For as long as people have looked in the sky, they have imagined extraterrestrial civilisations populating the planets around other stars. The idea of interplanetary empires has already entered the realm of science-fiction and many writers of the genre have even elaborated on such empires. The reality may be otherwise. Is it possible that an Alien civilisation could have really established
... [Show full abstract] colonises outside its own star
system ? This paper will make a survey of possible motivations and technological capabilities, within the reality of Physics, for the establishment a interstellar empire.