Galilean Relativity: Can Experiments Tell Motion Relative to Other Frames?

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Discussion Overview

The discussion revolves around the implications of Galilean Relativity, specifically whether experiments can determine motion relative to other inertial frames. It explores theoretical aspects of mechanics and the nature of reference frames.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant states that in Galilean Relativity, laws of mechanics are invariant across frames, suggesting that no experiment can determine if an inertial frame is moving or at rest relative to another frame.
  • Another participant argues that if laws of physics were different between inertial reference frames, measurable consequences would arise, allowing one to determine their speed by measuring those changes.
  • A subsequent reply agrees that measurable changes would occur if the frame of reference changes speed but questions how one could determine the speed of another frame without knowledge of its existence.
  • Another participant proposes a hypothetical scenario where the speed of light varies with direction in different frames, suggesting that such a variation could indicate a special frame. However, they conclude that in our universe, no such measurement is possible.

Areas of Agreement / Disagreement

Participants express differing views on whether experiments can determine motion relative to other frames, with some suggesting that measurable differences could exist while others maintain that such determination is not possible without knowledge of other frames.

Contextual Notes

The discussion includes assumptions about the nature of physical laws across frames and the implications of varying laws, which remain unresolved. The hypothetical scenarios presented also depend on specific conditions that are not established in the current framework of physics.

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In Galilean Relativity, laws of mechanics are invariant across frames. In all the frames they are the same.

So, in Dynamics and Relativity by W.D.McComb, it is written that this implies you cannot perform any experiment in an inertial frame that can tell whether an inertial frame is moving or at rest with respect to another frame.

My question is suppose laws of Physics are different in different frames, then if we are in a frame, can we perform mechanical experiments to determine its speed with respect to other inertial frames.
 
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If the laws of physics were different between every inertial reference frame depending on speed, there would be measurable consequences.
If some measurable thing did change with your reference frame's speed, then you could tell your speed by measuring that thing.
 
jfizzix said:
If the laws of physics were different between every inertial reference frame depending on speed, there would be measurable consequences.
If some measurable thing did change with your reference frame's speed, then you could tell your speed by measuring that thing.
Hi , thank you for your response.
The change will happen if the frame of reference in which you, changes its speed. I totally agree we can measure that change.
However, if we are just in our frame, what does it mean to determine the speed of other frame ? We do not even know of their existence
I am not able to understand this.
 
Imagine that the speed of light varied with direction (i.e. light behaved like a wave in a medium), except in one frame in which it is isotropic. That would hint that there was something special about the frame where the speed is isotropic, and how much the speed varied in your chosen frame would tell you how fast you were going with respect to that special frame.

In our universe, you can't do this (or anything analogous) by any means we are aware of.
 

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