# Can one determine that an instrument is an accelerometer locally?

1. Jun 1, 2010

### atyy

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?

2. Jun 2, 2010

### Staff: Mentor

Yes.

Yes.

Why would you need to do that? Just make sure the device is uncharged and drop it in vacuum.

3. Jun 2, 2010

### atyy

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: Jun 2, 2010
4. Jun 2, 2010

### Staff: Mentor

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.

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.

5. Jun 2, 2010

### atyy

Are these local operations?

6. Jun 2, 2010

### Staff: Mentor

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