# I Can empty space be considered ‘elastic’ and expandable?

#### metastable

If you rotate your two electron apparatus you will get the same behavior. Therefore spacetime is isotropic.
^Dale, thank you for your answer, I wasn't confused by it until I remembered that I thought you said before I can't actually rotate the magnetic moment vector of the electron to a desired vector...

metastable said:
Is there a method that will cause the vector of the electron's magnetic moment to stop precessing & continuously point in a desired direction? Suppose I observe a distant galaxy and I want each measurement I perform of the electron's magnetic moment vector to show that it is substantially parallel with the vector pointing towards that galaxy from my present position within some small margin of error. What forces and methods would I rely on to orient the vector of the electron's magnetic moment in this desired vector?
Dale said:
Not that I know of. But why not just use a classical gyroscope instead?
Nugatory said:
No, if you’re thinking about an electron and quantum mechanical spin

#### PeterDonis

Mentor
I recognize there are different meanings but the meaning I actually intended for "comoving" was the cosmology meaning
If you meant "comoving" in the cosmological sense, then your claim that the test electron is comoving with the reference electron is wrong. Do you see why?

#### Dale

Mentor
I can't actually rotate the magnetic moment vector of the electron to a desired vector
All of the same quantum mechanical issues apply regardless of how you rotate your apparatus. If you can’t do something in one orientation then you can’t do it in any other orientation either. Therefore it is isotropic.

You really need to stop mixing the QM and the cosmological questions as we have discussed.

#### PeterDonis

Mentor
I can't actually rotate the magnetic moment vector of the electron
We're not talking about trying to rotate the electron's magnetic moment vector. We're talking about setting up the scenario with all of it rotated--i.e., the line connecting the two electrons is along a different direction. That won't make any difference to what happens in the scenario; that's what the universe being isotropic means. You can also set up the scenario anywhere in the universe you like, and it won't make any difference to what happens; that's what the universe being homogeneous means.

"Can empty space be considered ‘elastic’ and expandable?"

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