Im watching some documentary on alien spaecraft, it was said that propulsion for one of these crafts would need an anti-gravity device. My first question is it even possible for an anti-gravity device to work according to the laws of physics. Second, if the field turned on you would need to generate -gravity to of set the current pull of gravity of the ship. Does that mean you also generate -mass to 0, and if so then shouldnt faster than light travel be possible? I guess what Im getting at is can mass exist that gives off zero gravity?