Natural Science Forum / Physics / Particle Physics / October 2004

A while ago there was a discussion about nuclear radioactive decay and
how it is an inherently random process. Quantum mechanics avers that,
at some level, there no point in asking what *causes* a nucleus to
decay. In fact, QM forces the abandonment of inner, deterministic cogs
and wheels that would more deeply account for the nuclear state with
an intrinsic half-life (decay probability). There's been much
historical gnashing about whether that's due to the act of measurement
disturbing the measured quantity, or due to a spread wavefunction that
collapses only at the point of measurement, or whatever, but that's
largely beside the point/question I want to pose here.

The problem is, we *do* understand the nucleus at a level more
fundamental than just the nucleus-as-a-random-entity. We can describe
it as a collection of nucleons, or as a collection of nucleons and
(more) virtual mesons, or -- if we are ambitious -- with QCD, perhaps
using a lattice calculation and a bunch of computers.

So -- and here's the question -- where does the inherent randomness of
the nuclear decay get transferred in the deeper explanation? Assuming
that the inherent randomness of QM persists and does not get replaced
by a purely deterministic description, this randomness must express
itself in the underlying nuclear shell model or QCD or whatever, so
that the purely random nature of the nuclear decay is accounted for by
that.

What are your thoughts on this? For the purpose of this thread, I
would ask that we assume that the indeterminacy of QM is assumed and
that we not bog down the discussion with cries that "QM is bogus and
the universe really is deterministic -- even Einstein said so."

PD