[extropy-chat] still no biscuit!

[Eliezer Yudkowsky]

This was a reply which was forwarded to me offlist:

> In general, if you make a measurement on a system, it is no longer
> closed (you have exerted forces on it), so there is no reason to
> expect momentum to be conserved.  If you make a precise measurement of
> the momentum (put the system in an eigenstate of momentum), let it be,
> and make a subsequent measurement of the momentum, you are indeed
> guaranteed to get the same answer.  This is true in both
> nonrelativistic and (special-)relativistic quantum mechanics; the only
> difference in the latter is that the momentum is no longer a kosher
> vector by itself; it is just the three spatial components of a
> four-vector and changes if you look at it from a moving frame of
> reference.
> 
> One of the posters intimated that the situation becomes more
> complicated in general relativity, which I can well believe; but I
> have never read anything about that.  From the popular press one
> gathers that there is at present no general-relativistic extension of
> quantum mechanics.

-- 
Eliezer S. Yudkowsky                          http://singinst.org/
Research Fellow, Singularity Institute for Artificial Intelligence