[extropy-chat] still no biscuit!

[scerir]

[fdwded by Eliezer]
> > 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.

This is the physical content of complementarity principle,
according to N.Bohr. Notice that Bohr - see i.e. the neutrino
case - was not a fan of conservation principles, at all.

'However, since the discovery of the quantum of action,
we know that the classical ideal cannot be attained in the
description of atomic phenomena. In particular, any attempt
at an ordering in space-time leads to a break in the causal
chain, since such an attempt is bound up with an essential
exchange of momentum and energy between the individuals and
the measuring rods and clocks used for observation; and just
this exchange cannot be taken into account if the measuring
instruments are to fulfil their purpose. Conversely, any
conclusion, based in an unambiguous manner upon the strict
conservation of energy and momentum, with regard to the dynamical
behaviour of the individual units obviously necessitates
a complete renunciation of following their course in space
and time'. (N.Bohr)

One would ask: what about Bohmian mechanics then? It is
a deterministic, causal, (non-local though) theory, 
is not it? So, it should provide a consistent 'course' 
of quantum events, in space and time. But this does not
seem to be the case, since the trajectories of Bohmian
mechanics are more "surreal" than real ...
http://www.arxiv.org/abs/quant-ph/0010020
http://www.arxiv.org/abs/quant-ph/0002046 

Aage Bohr (son of Niels) seems to push to the extreme 
the philosophy of complementarity saying that:
'Perhaps surprisingly, the very notion of genuine 
fortuitousness is powerful in its implications. 
With particles excluded, only geometry is left on the
stage, and the symmetry of spacetime itself, through 
its representations, provides the mathematical formalism 
of quantum mechanics. Once that point is recognized, 
quantum mechanics emerges from the principle of genuine
fortuitousness combined with the embodiment of spacetime 
symmetry, without any reference to degrees of freedom 
of particles or fields. The theory, exclusively concerned 
with probability distributions of genuinely fortuitous
clicks, thus differs from previous physical theories in 
that it does not deal with objects to be measured - which 
eliminates the issue of a quantum world.'
http://www.physicstoday.org/vol-57/iss-10/p15.html

The above point of view is not so far from the
'relational' interpretation of QM, by Carlo
Rovelli, or the 'Ithaca' interpretation of QM, 
by David Mermin.
http://www.arxiv.org/abs/quant-ph/9609002
http://www.arxiv.org/abs/quant-ph/9801057
http://www.arxiv.org/abs/quant-ph/9807055

s.

"Fields in empty space have physical reality;
the medium that supports them does not.
Correlations have physical reality;
that which they correlate does not."
- David Mermin