Does there exist a purely quantum mechanical carrier of the imprints
of gravitation? The motivation for considering this question arises
from the following historical scenario: Suppose a time traveller from
today visited Einstein in 1907, when he had the ``happiest thought of
his life'', just in time before Einstein actually started on the path
which led towards his formulation of gravitation (general relativity).
Suppose that this time traveller told Einstein about relativistic
quantum mechanics, about event horizons, and about Rindler's exact
spacetime coordinatization of paired accelerated frames. Would that
visitor from today have been able to influence the final form of the subsequent
theory of gravitation? Put differently, how different would the
course of history have been if Einstein had grafted relativistic
quantum mechanics and Rindler spacetime onto the *roots* of
gravitation instead of its trunk or branches?