* EXISTENCE ITSELF. Face it. What do ''you'' understand about it? Its origin? We keep on talking about existence even though no one can really define it.

* Dreams. The ones that make sense are perhaps the least common.

** In fact, the original Surrealist movement used dreams as its main inspiration. Given our tendency to refer to weird things as "surreal" nowadays, one could argue that dreams are the origin of MindScrew art.

* The theory of UsefulNotes/{{relativity}}. What’s your understanding of space and time? Location, distance, speed are all unambiguous, time is the same for everyone, etc? It's wrong. Space (and time too, possibly) just doesn't work that way. And that's just Special Relativity. Its big brother General Relativity is a lot more mind-screwing than that.

* Time even more so than space. Is it a real, tangible force that flows in four or more directions in four or more dimensions? Or is it just an existential explanation for gradual change which sates our need to catalog events and arrange everything into patterns? (Or alternately - [[Series/DoctorWho from a non-linear, non-subjective viewpoint - is it more like]] [[TimeyWimeyBall a big ball of wibbly-wobbly, timey-wimey]]... ''[[BuffySpeak stuff]]''?) The debate has raged for hundreds of years. Not helping is the fact that sometimes physics doesn't need to take time into account. Neither is the fact that, according to some simulations, time might be slowing down. Or maybe not--how would we know?

** For that matter, anything related to time travel theories. To further the point, look at the TemporalParadox and TimeyWimeyBall tropes. Read those and tell me you are not confused.

* Black holes. Read UsefulNotes/BlackHoles and you’ll (not) understand why.

* UsefulNotes/RichardFeynman once quipped, "If you think you understand quantum mechanics--you don't understand quantum mechanics." To give ''one'' example: small particles behave like waves. When a light wave goes through two slits right next to each other, it creates an interference pattern of light and dark bars. Doing the same with lots of electrons yields the same results, with light bars meaning more electrons hit there and dark bars meaning less. Doing the same with one electron at a time and adding the results together yields the ''exact same'' result. Translation: the electron goes through ''both slits'' and ''interferes with itself''. Observing the electron as it goes through gives a pattern of just two bars, as if the electron behaves solely like a particle, meaning simply ''observing the experiment'' changes the results.

* Abstract algebra, topology, and anything in UsefulNotes/{{mathematics}} that isn't immediately usable in some engineering/economics field (and those aren't completely exempt). Forget everything that you claim to know about such "trivial" things as addition, multiplication, division, space (space, as in 3D space), etc. Remember that some of the trippier aspects of quantum-mechanics are just special cases in mathematics.

** Mathematically, Quantum Theory is quite simple, really. It's in trying to make sense of it that things get ugly.

** One of the weirder things to come out of topology and set theory is a mathematical structure called the "[[http://en.wikipedia.org/wiki/Long_line_%28topology%29 long line]]". It's like the usual real line, but ''much longer''. Yes, it's longer than a line of infinite length. (Making sense of what that means requires some set theory.) So much longer, in fact, that even an infinite sequence of steps can only cover a tiny portion of it.

** Almost any mathematical concept taken to a high-enough level qualifies, right up to the concept of ''numbers''. Much of this has to do with the weirdness inherent in set theory (everything is a set; an element in a set, which is a type of subset; a subset of a set, which can itself be considered a set; or a relation on a set) and infinities (yes, plural--there are different sizes. See below).

* For spatial mathematics, consider this: The 'right-hand' 3-dimensional Vector direction of Y is counter-clockwise from X, which is clockwise from Z, which is counter-clockwise from Y. What this means is that Left is -1, Right is + 1, Down is -1, Up is + 1... and Backward is + 1, Forward is -1. Somehow, this makes the math work ''right''.

* Anything about 4-dimensional objects (or worse, more). If you take a bunch of 2D squares and fold them up, you get a cube. If you take a bunch of 3D cubes and fold ''those'' up, you get a [[http://commons.wikimedia.org/wiki/File:8-cell-simple.gif tesseract]].[[note]]No, not [[Film/{{Thor}} that one]]. Think more ''Literature/AWrinkleInTime'', only not quite.[[/note]]

* Fractals. Taken from the right perspective, it's impossible to tell a tiny sliver of melting ice from a glacier hundreds of square miles in size. Many natural features exhibit self-similarity across mind-boggling scales.

* e[[superscript:iπ]]--an irrational, transcendental number raised to the power of the product of another transcendental number and an ''imaginary'' number--equals ''[[ShockingSwerve what now]]''?

** [[spoiler:-1]].

** Leading to Euler's identity (aka Euler's equation), widely considered to be an example of deep [[http://en.wikipedia.org/wiki/Mathematical_beauty mathematical beauty]]: e[[superscript:iπ]] + 1 = 0.

* Speaking of [[http://en.wikipedia.org/wiki/E_(mathematical_constant) e]], it has so many nice properties in so many seemingly unrelated areas that it seems to be an key component '''OF MATH ITSELF'''. Think about it.

** [[http://en.wikipedia.org/wiki/List_of_topics_related_to_%CF%80 Same with]] π.

* [[http://en.wikipedia.org/wiki/Imaginary_number Imaginary numbers]]. A product of sheer impossibility created by the simple action of taking the square root of a negative number.

** Electrical engineers use them to model the behavior of Alternating Current (AC) circuits because they actually ''do'' correctly describe how these circuits behave!

** Not only applicable in electrical engineering, but fluid dynamics and aerodynamics too. Well defined two-dimensional fluid flows can be complete solved using a [[http://en.wikipedia.org/wiki/Schwarz%E2%80%93Christoffel_mapping series of transformations involving imaginary numbers.]]

* [[http://en.wikipedia.org/wiki/Negative_temperature Negative temperature]]. No, not negative Celsius or Fahrenheit, that would make too much sense. It is a truly negative temperature in ''[[BeyondTheImpossible Kelvin]]''. It is the temperature of something so "cold" it is hotter than anything with a positive temperature so when they come into contact heat will flow from the system with negative temperature to the one with positive temperature. In other words, temperature seen as a dial that has been turned past the 0-point and ended up at the other "end point".

* Biggest Mind Screw in UsefulNotes/{{Mathematics}} or a faulty proof?

-->[[UsefulNotes/FermatsLastTheorem "It is impossible to separate a cube into two cubes, or a fourth power into two fourth powers, or in general, any power higher than the second into two like powers. I have discovered a truly marvellous proof of this, which this margin is too narrow to contain."]]

** i.e., for "x[[superscript:n]] + y[[superscript:n]] = z[[superscript:n]] you can only find integer values for x, y and z that will produce a valid equation where n <= 2.

** Considering that it was never mentioned by Fermat again and that the eventual solution was 150 pages of extremely complex math involving mathematical concepts that didn't exist during Fermat's time (i.e. before ''basic calculus''), it's almost certain that Fermat discovered his proof was wrong and never mentioned that fact, or [[{{Troll}} had no proof at all]], but we may never know. Some have suggested that his theorem was a practical joke to frustrate fellow mathematicians: It's true, they just couldn't ''prove'' it. It is now the mathematical equivalent of the TheGreatPoliticsMessUp: Some Sci-Fi shows say that Fermat's Theorem has still never been solved (''Series/StarTrekTheNextGeneration'', for example, made a reference to it saying that it wasn't solved), when it fact it finally has.

* The [[http://en.wikipedia.org/wiki/Banach-Tarski_theorem Banach-Tarski theorem]] states that any ball can be divided into pieces and reassembled into two balls the same size as the original. ''Webcomic/IrregularWebcomic'' offers an [[http://www.irregularwebcomic.net/2339.html explanation]] in (almost) layman's terms as to how this is possible. [[spoiler:It isn't. It only works with mathematical abstractions, not actual objects.]]

* Gödel's Incompleteness Theorems. The first one shows that any consistent axiomatic system sophisticated enough to encompass elementary arithmetic contains statements that are true but cannot be proved in the system. Even more mind-screwtastic is Tarski's Indefinability Theorem, which states that the set of true statements in an axiomatic system is a non-namable set. Just think about it: it states that ''truth is indefinable in an axiomatic system''.

* If you thought ''Film/TheMatrix'' was mind-boggling, and you Did The Research, you already should be familiarized with Monsieur Jean Baudrillard. If don't, and you don't want to know that we live in a increasingly complex fake reality over-imposed onto reality by the media apparatus and the exchange system which we gladly buy in a daily basis, you better keep it that way. A brief reflexion on his school of thought:

** Simulacrum is not what covers the truth.

** Is truth the one which covers the fact that there is no truth.

** Simulacrum is true.

*** You may find it amusing at first, the scary part comes when you start nodding and saying "[[OhCrap Uh oh, it's starting to make sense]]".

* The Zen Koan is to make you achieve enlightenment by Mind Screws.

** What did your face look like before your parents were born?

** Two hands clap and there is a sound. What is the sound of one hand?

*** Don't know, ask [[Franchise/StarCraft Rory Swann]].

*** [[WesternAnimation/TheSimpsons Bart Simpson]] figured that one out--[[FridgeBrilliance he just slapped his fingers against his palm]].

*** [[Literature/{{Discworld}} It's "cl". The other hand makes the "ap"]].

*** [[http://buttersafe.com/2007/08/09/consulting-the-master/ This apparently]].

** "What is Buddha?" Dongshan said, "Three pounds of flax."

** Mu

* Complexity Theory (aka Ramsey Theory), which is at least as old as Chaos Theory and is the counterpart to it; it states that, given enough data, it is impossible for there '''not''' to be some kind of pattern to them. (Which doesn't signify that said pattern ''means'' anything...)

* [[http://en.wikipedia.org/wiki/Boltzmann_brain Boltzmann brain]]. A BrainInAJar-like, self-aware entity that, [[TimeAbyss given enough time]], would appear from nothing, complete with false memories and totally oblivious to the fact it's in the middle of the most absolute nowhere.

** And there's some evidence that this is more likely than the world as we know it being real.

* The concept of solipsism: Everything and everyone around you exists only so long as you do, potentially for as long as you do. You are the lynch-pin of the universe.

* Ever think about parallel universes? Most would have completely different sets of physical laws, assuming "laws" are a viable concept; or even if "concepts" have the capability to exist. Or if existence in itself is warped beyond human comprehension. And the worst thing of all, is that all these crazy, otherworldly, incomprehensible laws all makes sense within that universe, it all conforms to that universe's rules or "laws". Just thinking about it makes your head hurt.

** It's even worse. See the "infinite" entry below.

* Infinity and eternity will make your head hurt. [[UpToEleven Especially the fact that some infinities are larger than others]].

** If you consider possibilities such as our universe being infinite and/or an infinite number of [[AlternateUniverse other universes existing]], is even more brain-hurting, as ''everything would happen an infinite number of times''. Solutions to the paradoxes brought by them range from assuming time will end someday to [[YouCannotGraspTheTrueForm our inability to compute infinite probabilities]].

* LSD's effects. Completely subjective to the individual and utterly incomprehensible to someone who has never taken it.

* [[TrueArtIsIncomprehensible True Art]].

* PostModernism ''loves'' this.

* Many Website/ChuckNorrisFacts and [[RussianReversal Soviet Russia jokes]] count as this. Just ''how'' does a car drive a human?

* The [[http://www.maydaymystery.org/mayday/ May Day Mystery]], an uncategorizable and indescribable series of bizarre documents, possibly the coded annals of a conspiracy. Sure, it could all just be an (insanely) elaborate hoax, but WhatDoYouMeanItsNotSymbolic? If you squint and turn your head it kind of looks like an AlternateRealityGame.

* [[http://www.buzzfeed.com/mjs538/60-completely-unusable-stock-photos This collection of stock photos]].

* The now-infamous [[http://en.wikipedia.org/wiki/The_dress_(viral_phenomenon) dress]]. Depending on how your brain processes color, it may appear to be either white and gold or blue and black--and good luck convincing someone who sees it the other way. (The real colors, apparently, are blue and black.)

** And now more and more people who TakeAThirdOption have appeared, claiming that the dress is blue and dark gold.

* Wiki/TVTropes:

** At least half the entries in WildMassGuessing.

** The ThirdPersonPerson page. How many of the RealLife entries are posted by the person they speak of?

* ''Webcomic/{{Homestuck}}'''s [[StealthPun ~ATH]] coding language is a parody of programming in general, and esoteric languages in the specific.

** Any [[http://en.wikipedia.org/wiki/Esoteric_programming_language esoteric programming language]] will qualify as a MindScrew. For bonus points, there's one named "brainfuck."

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