🚀 go-pugleaf

In article <1992Apr14.162249.17020@kakwa.ucs.ualberta.ca> anderson@fermi.phys.ualberta.ca (Warren G. Anderson) writes:
>I think everyone has been pretty much missing Kens point here (or maybe I am).
>
>Consider the following. Prepare an excited particle in a state with finite  
>uncertainty in momentum. Around the particle, put a sherical detector that 
>measures exactly (it's a thought experiment, ok :-) the momenta of massive
>particles and the position of photons. Allow the excited particle to return
>to ground state.
>
   But the particle and photon are entangled, so the momentum of the
particle and the position of the photon are non-commuting observables. By
purely mathematical consistency arguments you can show that it is not
possible, even in principle, to measure both those quantities to
arbitrary precision.

>So, it seems that I have to either abandon conservation of energy
>or Heisenberg's uncertainty principles.
>
   No, the uncertainty principle says that you couldn't manufacture such
a system in the first place. You might as well be asking about the
behaviour of a wave packet which is arbitrarily short in time, and is
also a pure single frequency. Such beasts do not exist.

>##  Warren G. Anderson


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