  A new approach to wavefunction collapse is prepared by an analysis of
semiclassical gravity. The fact that, in semiclassical gravity, superposed
states must share a common classical spacetime geometry, even if they prefer
(according to general relativity) differently curved spacetimes, leads to
energy increases of the states, when their mass distributions are different. If
one interprets these energy increases divided by Planck's constant as decay
rates of the states, one obtains the lifetimes of superpositions according to
the Diosi-Penrose criterion and reduction probabilities according to Born's
rule. The derivation of Born's rule for two-state superpositions can be adapted
to the typical quantum mechanical experiments with the help of a common
property of these experiments. It is that they lead to never more than two
different mass distributions at one location referring e.g. to the cases that a
particle "is", or "is not", detected at the location. From the characteristic
energy of the Diosi-Penrose criterion, an action is constructed whose
relativistic generalisation becomes obvious by a decomposition of the
Einstein-Hilbert action to the superposed states. In Part 2, semiclassical
gravity is enhanced to the so-called Dynamical Spacetime approach to
wavefunction collapse, which leads to a physical mechanism for collapse.
