http://tvtropes.org/pmwiki/pmwiki.php/Main/ReversePolarity

"Lewis did it! Oh, thank the gods for legitimate, fact-based science!"

Harley Quinn: [holding a raygun] Don't come any closer, or I'll... [reads label on her raygun] reverse polarity!

[odd look]

Harley Quinn: I don't know... but it always works on Star Quest. Gotham Girls , "Cold Hands, Cold Heart" [holding a raygun] Don't come any closer, or I'll... [reads label on her raygun] reverse polarity![odd look]I don't know... but it always works on Star Quest.

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When a major obstacle in a Science Fiction show is resolved purely through the judicious application of Techno Babble, the characters have successfully Reversed the Polarity. It seems that every futuristic gadget or space ship subsystem performs some miraculous function if only you route the power through it backwards. Urban legend has it the expression originated on Doctor Who. In reality, the phrase "Reverse the Polarity" can be traced back at least as far back as the 1898 War of the Worlds sequel Edison's Conquest of Mars by Garrett P. Serviss. However, it was popularized by Doctor Who, as Jon Pertwee asked the writers for a simple piece of Techno Babble he could reliably deliver. The version most associated with the Third Doctor is "reverse the polarity of the neutron flow", although he only said it once during his time as the Doctor.

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A type of Applied Phlebotinum, Reversing the Polarity is the be-all end-all technical solution for any problem. Usually only thought of at the very end of the show ("Captain... we could reverse the polarity of the positron toilet and send a stream of charged crap particles toward the Romulans, rather than away..."). It always works. Always.

Of course, you can "reverse the polarity" in real lifejust put the battery in the other way round. Doesn't quite have the same effect, though. Most simple powered toy vehicles, electric toothbrushes and other devices that rely on a spinning electric motor will simply run backwards while more complex electronics with a DC power supply may even break or fry the device in question. This is why most "complex" devices nowadays are equipped with diodes, which keep the current from flowing backwards if the polarity is reversed, preventing damage to the main circuitry. Still, Don't Try This at Home, kids! Don't even bother trying it with Mains power either: Alternating current means the polarity is already being reversed, 100 or 120 times a second depending on country. You'll notice that it doesn't make your hairdryer or vacuum cleaner go backwards.

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Reversing the polarity on a car is also possible—some vintage cars, particularly British ones, are positive-ground, while negative-ground has been the standard worldwide since The '60s, so if you want to put a modern MP3-compatible stereo in your '59 Morris Minor a car polarity swap is a must.

Besides, it makes the characters in question look a lot less like brilliant scientists when they are (basically) sighing and asking the technician, "Did you plug it in the wrong way again? I mean, seriously. Red cable is positive. How hard can it possibly be to remember?"

Of course you can't do this with neutrons, because they're as electrically neutral as the name suggests, although if we're getting technical, they do have a magnetic polarity. However, if the neutrons are flowing somewhere, reversing the polarity might refer to changing the direction of flow.

Closely related to the Forgotten Superweapon. Also see Technobabble and Revive Kills Zombie.

Compare to Tim Taylor Technology.

Examples:

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Anime and Manga

In episode 13 of Neon Genesis Evangelion, an angel, in the form of continuously-evolving Grey Goo, gets into NERV headquarters by hitching a ride on one of the EVAs. They then form themselves into an organic supercomputer, which starts to hack into the Magi supercomputers that run the headquarters. To prevent them from resulting in the self-destruction of the Magi, Ritsuko has to open them up, climb inside one of them, and reprogram it from the inside. The entire episode contains no actual EVA combat, and introduces entirely new Technobabble terms, most of which relate to the workings of the Magi.

The entire episode contains no actual EVA combat, and introduces entirely new Technobabble terms, most of which relate to the workings of the Magi. This once happened in Pokémon's English dub when Team Rocket tried to get hold of two Luvdisc, and then reverse the polarity to get rid of all of the love in the world. This being Team Rocket, it's pretty much an Affectionate Parody of the trope. The original version just has them wanting the Luvdisc captured for an ongoing Team Rocket project. In Pokémon: Jirachi: Wish Maker, Butler makes a machine that is supposed to create a live Groudon from its fossilized remains. When the machine creates an enormous evil monster instead, he is able to make the machine destroy Groudon by simply reversing the direction of the fossil and the levers.

Uchuu Senkan Yamato: This was how they got the drill-missile to unscrew itself out of the barrel of the Wave-Motion Gun.

In Transformers Victory, Braver invents a device that can detect Decepticon brainwaves. During the inevitable battle, he is able to drive them off by actually reversing the polarity.

Cowboy Bebop episode "Honky Tonk Woman": She reversed the polarity of one of the missiles! It's coming right back at us!

In episode 17 of the Sakura Wars anime, Kohran puzzles over how to make Iris's kohbu properly handle her vast spirit energies, and comes up with an idea that, among other things, reverses the flow of her spirit energy through the regulator crystal.

Comic Books

Film  Animated

In Cars 2, Holley says this while trying to escape a death trap in the Big Bentley clock tower. On one hand, they at least keep it grounded in reality: once reversed, the only effect is the clock's motor and gear system running in reverse. On the other hand, she does it by shocking the motor with a Taser...

In Transformers: The Movie, the heroes' ship is targeted by Decepticon missiles. Kup's solution is to reverse the polarity, like he did against the Shrikebats of Dromedan. Hot Rod is afraid it will tear the ship apart; instead it repels the missiles.

Film  Live-Action

Literature

Live-Action TV

Music

A popular filk song, "The USS Make Shit Up" by Voltaire, about the Star Trek series contains a similar line: "Bounce the graviton particle beam / Off the main deflector dish / That's the way we do things, lad / We're making shit up as we wish..."

A musical example is in Bob Carlton's — sorry, William Shakespeare's — Return to the Forbidden Planet. Before the show starts, the 'crew' or ensemble members walk out and instruct the audience in standard safety procedures for their flight (air masks will deploy from ceiling, use of cell phones will cause the ship to explode, etc.) and end with teaching the audience how to Reverse Polarity themselves — only for an emergency situation, which is highly unlikely, nigh impossible — by putting their hands on their heads and twisting their torsos and heads to and fro. In Act II, of course, polarity needs to be reversed ("But it's not logical!" "Damn your logic! I've got lives to save!") and the audience has to help. As an added bonus, at the end of the show, as the crew and captain prepare to launch back to Earth (singing Born to Be Wild, of course), crew members announce that all is well by calling "Iambics functioning, Pentameters locked in, Hyperboles all off the scale!" and "R.S.C. jettisoned", in jokes all relating to Shakespeare's text, a conceit of language, and the Royal Shakespeare Company, respectively. Many of the posters (and T-shirts) for the show consist of a warning sign saying "WARNING: Do not reverse polarity!", and the playbill warns of the dangers of polarity reversal in space. Note that it is never actually specified what the polarity is reversed on, just that polarity in general is reversed - which makes the joke even more tongue-in-cheek...

Pops up in the Rush song "Vital Signs" . A tired mind become a shape-shifter/everybody need a mood lifter/everybody need reverse polarity

.

Radio

Lampshaded nicely in the Doctor Who BBC Radio drama The Ghosts of N-Space, in which the Brigadier jokingly suggests that the (Third) Doctor "Reverse the polarity of the neutron flow", to which the Doctor replies that the Brig knows as well as he does that the phrase is meaningless.

The Torchwood radio play "Lost Souls" plays this trope entirely straight, with the world saved from disaster by reversing the polarity of the positron flow. CERN apparently approved the science, and the impression is the writer was delighted to have found a context where the phrase actually made sense.

Tabletop Games

According to the Star Trek d6 RPG sourcebooks, reversing the polarity in different ways on the main deflector array can create a low power phaser, force someone out of warp, and allow you to basically do ANYTHING you could think of. The Main Deflector Array; Swiss Army Weapon of the Federation. In fact players are encouraged to come up with Techno Babble explanations for whatever it is they are trying to do.

Magic: The Gathering made a card for "Reverse Polarity"—any damage taken so far that turn from artifacts is retroactively added to your health total. Lampshaded, but most certainly not explained, in that the picture shows a mace acting as a Healing Shiv. The Yu-Gi-Oh! card game has a similar card: Rainbow Life.

Paranoia adventure "'The Yellow Clearance Black Box Blues''. The Maxwell-Effect Moleculokinesic Field Device is basically a Pyrokinesis gun (e.g. it acts like a flamethrower). 50% of the time it fires at reverse polarity and freezes the target.

Ghostbusters RPG adventure Hot Rods of the Gods. If a Ghostbusters fires his proton pack at Meera at the same time as Meera shoots at him with the red devolvo ray, it will reverse the polarity. The devolvo beam will affect Meera and the Ghostbuster will evolve into a superior being with increased intelligence and a large head.

Toon supplement Tooniversal Tour Guide, "Atomic Monster Theater" setting. Professor Doug Graves can reverse the polarity of his portable razor and create a vibration to drive a Giant Potato Bug back into its cave.

SPI's Universe. When a psionic navigator wants their ship to make a hyperjump, they concentrate on the destination and encode their thought patterns on a plate of magnetic monopoles. This reverses the polarity of the monopoles and causes the ship to jump to the chosen destination.

Theatre

Return to the Forbidden Planet has an audience participation moment when it's necessary to Reverse the Polarity of the Klystron Generator. A highly dangerous procedure. The UK touring version of the show included a large neon sign saying "Do Not Reverse Polarity" as part of the set. The cast would also mingle with the audience before the show began, giving instructions on how to perform the polarity reversal procedure.



Video Games

Webcomics

Web Original

Western Animation

Real Life