Time travel

Despite Groening and Cohen's intentions, time travel has become quite common in the Futurama universe. Unfortunately the manner in which time is travelled varies between occurrences. This article examines all manners of time travel used and paradoxes that may or may not have been caused by them. Except in the case of time spheres; travelling backwards produces a new timeline if something is changed or leads to the current timeline if nothing changes.

Chronological
Chronological time travel is the simplest form, as it requires no technological involvement, everyone everywhere already travels through time at a rate of one second per second. Spending your time in a hole in the ground may provide the illusion of non-chronological travel to others. Technology for this has been invented however, such as the cryotubes that allowed Fry to reach the 30th Century and Farnsworth's attempted time machine from The Continuum Less Travelled.

Linear time vs. cyclical time
There is a debate whether time is linear or cyclical. Most scientists today believe it is linear and that when the universe cease to exist, it will remain that way. However, in "The Late Philip J. Fry", we are shown that travelling far enough forward in time will eventually send you back to the big bang into an identical universe, which indicates that time is cyclical in Futurama's universe and speculates that it could also be cyclical in ours.

Time skip
A time skip is a variation on chronological travel, wherein the time traveler continues moving forward through time at an uncertain rate but then forgets whatever happened before the skip began, no matter how mundane or life changing the event was. An unbalance in the level of Chronitons is known to cause time skips.

Forward travelling
Many scientists believe that while it is impossible to travel backwards in time, due to paradoxes and whatnot, it should be possible to travel forward in time. Farnsworth's forward time machine does just that, though Farnsworth fails to explain how exactly his time machine works, though the machine seems to subtly reappear every now and then in the real world so they can see what happens outside the machine, which means that the machine should travel forward in time by actually jumping through it.

Time tunnels and wormholes
A time tunnel is a tunnel to another location in space-time. On rare occasion, a tunnel can form naturally, when microwave radiation combines with the gravitons and graviolis from a supernova. Tunnels can also be formed by time machines, such as Adoy's Time Tunneller. Unfortunately, travel through these tunnels can cause paradoxes. It is possible that the tunnels are actually a variety of wormhole, although their openings do look different. Furthermore it isn't completely certain that wormholes in the Futurama universe allow for time travel under normal conditions, which admittedly the time tunnels are not examples of. The ball return wormhole seen in Into the Wild Green Yonder may have only taken the ship to another location in space, with the Nimbus having been repaired rapidly. It would also appear that the other wormhole seen in the movie will not take the crew to another time period.

Nexus point
Seen only once and poorly explained, a nexus point is a space-time location that can be visited by certain persons from any originating space-time location. Nexus Point travel apparently limits the traveller to visiting only the Nexus Point and after the time period of the Nexus, the traveller returns to the originating space-time. The word "point" is misleading in this case, as there is a starting time and ending time, it is likely there are limits to how far along the x, y and z axes the traveller can move as well. While the Fry of one timeline visited Nibbler, luckily he gave him enough information by the end of the available time to prevent the new timeline's Fry from being trapped in the Infosphere.

Time sphere
A time sphere, despite being "paradox free" actually produces far more paradoxes than any other type of time travel. While some of it makes sense, most doesn't. Travelling back in time doesn't produce a new timeline when something different has happened If it weren't being controlled by a god, this would be a serious mistake on the writer's part. However, apparently this particular god can only handle a certain number of these issues. It also seems to vary in it's determination of which being or object is a time paradox duplicate.

Time rifle
A time rifle somehow causes future and past incarnations of a person or object to be swapped. A broken rifle is able to bring multiple versions of a person into the time period in which the gun was fired. Anything that happens to the younger version will also have happened to the older versions.

Time vortex
Time vortices are vortices that randomly transport living creatures and objects through time, and are created by Chronitons. They can range in size and power, and are able to transport an entire planet's population.

Farnsworth Effect
Professor Farnsworth has discovered that the fluid keeping heads alive in jars is composed of crystalline opal that traps that head in a temporal bubble, and if it is ingested, the person will travel back to the head's era for a limited time. A brief lick lasts for several seconds while a large amount can go up to 24 hours. Interestingly, it also transforms the persons clothes, so they fit with the era, and changes them back when they return to the present.

Paradoxes and oddities
A paradox is when something that has happened appears to contradict another. This section attempts to solve identify and explain away paradoxes. While the solutions here may make sense, we can't confirm that these solutions are canon.
 * In "Roswell that Ends Well", Fry manages to solve the . The theory being that killing one's own grandfather before their parent was conceived would prevent them from having been born in order to go back in time and kill their grandfather, thus preventing their parents... Or more logically this would simply create an alternate timeline in which you never existed. You can then remain in the new timeline with your old life no longer accessible. In this case Fry "simply" ended up as his own grandfather. However he couldn't have always been his own grandfather, while the rest of his DNA can be traced to his mother and grandmother, his Y chromosome seemingly has no origin. If perhaps we looked at three timelines a solution can be found. In universe X, Philip J. Fry's grandfather is Enos Fry, he is not our Fry and probably looks different. He goes back in time and creates a new timeline, universe W, by killing his actual grandfather and impregnating his grandmother, the only DNA from Enos being a Y chromosome. On return to the future he is not recognised by anyone. At the same time the crew of universe W have also travelled through a time hole but arrive in 1947 slightly earlier splitting off into universe V. This is our not Fry, but he manages to provide the same DNA that Fry-X had provided, Crew-W head back to universe V's 31st century and no difference is noticed, crew-V had left through a time hole already.  This could continue indefinitely, each crew arriving slightly earlier to produce a new universe, in which their alternate selves don't arrive. Ultimately, one of these timelines would eventually have the crew living out their lives in the 1900s and Fry dieing of old age before meeting Mildred, and Enos would again be the parent - it wouldn't be timeline X, but the genetics would match.
 * Nibbler pushes Fry into the tube believing that he, or another version of him, will save the universe, it is possible that Fry-X, and any others who had a delta brain wave, convinced the crew to leave the planet and they wandered space until they eventually went through the time hole. These universes were later destroyed by the Brainspawn.
 * The Futurama game has a duplicate Planet Express Ship without origin, when the crew go on their journey on board a ship that is initially damaged, then later return to Earth before they left. The ship is damaged so they leave the damaged ship and take the good one. Each loop has Farnsworth repair or replace components of the ship, with the dark matter engine always being replaced. It is possible that each time a different set of components is replaced, putting them into a different universe each loop and giving each component of the ship different origins. In order to explain the overall origin, the first timeline would have had the ship undamaged at the start, but the crew still taking the good ship to go to Mom's office.
 * Fry's tattoo in Bender's Big Score has no origin and because there are no timelines created by time sphere travel it can't be explained as having been done originally in another timeline. However each tattoo meets it's doom on Fry's buttock, while the one on Lars is sent back, is duplicated and one is destroyed while the other goes back...

Appearances

 * As chronological time travel occurs in all media, instances are mostly omitted


 * - cryogenics
 * - cryogenics
 * - time skip
 * - time tunnel, chronological
 * - cryogenics
 * - nexus point, cryogenics
 * - time sphere, cryogenics
 * - forward time machine
 * - mentioned in title caption, chronological
 * - time tunnel
 * - what if scenario possible time tunnel
 * - chronological
 * - time vortex
 * - time vortex
 * - time vortex, chronological
 * - time rifle
 * - ; rules near enough to those of time tunnels
 * - ; rules near enough to those of time tunnels