Are Geometric Points Affected By Forces?

[JDoolin]

TL;DR Summary

Could there be two different "camps" of relativity? Could we call these "A priorists" who say costationary geometric points are definable independent of the motion of matter, and "Observists", who say costationary geometric points can only exist if matter is embedded witin those points?

Yesterday I found a playlist of videos by a youtuber "Dialect" who made a distinction between what he called Tier 1 and Tier 2 arguments of Relativity.

Tier 2 promoted a view that acceleration was an observer dependent phenomena. In particular he was discussing the Twin Paradox, and he said that in situations where observer A accelerates toward observer B, that one had an equal right to say that observer B is accelerating toward observer A.

Tier 1 promotes a view that acceleration is determined from an a priori inertial coordinate system. He said that Tier 1 advocates must accept "An inertial frame is not being acted on by any known force-producing sources". However, I do not find that this is a fair characterization. I would say An inertial frame (being constructed only of massless conceptual points) cannot be acted on by any known or unknown force-producing sources.

It seems to me, Newton's Second Law and the Impulse Momentum Theorem are designed to work in a non-accelerated reference frame. The acceleration of Newton's Second Law is intended to only include accelerations against an inertial frame (or at least approximately inertial on the time scales involved in the problem), and the net force is intended to include only real forces... Not fictitious forces such as the force that pushes you back in an accelerating bus, or the force that pushes you outward on a turning merry-go-round.

I have not studied General Relativity in sufficient detail to know how to solve, for instance, the Mercury Orbit problem. It seems to me that one could find a simplification to that problem by invoking a spinning coordinate system, much as one might invokes a spinning coordinate system to calculate the Roche Limit, or to explain the Dzhanibekov effect.

But in regards to the Dzhanibekov effect and Roche limit, one never actually makes the claim that the original inertial coordinate system does not exist. Rather, they invoke a rotating reference frame that coexists.

But in the pedagogy of General Relativity, is it generally taught that new noninertial coordinate systems are being introduced because this makes various problems easier to solve, or is it generally taught that the reason for not using inertial coordinate systems (Minkowski/Cartesian) is because such coordinate systems do not exist because they are unobservable?

Or are there simply two philosophical "camps" in Relativity theory... One camp believing that inertial frames do exist as definable entities, even though we cannot physically construct them, and another camp believing that inertial frames are undefinable, because we cannot construct them from masses and clocks?

 

[PeterDonis]

Yesterday I found a playlist of videos by a youtuber

This is not a valid reference. If you want to claim that there is any such distinction made by physicists, you are going to need to find valid references (textbooks or peer-reviewed papers) that say so.

 

[PeterDonis]

Tier 2 promoted a view that acceleration was an observer dependent phenomena. In particular he was discussing the Twin Paradox, and he said that in situations where observer A accelerates toward observer B, that one had an equal right to say that observer B is accelerating toward observer A.

Tier 1 promotes a view that acceleration is determined from an a priori inertial coordinate system.

Neither of these are a correct description of the role acceleration plays in relativity. In relativity, proper acceleration is an invariant; it is a direct observable (you can measure it with an accelerometer). There is also coordinate acceleration, but that, as its name implies, is a coordinate-dependent quantity that does not have any physical meaning.

 

[PeterDonis]

Thread closed due to lack of a valid reference as a basis for further discussion.