Can one determine that an instrument is an accelerometer locally?

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Discussion Overview

The discussion revolves around the ability to determine if an instrument is an accelerometer locally, particularly within the framework of special relativity (SR). Participants explore the conditions under which one can ascertain inertial movement and the implications of needing to identify an accelerometer without prior knowledge of its properties.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants assert that one can determine locally if one is moving inertially using an accelerometer.
  • There is a proposal that one can determine if a particular instrument is an accelerometer, but this may require knowledge of the absence of forces acting on a body.
  • One participant questions the necessity of knowing the full distribution of matter in the universe to ascertain inertial movement, suggesting simpler methods such as ensuring the device is uncharged and dropping it in vacuum.
  • Another participant raises questions about how to ensure a device is uncharged and how to identify a vacuum region, indicating a need for practical methods.
  • Responses include suggestions for grounding the device and referring to equipment manuals to identify vacuum regions, though the nature of these operations as "local" is questioned.
  • A later reply clarifies that the term "local" refers to a small enough region of spacetime to neglect curvature, aligning with general relativity (GR) concepts.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of global knowledge for determining inertial movement and the practicality of identifying an accelerometer without prior information. The discussion remains unresolved with multiple competing perspectives presented.

Contextual Notes

Some assumptions regarding the definitions of "local" and "vacuum" are not fully explored, and the discussion includes unresolved questions about practical methods for ensuring a device's properties.

atyy
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Let's stick to SR here.

Given an accelerometer, one can determine locally if one is moving inertially or not?

Can one determine locally if a particular instrument is an accelerometer? If one has no accelerometer, then inertial movement has to be determined by absence of forces on the body. This can be done by knowing the full distribution of matter in the universe, and ascertaining that that distribution of matter does not exert any force on the particle, which seems to be a global determination?
 
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atyy said:
Let's stick to SR here.

Given an accelerometer, one can determine locally if one is moving inertially or not?
Yes.

atyy said:
Can one determine locally if a particular instrument is an accelerometer?
Yes.

atyy said:
If one has no accelerometer, then inertial movement has to be determined by absence of forces on the body. This can be done by knowing the full distribution of matter in the universe, and ascertaining that that distribution of matter does not exert any force on the particle, which seems to be a global determination?
Why would you need to do that? Just make sure the device is uncharged and drop it in vacuum.
 
DaleSpam said:
Why would you need to do that? Just make sure the device is uncharged and drop it in vacuum.

How would one make sure the device is uncharged?

And how would one identify a region of space as vacuum? (I guess if it's uncharged, we don't have to drop it in vacuum, since it won't interact with matter anyway, so we just have to determine it's uncharged.)
 
Last edited:
atyy said:
How would one make sure the device is uncharged?
Connect it to ground for a little while.

atyy said:
And how would one identify a region of space as vacuum?
Look at the owner's manual for your pump. The region on the "inlet" side will be the one with vacuum.

Look atyy, everything I say you can respond with another series of "how would one" questions. It will get tiresome fast; I get enough of that from my kids (usually "why" questions). Please figure out what your real question is before continuing.
 
DaleSpam said:
Connect it to ground for a little while.

Look at the owner's manual for your pump. The region on the "inlet" side will be the one with vacuum.

Are these local operations?
 
Yes. This is "local" in the sense of GR. Meaning that it is over a region of spacetime small enough to neglect curvature.
 

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