explain xkcd - User contributions [en]

Talk:2111: Opportunity Rover

2026-02-21T21:42:01Z

180.181.250.224:

The subject of this comic, the Opportunity Rover, is being officially declared dead today, the day the comic was released. I wonder how long this comic has been ready, waiting to eulogize the rover. [[User:Blaisepascal|Blaisepascal]] ([[User talk:Blaisepascal|talk]]) 18:03, 13 February 2019 (UTC)
: I'm not crying, you're crying! But seriously, I hope this one becomes a poster... one of my favorite comics in a good long while. --[[Special:Contributions/172.69.46.46|172.69.46.46]] 20:25, 13 February 2019 (UTC)
:: Stop slicing those onions ! [[Special:Contributions/162.158.91.125|162.158.91.125]] 14:12, 14 February 2019 (UTC)
::: :'( [[User:Linker|Linker]] ([[User talk:Linker|talk]]) 20:15, 14 February 2019 (UTC)
:::: TwT [[Special:Contributions/180.181.250.224|180.181.250.224]] 21:42, 21 February 2026 (UTC)
: Yes, more of a paean than "a discussion about ... " the Opportunity rover, and more, it justifies a yearning for the "opportunity" in general to share the knowledge with the world. Uplifting, for me. [[User:PGilm|PGilm]] ([[User talk:PGilm|talk]]) 20:59, 13 February 2019 (UTC)

The fact that the rover ran for 15 years is already magical. He was just designed to last several months (I sincerely use this surname), and people at NASA was suspecting that it may just last days. Yet he worked so hard for us. When I saw the movie about him 10 years ago, I wad SO moved. https://www.imdb.com/title/tt0436595/ All of you should watch it now. I had no idea that I would edit a wiki page about him today.
[[User:Kazeita|Kazeita]] ([[User talk:Kazeita|talk]]) 23:51, 13 February 2019 (UTC)

On one hand, this feels like a subtle nod to xkcd itself. In a sense, a lot of xkcd is Randall's own journal of what he thinks of every so often, and he gets to share it with millions and millions of people.
On the other, "and here's a trench I dug with my wheel" makes me think that Opportunity was using time outside of its feed to slowly but surely dig out an actual 100-meter or so trench. Getting larger. And larger. Until one day, it will rival even the trenches of Earth. And on that day...'''Their''' conquest will have begun. [[Special:Contributions/172.68.78.52|172.68.78.52]] 03:33, 14 February 2019 (UTC)
: The Netherlands? [[Special:Contributions/172.68.65.228|172.68.65.228]] 23:05, 14 February 2019 (UTC)

I'm wondering if Rover is truly "dead". (Is there an explanation in an outside article?) Possibly another device, or some future human expedition, could dust off its solar panels and/or replace the batteries and revive it.[[User:These Are Not The Comments You Are Looking For|These Are Not The Comments You Are Looking For]] ([[User talk:These Are Not The Comments You Are Looking For|talk]]) 05:34, 17 February 2019 (UTC)

In the fourth paragraph of the explanation, there are a couple of sentences about the reference to dust devils. I would submit that the mention of a dust devil in the comic is more likely a reference to this image captured by Opportunity in 2016: [https://www.nasa.gov/image-feature/jpl/pia20012/opportunitys-devilish-view-from-on-high Opportunity's Devilish View from on High]. [[User:MWinter|MWinter]] ([[User talk:MWinter|talk]]) 21:20, 17 February 2019 (UTC)

Talk:246: Labyrinth Puzzle

2026-02-20T05:17:45Z

180.181.250.224:

'''SOLUTION 2 DOES NOT WORK''' ONE QUESTION, NOT TWO, AND YOU DONT KNOW WHO THE LIAR IS. one answer of "this is the door" doesnt help beacuse you wont know the answer of the other guy. in which solution one will always get you the same door, and you pick the other one. solution 2 just gives you two different doors. no matter who you ask you will randomly get a door. if the guy says the truth you wont know that hes the truthfull one or not. AGAIN thruthful guy points to a door, the liar would have( if you asked him instead, OR could even ask both) pointed to the other door. again, asking that question does not give you two answers, because you. dont. know. who. the. liar. is.

'''SOLUTION 2 DOES WORK'''
Solution 2 does work. It IS one question. The question consists of a premise and a concluding statement "If I were to ask you ..." being the premise and "What would your answer be?" being the concluding statement of the question. You are not asking two questions. You are asking ONE question about another question. It may be a logical dodge but it is the SAME logical dodge as the first solution, except that it is asking them about themselves rather than about their brother which takes the form "If I was to ask your brother..." "what would his answer be" In many ways it's neater and more logical and does NOT require the brothers to know how the other would answer.

Solution 1: In mathematical terms takes the form (-1) × (+1) or (+1) × (-1) the result of both being =-1 however for it to work we have to assume that the brother being asked knows what his brother would say. However, nowhere in the question is this usually stated. So we're actualy dealing with either
a × (+1) or a × (-1) with a being an unknown variable which is either +1 or +1 or 0 (zero denoting that the brother doesn't actually know). This is a truer representation of the kind of answer you could expect to get from Solution 1.

Solution 2: As you are asking them about themselves then you are multiplying by themselves in mathematical terms so either (-1)×(-1) or (+1)×(+1). Multiplying either a positive or negative by itself will result in a positive. The brother doesn't need to know what he would answer, he just needs to know what answer HE would give IF he was asked the question.

[[User:SpiroExDeus|SpiroExDeus]] ([[User talk:SpiroExDeus|talk]]) 14:24, 19 November 2020 (UTC)

Just ask which color is the sky.. {{unsigned|‎175.110.37.200}}
:Oh, although the strip doesn't explicitly say so; in those riddles you can normally only ask one question. --[[User:St.nerol|St.nerol]] ([[User talk:St.nerol|talk]]) 23:00, 27 January 2013 (UTC)
::There's another (more traditional) three-guard variation where one guard always tells the truth, one guard always tells a lie and the third alternates between pure truth and pure lie (and you don't know which flip they're currently flopped upon). But you ''still'' only get to ask one question of one guard. Have fun with that one. My personal solution certainly has a degree of convolution, but I've heard other workable answers. [[Special:Contributions/178.98.31.27|178.98.31.27]] 02:24, 21 June 2013 (UTC)
::: I hope no-one considers this a spoiler to say but there is a trivial solution to the 3 guards problem, whether third guard is a spear handler or one that flips between truth and false hood, just try "Did you know that the pub in the village behing the freedom door is serving free beer all day, as long as their stocks last?" Then follow the guards through whichever door they use. Alternatively substitute beer for another commodity the guards may desire. [[Special:Contributions/141.101.98.175|141.101.98.175]] 00:59, 7 November 2016 (UTC)
:::@‎175.110.37.200, you would know which one lies but you would not know which door leads out. [[User:Tharkon|Tharkon]] ([[User talk:Tharkon|talk]]) 23:13, 10 October 2013 (UTC)
::::Eh, well, even if you had a perfect question to ask in this case, a lot of good would that do you: it'd only reveal the truth behind the setup, that ''none'' of the doors lead out. :p -- [[Special:Contributions/173.245.51.210|173.245.51.210]] 08:20, 8 November 2013 (UTC)
:::::Well yes it says that in the title-text. But good pick-up. [[Special:Contributions/108.162.219.58|108.162.219.58]] 02:31, 6 February 2014 (UTC)

One question, of one guard. I really like the original form of this riddle. It's a bit of a trick, though. It is crucial that the guards "know" each other's rules, but this is not even implied. And if it was stated in the question, that would probably be a good enough clue to get you to the answer. Of course, once you know the answer it seems trivial, but I wonder what percentage of people actually worked it out for themselves? Another good one is Monty Hall, even though that is pure, straightforward probability. [[Special:Contributions/108.162.219.223|108.162.219.223]] 18:11, 17 January 2014 (UTC)

:With two guards, they wouldn't need to know each others role. If they know their own role - which they do - each can infer the role of the other. [[Special:Contributions/162.158.34.137|162.158.34.137]] 13:01, 21 April 2016 (UTC)

:I think somebody needs a hug! [[Special:Contributions/108.162.219.223|108.162.219.223]] 18:11, 17 January 2014 (UTC)

The whole problem with this entire riddle is that if they are both liars you are screwed! Nothing in the riddle establishes a fact that they aren't liars. Now if there was a known truth teller in the riddle that explains the nature of the guards or the narrator does it, then the above solution works. {{unsigned ip|108.162.216.28

As you aren't given a limit to the number of questions, you can just ask each guard if they're the stabby guard. If two say yes, the third one is the truthful guard and you can ask him which way the exit is. If two say no, the third one is the lying guard and you can ask him where the exit isn't. No tricky questions so the stabby guard shouldn't stab you.[[Special:Contributions/162.158.255.195|162.158.255.195]] 18:14, 14 August 2015 (UTC)

I have a solution, but you need to ask multiple questions: 
''If the Stab Guard tells the truth:'' 
Ask each guard, firstly, "Are you the Stab Guard?" 
Truth Guard will answer "No." 
Stab Guard will answer "Yes." 
Liar Guard knows the answer is no, but, because he lies, will answer "Yes." 
The one who said no is the Truth Guard, so you can ask him which door leads to freedom. 
''If the Stab Guard lies:'' 
Point to the guard on the left, and ask each guard, "Does that guard lie?" 
If that guard is Truth Guard, then Truth Guard will answer "No," while Stab Guard and Liar Guard answer "Yes." 
If that guard is a liar, then Truth Guard will answer "Yes," while Stab Guard and Liar Guard answer "No." 
Whichever guard gives a unique answer is Truth Guard, so you can ask him which door leads to freedom. [[User:NickOfFørvania|NickOfFørvania]] ([[User talk:NickOfFørvania|talk]]) 23:37, 3 November 2015 (UTC)

:It's been solved on puzzling.stackexchange.com (given a specific definition of a tricky question): http://puzzling.stackexchange.com/questions/43092/xkcd-inspired-logic-puzzle [[Special:Contributions/141.101.98.130|141.101.98.130]] 12:14, 24 September 2016 (UTC)

I remember a book where the main character kicked one guard in the face and asked if it hurt. {{unsigned ip|162.158.252.137}}
:In a Percy Jackson book, one tells the truth, one lies, and one says something COMPLETELY random. (but the doors all lead to the same place anyway)

There's another unspoken rule: That the lie is either a yes or a no. If you asked the liar something, he could lie and say, "I don't know," which would leave you with nothing. Also, as Stabby MacStabberson does not appear to have any restrictions on what he tells you (that is, he has the choice between truth or falsehood,) there's no sure way out even if he wasn't tasked with stabbing you.[[Special:Contributions/162.158.255.69|162.158.255.69]] 05:32, 30 April 2016 (UTC)

Who said the Stab Guard has a true sense of complex? He could just stab you anytime. [[User:Dontknow|Dontknow]] ([[User talk:Dontknow|talk]]) 00:37, 16 March 2017 (UTC)

What's wrong with "Are you gonna stab me?"? They'll either answer or not and stab you or not, that's around 2 bits, which seems like it should maybe help decide in a space of 3. I ask Lie, he says yes, yet doesn't stab me. I ask True, he says no, and doesn't stab me. I ask Stabby, and he says no and doesn't stab me because it's a really simple question. [[Special:Contributions/108.162.216.48|108.162.216.48]] 16:44, 29 December 2020 (UTC) with [[Special:Contributions/108.162.216.48|108.162.216.48]] 16:44, 29 December 2020 (UTC)

Here's a solution, but it's quite stupid, and might not work, depending on if the guards appreciate their mothers:
Just ask a random guard, point to another, and say this: "That guard told me your mom was wearing their shirt last night!"
Then stand back, and let the chaos ensue.[[Special:Contributions/108.162.216.126|108.162.216.126]] 16:14, 25 November 2019 (UTC)

"What would you say is the way out?" It doesn't seem tricky, but it's actually a meta-question. The guard knows what they would say is the way out. If the guard tells the truth, they would say the correct door. The guard tells the truth about telling the truth and says the correct door. If the guard lies, they know they would lie about what the correct door is. The guard lies about lying and says the correct door. [[Special:Contributions/162.158.79.47|162.158.79.47]] 21:19, 3 February 2020 (UTC)

Assuming there are three doors (as shown in the picture), at least one door leads out, and at least one door does not, the single non tricky question of "Which doors lead out?" will always yield a useful answer. For two safe doors, if two door are pointed at, they are safe. if one door is pointed at, it's deadly. If only one door is safe, it's the opposite. If there are only two doors, (as in the standard puzzle) there's nothing you can door, as any question that both the liar and the truth teller would answer identically and tells you which door to go through is a tricky question. [[Special:Contributions/172.68.37.38|172.68.37.38]] 23:42, 2 May 2021 (UTC)
:Assuming only "door 1" leads out and I ask the liar "which doors lead out?", he may give any answer apart from "door 1", e.g. "all doors" or "doors 1 and 2" - this is not helpful. Similarily for 2 safe doors the answer to "which doors lead out?" could be a lie without of being the complete opposite of truth. (e.g. doors 1/2 lead out, liar could say 1/3 lead out - not useful) --[[User:Lupo|Lupo]] ([[User talk:Lupo|talk]]) 07:56, 3 May 2021 (UTC)
::In this soft of puzzle, lies are usually defined as the complete opposite of the true answer. Relaxing this constraint usually makes a puzzle like this completely unsolvable with a single question. With it in, the opposite of two safe doors is one death door, which lets you identify the two different possible statements for each possible combination of doors as truth or lie.[[Special:Contributions/73.151.32.230|73.151.32.230]] 20:16, 4 August 2025 (UTC)

My friend Umnikos came up with a solution for the version where the stabber acts randomly or adversarially for nontricky questions (tricky questions are those that could be used on their own to determine whether the stabber is lying, or to extract information without knowing whether someone is lying).

Q1: "does door 1 lead to freedom?"

Two guards will answer in one way, the third in another.

to the third, unique guard:

Q2: "if I asked you if door 1 lead to freedom, would you say yes?"

Q3: "if I asked you if door 2 lead to freedom, would you say yes?"

Q4: "if I asked you if door 3 lead to freedom, would you say yes?" [[User:AndrewTheXKCDer|AndrewTheXKCDer]] ([[User talk:AndrewTheXKCDer|talk]]) 18:49, 26 June 2021 (UTC)

;Does the actual Labyrinth Puzzle's solution work?

First of all, both of the gaurds in the Liar-Truthteller solution don't necessarily have to answer your question. And even if the fact that they have to answer your question was implied, couldn't the liar just say that none of them lead out? {{unsigned ip|172.70.211.129|18:43, 16 February 2024}}

Talk:1134: Logic Boat

2026-02-01T03:27:59Z

180.181.250.224:

Why not take the boat as well? The goat could drag it around, and you could use it as a makeshift shelter until you finish building a proper house. Also, why does cabbage weigh as much as a goat? [[User:Davidy22|Davidy22]][[User talk:Davidy22|<tt>(talk)</tt>]] 05:50, 14 November 2012 (UTC)

:Or-stay on this side. What's wrong with this side? [[Special:Contributions/172.68.46.41|172.68.46.41]] 06:33, 5 June 2018 (UTC)
I'd say that the wolf is the only one amongst them he should keep. Seeing as how the wolf doesn't treat Cueball like the goat--i.e. rip him to shreds--and actually fears him enough to even respect the goat in his presence, I'd say that the wolf is well broken-in and might make a good companion. The goat, on the other hand, is just dead weight. (Sure, Cueball could eat her, but that's why he has the cabbage.)
[1] Take the cabbage across [2] Return alone [3] Find the goat problem solved--and your friend well-fed [4] Take the wolf across [[Special:Contributions/207.237.164.241|207.237.164.241]] 06:33, 14 November 2012 (UTC)
::I am not the only one, then! I like wolves a lot more than goats. Then again, I simply like wolves. [[User:Greyson|Greyson]] ([[User talk:Greyson|talk]]) 03:48, 15 November 2012 (UTC)
::::They're like puppies! Except instead of love them, you have to occasionally beat the shit out of them to ensure that they continue to fear and respect you. Oh, and instead of love you back, they sometimes physically challenge your authority over the "pack". But yeah, they're all around awesome. [[Special:Contributions/207.237.164.241|207.237.164.241]] 09:42, 15 November 2012 (UTC)
::::::...
::::::I compare such a relationship (especially the "beat up the wolf in order for the wolf to fear you") to [[574:_Swine_Flu|Untoward's relationship with a pig.]] [[User:Greyson|Greyson]] ([[User talk:Greyson|talk]]) 15:03, 19 November 2012 (UTC)
::::::: Wolves are awesome in Minecraft just as in real life. And all you need is bones and rotting meat. [[Special:Contributions/108.162.218.101|108.162.218.101]] 23:01, 10 March 2014 (UTC)
::You're never alone with a goat - ask Alexander Selkirk. [[Special:Contributions/86.25.154.116|86.25.154.116]] 13:03, 25 October 2013 (UTC)
Why would cabbage count towards the total capacity of the boat? Take the wolf and the cabbage, return alone, take the goat.--[[Special:Contributions/69.197.220.27|69.197.220.27]] 08:08, 14 November 2012 (UTC)
::Maybe it's a sentient boat that knows how many passengers/objects are aboard no matter their weight?--[[User:Dangerkeith3000|Dangerkeith3000]] ([[User talk:Dangerkeith3000|talk]]) 16:09, 14 November 2012 (UTC)

The comments describing other shortcuts are really just emphasizing the joke in this comic. The logic puzzle introduces arbitrary constraints and asks the solver to come up with a solution. (This is reminiscent of the classic xkcd on [[356|Nerd Sniping]].) Most normal people would have the responses you listed about the constraints being arbitrary, but the people vulnerable to Nerd Sniping (i.e. nerds) usually are willing to ignore reality to solve a puzzle with artificial constraints. The purpose of the puzzle is to encourage logical thinking. (Maybe I should take the wolf first so it can't eat the goat. Oh, but then the goat would eat the cabbage. But if I take the cabbage first, the wolf would eat the goat. Therefore, I must take the goat first. ... Continue reasoning with trial and error until the puzzle is solved...) However, you correctly are pointing out how artificial the constraints on the puzzle are. In the actual comic, the solution of leaving the wolf behind would come as a humorous surprise to the nerd following along coming up with a solution. [[User:S|S]] ([[User talk:S|talk]]) 00:07, 15 November 2012 (UTC)
::And that would be the long way towards the 'Explanation' section [[Special:Contributions/207.237.164.241|207.237.164.241]] 09:42, 15 November 2012 (UTC)
::I don't think you attitude is as common as you're claiming it is, nor that it is the central joke of the comic, which is probably just about the unlikeliness of the scenario. Here's[[https://www.youtube.com/watch?v=DDzTyOJSe-Y]] a clip of a comedy episode where 'normal people' are trying to solve the problem straight and a nerd is missing the point.[[Special:Contributions/162.158.155.74|162.158.155.74]] 13:11, 23 July 2017 (UTC)

I see this as a play on the common use of “logical” to mean “consistent implicit goals or values,” as oppose to “consistent with the principles of inference” as in formal logic. For example, it's the former usage we see when Spock in Star Trek II says, “Logic clearly dictates that the needs of the many outweigh the needs of the few,” or in Star Trek IV, he says, “To hunt a species to extinction is not logical.” You leave the wolf because it’s not logical to hang around wolves longer than necessary –they’re dangerous. Of course, this usage of “logic” is highly relative and subjective (in contrast to formal logic). As some have argued, wolves are not only logical, but awesome. Title text drills home how subjective and relative this use of “logic” is. It’s not logical to take the cabbage because I don’t like cabbage. But I like goats so they “make sense.” --[[User:Emzed|Emzed]] ([[User talk:Emzed|talk]]) 18:40, 30 November 2012 (UTC)

Everybody knows the classic wolf, sheep and cabbage problem, but I just realized that this is not same problem! Just read the first panel: you have the constraints that the boat can carry two and you can't leave the goat with the cabbage or the wolf with the goat as in the classic problem, but nowhere is stated that you must reach the other side with the other three! You can just do nothing, or carry the sheep on the other side and go away with the boat...
--[[User:Sandman|Sandman]] ([[User talk:Sandman|talk]]) 20:02, 16 November 2012 (UTC)

:The problem actually doesn't state any requirement. An equally valid solution would be you starve to death, the cabbage rots to slime and the goat runs away while the wolf tears strips of flesh from your corpse. [[Special:Contributions/216.52.207.104|216.52.207.104]] 23:23, 5 December 2012 (UTC)

::Alternate Solution: Share the Cabbage with the goat. The wolf obviously respects you, so take it with you to make your pet. Don't let the goat ride- make it swim. {{unsigned|66.220.143.177}}

:::When I was a kid, we used the version with a dog, a chicken, and a bushel of corn. Being a farm kid, my solution was: take chicken, shoot dog, take corn. Because why the hell do you have a dog that eats chickens? Also, tie your bag o'corn up properly so a chicken couldn't get in. They're not that smart. And they cannot eat a bushel of corn in the time it takes you to cross a river and come back. Also, how did you manage to get to this point without everybody eating each other? Why isn't the chicken in a cage? That could protect it from getting eaten. Is it just sitting quietly awaiting your command? Won't it just wander away once you get it to the other side?
To the above: Goats HATE water. They do not swim well either. I think the wolf should swim.
My solution to the wolf/goat/cabbage is to tether the goat and the wolf far away from each other, whichever side they may be on. --[[Special:Contributions/184.21.245.225|184.21.245.225]] 22:29, 17 February 2013 (UTC)

Goats eat cabbage..
[[Special:Contributions/24.59.184.243|24.59.184.243]] 09:18, 13 January 2013 (UTC)
:Hmm... what is to keep the human from eating the cabbage?
:Send the wolf with the cabbage across and let the boat drift back, and then have the human go across with the goat. 3 steps. The real challenge of this puzzle is teaching your wolf to paddle the boat across. [[User:Zyxuvius|Zyxuvius]] ([[User talk:Zyxuvius|talk]]) 09:55, 25 October 2013 (UTC)

Fastest solution: Get the goat in the boat, drop the cabbage in the water, row boat across, periodically pushing the cabbage in the direction of the shore with your oars. 1 step. [[Special:Contributions/199.27.128.150|199.27.128.150]] 04:52, 10 January 2014 (UTC)

The river isn't that wide. Couldn't you just throw the cabbage across, then return and get the wolf, then return and get the goat? Or just leave the cabbage. [[User:Jake|Jake]] ([[User talk:Jake|talk]]) 14:37, 20 January 2014 (UTC)

Why wouldn't the wolf eat the cabbage? And why would the cabbage's presence stop the wolf from eating the goat (or does it not stop it)? [[User:Z|Z]] ([[User talk:Z|talk]]) 22:01, 3 August 2014 (UTC)

: Only the humans presence stops the wolf eating the goat, or the goat eating the cabbage. --[[User:Pudder|Pudder]] ([[User talk:Pudder|talk]]) 12:11, 31 October 2014 (UTC)

I've always heard this as a dog-chicken-corn problem. {{unsigned ip|108.162.216.190}}

This is the only website I've heard call it "wolf-goat-cabbage". Even wikipedia doesn't call it that anymore. And the trope is http://tvtropes.org/pmwiki/pmwiki.php/Main/FoxChickenGrainPuzzle - [[Special:Contributions/162.158.214.58|162.158.214.58]] 04:35, 22 July 2017 (UTC)

THROW THEM ALL ACROSS!!![[Special:Contributions/180.181.250.224|180.181.250.224]] 03:27, 1 February 2026 (UTC)

Talk:14: Copyright

2026-01-24T20:47:02Z

180.181.250.224:

First world problems. '''[[User:Davidy22|Davidy22]]'''[[User talk:Davidy22|<tt>[talk]</tt>]] 14:09, 8 January 2013 (UTC)
:Yeah, definitely! :D A funny thing is that according to [http://knowyourmeme.com/memes/first-world-problems Know Your Meme Google statistics] the "first world problems"-thing started in 2011, but in Sweden we've had jokes about "I-landsproblem" all since {{w|Hipphipp!}} (a hilarious Swedish humor show) ran back in 2001/2003. –[[User:St.nerol|St.nerol]] ([[User talk:St.nerol|talk]]) 17:28, 8 January 2013 (UTC)

does this mean i'm a criminal? i pirated minecraft and ksp [[User:An user who has no account yet|An user who has no account yet]] ([[User talk:An user who has no account yet|talk]]) 10:28, 7 September 2023 (UTC)
Has anyone noticed that *Kirby* often sits under an oak tree (it's how a lot of games start and end) [[Special:Contributions/180.181.250.224|180.181.250.224]] 20:47, 24 January 2026 (UTC)

3181: Jumping Frog Radius

2025-12-30T21:54:50Z

180.181.250.224: 1 cm = 10 mm, so Earth Schwarzschild radius is closer to 1 cm than 2.

{{comic
| number = 3181
| date = December 15, 2025
| title = Jumping Frog Radius
| image = jumping_frog_radius_2x.png
| imagesize = 339x243px
| noexpand = true
| titletext = Earth's r_jf is approximately 1.5 light-days, leading to general relativity's successful prediction that all the frogs in the Solar System should be found collected on the surface of the Earth.
}}

==Explanation==
{{incomplete|This page was created by an A frog stuck on mars. Don't remove this notice too soon.}}
The {{w|Schwarzschild radius}} is essentially the size of a {{w|black hole}} -- the maximum distance from the center where gravity is so strong that light can't escape. It is part of a solution to {{w|Einstein's field equations}}. It is usually calculated as
:''r''s = (2*''G*M'') / ''c''2
where ''G'' is the {{w|gravitational constant}}, ''M'' is the mass of the object, and ''c'' is the {{w|speed of light}}.
If ''M'' were the mass of the {{w|Earth}}, it would give the Schwarzschild radius for the Earth, which is about 9 mm. (If all of Earth's mass were compressed into a sphere of a bit less than 1 cm in diameter, it would become a black hole.)

The comic suggests a more useful radius: the ''Jumping Frog radius'' ''r''jf, which is the size of a "planet" such that its gravity keeps a champion {{w|Frog jumping contest|jumping}} {{w|The Celebrated Jumping Frog of Calaveras County|frog}} from being able to achieve {{w|escape velocity}}. Thus [[Randall]] has instead of ''c'', the 299,792,458 m/s speed of light, used a much smaller value of 4.5 m/s, to represent the maximum speed of a jumping frog. It is possible that Randall got that value from [https://www.researchgate.net/publication/5661154_Explosive_Jumping_Extreme_Morphological_and_Physiological_Specializations_of_Australian_Rocket_Frogs_Litoria_nasuta this paper], which on page 179 puts an upper limit on the maximum velocity of adult Australian {{w|striped rocket frog}}s at 4.52 m/s. (The frog is shown making a "ribbit" sound, which is made by {{w|Pacific tree frog}}s and their relatives in North America and not by rocket frogs, but it's [https://www.imdb.com/list/ls052470723/ widely attributed to frogs all over the world].)

The drawing to the right of the formula shows a planet with exactly the radius ''r''jf. Thus the frog can jump really high compared to the planet's size (in this case about as high as the planet's radius), before it falls back down. This implies that the frog is jumping at somewhat less than the 4.5 m/s needed to escape.

The title text points out that the ''r''jf of the Earth is about 1.5 light days, which is about 7 times the distance to {{w|Pluto}} (compare to the 9 mm Schwarzschild radius). Since Earth's radius is much smaller than this, no frogs will be able to escape, so all frogs that stray into Earth's gravitational well would collect here on Earth. As far as we know, all the frogs in the Solar System are on Earth{{Citation needed}}, so the data apparently matches the theory. However, the reasoning is incorrect, as many other astronomical bodies in our solar system also have ''r''jf greater than their physical radius. If a frog were to be on any of those other bodies, it wouldn't be able to jump away to fall to Earth. A flawed argument neither supports nor refutes the conclusion, although it is true as far as we know that all frogs in the solar system do live on Earth.

If you were to take a frog off the earth and put it in a tiny frog space suit, which somehow did not unduly inhibit its movement, it could jump off any number of the smaller bodies in the solar system. However, few of these bodies are small/low-mass enough for a frog to escape them, ''and'' large enough and close enough for us to observe them and accurately estimate their escape velocities. (The diameter of asteroid {{w|4942 Munroe}} is known to be about 3.45 km, but its shape and mass are unknown. Its surface has an [https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=2004942 exceptionally high albedo of 0.936], which suggests that the surface is mostly some kind of ice. If we assume that asteroid Munroe is spherical and entirely composed of water ice, with a density close to 1 g/cm3, its mass is 2.16 × 1010 kg, and its escape velocity is 0.041 m/s. If instead it's a solid sphere of meteoric iron/nickel with a density of about 8 g/cm3, its mass is 1.72 × 1011 kg, and its escape velocity is 0.115 m/s. In either case, Space Frog would have no trouble jumping away from Munroe.) Some examples:

{| class="wikitable"
!Celestial Body!!Escape Velocity (m/s)!!Frog Escape?!!Notes
|-
|Deimos||5.6||X||The smaller of Mars's two moons
|-
|Ersa||ca. 1||✓||Minor moon of Jupiter
|-
|Halley's Comet||ca. 2||✓||Notable comet, orbiting the sun every 76 years
|}

==Transcript==
:[The panel shows a large formula to the left and a small drawing to the right. The formula's right side is drawn above and below the division line:]
:''r''jf = 2''GM'' / (4.5 m/s)2

:[The drawing to the right shows a very small planet with the radius indicated with a labeled dotted arrow pointing from the center straight up to the edge of the planet. A frog is shown jumping on the surface. This is indicated with a parabolic dotted line going from a frog sitting on the surface near the top of the planet, up to the frog shown soaring through the air with its limbs stretched out about as high above the surface as the planet's radius. At this point the frog is making a sound. Then the dotted line goes down to about a quarter of the way around the planet where the frog lands making a noise, with lines around the frog representing the impact.]
:Arrow label: ''r''jf
:Frog: Ribbit
:Landing: Plop

:[Caption below the panel:]
:More practically useful than the Schwarzschild radius, the '''''Jumping Frog Radius''''' is the radius at which an object's gravitational pull is so strong that even a champion jumping frog can't escape.

{{comic discussion}}<noinclude>
[[Category:Physics]]
[[Category:Astronomy]]
[[Category:Animals]]

Talk:2607: Geiger Counter

2025-12-15T20:57:09Z

180.181.250.224:

Vanilla joke, but funny. [[User:Nafedalbi|Nafedalbi]] ([[User talk:Nafedalbi|talk]]) 18:41, 15 April 2022 (UTC)Nafedalbi
:It's Randall's "dad joke". [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 19:23, 15 April 2022 (UTC)
:Honestly, yeah. I impulsively went "wow... Randall's really jumped the stick figure shark." --[[Special:Contributions/172.70.110.121|172.70.110.121]] 06:32, 16 April 2022 (UTC)
::Not me. After plumbing the depths of Unicode and trying to describe a Taylor series expansion from square one, this is a welcome relief. [[Special:Contributions/172.70.214.81|172.70.214.81]] 07:34, 16 April 2022 (UTC)
: When does an ordinary joke become a dad joke? When it becomes apparent. [[Special:Contributions/172.70.130.121|172.70.130.121]] 10:31, 16 April 2022 (UTC)
::When does it become apparent? After the delivery. [[Special:Contributions/172.69.33.223|172.69.33.223]] 17:30, 16 April 2022 (UTC)
:::When is the best time for delivery? After a pregnant pause. [[Special:Contributions/172.70.178.199|172.70.178.199]] 15:19, 17 April 2022 (UTC)
::Many dad jokes will not become apparent until they are full groan. [[Special:Contributions/172.70.210.189|172.70.210.189]] 15:03, 18 April 2022 (UTC)

Randall, come here. Yes, right there. Stand still. THWACK! THWACK THWACK THWACK THWACK THWACK! That is all, you may go now. 20:41, 15 April 2022 (UTC)

The explanation makes clear the side of the pun regarding the Geiger counting clicking, but for non-native English speakers, the phrase "it clicked" meaning "I understood" may need clarification. [[Special:Contributions/162.158.166.213|162.158.166.213]] 21:17, 15 April 2022 (UTC)

Also possibly related to this news story https://www.reuters.com/world/europe/unprotected-russian-soldiers-disturbed-radioactive-dust-chernobyls-red-forest-2022-03-28/

Calling the pun a parody of another joke is weird. Jokes aren’t parodied. Parodies aren’t made of general things people say. It can be a ''play on'' that other joke, but not a ''parody'' of it. It’s not ''making fun'' of the other joke. [[Special:Contributions/108.162.245.69|108.162.245.69]] 11:24, 16 April 2022 (UTC)
:I somewhat agree with you. It's a 'type of' pun related to the Tom Swifty, which I edited in just now. I didn't actually remove the claim of parody. Perhaps someone else should also do that without hesitation... (...says I, unerringly!) [[Special:Contributions/162.158.159.43|162.158.159.43]] 15:06, 16 April 2022 (UTC)

Dates for the Trinity Site Open House are April 2 and October 15 for 2022. Bring your own geiger counter. [[User:TCMits|TCMits]] ([[User talk:TCMits|talk]]) 14:15, 16 April 2022 (UTC)
:...and possibly a time-machine? ;) [[Special:Contributions/162.158.159.43|162.158.159.43]] 15:06, 16 April 2022 (UTC)

== Title text: birds sitting on the wire ==

"Sitting/standing on the wire" is a German idiom ("Auf der Leitung sitzen/stehen"), translated to English literally. It means to not understand something, and is used primarily with concepts that supposedly are easy to understand. For example, not getting a joke. The birds are not part of the German idiom itself. Birds were chosen because they can sit on wires literally (think: Alfred Hichcocks' movie), yet also understand (or not understand) something and thus be subject of the idiom. It's quirky but somewhat works for the joke. If you want to carry on with the idea of literally-translated German idioms, the word "birds" can refer to "funny/strange people". The title text then translates to: "At first I didn't get why they were warning me about all those funny people who didn't get it, but then I understood." [[Special:Contributions/141.101.69.46|141.101.69.46]] 22:10, 3 June 2022 (UTC)

I do not understand the joke in the title text, so if somebody could please write an explanation, that would be great.
Also, this is my first ever full comic description! Yay!
I don't know what categories this fits in, if somebody could also put those in that would be great. [[User:MrYellow04|MrYellow04]] ([[User talk:MrYellow04|talk]]) 19:58, 15 April 2022 (UTC)
:I suggest you stand under a wire with lots of birds on it for a while. It will hit you. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 20:32, 15 April 2022 (UTC)
:Dirty birdy in the sky, why you do that in my eye? Boy I'm glad that cows can't fly! [[User:TCMits|TCMits]] ([[User talk:TCMits|talk]]) 14:15, 16 April 2022 (UTC)
::I thought they were canaries (toxic gas)
I thought it meant the birds were dangerously mutated because of the radioactivity, but now I understand. [[Special:Contributions/172.69.34.84|172.69.34.84]] 22:00, 15 April 2022 (UTC)
:Just make sure you don't open your mouth and tilt your head back. [[Special:Contributions/172.70.90.63|172.70.90.63]] 22:59, 15 April 2022 (UTC)

The title text joke may be understood more easily by reading "stood under" in place of "understood". [[Special:Contributions/162.158.107.124|162.158.107.124]] 19:37, 15 April 2022 (UTC)

Living in Manhattan, you learn to notice when an area is full of bird droppings and avoid standing there. You also need to pay attention when parking your car. Certain lamp posts (where the lamp is cantilevered over the street) near Central Park often tend to have a large accumulation under them. [[Special:Contributions/108.162.246.178|108.162.246.178]] 19:47, 15 April 2022 (UTC)

I added telegraph wires (UK-only term, possibly, and anachronistic as they are telephone cables, so feel free to change to be US-centric) and birds seem happy to sit on pole-suspended POTS cables as much as power-lines, so the linked heat-effect thing is definitely a minority necessity. I think it's just a perch. Though we probably have more signal-wires. Most(?) streets more than a few decades old have telegraph poles feeding wires to established properties (even if cable/FTTP has been dug into trenches) but mains electricity tends to have been subsurface for much longer, with only HV national/rural-area transmission grids up on pylons/poles. Obviously there ''are'' a lot more perching birds out in the countryside, where they may dominate (but still the 'telegraph' may follow road or rail routes to service the villages and isolated inhabitations along them) but you don't tend to see birds atop the larger lines at all... Too high up? ''Too'' hot? I've seen rooks/etc happily doing a Hitchcock upon a pylon itself, apparently enjoying the communal view. [[Special:Contributions/172.70.90.63|172.70.90.63]] 18:54, 15 April 2022 (UTC)

== Leonard Cohen reference? ==

It seems to me that the title text has to be somehow referencing one of Leonard Cohen’s better known songs, “Bird on the Wire”, from the very specific phrasing there. [[Special:Contributions/108.162.245.69|108.162.245.69]] 11:21, 16 April 2022 (UTC)
: It's a fairly common phrase. Including the 1990 Goldie Hawn / Mel Gibson [https://g.co/kgs/QZ6LpN film]. [[User:Iggynelix|Iggynelix]] ([[User talk:Iggynelix|talk]]) 16:23, 16 April 2022 (UTC)

:I think it more likely there's some reference meant to birds not getting electrocuted while sitting on power cables-perhaps this is even in a "What If" book? I don't think very likely, but more likely than any Leonard Cohen reference. It's because "both the bird's feet are on the same potential, so electricity does not flow through the bird. The bird also offers greater resistance than the power cable, so the electricity continues to flow through the power cable." I figured this "explanation" fits here as well as anywhere. [[User:Cuvtixo|Cuvtixo]] ([[User talk:Cuvtixo|talk]]) 21:06, 16 April 2022 (UTC)
::I think it's a red-herring that the nature of the wire has ''anything'' to do with it. Birds will perch on handy things, whether electrical cables (hopefully with spacings between separate phase-wires/across the insulator 'hangers' significantly more than an idle wing-stretch!), telephonic, washing line, zip-line, etc, etc. A wire just gives more chance for 'mostly open space, beneath which an unaware human is particularly (but not obviously) susceptible to birds voiding their systems' than with a street-lamp arm, a high ledge on a tall building, tree branches or the underside frames of girder-based bridges.
::Birds do indeed escape (trivial) electrocution on power-lines, but that doesn't help the joke because they can crap on you from ''anything'' that you under-stand (or just by chance, by dint of being birds and occasionally finding they need to let go whilst already in flight... or by direct malice in the case of nest-guarding skuas/etc).
::Not to disect the comedy frog, or anything, because that would be cold-blooded. [[Special:Contributions/172.69.79.223|172.69.79.223]] 00:00, 17 April 2022 (UTC)

"Pretty sure eggrolled was just a typo", as corrected with [https://www.explainxkcd.com/wiki/index.php?title=2607:_Geiger_Counter&diff=prev&oldid=230619 this edit]... No, I think not. I've just undone a whole host of (repeated) vandalisms, some of which were to put "eggroll" in as replacements... the rest were equally stupid (or greater). Check edit log for just before now to see what pages I reverted/etc. Because someone is apparently clever enough to edit wiki pages (oh boy, what a smart person, I'm sure nobody of lesser intellect could ''ever'' have accomplished such a thing(!)...). Anyway, good work recorrecting it, whoever you are. [[Special:Contributions/172.69.79.223|172.69.79.223]] 00:15, 17 April 2022 (UTC)

At first I didn't understand why they were warning me about the boomerang, but then it hit me... (Yes, I may have stolen that joke from Milton Jones.) --[[User:IByte|IByte]] ([[User talk:IByte|talk]]) 09:02, 17 April 2022 (UTC)

I swear I've seen this exact comic before, why was it reposted? [[User:IJustWantToEditStuff|IJustWantToEditStuff]] ([[User talk:IJustWantToEditStuff|talk]]) 20:43, 23 January 2023 (UTC)