All Theories Are True

The Sci Fi Counterpart of All Myths Are True, this is when long-obsolete, fringe, or disproven scientific theories are considered true for the purposes of either Rule of Cool or Art Major Technology. Examples should be distinguished from Science Marches On, as in this trope's case the use of dodgy science is quite deliberate. This is sometimes a supertrope of Ancient Astronauts, Lamarck Was Right, Genetic Memory, Psychic Dreams for Everyone and many other tropes found right here on this wiki, and arguably underpins most modern uses of alchemy in Speculative Fiction. It's also rampant in Steampunk, which is often set in universes where, for example, the theory of the aether is true.

The trope comes in one of two flavors: Obsolete science may be used to evoke associations with the past in a manner resembling Zeerust Canon; alternately, fringe or obsolete science may be used to evoke the notion that all manner of far out ideas are really true in this particular fictional universe. More generally, it covers fringe or obsolete scientific concepts that are just part of a story's premise and aren't used to evoke anything.

It does not include plain bad or mistaken notions of the You Fail Science Forever sort, though it can be hard to tell sometimes. The criterion for inclusion on this list is that the concept involved is a real fringe or obsolete theory meant to explain an already-observed phenomenon that the work treats as true for reasons of premise or style. In other words, the explanations are speculative or obsolete; the phenomena explained are, however exaggerated, real.

The title of this trope is somewhat inaccurate. A Theory is actually something that has been proven and has been comprehensively explained. A Law is something that has been proven but has not been explained. This Trope refers to Hypotheses, predictions which are then tested to become Laws or be invalidated.

Real Life examples abound, of course, but should be avoided unless they have been the basis of fictional works or story premises.

Comic Books

 * Grant Morrison loves treating fringe science claims as true in his comics, whether it's the "morphogenetic field" in Animal Man or Masaru Emoto's theory that water has feelings coming true in a chapter of Seven Soldiers.
 * Lampshaded in an issue of Alan Moore's Tom Strong, where the hero and villain reminisce about a 1930s adventure and are disturbed that phlogiston, invisible liquid heat, was real then... despite having since been disproven as a theory.
 * What was more disturbing was how the villain somehow managed to invent a way to create phlogiston, despite the idea being bunk.

Literature

 * Discworld has a lot of fun with fringe science. Most notably the way the word "quantum" can be used to justify anything, and the morphogenic field. (GURPS Discworld notes that all theories of morphic resonance are true on the Disc, including the ones that contradict each other).
 * Not to mention the whole "the world is flat" thing, y'know?
 * Animorphs used this trope sometimes. In the case of Area 51... I mean, Zone 91... it was heavily Lampshaded. It was more moderately lampshaded when an Atlantis-type lost civilization turned out to be real. And there are also the Skrit Na, whose main purpose for being in the books was to be an alien race fitting the description of The Greys. Subverted, though, when Erek is telling the story of how his Chee race arrived at the right time to be Ancient Astronauts. When asked about the concept that they might have been the ones to design the pyramids, Erek clarifies that the Chee didn't interfere with human society in ways like that, just as they don't do things like that in the present day. Also, the series' treatment of psychic phenomena, and of the question of dolphin and whale intelligence, seems to be based on this trope.
 * Other Songs, a not-yet-translated novel by Polish author Jacek Dukaj, is set on alternate Earth where Aristotle was right.
 * Stationery Voyagers was inspired in part by theories about a universal wall, that the universe is shaped like an inverted onion, that misplaced blue shifts in certain cosmos that conflict with universal expansion indicate a galaxy "bouncing off the wall," and theological hypotheses of Heaven and Hell as Another Dimension. It runs ape wild with these ideas.
 * But the concept of spaceships having pseudo-gravity generators still eludes the premise, and Faster-Than-Light Travel is outright rejected for all non-supernatural beings.
 * Several short works by Hugo-winner Ted Chiang follow this formula, including one in which the tower of Babel does in fact reach the sky (Tower of Babylon), and another exploring the ultimate consequences in a world where the preformationist hypothesis is accurate (Seventy-Two Letters).
 * Kate Elliot's Crown of Stars series is set in a world in which the Peripatetic theory of a geocentric universe within a series of nested crystal spheres in which are contained the stars and the planets is true. It is still possible to go to the stars, although obviously the experience is a much different one. One character actually speculates on what, in the world of the story, is the fringe theory that the universe might be a heliocentric one in which the stars and planets float in a vacuum, but rejects it.

Live Action TV

 * The X-Files uses the premises of innumerable fringe and obsolete theories as the premises of episodes and the show's sprawling Myth Arc. A partial list:
 * "Space" - The Face on Mars
 * "Eve" - Human clones and bioengineering.
 * "Gender Bender" - Human sex pheromones.
 * "Young At Heart" - Genetic engineering and animal gene-splicing.
 * "Sleepless" - Lack of sleep makes you crazy - and psychic.
 * "Firewalker" - Silicon-based life.
 * "Dead Kalm" - Free radicals theory of aging.
 * "Humbug" -  fetus in fetus.
 * "Soft Light" - A man's anti-matter and/or dark matter shadow kills people.
 * "Jersey Devil," "Quagmire," "Detour," and many others - Cryptids
 * "Wetwired" - Brainwashing via television signals.
 * "Home" - Inbreeding.
 * "Teliko" - Pineal Weirdness
 * "El Mundo Gira" - Bizarre rains with an alien enzyme.
 * "Unruhe" - Spirit photography.
 * The show also used most of UFO lore, especially the Roswell and Grey aliens theories.
 * A notable Spiritual Successor, Fringe also uses this trope as its premise.
 * Ditto the short-lived series Dark Skies, based on UFOlogy and other 1960s Conspiracy Theory lore.
 * In Sliders, the existence of the Kromaggs (humanoid creatures that evolved instead of Homo sapiens in various parallel universes) is ascribed to "Killer Ape Theory," which was a theory held by many 19th century naturalists about early human evolution. Notable in that in the real world, Killer Ape Theory tried (very inadequately) to explain the divergence between humans and the other apes, in the show the theory was appropriated to explain the divergence between Homo sapiens and Kromaggs from a common stock. And guess where the name "Kromagg" comes from?

Tabletop Games

 * The Spelljammer setting for second edition Dungeons and Dragons, while fantasy, used such ideas as worlds being surrounded by crystal spheres and floating in phlogiston.
 * A big part of the Sons of Ether brand in Mage: The Ascension is science that go beyond conventional ideas of the "possible".
 * Wonders look like they work this way in Genius: The Transgression however if you dig deeper it's really a combination of actual science and Mania.
 * This is also one of the noted problems of Lemurians and their Brahmins. A Genius can easily cite any scientific theory, bunkum or backed-up, for why their device works, but the members of the Peerage have some understanding that what they're doing is not quite science. The Lemurians, on the other hand, believe that something went wrong with the standing model of the universe, and want to try to "fix it" to support their theories.
 * It's also how Bardos work. A theory of the universe is proven to be untrue? Then it simply spins off into an alternate dimension where it is. Certain Bardos include a model of the universe where the planets are crystal spheres pushed through seas of aether by gigantic archangels, a dystopia that demonstrates both the failures and successes of Soviet totalitarianism, a Barsoom-like vision of Mars that came into existence when the Viking rover pictures came back, and the Hollow Earth, which is populated by both every sort of prehistoric creatures and Nazis.
 * This is the basis of the GURPS supplement "Fantasy Tech". Everything from the the popular belief that ancient armor was ridiculously heavy to the scientific fact that the sun exerts a strong natural attraction on dew, so if you fill bottles with dew during the night you will rise upward during the day.

Video Games

 * In Rise of Legends, helicopters follow Leonardo Da Vinci's "aerial screw" drawings, long since proven aerodynamically impossible.
 * Command & Conquer: Red Alert previously used Tesla Coils as death rays. Though it used to be thought this was possible, it isn't.
 * The Fallout series.

Web Comics

 * "Gaslamp fantasy" Girl Genius is all about this, but then, at least one character states that a strong spark is actually a Reality Warper.