History Main / TimeDilation

* The AlanMoore comic TheBalladOfHaloJones deals with this in the war period of Halo's life. The planet Moab has such an extreme gravitational field that all the soldiers have to wear high pressure armor to fight. When the AmazonBrigade marches towards combat, the fight is frozen but gradually speeds up as they get closer to it, being at normal speed by the time they arrive. Every time Halo goes out on a mission for an afternoon, she misses another birthday. She ends up getting promoted this way, and she returns one last time to find that war ended months ago.

->''There once was a lady named Bright,''\\
''Who could travel much faster than light,''\\
''She set out one day,''\\
''In a relative way,''\\
''And returned on the previous night''
->--Arthur Henry Reginald Buller, of Punch Magazine

Time dilation is a scientific concept related to relativity which states, basically, that for an observer onboard a spaceship travelling at [[strike: a certain speed]] any speed at all (though only noticeable at appreciable fractions of the speed of light), time passes more slowly than it would for an observer on Earth. When near-lightspeed travel becomes involved, the effects become quite drastic: A person might go on a space journey that seems to him to last one year and, on returning, find that 10 years have passed on Earth. This is sometimes extrapolated by science fiction authors to apply to FTLTravel as well, though this would not necessarily be the case [[hottip:*:to the extent that science can make statements about the what would happen if something that science already says is impossible happens]].

* CharlesStross's Eschaton series has FTL travel allowing time travel (like the poem above), something that is [[http://www.theculture.org/rich/sharpblue/archives/000089.html generally accepted]] in physics circles.

* ''VoicesOfADistantStar'' averts this, but the novelization apparently doesn't.

* The twins paradox can be expressed as a variational principle that holds true for both general and special relativity: If an object travels between two events (i.e. points in space at a given time), and is not under the influence of an external force, the path it takes is the path that experiences the most time.
** For flat space-time, the path that takes the longest time is a straight line, confirming the Newtonian law of inertia that objects not under the effect of an external force travel in straight lines. Curved paths with the same endpoints all experience less time than the straight line path.
** For curved space-time (i.e. in the presence of mass) the straight line path is no longer the path that takes the longest time, since the path can "dip" into the gravitational field to experience gravitational time dilation and take a longer time (coincidentally making it seem like the object's path is being affected by gravitational force). In that way gravity isn't really a force in general relativity -- it's just subsumed into the law of inertia.

* MassEffect is notable for its rather impressive justification of this trope's ''absence'' - an object with [[http://en.wikipedia.org/wiki/Exotic_matter negative mass]] is not subject to relativity, and one of the [[MinovskyParticle primary attributes]] of [[{{Unobtainium}} Element Zero]] is its ability to lower the mass of objects to negative numbers.

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* GPS has a small correction for time dilation between the surface of the earth and up in space.

Examples using FTL:

There are a couple of quirks about real-world time dilation that also make it somewhat different from what you see in fiction:

Examples:

Time dilation is a scientific concept related to relativity which states, basically, that for an observer onboard a spaceship travelling at [[strike: a certain speed]] any speed at all (though only noticeable at appreciable fractions of the speed of light), time passes more slowly than it would for an observer on Earth. When near-lightspeed travel becomes involved, the effects become quite drastic: A person might go on a space journey that seems to him to last one year and, on returning, find that 10 years have passed on Earth. This is sometimes extrapolated by science fiction authors to apply to FTLTravel as well, though this would not necessarily be the case. Note that this effect occurs at considerably lower velocities as well, as an atomic clock on Earth and one in orbit around Earth will be ever so slightly desynced.

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* In {{Hyperion}} humanity has a way of circumventing this with portals. The problem is that you have to send relativistically fast ships out to build a portal at the other end, so the people sent to build them leave their whole life behind.

* The AlanMoore comic TheBalladOfHaloJones deals with this in the war period of Halo's life. The planet Moab has such an extreme gravitational field that all the soldiers have to wear high pressure armor to fight. When the platoon comprised entirely of TheSquadette walk towards combat, the fight is frozen but gradually speeds up as they get closer to it, being at normal speed by the time they arrive. Every time Halo goes out on a mission for an afternoon, she misses another birthday. She ends up getting promoted this way, and she returns one last time to find that war ended months ago.

* The AlanMoore comic TheBalladOfHaloJones deals with this in the war period of Halo's life. The planet Moab has such an extreme gravitational field that all the soldiers have to wear high pressure armor to fight. When the SoldierGirl squads walk towards combat, the fight is frozen but gradually speeds up as they get closer to it, being at normal speed by the time they arrive. Every time Halo goes out on a mission for an afternoon, she misses another birthday. She ends up getting promoted this way, and she returns one last time to find that war ended months ago.

Time dilation is a scientific concept related to relativity which states, basically, that for an observer onboard a spaceship travelling at a certain speed, time passes more slowly than it would for an observer on Earth. When near-lightspeed travel becomes involved, the effects become quite drastic: A person might go on a space journey that seems to him to last one year and, on returning, find that 10 years have passed on Earth. This is sometimes extrapolated by science fiction authors to apply to FTLTravel as well, though this would not necessarily be the case. Note that this effect occurs at considerably lower velocities as well, as an atomic clock on Earth and one in orbit around Earth will be ever so slightly desynced.

* Jump drive in C.J. Cherryh's AllianceUnion universe causes some time dilation, jumps take a week or less for the crew and a month or two for planetsiders and stationers. Of course, humans have to be sedated for jump and most other oxygen-breathing species are unconscious during jump.
* Some levels of hyperspace in the Uplift series.
* One more [[HyperspaceIsAScaryPlace scary thing]] about [[WarHammer40000 the Warp]] is that you can never tell when you will emerge. More than once a fleet has arrived centuries after departing.

** Which, to a physics student, sounds more impossible than travelling faster than the speed of light.
* In {{Hyperion}} humanity has a way of circumventing this with portals. The problem is that you have to build a portal at both ends in order to make it work.

* A musical example: Queen's "'39" is about a crewman on a spaceship who travels to a distant planet and returns after a year, only to discover that a hundred years have passed back home and only the descendents of his loved ones remain. It ends on quite a down note.

**One episode features a middle aged man who hires the bounty hunter protagonists to rescue his kidnapped parents, who's kidnappers had been travelling at very fast speeds for 50 years causing them to age only 8 months, meaning he's now twice their age.