explain xkcd - User contributions [en]

2034: Equations

2018-08-17T14:03:32Z

141.101.107.30: /* Transcript */ Unicode guy back again, minor fixes

{{comic
| number = 2034
| date = August 17, 2018
| title = Equations
| image = equations.png
| titletext = All electromagnetic equations: The same as all fluid dynamics equations, but with the 8 and 23 replaced with the permittivity and permeability of free space, respectively.
}}

==Explanation==
{{incomplete|Created by an EQUATION. Do NOT delete this tag too soon.}}
This comic gives a set of equations supposedly from different areas of science in mathematics, physics, and chemistry. To anyone not familiar with the field in question they look pretty similar to what you might find in research papers or on the relevant Wikipedia pages. To someone who knows even a little about the topic, they are clearly very wrong and only seem even worse the more you look at them.

;All kinematics equations
:<math>E = K_0t + \frac{1}{2}\rho vt^2</math>
{{w|Kinematics}} describes the motion of objects without considering mass or forces.

This equation here literally states: "Energy equals a constant <math>K_0</math> multiplied by time, plus half of density multiplied by speed multiplied by time squared". The first term here is hard to interpret: it could be correct if <math>K_0</math> is a constant power applied to the system, but this symbol would more normally be used to denote an initial energy, in which case so multiplying by <math>t</math> would be wrong. The second term looks similar to the traditional kinetic energy formula <math>\frac{1}{2}mv^2</math> but with a density instead of the mass. This is then wrong without some accompanying volume term (on either side of the equation). This appears to be a play on the forumula: <math>s = ut + \frac{1}{2}\ at^2</math> where distance travelled (s) in a constantly accelerating environment, is determined by initial velocity (u), time (t) and acceleration (a)

;All number theory equations
:<math>K_n = \sum_{i=0}^{\infty}\sum_{\pi=0}^{\infty}(n-\pi)(i-e^{\pi-\infty})</math>
{{w|Number theory}} is a branch of mathematics primarily to the study the properties of integers.

Taken literally the equation says: "The nth K-number is equal to: for all i in 0 to infinity, for all pi in 0 to infinity; subtract pi from n, and multiply it with i minus e to the power of pi minus infinity". A twofold misconception can be seen here. The first is the reassignment of pi as a variable instead of the constant (3.14...). This might be a jab at how in number theory letters and numbers are used interchangeably, but where some letters are all of a sudden fixed constants. The second misconception is the use of infinity in the latter part of the formula. Naively this would signify that (with the reassigned pi values) the part in the power would range from minus infinity to zero. However, infinity is not a number and cannot be used as one without using a limit construct.

;All fluid dynamic equations
:<math>\frac{\partial}{\partial t}\nabla\cdot \rho = \frac{8}{23}
\int\!\!\!\!\!\!\!\!\!\;\;\bigcirc\!\!\!\!\!\!\!\!\!\;\;\int
\rho\,ds\,dt\cdot \rho\frac{\partial}{\partial\nabla}
</math>
{{w|Fluid dynamics}} describes the movement of non-solid material. In particular for gases, the density <math>\rho</math> is often the most interesting quantity (for liquids, this is actually just constant). A unique feature of fluid-dynamic equations is the presence of {{w|Advection|advection terms}}, which take the form of often strange-looking spatial derivatives. This equation turns this up to a new level by differentiating with respect to a differential operator <math>\nabla</math>, which does not make any sense at all. Also it has a contour integral which seems reminiscent to a closed-circle process like in a piston engine, but this does not really fit in the context (differential description of a gas), and it has a pair of {{w|Magic number (programming)|unexplained numbers}} <math>8</math> and <math>23</math>, probably alluding to the {{w|Heat capacity ratio|specific heat ratio}} which is often written out as the fraction <math>\tfrac{7}{5}</math>, whereas most other physics equations [[899: Number Line|avoid including any plain numbers higher than 4]].

;All quantum mechanic equations
:<math>|\psi_{x,y}\rangle = A(\psi) A(|x\rangle \otimes |y\rangle)</math>
{{w|Quantum mechanics}} is a fundamental theory in physics which describes the nature at scales of atoms and below. It typically uses the {{w|Bra–ket notation|bra–ket notation}} in its formulae.

This equation takes a state psi in the dimensions of x and y and equates it to an operator A performed on psi multiplied by the same operator performed on the tensor product of x and y. Seeing as the state psi is already the tensor product of the states x and y, this is equivalent to performing the same unknown operator twice on psi, and unless this operator is its own inverse such as a bit-flip or Hermitian operator, this equation is therefore incorrect.

;All chemistry equations
:<math>\mathrm{CH}_4 + \mathrm{OH} + \mathrm{HEAT} \rightarrow \mathrm{H}_2\mathrm{O} + \mathrm{CH}_2 + \mathrm{H}_2 \mathrm{EAT}</math>
A {{w|Chemical equation|chemical equation}} is the symbolic representation of a chemical reaction in the form of symbols and formulae, wherein the reactant entities are given on the left-hand side and the product entities on the right-hand side. The number of each element on the left side must match them on the right side, the equation is balanced. The energy produced or absorbed in this process is not included in that formula.

This here is a modification of the combustion of methane. The correct form is often taught and a good example problem but obviously there are more chemistry problems.<math>\mathrm{HEAT}</math> is normally shorthand for {{w|activation energy}}, but in Randall's version it's jokingly used as a chemical ingredient and becomes <math>\mathrm{H}_2\mathrm{EAT}</math>, taking the hydrogen atom freed by the combustion equation shown. To deliver the punchline while maintaining proper stoichiometry, <math>\mathrm{OH}</math> (which should be <math>\mathrm{OH}^-</math>, since the oxygen keeps a free electron when it combines with a single hydrogen) is shown instead of <math>\mathrm{O}_2</math>. The proper methane combustion equation would be: <math>\mathrm{CH}_4 + 2 \mathrm{O}_2 \rightarrow 2 \mathrm{H}_2\mathrm{O} + \mathrm{CO}_2</math>

;All quantum gravity equations
:<math>\mathrm{SU}(2)\mathrm{U}(1) \times \mathrm{SU}(\mathrm{U}(2))</math>
This is more similar to experessions which appear in {{w|Grand_Unified_Theory|Grand Unified Theory}} (GUT) than general quantum gravity. Unlike some of the other equations, this one has no interpretation which could make it mathematically correct. This is similar to the notations used to describe the symmetry group of a particular phenomena in terms of mathematical {{w|Lie_Group|Lie Groups}}. A real example would be the Standard Model of particle physics which has symmetry according to <math>\rm{SU(3)\times SU(2) \times U(1)}</math>. Here, <math>\rm{SU}</math> and <math>\rm{U}</math> denote the special unitary and unitary groups respectively with the numbers indicating the dimension of the group. Loosely, the three terms correspond to the symmetries of the strong force, weak force and electromagnetism although the exact correspondence is muddied by symmetry breaking and the Higgs mechanism.

Of course, an expression missing an "=" sign, is difficult to interpret as an "equation", because equations normally express an "equality" of some kind. Nobody knows whether Randal refers to a horse here (equidae)

Randall's version clearly involves some similar groups although without the <math>\times</math> symbol it is hard to work out what might be happening. A term like <math>\rm{SU(U(2))}</math> has no current interpretation in mathematics, if anyone thinks otherwise and possibly has a solution to the quantum gravity problem they should probably get in touch with someone about that.

;All gauge theory equations
:[[File:All gauge theory equations.png]]
In physics, a {{w|Gauge theory|gauge theory}} is a type of field theory which is invariant to local transformations. The term gauge refers to any specific mathematical formalism to regulate redundant degrees of freedom.

This equation looks broadly similar to the sorts of things which appear in gauge theory such as the equations which define {{w|Yang–Mills_theory#Quantization|Yang-Mills Theory}}. By the time physics has got this far in, people have normally run out of regular symbols making a lot of the equations look very daunting. The actual equations in this field rarely go far beyond the Greek alphabet though and no-one has yet to try putting hats on brackets. The appearance of many sub- and superscripts is normal (this links to the group theory origins of these equations) and for the layperson it can be impossible to determine which additions are labels on the symbols and which are indices for an {{w|Einstein_notation|Einstein Sum}}.

The left-hand side <math>S_g</math> is the symbol for some {{w|Action_(physics)|action}}, in Yang-Mills theory this is actually used for a so-called "ghost action". On the right-hand side we have a large number of terms, most of which are hard to interpret without knowing Randall's thought processes (this is why real research papers should all label their equations thoroughly). The <math>\frac{1}{2\bar{\varepsilon}}</math> looks like a constant of proportionality which often appears in gauge theories. The factor of <math>i = \sqrt{-1}</math> is not unusual as many of these equations use complex numbers. The <math>\eth</math> symbol looks similar to a <math>\partial</math> partial derivative symbol especially as the {{w|Dirac_equation#Covariant_form_and_relativistic_invariance|Dirac Equation}} uses a slashed version as a convenient shorthand.

The rest of the equation cannot be mathematically correct as the choice of indices used does not match that on the left-hand side (which has none). In particle physics subscripts (or superscripts) of greek letters (usually <math>\mu</math> or <math>\nu</math>) indicate terms which transform nicely under Lorentz transformations (special relativity). Roman indices from the beginning of the alphabet relate to various gauge transformation propetries, the triple index seen on <math>p^{abc}_v</math> would likely come from some <math>\rm{SU(3)}</math> transformation (related to the strong nuclear force). Since <math>S_g</math> has none of these (and is thus a scalar which remains constant under these operations), we would need the right-hand side to behave in the same way. Most of the indices which appear are unpaired and so will not result in a scalar making the equation very wrong. For those not familiar with this type of equation, it is a similar mistake messing up units and setting a distance equal to a mass.

;All cosmology equations
:<math>H(t) + \Omega + G \cdot \Lambda \, \dots \begin{cases} \dots > 0 & \text{(Hubble model)} \\ \dots = 0 & \text{(Flat sphere model)} \\ \dots < 0 & \text{(Bright dark matter model)} \end{cases}
</math>
This is a parody of equations defining the {{w|Hubble's_law#Derivation_of_the_Hubble_parameter|Hubble Parameter}} <math>H(t)</math> although it looks like Randall has become bored and not bothered to finish his equation. Such equations usually have several <math>\Omega</math> terms representing the contributions of different substances to the energy-density of the Universe (matter, radiation, dark energy etc.). In this context <math>G</math> could be Newton's constant and <math>\Lambda</math> is the cosmological constant (energy density of empty space) although seeing them appear multiplied and on the same footing as <math>H</math> is unusual (the dot is entirely unnecessary). Choosing to make <math>H</math> a function of time <math>t</math> and not of redshift <math>z</math> is also unusual.

The second section looks like the inequalities used to show how what shape the Universe, based on the value of the curvature parameter <math>\Omega_k</math>. A value of 0 indicates a flat Universe (this more or less what we observe) whilst a positive /negative value indicates an open /closed curved Universe. Randall's choice of labels further makes fun of the field as both a flat sphere and bright dark matter are oxymoronic terms which would involve some rather strange model universes.

;All truly deep physics equations
:[[File:All truly deep physics equations.png]]
<math>\hat H</math> is the Hamiltonian operator, which when applied to a system returns the total energy. In this context, U would usually be the potential energy. However, there is also a subscript 0 and a diacritic making indicating some other variable. Much of physics is based on Lagrangian and Hamiltonian mechanics. The Lagrangian is defined as <math>\hat L = \hat K - \hat U </math> with K being the kinetic energy and U the potential. Hamiltonian mechanics uses the equation <math>\hat H = \hat K + \hat U </math>. The Hamiltonian must be conserved so taking the time derivative and setting it equal to zero is a powerful tool. The principle of least action says allows most modern physics to be derived by setting the time derivative of the Lagrangian to zero.

==Transcript==
:[Nine equations are listed, three in the top row and two in each of the next three rows. For the bottom equation to the left, there are three equations in one, the part that is different in each equation is given on three lines and a bracket encompassing all three points to three dots indicating the equation continues. Below each equation there are labels:]

:E = K0t + 1/2 pvt2
:All kinematics equations

:Kn = ∑i=0∞∑π=0∞(n-π)(i-eπ-∞)
:All number theory equations

:∂/∂t ∇ ⋅ p = 8/23 (∯ ρ ds dt ⋅ ρ ∂/∂∇)
:All fluid dynamic equations

:|ψx,y〉 = A(ψ) A(|x〉⊗ |y〉)
:All quantum mechanics equations

:CH4 + OH + HEAT → H2O + CH2 + H2EAT
:All chemistry equations

:SU(2)U(1) × SU(U(2))
:All quantum gravity equations

:Sg = (-1)/(2ε̄) i ð (̂ ξ0 +̊ pε ρvabc η0 )̂ f̵a0 λ(ℨ̆) ψ(0a)
:All gauge theory equations

:H(t) + Ω + G⋅Λ ... > 0 (Hubble model) ... = 0 (Flat sphere model) ... < 0 (Bright dark matter model)
:All cosmology equations

:Ĥ - u̧0 = 0
:All truly deep physics equations

{{comic discussion}}

[[Category:Science]]
[[Category:Physics]]
[[Category:Math]]
[[Category:Chemistry]]
[[Category:Astronomy]]

2034: Equations

2018-08-17T06:53:21Z

141.101.107.30: /* Transcript */

Talk:2032: Word Puzzles

2018-08-14T09:54:40Z

141.101.107.30: "post-live" fix

;Is it a real word puzzle?
Who wants to labouriously check if he's double-bluffed and used an actual word puzzle for this comic? :D [[Special:Contributions/162.158.154.181|162.158.154.181]] 17:45, 13 August 2018 (UTC)

"Jeopardy" is misspelled in the description. Can someone who is logged in please fix?
Many of the "clue" words can also be rearranged, anagram-wise, to form new words, e.g., parts ≈ strap. {{unsigned ip|162.158.74.243}}

Most words have 2, 3, 4 or 5 characters. I do not believe, it is a simple crossword puzzle, otherwise he would not fool people. Sebastian --[[Special:Contributions/172.68.110.4|172.68.110.4]] 18:17, 13 August 2018 (UTC)

;Some thoughts:
*Cueball is messing with Megan and not presenting an answer what the "reminiscent of Jeopardy answers" would imply.
*{{w|Lance Ito}} is a judge well known for the O. J. Simpson murder case.
*{{w|Brian Eno}} is an English musician, composer, record producer, singer, writer, and visual artist. Read the Wiki article to learn more.
*No idea what "Ohio's AirAsia Arena" could imply.
--[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 18:37, 13 August 2018 (UTC)
::Almost all the words in the alt-text / title-text are open to multiple pronunciations from a phonetic standpoint. Often they're placed next to a word containing the same sound with a different spelling, or the same spelling with a different sound.
::Once again Randall is creeping me out with this, as yesterday I complained about the spelling of "tear" with a comment including this line:
::tire tier tear tear tare tar ... teer?
::Randall so often does comics that feel intimately in touch with what I'm doing or saying the day before that it's almost spooky. If I weren't an outlier in so ''many'' scatter plots I might almost begin to feel "ordinary".
::[[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 22:35, 13 August 2018 (UTC)

;Moved from the explanation (discussion goes here)
The kind of puzzle that Megan thinks she is solving is called a "Cryptic", which has markedly different rules than ordinary crosswords. If Cueball's statement had been "Part of this aria is an Indian garment" the answer would have been "sari", because a part of the phrase "this aria" is the sequence "sari", which in turn is an Indian garment. Cueball's actual statement contains quite a few familiar cryptic puzzle triggers. The word "composed" can be a hint of a preceding or following anagram, in this case of "this aria" or of "by Brian" or of even longer adjacent strings. Although "opera star" could be a famous singer, say "Caruso", it might also be the name of an opera followed by the name of an astronomical star. "Au pair" could be any of its ordinary meanings, say "nanny", but might also be "earrings" (because AU is the chemical symbol for gold, and a gold pair could be earrings). The word "start" is often a hint to take just the beginning of a word, so "the start" would be "t", or "start of his" would be "h" or "hi". The New York Times runs a cryptic crossword as its "second Sunday puzzle" every other month or so, and there are other regular cryptic crossword venues. In case you are interested, there are various guides on the web for solving cryptics, such as this one at The Atlantic: https://www.theatlantic.com/past/docs/issues/puzzclue.htm. (-- John?)
:This sounds like the most correct explanation to me so far, much moreso than the strictly crossword-based interpretation. I think this ''should'' be in the explanation.
:[[User:ProphetZarquon|ProphetZarquon]] ([[User talk:ProphetZarquon|talk]]) 22:44, 13 August 2018 (UTC)
: Why was this moved from the explanation? This is a far better explanation then what remains there. [[Special:Contributions/162.158.38.172|162.158.38.172]] 07:52, 14 August 2018 (UTC)
::I've moved this because it's written like a comment (including the sign). And I think at first we should focus on the ''My Hobby'' thing, Cueball is messing with someone. If you're also ''sure'', like Megan is, that there is a puzzle to solve then Cueball is probably messing you too. Nevertheless all mentioned items and persons have to be explained. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 09:16, 14 August 2018 (UTC)

Although Randall says he is messing with us, the fact that he is so much cleverer than any of the rest of us means that Cueball's statement might even be a legitimate cryptic clue. --John [[Special:Contributions/108.162.219.214|108.162.219.214]] 18:40, 13 August 2018 (UTC)

If anyone has an account on https://puzzling.stackexchange.com/, that community might be able to figure out if it's a legit puzzle. [[Special:Contributions/162.158.142.64|162.158.142.64]] 20:59, 13 August 2018 (UTC)
:I just asked at puzzling.stackexchange: https://puzzling.stackexchange.com/questions/69502/is-this-a-puzzle-if-so-what-is-the-solution. [[Special:Contributions/141.101.96.209|141.101.96.209]] 02:03, 14 August 2018 (UTC)
::One answer supports my statement above: "I see no reason to believe this is a puzzle: it's simply a bunch of words that commonly appear in crosswords." Just sayin. --[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 09:16, 14 August 2018 (UTC)

Two words: [[Nerd Sniping]] [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 07:21, 14 August 2018 (UTC)

:"opera star" = "au pair a[t the] star[t]"? --[[Special:Contributions/162.158.88.230|162.158.88.230]] 07:43, 14 August 2018 (UTC)

When I first read this sentence, I thought he just wanted to be needlessly verbose for a simple joke, like [https://www.youtube.com/watch?v=oE5KkmDAcDs here]. [[User:Fabian42|Fabian42]] ([[User talk:Fabian42|talk]]) 08:16, 14 August 2018 (UTC)

In the explanation, I think there's a misunderstanding of "post-live". Death is "post-life", while "post-live" is the period after an artist stops performing live (in rock conerts, on stage, etc.). The artist may still be alive, and even produce studio albums. So, according to the comic, Brian Eno has stopped performing on-stage, but has still continued to create music (e.g. compose an aria). - Assaf

Talk:473: Still Raw

2017-10-19T15:21:07Z

141.101.107.30:

The explanation says: "... Pluto has been the ninth planet in our solar system until 2006 ...".

It should says 'the tenth' isn'it?
[[User:SioD|SioD]] ([[User talk:SioD|talk]]) 14:52, 30 August 2013 (UTC)

:Pluto was discovered in 1930, and has been since the ninth body to be discovered and classified as a "planet". The sentence is a temporal rather than spacial reference, if that clears up any confusion. [[User:Thokling|Thokling]] ([[User talk:Thokling|talk]]) 12:04, 24 September 2013 (UTC)

::Actually, no. Using the temporal definition, Pluto would be number 13. It was discovered after Ceres, Pallas, Juno and Vesta, which were discovered, named and classified, but then quickly demoted, all about 120 years before Pluto. This was due to the fact that telescopes of the day were strong enough to see quite a bit of the asteroid belt in a relatively short time, unlike with the "previously mythical" Kuiper belt.
::Also, if any thing, the spacial discrepancy should be between eighth and ninth, as Pluto's orbit is squeezed enough to be inside that of Neptune, but long enough to extend outside it. Charon, Pluto's "moon" may cause additional worry, but is usually ignored.
::Anonymous 01:11, 4 December 2013 (UTC)

:::I think this interpretation is a bit deliberately obtuse. Ceres wasn't considered a planet at the same time that Pluto was, so Pluto was indeed the ninth planet for a period of time. There is no confusion here.
:::On another note, the Dawn and New Horizons probes have now given us a large world covered in volatiles and weather, with internally driven geology, and a smaller, more obviously non-spherical cratered ball of rock. A common sense definition of a planet would probably leave Ceres out. As for Vesta, nobody has ever considered that a planet, not even the "Pluto should still be a planet" crowd. Again, being deliberately contrarian doesn't usually shed any light on scientific questions. [[Special:Contributions/108.162.250.158|108.162.250.158]] 03:38, 18 April 2016 (UTC)

:I think we would all be happy if the astronomers would come up with a definition of a planet that reasonably included Pluto but reasonably excluded the other 'candidates' that have been found so far. You know, the ones without large moons. Or Pluto could just be grandfathered in. Exactly how would science be held back by this?? [[Special:Contributions/108.162.219.223|108.162.219.223]] 00:00, 4 January 2014 (UTC)
:You don't think they tried to find a standard that included Pluto and excluded the others? Also grandfathering makes the idea of making a standard definition useless. {{unsigned ip|108.162.250.162}}
:: For my part, I never understood why it was such an issue to not have the other things that are now dwarf planets classified as planets. More planets are cool, aren't they? They could have used whatever cut they made between dwarf planets and other stuff as definition boundary for planets and promoted them instead of declassifiying Pluto. You could then have split the category "planets" into "instert-cool-name-here"-planets and dwarf planets and voilà, more planets AND congruent definition. Also, less confusing nomenclature, as with the present definition dwarf planets aren't planets, even though the name makes it appear as if they are a subcategory of planets. I totally get why Pluto should be in a seperate category from the other large planets. [[Special:Contributions/162.158.91.95|162.158.91.95]] 11:46, 19 October 2017 (UTC)
::I always assumed the decision was aesthetic. They were faced with a choice between eight well-known planets with familiar names and distinctive characteristics that fit neatly on a poster and dozens or hundreds of planets, mostly obscure lumps of rock or ice.

The airplane/treadmill question is actually hard to define properly. In real case scenario, the plane would of course take off, but you can keep it in place if you assume really fast treadmill (much faster that the plane), friction in airplane wheels and that those wheels won't break off, catch fire or otherwise get destroyed under the stress much higher they are developed for. Oh, wait, actually the airplane WONT take off if the wheels break. :-) -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 12:01, 5 December 2013 (UTC)

:If you choose to model friction in the wheels, it would be simpler to model the airplane with NO wheels, and then ask whether it could take off. Well, 'Airplane!' notwithstanding, it couldn't. But that's not an interesting problem, right? And neither is the variation with friction in the wheels. [[Special:Contributions/108.162.219.223|108.162.219.223]] 23:54, 3 January 2014 (UTC)
::Odd that carrier decks still have to be so long. In fact launching them from podiums would allow the use of on-deck hangars.
::Anyone know if this applies to helicopters?

[[User:Weatherlawyer| I used Google News BEFORE it was clickbait]] ([[User talk:Weatherlawyer|talk]]) 02:14, 31 January 2015 (UTC)

1897: Self Driving

2017-10-05T23:34:10Z

141.101.107.30: /* Explanation */ rm nonexplanation

{{comic
| number = 1897
| date = October 2, 2017
| title = Self Driving
| image = self_driving.png
| titletext = "Crowdsourced steering" doesn't sound quite as appealing as "self driving."
}}

==Explanation==
{{incomplete|First draft}}
This comic references the approach of using {{w|CAPTCHA}}<nowiki>s</nowiki> input to solve problems, particularly those involving image classification, which are not solvable by computers.

Such an approach can serve to create the learning set as the basis for training an {{w|artificial intelligence}} (AI) to better recognize or respond to similar stimuli. This approach was used by Google to identify house numbers for Google Street View, and nowadays Google also uses CAPTCHAs to identify street signs and objects in pictures. This might be a reasonable way to help improve the performance of the AI in a self-driving car that responds to video input, by reviewing images it might encounter and flagging road signs, etc. that it should respond to.

However, the temptation might be to simply sidestep the hard problem of AI by having all instances 'solved' by "offloading [the] work onto random strangers" through CAPTCHAs. For example, this has been used to defeat CAPTCHAs themselves; people were asked to solve CAPTCHAs to unlock pornographic images in a computer game, while the solution for the CAPTCHA was relayed to a server belonging to cybercriminals. (See [http://news.bbc.co.uk/2/hi/technology/7067962.stm PC stripper helps spam to spread] and [https://doi.org/10.1016/S1353-4858(08)70036-9 Humans + porn = solved Captcha]).

Alarmingly, the developers of this '{{w|Self-driving car|self driving}}' car seem to have gone for the lazy approach. Instead of teaching an AI, the CAPTCHA answer is used in real time to check whether the "self-driving" car is about to arrive at an intersection with a stop sign. This information is pretty critical, as failing to mark the stop could cause an accident. The user is unlikely to respond to the CAPTCHA in time to avert disaster, not to mention that any interruption to the car's internet connection could prove fatal. [[:Category:Self-driving cars|Self driving cars]] has become a recurrent theme on xkcd.

The system depicted is a {{w|Wizard of Oz experiment}} (as is the "Mechanical Turk" which a popular crowdworking system is named after) whereas actual self-driving cars, to the extent that they can use (Re-) CAPTCHA-style human detection systems, would involve an asynchronous decision system. Other synchronous decision systems which actually exist are political voting and money as a token of the exchange value of trade.

The title text explains that this method could be called "crowdsourced steering", {{w|crowdsourcing}} meaning sending the data on the internet to let several users provide their ideas and input on a problem. People would naturally suspect that this is considerably less safe than a car which is actually capable of self-driving; if the internet can barely [[1333: First Date|collectively steer a videogame character]], what chance do they have steering an actual, physical vehicle?

This also suggests that [[Randall]] is a bit skeptical of the current stage of AI, as this doubts whether the AI technology really is working in the way that we expect. It also comments on how what we call 'progress' actually is putting our work onto other people.

==Transcript==
:[Inside a frame there is the following text above an image:]
:To complete your registration, please tell us whether or not this image contains a stop sign:

:[The square image is a drawing of a road leading up to a sign post with a hard to read word at the top part of the sign. The sign also has two smaller signs left and right with unreadable text. The image is of poor quality, but trees and other obstacles next to the road can be seen. Darkness around the edges of the image could indicate that it is night and the landscape is only lit up by a cars head lights.]
:Sign: Stop

:[Beneath the image there are two large gray buttons with a word in each:]
:No Yes

:[Beneath the buttons are the following text:]
:Answer quickly – our self-driving car is almost at the intersection.

:[Caption beneath the frame:]
:So much of "AI" is just figuring out way to offload work onto random strangers.

{{comic discussion}}

[[Category:Self-driving cars]]
[[Category:Artificial Intelligence]]

Talk:1838: Machine Learning

2017-05-19T04:43:07Z

141.101.107.30:

Appearently, there is the issue of people "training" intelligent systems out of their gut feeling: Let's say for example a system should determine whether or not a person should be promoted to fill a currently vacant business position. If the system is taught by the humans currently in charge of that very decision, and it weakens the people the humnas would decline and stenghtens the one they wouldn't, all these people might do is feeding the machine their own irrational biases. Then, down the road, some candidate may be declined because "computer says so".
One could argue that this, if it happens, is just bad usage and no inherent issue of machine learning itself, so I'm not sure if this thought can be connected to the comic. In my head, it's close to "stirring the pile until the answers look right". What do you people think?
[[Special:Contributions/162.158.88.2|162.158.88.2]] 05:39, 17 May 2017 (UTC)

It's a good point but I don't think it's relevant to the comic. [[Special:Contributions/141.101.107.252|141.101.107.252]] 13:55, 17 May 2017 (UTC)

Up the creek *with* a paddle. [[Special:Contributions/162.158.111.121|162.158.111.121]] 07:52, 17 May 2017 (UTC)

It's a compost pile! Stir it and keep it moist until something useful comes out.
[[Special:Contributions/162.158.75.64|162.158.75.64]] 11:40, 17 May 2017 (UTC)
]

Actually I doin't think the paddle has anything to do with canoes - paddles like that are often used when stirring large quantities. In Louisiana its called a crawfish or gumbo paddle

I think the entire paragraph that goes "One of the most popular paradigms of..." needs to be cleaned up to make it human readable. [[User:Nialpxe|Nialpxe]] ([[User talk:Nialpxe|talk]]) 12:09, 17 May 2017 (UTC)

The comment that SVMs would be a better paradigm, rather than neural networks, is kind of wrong. Anyone who's worked with neural networks knows they're still essentially a linear algebra problem, just with nonlinear activation functions. Play around with tensorflow (it's fun and educational!) and you'll find most of the linear algebra isn't abstracted away as it might be in Keras, SkLearn or Caret (R). That being said, interpretability is absolutely a problem with these complex models. This is as much because the world doesn't like conforming to the nice modernist notion of a sensible theory (ie. one that can be reduced to a nice linear relationship), but even things like L1 regularisation often leave you wondering "but how does it all fit together?". On the other hand, while methods like SVMs still have a bit of machine learning magic in resolving how its hyperplane divides the hyperspace (ie. the value is derived empirically, not theoretically), the results are typically human interpretable, for a given definition of interpretable. It's no y= wx + b, but it's definitely possible. Same same for most methods short of very deep neural nets with millions of parameters. Most machine learning experts I've met have a pretty good idea what is going on in the simpler models, such as CARTs, SVMs, boosted models etc. The only reason neural nets are blackbox-y is that there's a huge amount going on inside them, and it's too much effort to do more than analyse outputs! [[Special:Contributions/172.68.141.142|172.68.141.142]] 22:43, 17 May 2017 (UTC)

Does anyone else think the topic may have been influenced by Google's recently (May 17) featured article about machine learning?[[https://www.google.com/intl/en/about/main/gender-equality-films/]]
--[[Special:Contributions/162.158.79.35|162.158.79.35]] 12:17, 17 May 2017 (UTC)
:Google has been saying a lot about machine learning recently, particularly w.r.t. android. [[Special:Contributions/141.101.107.30|141.101.107.30]] 04:43, 19 May 2017 (UTC)

Maybe one day bots will learn to create entire explanations for xkcd. [[Special:Contributions/141.101.99.179|141.101.99.179]] 12:38, 17 May 2017 (UTC)
:Good, then maybe we won't have over-thought explanations anymore.
:: "That was a joke, haha" [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 07:36, 18 May 2017 (UTC)

The fuck is "{{w|Pinball}}"? [[Special:Contributions/162.158.122.66|162.158.122.66]] 03:59, 19 May 2017 (UTC)

1838: Machine Learning

2017-05-19T02:35:02Z

141.101.107.30: /* Explanation */

{{comic
| number = 1838
| date = May 17, 2017
| title = Machine Learning
| image = machine_learning.png
| titletext = The pile gets soaked with data and starts to get mushy over time, so it's technically recurrent.
}}

==Explanation==
{{incomplete|Work in progress. <s>This explanation is an attempt at {{w|design by committee|machine learning by committee}}.</s>}}

{{w|Machine learning}} is a method employed in automation of complex tasks. It usually involves creation of algorithms that deal with statistical analysis of data and pattern recognition to generate output. The validity/accuracy of the output can be used to give feedback to make changes to the system, usually making future results statistically better.

Pinball stands atop his machine learning system, which consists of a pile of mathematical functions with an input funnel (labelled "data") at one end, an output box (labelled "answers") at the other, and a whole mess of mathematical functions in between. As Pinball explains to the incredulous Cueball, data enters through the funnel, undergoes an incomprehensible process of linear algebra, and comes out as answers. Pinball appears to be a functional part of this system himself, as he stands atop the pile stirring it with a paddle. Pinball's machine learning system is probably very inefficient, as he is integral to both the mechanical part (repeated stirring) and the learning part (making the answers look "right").

The main joke is that, despite this description being too vague and giving no intuition or details into the system, it is close to the level of understanding most machine learning experts have of the most popular class of techniques in machine learning, namely support vector machines. 

This comic compares a machine learning system to a compost pile. {{w|Composting}} is the process of taking organic matter, such as food and yard waste, and allowing it to decompose into a form that serves as fertilizer. A common method of composting is to mound the organic matter in a pile with a certain amount of moisture, then "stirring" the pile occasionally to move the less-decomposed material from the top to the interior of the pile, where it will decompose faster.

''One of the most popular paradigms of machine learning is that of supervised learning, where a function mapping an input to an output is learned from several input-output pairs, e.g. a function mapping images of faces to people names, from a dataset of static labelled images. Classic machine learning techniques like regression, or logistic regression, have understandable parameters, and provable algorithms, but require significant engineering in the pre-processing step and don't perform very well for data like images or natural text. Deep learning techniques, on the other hand, require very little pre-processing, but require the data to be run through several steps of linear algebra, where essentially in each step the output of the previous step is multiplied with a matrix and sent to the the next step. This multi-step process has proven to be very successful for image and text data, but the structure of the parameters, arranged as a matrix for each step, allows for very little interpretation, and can only be described as "data going through a pile of linear algebra".''

The method of training such deep neural networks is via gradient descent, which can be viewed as "stirring the pile of linear algebra until the answers start looking right".

The title text refers to recurrent neural networks, which are a useful class of deep neural networks for dealing with sequence data like speech or text.

This comic satirizes machine learning, more specifically neural networks. In its most basic form, a neural network takes data and results and strengthens connections that give the right answer and weakens ones that don't, until the results "look right". Neural networks are extremely data-dependent, and make remarkably few guarantees when compared to most other computing techniques, thus the joke.

''Recently, other forms of neural networks, such as LSTMs, feed old sequence data back into the network with some delay, making it recurrent. The title text calls this the pile "getting mushy". The title text is also be a pun based on how Pinball is going through the data. Instead of using a shovel, he is using a canoe paddle. Canoes can be used on rivers, and rivers by definition have currents. Thus, a recurrent data could, in this situation, mean data treated as if it were part of a river.''

In large-scale composting operations, the raw organic matter added to the pile is referred to as "input". This cartoon implies a play on the term "input", comparing a compost input to a data input.

==Transcript==

[Cueball Prime, holds a canoe paddle at his side and stands on top of a "big pile of linear algebra" containing a funnel labeled "data" and box labeled "answers". Cueball II stands to the left side of the panel.)]

Cueball II: This is your machine learning system?

Cueball Prime: Yup! You pour the data into this big pile of linear algebra, then collect the answers on the other side.

Cueball II: What if the answers are wrong?

Cueball Prime: Just stir the pile until they start looking right.

{{comic discussion}}

Talk:1837: Rental Car

2017-05-18T08:17:23Z

141.101.107.30:

Started with a bare-bones explanation. Please elaborate further. [[User:Nialpxe|Nialpxe]] ([[User talk:Nialpxe|talk]]) 09:28, 15 May 2017 (UTC)

It looks like the "one in six" figure might be a reference to [[795: Conditional Risk]]? [[Special:Contributions/108.162.229.244|108.162.229.244]] 09:34, 15 May 2017 (UTC)

Added a transcript (that ip is mine, was not logged in)[[User:PMR GO|PMR GO]] ([[User talk:PMR GO|talk]]) 10:01, 15 May 2017 (UTC)

Maybe the murder car is a reference to Christine? See https://en.wikipedia.org/wiki/Christine_(1983_film)
[[Special:Contributions/162.158.88.128|162.158.88.128]] 14:45, 15 May 2017 (UTC)
:Seems like a stretch. Christine killed like 6 out of 8, for starters, and wasn't a rental... [[Special:Contributions/162.158.74.51|162.158.74.51]] 20:38, 15 May 2017 (UTC)

Is the Trivia section meant to be a joke? Otherwise, the paragraph "That equates to a reduction in risk..." should be deleted, as it is totally meaningless. Comparing two entirely different figures (number of deaths per vehicle ''sold'' worldwide one year, number of deaths per vehicle ''on the roads'' in the US the next year) makes no sense. If it's a joke, it should be made clearer. Zetfr 08:19, 16 May 2017 (UTC)

Could this joke be about how a broken GPS has higher odds of getting you killed than playing Russian Roulette?
:Don't tell me the odds. [[Special:Contributions/141.101.107.30|141.101.107.30]]

Talk:793: Physicists

2017-05-02T21:28:27Z

141.101.107.30:

And thus, the character of Sheldon Cooper was born...{{unsigned|108.28.72.186}}
: Oh great, now I can't help but read the title text in his voice. [[Special:Contributions/162.158.2.62|162.158.2.62]] 22:04, 10 November 2016 (UTC)
: Lol accurate [[Special:Contributions/108.162.219.223|108.162.219.223]] 04:59, 30 December 2013 (UTC)
::Nobody seriously reads scientific papers all the way through. Most of it is just about conditions used as controls, etcetera. Most people just get by on the abstract and the conclusion whilst seriously interested people get through to the introduction from the abstract before skipping to the conclusion.
::: I read the above statement in Raj's voice because of the original comment. Not sure why Raj.

[[User:Weatherlawyer| I used Google News BEFORE it was clickbait]] ([[User talk:Weatherlawyer|talk]]) 15:54, 26 January 2015 (UTC)

The tanscript claims the blackboard contains equations and diagrams. But there is no equation on the blackboard.