explain xkcd - User contributions [en]

2721: Euler Diagrams

2023-01-07T21:15:15Z

172.71.134.132: /* Explanation */

{{comic
| number = 2721
| date = January 6, 2023
| title = Euler Diagrams
| image = euler_diagrams_2x.png
| imagesize = 370x409px
| noexpand = true
| titletext = Things Leonhard Euler created ( most of math ( overlapping circle diagrams ) a cricket bowling machine ) Things John Venn created
}}

==Explanation==
{{incomplete|Created by THE EULER BOT - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

In this comic, [[Cueball]] is showing an off-screen person a {{w|Venn diagram}} he made about something. The off-screen person then factually informs Cueball that it is an {{W|Euler diagram}}, not a Venn diagram, and seems about to go into the reasons. Cueball may know the reasons, as he interrupts with the complaint that {{w|List of things named after Leonhard Euler|many things}} are named for {{w|Leonhard Euler}} (specifically {{w|Euler's constant}} and {{w|Euler's function}}) and just wants to call the diagram a Venn diagram to give {{w|John Venn}} a more equal share of the fame. His off-screen friend refuses, and mockingly states that numbers are now called "Euler letters", which is currently false.{{citation needed}} Modern {{w|Arabic numerals}} predate Euler by at least a century, and other numerals existed before that.

A Venn diagram is "a widely used diagram style that shows the logical relation between sets". It shows overlap of items in different categories (sets) by using overlapping circles (or other shapes) to stand in for categories. If an item is within a certain circle, it is in the category the circle represents. So in a Venn diagram of "animals" and "fuzzy things", "cat" would be in the overlap between both circles, "frog" would be inside only "animals", and "kiwifruit" would only be in "fuzzy things". "Crystals" would be outside both
circles.

{{w|John Venn}} was not the first to invent the idea of drawing regions whose overlap shows the intersection of sets -- that was popularized by Euler (although he may not have been the first to do it) and was known as {{w|Euler Diagram}}s. Venn's innovation, roughly 100 years later, was to consistently draw ALL intersections of sets, even those intersections that had no members. In a Venn diagram, all 'circles' must overlap with all other circles, even if there are no items in the overlap. This is easy enough for 2 and 3 sets, but as the number of sets increases, the diagrams can get [https://www.newscientist.com/article/dn22159-logic-blooms-with-new-11-set-venn-diagram/ rather complicated]. [https://raw.githubusercontent.com/wiki/tctianchi/pyvenn/venn6.png This] and [https://en.wikipedia.org/wiki/Template:Supranational_European_Bodies the relationships between the European countries] is another example. The sets can start looking very non-circular. An Euler diagram is required to depict only the non-empty combinations/sets, and therefore does not have this constraint. The diagram in the comic does not have any overlap between the left and right sections so, while it is an Euler diagram, it is not a Venn diagram.

[[File:Euler Diagrams title text.png|300px|thumb|right|The title text as a Venn (and, simultaneously, an Euler) diagram]]
The title text is an example of a "written" Venn diagram, with Leonhard Euler creating "most of math", John Venn creating a {{w|cricket}} bowling machine, and both of them having created overlapping circle diagrams.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}<br>
:[Cueball is standing in front of a whiteboard, evidently giving a talk. The title "Venn Diagram of" is visible, along with three partially overlapping circles and various illegible text.]
:Offscreen voice: Actually, that's an ''Euler'' diagram, because-
:Cueball (palms upraised pleadingly): Come '''''onnnn.'''''
:Cueball: '''''Everything''''' is named after Euler. Euler's constant, Euler's function.
:Cueball: Can't we let John Venn have this?
:Offscreen voice: No.
:Offscreen voice: Also, numbers are now "Euler letters."

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Math]]
[[Category:Euler diagrams]]
[[Category:Venn diagrams]]
[[Category:Sport]]

2721: Euler Diagrams

2023-01-07T21:14:52Z

172.71.134.132: /* Explanation */

{{comic
| number = 2721
| date = January 6, 2023
| title = Euler Diagrams
| image = euler_diagrams_2x.png
| imagesize = 370x409px
| noexpand = true
| titletext = Things Leonhard Euler created ( most of math ( overlapping circle diagrams ) a cricket bowling machine ) Things John Venn created
}}

==Explanation==
{{incomplete|Created by THE EULER BOT - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

In this comic, [[Cueball]] is showing an off-screen person a {{w|Venn diagram}} he made about something. The off-screen person then factually informs Cueball that it is an {{W|Euler diagram}}, not a Venn diagram, and seems about to go into the reasons. Cueball may know the reasons, as he interrupts with the complaint that {{w|List of things named after Leonhard Euler|many things}} are named for {{w|Leonhard Euler}} (specifically {{w|Euler's constant}} and {{w|Euler's function}}) and just wants to call the diagram a Venn diagram to give {{w|John Venn}} a more equal share of the fame. His off-screen friend refuses, and mockingly states that numbers are now called "Euler letters", which is currently false.{{citation needed}} Modern {{w|Arabic numerals}} predate Euler by at least a century, and other numerals existed before that.

A Venn diagram is "a widely used diagram style that shows the logical relation between sets". It shows overlap of items in different categories (sets) by using overlapping circles (or other shapes) to stand in for categories. If an item is within a certain circle, it is in the category the circle represents. So in a Venn diagram of "animals" and "fuzzy things", "cat" would be in the overlap between both circles, "frog" would be inside only "animals", and "kiwifruit" would only be in "fuzzy things". "Crystals" would be outside both
circles.

{{w|John Venn}} was not the first to invent the idea of drawing regions whose overlap shows the intersection of sets -- that was popularized by Euler (although he may not have been the first to do it) and was known as {{w|Euler Diagram}}s. Venn's innovation, roughly 100 years later, was to consistently draw ALL intersections of sets, even those intersections that had no members. In a Venn diagram, all 'circles' must overlap with all other circles, even if there are no items in the overlap. This is easy enough for 2 and 3 sets, but as the number of sets increases, the diagrams can get [https://www.newscientist.com/article/dn22159-logic-blooms-with-new-11-set-venn-diagram/ rather complicated]. [https://raw.githubusercontent.com/wiki/tctianchi/pyvenn/venn6.png This] and [https://en.wikipedia.org/wiki/Template:Supranational_European_Bodies the relationships between the European countries] is another one. The sets can start looking very non-circular. An Euler diagram is required to depict only the non-empty combinations/sets, and therefore does not have this constraint. The diagram in the comic does not have any overlap between the left and right sections so, while it is an Euler diagram, it is not a Venn diagram.

[[File:Euler Diagrams title text.png|300px|thumb|right|The title text as a Venn (and, simultaneously, an Euler) diagram]]
The title text is an example of a "written" Venn diagram, with Leonhard Euler creating "most of math", John Venn creating a {{w|cricket}} bowling machine, and both of them having created overlapping circle diagrams.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}<br>
:[Cueball is standing in front of a whiteboard, evidently giving a talk. The title "Venn Diagram of" is visible, along with three partially overlapping circles and various illegible text.]
:Offscreen voice: Actually, that's an ''Euler'' diagram, because-
:Cueball (palms upraised pleadingly): Come '''''onnnn.'''''
:Cueball: '''''Everything''''' is named after Euler. Euler's constant, Euler's function.
:Cueball: Can't we let John Venn have this?
:Offscreen voice: No.
:Offscreen voice: Also, numbers are now "Euler letters."

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Math]]
[[Category:Euler diagrams]]
[[Category:Venn diagrams]]
[[Category:Sport]]

Talk:2711: Optimal Bowling

2022-12-15T12:26:10Z

172.71.134.132: Angle ?

Who cares about rules? I mean, I'm pretty sure your score won't count according to rules if you bowl from establishment uphill from bowling alley. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 05:36, 15 December 2022 (UTC)

If the ball has a diameter of 8.5 inches (multiplied by 2.54 and Pi makes about 67.8cm circumference) the rpm is also limited by the speed of light of the surface (reached at about 6.4x10^9rpm).

Please elaborate on how widespread the aforementioned destruction would be. [[Special:Contributions/172.71.154.38|172.71.154.38]] 10:50, 15 December 2022 (UTC)
: See What-If #1 (https://what-if.xkcd.com/1/) for reference. [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 11:01, 15 December 2022 (UTC)

Randall is clearly overestimating the mass range at which "equipment damage" would occur. Even 10^3 kilos is a //car//. I'm pretty sure that throwing a bowling ball the mass of a car would do a lot of equipment damage. I believe the 10^10 to 10^20 range should be "widespread destruction" (already a category above) and between that and the Schwarzchild mass should be something like "all life on Earth destroyed" because 10^20 kilos is plenty large enough for a global killer asteroid (admittedly its velocity would be much smaller... but still, I don't see how you have 1% of the Moon's mass in bowling ball without wiping out all life on Earth). [[Special:Contributions/172.70.85.175|172.70.85.175]] 11:20, 15 December 2022 (UTC)
: That's the joke :) The humour is in the understatement [[User:Xseo|Xseo]] ([[User talk:Xseo|talk]]) 11:51, 15 December 2022 (UTC)

For further edification: A 10^3 kg bowling ball traveling at 10^3 m/s is approximately equivalent to a shell fired from the main battery gun of a battleship. [[Special:Contributions/162.158.159.74|162.158.159.74]] 11:40, 15 December 2022 (UTC)

The aim geaph is wrong, isn't it? I have never practiced bowling, but I am pretty sure I have seen videos explaining that you need to aim on the side, and the spin will bring the ball to strike the pin group with an angle, not head on. [[Special:Contributions/172.71.134.132|172.71.134.132]] 12:26, 15 December 2022 (UTC)