Why is the equivalence of gravitational and inertial mass so remarkable?
Yes, it is remarkable. Theoretically, inertial mass must be proportional to the gravitational mass. I hope there is no theory which proves the constant of proportionality equal to one. This is not mere conversion of units from one system to another system. Experiments show that the constant of proportionality is one. If it were NOT equal to one, we will have two different quantities in physics. In fact, two different branches of Physics; one explaining in terms of gravitational mass and another in terms of inertial mass will be followed. Mass is the base of all other derived quantities; we will have two base quantities for mass alone. The constant of proportionality being equal to one we do not differentiate inertia and mass. Like Einstein’s postulate that speed of E.M wave is independent of source’s speed, if any one finds the basic relation between inertial and gravitational mass, it will lead physics in different dimension.
