What ive learned is that when going at a fraction of C, the energy put into the acceleration is transferred into mass. However what is strange is that its gravitational strength does not increase. People keep saying that gravity is a property of the invarient mass and that alone. So then where does that energy go to? For all that is concerned, and increase in mass without an increase in gravity is like adding 1 to infinity. This then means that any mass increase does not increase gravitational strength, thereby concluding that: A) Gravity is a property of n number of particles, rather than a term of mass (Since then all similar fundimental particles would have similar masses) or B) Gravity is not a property of matter.