We examine Sciama's inertia theory: we generalise it, by combining rotation
and expansion in one unique model, we find the angular speed of the Universe,
and we stress that the theory is zero-total-energy valued. We compare with
other theories of the same null energy background. We determine the numerical
value of a constant which appears in the Machian inertial force expression
devised by Graneau and Graneau[2], by introducing the above angular speed. We
point out that this last theory is not restricted to Newtonian physics as those
authors stated but is, in fact, compatible with other cosmological and
gravitational theories. An argument by Berry[7] is shown in order to "derive"
Brans-Dicke relation in the present context.Comment: 10 pages including front one. New version was accepted to publication
by Astrophysics and Space Scienc