Inertial Frame of Reference: Why Space Selects a Non-Inertial Frame

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Discussion Overview

The discussion centers on the nature of inertial and non-inertial frames of reference, exploring why certain frames exhibit fictitious forces such as inertia. Participants delve into the implications of spacetime geometry and the concept of absolute space, questioning the underlying principles that dictate frame selection.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions why space appears to select specific frames as non-inertial, suggesting a potential for absolute characteristics in space.
  • Another participant argues that the distinction between inertial and non-inertial frames is determined by spacetime geometry, not by any magical selection process.
  • A further contribution explains that spacetime has properties that dictate certain characteristics, such as the invariant interval and the nature of straight lines, without favoring specific reference frames.
  • One participant emphasizes that the choice of reference frame is subjective, using an analogy of straight and curved lines to illustrate that non-inertial effects arise from the selection of a curved frame.

Areas of Agreement / Disagreement

Participants express differing views on the nature of frame selection, with some suggesting a more absolute characteristic of space while others maintain that it is a matter of geometric choice. The discussion remains unresolved regarding the implications of these perspectives.

Contextual Notes

Participants reference concepts such as the metric tensor and Christoffel symbols, indicating that the discussion involves complex mathematical and physical principles that may not be fully resolved within the thread.

mark_gg
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Why does one particular 'frame of reference' have fictitious forces (like inertia) whilst another one doesn't.

I understand the basics, but more interested in 'why' space seems to have magically chosen specific frame to be the 'non inertial frame'.

Could space be more absolute than we think it is?

Has any research been done in this problem, which is at odds with a truly relativistic space (although I'm not saying relativity is wrong)

Thank you.
 
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Nature doesn't "magically" choose the inertial and non-inertial frames or the inertial and non-inertial trajectories; such things are determined entirely by the space-time geometry i.e. by gravity.
 
Spacetime has properties--its geometry. The geometry of spacetime gives no preference to specific locations or times or directions or reference frames. But it does determine certain things:

(1) The invariant interval between two close-by events.
(2) Which spatial lines are "straight".
(3) Which spacetime paths are inertial.

In the usual treatment of Special Relativity and General Relativity, all of these features are derived from a geometric field called the metric tensor. The metric tensor doesn't determine a preferred state of rest, and it doesn't determine a preferred direction in space, but it does determine which paths are inertial and which lines are "straight".

In the geometric view of spacetime, a path being inertial is exactly analogous to a line being straight.
 
mark_gg said:
I understand the basics, but more interested in 'why' space seems to have magically chosen specific frame to be the 'non inertial frame'.
There is nothing magical about it. The reference frame is a matter of choice. If you choose a curved reference frame then you get non-zero Christoffel symbols.

As an analogy, if you have a blank piece of paper, no coordinates, you still have straight lines and curved lines. If you then base your coordinates off the curved lines you would have "coordinate acceleration" of straight lines.

Do you think it is magical that both straight and curved lines exist? Do you think it is magical that they can be distinguished from each other?
 

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