## 2 clocks on a single satelite

Hello here is small question:
Lets say we have 2 clocks on spacecraft.
Both are synchronized with Earth clock before start.

Lets synchronize one of them with Earth clock again when they arrive to an orbit.

Do relativity predict some faze diference for these two clocks now?
If so how big?
Thanks.

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 Recognitions: Gold Member Are you aware that there is no such thing as an Earth clock? Clocks on the surface of the Earth in different locations will tick at different rates, just like clocks in different orbits will tick at different rates. The differences are extremely small but can be measured with today's technology. That's why GPS was invented, just so that we could all synchronize not only the rates of our clocks, but the times on them. A practical way to perform your experiment would be to compare the tick rates of different precision clocks at different locations on the surface of Earth and in orbit to the tick rate provided by GPS. But the answers will depend on the specifics which you haven't provided.

 Quote by Alvydas Do relativity predict some faze diference for these two clocks now? If so how big? Thanks.
Yes, GR predicts a de-synchronization dependent on the length (and the path) of the rocket. The simplest case is the one where the rocket is moving radially away from the Earth.

## 2 clocks on a single satelite

Tank You for the answer. I will try to clear my question with more details.
Let at the begining all 3 clocks are at one point A on the Earth.
All them goes the same.
Then let say during some sort time (some minutes) 2 of them together go to an orbit.
Let say 100 km up.
Then with radio telescope from the same starting point A we additionally synchronize one of mentioned clocks in space.

By saying synchronize I mean only phase adjustment, without effecting clocks rate.
So both clocks on satelite will tick with the same rate anyway.
But what about phase. Maybe synchronization itself will effect phase a little?

If some very very little phase shift still occurs maybe you can estimate what order it can be at 100km orbit for example.

We may even think that there is no gravitational time delay for simplicity.
Just how synchronization of phase will effect (or will not) one of these clocks.

 Mentor The difference between the two satellite clocks just comes from the rocket launch then - some parts from special relativity (the rocket moves relative to the ground) and some from general relativity (height difference to the surface). Note that for clocks orbiting the earth, there is no way to synchronize it with clocks on the ground in a meaningful, symmetric way. You have to define a reference system where you do this.
 Here is a little why I have asked this question: Lets say (just lets say for a moment) that speed of light is not constant. Lets say it is c-10km/s upward direction and c+10km/s downward direction (near the Earth). The question is what experiments may detect or reject this assumption? But please don't say just GPS. Most say it would be notable at GPS. But when I asking them to paint some simple draft/scheme with a few radio-wave (or light) emitters, receivers and clocks how it could look to test such asumtion nobody can do it. Thats is very strange. Maybe you can help to visualize simplest realistic experiment setup to test assumption I have mentioned. Maybe it would be interesting for other people also and would save a lot of my time. Thank you.

 Quote by Alvydas Here is a little why I have asked this question: Lets say (just lets say for a moment) that speed of light is not constant. Lets say it is c-10km/s upward direction and c+10km/s downward direction (near the Earth). .
There are many tests that falsify your assumption. See here.

 Mentor You would have to define what you mean by a different speed of light first. In SI units, the speed of light is constant by definition (the length of a meter is the distance light travels in 1/299792458 s). In other words, a "different speed of light" would be equivalent to a different length of a ruler. Which can be measured.

 Quote by GAsahi There are many tests that falsify your assumption. See here.
Tank you. Maybe you can recommend one or two the best most sutable the case I was asking?
Really would take much time to study deeply them all.
Sometime I also have read this article from interesting man from NASA http://arxiv.org/abs/0912.3818 . Therefore there are similar questions.

 Quote by mfb You would have to define what you mean by a different speed of light first. In SI units, the speed of light is constant by definition (the length of a meter is the distance light travels in 1/299792458 s). In other words, a "different speed of light" would be equivalent to a different length of a ruler. Which can be measured.
I am not sure, maybe some hard body, like it was defined a long time before.

 Quote by Alvydas Tank you. Maybe you can recommend one or two the best most sutable the case I was asking? Really would take much time to study deeply them all. Sometime I also have read this article from interesting man from NASA http://arxiv.org/abs/0912.3818 . Therefore there are similar questions.
The paper that you are citing is written by a known crackpot (Gezari).

DeSitter, Physik. Zeitschr. 14, 429, (1913) http://www.datasync.com/~rsf1/desitter.htm. DeSitter, Physik. Zeitschr. 14, 1267, (1913) http://www.datasync.com/~rsf1/desitter.htm.

 Quote by GAsahi The paper that you are citing is written by a known crackpot (Gezari). Read these: DeSitter, Physik. Zeitschr. 14, 429, (1913) http://www.datasync.com/~rsf1/desitter.htm. DeSitter, Physik. Zeitschr. 14, 1267, (1913) http://www.datasync.com/~rsf1/desitter.htm.
"In the theory of Ritz light emitted by a source moving with velocity u is propagated through space in the direction of the motion of the source with the velocity c + u, c being the velocity of light emitted by a motionless source."

Yes I know it and I agree with you about Ritz's theory. But this is not the case I was mentioned. Here all sources can be static and here are no assumption that speed of light depends on velocity of source.

Here is assumption that gravity of the Earth makes speed of light different in all directions.
But I don't need discussion about theory. By the way it even do not allow your forum rules.
I just need simple setup for experiment to test it.
Maybe somebody can paint it? Even with letters would be good enough.
For example maybe somebody had done MMX with one leg up or maybe some other very different ideas?

 Quote by Alvydas From your link: "In the theory of Ritz light emitted by a source moving with velocity u is propagated through space in the direction of the motion of the source with the velocity c + u, c being the velocity of light emitted by a motionless source." Yes I know it and I agree with you about Ritz's theory. But this is not the case I was mentioned. Here all sources can be static and here are no assumption that speed of light depends on velocity of source.

 Quote by Alvydas Lets say (just lets say for a moment) that speed of light is not constant. Lets say it is c-10km/s upward direction and c+10km/s downward direction (near the Earth).
The papers by DeSitter explain exactly what you asked for.

 Here is assumption that gravity of the Earth makes speed of light different in all directions.
You mean that you make this assumption, right?

 But I don't need discussion about theory. By the way it even do not allow your forum rules.
Yes, the forum disallows discussing fringe ideas.

 Quote by GAsahi The papers by DeSitter explain exactly what you asked for.
I am sorry am not sure I understand how exactly these observations with stars contradict to mentioned assumption.
I am not the first who was thought about it.
If it is out of forum rules here is my email allvydas eta gmail point com
Other experiments which most directly contradict to mentioned assumtion also welcom.
In general I have not idea how someone can desing experiment setup without knowing a big set of alternative views.

Mentor
 Quote by Alvydas For example maybe somebody had done MMX with one leg up or maybe some other very different ideas?
I do not remember seeing this, but I would bet money that experiments similar to this have been performed.
In addition, the increased precision of the measurements allow to measure the individual directions separately and other nice things.

 Quote by mfb I do not remember seeing this, but I would bet money that experiments similar to this have been performed. In addition, the increased precision of the measurements allow to measure the individual directions separately and other nice things.
Would be extreemly interesting to see info about it.
Just my guess: it likely could be free falling apparatus to avoid physical length contraction due gravity.

 Quote by Alvydas Here is a little why I have asked this question: Lets say (just lets say for a moment) that speed of light is not constant.
Once again, this forum disallows fringe speculations.

 Lets say it is c-10km/s upward direction and c+10km/s downward direction (near the Earth).
If that were true, GPS wouldn't work.