Galactic empires are a common trope used in science fiction and science fantasy, particularly in space opera. Many authors have either used a galaxy-spanning empire as background, or written about the growth or decline of such an empire. The capital of a galactic empire is frequently a core world or home world.
Frank Herbert's Dune features hitherto disregarded desert-dwellers who due to a a powerful new religion expand to topple an old empire and build a new one.
The best known to the general public today is probably the Galactic Empire from Star Wars, which was formed in turn from the Galactic Republic.
Most of these galaxy-spanning domains depend on some form of transportation capable of quickly or instantly crossing vast cosmic distances (usually measured in light-years), many times faster than could photons at light speed. These invariably require some type of propulsion or displacement technology forbidden by Einstein's Theory of Relativity, or that otherwise relies on theories that circumvent or supersede relativity. (See: warp drive; hyperspace; Alcubierre drive.)
The term "galactic empire" has, no doubt because of association with the Empire from Star Wars, gained an unfavorable reputation. However, the Galactic Empires from Foundation and the CoDominium universe are relatively benign organizations; indeed, much of the plot of the Foundation series revolves around the issue of who can best and quickest revive the fallen galactic empire, it being taken for granted that this is a positive and worthy aim.
In many cases, the term "galactic empire" is misleading as it suggests a galaxywide empire. This is likely due to the once common tendency for fiction to either confuse galaxy and star system or to simply underestimate the size of the galaxy. While some of the noted fictional empires tend to encompass a large portion of the galaxy, many other empires may be classified as interplanetary or interstellar empires since they encompass only a local group of star systems. Note that even Star Wars' over-the-top Galactic Empire encompassed less than half of the Star Wars galaxy, according to the Expanded Universe materials.
Poul Anderson makes the point that the declining Empire depicted in his Dominic Flandry series does not span the entire Galaxy but only a fraction of one of its Spiral Arms - and still, it is vast beyond humans' ability to truly comprehend, and is in the process of collapsing under its own weight.
Famous quotes containing the words imperial and/or spy:
“Insensibility, of all kinds, and on all occasions, most moves my imperial displeasure.”
—Frances Burney (1752–1840)
“Living, just by itself—what a dirge that is! Life is a classroom and Boredom’s the usher, there all the time to spy on you; whatever happens, you’ve got to look as if you were awfully busy all the time doing something that’s terribly exciting—or he’ll come along and nibble your brain.”
—Louis-Ferdinand Céline (1894–1961)