okay... BASICALLY, our science teacher said that if something is hit by an object with kinetic energy (in inter-stellar space), then they will continuously move backwards with out any means to stop themselves, his example of this was throwing tennis balls at aliens... or something like that... APPARENTLY, the alien wont stop moving because there is no air resistance or gravity to take its energy, so the poor alien has to wait until it hits something... this is all Mr. Cartwrights fault... go blame him...