Aldaron, good example. (I hope that guy gets out of the way in time.LOL) Tachions if they exist might actually be used to push an object forward given the right circumstances, but as far as I know neither tachions nor gravitons have been confirmed as existing; it would seem, however, that some form of radiant energy would be given off by an object traveling at speeds approaching the speed of light whether tachions or some other form of energy (like radio waves). Whether tachions would push photons out of their way or not is a good question. I think that tachions would simply pass through other objects and even photons, but that is more of a feeling I get about it than anything else.