  The deep connection between entropy and information is discussed in terms of
both classical and quantum physics. The mechanism of information transfer
between systems via entanglement is explored in the context of decoherence
theory. The concept of entropic time is then introduced on the basis of
information acquisition, which is argued to be effectively irreversible and
consistent with both the Second Law of Thermodynamics and our psychological
perception of time. This is distinguished from the notion of parametric time,
which serves as the temporal parameter for the unitary evolution of a physical
state in non-relativistic quantum mechanics. The atemporal nature of the
`collapse' of the state vector associated with such information gain is
discussed in light of relativistic considerations. The interpretation of these
ideas in terms of both subjective and objective collapse models is also
discussed. It is shown that energy is conserved under subjective collapse
schemes whereas, in general, under objective collapse it is not. This is
consistent with the fact that the latter is inherently non-unitary and that
energy conservation arises out of time symmetry in the first place.
