B Looking Out of the Window: Phys & Math Meaning in Postulates & Principles

[roineust]

What is the physical and mathmatical meaning, of the metaphorical action of 'looking out of the window' or 'not looking out of the window', of a ship, a starship, a train, an elevator or any other vehicle, in postulates such Galilean postulate and SR 1st postulate and in GR weak and strong equivalence principles?

Does 'looking out of the window' mean having a direction?

If there is an experiment equipment within the vehicle, that measures a phenomenon and tells about the difference of constant speed of two measurments or the difference between gravity and acceleration of two measurments, but this equipment does not use any data or information about that phenomenon, which involve direction of arrival or direction of departure of that phenomenon, does such a measurment, qualify as 'not looking out of the window'?

Is it possible and scientific, that a postulate or a principle, will be based on an understanding, that even theoretically, there could be no way of satisfying the condition of 'not looking out of the window'?

If there is even no theoretical possibility to be 'not looking out of the window', then doesn't that mean that an experimental measurment has no meaning, while using such a postulate or principle?

If this is the case, what kind of science is it, that involves agreement on nullifying the meaning of the measurment act?

 

[Ibix]

Typically, "looking out of the window" relates to the measurement of speed. That boils down to the claim that you cannot even define speed except relative to something else. In that case, in a sealed room, I can only define the speed of the room with respect to things inside the room because I can't measure anything else.

One could posit a system of physics where this was not the case. A Michelson-Morley interferometer, if there had been a classical ether of the kind they expected, would allow you to measure speed with respect to an ether that couldn't be excluded from the room. I gather people do continue to search for violations of Lorentz covariance, but so far we've never seen evidence of it.

 

[PeterDonis]

What is the physical and mathmatical meaning, of the metaphorical action of 'looking out of the window' or 'not looking out of the window', of a ship, a starship, a train or any other vehicle, in postulates such Galilean postulate and SR 1st postulate and in GR weak and strong equivalence principles?

It means using information that cannot be acquired solely from observations made within the ship, starship, train, etc. The point is that the equivalence principle only applies to local observations, i.e., it only takes into account information that can be acquired solely from observations within the ship, starship, train, etc.

 

[roineust]

Typically, "looking out of the window" relates to the measurement of speed. That boils down to the claim that you cannot even define speed except relative to something else. In that case, in a sealed room, I can only define the speed of the room with respect to things inside the room because I can't measure anything else.

One could posit a system of physics where this was not the case. A Michelson-Morley interferometer, if there had been a classical ether of the kind they expected, would allow you to measure speed with respect to an ether that couldn't be excluded from the room. I gather people do continue to search for violations of Lorentz covariance, but so far we've never seen evidence of it.

I mean experimental equipment that can tell the difference of 2 different constant speeds or difference between gravity and accelaration in 2 different measurments, using gravitational waves phenomenon, without using any information about the arrival or departure direction of these gravitational waves.

Would that qualify as 'not looking out of the window'?

 

[Ibix]

You could only measure your speed with respect to the gravitational wave.

As has been pointed out to you several times before, if you can detect a gravitational wave then your sealed box is large enough that the equivalence principle does not apply. You may well be able to detect non-uniformity in the gravitational field if any is present.

To be honest, I think you are completely missing the point here. The equivalence principle, when stated mathematically, is simply that the effects of some specified curvature will always be less noticeable in a smaller region than in a larger region (one that contains the smaller region), and can be made to vanish at a point. Closed boxes and open windows is simply a loose illustration.

 

[roineust]

As has been pointed out to you several times before, if you can detect a gravitational wave then your sealed box is large enough that the equivalence principle does not apply. You may well be able to detect non-uniformity in the gravitational field if any is present.

I was told, but was never given any intuitive explanation.

 

[Vanadium 50]

I think you were told and refused (and continue to refuse) to accept the explanation.

You really have two options: learn the math and check it yourself, or trust those who can and did. There really is no third alternative. Or, as a famous painter once said "Two and two continue to make four, despite the whine of the amateur for three or the cry of the critic for five."

 

[roineust]

I think you were told and refused (and continue to refuse) to accept the explanation.

You really have two options: learn the math and check it yourself, or trust those who can and did. There really is no third alternative. Or, as a famous painter once said "Two and two continue to make four, despite the whine of the amateur for three or the cry of the critic for five."

Sorry, i don't understand what it is that you say that i was told, since all you always say is only that i was told.

Are you saying that i was told anytime in the past by you, anything besides i was told? I don't think so or can't remember such an ancient telling.

 

[Ibix]

I was told, but was never given any intuitive explanation.

An intuitive explanation for what? The notion that if you can detect curvature you cannot neglect curvature in your measurements? Or for the equivalence principle? That's just an experimental observation by Einstein (or, more precisely, an insight into Galileo's acceleration of falling masses experiments) that guided his mathematical thinking. Or for its mathematical form? That's just a statement about degrees of freedom and smoothness of solutions to differential equations.

 

[roineust]

An intuitive explanation for what? The notion that if you can detect curvature you cannot neglect curvature in your measurements? Or for the equivalence principle? That's just an experimental observation by Einstein (or, more precisely, an insight into Galileo's acceleration of falling masses experiments) that guided his mathematical thinking. Or for its mathematical form? That's just a statement about degrees of freedom and smoothness of solutions to differential equations.

And how do you know when using the equivalence principle, that if you have an equipment sensitive enough, you can ever measure any gravity without a curvature?

 

[Ibix]

And how do you know when using the equivalence principle, that if you have an equipment sensitive enough, you can ever measure any gravity without a curvature?

I cannot understand that question.

 

[roineust]

I cannot understand that question.

I will think it over for a while and try to explain myself better, perhsps i will need to ask some questions on the way there.

 

[Dale]

And how do you know when using the equivalence principle, that if you have an equipment sensitive enough, you can ever measure any gravity without a curvature?

I am also having trouble parsing this question

 

[PeterDonis]

I mean experimental equipment that can tell the difference of 2 different constant speeds or difference between gravity and accelaration in 2 different measurments, using gravitational waves phenomenon, without using any information about the arrival or departure direction of these gravitational waves.

There is no such equipment possible. That is what GR says. The equivalence principle applies to gravitational waves as it does to everything else. That answer has been given to you in previous threads, and it will stay the same no matter how many times you try to ask the same question in different words and with different scenarios.

 

[PeterDonis]

The OP question has been answered. Thread closed.