So, relatively speaking...

Would it be correct to say that you can't measure your own absolute location or speed, but you can measure your absolute spin? Does this have any significance?

And while some people refer to relativity when explaining why there can't be a universally agreed upon time system, doesn't the 4-dimensional model of the universe implied in relativity mean that the time and location of any event can be described with 4-dimensional coordinates, presumably with some agreed upon non-accelerating object as reference.

how do you know its non-accelerating.

>>1
Please use rotation instead of spin. Spin has a different meaning in physics.

And yes, if you take an arbitrary reference point you can describe the entire universe that way. The point of relativity is that there are no absolute reference point, and every reference point is necessarily arbitrary.

>>2
Back to /b/, please.

>>3
Ah, yes. I meant the angular speed, to be more precise.

Theres uncertainty in angular speed as well.

Angular momentum operator L^2 commutes with position and velocity though, doesn't it?

>>6
True.

What exactly doesn't it commute with though.

I know it doesn't commute with L_x_i if you get my notation (Can't do subscripts) for x,y and z.

But is there another obvious quantity, in the same vein as postion and veloctity, that it doesn't commute with?

>>8
Last I recall, L² commutes with everything.
L_x doesn't commute with L_y though.

It can't commute with everything, or can it :-/

I was pretty cetain [L^2,L_x]=ih

where I mean h bar but can't write that silly shit.

>>10
ħ

>>10
http://en.wikipedia.org/wiki/Canonical_angular_momentum

Besides, {L,L_z} is one of the most common bases in which to do quantum computations.  This basis would not make sense if what you said was true.

Use the [sup] and [sub] tags.

>>12
blah. I need to learn this shit before the exams.

[sup] [sub]

aa ^aa
aa _aa

There isn't any way to measure Spin (not angular speed/rotation) right?

>>17
Spin is a property of elementary particles, not large bodies.