Galactic empires are a common trope

Trope (literature)

A literary trope is the usage of figurative language in literature, or a figure of speech in which words are used in a sense different from their literal meaning...

 used in science fiction

Science fiction

Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...

 and science fantasy

Science fantasy

Science fantasy is a mixed genre within speculative fiction drawing elements from both science fiction and fantasy. Although in some terms of its portrayal in recent media products it can be defined as instead of being a mixed genre of science fiction and fantasy it is instead a mixing of the...

, particularly in space opera

Space opera

Space opera is a subgenre of science fiction that emphasizes romantic, often melodramatic adventure, set mainly or entirely in outer space, generally involving conflict between opponents possessing advanced technologies and abilities. The term has no relation to music and it is analogous to "soap...

. Many authors have either used a galaxy

Galaxy

A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...

-spanning empire

Empire

The term empire derives from the Latin imperium . Politically, an empire is a geographically extensive group of states and peoples united and ruled either by a monarch or an oligarchy....

 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

Dune (novel)

Dune is a science fiction novel written by Frank Herbert, published in 1965. It won the Hugo Award in 1966, and the inaugural Nebula Award for Best Novel...

involves hitherto disregarded desert-dwellers creating a powerful new religion and burst out to topple an old empire and build a new one.

The best known to the general public today is probably the empire from Star Wars

Galactic Empire (Star Wars)

The Galactic Empire is one of the main factions in the fictional universe of Star Wars. It is a galaxy-spanning regime established by the series' lead villain, Palpatine, to replace the Galactic Republic in Star Wars Episode III: Revenge of the Sith. The Galactic Empire is introduced in Star Wars...

, which was formed in turn from the Galactic Republic

Galactic Republic (Star Wars)

The Galactic Republic is the name of the interplanetary State used in the fictional Star Wars universe prior to the establishment of the Galactic Empire. The form of this government, created by the Senate, was introduced in the Prequel Trilogy. By the time of the original Star Wars trilogy, it is...

.

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-year

Light-year

A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...

s), 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

Theory of relativity

The theory of relativity, or simply relativity, encompasses two theories of Albert Einstein: special relativity and general relativity. However, the word relativity is sometimes used in reference to Galilean invariance....

, or that otherwise relies on theories that circumvent or supersede relativity. (See: warp drive; hyperspace

Hyperspace

Hyperspace may refer to:*in mathematics and general science** A Euclidean space of dimension greater than three, see fourth dimension and higher dimensions ** Space of any dimension, whether lower, higher, or...

; Alcubierre drive

Alcubierre drive

The Alcubierre drive, also known as the Alcubierre metric, is a speculative, but valid solution of the Einstein field equations. It is a mathematical model of a spacetime exhibiting features reminiscent of the fictional "warp drive" from Star Trek, which can travel "faster than light", although...

.)

The term "galactic empire" has, no doubt because of association with the Empire from Star Wars

Star Wars

Star Wars is an American epic space opera film series created by George Lucas. The first film in the series was originally released on May 25, 1977, under the title Star Wars, by 20th Century Fox, and became a worldwide pop culture phenomenon, followed by two sequels, released at three-year...

, gained an unfavorable reputation. However, the Galactic Empires from Foundation and the CoDominium

CoDominium

-The CoDominium series:*A Spaceship for the King *He Fell into a Dark Hole *The Mote in God's Eye...

universe are relatively benign organizations.

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.