Mach's Principle and Evolution of the Universe 
Within the framework of Mach's principle and of D.W. Sciama's physical
interpretation of it, a quantitative evaluation of the inertial mass as
a function of the density of the universe and of the epoch is obtained.
The calculation is somewhat similar to the solution of Olbers's paradox.
The result shows that the inertial mass varies as the universe expands
except for a flat, Euclidean universe. This leads to insights on the Principle