Non-arbitrary frame of reference for acceleration?

In summary, the conversation discusses how the ability to choose a frame of reference arbitrarily in physics relates to Noether's Theorem and laws of conservation. In Newtonian Mechanics, momentum conservation is expressed through the action-reaction law, but for fictitious forces, such as those in an accelerating frame of reference, there is no corresponding reaction force. This leads to the question of whether a non-arbitrary frame of reference is needed for acceleration, and the role of a "master" frame of reference in Special and General Relativity. The conversation concludes by clarifying that inertial frames, not a single "master" frame, are necessary for understanding acceleration, and that this concept applies to both SR and GR.
  • #1
The Adversary
11
0
The reason we can choose a frame of reference arbitrarily is that a physical system is not dependent on an absolute position, orientation or time.
According to Noether's Theorem, the invariance of a system under a change of position is equivalent to the momentum conservation law.
In the same way, invariance under a change in orientation is the angular momentum conservation law, and time invariance is the law of
conservation of energy.
In Newtonian Mechanics, momentum conservation is expressed as the action-reaction law; If for every force (change of momentum) there's an equal and opposite
reaction force, momentum is conserved.
For fictitious forces however, like the force that acts when the frame of reference itself is accelerating, there's no corresponding
reaction force; Hence there seems to be no conservation law in that case.
Does this not point in the direction of a non-arbitrary frame of reference for acceleration?
I've looked around on google, but I've always heard that this is an unsolved mystery in physics.

Any ideas?
 
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  • #2
The Adversary said:
Does this not point in the direction of a non-arbitrary frame of reference for acceleration?
I've looked around on google, but I've always heard that this is an unsolved mystery in physics.
This is not an unsolved mystery. There is not a single non arbitrary frame, but rather a whole class of them. They are called inertial frames. They are discussed frequently.
 
  • #3
You always end up with some kind of 'master' frame of reference that must contain all other frames of reference otherwise you can't express the acceleration
of a reference frame. And within a non-master reference frame, the acceleration of it acts as a fictitious force.
And if you include all of the fictitious forces, including the ones for rotation and accelerated rotation, your laws of physics always look the same
in all reference frames. I believe you can then call your laws generally invariant, even though that term is usually reserved for GR.
But it always requires a Master Frame!
I'm curious whether or not this Master Frame is also required in SR and GR; My gut tells me yes, but ...
 
  • #4
The Adversary said:
You always end up with some kind of 'master' frame of reference that must contain all other frames of reference otherwise you can't express the acceleration
of a reference frame.
No, you don't. You end up with a set of 'master' frames called inertial frames. You can express the acceleration of a non inertial frame with respect to any of them completely equivalently.

Furthermore, inertial frames do not "contain" non inertial frames. They are simply physically distinguishable from non inertial frames. I.E. the distinction is not arbitrary.

The Adversary said:
But it always requires a Master Frame!
I'm curious whether or not this Master Frame is also required in SR and GR; My gut tells me yes, but ...
Your gut is wrong.
 
  • #5
After deleting yet another post repeating the same misinformation, this thread is closed.
 

1. What is a non-arbitrary frame of reference for acceleration?

A non-arbitrary frame of reference for acceleration refers to a specific point or object chosen as the basis for measuring the acceleration of other objects in motion. This frame of reference is chosen based on its relation to the motion being studied and is not influenced by personal bias or preference.

2. Why is it important to have a non-arbitrary frame of reference for acceleration?

Having a non-arbitrary frame of reference for acceleration allows for accurate and consistent measurements of acceleration. It also helps to eliminate any subjective influence on the data and allows for comparisons between different objects or systems.

3. How is a non-arbitrary frame of reference for acceleration determined?

A non-arbitrary frame of reference for acceleration is determined by considering the motion being studied and selecting a point or object that is stationary or has a constant velocity relative to the motion. This frame of reference should be easily identifiable and measurable.

4. Can a non-arbitrary frame of reference for acceleration change?

Yes, a non-arbitrary frame of reference for acceleration can change depending on the motion being studied. For example, if studying the acceleration of a ball rolling along a ramp, the frame of reference may be the starting point of the ball. But if studying the acceleration of a car on a straight road, the frame of reference may be a stationary object on the side of the road.

5. How does a non-arbitrary frame of reference for acceleration differ from an arbitrary frame of reference?

A non-arbitrary frame of reference for acceleration is based on scientific principles and is chosen based on its relation to the motion being studied. An arbitrary frame of reference, on the other hand, is chosen for convenience or personal preference and may not accurately represent the motion being studied.

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