explain xkcd - User contributions [en]

1603: Flashlights

2015-11-16T19:15:50Z

108.162.221.48: /* Explanation */ "often" is too much. There are 1604 xkcd comics and only 4 times is related with fleshlights.

{{comic
| number = 1603
| date = November 13, 2015
| title = Flashlights
| image = flashlights.png
| titletext = Due to a typo, I initially found a forum for serious Fleshlight enthusiasts, and it turns out their highest-end models are ALSO capable of setting trees on fire. They're impossible to use without severe burns, but some of them swear it's worth it.
}}

==Explanation==
In this comic, [[Cueball]] has acquired or built a new high powered {{w|flashlight}} ("torch" in British English), which he wants to demonstrate to [[Megan]]. When Cueball refers to older flashlights as dim and finnicky, this gives reason to assume that the flashlight he is holding is going to be ridiculously overengineered.

Indeed, when he switches it on outside the house, the intense light beam completely drowns out the scene. Only the reflected light from the forest lights up the part of Cueball and Megan's faces that are turned towards it. Megan is holding up a hand, apparently to shield her eyes.

Cueball comments that the flashlight lights up the entire forest, but Megan observes that it is the trees that are on fire, indicating that Cueball's flashlight is so overpowered that the energy of its beam is sufficient to cause the organic matter of trees to combust.

Of course, a flashlight that cannot safely be pointed at things is fairly useless for the traditional purpose of a flashlight, which would be to find things in the dark by directing light over them. This mundane and practical reasoning does not seem to matter to Cueball of course, who appears only interested in the intensity and brightness the device is capable of achieving.

Cueball might allude to a number of technical improvements, notably xenon-based incandescent bulbs, multiple-LED assemblies, Lithium batteries (usually used for photography flashes) or rechargeable batteries. A number of companies market "tactical" flashlights that are supposedly powerful enough to incapacitate an opponent, using terms such as "scorching" to advertise their products. See for instance this video about a [https://www.youtube.com/watch?v=NiKzrnKR3Ts Wicked Lasers Torch] of the brand [http://www.wickedlasers.com/torch Torch] that ignites paper and melts stuff. Not strong enough to put a forest on fire but it is not safe to point at anything close by!

[[Randall]] has also looked at what lasers could do of damage in two [[what if?]]: [https://what-if.xkcd.com/13/ Laser Pointer] and [http://what-if.xkcd.com/119/ Laser Umbrella].

The title text refers to {{w|Fleshlight}}, a brand of male masturbation toys modeled after various human orifices (typically female). Cueball (or Randall) claims that he only arrived on a forum for Fleshlight enthusiasts due to a typo. Apart from the "e" vs. "a" in Fleshlight, they are also fashioned to look like oversized flashlights. On that forum he found out that the highest-end models of their product lines was also capable of setting trees on fire. This would probably happen due to violent vibrations inside the orifice, or excessively powerful internal heating. Anything powerful enough to burn trees would indeed cause the user severe burns in a very unpleasant area. But some of the enthusiasts swear that it is still worth it, in the same manner that Cueball only cares about the intensity of the flashlight, regardless of the consequences. Maybe they are just trying to trick you into doing something stupid! Or maybe they're just into that kind of thing.

A fleshlight has previously been featured in [[1397: Luke]], where one is believed to be a laser sword (that would burn!) And they are also mentioned in [[141: Parody Week: Achewood]] and [[600: Android Boyfriend]]. So they are something that has entered in Randall's mind at least 4 times.

==Transcript==
:[Cueball carries a flashlight walking towards Megan who is sitting on a couch]
:Cueball: Remember how flashlights sucked when we were kids? Always dim and finnicky?
:Megan: I guess?

:[Cueball and Megan walking to the left]
:Cueball: Well, I discovered there are now internet flashlight enthusiasts.
:Cueball: And the technology has... improved.
:Megan: OK, Let's see.

:[It is dark outside where Cueball turns on the flashlight. The beam is very bright and very visible even seen from the side. Backscattered light reflects off Cueball and Megan's faces, turning them into bright white beings in the dark. The facade of the house and the stairs are also visible in the same manner, with deep dark shadows where anything is in the shadow. Megan averts her face from the light holds up a hand to cover her eyes. When the flashlight turns on it even makes a sound, written in white above the beam:]
:Flashlight: '''''FWOOSH'''''

:[Cueball and Megan look at what the beam falls on (outside the frame). Megan has taken her hand down. Both their faces are only lit up like a crescent moon. Cueball is holding the flashlight with both hands as if it is pushing back on him. The text is written in white on the dark sky above them.]
:Cueball: See how it lights up the whole forest?
:Megan: ... The trees are on fire.
:Cueball: Real bright, though.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics with inverted brightness]]
[[Category:Sex]]

Talk:1537: Types

2015-06-13T19:24:14Z

108.162.221.48:

Relevant: WAT talk https://www.destroyallsoftware.com/talks/wat {{unsigned ip|‎108.162.254.108}}

Are (6) and (7) about completing sequences?

If the sequence was [1, 2, 3, ?] we would expect the ? to be a placeholder for 4. So [1, 2, 3]+2 is wrong := FALSE. But [1, 2, 3]+4 is correct := TRUE. {{unsigned ip|141.101.99.22}}

"+2 appears to be applying a unary + to the number 2" : or it adds the number of the line, 10, to 2 => 12. Also, the eleventh line, "2+2" may add 2 to all the following 2, explaining line 12. (that theory is from a friend of mine) [[User:Seipas|Seipas]] ([[User talk:Seipas|talk]]) 12:17, 12 June 2015 (UTC)
: Also, for the lines 6 and 7, the operation "[1,2,3]+x" may add x to the set [1,2,3] and return true if the operation succeeded or false if not. Adding 2 to the set [1,2,3] returns false because 2 is already in [1,2,3]. [[User:Seipas|Seipas]] ([[User talk:Seipas|talk]]) 12:23, 12 June 2015 (UTC)
:: I thought it was doing element-wise addition and then comparing "[6] > [3,4,5]" (using the line number in the joke, like in line 10). The problem here is that line 6 should return true and line 7 should return false. [[User:Rand|Rand]] ([[User talk:Rand|talk]]) 15:46, 13 June 2015 (UTC)

Yellowish Blue: http://www.livescience.com/17948-red-green-blue-yellow-stunning-colors.html is NaN! {{unsigned ip|108.162.221.129}}

''"The ironic thing is that fractions with 2 in the nominator are not the kind of numbers that typically suffer from floating point impreciseness."''
- This is not technically correct. Should read "fractions with 'power of 2' in the '''de'''nominator. However, the 3/2 would cause precision errors. {{unsigned ip|108.162.221.129}}
: I don't know proper English wording for things, but 3/2=3*2^-1, so it would be represented exactly under IEEE-754 too. [[Special:Contributions/141.101.89.217|141.101.89.217]] 13:58, 12 June 2015 (UTC)

Is there more to this comic, a fixed set of rules that can tie all the examples together, or does each line make its own joke independently? [[Special:Contributions/108.162.219.5|108.162.219.5]] 12:54, 12 June 2015 (UTC)

;"normally"

<blockquote>This would make sense if it was <code>[] + 2</code></blockquote>

It really wouldn't. Javascript returns <code>"2"</code> (god knows why) and Python gives an error. Don't really feel like testing many other languages, but I also think it's not really a logical assumption to make at all. Can't think of a reason for <code>[] + 2</code> to return <code>[2]</code>... ever. It ''might'' make a little bit of sense in Randall's oddly typed language, but not in any sane one. --[[User:TotempaaltJ|TotempaaltJ]] ([[User talk:TotempaaltJ|talk]]) 12:35, 12 June 2015 (UTC)

: Javascript first converts <code>[]</code> (the empty array) to the empty string (using the rule "stringify each element and join with a comma"), then treats the operation as <code>"" + 2</code>, which results in conversion of the other operand to string and then concatenation. [[Special:Contributions/141.101.97.214|141.101.97.214]] 12:46, 12 June 2015 (UTC)

line 4: asci code of N + 2 = asci code of P [[User:SirKitKat|sirKitKat]] ([[User talk:SirKitKat|talk]]) 13:07, 12 June 2015 (UTC)

My favourite xkcd in a while. =8o) Of the list I got a good laugh out of numbers 8 and 13. [[User:Jarod997|Jarod997]] ([[User talk:Jarod997|talk]]) 13:11, 12 June 2015 (UTC)

I think a lot of this is his joke about programming languages loving the number 4. 2 + "2" = "4", [1,2,3] + 4 = true, 2+2 = DONE, and the range one all seem to support this. Also reminds me of this: http://xkcd.com/221/ {{unsigned ip|173.245.52.112}}

Why isn't yellowish blue just green? [[User:Djbrasier|Djbrasier]] ([[User talk:Djbrasier|talk]]) 16:18, 12 June 2015 (UTC)
:Because yellow and blue don't make green. [[Special:Contributions/108.162.237.158|108.162.237.158]] 23:33, 12 June 2015 (UTC)
::It does with my paint kit. Isn't that subtractive mixing. I feel like I've just traveled to a version of [[1268: Alternate Universe]], except I'm the only one here who went to kindergarten. What am I missing? [[User:Djbrasier|Djbrasier]] ([[User talk:Djbrasier|talk]]) 02:28, 13 June 2015 (UTC)
:::Since this is a Programming language, it must be talking about RGB colors, where green is a base color and yellow is mixed using red and green. So a "yellowish blue" would contain all base colors, resulting in white – and that's propably why Randall's language returns NaN.[[Special:Contributions/141.101.92.42|141.101.92.42]] 08:39, 13 June 2015 (UTC)
::The only {{w|color wheel}} I know has purple (not blue) opposite yellow and orange (not yellow) opposite blue. If that is incorrect, then wikipedia needs some serious editing. [[User:Djbrasier|Djbrasier]] ([[User talk:Djbrasier|talk]]) 02:31, 13 June 2015 (UTC)

line 4: I read NaP as Not a Problem. [[Special:Contributions/141.101.104.12|141.101.104.12]] 17:00, 12 June 2015 (UTC)
: So did I. [[User:Xynariz|Xynariz]] ([[User talk:Xynariz|talk]]) 23:12, 12 June 2015 (UTC)

Line 3 is missing its prompt. There does not appear to be any relevance to the joke, nor has anyone yet explained why it should be missing. Typo? [[Special:Contributions/108.162.221.183|108.162.221.183]] 17:10, 12 June 2015 (UTC)

:I haven't noticed it until I saw your comment. It seems deliberate to me. Hard not to notice that when writing the fourth line. [[Special:Contributions/108.162.221.48|108.162.221.48]] 19:24, 13 June 2015 (UTC)BK201

Note that some programming languages avoid the problem of overloaded '+' operator between operands of vividly different types by using other symbols for string concatenation (be it "a"~"b" or "a"."b") and numerical addition. The real WTF is abusing '+' for string concatenation, which has very different properties from numerical addition, not being symmetrical for example: concat("aa", "bb") == "aabb", while concat("bb", "aa") == "bbaa" != "aabb". --[[User:JakubNarebski|JakubNarebski]] ([[User talk:JakubNarebski|talk]]) 17:38, 12 June 2015 (UTC)

Series of comics? I don't recall any others about Randall's new programming language... [[Special:Contributions/141.101.98.29|141.101.98.29]] 19:13, 12 June 2015 (UTC)

;+2
I think this is a japanese language joke. The + sign can also refer to the kanji 十, which is 10 in japanese. This would explain the result being twelve. 十二, or 10 2, is twelve in japanese. {{unsigned|Rafaeladson}}

I think number 5 is an escaped quote (two consecutive double quotes yields one double quote), a plus sign, and another escaped quote. The result is shown with an alternate form of escaped quotes (the apostrophe and double quote can both be used to show a string). NSIS scripting language uses this notation.[[Special:Contributions/108.162.221.180|108.162.221.180]] 20:19, 12 June 2015 (UTC)

Clearly this is what the xkcd phone's OS is written in (with some help from StackOverflow) {{unsigned ip|162.158.68.113}}

Great job at explaining the outputs. I clearly would have missed some interpretations without your insights. [[Special:Contributions/108.162.254.146|108.162.254.146]] 21:10, 12 June 2015 (UTC)

The joke on line [10] really doesn't seem to be a Chinese/Japanese language joke. We can see that the language interacts much more directly with line numbers from the inter-line joke between lines [11] and [14], where line [12] becomes [14] because the value of 2 has become 4. This is provable by observing that the line after [14] is [13], showing that the previous line really is still line [12], it simply displays as [14] because the value of 2 has changed. This absurdly direct interaction between the code and its line number makes the joke on line [10] make a lot more sense, as a Chinese/Japanese language joke here seems much too contrived and out-of-place considering the nature of the other jokes in the comic. Not to mention, if the joke on line [10] was really concerning the code's interaction with its line number, it would set up nicely for introducing the inter-line joke between lines [11] and [14].[[Special:Contributions/188.114.106.89|188.114.106.89]] 03:35, 13 June 2015 (UTC)

As a speaker of Japanese, the explanation "[In the Japanese number system] the plus sign is instead the symbol 十" sounds even more absurd than if someone said that English speakers use the small letter "t" as an addition symbol. "十" (ten) and "＋" (full-width plus) are different glyphs and using them interchangeably would certainly not be useful. Although depending on language skill and display font they may visually seem more equal than they're supposed to. 08:28, 13 June 2015 (UTC)

* #5—I'm surprised we've missed the obvious joke: quotations within quotations. the double-quatation "I think so." gets single-quoted within another quotation: "He said, 'I think so.'"
* The word is "complements", not "opposites", on the colour wheel. I think the joke is likely that most people think of "yellowish blue" as "green"—as it would be on an artists' colour wheel. Regardless, complements on an RGB colour wheel should not result in NaN—it would result in a mix of yellow (255, 255, 0) and blue (0, 0, 255), which is white (255, 255, 255).
* [[Special:Contributions/108.162.226.174|108.162.226.174]] 12:23, 13 June 2015 (UTC)

Is it bad that all I understood at first was the last one?

Talk:1347: t Distribution

2014-03-26T15:47:52Z

108.162.221.48: WolfWings - Out at a hotel on a business trip, sorry for no login!

http://en.m.wikipedia.org/wiki/Student%27s_t-test

[[Special:Contributions/173.245.50.73|173.245.50.73]] 05:20, 26 March 2014 (UTC)Adam

I think this is a comment of the quality of education today - it is difficult to grade students on a distribution curve and even more so when you take into account the distribution curve of the teachers ability. {{unsigned ip|108.162.249.205}}

I noticed the teacher's curve is symmetrical, and after further inspection it could be interpreted as an edge detection: high values show where an edge occurs. The two highest peaks would nicely align with the edges of the paper, the next highest peaks fit the edges of the table, and the rest could be approximation artefacts, as they're equidistant and rather insignificant compared to those four. I'm not statistics pro, but maybe that rings someone's bells? [[Special:Contributions/108.162.210.239|108.162.210.239]] 07:56, 26 March 2014 (UTC)

:Interesting observation. It may play into an age-long legend told and re-told among the students that some teachers grade papers by tossing the whole pile in the air; those sheets that land on the teacher's desk get a pass, those falling to the floor get a fail. Sometimes the story gets modified in such a way that papers falling on the teacher's book (or other object) laying on the desk will get a higher marking than those simply hitting the desk. The latter version would explain the higher sheet-size-apart peaks. [[Special:Contributions/108.162.210.111|108.162.210.111]] 08:57, 26 March 2014 (UTC)

To be more explicit, I think the sheet of paper represents some data. Cueball is not happy with the results of applying Student's t test, so ze is trying more complex tools in the hope of getting significance. -- TimMc / [[Special:Contributions/173.245.52.27|173.245.52.27]] 11:51, 26 March 2014 (UTC)

:I would upvote this comment if allowed. As an aside, there are some teachers who think a class' grades will always fall into a nice t Distribution (thus the expression "grading on a curve") and others who vehemently hate the notion. Source: my 3-year stint as a math teacher in an urban high school. [[User:Smperron|Smperron]] ([[User talk:Smperron|talk]]) 14:06, 26 March 2014 (UTC)

Man, normally these explanations clear the comic right up for me, but I've read this one thrice now and I still can't figure out what a t-distribution is, much less a joke based on one. The only definition being a Wikipedia quote written in legalese doesn't help. So a t-distribution estimates...the probability of a population's average when there's unknown information?[[Special:Contributions/108.162.216.48|108.162.216.48]] 12:17, 26 March 2014 (UTC)
:The unknown information is the sample size (class size, for example) and standard distribution (by how much, on average, is something going to vary from the mean). The unknown information is not "in the data".[[User:Jarod997|Jarod997]] ([[User talk:Jarod997|talk]]) 12:28, 26 March 2014 (UTC)
:Basically, if you have an underlying process that would produce samples with a Gaussian distribution with mean of 0, and stddev of 1, and then you pull a finite number of samples out of it, and do the usual "average" operation on those samples (i.e. sum them and divide by the number of samples) you would expect that that computed average would be close to zero. But it might not be! By chance the samples you pulled might mostly have been from the far right or left side of distribution and the average you got would be way off. Student's T distribution (for a certain number of samples, n) is basically "given that the underlying process a Gaussian with mean zero and stddev of 1, if I repeatedly take n samples from that distribution and compute the average of those samples to get an "estimated mean", this is how I expect that estimated mean to be distributed". Naturally, this is important in questions like "I took 100 samples and got an average of 0.02 -- does this mean that it is sensible to think that the mean of the underlying distribution is actually zero?"
: Of course, most of the joke is that the distribution is named "Student's", which is not strongly dependent on the nature of the statistics. [[User:Vyzen|Vyzen]] ([[User talk:Vyzen|talk]]) 12:42, 26 March 2014 (UTC)
::Okay, it's pretty clear to me now what the Student's t distribution is. I'm still not sure about the punchline though, how does the "Teacher's" t distribution come into play? Does the uneven distribution represent any phenomena in the academic world? Like, as suggested above, is this a joke about grading? [[Special:Contributions/173.245.53.137|173.245.53.137]] 15:05, 26 March 2014 (UTC)
The teacher's t-distribution looks like multiple spikier curves with different centres added together
and it doesn't fit the table. [[User:Wwt|Wwt]] ([[User talk:Wwt|talk]]) 13:17, 26 March 2014 (UTC)

I took from it that the Students Distribution was too perfect, and real data would rarely yield those idealized results in a small sample size. That the teacher's distribution used actual numbers, with the occasional spikes. I took from the title text, the tendency of students, or anyone with pre-conceived notions, to keep redoing the test until they get the results they expect, in this case, the textbook result. [[Special:Contributions/173.245.55.71|173.245.55.71]] 13:25, 26 March 2014 (UTC)

Any thoughts on the piece of paper he's trying to pull out from beneath the Students' T-distribution? [[Special:Contributions/108.162.219.66|108.162.219.66]] 14:10, 26 March 2014 (UTC)

:I don't think he he trying to pull the paper from out beneath the t-distribution. I think he is placing the distribution on top of the paper to see if the data on the paper matches the distribution. In panel 2, he looks at the paper and decides that, no, it doesn't, so then opts to use another distribution - the Teacher's t-distribution and see if that works. The comic may be hinting that the t-distribution in grading, etc (since students and teachers are explicitly listed) is flawed. --[[User:Dangerkeith3000|Dangerkeith3000]] ([[User talk:Dangerkeith3000|talk]]) 15:10, 26 March 2014 (UTC)

I may be over-simplifying it, but the 'Teachers' T looks like a reference to the 'double-hump programmer' idea, converted into a T-distribution. The other ideas cover the general principle, but this looks like a specific example as well. [[Special:Contributions/108.162.221.48|108.162.221.48]] 15:47, 26 March 2014 (UTC)