Sum up Questions for Gravitational Waves & Weighing Scales

[roineust]

In spite of all the problems that apparently arise from my questions or from what these questions represent (among these problems 'do not seem to agree with the underlying framework'), i would be obliged if someone can answer me the following questions, which i am hesitant to ask here as a thread, since i think the thread will be locked, way before any answer which i can understand will be replied:

Here is a quote which is a part of a reply to a thread that i posted last Thursday, under the subject "Gravitational Waves Question", which states:

"Yes, a passing gravitational wave does, in principle, affect the reading on a weighing scale.."

My initial question is:

Does a passing gravitational wave, in principle, also affect the reading on a weighing scale accelerated in a straight line in space (where there is negligible gravity), as if it was weighing a mass on a planet or for example, weighing on Earth and then in comparison accelerated in space at 9.8 m/s^-2?

1. If the answer to this initial question is in principle YES, the following questions are*:
*But it does not seem to be the answer that i am mostly given and therefore, you can jump ahead to questions 1.B. , 2 and 3.

1.A. Therefore acceleration in a straight line is equal to gravity, to the extent that it is influenced to the exact same amount by gravitational waves, as gravity does, i.e. acceleration of a mass in a straight line produces gravity and can in principle, change and be changed in measurement of properties by gravitational waves?

If the answer to 1.A. is YES or NO, my following question is:

1.B. Does gravity (and acceleration of a mass in a straight line*) also produce gravitational waves? I was answered in previous threads, that gravity and gravitational waves are not the same, because gravitational wave is a tidal wave.

*This question also stands regarding only gravity and not acceleration of mass in a straight line, in case the answer to question 1.A. is NO.

But i don't understand:

1.B.1 If the difference between gravity and gravitational waves (tidal waves), is an essential difference or only a difference in scale of magnitude. If it is an essential difference, can you explain this further or refer to a good explanation, that also relates to how these 2 apparently essentially different phenomenon of gravity and gravitational waves, do influence one another after all?

1.B.2. Why does a mass that moves in a rotational path or in a cyclical path do create gravitational waves, while close to static mass, and mass moving at constant speed in a straight line, and mass accelerated in a straight line, can not produce gravitational waves? Does it have to do with angular acceleration or with other properties of the masses' movement path?

1.B.3. If it has to do with angular acceleration, what is the essential difference that angular acceleration has, in comparison to constant speed and acceleration in a straight line, that produces gravitational waves in one case but does not produce them in the other cases?2. If the answer to the initial question in this thread is NO, the following question is:

2.A. How does this come into terms with the equivalence principle of general relativity, which states that gravity and acceleration are the same?

I seem to be given answers in this relation, which often include the term 'locally' and that the equivalence principle is defined only 'locally'. But i don't seem to understand this well enough: For sure the equivalence principle is not defined in such a way, that it is experimentally not testable?

For example, if the equivalence principle includes by definition of the term 'locally' an area or a point in space, which are infinitely small, i.e. an area or a point in space that size is by definition, impossible to build any experimental equipment that can measure what happens inside such a point or an area? Can you please explain further in this regard?3. What is the difference in scale of magnitude, between the current gravimeters best sensitivity (10^-11 m/s^-2) and the amount of sensitivity needed, in order to be able to influence the reading of the gravimeter by: 1. Gravitational waves measured by current LIGO like devices. 2. Gravitational waves that are perhaps hypothesized to be prevalent through the universe, even if they have properties that are at a scale of magnitude, that is currently not possible to measure by LIGO like devices.

 

[Vanadium 50]

IBTL.

You've asked before.
You don't like the answer. (Or maybe don't believe the answer)
You've asked again.
You got the same answer.
You still don't like the answer.
You've asked again.
You got the same answer.
You still don't like the answer.
You've asked again.
You got the same answer.
You still don't like the answer.

Do you really think this time will be different?

 

[roineust]

IBTL.

You've asked before.
You don't like the answer. (Or maybe don't believe the answer)
You've asked again.
You got the same answer.
You still don't like the answer.
You've asked again.
You got the same answer.
You still don't like the answer.
You've asked again.
You got the same answer.
You still don't like the answer.

Do you really think this time will be different?

Sorry, but i don't understand how your reply answers my questions, which are an attempt, as can be seen from the subject matter, to summarize and elaborate the questions from my previous posts.

 

[Ibix]

Does a passing gravitational wave, in principle, also affect the reading on a weighing scale accelerated in a straight line in space (where there is negligible gravity) to the exact same amount,

No. Frequency and amplitude would be different due to gravitational blueshift. Edit: actually it's more complex than that - the accelerating observer would see a different waveform entirely due to the changing tangent vector of their worldline.

Does gravity (and acceleration of a mass in a straight line*) also produce gravitational waves?

The source of gravitational waves is a changing quadropole moment. Some accelerating masses have this, some do not. Static gravitational fields do not produce gravitational waves.

1.B.1 If the difference between gravity and gravitational waves (tidal waves), is an essential difference or only a difference in scale of magnitude. If it is an essential difference, can you explain this further or refer to a good explanation, that also relates to how these 2 apparently essentially different phenomenon of gravity and gravitational waves, do influence one another after all?

All gravitational phenomena are just solutions of Einstein's Field Equations. Just like electric fields, magnetic fields, and light are all solutions of Maxwell's equations. All electric, magnetic and electromagnetic phenomena are in some sense the same thing (just disturbances of the electromagnetic field) but different types of disturbance with different properties and effects.

Whether you regard static gravitational fields as different things from gravitational waves is up to you. You seem to see them as different (for example in your previous thread you repeatedly referred to static gravitational fields as a force but not gravitational waves, which was what prompted my comment about you not accepting the model that we can use to answer you). I'd suggest that it's unhelpful. I'd say they're the same underlying phenomenon in different circumstances.

1.B.2. Why does a mass that moves in a rotational path or in a cyclical path do create gravitational waves, while close to static mass, and mass moving at constant speed in a straight line, and mass accelerated in a straight line, can not produce gravitational waves?

Do they have a changing quadropole moment? If so, they produce gravitational waves. If not, they don't.

2.A. How does this come into terms with the equivalence principle of general relativity, which states that gravity and acceleration are the same?

The equivalence principle doesn't state that. It just says that for any given experimental precision there exists a box small enough that you cannot distinguish "at rest on the surface of a planet" from "at rest in an accelerating rocket".

There are a lot of tests of the equivalence principle. An obvious one is Galileo's cannon ball experiment.

3. What is the difference in scale of magnitude, between the current gravimeters best sensitivity (10^-11 m/s^-2) and the amount of sensitivity needed, in order to be able to influence the reading of the gravimeter by: 1. Gravitational waves measured by current LIGO like devices.

That isn't the point. The point is that the Earth is not a rigid body. It vibrates at much higher amplitudes than the signal you are trying to detect. You can't isolate your sensor from this noise by disconnecting it from the Earth because its the contact force that you are trying to measure.

 

[PeterDonis]

i am hesitant to ask here as a thread, since i think the thread will be locked, way before any answer which i can understand will be replied

You are right, the thread will be locked way before any answer which you can understand will be given. That is because you do not have the conceptual background to understand the (correct) answers you are being given, and you are not receptive to attempts to give you a better conceptual background.

In other words, the problem of you not getting answers you can understand is not a problem we can fix by you posting the same question again and again and us giving the same answers again and again. It is a problem you have to fix by taking the time to build your own correct understanding of GR, so that you have the conceptual background to understand what you are being told.

In building your own understanding, I would advise not even trying to understand gravitational waves until you have a more basic understanding of how GR works. Hint: if you are using the term "gravity" without qualification, and think that term has a well-defined meaning, you don't have a basic understanding of how GR works. In GR, there is no single thing which is "gravity", and it's better to not use the term "gravity" at all, but to focus on the different things that GR models directly, like spacetime geometry, spacetime curvature, path curvature of worldlines, and the equivalence principle. Another hint: if you think the equivalence principle means "acceleration is equivalent to gravity", you don't have a good basic understanding of how GR works.

 

[PeterDonis]

the thread will be locked way before any answer which you can understand will be given.

In other words, right now. Thread closed.