Explaining mass as a variable-no printing

Remember this: if you stay with a body ( or particle ) of possessing mass, called proper or rest mass, the amount of mass is constant! Common sense.

It is only when you are stationary and stand back, so to speak, and then measure the amount of mass a moving body ( or particle ) has, that you will both observe and hence measure different amounts of mass directly related to the velocity of the passing body of mass!! And, logically, different observers at different positions in spacetime will simultaneously measure different amounts of mass of the exact same body possessing mass. 

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