitational potential. So it doesn't matter how you got there.

[swansont]

What I am getting at is, does the direction travelled up or down into a gravity well affect the time dilation more in one direction than the other.

No. As I've stated already, the effect is only a function of the position in the well. The Pound-Rebka type experiments confirm this.

 

 

I am trying to understand exactly how the time on satellite clocks is affected by gravity, before moving the thread onto, such things as how does the atmosphere affect propagation delays or how the ionosphere affect the accuracy of GPS.

 

I have been lead to believe that time dilation is massively significant when looking at the accuracy of GPS. If it wasn't taken into account the GPS would not work, as well as it does today.

That's true. But we're talking about the end result here. If you have questions on the underlying physics, it should be in a new thread. If you are going to propose anything like an aether ("flow of space") then you'd better do it in speculations and be prepared to justify your contention.

[Handy andy]

No. As I've stated already, the effect is only a function of the position in the well. The Pound-Rebka type experiments confirm this.

 

 

 

That's true. But we're talking about the end result here. If you have questions on the underlying physics, it should be in a new thread. If you are going to propose anything like an aether ("flow of space") then you'd better do it in speculations and be prepared to justify your contention.

 

Thanks for the reply, I will study the Pound-Rebka experiments.

 

I started this thread under Engineering a legitimate subject because I am staying away from speculating.

 

I did not know threads could be started under speculation.

No. As I've stated already, the effect is only a function of the position in the well. The Pound-Rebka type experiments confirm this.

 

 

 

The below is one of many links I followed on Pound-Rebka experiment it does not confirm your assertion. There are many interpretations of the same experiment, your assertion above I think is unfounded. An object travelling into the well will experience shorter time dilation effects than an object travelling out of the well.

 

http://www.circlon-theory.com/HTML/poundRebka.html

 

As a photon goes into a gravity well it increases its energy and as it leaves it loses energy, its frequency therefore increases as it goes in and decreases as it comes out, blue and red shift. The amount of time measured for the return journey out of the gravity well will be more than the journey to the gravity well.

 

I will keep trawling the pound-rebka experiment web sites to see if any web site agrees fully with your assertion, at the current moment I have found none, do you have a link that agrees with your assertion?

Edited May 11, 2017 by Handy andy

[Strange]

The below is one of many links I followed on Pound-Rebka experiment it does not confirm your assertion.

 

 

You really need to learn how to judge the quality of your sources. If you are trying to learn, it is generally not a good idea to get your information from sites like that.

 

Wikipedia has a good page on the experiment with references to good sources.

[Handy andy]

 

 

You really need to learn how to judge the quality of your sources. If you are trying to learn, it is generally not a good idea to get your information from sites like that.

 

Wikipedia has a good page on the experiment with references to good sources.

 

One of the many problems with the internet is any one can publish crap and state it as fact, even reputable science websites and universities claim discoveries or predictions that cant be verified and subsequently turn out to be nonsense. If presented with a thousand books which are all wrong and we read them all, we learn nothing, unless we question what is written. People who don't question everything in science might as well follow religion.

 

Wikipedia is not full proof either but which Wiki link would you suggest.

Edited May 11, 2017 by Handy andy

[John Cuthber]

 

One of the many problems with the internet is any one can publish crap and state it as fact, even reputable science websites and universities claim discoveries or predictions that cant be verified and subsequently turn out to be nonsense. If presented with a thousand books which are all wrong and we read them all, we learn nothing, unless we question what is written. People who don't question everything in science might as well follow religion.

 

Wikipedia is not full proof either but which Wiki link would you suggest.

Wiki is generally very good. Mistakes there usually get corrected quickly.

The remarkably obvious place to start is here

https://en.wikipedia.org/wiki/Pound%E2%80%93Rebka_experiment

[Handy andy]

 

 

You really need to learn how to judge the quality of your sources. If you are trying to learn, it is generally not a good idea to get your information from sites like that.

 

Wikipedia has a good page on the experiment with references to good sources.

https://en.wikipedia.org/wiki/Pound%E2%80%93Rebka_experiment

 

The pound rebka experiment, confirms general relativity at different levels in a gravitational well and it confirms a red shift going into the gravity well and therefore a blue shift coming back out. Red in Blue out not GIGO. The time dilation on the return journey of the experiment I mentioned above will be smaller.

 

Wiki is generally very good. Mistakes there usually get corrected quickly.

The remarkably obvious place to start is here

https://en.wikipedia.org/wiki/Pound%E2%80%93Rebka_experiment

I was posting my reply as you posted

 

Edit: Red in Blue out

 

Got it thanks all.

How does the earths atmospheric changes affect the GPS accuracy with reference to propagation delays in particular through the ionosphere, and through humid and dry environments.

 

I found this on wikipedia, https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System

 

Does altitude or latitude affect GPS accuracy.

Edited May 12, 2017 by Handy andy

[Strange]

 

How does the earths atmospheric changes affect the GPS accuracy with reference to propagation delays in particular through the ionosphere, and through humid and dry environments.

 

I found this on wikipedia, https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System

 

That seems to answer your questions! (I might bookmark that one. I just realised that it is 20 years since I worked on GPS systems...)

 

 

Does altitude or latitude affect GPS accuracy.

 

It may need to be taken into account (altitude, at least) because it changes the relative gravitational time dilation. But shouldn't affect accuracy.

[swansont]

 

How does the earths atmospheric changes affect the GPS accuracy with reference to propagation delays in particular through the ionosphere, and through humid and dry environments.

 

 

Ionosphere delays can be measured and compensated for if you have two frequencies at your disposal, since there is dispersion (the effect depends on frequency). It's the troposphere that has to be approximated.

[Handy andy]

 

Ionosphere delays can be measured and compensated for if you have two frequencies at your disposal, since there is dispersion (the effect depends on frequency). It's the troposphere that has to be approximated.

 

What is the complete mechanism behind the ionisation of atoms in both the ionosphere and troposphere, which leads to loss or reduction of signal strength.

 

Gamma Rays UV rays etc knock electrons off atoms, the electrons in the atoms only transition when they have enough energy to go to the next energy level. The atoms also absorb energy in the form of kinetic energy. When GPS signals are transmitted through the troposphere and ionisation layers, signals are absorbed more easily than through air at higher atmospheric pressure at lower altitudes, is this because some of the kinetic energy of the atoms adds with the energy of the gps signal giving the atoms enough energy to transition to the next energy level.

 

Why does none ionized air at normal atmospheric pressure not absorb GPS signals as much as ionized air at lower atmospheric pressure. Is there differentmixes of gases at higher altitude..

 

Which gases in the atmosphere ionize more easily. Would concentrations of radon gas block GPS signals due to its radio active nature.

 

 

That seems to answer your questions! (I might bookmark that one. I just realised that it is 20 years since I worked on GPS systems...)

 

 

It may need to be taken into account (altitude, at least) because it changes the relative gravitational time dilation. But shouldn't affect accuracy.

 

I thought some one around here new about GPS, was DGPS around 20 years ago, I cant remember.

Edited May 13, 2017 by Handy andy

[swansont]

When GPS signals are transmitted through the troposphere and ionisation layers, signals are absorbed more easily than through air at higher atmospheric pressure at lower altitudes, is this because some of the kinetic energy of the atoms adds with the energy of the gps signal giving the atoms enough energy to transition to the next energy level.

 

 

 

The troposphere is the lowest layer, at the lowest altitude and highest pressure.