Instantaneous Communications plus Time Dilation Equals ???

[Zeropoint]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Okay. Call up the people who designed the GPS system and tell them that the effects they're compensating for aren't real.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Okay. Call up the people who designed the GPS system and tell them that the effects they're compensating for aren't real.

 

OK, in detail, what are they actually compensating for? The light-speed delay and a slightly slower clock on the satellites, or the crazy-quilt effect described in the "train example"?

[Zeropoint]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

What you call the crazy quilt effect (in addition to the lightspeed delay and the clocks running faster on the satellites, of course). I'm sorry if it offends your sensibilities, but it's established, experimentally verified fact.

 

Sagnac distortion

 

GPS observation processing must also compensate for the Sagnac effect. The GPS time scale is defined in an inertial system but observations are processed in an Earth-centered, Earth-fixed (co-rotating) system, a system in which simultaneity is not uniquely defined. A Lorentz transformation is thus applied to convert from the inertial system to the ECEF system. The resulting signal run time correction has opposite algebraic signs for satellites in the Eastern and Western celestial hemispheres. Ignoring this effect will produce an east-west error on the order of hundreds of nanoseconds, or tens of meters in position.

 

It's real, no matter how much it bugs you.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

The Sagnac effect is not an artifact of the choice of reference frame. It is independent of the choice of reference frame, as is shown by a calculation that invokes the metric tensor for an observer at the axis of rotation of the ring interferometer and rotating with it yielding the same outcome.

 

That doesn't sound like the Sagnac effect has anything to do with the "crazy-quilt" effect from the "train example" -- which specifically references different observations at different "frames of refernce".

[Xavier Onassiss]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

That doesn't sound like the Sagnac effect has anything to do with the "crazy-quilt" effect from the "train example" -- which specifically references different observations at different "frames of refernce".

 

The important connection is in the paragraph labelled Synchronization Procedures. From the linked article:

 

On a non-rotating planet that ensures fidelity: two time-disseminating relays, going full circle in opposite directions around the globe, will arrive at the originating station simultaneously. However, on a rotating planet, it must also be taken into account that the receiver moves during the transit time of the signal, shortening or lengthening the transit time compared to what it would be in the situation of a non-rotating planet.

 

It is recognized that the synchronization of clocks and ring interferometry are related in a fundamental way. Therefore the necessity to take the rotation of the Earth into account in synchronization procedures is also called the Sagnac effect.

 

When you look at it this way, it's easier to see the similarity to the differing reference frames in the 'train experiment.'

 

 

Don't look at me,

Xavier Onassiss

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

The important connection is in the paragraph labelled Synchronization Procedures. From the linked article:

 

 

 

When you look at it this way, it's easier to see the similarity to the differing reference frames in the 'train experiment.'

 

It seems to me that you'd have to adjust for the rotating planet anyway.

[austenandrews]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Sure' date=' fine, but where it breaks down in the "train example" is still in the assertion that it behaves in as many ways as there are different frames of references around it, that it does multiple things at the same time, instead of one thing.[/quote']

It only does one thing. It acts like a chunk of spacetime.

[Lawnmower Boy]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Kris, it's a transformation from one inertial frame of reference to another, just using the Lorentz-Fitzgerald transform instead of the Galilean one that you regard as intuitive, and it is exactly like the train example. The video lecture pasted in above should be a quite sufficient explanation.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Kris' date=' it's a transformation from one inertial frame of reference to another, just using the Lorentz-Fitzgerald transform instead of the Galilean one that you regard as intuitive, and [i']it is exactly like the train example. [/i]The video lecture pasted in above should be a quite sufficient explanation.

 

I watched it when you posted it.

[Lawnmower Boy]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Nothing says that you can't watch it again, but you might also want to work through some problems. Draw the spacetime diagrammes for the train examples, for instance.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Nothing says that you can't watch it again' date=' but you might also want to work through some problems. Draw the spacetime diagrammes for the train examples, for instance.[/quote']

 

First, working through all the theoretical examples in the world isn't going to change the fundamental issue here.

 

Second, I find it laughable that several people are making an assumption that this is about "the intuitive understanding of reality".

[Lawnmower Boy]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Your concerns about the nature of reality will be resolved once once you've worked through a few problem sets. This is no different from any other problem in geometry or kinematics, other than in the use of the non-Galilean coordinate transformation. And we may be arguing past each other in our definition of intuition, which I would simply regard as a synthetic a priori. Euclidean spacetime is an invalid synthetic a priori. Causality is probably not. As you will see in working through the problems, causality is maintained in special relativity.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

But according to the oft-mentioned example that kicked this all off, there's still the issue of the same damn photon doing different things depending on where you're watching it from, a crazy-quilt / house-of-mirrors effect.

[austenandrews]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

The photon only does one thing - travel at the speed of light and strike one end of the train. That's all it ever does. It does that in every frame of reference.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

The photon only does one thing - travel at the speed of light and strike one end of the train. That's all it ever does. It does that in every frame of reference.

 

Then the train car example we've been discussing is a terrible and inaccurate example.

[austenandrews]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

It's a textbook example. There are two photons. One travels at c and strikes one end the train car. The other travels at c and strikes the other end of the train car. These two events happen in every frame of reference.

 

The bone of contention is the idea that these two events have some concrete order. That's an illusion.

[Nyrath]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Kristopher, you are pounding your head against a brick wall here. This is an RPG forum, not a classroom.

 

FIND A PHYSICS PROFESSOR AND ASK THEM.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Kristopher, you are pounding your head against a brick wall here. This is an RPG forum, not a classroom.

 

FIND A PHYSICS PROFESSOR AND ASK THEM.

 

It's not as if they'll provide something that's not provided here or in the sources I've looked up online.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

It's a textbook example. There are two photons. One travels at c and strikes one end the train car. The other travels at c and strikes the other end of the train car. These two events happen in every frame of reference.

 

The bone of contention is the idea that these two events have some concrete order. That's an illusion.

 

The bone of contention is that the example claims that the train car is moving relative to the light, and is not moving relative to the light, at the same damn time.

[Nyrath]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

It's not as if they'll provide something that's not provided here or in the sources I've looked up online.

 

Ummmm, not to put too fine a point on it, but a human being who is an expert in the matter in question is generally always superior to an un-living textbook or webpage, or living people who are not experts. A professor can go over your argument with you, and clarify matters. That's what they do for a living.

 

If you do not want to talk to an expert, then I'm at a loss over what exactly you do want. We are mostly unwilling to espouse your belief that GPS satellites cannot possibly work since they were designed using the theory of relativity you maintain is fraudulent.

 

You cannot just take the parts of relativity theory you want, it predicts both the GPS shift and the lack a concrete order of events on the train car. If you reject the train car, you reject all of relativity.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

I've never said that GPS sats don't work, nor do I believe any such thing.

[Zeropoint]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

You agree that they work, yet you deny that the effects which they have to account for are real.

 

Premise one: The Global Positioning System works as designed.

Premise two: The Global Positioning System is designed to accommodate relativistic effects, including relative simultaneity.

 

That you can accept these two premises, yet deny the conclusion that relative simultaneity is real indicates to me either a severe failure of reasoning ability, or an irrational attachment to outdated Newtonian models.

 

Your belief that the light reaching the front of the train and the light reaching the back of the train must occur in a single clearly defined sequence is not in accord with Relativity theory, nor with experimental evidence. In short, said belief does not match reality.

 

At this point, I find myself wondering whether you reject the conclusion because you perceive (due to incomplete understanding) a flaw in the arguments presented, or because you simply don't LIKE the conclusion.

 

If it's the former, please help us to understand what you're missing.

 

If it's the latter . . . further discussion is pointless.

[Nyrath]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

I've never said that GPS sats don't work' date=' nor do I believe any such thing.[/quote']

 

So you do agree that the two events in the train do not have some concrete order.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

You agree that they work, yet you deny that the effects which they have to account for are real.

 

Premise one: The Global Positioning System works as designed.

Premise two: The Global Positioning System is designed to accommodate relativistic effects, including relative simultaneity.

 

That you can accept these two premises, yet deny the conclusion that relative simultaneity is real indicates to me either a severe failure of reasoning ability, or an irrational attachment to outdated Newtonian models.

 

Your belief that the light reaching the front of the train and the light reaching the back of the train must occur in a single clearly defined sequence is not in accord with Relativity theory, nor with experimental evidence. In short, said belief does not match reality.

 

At this point, I find myself wondering whether you reject the conclusion because you perceive (due to incomplete understanding) a flaw in the arguments presented, or because you simply don't LIKE the conclusion.

 

If it's the former, please help us to understand what you're missing.

 

If it's the latter . . . further discussion is pointless.

 

Is the train car catching up with the light, or not?

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

So you do agree that the two events in the train do not have some concrete order.

 

When did I say that?