  The insertion of a small polarizable particle in an arbitrarily large optical
cavity significantly alters the quantum-mechanical state of the electromagnetic
field in that the photon ground state of the empty cavity and that of the
cavity with the particle become mutually orthogonal and, thus, cannot be
connected adiabatically in the infinite limit. The photon problem can be mapped
exactly onto that of a many-body system of fermions, which is known to exhibit
an orthogonality catastrophe when a finite-range local potential is introduced.
We predict that the motion of polarizable objects inside a cavity, no matter
how slow, as well as their addition and removal from the cavity, will generate
a macroscopic, diverging number of low-energy photons. The significance of
these results in regard to the quantum measurement problem and the dynamical
Casimir effect are also discussed.
