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However, in SR where all objects move with constant speed wrt each other there are two (different?) types of masses. The invariant mass and relativitic mass

M=m/sqrt(1-(v/c)^2), M=relativitic mass, m=invariant mass

How does the two masses in SR relate to the gravitational mass=inertial mass (lets assume they are equal for simplification)?

For one thing is it possible to measure gravitational mass=inertial mass in flat spacetime since acceleration of the masses must be needed but disallowed.

But from reading Wiki it seems that inertial mass = relativistic mass

http://en.wikipedia.org/wiki/Relativistic_mass

http://en.wikipedia.org/wiki/Mass_in_General_Relativity

http://en.wikipedia.org/wiki/Mass