explain xkcd - User contributions [en]

Talk:85: Paths

2015-06-05T01:46:14Z

108.162.237.179:

This is the kind of thing that comes up in story problems in Calculus often. If you can travel in/over one medium at one speed, and in/over another medium at a different speed, what is the optimum path to minimize your travel time.<br>
An example of this problem would be if there is a drowning swimmer 100 meters offshore, you are 300 meters from the point on the shoreline closest to the swimmer, and you can run at 15mph and swim at 2mph, how far do you run along the shoreline before going into the water to get to the swimmer as quickly as possible?<br>
The fact that Randall shows two different paths over the "grass" makes me think that he was thinking more along the line of obsessively optimizing his path rather than about whether it might be acceptable or not to walk over the grass. -- mwburden [[Special:Contributions/70.91.188.49|70.91.188.49]] 21:23, 13 December 2012 (UTC)

Along similar lines, [http://abcnews.go.com/Technology/story?id=97628&page=1 this mathematician's dog] uses Calculus (albeit at an intuitive, rather than mathematical level) to optimize the path that it takes to retrieve the ball from the water. -- mwburden [[Special:Contributions/70.91.188.49|70.91.188.49]] 21:27, 13 December 2012 (UTC)

This particular situation is less interesting, since the walker's speed is the same for all three paths! This is seen by the times being directly proportional to the distances. Normally, the off-normal-path is at a lower speed, but some shorter path still gives the smallest time.DrMath 08:22, 14 October 2013 (UTC)

Where do the equations come from to figure out #2 & #3 - can anybody derive it? {{unsigned ip|108.162.219.185}}
:The equation #2 comes from the second route. t(1+√2)/3 is how far the second path takes the guy. If each block is a unit square, the diagonal to the corner is √2 while the next part is 1. The t/3 part is making it comparable to the first one (the first one is t despite it being 3 unit squares). Equation #3 is t√(5)/3. Plugging 1, 2, and √5 into wolfram|alpha for triangle side lengths makes it a right triange, so the √5 comes from the side length (assuming unit squares) while the t/3 makes it comparable to the first one.[[User:Mulan15262|Mulan15262]] ([[User talk:Mulan15262|talk]]) 02:36, 1 December 2014 (UTC)

Interestingly enough, if the three sides are equal in time taken (20 seconds each), the time it would take for path #2 would be 20rt2 + 20, and path three would be roughly 40, which comes out to 60, 48.28, and 40 seconds by using very simple geometry.

1522: Astronomy

2015-05-08T21:57:25Z

108.162.237.179:

{{comic
| number = 1522
| date = May 8, 2015
| title = Astronomy
| image = astronomy.png
| titletext = Astrobiology is held back by the fact that we're all too nervous to try to balance on the ladder while holding an expensive microscope.
}}

==Explanation==
{{incomplete|New page}}

For many ordinary objects, one can achieve a better view in two ways: (#1) by looking at the object from a distance through a telescope, or (#2) by approaching the object and looking at it through a magnifying glass. Magnifying glasses typically have a very short resolving distance, usually on the order of a tenth of a meter, so approach #2 is effective only in the case where you can get very close to the object in question.

In the comic, the objects being viewed are celestial bodies. Megan takes approach #1, looking at them through a telescope. Beret Guy attempts approach #2, using a step-ladder to try to get close to the celestial bodies, and then looking through a magnifying glass. This approach could be successful only if the celestial bodies were within a few meters of us. In fact they are many orders of magnitude further away than that, and Beret Guy's use of the ladder would yield no appreciable improvement in his view of celestial bodies through a magnifying glass. The history of astronomy is filled with drastic underestimates of distances to celestial bodies, but none quite so comical as Beret Guy's very extreme underestimate.

Although Beret Guy's approach to astronomy seems ill-informed, previous comics such as [[1486: Vacuum]] and [[1490: Atoms]] show that his unusual understanding of science actually works. The comic could also be a reference to the fact that space-based telescopes are much smaller than ground-based telescopes: for example, the primary mirrors of the {{w|Hubble Space Telescope}} and the {{w|W. M. Keck Observatory}} are 2.4 m and 10 m respectively.

The title text assumes (for comic effect) that the only thing wrong with Beret Guy's strategy is that the ladder would be unstable, when in fact his approach would be quite obviously bound to fail for the many reasons described above.

{{w|Astrobiology}} is the study of life (or possibility thereof) elsewhere in the universe.

It might be interesting to note that a lot of developments in "terrestrial" biology were made by the use of a simple microscope (similar to a magnifying lens), so Beret Guy's approach might be an attempt to build on that.

==Transcript==

[In front of a starry black sky, Megan looks at the stars through a telescope about twice her size, touching it at the base]

[Beret Guy enters the panel holding a ladder and a magnifying glass]

[Beret Guy places the ladder next to Megan and her telescope. The ladder is stands like a triangle, is slightly larger than Megan, but smaller than the telescope]

[Beret guy climbs to the top of the ladder, and looks at the stars through a magnifying glass]

{{comic discussion}}


[[Category:Science]]
[[Category:Astronomy]]
[[Category:Biology]]
[[Category:Comics featuring Beret Guy]]
[[Category:Comics featuring Megan]]
[[Category:Comics with inverted brightness]]

Talk:1409: Query

2014-08-19T00:15:26Z

108.162.237.179:

----
I assume the Cueball sitting on the box is being accused of being Hairy. I'd say no. [[User:Markhurd|Mark Hurd]] ([[User talk:Markhurd|talk]]) 07:26, 18 August 2014 (UTC)

Is there any particular point Randall would be making where 2 females and only one male, out of 5 each, have watch porn in the last half day? [[User:Markhurd|Mark Hurd]] ([[User talk:Markhurd|talk]]) 07:26, 18 August 2014 (UTC)
:I wasn't sure about one of those 'females', because of the various visual cues.
:What do we know/can assume about the figures? From Left to Right...
:Dark-haired ponytail and mobile phone, on own: *above 30*, not high-earning, flies easily, not a recent porn viewer. (Possibly she's a professional woman, but not smashed through the glass ceiling.)
:Assumed Megan with the 'device', standing apart: less than 30yo, not high-earning, *fears flying* (hence her inspiration), not a recent porn viewer. (Could this be the archetypal Megan, or just ''a'' Megan?)
:Taller cueball, in 1-to-1 conversation: *above 30*, not high-earning, flies easily, not a recent porn viewer. (Grown up, doubtless socially comfortable.)
:Shorter, buzzcut cueball, in 1-to-1 conversation: *above 30*, *high earner*, flies easily, not a recent porn viewer. (Probably an pre-middle-aged Exec "going places", perhaps his success and choice of 'young' haircut are as a result of a mild case of Napoleon syndrome, but if people will talk to him he's probably not being a dick about his success.)
:Sitting ponytail, in conference: less than 30yo, not high-earning, flies easily, *recent viewed porn*. (From the companions and the position, probably high 20s recent graduate relaxing with a long-term social group.)
:Sitting cueball, in conference: *above 30*, not high-earning, flies easily, not a recent porn viewer. (Another graduate, early 30s, probably exercises in order to find that sitting position relaxing. Part of the same social group.)
:Sitting flowinghair, in conference: *above 30*, not high-earning, *fears flying*, *recent viewed porn*. (''Sex indeterminate'' as that hair could indicate a metrosexual male. By 30 the look is probably starting to wearing thin, but still not overly embaressing. It certainly doesn't look like (s)he has settled down in a familial relationship yet, but has quite obviously flown the parental nest and is now with friends from college/university. Or might have been met on a round-the-world backpacking holiday and discovered they were from his own home city, except for the fear of flying (unless worked passage on ships). Probably knows all the cool scenes in this city, though, so well worth socialising in the park with.)
:Perched cueball, with icecream, hanging out: less than 30yo, not high-earning, flies easily, not a recent porn viewer. (Probably a teenager, with a close-cropped haircut. Might or might not know the other two behind him, but hard to tell what he thinks except perhaps "I've got an ice-cream! Yay!" Perhaps after a busy day of not-watching-porn.)
:Leaning ponytail, with device, hanging out: less than 30yo, not high-earning, *fears flying*, not a recent porn viewer. (Teenage girl. Big on social networking. Probably not so big on face-to-face-talking.)
:Smallest cueball, with device, hanging out: less than 30yo, not high-earning, *fears flying*, *recent viewed porn*. (Teenage boy. Typical teenage boy. As girl, but probably in-between Tweeting with the girl next to him he's serrupticiously viewing a video someone sent him (see his furtive look?), and maybe of the girl next to him. Or something 'sexted' ''from'' her, if that wouldn't count for her SELECTion on that criteria. One way or another, ''probably'' with the sound off.)
:...what's more, presumably none of those fiogures were Terminator Units, Alien Shapeshifting Lizards or ''already'' ghosts of some kind (or whatever class of individual would not belong in TABLE PEOPLE). [[Special:Contributions/141.101.99.7|141.101.99.7]] 09:34, 18 August 2014 (UTC)

::Thats racism! I mean speciesm. Alien Shapeshifting Lizards are people too! -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 10:15, 18 August 2014 (UTC)

Sounds a lot like watch_dogs. [[Special:Contributions/108.162.229.201|108.162.229.201]] 07:42, 18 August 2014 (UTC)

Is this Zuckerberg's phone? [[Special:Contributions/108.162.254.34|108.162.254.34]] 09:33, 18 August 2014 (UTC)

Is there any particular reason this comic isn't appearing on the homepage at the moment? For some reason xkcd.com is displaying 1408 "March of the Penguins". No actual navigation on the site will take me to this comic, I have to manually type /1409 into the URL bar. --[[User:Zagorath|Zagorath]] ([[User talk:Zagorath|talk]]) 10:20, 18 August 2014 (UTC)

I'm under the impression that Megan is using the device to look for potential mates. The age and income queries point to this, the other two are less common but still make sense in the context of a relationship. Finding no one who matches all of her criteria, she then deletes the list.
[[User:Dromaeosaur|Dromaeosaur]] ([[User talk:Dromaeosaur|talk]]) 10:41, 18 August 2014 (UTC)
:Well, there's obviously something to the idea of those directing her choices (for positive ''or'' negative selection purposes - I assume <=30 && >$100k, but would she want someone who shares her fear and would ''never'' suggest a plane trip, or someone who could be reassuring when one ''is'' taken? And someone who is 'wholesome' or likely to be open-minded about pornography?) but, although it's likely there's no Mr(/Mrs) Right, she finds just proclaims it "neat" and only seems to inadvertently 'tidy up' (albeit too much), rather than doing it in deliberate (if again misjudged) frustration... [[Special:Contributions/141.101.99.7|141.101.99.7]] 11:39, 18 August 2014 (UTC)

Why does the explanation call it "SQL-esque"? That looks like fully valid SQL to me. --[[Special:Contributions/108.162.230.119|108.162.230.119]] 10:49, 18 August 2014 (UTC)

I think the comic is a reference to "Big Data" and the claim I read this morning that one organisation has a file on 10% of the world's population with around 1500 pieces of information on each of them. [[Special:Contributions/141.101.98.194|141.101.98.194]] 12:27, 18 August 2014 (UTC) Dan

One thing I find interesting is what I see as an implication that <del>5/10</del> (sorry: 6/10) of the people pictured would not have a "device" on them at the time they were dropped with the PEOPLE table - certainly ''more'' than half of people have a device (or at least an ID or set of keys or something)... perhaps being contained within their clothing -- which apparently is dropped along with the associated person -- means THOSE devices were dropped along with the clothing (cascading?); however, being in the hands of the associated person means a certain level of disassociation... idunno... pick pick pick away at the joke! ALSO, seems like the time since someone watched porn would have to be computed (wouldn't be stored in the table as a field itself, but computed from a field like time_last_watched_porn and datediff... or else some user-defined function)... FINALLY - would have been great to see the result of an INSERT or UPDATE statement prior to dropping... ah well - [[User:Brettpeirce|Brettpeirce]] ([[User talk:Brettpeirce|talk]]) 14:10, 18 August 2014 (UTC)

See [[327: Exploits of a Mom]]. That is all. [[Special:Contributions/173.245.54.153|173.245.54.153]] 19:04, 18 August 2014 (UTC)

I think it's interesting Megan chooses to Drop Table People right after viewing who's watched porn, much like people who clear their browser cache/history after watching porn to make sure no one else finds out. [[Special:Contributions/108.162.237.179|108.162.237.179]] 00:15, 19 August 2014 (UTC)