explain xkcd - User contributions [en]

2945: Broken Model

2024-06-16T03:30:23Z

172.68.26.173: /* Explanation */

{{comic
| number = 2945
| date = June 12, 2024
| title = Broken Model
| image = broken_model_2x.png
| imagesize = 278x448px
| noexpand = true
| titletext = In addition to eating foxes, rabbits can eat grass. The grass also eats foxes. Our equations chart the contours of Fox Hell.
}}

==Explanation==
{{incomplete|Created by HELPLESS GRASS. Do NOT delete this tag too soon. Otherwise, the KILLER SKINWALKER FROM THE BUNNYROOMS may come for you.}}
This comic shows [[Miss Lenhart]] explaining a mathematical model of a predator-prey relationship. The model has the terms swapped, showing that 400 rabbits are preying on 20 foxes. The teacher realizes this mistake and says "If this were an ecology class, I would have to fix that." Instead of fixing the model, though, she instead begins to calculate using this flawed model, and notes that this model implies that rabbits are carnivores.

The equations start with Nrabbits(0)=400 and Nfoxes(0)=20, the number of rabbits and foxes at time 0, followed by what looks like the {{w|Lotka–Volterra equations}}, a pair of first-order nonlinear differential equations, frequently used to describe the dynamics of biological systems in which two species interact. One of the pair of equations describes the number of prey over time, the other the number of predators over time, differing only by a negative sign (and coefficients). It is easy to mix up which equation describes which species, leading to the inverted predator-prey relation described.

If this was indeed the case the rabbits would soon render the foxes extinct. The reason this doesn't happen in reality for rabbits is that they outnumber the foxes (20 foxes vs 400 rabbits) and thus can survive being preyed upon. Often the predator takes the old and sick animals first, thus keeping the rest of the animals more healthy. But following the math of the wrong formula would soon lead to zero foxes. As per the title text, the rabbits could survive without the foxes to prey on, since they still eat grass. However, this reality is terrifying for the foxes, because they are rendered as prey.

The title text extends the joke by looking at a even more flawed model. This model has grass as well, but instead of grass and foxes not interacting, grass eats foxes, creating a "Fox Hell."
In the real world, grass doesn't hunt foxes{{citation needed}}, but instead, grass pulls nutrients from air and soil and synthesizes its energy through [https://soandmo.com/blogs/blog/where-does-the-grass-plant-get-its-energy-from photosynthesis], and may use foxes that have already died from other causes as fertilizer. Foxes do occasionally [https://www.wildlifeonline.me.uk/animals/article/red-fox-diet-what-foxes-eat eat grass], although not as food, but for other health reasons.

==Transcript==
:[Miss Lenhart is holding a pointer to a whiteboard, indicating the last part of the last line of text.]
:Miss Lenhart: Hmm, looks like I accidentally swapped the predation terms.
:Miss Lenhart: If this were an ecology class, I would have to fix that.
:Miss Lenhart: Unfortunately for those 20 poor foxes, this is calculus, and the math says these 400 rabbits are hungry for meat.

:[There are three lines on the white board, where the '...' ellipses in the bottom line are illegible:]
:Nrabbits(0) = 400
:Nfoxes(0) = 20
:dN0/dt = ... dN.../... = ...

:[Caption below the panel:]
:Every broken mathematical model is just a glimpse into a terrifying alternate universe.

{{comic discussion}}

[[Category:Comics featuring Miss Lenhart]]
[[Category:Math]]
[[Category:Biology]]
[[Category:Animals]]

2945: Broken Model

2024-06-16T03:29:12Z

172.68.26.173: /* Explanation */

{{comic
| number = 2945
| date = June 12, 2024
| title = Broken Model
| image = broken_model_2x.png
| imagesize = 278x448px
| noexpand = true
| titletext = In addition to eating foxes, rabbits can eat grass. The grass also eats foxes. Our equations chart the contours of Fox Hell.
}}

==Explanation==
{{incomplete|Created by HELPLESS GRASS. Do NOT delete this tag too soon. Otherwise, the KILLER SKINWALKER RABBIT may come for you.}}
This comic shows [[Miss Lenhart]] explaining a mathematical model of a predator-prey relationship. The model has the terms swapped, showing that 400 rabbits are preying on 20 foxes. The teacher realizes this mistake and says "If this were an ecology class, I would have to fix that." Instead of fixing the model, though, she instead begins to calculate using this flawed model, and notes that this model implies that rabbits are carnivores.

The equations start with Nrabbits(0)=400 and Nfoxes(0)=20, the number of rabbits and foxes at time 0, followed by what looks like the {{w|Lotka–Volterra equations}}, a pair of first-order nonlinear differential equations, frequently used to describe the dynamics of biological systems in which two species interact. One of the pair of equations describes the number of prey over time, the other the number of predators over time, differing only by a negative sign (and coefficients). It is easy to mix up which equation describes which species, leading to the inverted predator-prey relation described.

If this was indeed the case the rabbits would soon render the foxes extinct. The reason this doesn't happen in reality for rabbits is that they outnumber the foxes (20 foxes vs 400 rabbits) and thus can survive being preyed upon. Often the predator takes the old and sick animals first, thus keeping the rest of the animals more healthy. But following the math of the wrong formula would soon lead to zero foxes. As per the title text, the rabbits could survive without the foxes to prey on, since they still eat grass. However, this reality is terrifying for the foxes, because they are rendered as prey.

The title text extends the joke by looking at a even more flawed model. This model has grass as well, but instead of grass and foxes not interacting, grass eats foxes, creating a "Fox Hell."
In the real world, grass doesn't hunt foxes{{citation needed}}, but instead, grass pulls nutrients from air and soil and synthesizes its energy through [https://soandmo.com/blogs/blog/where-does-the-grass-plant-get-its-energy-from photosynthesis], and may use foxes that have already died from other causes as fertilizer. Foxes do occasionally [https://www.wildlifeonline.me.uk/animals/article/red-fox-diet-what-foxes-eat eat grass], although not as food, but for other health reasons.

==Transcript==
:[Miss Lenhart is holding a pointer to a whiteboard, indicating the last part of the last line of text.]
:Miss Lenhart: Hmm, looks like I accidentally swapped the predation terms.
:Miss Lenhart: If this were an ecology class, I would have to fix that.
:Miss Lenhart: Unfortunately for those 20 poor foxes, this is calculus, and the math says these 400 rabbits are hungry for meat.

:[There are three lines on the white board, where the '...' ellipses in the bottom line are illegible:]
:Nrabbits(0) = 400
:Nfoxes(0) = 20
:dN0/dt = ... dN.../... = ...

:[Caption below the panel:]
:Every broken mathematical model is just a glimpse into a terrifying alternate universe.

{{comic discussion}}

[[Category:Comics featuring Miss Lenhart]]
[[Category:Math]]
[[Category:Biology]]
[[Category:Animals]]

Talk:2002: LeBron James and Stephen Curry

2018-06-05T16:08:39Z

172.68.26.173: 1 possible explanation and a clarification

I have no idea what this is about, but wondered if Stephen Curry was related to the Curry twins Tom and Ben, who are both over 6' - or to Tim, who isn't except in heels.
[[User:Arachrah|Arachrah]] ([[User talk:Arachrah|talk]]) 07:53, 4 June 2018 (UTC)
: Both LeBron James and Stephen Curry are famous NBA players. [[Special:Contributions/172.69.190.4|172.69.190.4]] 08:46, 4 June 2018 (UTC)
::How would you not know that? And even if you don't know who they are, you must have at least heard about them before, right? [[User:Herobrine|Herobrine]] ([[User talk:Herobrine|talk]]) 09:21, 4 June 2018 (UTC)
::: Not everyone is from USA. [[Special:Contributions/172.69.190.4|172.69.190.4]] 09:41, 4 June 2018 (UTC)
:::: That excuse could work, except your IP address is based in the USA :) [[User:Zachweix|Zachweix]] ([[User talk:Zachweix|talk]]) 12:01, 4 June 2018 (UTC)
::::: So is mine right now, but that doesn't mean I'm '''from''' here, and they didn't make us memorise every NBA player on the plane. (Hey cool, this IP has edited here before too) -[[Special:Contributions/162.158.186.60|162.158.186.60]] 15:36, 4 June 2018 (UTC)
:::: Basketball is the second most popular sport in the world [Citation needed], so it is safe to assume a large portion of the internet people know LeBron and Curry even if it is only by memes.

::: I like Curry. You know, the dish. And the actor. Tim, that is. [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 11:58, 4 June 2018 (UTC)
Not everyone in the USA follows sports. I've heard of LeBron James, but only in passing. The only Curry I know of is a fictional one from some old movie. {{unsigned ip|162.158.74.147}}
;Nate Silver

Nate Silver is famous for his numerical approach and extensive use of statistics and simulations.
He foresaw a probability of 28.6% for Donald to win the electoral college just before the election. That is a greater chance than most political commentators would have granted Donald. Typical betting sites saw Hillary 5:1 ahead at the evening of the election.
So I would not at all say that he got everything wrong in 2016. He predicted that Hillary would be a formidable number of votes ahead as most probable outcome, but also that many states would be very tight.
[[https://projects.fivethirtyeight.com/2016-election-forecast/]]. Sebastian --[[Special:Contributions/172.68.110.106|172.68.110.106]] 09:21, 4 June 2018 (UTC)

;Definitions needed
Hi! Could definitions be added for some of the terms used, such as "bleachers"? Thanks! [[Special:Contributions/162.158.155.200|162.158.155.200]] 11:30, 4 June 2018 (UTC)
: really?[[https://www.google.com/search?q=bleachers&client=firefox-b-1-ab&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjPv-v82LzbAhWLzlkKHUPVByAQ_AUICigB&biw=794&bih=941|really?]][[Special:Contributions/108.162.219.232|108.162.219.232]] 14:07, 5 June 2018 (UTC)

;Magnetic North
I would have liked the "magnetic north" thing to be due to the geographical orientation of the teams home courts (if the Cavaliers are the only team to have a court that happens to be roughly north-south oriented, it would explain the higher points value). Looking at the Stupid Name Arena, however, it appears that the court inside is probably about NW-SE. Too bad. [[User:Chrullrich|Chrullrich]] ([[User talk:Chrullrich|talk]]) 14:15, 4 June 2018 (UTC)
: It is probably referencing how Lebron-led teams always make quick work of the perennially promising Toronto Raptors teams that call themselves "the North".

I was thinking that might be a reference to the Cleveland Cavaliers playing their home games at a slightly high latitude than the (San Fransico-based) Golden State Warriors. (However, they are nearly at the same latitude, and neither is anywhere near 75 degrees North) [[User:JamesCurran|JamesCurran]] ([[User talk:JamesCurran|talk]]) 19:24, 4 June 2018 (UTC)

;SSN to Free Throw%
Would it be too much of a stretch to add in the fact that Stephen Curry's point is highlighted on the chart, as a nod to the fact that (the majority of) one's SSN can actually be determined if one knows details about personal information such as where one was born? [[Special:Contributions/108.162.219.130|108.162.219.130]] 16:08, 4 June 2018 (UTC)
:Not anymore. My three kids were all born in the same hospital -- same wing; rooms only meters apart -- but have TOTALLY different SSN's. (No, I'm not sharing them as proof!) We even asked the local SS office what happened and they said they're starting to reuse numbers at random. I think it's not "reuse" as much as "reallocate", but either way the strict geographical basis is no longer valid. --'''BigMal''' // [[Special:Contributions/172.69.70.209|172.69.70.209]] 16:31, 4 June 2018 (UTC)
:Originally, the first three digits indicated the office where the person requested an SSN. It didn't really signify anything. It was just that each office was given on a block of numbers to assign, and that block all started with the same three digits. Since in the early days of Social Security, a person got theirs, not at birth, but when they first got a job, it was more of an indication of where they happened to be living then, rather than where they were born. By the 60s, SSN assignment had been centralized, but they still tried to maintain the regional number, based on the zip code of the person requesting an SSN. Apparently, they have more recently realized that's just a waste of time and just started issuing them sequentially. [[User:JamesCurran|JamesCurran]] ([[User talk:JamesCurran|talk]]) 19:17, 4 June 2018 (UTC)
::New method started in 2011, so until around 2029 we'll be able to use the "SSN to FT% in NBA" metric, and have it tie to location at time of SSN generation.[[Special:Contributions/162.158.74.165|162.158.74.165]] 21:37, 4 June 2018 (UTC)

Does anyone know what the "sandwiches" graph is a reference to? I don't believe I have heard anything about the Warriors and a love for sandwiches. [[Special:Contributions/172.68.46.101|172.68.46.101]] 17:03, 4 June 2018 (UTC)
:Maybe this? [[https://www.si.com/extra-mustard/2015/04/10/warriors-stephen-curry-45-point-game-sandwich]] [[Special:Contributions/162.158.62.39|162.158.62.39]] 17:23, 4 June 2018 (UTC)

;More on SSN to Free Throw%
I did a quick digitization of the SSN /FT% graph, and the Steph Curry point is at about FT% = 92.5% and SSN ~ 300-XX-XXXX, which corresponds to his 2018 ft% of 92.1% (from wikipedia) and his birthplace of Ohio having a SSN in the range of 268-302 https://www.ssofficelocation.com/social-security-number-prefix . Even if SSN prefixes are random now, they probably weren't when he was born 30 years ago, so it is probably safe to conclude that the location of the point is deliberate. [[User:Acflip|Acflip]] ([[User talk:Acflip|talk]]) 19:01, 4 June 2018 (UTC)
:They changed in 2011 to random generation. I doubt there's any 7 year old NBA players, so until 2029 we'll be able to use this -ahem- metric.[[Special:Contributions/162.158.74.165|162.158.74.165]] 21:34, 4 June 2018 (UTC)

;On the pog collection

Is it possible that the "pog collection" also refers to the player's collection of Player of the Game awards? Lebron James would surely have a staggering amount of it, and Steph Curry would have considerably less, since Steph Curry has a lot of other good teammates.
[[User:Skybreak|Skybreak]] ([[User talk:Skybreak|talk]]) 07:58, 5 June 2018 (UTC)Skybreak

;Best Sport

Lets be real here. The odds of them being better at a sport then basketball are basically nill. Unless you use an unusual definition of "sport" or "better".
[[Special:Contributions/108.162.219.232|108.162.219.232]] 14:07, 5 June 2018 (UTC)

;Shot Map

It may be a reference to the tunnel shot, but it's more likely just a joke about Steph Curry's unusual range for field goals. He's well known for making 3-point shots from much farther out than the average the NBA player. [[User:Hasown|Hasown]] ([[User talk:Hasown|talk]]) 14:57, 5 June 2018 (UTC)
:Thinking about it further, the map doesn't even show any shots from the tunnel, and the tunnel's placement is inaccurate as well. The tunnels to the locker rooms are in the corners of the court, not directly behind the hoop. There are always bleachers behind the hoop for fans to sit. [[User:Hasown|Hasown]] ([[User talk:Hasown|talk]]) 15:03, 5 June 2018 (UTC)