explain xkcd - User contributions [en]

1665: City Talk Pages

2016-04-08T16:13:52Z

Natg 19: /* Explanation */ ce

{{comic
| number = 1665
| date = April 8, 2016
| title = City Talk Pages
| image = city talk pages.png
| titletext = "I don't think the Lakeshore Air Crash Museum really belongs under 'Tourist Attractions.' It's not a museum--it's just an area near the Lake Festival Laser Show where a lot of planes have crashed.
}}

==Explanation==
{{incomplete|First cut, please help with explanation}}

The comic makes fun about Wikipedia-talkpages. In the Wikipedia every page has also an discussion-page called talk-page in the English Wikipedia. In this case the comic talks about the talk-page of a city. While topics some are quite normal for such a talk-page (the quality of the images) others are not (too many murders in the city).

The topics show a common problem of wikipedia-talk-pages: People think that the talk-page is for talking about the ''object'', but it is for talking about the ''article''.

{{w|Voltaire}} was a French Enlightenment writer.

{{w|Zootopia}} is a 2016 Disney film.

{{w|Andrew Lloyd Webber}} was an English composer famous for writing The Phantom Of The Opera. Meanwhile, {{w|Frank Lloyd Wright}}, who has a somewhat similar name, was an American architect, who designed more than 1,000 structures.

==Transcript==
{{comic discussion}}

1665: City Talk Pages

2016-04-08T16:13:33Z

Natg 19: /* Explanation */ add more cultural notes

1665: City Talk Pages

2016-04-08T16:11:25Z

Natg 19: /* Explanation */ add info on frank lloyd wright

{{comic
| number = 1665
| date = April 8, 2016
| title = City Talk Pages
| image = city talk pages.png
| titletext = "I don't think the Lakeshore Air Crash Museum really belongs under 'Tourist Attractions.' It's not a museum--it's just an area near the Lake Festival Laser Show where a lot of planes have crashed.
}}

==Explanation==
{{incomplete|First cut, please help with explanation}}

The comic makes fun about Wikipedia-talkpages. In the Wikipedia every page has also an discussion-page called talk-page in the English Wikipedia. In this case the comic talks about the talk-page of a city. While some are quite normal for such a talk-page (the quality of the images) others are not (too many murders in the city).

Andrew Lloyd Webber was an English composer famous for writing The Phantom Of The Opera. Meanwhile, Frank Lloyd Wright, who has a somewhat similar name, was an American architect, who designed more than 1,000 structures,

==Transcript==
{{comic discussion}}

1665: City Talk Pages

2016-04-08T16:09:57Z

Natg 19: add image

File:city talk pages.png

2016-04-08T16:08:35Z

Natg 19:

== Licensing ==
{{XKCD file}}

704: Principle of Explosion

2016-02-11T19:28:01Z

Natg 19: /* Explanation */ copyedit

{{comic
| number = 704
| date = February 19, 2010
| title = Principle of Explosion
| image = principle_of_explosion.png
| titletext = You want me to pick up waffle cones? Oh, right, for the wine. One sec, let me just derive your son's credit card number and I'll be on my way.
}}

==Explanation==
[[Cueball|Cueball's]] friend (who also looks like Cueball) explains the {{w|principle of explosion}}, a classical law of logic, that says that if you start out with propositions ({{w|axiom}}s) that contradict each other, it is possible to derive (prove) any statement you want in the language you are working in, true or false.

Cueball then proceeds to misinterpret (perhaps intentionally) that you can derive any ''fact'' about the physical world. His formula of {{w|propositional logic}} in the third panel reads "'''P''' and not '''P'''", where '''∧''' is the formal logic symbol for "and" and '''<sup>¬</sup>''' is the symbol for "not". '''P''' stands for a proposition. As "'''P''' and not '''P'''" is shorthand for "'''P''' is both true and false", this forms a contradiction from which the principle of explosion can begin. Humorously and to his friend's bewilderment he then successfully manages to 'derive' the phone number for his friend's mom.

:'''An example from math''': If you assume that √2 is a rational number, you can 'prove' things that are obviously false, such as the fact that some numbers must be both even and odd. Consequently, you can draw the conclusion that √2 must be an irrational number (provided such a thing exists at all! - luckily, it does and obeys the same calculation rules as for rational numbers; this is how {{w|proof by contradiction}} works.))

:This can be seen in a {{w|Truth Table}}:
:{| class="wikitable"
|-
! P
! ¬P
! P ∧ ¬P
! P ∧ ¬P ⇒ Q
|-
| T
| F
| F
| T
|-
| F
| T
| F
| T
|}

:The formula P ∧ ¬P ⇒ Q is true in every possible interpretation. No matter what propositions are substituted for P and Q the implication is true. So if a single example of a contradiction were found, then every proposition would be true, (and simultaneously false).

After deriving the phone number Cueball instantly calls his friends mom, who turns out to be Mrs. Lenhart. She asks Cueball out, without any preamble, to his friend's vexation. It does not get better when it is obvious that she wishes to drink "cheap" {{w|boxed wine}} with him, and Cueball is free tonight! There is definitely a hint of {{w|Mrs. Robinson}} over Mrs. Lenhart here.

Maybe it is [[Miss Lenhart]] who has married, or she is the mother of both Miss Lenhart and Cueball's friend? She could, in fact, be Cueball's school teacher. He obviously knew her name and is ready to go to her place in an instant.

In the title text we hear more of Cueball's (one-sided) conversation with Mrs. Lenhart. She asks him to pick up waffle cones, a variety of {{w|ice cream cone}}. And when he sounds bewildered by this she explains that it is for drinking the wine. This is probably not a very good idea, since waffles are typically not water proof and would also dissolve into the wine. But it could also be considered kinky; something Mrs. Lenhart's son would not like to hear about. The rest of the title text is just more of the main comic's derivation joke, since Cueball will use a second to derive her son's credit card number, so he can buy the cones at his expense.

Of course we have no proof that he is actually speaking to Mrs. Lenhart. It could just be a prank he is pulling on his annoying mathematically interested friend. All he needed was to have looked her phone number up in advance.

==Transcript==
:[Cueball's Cueball-like friend is talking to him.]
:Friend: If you assume contradictory axioms, you can derive anything. It's called the principle of explosion.
:Cueball: ''Anything?'' Lemme try.

:[Cueball is writing on a piece of paper on a desk.]

:[Cueball is holding up a piece of paper to his friend, while holding a phone.]
:Cueball: Hey, you're right! I started with '''P∧<sup>¬</sup>P''' and derived your mom's phone number!
:Friend: That's not how that works.

:[The friend is looking at the piece of paper, while Cueball is talking to someone on a phone. The desk from before can be seen to the right.]
:Cueball: Mrs. Lenhart?
:Friend: Wait, this ''is'' her number! How—
:Cueball: Hi, I'm a friend of— Why, yes, I ''am'' free tonight!
:Friend: ''Mom!''
:Cueball: No, box wine sounds lovely!

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Miss Lenhart]]
[[Category:Multiple Cueballs]]
[[Category:Math]]
[[Category:Logic]]

1642: Gravitational Waves

2016-02-11T19:24:46Z

Natg 19: move sentence

{{comic
| number = 1642
| date = February 11, 2016
| title = Gravitational Waves
| image = gravitational waves.png
| titletext = "That last LinkedIn request set a new record for the most energetic physical event ever observed. Maybe we should respond." "Nah."
}}

==Explanation==
{{incomplete|Needs more technical expertise on gravitational waves}}
A {{w|gravitational wave detector}} is a device used to measure {{w|gravitational waves}}, small distortions of {{w|spacetime}} that were first predicted by Albert Einstein in 1916.

Megan, Cueball, and Ponytail are listening to signals from a gravitational wave detector. However, in addition to "normal" wave signals, there are also signals that appear to be "spam" emails, like invitations from {{w|Linkedin}}, a job networking site, a mortgage offer, and a social meetup.

This comic was published on a Thursday, not following the normal publish schedule, to coincide with the [https://www.theguardian.com/science/2016/feb/11/gravitational-waves-discovery-hailed-as-breakthrough-of-the-century discovery of a clear gravitational wave signal] on February 11, 2016. Gravitational waves were detected through the collision of 2 black holes.

==Transcript==

:[Cueball, Megan, and Ponytail are in a room in front of a computer machine]
:Megan: The gravitational wave detector works! For the first time, we can listen in on the signals carried by ripples in the fabric of space itself!

:Computer: EVENT: Black hole merger in Carina (30 Mo, 30Mo)
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Black hole merger in Orion (20Mo, 50Mo)
:Computer: EVENT: Mortgage offer from Triangulum Galaxy
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Meet lonely singles in the local group tonight!

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Astronomy]]

1642: Gravitational Waves

2016-02-11T19:21:02Z

Natg 19: /* Transcript */ fix

{{comic
| number = 1642
| date = February 11, 2016
| title = Gravitational Waves
| image = gravitational waves.png
| titletext = "That last LinkedIn request set a new record for the most energetic physical event ever observed. Maybe we should respond." "Nah."
}}

==Explanation==
{{incomplete|Needs more technical expertise on gravitational waves}}
A {{w|gravitational wave detector}} is a device used to measure {{w|gravitational waves}}, small distortions of {{w|spacetime}} that were first predicted by Albert Einstein in 1916. Gravitational waves were detected through the collision of 2 black holes.

Megan, Cueball, and Ponytail are listening to signals from a gravitational wave detector. However, in addition to "normal" wave signals, there are also signals that appear to be "spam" emails, like invitations from {{w|Linkedin}}, a job networking site, a mortgage offer, and a social meetup.

This comic was published on a Thursday, not following the normal publish schedule, to coincide with the [https://www.theguardian.com/science/2016/feb/11/gravitational-waves-discovery-hailed-as-breakthrough-of-the-century discovery of a clear gravitational wave signal] on February 11, 2016.

==Transcript==

:[Cueball, Megan, and Ponytail are in a room in front of a computer machine]
:Megan: The gravitational wave detector works! For the first time, we can listen in on the signals carried by ripples in the fabric of space itself!

:Computer: EVENT: Black hole merger in Carina (30 Mo, 30Mo)
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Black hole merger in Orion (20Mo, 50Mo)
:Computer: EVENT: Mortgage offer from Triangulum Galaxy
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Meet lonely singles in the local group tonight!

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Astronomy]]

1642: Gravitational Waves

2016-02-11T19:17:39Z

Natg 19: add more explanation

{{comic
| number = 1642
| date = February 11, 2016
| title = Gravitational Waves
| image = gravitational waves.png
| titletext = "That last LinkedIn request set a new record for the most energetic physical event ever observed. Maybe we should respond." "Nah."
}}

==Explanation==
{{incomplete|Needs more technical expertise on gravitational waves}}
A {{w|gravitational wave detector}} is a device used to measure {{w|gravitational waves}}, small distortions of {{w|spacetime}} that were first predicted by Albert Einstein in 1916. Gravitational waves were detected through the collision of 2 black holes.

Megan, Cueball, and Ponytail are listening to signals from a gravitational wave detector. However, in addition to "normal" wave signals, there are also signals that appear to be "spam" emails, like invitations from {{w|Linkedin}}, a job networking site, a mortgage offer, and a social meetup.

This comic was published on a Thursday, not following the normal publish schedule, to coincide with the [https://www.theguardian.com/science/2016/feb/11/gravitational-waves-discovery-hailed-as-breakthrough-of-the-century discovery of a clear gravitational wave signal] on February 11, 2016.

==Transcript==

:[Cueball, Megan, and Ponytail are in a room in front of a computer machine]
:Megan: The gravitational wave detector works! We can listen in on the signals carried by ripples in the fabric of space itself!

:Computer: EVENT: Black hole merger in Carina (30 Mo, 30Mo)
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Black hole merger in Orion (20Mo, 50Mo)
:Computer: EVENT: Mortgage offer from Triangulum Galaxy
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Meet lonely singles in the local group tonight!

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Astronomy]]

1642: Gravitational Waves

2016-02-11T19:15:06Z

Natg 19: add reason

{{comic
| number = 1642
| date = February 11, 2016
| title = Gravitational Waves
| image = gravitational waves.png
| titletext = "That last LinkedIn request set a new record for the most energetic physical event ever observed. Maybe we should respond." "Nah."
}}

==Explanation==
{{incomplete|Needs more technical expertise on gravitational waves}}
A {{w|gravitational wave detector}} is a device used to measure {{w|gravitational waves}}, small distortions of {{w|spacetime}} that were first predicted by Albert Einstein in 1916.

This comic was published on a Thursday, not following the normal publish schedule, to coincide with the [https://www.theguardian.com/science/2016/feb/11/gravitational-waves-discovery-hailed-as-breakthrough-of-the-century discovery of a clear gravitational wave signal] on February 11, 2016.

==Transcript==

:[Cueball, Megan, and Ponytail are in a room in front of a computer machine]
:Megan: The gravitational wave detector works! We can listen in on the signals carried by ripples in the fabric of space itself!

:Computer: EVENT: Black hole merger in Carina (30 Mo, 30Mo)
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Black hole merger in Orion (20Mo, 50Mo)
:Computer: EVENT: Mortgage offer from Triangulum Galaxy
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Meet lonely singles in the local group tonight!

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Astronomy]]

1642: Gravitational Waves

2016-02-11T19:14:34Z

Natg 19: incomplete

{{comic
| number = 1642
| date = February 11, 2016
| title = Gravitational Waves
| image = gravitational waves.png
| titletext = "That last LinkedIn request set a new record for the most energetic physical event ever observed. Maybe we should respond." "Nah."
}}

==Explanation==
{{incomplete}}
A {{w|gravitational wave detector}} is a device used to measure {{w|gravitational waves}}, small distortions of {{w|spacetime}} that were first predicted by Albert Einstein in 1916.

This comic was published on a Thursday, not following the normal publish schedule, to coincide with the [https://www.theguardian.com/science/2016/feb/11/gravitational-waves-discovery-hailed-as-breakthrough-of-the-century discovery of a clear gravitational wave signal] on February 11, 2016.

==Transcript==

:[Cueball, Megan, and Ponytail are in a room in front of a computer machine]
:Megan: The gravitational wave detector works! We can listen in on the signals carried by ripples in the fabric of space itself!

:Computer: EVENT: Black hole merger in Carina (30 Mo, 30Mo)
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Black hole merger in Orion (20Mo, 50Mo)
:Computer: EVENT: Mortgage offer from Triangulum Galaxy
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Meet lonely singles in the local group tonight!

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Astronomy]]

1642: Gravitational Waves

2016-02-11T19:08:32Z

Natg 19: copyedit

{{comic
| number = 1642
| date = February 11, 2016
| title = Gravitational Waves
| image = gravitational waves.png
| titletext = "That last LinkedIn request set a new record for the most energetic physical event ever observed. Maybe we should respond." "Nah."
}}

==Explanation==
A {{w|gravitational wave detector}} is a device used to measure {{w|gravitational waves}}, small distortions of {{w|spacetime}} that were first predicted by Albert Einstein in 1916.

This comic was published on a Thursday, not following the normal publish schedule, to coincide with the [https://www.theguardian.com/science/2016/feb/11/gravitational-waves-discovery-hailed-as-breakthrough-of-the-century discovery of a clear gravitational wave signal] on February 11, 2016.

==Transcript==

:[Cueball, Megan, and Ponytail are in a room in front of a computer machine]
:Megan: The gravitational wave detector works! We can listen in on the signals carried by ripples in the fabric of space itself!

:Computer: EVENT: Black hole merger in Carina (30 Mo, 30Mo)
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Black hole merger in Orion (20Mo, 50Mo)
:Computer: EVENT: Mortgage offer from Triangulum Galaxy
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Meet lonely singles in the local group tonight!

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Astronomy]]

1642: Gravitational Waves

2016-02-11T19:07:55Z

Natg 19: fix wiki linking

{{comic
| number = 1642
| date = February 11, 2016
| title = Gravitational Waves
| image = gravitational waves.png
| titletext = "That last LinkedIn request set a new record for the most energetic physical event ever observed. Maybe we should respond." "Nah."
}}

==Explanation==
A {{w|gravitational wave detector}} is a device used to measure {{w|gravitational waves}}, small distortions of {{w|spacetime}} that were first predicted by Albert Einstein in 1916.

This comic was published on a Thursday, not following the normal publish schedule, to coincide with the https://www.theguardian.com/science/2016/feb/11/gravitational-waves-discovery-hailed-as-breakthrough-of-the-century discovery of a clear gravitational wave signal] on February 11, 2016.

==Transcript==

:[Cueball, Megan, and Ponytail are in a room in front of a computer machine]
:Megan: The gravitational wave detector works! We can listen in on the signals carried by ripples in the fabric of space itself!

:Computer: EVENT: Black hole merger in Carina (30 Mo, 30Mo)
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Black hole merger in Orion (20Mo, 50Mo)
:Computer: EVENT: Mortgage offer from Triangulum Galaxy
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Meet lonely singles in the local group tonight!

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Astronomy]]

1642: Gravitational Waves

2016-02-11T19:05:09Z

Natg 19: beginning explanation

{{comic
| number = 1642
| date = February 11, 2016
| title = Gravitational Waves
| image = gravitational waves.png
| titletext = "That last LinkedIn request set a new record for the most energetic physical event ever observed. Maybe we should respond." "Nah."
}}

==Explanation==
A [[w|gravitational wave detector]] is a device used to measure [[w|gravitational waves]], small distortions of [[w|spacetime]] that were first predicted by Albert Einstein in 1916.

This comic was published on a Thursday, not following the normal publish schedule, to coincide with the https://www.theguardian.com/science/2016/feb/11/gravitational-waves-discovery-hailed-as-breakthrough-of-the-century discovery of a clear gravitational wave signal] on February 11, 2016.

==Transcript==

:[Cueball, Megan, and Ponytail are in a room in front of a computer machine]
:Megan: The gravitational wave detector works! We can listen in on the signals carried by ripples in the fabric of space itself!

:Computer: EVENT: Black hole merger in Carina (30 Mo, 30Mo)
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Black hole merger in Orion (20Mo, 50Mo)
:Computer: EVENT: Mortgage offer from Triangulum Galaxy
:Computer: EVENT: Zorlax the Mighty would like to connect on Linkedin
:Computer: EVENT: Meet lonely singles in the local group tonight!

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Astronomy]]

1642: Gravitational Waves

2016-02-11T19:01:26Z

Natg 19: /* Transcript */ copyedit

1642: Gravitational Waves

2016-02-11T19:00:42Z

Natg 19: add category

1642: Gravitational Waves

2016-02-11T18:58:52Z

Natg 19: add more info

1642: Gravitational Waves

2016-02-11T18:51:55Z

Natg 19: add comic image

[[File:gravitational waves.png]]

File:gravitational waves.png

2016-02-11T18:51:19Z

Natg 19:

== Licensing ==
{{XKCD file}}