Intergalactic travel

Intergalactic travel is travel between galaxies, and is considered much more technologically demanding than even interstellar travel. At the speed of light, travelling from Earth in the Milky Way galaxy to the Andromeda Galaxy (the nearest major galaxy) would take roughly 2.5 million years (a distance of 2.367x10^22 meters) from the perspective of observers on Earth, but would take an arbitrarily short amount of time for the traveller (due to the effects of time dilation), depending on exactly how close to the speed of light the vessel is traveling, perhaps a few decades ship's time.

In engineering terms, intergalactic travel is considered pure science fiction. Because of the enormous distances, intergalactic travel is extraordinarily impractical because of the need for much more advanced propulsion methods than are currently thought possible. Even if these issues were solved, navigating a spacecraft across such great distance would require a much deeper understanding of galactic coordinates and position and also a way not just to slow it down upon reaching its target but also to find exactly which star, planet or body to orbit or reach. If its an unmanned probe, it can take millions of years just to receive the transmission of any information which is restricted to the speed of light.

Another concern for intergalactic travel would be that by the time a spacecraft could reach another galaxy, much more advanced propulsion technologies would likely have been created on Earth, meaning that it would be more efficient to simply send another spacecraft traveling at faster speeds. Each time a new mission is launched, it would soon become obsolete.

Science fiction frequently employs speculative concepts such as wormholes and hyperspace as more practical means of intergalactic travel.

See also

• Intergalactic space
• Faster-than-light