explain xkcd - User contributions [en]

298: Tesla Coil

2024-12-21T21:49:22Z

162.158.62.180: /* Explanation */ "was" should be outside of the quotations as it is not in the original quote.

{{comic
| number = 298
| date = August 3, 2007
| title = Tesla Coil
| image = tesla_coil.png
| titletext = For scientists, this can be the hardest thing about dreams.
}}

==Explanation==

[[Cueball]] diligently creates a {{w|Tesla coil}}, a device that produces {{w|high voltage}} alternating currents.

After that show by Cueball, [[Black Hat]] magically shoots electricity from his fingertips. When Cueball asks how he did that, he says that science doesn't really work, then hovers in mid-air, further proving his point. There is simply no apparent explanation for Black Hat's abilities, which means science is still woefully incomplete or, as Black Hat said, simply doesn't work.

Black Hat further explained that the reason that nobody told Cueball was because they thought he was "cute when [he] got into something". Implying that everyone else also knows, and only Cueball was clueless.

The title text indicates that this was all actually a dream, explaining Black Hat's abilities and pointing out how dreams can be difficult for scientists as they will attempt to analyze and understand everything in the dream according to the laws of science, which wouldn't apply in dreams.{{citation needed}}

==Transcript==
:[Cueball and Black Hat stand near a tesla coil mounted on a table.]
:Cueball: I finally finished my Tesla Coil!

:[The room is dark; the characters appear as faint blue outlines on black background. Cueball turns on the Tesla Coil and it sparks white static electricity.]
:''click''
:Black Hat: Cool, but—

:Black Hat: Check this out!
:[Lightning shoots out of Black Hat's hands, Cueball appears to be in shock  and awe.]

:[The lights are back on, Cueball's arms are raised in amazement.]
:Cueball: How did you do that?
:Black Hat: The world doesn't actually make any sense. Science doesn't work. No one told you because you're so cute when you get into something.

:[Black Hat floats up the frame, and Cueball is pointing towards Black Hat.]
:Black Hat: Still, neat toy.
:Cueball: Now you're hovering!
:Black Hat: I guess you're still not getting this.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Black Hat]]
[[Category:Comics with color]]
[[Category:Comics with inverted brightness]]

Talk:2700: Account Problems

2022-11-19T01:25:08Z

162.158.62.180:

What was going on with this page? [[User:Sarah the Pie(yes, the food)|Sarah the Pie(yes, the food)]] ([[User talk:Sarah the Pie(yes, the food)|talk]]) 00:58, 19 November 2022 (UTC)

:Vandalism. I mentioned it on the [[explain xkcd:Community portal/Admin requests|Admin requests]] page. It's getting reverted back to normal pretty quickly when it happens, but it will probably keep happening until an admin bans the person doing it, or the person doing it gets bored and stops on their own. [[User:Equites|Equites]] ([[User talk:Equites|talk]]) 01:05, 19 November 2022 (UTC)

are two nazis actually in an edit war or is it just one person astroturfing --[[Special:Contributions/162.158.63.100|162.158.63.100]] 01:18, 19 November 2022 (UTC)

I'm trying to combat it, but I'll only be able to keep this up for around another 20 minutes or so. [[User:InfoManiac|InfoManiac]] ([[User talk:InfoManiac|talk]]) 01:21, 19 November 2022 (UTC)

This reminds me of the time I used a character in my password that was the "stty kill" character for one workstation's default console terminal settings. I normally logged in via ssh, and occasionally logged in via xdm, but the time I tried logging in via the console, it really didn't like what was left of my password. [[Special:Contributions/162.158.62.180|162.158.62.180]] 01:25, 19 November 2022 (UTC)

165: Turn Signals

2022-05-04T21:21:32Z

162.158.62.180: Undo revision 248744 by Ex Kay Cee Dee (talk)

{{comic
| number = 165
| date = October 2, 2006
| title = Turn Signals
| image = turn_signals.png
| titletext = I'm not very good at meeting people.
}}

==Explanation==
{{w|Turn signals}} are designed to flash between 60 and 120 times per minute. Most turn signals are driven by an {{w|electromechanical}} device. Due to manufacturing tolerances, battery state of charge, ambient temperature, and various other factors, two different turn signals rarely flash at the same rate, even among cars of the same make and model. Having two cars with turn signals flashing at the same rate would be a rare event.

[[Cueball]] notices this event, and expresses his excitement to the driver of the other car, despite being stopped at an intersection. The other driver is confused by this. Turn signal frequency is something that most people don't take notice of.{{Citation needed}} Cueball, however, takes it as an opportunity to strike up a conversation and make a new friend.

The beat frequency is the rate at which two frequencies transition from being ''{{w|phase (waves)|in phase}}'' with each other to being ''out of phase'' and then to being ''in phase'' again. In other words, two turn signals that begin by flashing together will transition to flashing opposite each other and then back to flashing together, and the rate at which this process cycles is the beat frequency. Because the beat frequency is simply the ''difference'' between the two turn signal frequencies, two turn signals whose frequencies are closer together will take longer to pass through the in-phase/out-of-phase cycle, and two signals whose frequencies are identical would take an infinite time (i.e., their relative phase never changes). The beating of turn signals is an easy phenomenon to observe when one is stopped at a {{w|traffic light}} with nothing to do but watch the flashing turn signals, and it is the lack of beating that Cueball noticed and excitedly reported.

The title text refers to the fact that this is probably not a good strategy for making friends, and it could suggest that the character Cueball may be [[Randall]].

==Transcript==
:[Two cars are seen sitting at a red light. One person is seen walking from his car up to the driver of the car in front of him. The turn signals of both cars seem to be blinking at the same time.]
:Person in Street: Hey, our turn signals are in sync!
:Person in Car: What the hell?

:Person in Street: Usually they're at least a little off. But I've been watching like 30 seconds and haven't seen any beat frequency!
:Person in Car: Who are you?

:Person in Street: You know, from the beat frequency you can tell the difference in timing of the two signals.
:Person in Car: ...
:Person in Street: But ours are the same!
:Person in Car: ...
:Person in Street: So, wanna hang out later?

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics with color]]
[[Category:Traffic light]]
[[Category:Multiple Cueballs]]

1353: Heartbleed

2022-05-04T21:01:54Z

162.158.62.180: Undo revision 243780 by Ex Kay Cee Dee (talk)

{{comic
| number = 1353
| date = April 9, 2014
| title = Heartbleed
| image = heartbleed.png
| titletext = I looked at some of the data dumps from vulnerable sites, and it was... bad. I saw emails, passwords, password hints. SSL keys and session cookies. Important servers brimming with visitor IPs. Attack ships on fire off the shoulder of Orion, c-beams glittering in the dark near the Tannhäuser Gate. I should probably patch OpenSSL.
}}

==Explanation==
The {{w|Heartbleed bug}} refers to a critical bug in the {{w|OpenSSL}} cryptographic library. This bug was publicly revealed on Monday, 7 April 2014. Due to a programming error in OpenSSL versions 1.0.1 through 1.0.1f — meaning the bug had existed for two years — attackers could read random server memory by sending specially prepared HeartbeatRequest messages to an affected server.

OpenSSL is a very commonly used library to implement {{w|SSL/TLS}}, a cryptographic protocol not only used to secure web traffic but also for mail clients and much more. Only the user and the server can read the communication. On the web the protocol is ''https://'' (HTTP Secure), instead of the open ''http://'' standard. SSL is often used to protect sensitive web traffic, such as login requests, which contains the user names and passwords in the requests. The server sends a certificate to the browser before the secure connection is established. If the certificate is registered the browser accepts it automatically, otherwise the user gets a popup to accept or reject this insecure certificate.

A vulnerability that lets an attacker read random clumps of memory on the server would possibly let an attacker find recent username/password requests, allowing them to gain unauthorized access to user accounts. Even worse, this vulnerability could read the server's private key, enabling anyone to impersonate the server and/or decrypt any future traffic that relies on that key, and any previously-obtained prior traffic also, unless a "perfect forward secrecy" cipher is used. Furthermore, the Heartbleed exploit occurs during the handshake phase of setting up a connection, so no traces of it are logged, i.e. you can be attacked and never be the wiser.

More information is available at [http://heartbleed.com heartbleed.com] or under the reference [https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-0160 CVE-2014-0160 at nvd.nist.gov].

In the last panel, Megan interprets Cueball's question ("is '''everything''' compromised?") expansively. She responds that, being a computer bug, Heartbleed can only affect information which is stored on computers. Cueball concludes that information recorded in analog media, such as that written on paper or etched in clay tablets, is safe. Megan adds that imaginations are also unaffected by Heartbleed, and Cueball is reassured. The reader may wonder how our society would fare in the face of the leakage of all electronically stored private information, but having our imaginations intact is certainly reassuring.

The title text cites the {{w|Tears in rain soliloquy}}, the dying words of the replicant and main antagonist Roy Batty (played by {{w|Rutger Hauer}}) in the 1982 film ''{{w|Blade Runner}}'', implying that the 64KiB HeartBleed buffer is so complete it includes memories from replicant brains. This is ironic as in the soliloquy, Roy Batty stated "All those moments will be lost in time".

The title text also suggests to patch OpenSSL oneself, which might refer to the patched version of OpenSSL by Debian, which turned out to be vulnerable in 2008, and was the topic of [[424: Security Holes]].

===Heartbleed===
In addition to the below, see [[1354|xkcd's explanation]] in the next comic.

{{w|Transport Layer Security}} (TLS), the successor to {{w|Secure Sockets Layer|SSL}}, is a protocol that provides end-to-end encryption for data transmitted over the internet, and is described in [http://tools.ietf.org/html/rfc5246 RFC 5246]. The Heartbeat extension to TLS introduced in 2012 (described in [https://tools.ietf.org/html/rfc6520 RFC 6520]) provides a protocol for keeping an encrypted TLS session alive (preventing inactivity timeouts), so you do not have to do a costly TLS handshake with the server for subsequent transfer of information.

The Heartbeat protocol involves the client sending a packet with an arbitrary payload (often a random 16 to 32 byte number) that the server periodically sends back to the client to tell the client that the TLS session is still alive. When the client sends the packet to a vulnerable version of OpenSSL, the OpenSSL server reads a <code>payload_size</code> from the header sent by the client. This is a 2-byte number (0 to 0xffff=65535) that is supposed to describe the size of the payload. The OpenSSL library writes the payload to memory, but it does not check that the size of the payload written to memory matches the <code>payload_size</code> taken from the client's header. When the vulnerable server sends back the Heartbeat KeepAlive response to the client, it will readout <code>payload_size</code> number of bytes and send them back to the client. If you send a payload that is actually 16 bytes, but claims it is 0xffff bytes you will read the next 64KiB of memory of the vulnerable process starting from wherever the payload was written. An attacker can repeat this attack many times and can do this attack early in the TLS handshake, so the attack will not in any way be logged unless they are logging every incoming packet which is not typical and would result in many passwords being logged. As private keys often have an identifiable format, it is often possible for an attacker to find the private TLS key, so if they eavesdrop on network traffic they can decrypt and/or alter it. For more detailed information see: [http://blog.cryptographyengineering.com/2014/04/attack-of-week-openssl-heartbleed.html 1], [http://security.stackexchange.com/a/55117/2568 2], [https://news.ycombinator.com/item?id=7549943 3].

It is worth noting that modern operating systems use a {{w|Virtual Memory#Usage|virtual memory}} abstraction above physical memory. This means every process can only access memory assigned to it, so it would be impossible for a vulnerable web server to read memory assigned to another process (like a text editor that has erotic fan fiction stored to memory) on the same computer. For more info, see: [http://security.stackexchange.com/a/55271/2568 4].

It also should be noted that this heartbleed bug only affects certain versions of OpenSSL, and does not affect other TLS/SSL implementations, or OpenSSH which does not even use the TLS protocol, but uses the SSH-2 protocol (described in [http://tools.ietf.org/html/rfc4251 RFC 4251]). SSH is typically used for remote logins on unix and linux computers.

Vulnerable sysadmins need to update to a patched version of OpenSSL or one with the Heartbeats disabled. Unless their TLS keys were protected by hardware, they probably also need to revoke their old TLS keys, and generate new TLS keys. To learn how to do this visit [https://leo-green.com Leo Green]. There you will find all the information you need.

Users of vulnerable systems should change their passwords after the sysadmins have revoked their old key and issued new ones (as their passwords may have been compromised). Users can check whether a given website is vulnerable via a [http://filippo.io/Heartbleed/ Heartbleed test also available as open source]. The [https://lastpass.com/heartbleed/ Lastpass heartbleed diagnostic] also indicates whether the signature on the TLS key predates the publication of the heartbleed vulnerability.

The [https://github.com/openssl/openssl/commit/bd6941cfaa31ee8a3f8661cb98227a5cbcc0f9f3 vulnerable commit] was introduced Dec 31st, 2011 by Robin Seggelmann, the first co-author of the heartbeats RFC, and went live when OpenSSL version 1.0.1 was released on 2012-03-14 and the vulnerability was widely announced 2014-04-07.

==Transcript==
:Megan: Heartbleed must be the worst web security lapse ever.
:Cueball: Worst so far. Give us time.

:Megan: I mean, this bug isn't just broken encryption.
:Megan: It lets website visitors make a server dispense random memory contents.

:Megan: It's not just keys. It's traffic data. Emails. Passwords. Erotic fanfiction.
:Cueball: Is '''''everything''''' compromised?

:Megan: Well, the attack is limited to data stored in computer memory.
:Cueball: So paper is safe. And clay tablets.
:Megan: Our imaginations, too.
:Cueball: See, we'll be fine.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Computers]]

2021: Software Development

2022-05-04T21:01:45Z

162.158.62.180: Undo revision 241056 by Ex Kay Cee Dee (talk)

{{comic
| number = 2021
| date = July 18, 2018
| title = Software Development
| image = software_development.png
| titletext = Update: It turns out the cannon has a motorized base, and can make holes just fine using the barrel itself as a battering ram. But due to design constraints it won't work without a projectile loaded in, so we still need those drills.
}}

==Explanation==
Software development is often characterized by [[1513: Code Quality|graceless]] [[1695: Code Quality 2|solutions]] to rudimentary problems. [[Cueball]] has built an elegant drill (function) that can adjust torque and speed as necessary automatically to fulfill his requirement of 500 holes in the wall. [[Hairy]], in a categorically inelegant solution, loads 500 drills into a cannon and shoots them at the wall. This solution, in reality, would entail too many ludicrous safety problems to execute, but in software, the implications are only [[1833: Code Quality 3|really bad code]].

The casual disregard for the software itself is reminiscent of the idea of [https://devops.stackexchange.com/questions/653/what-is-the-definition-of-cattle-not-pets cattle not pets] when deploying to servers.

This resembles assigning two different software teams to resolve different parts of a problem and of making the independent tools collaborate to form a fluid solution. The so-called "drill team" is given the task of making the part of the system that makes a hole in the wall. The cannon team was given the task of making the part of the system that aims what the drill team produces at the designated place on the wall and subsequently drills the hole. The drill team assumed that the aiming device would merely position their portion on the wall allowing it to make the hole, but the cannon team could not make assumptions about how the drill team would generate holes - they needed to make something that could use whatever the drill team produced to make the holes, thus making a cannon, so they could ensure their success.

The title text is a joke about how often in software the best solution to a problem is general rather than specific. See for example developers using Ruby on Rails (a full web framework with support for emails, templating, and web sockets) for a simple API-only service. They only need a very small part of rails (the hole drilling part), but end up with the whole framework anyway due to design limitations.

Another explanation of the title text is that software development is also often characterized by complexity and unintentional interdependence between different modules of code. It is an unending source of frustration for coders that a seemingly minor change to code can cause major changes to how the program works, including changes seemingly unrelated to the specific code that changed. A similar problem is when a line of code that “should be” unnecessary (according to the rules of the programming language) ends up being essential because the program will not work if the code is cleaned up and the line removed. A final factor is that coders often write a particular function once in the first module, and then call back to that function when necessary in subsequent modules rather than rewriting the function over and over again. In that case, the first module cannot be eliminated, even if it is no longer necessary, because then all of the calls to the original function would be null, and the rest of the modules could not work. This can happen not just within programs but across them, as much software on the internet relies on large collections of program modules in public or open source software databases. When a module goes missing it can have wide ranging effects, as seen in {{w|Npm (software)#Notable breakages|March of 2016.}}

In the context of the comic, it could be that the code for the cannon was written to check if it is “loaded” before it does anything, so the drill code is still needed to get the cannon to move on its motorized base and make the holes. Or the code for the drill defines an obscure variable that is used by other code for the cannon or its base, so “removing” the drill code would cause the cannon to “crash” and not operate.

==Transcript==
:[Cueball and Hairy are standing together and Hairy holds a power tool in his hands.]
:Cueball: We need to make 500 holes in that wall, so I've built this automatic drill. It uses elegant precision gears to continually adjust its torque and speed as needed.
:Hairy: Great, it's the perfect weight! We'll load 500 of them into the cannon we made and shoot them at the wall.

:[Caption below the frame:]
:How software development works

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Hairy]]
[[Category:Programming]]

1448: Question

2022-05-04T21:01:36Z

162.158.62.180: Undo revision 245630 by Ex Kay Cee Dee (talk)

{{comic
| number = 1448
| date = November 17, 2014
| title = Question
| image = question.png
| titletext = The universe long dead, IsaAC surveyed the formless chaos. At last, he had arrived at an answer. 'I like you,' he declared to the void, 'but I don't LIKE like you.'
}}

==Explanation==
The comic is a reference to a short story by Isaac Asimov "{{w|The Last Question}}", where humans kept asking successively more complex computers whether {{w|entropy}} can be reversed, thereby preventing the {{w|heat death of the universe}}. The computers always answered "THERE IS AS YET INSUFFICIENT DATA FOR A MEANINGFUL ANSWER". In the end, the final computer figured out the answer, but there were no humans left to give the answer to.

The comic depicts a note to “Isaac” (Isaac Asimov). The note asks Isaac to identify whether he likes the note-writer by choosing either “yes” or “no”. Isaac is supposed to check an answer and hand the note back, but Isaac (whose pen is red) has written and selected a third answer, "there is as yet insufficient data for a meaningful answer", mirroring the way his computers in the short story responded. Notes of this form are stereotypically written by young schoolchildren to gauge or incite romantic interest. This allows impatient children to get an answer during a class, and timid children to get an answer without having to ask the person face to face.

Title text is a reference to the ending in “The Last Question”. The unique capitalization of "IsaAC" in this text implies that IsaAC is an acronym for a type of supercomputer named with a similar convention to the computers in "The Last Question". Instead of the computer climactically coming up with the solution on how to save the universe from entropy when all humanity is gone, like in the “The Last Question", IsaAC comes up with the anticlimactic excuse of an answer 'I like you, but I don't LIKE like you'. “LIKE like” is a childish euphemism for romantic interest. In "The Last Question", a character considers a thought that perhaps AC stands for "analog computer", but in reality this was never the case; for example, ENIAC stands for "Electronic Numerical Integrator ''And Computer''" and UNIVAC stands for "UNIVersal ''Automatic Computer''". This title text may also be meant to imply that Isaac Asimov was a supercomputer.

The original story can be read [http://www.physics.princeton.edu/ph115/LQ.pdf here].

Comic [[1737: Datacenter Scale]] also references the short-story in the title text.

==Transcript==
:[A post-it note which reads:]
:Dear Isaac
:Do you like me?
:□ Yes
:□ No
:[Below handwritten in red ink with a checked box:]
:☒ there is as yet insufficient data for a meaningful answer

{{comic discussion}}
[[Category:Comics with color]]
[[Category:Romance]]

363: Reset

2022-05-04T21:01:26Z

162.158.62.180: Undo revision 242084 by Ex Kay Cee Dee (talk)

{{comic
| number = 363
| date = December 28, 2007
| title = Reset
| image = reset.png
| titletext = Clearance for this Sign: 11 Feet
}}

==Explanation==
A common sight in workplaces is a sign reading '[XX] days since [event]' or '[XX] days without [event]', where [XX] is a two-digit number (indicated using flip cards so it may be easily changed) and [event] is some undesirable preventable occurrence. The purpose of such signs is to inspire employees by proudly displaying how long the event has been avoided or prevented. The most common version of such signs, used in industrial workplaces, displays the number of days since the last workplace accident or injury.

In the comic, the sign says "38 days since the last time someone reset this sign". The term 'reset' is the crux, because while computer-minded people tend to interpret it as 'reboot' or 'set to zero', it also means re-set (with the meaning 'set again'). [http://www.collinsdictionary.com/dictionary/english/reset See definition.]

We will call: 
reset ~ set to zero --> meaning 1 
re-set ~ set again --> meaning 2

Because the sign uses manual flip cards, one cannot add days to the counter without re-setting the sign, which creates a paradox: either you add a day by re-setting it (which, according to the sign, means you'd have to reset the sign) or you don't (in which case the value on the sign would not be valid). The value of the sign cannot be true for more than one day. The value of the sign in the comic (38) can only be true if someone flipped the cards 38 days ago.

The sign is {{w|self-referential}} (which causes the paradox). Self-reference is a [[:Category:Self-reference|recurring theme]] in xkcd. Examples include [[33: Self-reference]] and [[688: Self-Description]].

If you only use meaning 1, the sign can be seen as a {{w|Reactance (psychology)|challenge/invitation}}.

The title text refers to the signs sometimes hung over roadways in front of bridges that display the clearance of the bridge for the benefit of tall vehicles. However, this one displays only its own clearance, a number that would be unimportant if the sign itself were not there.

==Transcript==
:[Cueball stands in front of a doorway looking at a flip-counter sign posted on a wall.]
:Sign: 38 days since someone reset this sign

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Self-reference]]

476: One-Sided

2022-05-04T21:01:11Z

162.158.62.180: Undo revision 242794 by Ex Kay Cee Dee (talk)

{{comic
| number = 476
| date = September 15, 2008
| title = One-Sided
| image = one-sided.png
| titletext = He continued, "Okay, Bernanke is uncontaminated. Find a crossbow and get him into position behind one of the columns at the Fed entrance. This is gonna get ugly."
}}

==Explanation==
The comic refers to the phenomenon of hearing half a conversation from a stranger on a cell phone and, not noticing the cell phone, imagining that that person is talking to you and responding in kind. The chart gives a plot of the frequency that this occurs (for [[Randall]] here represented by the [[Cueball]] to the left) against the amount of time that passes before the error is discovered. It also implies that Randall's second relationship was in reality just a particularly long instance of this occurrence, suggesting that his 'girlfriend' wasn't even aware of the relationship.

The title text is the continuation of the phone call, which involves a fictional conspiracy involving the then Chairman of the {{w|Federal Reserve}} {{w|Ben Bernanke}} and a {{w|crossbow}}.

On September 23, about a week after this comic, Randall posted a [https://blog.xkcd.com/2008/09/23/federal-reserve-skateboard-a-short-story/ short story] to his blog, featuring Ben Bernanke breaking into the Federal Reserve building with a crossbow.

==Transcript==
:[Caption above the panel:]
:Sometimes my conversations with strangers go on for a while before I realize that they're talking on their phones.

:[To the right above a graph, Cueball is standing next to a Cueball-like guy with a backpack.]
:Guy with backpack: Hi!
:Cueball: Hi.
:Guy with backpack: What's up?
:Cueball: Uh, not a lot...
:Guy with backpack: Shit. Does Bernanke own a crossbow?

:[To the left and below these two guys is a graph with the axis labelled. The graph looks parabolic towards the left-hand side, but as x approaches infinity, y approaches zero. A vertical dashed line runs through the graph, slightly to the right of the peak of the graph. To the right of the dashed line, there is an arrow pointing to the right that is labelled. The x-axis has a broken scale, and to the right of the break, there is a very small increase in the graph that is parenthetically labelled with a small arrow.]
:Y-axis: How Often This Happens
:X-axis: Length of conversation
:Arrow: Awkward Zone
:Small arrow: (My Second Relationship)

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category: Multiple Cueballs]]
[[Category:Line graphs]]
[[Category:Crossbows]]
[[Category:Social interactions]]
[[Category:Comics featuring politicians]]
[[Category:Phones]]

1822: Existential Bug Reports

2022-05-04T21:01:01Z

162.158.62.180: Undo revision 243109 by Ex Kay Cee Dee (talk)

{{comic
| number = 1822
| date = April 10, 2017
| title = Existential Bug Reports
| image = existential_bug_reports.png
| titletext = ISSUE: If we wait long enough, eventually the Earth will be consumed by the Sun. WORKAROUND: None.
}}
==Explanation==
[[Megan]] is sitting at her desk, writing an error report. Her description of the issue is fairly standard, albeit somewhat vague: A recent software update has broken the support for hardware she needs for her job. Most likely, she is saying that her OS is now reporting a piece of hardware is no longer supported. This is self-evidently problematic for her, as described in her error report.

The humor in this strip comes from her own suggested {{w|workaround}} (a short-term method of working despite the problem), which is absurd as she proposes simply waiting for the {{w|Sun}} to consume the {{w|Earth}} when it turns into a {{w|red giant}} towards the end of its lifetime approximately {{w|Sun#After_core_hydrogen_exhaustion|5 billion years}} from now.

While this would eliminate the issue, as both the hardware and software as well as Megan and her job would all cease to exist, this would not be helpful to Megan as it does not address the underlying problem of her being unable to work in the present. 5 billion years is also far in excess of the lifespan of humans{{Citation needed}} and operating systems alike. Lastly, as it does not allow Megan to actually continue her work, it's not strictly speaking a workaround.

In the title text, [[Randall]] asks for a workaround from Megan's "workaround". He writes it down as another bug report, as though it were a software problem. The answer is that there is '''none'''. Randall in his crisis see no way to prevent Earth from being consumed by the Sun. However, one possible workaround could be evacuation of the Solar System, as if humanity still exists by the time the Earth's destruction occurs, we will likely have highly advanced technology. Maybe at that time it would even be [https://qntm.org/moving possible to move the Earth], first further out to prevent both the engulfment and also the earlier evaporation of the oceans and later it could then be moved back in when the sun turns into a {{w|white dwarf}}.

Megan has previously expressed such existential problems in [[220: Philosophy]], where Randall presented a solution for it. Similar she was depressed in [[1111: Premiere]], where it was the boiling away of the oceans, mentioned above, that was her concern.

==Transcript==
:[Megan is sitting in an office chair at her desk typing on her laptop. Above her are two light-gray frames with text. Above each frame is a bold header:]
:'''Issue:'''
:Recent update broke support for hardware I need for my job.

:'''Workaround:'''
:If we wait long enough, the Earth will eventually be consumed by the Sun.

{{comic discussion}}

[[Category:Comics featuring Megan]]
[[Category:Philosophy]]
[[Category:Computers]]
[[Category:Astronomy]]
[[Category:Time]]

Talk:2606: Weird Unicode Math Symbols

2022-04-14T11:42:12Z

162.158.62.180: Added possible meanings for U+237C ⍼

Apparently, nobody knows what U+237C ⍼ means (https://ionathan.ch/2022/04/09/angzarr.html)
: For me it looks very like as designation of where electrical cable is burrowed. It should come with numbers near angle hands designating depth and offset from sign. But it just a guess, of course [[Special:Contributions/141.101.76.221|141.101.76.221]] 05:30, 14 April 2022 (UTC)
: There are at least four people on (https://news.ycombinator.com/item?id=31012865) who claim to have seen the symbol in the wild: German/Dutch proof by contradiction, diode with a gate, Finnish proofreaders mark indicating when and how to split a word, and indicating which way EM waves are polarized --[[Special:Contributions/162.158.62.180|162.158.62.180]] 11:42, 14 April 2022 (UTC)

Can someone add a column where we try to crowdsource a description for the "mathematical use of symbol" ?

I'm curious what those symbols actually mean, and the unicode titles don't give that much information.

I do not doubt that have enough math geeks on here to find the answer to most of then :-D

Thanks!
[[User:Flekkie|Flekkie]] ([[User talk:Flekkie|talk]]) 01:20, 14 April 2022 (UTC)

i agree w Flekkie's comment
[[User:Blue in real life|Blue in real life]] ([[User talk:Blue in real life|talk]]) 02:27, 14 April 2022 (UTC)

If you make edits, please don't immediately delete all of mine because you think yours are better. It shows you conflicting edits for a reason. Some explanations are nonsensical, like defining a smash product as the "result of dividing two product spaces." The smash product is specifically the quotient of the underlying spaces of two pointed spaces where points in the product spaces are identified if they contain either labeled point as an element. Other claims are simply mistaken. For instance, the ≝ symbol is used to introduce a definition, not to declare that the definition has been achieved in a proof. The claim that "A union on smash product appears to be one where the sets are nit isomorphic" is totally meaningless. The symbol ⩩ is not merely decorative but is intended as a supplemental math symbol like all the others. I couldn't track down its purpose. The APL symbol description somehow never bothers to mention APL. This is all very cursory, which is fine, but just please don't delete my work while doing it. [[Special:Contributions/172.70.130.5|172.70.130.5]] 04:15, 14 April 2022 (UTC)
:I'm done, page is yours. I'd been working on it for an hour and every time I tried to save, a new edit came in. I did my best to reconcile them but by the fifth I just saved a copy of what was there and pasted mine over. I immediately got to work on recovering what I had pasted over as indicated in the edit comment and like I said, I'm done. I've merged to the best of my ability and have no more interest in this page.
:--[[User:FrankHightower|FrankHightower]] ([[User talk:FrankHightower|talk]]) 04:37, 14 April 2022 (UTC)
::I'm very sorry if I was one of those who stepped on your edits. I was originally trying to fix brokenness in the table. ^^^^^ ≫ ^ is the symbol for preferring many small edits over not saving your work often in a batch-mode collaborative editing environment. [[Special:Contributions/172.70.207.8|172.70.207.8]] 04:55, 14 April 2022 (UTC)

:: Don't worry about it, idk why I was so upset. It's that feeling you get when you click "save" and then suddenly it's gone. If anything's still missing, I'll just restore it. [[Special:Contributions/172.70.131.106|172.70.131.106]] 05:41, 14 April 2022 (UTC)

I wish we had as much research on ⧍ and ⩩ as we have for ⍼. [[Special:Contributions/172.70.207.8|172.70.207.8]] 05:16, 14 April 2022 (UTC)
: No clue what those are for. The first is a triangle with serifs? The triangle symbol (not capital delta) is often used in geometry to represent a triangle, but why in the world would you give a geometric figure serifs? I think I may have seen the triple cross-hatch somewhere, but I couldn't say where. Maybe it's the chess commentary symbol for being mated so badly it's embarrassing. [[Special:Contributions/172.70.131.106|172.70.131.106]] 05:41, 14 April 2022 (UTC)
:: I'm guessing what must have happened is the [https://decodeunicode.org/en/u+2A00 code page in question] was filled in by a typographer with more graphic design than mathematical experience, who likely added made-up "missing" symbols as the design-logical extensions of the symbols they were given, presumably to be on the safe side in case they had what appeared to be a possibly incomplete set. There are some awesome ones in there, like "⩐" TEST-TUBE PARTHENOGENISIS, and "⨻" THE ILLUMINATI IS DEAD. [[Special:Contributions/162.158.255.171|162.158.255.171]] 06:07, 14 April 2022 (UTC)
: The ⧍ character has the same origin as ⍼, namely that they were both part of ISO/IEC TR 9573-13 with no explanation given. You can find it in some old charts online, like here: [https://www.w3.org/TR/REC-MathML/chap6/ISOAMSBe2.html], under `trisb`/codepoint E27E. [[User:Ionchy|ionchy]] ([[User talk:Ionchy|talk]]) 07:03, 14 April 2022 (UTC)
:: I am sure that I have seen maps with such a symbol used for campsites, and without the bold strokes of the top sides as the National Park Service draws it. I haven't found any yet, but I have found one without the center base -- like _/\_ -- on a 1960s era map. [[Special:Contributions/172.69.134.131|172.69.134.131]] 07:07, 14 April 2022 (UTC)
: As for ⩩, the character just before it in the Unicode code chart [https://www.unicode.org/charts/PDF/U2A00.pdf], ⩨, has the text "identical and parallel to", so it's possible the horizontal lines in this one also means "identical to". I don't know what three vertical lines mean though, and in Unicode there's three (!) different characters with similar glyphs: U+2980 ⦀, U+2AF4 ⫴, and U+2AFC ⫼. [[User:Ionchy|ionchy]] ([[User talk:Ionchy|talk]]) 07:28, 14 April 2022 (UTC)
:: Identical both vertically and horizontally? [[Special:Contributions/172.69.134.131|172.69.134.131]] 07:32, 14 April 2022 (UTC)
:: I found one suggestion that the dodecathorp should be used to refer to very big numbers...[[Special:Contributions/172.69.79.223|172.69.79.223]] 08:33, 14 April 2022 (UTC)

Apparently, Randall reads Hacker News like the rest of us... --[[Special:Contributions/172.68.110.141|172.68.110.141]] 09:38, 14 April 2022 (UTC)

[[Special:Contributions/172.68.238.67|172.68.238.67]]Did you know that ⩩ was a logo of the Romanian fascist group Iron Guard?[[Special:Contributions/172.68.238.67|172.68.238.67]]

Not that I have special knowledge (above aspiring-polymath level), but for "Rightwards Arrow Above Reverse Almost Equal To" and its leftwards sibling (the current suggestion being that it's an assignment of an approximation) I'd posit that it's a directional approximation specific to chaotic systems. For a precise a=b in a system where small changes to one side can effect large changes in the other, uncertainty or deliberate approximation of either of them ''may'' still map well enough to the value across the desired ≈ relationship, but that is only acceptably so unidirectionally. Hence (and I wouldn't know which would be the better convention) the arrow depicts the direction of either the dependence or the more dominant option, whichever it is that almost-ties the values tovether. (I also really ought to check what the ''reverse'' almost-equal-to sign is used for, it could be radically different from the 'forwards' version in some field, for which the directionality might even be trivially understood by context.) [[Special:Contributions/172.70.91.36|172.70.91.36]] 11:25, 14 April 2022 (UTC)

1572: xkcd Survey

2022-04-09T21:03:19Z

162.158.62.180: /* Explanation */

{{comic
| number = 1572
| date = September 2, 2015
| title = xkcd Survey
| image = xkcd_survey.png
| titletext = The xkcd Survey: Big Data for a Big Planet
}}
*The original comic links to [http://goo.gl/forms/B5RaBeZ6nw The xkcd survey] at Google, which is closed now.

==Explanation==
As the comic image states, it links to a survey created with [https://www.google.com/forms/about/ Google Forms], containing a series of questions. The questions range from mundane typical survey questions such as “Do you have any food allergies?”, to rather strange, such as “Fill this text box with random letters by randomly mashing keys on your leopard.” (See [[1530: Keyboard Mash]]).

The stated goal of the survey is to “create an interesting and unusual data set for people to play with”. A strange data set is a ripe opportunity for a sampling of readers. It's also supposed to be “a search for weird correlations” – presumably the goal is to be able to say things like “people who have been skydiving are (more/less) likely than average to dislike cilantro”. (See also [[882: Significant]] about finding presumably-spurious correlations between unrelated data.)

If the data is ever released, this explanation will be updated, but as of April 2022, this has not happened.

{{w|Image_map#Client-side_image_map|HTML image maps}} is a technique for marking up areas of an image on a web page, such that each area can be a link without the whole image being a link. [[Randall]] could have used this type of image map to make only the “Click here to take the survey” button be a link, and none of the rest of the image. But he cannot get the hang of it (or knowing his skills, does not wish to take the time to learn it). Not getting the hang of HTML image maps was also referenced on the banner for his [[xkcd_Header_text#2014-07-23_-_what_if.3F_book_tour|book tour]] for the [[what if?]] book

The title text is a joke off of {{w|Big Data}}, which is a name for analysis of a set of data that includes a huge amount of information. He also says "for a big planet" because the Earth is big.{{Citation needed}}

The survey is closed, and the questions replaced with the text: "The xkcd survey is now closed. Thank you for all your answers! Response data is being collected and will be posted soon." As of February 2022, the same caption is still there, with no indication of exactly how soon the data is intended to be posted. (Apparently, Randall crashed google forms, so the data is taking a long time to be retrieved [https://www.reddit.com/r/xkcd/comments/40mhve/what_ever_happened_to_the_survey_we_took/ (see this reddit thread)] - much like his breaking of [http://what-if.xkcd.com/imgs/a/62/balloon_wolfram.png Wolfram Alpha]] during answering a reader's question on [[what if?]])

==The Survey==
A recreation of the survey can be found [https://goo.gl/forms/CtAILwjyJAYsmqbO2 here on Google].

The recreation's data can be [https://goo.gl/5A77ZX found live here.]

It started with the following statement:

<nowiki>This is an anonymous survey. After it's done, a database of everyone's responses will be posted.
There's no specific reason for any of the questions. The goal is to create an interesting and unusual data set for people to play with. This is obviously not going to be a real random sample of people, but in the interest of getting cooler data, if you're sharing this with friends, try sending it to some people who wouldn't normally see this kind of thing!

WARNING: This survey is anonymous, but your answers WILL BE MADE PUBLIC. Depending what you write, it's possible that someone may be able to identify you by looking at your responses. None of these questions should ask about anything too private, but don't write anything that you don't want people to see. If you're not comfortable answering a question, just skip it.</nowiki>

'''Note:''' The order of the possible answers (the list of possibilities) was random, and changed every time the page is reloaded. So do not try to fix the order here below...

===Plane===
*Have you ever been in a plane?
**No
**Yes

===Skydiving===
*Have you ever been {{w|Parachuting|skydiving}}?
**No, but I might someday
**Yes
**No

===The Dress===
*When you first saw {{w|The dress (viral phenomenon)|The Dress}}, what color was it? — (Also see [[1492: Dress Color]] and the [[Blag]] ENTRY [http://blog.xkcd.com/2010/05/03/color-survey-results/ Color Survey Results]).
**White and gold
**A color combination not listed here
**I don't remember
**Blue and black
**What dress?

===Popular food===
*What's a really popular food that you don't like?
**''Text box''

===Floaters===
*When you look at a blue sky, do you see those swirly {{w|floater|floaters}} in your vision?
**Yes, constantly
**I'm not sure what things you mean
**Yes, occasionally
**No

===Running out of gas===
*Have you ever had a car run out of gas while you were driving it?
**Yes
**No

===Animals===
*Name the first five animals you can think of
**''Multi line text box''

===Weather===
*What's the weather like where you are right now?
**''Text box''

===Activities===
*Which of these can you do reasonably well?
*(Check all that apply)
**{{w|slam dunk|Dunk}} a basketball — A "slam dunk" or simply "dunk" is the act of jumping up and putting the ball through the net with a lot of force
**Tie a {{w|sheet bend}} or {{w|bowline}} — A sheet bend is a knot that joins two ropes together; A bowline is a knot used to form a fixed loop at the end of a rope. Although tied differently, the resulting knots are identical{{Citation needed}}.
**Roller skate
**[http://www.huffingtonpost.com/news/high-heel-race/ Run in high heels]
**Drive a stick shift — See {{w|Manual transmission}} of a car
**Solve a {{w|Rubik's cube}}
**Dive headfirst off a diving board — See {{w|Springboard}} and {{w|Diving platform}}
**Ice skate
**{{w|Skateboarding|Skateboard}}
**Walk on {{w|stilts}} — Stilts are poles, posts or pillars used to allow a person to walk at a height above the ground
**Ski
**Cut vegetables with a knife
**Swim
**Ride a horse
**{{w|Unicycle}}
**Change the oil on a car
**Do a back {{w|Handspring (gymnastics)|handspring}} — A handspring is an exercise in gymnastics in which you jump through the air landing on your hands, then again landing on your feet
**Juggle — {{w|Toss juggling}} (the most recognizable form of juggling) consists in throwing objects into the air and catching them.

===Spelling===
*What word can you never seem to spell on the first try?
**''Text box''

===Condiments===
*Do you eat {{w|condiments}} directly out of the fridge as a snack?
**No
**Yes

===Thermostat===
*When you adjust a thermostat that was set by someone else, it's usually because you want the room to be...
**Cooler
**Warmer

===Clothing===
*What color is the shirt/dress/upper-body-clothing you're wearing right now, if any?
**''Text box''

===Colds===
*Do you get {{w|Common cold|colds}} often?
**No
**Yes

===Number===
*Pick a number from 1 to 100
**''Text box''

===Spelling===
*On a scale of 1 to 10, how good at spelling are you? (Note that the question does not specify which end of the scale is good or bad.)
**''Tick off list with numbers from 1 to 10.''

===Myers-Briggs===
*Do you know your {{w|Myers–Briggs_Type_Indicator|Myers-Briggs type}}?
**No
**Yes

===Astrology===
*Do you know your {{w|astrological sign}}?
**No
**Yes

===Siblings===
*How many older siblings do you have?
**''Text box''
*How many younger siblings do you have?
**''Text box''
*How many twin/etc siblings do you have?
**''Text box''

===Sleepiness===
*Do you feel sleepy a lot?
**Yes
**No

===Movie star===
*Name a movie star
**''Text box''

===Time in sun===
*Do you spend a lot of time in the sun?
**Yes
**No

===Broccoli===
*Does {{w|broccoli}} taste bitter to you?
**Yes
**No
**I've never had it

===Wakefulness===
*Do you regularly stay awake much later than you meant to?
**Yes
**No

===Keyboard mashing===
*Fill this text box with gibberish by mashing random keyboard keys (See [[1530: Keyboard Mash]]).
**''Broad multi-line text box''

===Driving===
*On a scale of 1 to 5, where 1 is terrible and 3 is average, how good a driver do you think you are?
**''Tick off list with numbers from 1 to 5.''

===Allergies===
*Do you have any food allergies?
**No
**Yes

===Thunder===
*Have you heard thunder or seen lightning in the past year? — (The title-text of [[831: Weather Radar]] mentions the belief that thunderstorms seemed more common when one was a kid. Since the survey also asks for age this question is likely a test of that belief.)
**Yes
**No

===Flavor preference===
*Which do you prefer? (It seems to be missing the ''neither'' option...)
**Chocolate
**Vanilla

===Number (reprise)===
*Pick another number from 1 to 100 (Supposedly should not be the same as in the first pick a number box).
**''Text box''

===Internet===
*When you think about stuff on the internet, where do you picture it being physically located? Even if you know it's not really how things work, is there a place you imagine websites and social media posts sitting before you look at them? If so, where is it?
**''Broad multi-line text box''

===Roll tongue===
*Can you {{w|Tongue rolling|roll your tongue}}?
**Yes
**No
**What?

===Toes===
*Can you pick things up with your toes?
**No
**Yes

===Age===
*How old are you?
**''Text box''

===Walls===
*What color are the walls around you right now?
**''Text box''

===Cell phone===
*What kind of cell phone do you have?
**{{w|iPhone}}
**{{w|Android (operating system)|Android}}
**Other smartphone
**Non-smartphone
**I don't have a cell phone

===Eating===
*What's the last thing you ate?
**''Text box''

===Difficult words===
*Which of these words do you know the meaning of?
*Some of these words don’t appear in any of the following dictionaries: the Oxford English Dictionary, the New Oxford American Dictionary, Wiktionary, or Dictionary.com. With one exception, however, reviewers on this site have found verifiable examples of use for the words in question.
*[http://dictionary.reference.com/ Dictionary.com] has an index of difficulty (measured in pixels, with class name <code>difficulty-indicator</code>). We add it at the right of the words that have it. N/A means that a word isn't present in Dictionary.com, or that it doesn't have an index.
**Slickle – Not in any standard dictionary. However, it [http://www.urbandictionary.com/define.php?term=Slickle is in] the crowd-sourced in Urban Dictionary, as well as a suggested planet name in [[1253: Exoplanet Names]]
**{{Wiktionary|rife|Rife}} – [http://dictionary.reference.com/browse/rife 117]
**{{Wiktionary|soliloquy|Soliloquy}} – [http://dictionary.reference.com/browse/soliloquy 150]
**Fination – not in any dictionary. Appears infrequently in Victorian texts (e.g., [http://books.google.com/books?id=ghNOAAAAYAAJ&pg=PA245&dq=Fination 1889], [http://books.google.com/books?id=nwlCAQAAMAAJ&pg=PA214&dq=Fination 1839])
**{{Wiktionary|stipple|Stipple}} – [http://dictionary.reference.com/browse/stipple 144]
**{{Wiktionary|peristeronic|Peristeronic}} – [http://dictionary.reference.com/browse/peristeronic N/A]. Randall used it and defined it for readers in [[798: Adjectives]].
**{{Wiktionary|modicum|Modicum}} – [http://dictionary.reference.com/browse/modicum 120]
**Trephony – Not available in reference dictionaries. An obsolete spelling of "{{w|Trephine}}" (especially when used as a verb for the process of {{w|Trepanning|trephination}}). Initially a transliteration of Greek [http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0057:entry=tru/panon τρυπάω] for the same.
**Tribution – A regular construction from {{Wiktionary|tribute#Verb|Tribute (verb)}} using "{{Wiktionary|-tion}}" to transform into a noun. Using this regular formation, the term would mean the act of tribute, but no examples of actual use are available. It is worth noting that the use of "tribute" as a verb is generally considered obsolete and the few forms that persist in use relate primarily to the tributary and distributary river systems
**{{Wiktionary|phoropter|Phoropter}} – [http://dictionary.reference.com/browse/phoropter N/A] 1.An instrument used in eye examinations to determine an individual's prescription, the patient looking through various lenses at a chart on the other side.
**Unitory – Not available in reference dictionaries. An obsolete spelling of "Unitary," chiefly British. While long obsolete in normal usage, it persisted longer in mathematics that it did elsewhere (particularly for "Unitory Method" and "Unitory Matrices"). Example of use: [https://books.google.com/books?id=Wl1BAQAAMAAJ&pg=RA5-PA27&lpg=RA5-PA27&dq=unitory+method&source=bl&ots=rfRKJXAJqV&sig=Wsr_gV7xG6Airah9Lx1M0hi-7Zc&hl=en&sa=X&ved=0CDsQ6AEwBmoVChMInd_R9qTbxwIVChU-Ch36IAh_#v=onepage&q=unitory%20method&f=false (1)]
**{{Wiktionary|amiable|Amiable}} – [http://dictionary.reference.com/browse/amiable 123]
**{{Wiktionary|salient|Salient}} – [http://dictionary.reference.com/browse/salient 69]
**{{Wiktionary|regolith|Regolith}} – [http://dictionary.reference.com/browse/regolith 162]
**{{Wiktionary|lithe|Lithe}} – [http://dictionary.reference.com/browse/lithe 105]
**Revergent – technical word from {{w|fern}} biology, referring to the edges of fern leaves which curl back on themselves (see [http://link.springer.com/article/10.1007%2FBF00985044 Schölch, 2000])
**{{Wiktionary|hubris|Hubris}} – [http://dictionary.reference.com/browse/hubris 117]
**{{Wiktionary|fleek|Fleek}} – [http://dictionary.reference.com/browse/fleek N/A]
**Cadine – A rare loan-word for {{Wiktionary|fr:cadine|a sultan's wife or a noble ottoman woman}} which comes to English through the French. Examples of Use: [https://books.google.com/books?id=4yz-Y-_OOO0C&printsec=frontcover#v=onepage&q=cadine&f=false (1)]. Also the name of an {{w|it:Cadine|italian city}}.
**{{Wiktionary|apricity|Apricity}} – Not available in reference dictionaries. An obsolete word for the sun's heat in winter (e.g., [http://books.google.com/books?id=CFBGAAAAYAAJ&pg=PT76&dq=apricity Bailey 1775]). According to the What If? book (page 80), this is Randall's single favourite word in the English language.

===cat===
*Please type "cat" here:
**''Text box''

===Dreams===
*Do you usually remember your dreams?
**No
**Yes

===Text editors===
*Do you have strong opinions about text editors? (See {{w|Editor war}})
**Yes
**No

===Emoji===
*How do you feel about {{w|emoji}}?
**Negative 😠 (Unicode 1f620 - Angry face)
**Positive 😊 (Unicode 263a - Smiling face)
**Neutral 😐 (Unicode 1F610 - Neutral face)

===Snow===
*Does it ever snow where you live?
**No
**Yes

===Taste of food===
*Do you strongly dislike the taste or texture of any of these things?
**Eggs
**Chocolate ice cream
**Beer
**White wine
**{{w|Carbonation}} (or Fizz)
**Red wine
**{{w|Cilantro}}
**Coffee
**Tomatoes
**Yogurt

===Beverages===
*Which of these do you regularly drink?
**Caffeinated soda (e.g. Coca-Cola, Dr. Pepper)
**Noncaffeinated soda
**Coffee
**Fruit juice
**Milk
**Beer
**Wine
**Tea
**{{w|Maple syrup}}
**Water

===Random words===
*Type five random words
**''Broad multi-line text box''

===Flying===
*Are you nervous about flying?
**Yes
**No
**A little

===Favorite number===
*On a scale of 1 to 5, which number is your favorite?
**''Tick off list with numbers from 1 to 5.''

===Sandwich===
*Which of these would you consider a {{w|sandwich}}?
*(Check all that apply)
**{{w|Taco}}
**{{w|Quesadilla}}
**{{w|Submarine sandwich|Sub/Hoagie}}
**{{w|Cheesesteak}}
**{{w|Hamburger}}
**{{w|Open-faced sandwich}}
**{{w|Calzone}}

===Animal affinity===
*Which of these describes you?
*(Check all that apply)
**Dog person
**Cat person
**Half-cat half-person
**Part of a subterranean race of dog people
**Literally named "Catherine Person"

===Sense of direction===
*Would you say you have a good sense of direction?
**Yes
**No

===Socks or underwear===
*Have you ever thrown out all your different pairs of socks/underwear, bought a bunch of replacements that were all one kind, and then told all your friends how great it was and how they should do it too?
**Yes
**No
**I did the throwing out thing, but didn't talk to everyone about it
**No, but I'm totally doing that now

==Transcript==
:[A simple comic with text only. The ''click here'' part is inside a black frame.]
:Introducing
:'''The xkcd Survey'''
:A search for weird correlations
:Note: This survey is anonymous, but
: all responses will be posted publicly 
:so people can play with the data.
:'''Click here to'''
:'''take the survey'''
:Or click here, or here.
:The whole comic is a link,
:because I still haven't gotten
:the hang of HTML imagemaps.

==Trivia==
This strip was referenced upon the availability of preorders for ''How to: Absurd Scientific Advice for Common Real-World Problems''. A new banner appeared at the top of the site to announce that preorders were available; at the right of the banner was a blue box labelled "Click here to preorder", followed immediately below by "Or click anywhere. I still haven't figured out HTML imagemaps."

{{comic discussion}}

[[Category:Comics with color]]

2186: Dark Matter

2022-03-31T00:01:04Z

162.158.62.180: /* Explanation */ no need for the double cite?

{{comic
| number = 2186
| date = August 7, 2019
| title = Dark Matter
| image = dark_matter.png
| titletext = To detect dark matter, we just need to build a bird feeder that spins two squirrels around the rim in opposite directions at relativistic speeds and collides them together.
}}

==Explanation==
[[Megan]] and [[Cueball]] are talking about {{w|dark matter}}, the mysterious invisible mass observed indirectly by the rate at which galaxies rotate. Megan states that dark matter's density in the solar system is 0.3 GeV/cm3, as claimed, for example, by [https://arxiv.org/abs/1205.4033 Bovy and Tremaine (2012) "On the local dark matter density" in ''The Astrophysical Journal''.] Cueball does not understand what that means, so Megan explains that it equates to one squirrel's mass of dark matter in the volume of the {{w|Earth}}. In the final two panels, Cueball humorously misinterprets this as implying dark matter is actually one or more squirrels, and thereby provides the mass which causes [https://www.youtube.com/watch?v=PfHu-UJaK0Q squirrels to spin on bird feeders designed to deter them] while birds, with lower mass, do not. This enrages Megan.

The {{w|gigaelectronvolt}} (GeV) is a unit of energy that can be converted to a mass using {{w|Mass%E2%80%93energy_equivalence|Einstein's formula}} ''E'' = ''mc''2. It is typically used for subatomic particles, such as {{w|weakly interacting massive particles}} (WIMPs), one of {{w|Dark matter#Composition of dark matter: baryonic vs. nonbaryonic|several contending possibilities}} for the still-open question of the composition of dark matter, and one which Megan's uniform density figure implies constitutes most of it. For example, the mass of a proton is 0.938 GeV/''c''2. However, it is common to omit the ''c''2 denominator, representing masses as GeV or MeV. A mass represented as 0.3 GeV is equal to 5.35 × 10−25 grams [https://www.wolframalpha.com/input/?i=0.3+(GeV%2Fc%5E2)+in+grams]. Since the {{w|Figure_of_the_Earth#Volume|Earth's volume}} is 1.083 × 1027 cm3 Megan's figures imply that a {{w|squirrel}} has a mass of about 1.3 lb (1.083 x 5.35 × 1027−25 g = 580 g [https://www.wolframalpha.com/input/?i=(0.3+(GeV%2Fc%5E2)%2Fcm%5E3)+*+(volume+of+earth)+in+grams]), a typical weight for several species of common squirrels.

[[:Category:Squirrels|Squirrels]] are a recurring topic on xkcd, but are not a serious alternative to WIMPs as a scientific explanation for [[2035: Dark Matter Candidates|the composition of dark matter]]. Since the September 2015 detection by the {{w|LIGO|Laser Interferometer Gravitational-Wave Observatory}} (LIGO) and subsequent confirmation by the {{w|Virgo interferometer}} of gravitational waves from unexpectedly many merging {{w|black hole|black holes}} substantially more massive than those produced by stellar collapse, {{w|primordial black hole| primordial black holes}} (PBHs) have become a popular alternative explanation to WIMPs (or squirrels), attracting [https://arxiv.org/abs/1605.04023 proponents at NASA,] and [http://www.buchaltercosmologyprize.org/#announcements other cosmologists] for [https://arxiv.org/abs/1711.10458 several reasons.] But PBHs remain controversial, because if they constituted more than a very small portion of dark matter, [https://iopscience.iop.org/article/10.1088/2041-8205/720/1/L67 alternative explanations would be almost entirely excluded.]

Other alternative hypotheses for the observations suggesting dark matter, such as theories involving the {{w|Modified Newtonian dynamics|gravitational force varying over different distances}}, often upset cosmologists as much as Megan is shown to be, because they violate the {{w|cosmological principle}} among other issues. Part of this frustration may be due to the fact that even after many decades of careful, tremendously expensive, and often [http://www.allesfoen.de/artinscience/wordpress/?p=236 stunningly beautiful] experiments, none of the many explanations for dark matter or the observations suggesting it have as yet any support from direct empirical observations.

To help resolve this mystery, the title text imagines using a spinning bird feeder like a {{w|particle accelerator}}, colliding squirrels at relativistic speeds as if they were subatomic particles, to detect dark matter particles like the CERN accelerator discovered the {{w|Higgs boson}}. (Note, however, that accelerating even [https://what-if.xkcd.com/1/ one squirrel] to relativistic velocities would destroy the feeder along with any nearby birds, not to mention the squirrels, and the surrounding city.

==Transcript==
:[Megan walks with Cueball. She is holding a hand out while telling Cueball something.]
:Megan: Dark matter density in the solar system is around 0.3 GeV/cm3
:Cueball: Is... that a lot?

:[As they continue to walk and talk she spreads her arms out.]
:Megan: In terms of mass, it means the Earth contains one squirrel worth of dark matter at any given time.
:Cueball: Wow.

:[In a frame-less panel Cueball stops while Megan walks past him. Megan is face-palming herself while looking down.]
:Cueball: Is there any way to find out which squirrel it is?
:Megan: No, it's not literally-

:[Cueball holds his hand with one finger up in front of Megan, while she has turned towards him and is holding both arms up, possible with balled fist, as she shouts back at him, shown both with large fat letters and with small lines emanating above her head.]
:Cueball: Oh, that explains why they weigh enough to set off those spinning bird feeders!
:Megan: '''''Dark matter isn't squirrels!

{{comic discussion}}

[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Squirrels]]
[[Category:Astronomy]]
[[Category:Physics]]

2583: Chorded Keyboard

2022-02-20T22:28:13Z

162.158.62.180: /* Explanation */

{{comic
| number = 2583
| date = February 18, 2022
| title = Chorded Keyboard
| image = chorded_keyboard.png
| titletext = And even though it all went wrong / I'll stand before the lord of song / with nothing on my tongue but 'I don't understand, I swear I backed up my keyboard config before messing with it'
}}

==Explanation==
{{incomplete|Created by LEONARD COHEN - Someone with proper computer knowledge should probably elaborate on the terms "chorded keyboard" and "keyboard config". Do NOT delete this tag too soon.}}
This strip is a parody of the first verse (and in the title text, the end of the last verse) of {{w|Leonard Cohen}}'s "{{w|Hallelujah (Leonard Cohen song)|Hallelujah}}", which has become a distinctive and popular song of which {{w|Cover version|covers}} and versions exist. Written as a {{w|Sentimental ballad|ballad}}, it is partly based upon the allegory of a mystical {{w|Chord (music)|musical chord}} of several musical notes, that the words and tune both describe and illustrate by example.

Here is the verse from the song (see the lyrics [https://genius.com/Leonard-cohen-hallelujah-lyrics here]):
:Now I've heard there was a secret chord
:That David played, and it pleased the Lord
:But you don't really care for music, do ya?
:It goes like this, the fourth, the fifth
:The minor fall, the major lift
:The baffled king composing "Hallelujah"

[[Cueball]] is {{w|Filk music|filking}} upon this theme, but in his case he has somehow set up his computer so that, upon pressing a certain combination of multiple keys on his keyboard, the system will automatically type out the word "hallelujah" (xkcd's all-caps typesetting makes it unclear how the word is capitalized). In his description of the process, in both the comic proper and the title text, he uses adapted lyrics that again both describe and illustrate by example. Most of the initial lyrics are floating 'thoughts'. The punchline "hallelujah", however, is 'spoken' out of his computer monitor - typical of how on-screen text is indirectly shown in this comic series. It partially continues as a song parody through the title text but then trails off into a typical computer-complaint that he perhaps [[:Category:Cueball Computer Problems|may often have cause to make]].

The original lyrics rely upon typically nuanced rhymes, such as "do you" (or "do ya'") with "Hallelujah", and "fifth" with "lift", but fairly reliably rhymes "chord" with "Lord". In [[Randall]]'s version, it starts with "chord" and "word" which ''look'' like they should rhyme, but would be /kɔɹd/ {{w|International Phonetic Alphabet|vs.}} /wɝd/ in an typical US accent. Similarly "shift" and "left" might be considered not a {{w|Perfect and imperfect rhymes|perfect rhyme}} when read as prose, but should still be possible to meaningfully sing.

Technically, a {{w|Chorded_keyboard#Open-source_designs|chorded keyboard}} is one in which (nearly) all inputs are made by simultaneous pressing of a given combination of a limited number of keys, such as a literal handful of non-alphabetic keys that the user learns to combine to represent the key-presses of more standard keyboards. The workings of such a keyboard tends to be handled internally, sending to the computer the signal(s) that ''would'' have been sent from its larger cousin.

A big thing among millenial hackers like Randall and his original audience was customising keyboard uses. The linux operating system was originally designed and used for personal customisation, and people move their configurations from system to system, often customising how things respond to such a degree that other users struggle to make use of their system at all. The first major two text editors, vim and emacs, were composed of different camps of how to efficiently type. The emacs camp believed it was more effective to hit many keys at once to accomplish a large task, but both editors were designed to be highly customisable. It's well known that the traditional qwerty keyboard was specifically designed to make typing inefficient so as to reduce engineering burden in making old typewriters responsive and reliable. Given the prevalence of them, it has been common among hackers to remap a keyboard to be more efficient, such as to use a dvorak layout rather than a qwerty layout, as it is known to be far more efficient to type with. Chorded configurations are an order of magnitude more efficient than the dvorak layout, but are more complex to configure because the result is not at all a one-to-one mapping. The traditional court reporting device is a chorded keyboard, to keep up with human speech.

Using a combination of normally single-use keys (the 'H' and a cursor) with others, including modifiers ('shift' and 'control'), i.e. 'chording' ''with'' his keyboard, is the kind of key combination found traditionally in emacs. The ballad then comes across as an ode to system customisation and the days of millenial linux hacking, when everybody who used a computer knew how to rebuild it by hand in any way they wanted.

The chording example goes beyond mainstream use (shift and an an alphabetic character changes the character case, whilst ctrl and a character may initiate an editing command) or mainstream multi-modifier combinations (ctrl, alt and the 'e' may result in the 'é', where the keyboard does not otherwise support it) and even goes beyond [[378: Real Programmers|emacs-like command ''sequences'']] which are generally software-specific. It seems more likely that such a setup is handled within the computer, either defined within the OS or (as is often the case with specialist configurable gaming keyboards) via the driver installed to mediate such esoteric keyboard combinations as the user has predefined for themselves.

Cueball's combination-keypress may in fact be better termed a 'macro', in some contexts. The single event, somehow triggered by this particular simultaneous multi-key input, invokes the injection of a pre-specified sequence of standard characters into the appropriate text-buffer/-stream in lieu of manual input.

The title text spoofs the last verse of the (original) song, with "Hallelujah" being replaced by Cueball trailing off musing about having apparently lost the backup of his keyboard configuration, implying that he ended up in a position where he would want to restore said backup (for instance, having tampered with it to the point he is no longer capable of operating the keyboard efficiently, if at all).

Here is the original verse, where the title text spoofs the last three lines:
:I did my best, it wasn't much
:I couldn't feel, so I tried to touch
:I've told the truth, I didn't come to fool ya
:And even though it all went wrong
:I'll stand before the lord of song
:With nothing on my tongue but hallelujah

As added irony, while in the original that verse is hopeful, with the singer being thankful for experiencing joy even from a relationship that ultimately failed, contrarily in the alt text Cueball is apparently expressing regret. Or, if taken literally, it could instead imply that God himself is questioning Cueball about his tampering with software, which could fit with the running gag of [[:Category:Cueball Computer Problems|Cueball's (often self-inflicted) computer problems being hyperbolically atrocious]].

When one modifies one's keyboard config, it can make the system seem unusable (or at least highly unexpected) to things like a boss, a spouse, or an automated maintenance system. When an error is made somewhere in the process, it can make the system seem unusable to the very person who made the changes, making it hard to change them back.

==Transcript==
:[Cueball is sitting in an office chair at his desk, typing on his keyboard as shown by small lines over one hand, while looking at the screen of his stationary computer. The screen is on a raised platform on his desk. Lyrical text is written upon each scene as an unspoken narration.]
:I heard there was a secret chord
:That David pressed and it typed a word

:[A closeup on Cueball in a slim panel. We see him from the waist up, with his hands on the keyboard just beneath the panels frame.]
:But you don't use a chorded keyboard, do you

:[Same setting as in the first panel, except Cueball's arms have moved and there are movement lines above and below his arms.]
:It goes like this, <control> and <shift>
:The other hand hits H and <left>

:[Slimmer panel but same setting as in the first panel, again the arms have moved a bit, with movement lines above them. The final written word of text is marked as arising directly from the computer monitor, thus written there.]
:And all at once it types out
:Computer: Hallelujah

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Songs]]
[[Category:Cueball Computer Problems]]

2545: Bayes' Theorem

2021-11-22T23:02:09Z

162.158.62.180: /* Explanation */

{{comic
| number = 2545
| date = November 22, 2021
| title = Bayes' Theorem
| image = bayes_theorem.png
| titletext = <nowiki>P((B|A)|(A|B)) represents the probability that you'll mix up the order of the terms when using Bayesian notation.</nowiki>
}}

==Explanation==
{{incomplete|Created by a FALSE POSITIVE - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

{{w|Bayes' theorem}} describes the probability of an event, based on prior knowledge of conditions that might be related to the event.

In this comic, the off-panel student knows that they are studying Bayes' theorem, so they use that prior knowledge to guess that the test result is a false positive. The punch line is the caption - if you know Bayes' theorem well enough, you don't need to actually calculate the probabilities.

The title text refers to the mathematical definition of Bayes' theorem: P(A | B) = P(B|A) * P(A) / P(B). P(A|B) represents the probability of some event A occurring, given that B has occurred. This is often referred to as "the probability of A given B". It can be hard to remember if P(A|B) means probability of A given B, or if it's B given A, and Randall's joke is based on this difficulty. Specifically, P((B|A)|(A|B)) would be the probability of (A|B) given (B|A), which makes it the probability that you got the order of the notation mixed up.

==Trivia==
When this comic came out, the title text was only "P((B", but this was quickly corrected.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[Miss Lenhart using a pointer and pointing to a white-board with statistical formulae]
:Miss Lenhart: Given these prevalences, is it likely that the test result is a false positive?
:(off-panel voice): Well, this chapter is on Bayes' Theorem, so yes.

:[Caption below the panel]:
:Sometimes, if you understand Bayes' Theorem well enough, you don't need it.

{{comic discussion}}

[[Category:Comics featuring Miss Lenhart]]
[[Category:Statistics]]

2520: Symbols

2021-09-25T00:07:19Z

162.158.62.180: Made the phrasing more neutral.

{{comic
| number = 2520
| date = September 24, 2021
| title = Symbols
| image = symbols.png
| titletext = "röntgen" and "rem" are 20th-century physics terms that mean "no trespassing."
}}

==Explanation==
{{incomplete|Created by an INTERNET ARGUMENT - Please change this comment when editing this page. Do NOT delete this tag too soon. Bare-bones explanation is in, but needs much more detail.}}

This comic refers to elements of (mostly mathematical or engineering) notation commonly used in various fields of math and science. Each piece of notation is presented as "symbolizing" not what it specifically means, but a typical ''context'' in which it might be encountered. Many of the individual descriptions sounds look like verbiage that might be found on informational or warnings signs or placards, although typically with a silly edge.

*d/dx: An undergrad is working very hard
d/dx is the symbol for a single-variable {{w|Derivative|derivative}}. This is a mathematical operation that, while difficult, is one of the most basic operations in calculus and consequently well within the reach of an undergraduate student, particularly in science. Thus, an equation with this operation would be one that would cause an undergraduate student to work very hard.

*∂/∂x: A grad student is working very hard
The replacement of the standard "d" letters with the curly letters "∂" denotes the partial derivative, which generalizes the ordinary derivative to multi-variable calculus. Problems with partial derivatives, especially partial differential equations, can be extremely challenging—appropriate for hard graduate-level work.

*ħ: Oh wow, this is apparently a quantum thing
ħ (pronounced "h-bar") is a symbol used for (the reduced) Planck's constant, a universal, fundamental constant in quantum physics. ħ is equal to the energy of a photon divided by its frequency, and angular momentum in quantum mechanical systems is measured in quantized integer or half-integer units of ħ.

*Re: Someone needs to do a lot of tedious numerical work; hopefully it's not you
The Reynolds number (which is actually usually denoted by "Re," not "Re" as it appears in the comic) is the most important dimensionless group in fluid mechanics. Named for Osborne Reynolds, Re characterizes the relative sizes of inertial and viscous effects in a moving fluid. Large values of Re are indicative of turbulent flow, which cannot usually be solved for analytically, and so numerical modelling is necessary. Accurate numerical studies of high-Reynolds-number flows are notoriously difficult to create and program.

*(Ta4 – Tb4): You are at risk of skin burns
The Stefan-Boltzmann law says that a perfectly absorbing ("black body") source emits electromagnetic radiation with a power per unit area of σT4, where σ is a known constant and T is the absolute temperature. The quantity (Ta4 – Tb4) thus appears in any calculation of purely radiative energy transfer between two bodies, one at temperature Ta and the other at Tb. When radiative transfer is large enough to be the most important form of heat interchange, it is normally also large enough to sear the skin with thermal or ultraviolet burns.

*NA: You are probably about to make an incredibly dangerous arithmetic error
NA, or Avogadro's number, is the number of molecules in a mole of a substance—roughly the number of protons and neutrons in 1 gram of matter. This is an enormous number, approximately 6.02 × 1023. Adding up molecular weights and converting between grams and moles of several substances is a lot of arithmetic on a scale where intuition won't help you catch mistakes. Working with NA, it is easy to make errors of one or more factors of ten without noticing. If this kind of error is made in the calculation of the stoichiometrically correct amount of a reagent in a chemical reaction, it is possible to accidentally create dangerous amounts of unwanted chemical products.

*µm: Careful, that equipment is expensive
Micrometers are a very small unit of distance. Any equipment that is operating in these units will be incredibly finely calibrated and thus very expensive.

*mK: Careful, that equipment is very expensive
Millikelvin temperatures are very cold, barely above absolute zero, suggesting sensitive experiments probing quantum mechanical behavior that would likely only exist in an advanced laboratory. Any equipment that works down a mK temperatures is likely to be very expensive.

*nm: Don't shine that in your eye
Nanometers are most frequently seen in the listed wavelengths for lasers. Pointing a visible or infrared laser at someone's eye is notoriously dangerous; the tightly-focused coherent light can cause permanent damage very quickly.

*eV: Definitely don't shine that in your eye
Electron volt energies are typical of moderate-energy particle beams, produced by accelerating electrons (or protons) over macroscopic voltages. These particle beams can be [https://en.wikipedia.org/wiki/Anatoli_Bugorski even more damaging] to soft tissues than optical-wavelength lasers.

*mSv: You are about to get into an Internet argument
The millisievert is a unit of radiation dose absorbed. It is actuality a very small dosage, but the joke refers to Internet trolls debating the effects of low-dose radiation sources, such as 5G wireless networks. Randall's comment may also be referring to [https://xkcd.com/radiation/ this chart].

*mg/kg: Go wash your hands
This unit measures the dose of a drug or other chemical in milligrams per kilogram of body mass. If the appropriate dose - or worse, the lethal dose - is measured in mg/kg (parts per million), then the substance may be quite toxic.

*µg/kg: Go get in the chemical shower
A unit 1000 times smaller than mg/kg. If a dosage is measured in micrograms per kilogram (parts per billion), it is probably causing chemical rather than biological reactions.

*π or τ: Whatever answer you get will be wrong by a factor of exactly two
π is defined as the ratio of a circle's circumference to its diameter, while τ is defined as 2π (the ratio of the circumference to the radius). π has been used as the primary constant for describing the circumference and area of circles for millennia, but proponents of τ claim that τ is actually more natural in most constants, since it makes working in radians more straightforward. The joke here is that whichever constant you use, it will probably be the wrong one (off by a factor of two, one way or the other) for the formula you are trying to use.

The title text refers to two non-SI units of radiation measurement. In the mid-20th century when they were in use, the dangers of radiation weren't as well understood as today, so an area with radiation that was noteworthy back then is probably dangerous, hence the no trespassing part.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

;d/dx
:An undergrad is working very hard
;∂/∂x
:A grad student is working very hard
;ħ
:Oh wow, this is apparently a quantum thing
;Re
:Someone needs to do a lot of tedious numerical work; hopefully it's not you
;(Ta4 - Tb4)
:You are at risk of skin burns
;NA
:You are probably about to make an incredibly dangerous arithmetic error
;µm
:Careful, that equipment is expensive
;mK
:Careful, that equipment is very expensive
;nm
:Don't shine that in your eye
;eV
:Definitely don't shine that in your eye
;mSv
:You are about to get into an internet argument
;mg/kg
:Go wash your hands
;µg/kg
:Go get in the chemical shower
;π or τ
:Whatever answer you get will be wrong by a factor of exactly two

{{comic discussion}}