Our Time Travel Is Different

""I'm standing at the time portal, which scientists say, follows 'Terminator' rules. That is, it's one way only and you can't go back. This is in contrast to, say, 'Back to The Future' rules, where back and forth is possible, and of course 'Timerider' rules, which are just plain silly.""

- Reporter, South Park

What does Time Travel look like? Well, no one knows (as far as we know anyway), but fiction has given us four models, each of which may or may not involve a Time Machine. (These concepts are not to be confused with the different fictional interpretations of Temporal Mutability).

Videocassette Time Travel: According to this theory, time is like a videocassette (for those of you born after 1995, videocassettes are what we played movies on back in the dark days before DVDs). Normally, time is on "play" and traveling backwards or forwards is like pushing "rewind" or "fast-forward". This theory originated in H.G. Wells' The Time Machine (which obviously predated the videocassette, but it's still a good analogy).

It is, of course, presumed that you're invisible (and intangible) while traveling through time in this manner, i.e. people on the outside don't see someone standing around for years and years while moving very slowly. Modern works take this for granted, but H.G. Wells actually gave it a Hand Wave, essentially explaining that the traveler is going through time too quickly to be seen. (This doesn't quite explain how the traveler isn't solid, but never mind.)

If one is only going forwards, then this version resembles one the most scientifically plausible means of time travel, namely, accelerating fast enough for Time Dilation to be noticeable. (Of course, since you're actually accelerating, you'll only be able to see the "fast-forwarding" of very distant large object, like a galaxy, and your vision will be modified too, so it's not really anything like this model.)

Examples of this version of time travel:
 * As mentioned, H.G. Wells' The Time Machine and all film adaptations thereof.
 * The film version of Harry Potter and the Prisoner of Azkaban (but not the book).
 * Somewhere in Time (1980 film)
 * The book The Magic School Bus in the Time of Dinosaurs. Absurdly, the TV adaptation used this theory for the trip back in time, but switched to the one below for the return trip. Even stranger, the fossilized dinosaur egg became a normal egg (as in feasibly hatchable or edible), yet none of the humans on board disintegrated from aging backwards millions of years.
 * The book Sonic The Hedgehog in the Fourth Dimension (also involves time machines using the two methods described below, but quite a few pages of narrative go into describing a trip made using a time machine using this method).
 * Braid used a more efficient form of the one used in Prince of Persia Sands of Time.
 * The eponymous character of Bunny Must Die similarly uses this except she has pause and slow as well.
 * At the end of Stargate SG-1, Teal'c is sent back in time through this method, to impart the solution to the problem of the Ori's ability to track the ship with the Asgard memory core (the Odyssey). The solution is on a memory crystal, which when inserted, prevents the Ori from tracking the ship.
 * The Butterfly Effect actually uses this analogy to allow the Main Character to revisit his memories; and then later change them.
 * This is how time travel works in Jasper Fforde's Thursday Next Series, but here you can also pause and loop.
 * While Thursday only gives us an up-close view of this type of time travel, the Chrono Guard's repertoire seems much more extensive. Their office is something akin to this in reverse, and vague references are made to "The Cone", something around which Time Agents navigate... somehow... adding an element of wormhole time travel. You never even get an idea of how things like the Echo!Friday or the tech mining work, and you aren't meant to. Fforde's time travel depicts how utterly incomprehensible extensive time travel would be to the uninitiated.
 * In Futurama, Farnsworth made a time machine that acted this way, although it could only go forward in time. The machine was completely unaffected by outside events, such as explosions.

Wormhole Time Travel: The theory here seems to be that going back in time immediately puts you in another dimension. Usually, this dimension will be some kind of wormhole or "time tunnel" composed of flashing lights and cool special effects. You may even see images from famous moments in history fly by as a helpful gauge of when you're going. In less serious versions, the tunnel may be decorated with clocks and calendars or be labeled with years. Depending on the story, the wormhole links the user to a different spot on his own timeline or to a different spot on the next timeline over; the difference is largely academic.

Examples of this version of time travel: "Calvin: You could help me drive, you know! If we miss our exit, we could fly right into the big bang!"
 * Doctor Who's Time Vortex.
 * Bill and Teds Excellent Adventure
 * Farscape ,the Wormholes cross space and time.
 * The book version of Harry Potter and the Prisoner of Azkaban (but not the film).
 * As the title suggests, the 1960s TV show The Time Tunnel.
 * The End of Eternity has a parallel "timeless" dimension.
 * In Stargate SG-1, the Stargates have twice been used for time travel (also seen in Atlantis and the SG-1 movie Continuum). It's unclear whether or not this counts since wormholes are a regular fixture of Stargate travel anyway.
 * Mario & Luigi: Partners in Time.
 * The Legend of Zelda Majoras Mask.
 * Teenage Mutant Ninja Turtles Turtles in Time had a mostly black version that they blipped through.
 * One issue of Count Duckula had a wormhole made of rings labeled with years.
 * Chrono Trigger
 * Futurama when it's as a result of combining microwaves and radiation from a supernova. They even ended up with a bunch of clocks on board.
 * Day of the Tentacle "This must be that Woodstock place Mom and Dad are always talking about!"
 * TRU-Life Adventures
 * Superman, before 1985, could do this under his own power.
 * Time Bandits used "time holes".
 * Tsubasa Reservoir Chronicle, where the characters actually thought that they were going to an alternate universe (as they usually do) until The Reveal several arcs later.
 * Ecco the Dolphin. It's clearer in Defender and the special cutscenes in the CD version of Tides.
 * In Sluggy Freelance Timeless Space works like this, after a fashion. No one ever intentionally uses it for time travel, but someone who enters and then leaves Timeless Space can return to the regular universe centuries before or after they left.
 * Mainly because leaving Timeless Space is handled by
 * Mirai Sentai Timeranger and to a lesser extent Power Rangers Time Force when summoning the Combining Mecha.
 * In the case of Power Rangers, It has always used "time hole" time travel since season 2.
 * Star Trek the Original Series had the Guardian of Forever.
 * Inuyasha. The well is the wormhole.
 * In the Haruhi Suzumiya novels, Asahina's time travelers's method and Nagato's "emergency escape program" seems to be of the "special effects" variety, but it makes Kyon much too dizzy and nauseous to actually look beyond taking quick peeks, which he doesn't understand; this arguably makes it both Wormhole Time Travel and Unseen Time Travel. Asahina and Nagato don't seem to have that problem, but we don't know for sure either.
 * Calvin and Hobbes uses this, which Calvin compares to traveling on a highway:


 * Godzilla vs. King Ghidorah uses a variant of this; when the characters time-jump everything around seems to speed up or reverse like in videocassette time-travel, but a few moments later they enter a tunnel of crazy psychedelic special effects and arrive at their destination.
 * While it also includes Instantaneous Time Travel, the Yu-Gi-Oh Tenth Anniversary Movie briefly shows Paradox coming out of a portal.
 * Yu-Gi-Oh 5 Ds: The Infinity Device is capable of creating wormholes.
 * In Universal War One, the main cast time travels because of the opening/closure of a wormhole.
 * Seven Days uses this one; different from others in that the protagonist needs to steer ("fly the needles") in order to land on Earth. Even with his better than average ability, his time machine still winds up miles away from where he left.
 * The comic book Major Bummer used the less serious version, with moments from history flying by on two dimensional "shards" of time, one of which ends up impaling a character.
 * Septimus Heap: The time travel through the Glasses goes through an intermediary dimension that, if the paired arrival point Glass is lacking, can dump you into a place where there is no time at all.
 * Sonic CD
 * Puella Magi Madoka Magica:.
 * The Girl Who Leapt Through Time: Actually plays with both Worm Hole and Instantaneous travel. Makoto's first leap she goes through a very strange occurrence, all subsequent leaps after are instant.

Instantaneous Time Travel: Who says you need to see anything when you go back in time? Used in the Back to The Future films, this is where time travel is simply instantaneous. One second Marty McFly is in 1985. Then there's a flash of light and he's in 1955. Simple as that.

Examples of this version of time travel:
 * As mentioned, the Back to The Future series.
 * In the DVD extras, the director tells us that they created an elaborate visual sequence for time travel, putting it under the previous version. Then they decided that time travel wouldn't have any such visuals.
 * Isaac Asimov's Pebble in the Sky has an excellent example.
 * Stargate SG-1 used this version with the time-traveling puddle jumper in "Moebius". Another time-traveling puddle jumper (or possibly the same one) appeared in the Stargate Atlantis episode "Before I Sleep".
 * The Legend Of Zelda The Ocarina Of Time.
 * The Journeyman Project from the second game onward. The noise and purple lightning when someone departs and arrives via this sort of time travel is handwaved as a phenomenon called "displacement effect", caused by the amount of matter in the universe being added or subtracted by the time traveller. The "time tunnel" shown in the first game more resembled a screensaver with the Playstation controller icons than anything else, and was wisely removed.
 * The Mental Time Travel on Lost were instantaneous.
 * A straighter example of instantaneous time travel was seen in the first half of season five, albeit not by choice and causing loads and loads of painful headaches and fatal nosebleeds. And was actually seen as.
 * Its Not Like That Darling has instantaneous, no-flash (no air displacement either, for that matter) time travel.
 * In Back to the 50s, S Club travel back in time 40 years simply by driving through a shimmering thing on the road, in a car which seemed to be self-aware just after the amount of distance it have driven went over one million miles.
 * Red vs. Blue. The very first instance of time travel is the latter version, since it occurs during a huge explosion that knocks all the characters out and then waking up in the future, except for Church who's in the past. Every other instance somebody goes back in time though, it's instantaneous.
 * Kim Possible, A Sitch in Time
 * In Quantum Leap, Sam arrives and leaves via an impressive special effect, but the final episode points out that this version applies in reverse: Sam sees what may be another leaper depart, and isn't sure what he just saw. He later explains it to Al, who also can't be sure -- neither of them has seen what a leap looks like. This implies instantaneous, since Sam is conscious when he leaps...
 * The Cassiopeia in Mahou Sensei Negima seems to function like this.
 * Primeval has The Anomalies, big glowing balls of timey wimey stuff, step into it and find yourself in the past or future instantaneously.
 * In Wyrd Sisters, it's mentioned that people expect videotape-style time travel, but what they actually get is this.
 * In the Suzumiya Haruhi novels there is one instance of Nagato sending Kyon and Asahina three years forward in time in what Kyon experiences as an instant.
 * In the Yu-Gi-Oh Tenth Anniversary Movie, the time travellers' motorbikes glow brightly, then they speed up and disappear in a flash of light.
 * In The Time Traveler's Wife, this is how Henry, travels through time. Unfortunately, he can't control it.
 * This is just about how it works in Sonic CD; it would be more instantaneous except for the time required to load the next level, which uses a visual effect that suggests the Wormhole method, but when Sonic appears in the past or future, his momentum is conserved from whichever time period he left, making it clear that it's meant to be instantaneous.
 * This is how time travel works for units in Achron. For the player, in practice it is something of this and Mental Time Travel combined, though what is known of the fluff suggests it is somewhat more complicated.
 * This is how the Time Matrix works in Animorphs
 * Seems to be how time travel works in Homestuck. Both Dave and Aradia just spin their timetables/time music boxes and appear at their destination time.

Unseen Time Travel: This covers all instances where the time travel occurs off-screen. Often a form of Mental Time Travel. For example, if you fell asleep and then woke up to find yourself in The Middle Ages. Another variation of this occurs if all the audience ever sees is the traveler leaving from and arriving in various times, i.e. the traveler's point of view is never shown. Either way, it's impossible to determine which of the above theories is in place.

Examples of this version of time travel:
 * A Connecticut Yankee in King Arthur's Court
 * George "Yankee" Longago, an obscure Golden Age superhero, had the power to travel through time while asleep, usually based on his subconscious desires.
 * In Time and Again by Jack Finney, the protagonist surrounds himself with objects from The Gay Nineties while living in a Victorian Penthouse overlooking Central Park; by imagining himself to be in the 1890s he wakes up one day and is in the 1890s.
 * Robert Sheckley's Time Killer has something approaching this.
 * This is also used, sometimes as Applied Phlebotinum, but also for comedic effect, with Paradox, on Ben 10 Alien Force. Paradox has almost complete knowledge of the Timey Wimey Ball.
 * The manga Little Jumper arguably uses this. Time machines make all kinds of fuss on-camera when they get to where they're going, but we have yet to see the travelers' perspective.
 * In Split Infinity (the movie, not the novel by Piers Anthony), the main character falls from a barn loft in 1992 and wakes up as her great aunt in 1929.
 * In Primer, the time machine is a solid box which you have to stay inside for the duration of the trip. One character mentions that he heard a sound like the ocean -- it's unclear whether that was just the machine or not.
 * Presumably it's the ambient sound in the room, but backwards.
 * In this context, "for the duration of the trip" means that if you turned the machine on 12 hours ago, you have to sit in the machine for 12 hours. Staying in the machine too long, or leaving early, is implied to cause major health problems.
 * A strange example from the Nasuverse: time travel is said to be a True Magic ("impossible miracles") and is brought up by a character mentioning ways to revive from death. However, there is no character who can use Time Travel in Canon, as there are basically only five users of True Magic.
 * Used in Black Knight.
 * Used in an episode of S Club 7 in Miami (aka Miami 7), where the group went into fog on a boat in the Bermuda Triangle and fell unconscious, waking up in the 80s with clothes from that time. They regained their original clothes when they re-entered the fog to go back to their own time, except for Hannah, who kept her 80s shoes for reasons that were never explained.
 * Mental Time Travel such as that found in Groundhog Day usually goes under this category.
 * In Suzumiya Haruhi novels, whenever Kyon is time traveling, he has to close his eyes because it makes him so sick he could puke. The reader doesn't learn much of what is happening, but the hints sound like a version of Wormhole Time Travel.
 * A Season 4 episode of Supernatural, "In The Beginning": one second, Dean is in 2008, and then Castiel . We don't ever see how they travel there.
 * Sapphire and Steel just arrive at whatever place and time their assignment is set, usually walking in through the front door. However, at the end of Assignment 2, we see Steel jump into the air and vanish, but, like many things in this show, it's never explained if this happens all the time or even if they're time-travelling or just moving between dimensions, so...
 * Harry Turtledove's Alternate History novel Guns of the South has time travel via square platforms that apparently dematerialize the user in a fashion similar to Star Trek transporters. We only ever see them in use once, as
 * "Billy Pilgrim has come unstuck in time," meaning that he lives his life out of order, but there are no discernible time travel moments or effects.
 * Captain Picard time-travels this way in "All Good Things...", the finale of Star Trek the Next Generation.
 * In Umineko no Naku Koro Ni, Ange is split / time travels when she jumps off the roof of the hospital, but there is no detail given as to the process by which she actually does it, since the third installment ends with her jumping off the roof, and the fourth installment begins with her already in the meta-world. Granted, of course, that the meta-world itself is outside of the time-space continuum.
 * The Planet of the Apes variety could be number 3, but as it's never shown, we can't say for sure. It's not one or two, though, based on some of the dialogue from Escape.
 * Groundhog Day Phil wakes up in a Groundhog Day Loop