explain xkcd - User contributions [en]

1372: Smartwatches

2019-11-18T19:53:44Z

108.162.216.86: Spelling correction.

{{comic
| number = 1372
| date = May 23, 2014
| title = Smartwatches
| image = smartwatches.png
| titletext = This is even better than my previous smartphone casemod: an old Western Electric Model 2500 desk phone handset complete with a frayed, torn-off cord dangling from it.
}}

==Explanation==
{{w|Smartwatch|Smartwatches}} are fairly recent innovations which function something like smartphones which are attached to one's wrist, although the screens are often shorter than those of typical smartphones, and they typically need to be attached via bluetooth to a smartphone. This comic shows someone "{{w|Case modding}}" some smartwatches and a broken smartphone; that is, taking the electronic innards of two smartwatches and putting them into the sawn-in-half case of a smartphone before attaching the two halves with a hinge, allowing it to open and close like flip phones, a type that was popular before the rise of smartphones.

The {{w|Model_500_telephone#Model_2500|Western Electric Model 2500}} is the last standard desk-style domestic telephone set issued by the {{w|Bell System}} in North America. It contains the # key and the * key, so it can be said it has same application features as the first cellphones, but it's obviously much bigger, and of course not wireless. Smartphones usually have much more functionality. {{w|Case modding}} is the art of building machines (usually computers) into nicely shaped non-standard cases. The opinion about "niceness" of the result vary, as usual in art. The point is that changing the case doesn't change the functionality, so the niceness (or, usually, "coolness") is generally the only relevant feature (although, badly done modding can affect cooling).

It appears that [[Randall]] has a rather low opinion of smartwatches, as he suggests that it would be better to take out their screens and mount them onto a dead iPhone than to use them the way smartwatches are normally used.

However, Randall's suggestion to cut open the dead phone with a hacksaw is unsound for several reasons:
1. Any attempt to saw through glass will cause it to shatter. To cut glass, one needs to grind it, not saw it.
2. Even if the phone is dead, the battery may be charged. Saw blades conduct electricity, so the person might get electrocuted.
3. Some batteries contain chemicals that are toxic or explosive. Even if the battery is discharged, sawing through it is very dangerous.
To add which, the hinge depicted in the cartoon is an ordinary household hinge. It is overly large for using in electronics compared to hinges on old clamshell-style cell phones, and drilling holes in the watch cases to attach one would potentially damage the internal electronic circuits. It could also puncture the battery, causing it to catch fire. Either render the watch useless.
4. Also, it's possible the watches wouldn't fit that nicely into the iPhone.

While no phones such as the one depicted existed at the time of the comic (2014), in November 2019, Motorola officially announced a new Android phone, to be released under the Razr name, which is extremely similar in form-factor to the fictitious phone shown in this comic, albeit with a single flexible LCD screen, rather than two separate screens.

==Transcript==
:A USE FOR SMARTWATCHES:
:[Depicted are two smartwatches, both labelled as "Working" and showing generic colour displays, and one smartphone labelled as "Dead" with a blank screen.]

:[A hacksaw cutting through the smartphone, throughout the middle of the long edge of the case.]

:[The two smartwatches are shown with the wristband and case broken around the edge of the display because the displays with the associated electronics are removed. Arrows are shown coming from the smartwatch cases to the smartwatch displays, then from the displays to the smartphone case halves.]

:[The smartphone halves are installed with the smartwatch components and a hinge with screws beside is shown. Another view shows the hinge screwed into the back of the smartphone case.]

:[The smartphone with the working smartwatch components installed is shown, with the hinge three-quarters open and fully closed - resembling an early flip-phone.]
:World's first flip iPhone

{{comic discussion}}
[[Category:Comics with color]]
[[Category:Smartphones]]

1372: Smartwatches

2019-11-18T19:52:15Z

108.162.216.86: Added info about 2019 Motorola Razr announcement.

{{comic
| number = 1372
| date = May 23, 2014
| title = Smartwatches
| image = smartwatches.png
| titletext = This is even better than my previous smartphone casemod: an old Western Electric Model 2500 desk phone handset complete with a frayed, torn-off cord dangling from it.
}}

==Explanation==
{{w|Smartwatch|Smartwatches}} are fairly recent innovations which function something like smartphones which are attached to one's wrist, although the screens are often shorter than those of typical smartphones, and they typically need to be attached via bluetooth to a smartphone. This comic shows someone "{{w|Case modding}}" some smartwatches and a broken smartphone; that is, taking the electronic innards of two smartwatches and putting them into the sawn-in-half case of a smartphone before attaching the two halves with a hinge, allowing it to open and close like flip phones, a type that was popular before the rise of smartphones.

The {{w|Model_500_telephone#Model_2500|Western Electric Model 2500}} is the last standard desk-style domestic telephone set issued by the {{w|Bell System}} in North America. It contains the # key and the * key, so it can be said it has same application features as the first cellphones, but it's obviously much bigger, and of course not wireless. Smartphones usually have much more functionality. {{w|Case modding}} is the art of building machines (usually computers) into nicely shaped non-standard cases. The opinion about "niceness" of the result vary, as usual in art. The point is that changing the case doesn't change the functionality, so the niceness (or, usually, "coolness") is generally the only relevant feature (although, badly done modding can affect cooling).

It appears that [[Randall]] has a rather low opinion of smartwatches, as he suggests that it would be better to take out their screens and mount them onto a dead iPhone than to use them the way smartwatches are normally used.

However, Randall's suggestion to cut open the dead phone with a hacksaw is unsound for several reasons:
1. Any attempt to saw through glass will cause it to shatter. To cut glass, one needs to grind it, not saw it.
2. Even if the phone is dead, the battery may be charged. Saw blades conduct electricity, so the person might get electrocuted.
3. Some batteries contain chemicals that are toxic or explosive. Even if the battery is discharged, sawing through it is very dangerous.
To add which, the hinge depicted in the cartoon is an ordinary household hinge. It is overly large for using in electronics compared to hinges on old clamshell-style cell phones, and drilling holes in the watch cases to attach one would potentially damage the internal electronic circuits. It could also puncture the battery, causing it to catch fire. Either render the watch useless.
4. Also, it's possible the watches wouldn't fit that nicely into the iPhone.

While no phones such as the one depicted existed at the time of the comic, in November 2019, Motorola officially announced a new Android phone, to be released under the Razr name, which is extremely similar in form-factor to the fictitios phone shown in this comic, albeit with a single flexible LCD screen, rather than two separate screens.

==Transcript==
:A USE FOR SMARTWATCHES:
:[Depicted are two smartwatches, both labelled as "Working" and showing generic colour displays, and one smartphone labelled as "Dead" with a blank screen.]

:[A hacksaw cutting through the smartphone, throughout the middle of the long edge of the case.]

:[The two smartwatches are shown with the wristband and case broken around the edge of the display because the displays with the associated electronics are removed. Arrows are shown coming from the smartwatch cases to the smartwatch displays, then from the displays to the smartphone case halves.]

:[The smartphone halves are installed with the smartwatch components and a hinge with screws beside is shown. Another view shows the hinge screwed into the back of the smartphone case.]

:[The smartphone with the working smartwatch components installed is shown, with the hinge three-quarters open and fully closed - resembling an early flip-phone.]
:World's first flip iPhone

{{comic discussion}}
[[Category:Comics with color]]
[[Category:Smartphones]]

1685: Patch

2016-05-28T15:40:55Z

108.162.216.86: /* Transcript */ first line: changed L back to T on end of "import". In the font used, the L has a bottom line centered on the vertical, which is not seen here.

{{comic
| number = 1685
| date = May 25, 2016
| title = Patch
| image = patch.png
| titletext = My optimizer uses content-aware inpainting to fill in all the wasted whitespace in the code, repeating the process until it compiles.
}}

==Explanation==
{{w|Adobe Photoshop}} is a commonly used application for image manipulation. One of its features is the Patch tool, which allows the user to overwrite parts of the image, replacing them with a copy of another area of the same image. It is often used for “patching up” photographs by overwriting scratches or other visible damage to the photo. Another of Photoshop’s features is “content-aware fill”, which could also be described as “content-aware inpainting”. It works similarly to the Patch tool, but automatically generates a replacement texture from the area surrounding the deleted part instead of copying a user-specified area exactly.

{{w|GNU}} {{w|Patch (Unix)|patch}} is a program that replaces only parts of code with an updated version, without requiring the user to download the entire source code. Here, it appears the author was told to “patch” the code, but used Photoshop to do this instead of GNU patch, with devastating results. Although the title text suggests that if you did this enough times the code would eventually compile, this would never happen. In fact, Photoshop could only edit an image of the text and not the text itself. (However, it could work if optical character recognition (OCR) were integrated into the workflow as well.)

The comic blurs the difference between {{w|text_file|text}} (in which letters and symbols represent discrete values, such as 65 being the number for the letter A in the ASCII encoding standard, and it's relatively easy for a program compiler to interpret combinations of these values as keywords and other programming constructs) and {{w|Raster_graphics|graphics}} (where the letters and symbols in the comic are actually represented by pattern of colored dots), playing with the idea that the ''patch'' metaphor can be used on both (although with different meanings). There are common and straightforward processes for converting text information to images, such as printing, which can convert text to a graphics format very faithfully. The reverse, however, requires the use of {{w|optical character recognition}} (OCR), which attempts to figure out which letter or symbol certain patterns of dots "look like". OCR could be effective in converting some of the image in the comic back to usable text, however it would fail on some of those patterns that have been mangled and don't look like any existing characters or symbols. A compiler can only operate on text data, so converting the graphic back into text would be a requirement to even begin to attempt to compile it, a step omitted in the title text.

The code appears to be written in {{w|Python_(programming_language)|Python}}, a programming language often referred to in xkcd. A few of the function names that can be recognized are "isPrime" and "quicksort", both elementary programming algorithms. It was also apparently originally edited using a Python-aware programming text editor, which is able to use different colors for different programming elements. For example, it appears to use red for keywords, blue for variables, and black for other elements, however because of the mangling from the use of the wrong patching program, that doesn't appear to be consistent. Since the patching replaced graphical elements rather than whole characters, there are examples of symbols that are combination of two different characters, and when the original two characters were rendered in different colors the resulting non-character could be in two colors, or the resulting "word" might be rendered in multiple colors.

The comic brings to attention the high rate of Adobe Photoshop piracy. GNU Patch is available for free, even [http://gnuwin32.sourceforge.net/packages/patch.htm for Windows], and Mac OS X. So the comic implies that Adobe Photoshop, subscription to which costs $20/month, is more available than GNU patch. According to [http://blog.epicedits.com/2008/03/28/60-of-photoshop-users-are-pirates/ this poll], 58% of Photoshop copies were pirated.

The title text also explains that patch used the content-aware inpainting to fill in all the wasted whitespace in the code. In most programming languages, whitespace is necessary to separate words, so this would combine words that shouldn’t be combined and create invalid code. Since the code in the image is Python, the code will be messed up even more, because Python uses whitespace as a part of its programming syntax. For example, statements are separated by new lines instead of by semicolons (;), and indentation is used instead of brackets to determine the scope of each section of code.

The original code was likely as follows:

import re
def isPrime(n):
if n<=1:
return False
for i in range(2, int(n**0.5)+1):
if n%i==0:
return False
return True
def isPrimeRegex(n):
if re.match(r'^1?$|^(11+?)\1+$', '1'*n):
return False
return True
def quicksort(a):
if len(a) < 2:
return a
pivot=a[0]
l=[i for i in a if i<pivot]
r=[i for i in a if i>pivot]
mid=[pivot]*(len(a)-(len(l)+len(r)))
return quicksort(l)+mid+quicksort(r)

isPrime and quicksort are standard python implementations of simple algorithms (although you would not generally write a sorting algorithm in python as there are built-in algorithms available). isPrimeRegex uses the [https://docs.python.org/library/re.html re module] to detect if a number is prime by seeing if a string containing that many 1s can be matched to 2 or more copies of some string containing at least 2 1s.

The comic two comics back [[1683: Digital Data]], also related to turning digital data into bad copies. Less than a month before quicksort was mentioned in [[1667: Algorithms]], and a month before that another "easy" solution to a programming problem was released in [[1654: Universal Install Script]].

==Transcript==
:[The panel displays part of a code, in five different colors (red, purple, light blue, blue and green) as well as normal black text, which due to image editing is difficult to read. The first and last line are partly obscured by the frame of the panel. Here below is an attempt to transcribe the code, using the sign "¤" for anything not easily transcribed. Feel free to add other signs instead of these that looks more like the one in the image (and also improve the attempted transcription if possible).]
impo¤t me
dooPisPŞ¤me(n):
r(¤n<n,1:
retern F(ise
for i irararre(2, nint *n**n+5)+5):
if n i==0
ret¤¤nrselsel:
re¤ irn True
defesisPrimcieg ¤x(cx
if ge¤inatcx(ᵣ'^(1?| ?.1+?)\+)$'*n )1'*n):
rerjrn Fa( e
LetylnrTrl
dql qlsorsorn(a :
if ¤n(a < 2:
eteturn a
pi= =r fa[0]
l=pi=for j ln a i< i<pi<(t]()
r=[l=for f in a) r i>viviv](vo)
mid=[pi[*t]*(l*t,(a)-(lenpienlen(c)))
r¤lrurrriklcksckt(l) + r ¤ ¤quickrort(r)

:[Caption below the panel:]
:Protip: If you don't have access to the GNU ''patch'' tool, you can use the Photoshop one.

{{comic discussion}}

[[Category:Comics with color]]
[[Category:Protip]]
[[Category:Programming]]

1475: Technically

2015-01-19T17:45:30Z

108.162.216.86: /* Explanation */

{{comic
| number = 1475
| date = January 19, 2015
| title = Technically
| image = technically.png
| titletext = "Technically that sentence started with 'well', so--" "Ooh, a rock with a fossil in it!"
}}

==Explanation==
{{incomplete|First Draft}}

When the word "technically" is used to start a sentence, the remainder of the sentence tends to follow one of a number of patterns:

{| class="wikitable"
! Sentence pattern
! Example
|-
| An explanation which is far more complex than the listener needs/wants.
| "Technically an inch is 25.4 mm, but historically..."
|-
| A justification of a particular (usually unpopular) viewpoint through an unusual technical definition.
| "Technically a tomato is a fruit, so there is no reason it shouldn't be used in a fruit salad."
|-
| A pedantic overapplication of rules or laws, often to avoid the spirit of the law through a technical loophole.
| [http://factually.gizmodo.com/technically-american-flag-napkins-are-illegal-1599774198 "Technically, American flag napkins are illegal."]
|-
| The speaker repeating a 'little known fact', believing that he/she sounds incredibly knowledgeable.
In many cases these 'facts' are actually false, as in the example to the right (see {{w|Ten_percent_of_brain_myth|the 10% of the brain myth}}).
| "Technically we only use 10% of our brains, so imagine what we could do if we used 100%"!
|}

[[Cueball]] has decided that any sentence beginning with the word "technically" is highly likely to be completely worthless for him to listen to, so he allows himself to be distracted by anything which happens to be around.

The particular sentence uttered by White Hat is of the fourth type, due to his incorrect interpretation of the word "drug" and lack of understanding of the role of food in human physiology. Indeed, the word drug is defined as "a substance used to treat an illness, relieve a symptom, or modify a chemical process in the body for a specific purpose", followed by a secondary definition of "a psychoactive substance, especially one which is illegal and addictive". Food, on the other hand, is defined as "any substance that can be consumed by living organisms, especially by eating, in order to sustain life". In other words, food is consumed in order to sustain the normal, innate state of the body, while the drug is consumed in order to alter certain states.

The title text starts to pedantically over apply Cueball's rule to the comic panel, noting that technically [[White Hat]]'s sentence started with the word 'well' instead of the word 'technically', and thus Cueball is wrong to have ignored it. This makes the title text a sentence of the third type. Halfway through the sentence, this argument is cut off by the discovery of a rock with a fossil in it, correctly applying the rule to a sentence that began with the word "technically".

==Transcript==
:[White Hat talks to Cueball who looks at a flying insect]
:White Hat: Well, technically, food is a "drug", since it's a substance that alters how your body works, so yes, I'm —
:Cueball: Hey, look at that weird bug!

:[Caption below the frame:]
:My life improved when I realized I could just ignore any sentence that started with "technically."

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring White Hat]]

899: Number Line

2014-09-02T21:12:12Z

108.162.216.86: /* Explanation */ A parenthetical "for non-US residents" comes across as overly patronizing and adds nothing to the explanation. ~~~~

{{comic
| number = 899
| date = May 16, 2011
| title = Number Line
| image = number line.png
| titletext = The Wikipedia page List of Numbers opens with "This list is incomplete; you can help by expanding it."
}}

== Explanation ==

Once again, Randall seems to be just messing around, this time with a number line.

*'''Negative numbers''' have the same magnitude as positive numbers but can only be used to represent the removal of that same magnitude (hence the term "difference" being used for subtraction).

*'''0.99'''.... is {{w|0.999...|equal to 1}} because there is no number between 0.99.... and 1. 1 - '''0.0000000372''' is 1 bit less than the IEEE 754 32-bit floating-point representation of 1.

*The '''{{w|golden ratio}}''' or "phi" is the number (1 + sqrt(5)) / 2, about 1.61803. It has many interesting mathematical properties, mostly relating to geometry, and has occasional appearances in nature, such as spirals formed by the seeds in sunflowers. It is also subject to many less credible claims, such as the belief that phi appears in {{w|Parthenon}} (a well-disputed claim) or that rectangles proportioned after phi are more aesthetically pleasing.

* The approximate range from 2.1 to 2.3 is marked as '''The Forbidden Region'''. Why Randall marked this range as forbidden is really anyone's guess; it seems to be an entirely arbitrary designation.

*'''{{w|e (mathematical constant)|e}}''' (Euler's number) is 2.71828... and '''π''' (pi) is 3.14159265...

*'''2.9299372''' is a President's Day reference. It is the average of e and pi just as the American Presidents' Day is always observed on the 3rd Monday of February (between {{w|George Washington}} and {{w|Abraham Lincoln}}'s birthdays). Washington and Lincoln were the 1st and 16th Presidents of the USA, respectively. Each has a celebrated place in American history.

*'''{{w|Gird}}''' is a purely fictional number. (The glyph that Randall uses seems to resemble an older shape of the digit 4, such as seen on [http://www.bl.uk/learning/images/mappinghist/large2296.html archaic maps].). Canon and orthodox are references to organised religions. Gird could be a reference to any or all of:
**[http://www.strangehorizons.com/2000/20001120/secret_number.shtml Bleem] - a fictional integer between 3 and 4
**iCarly's [http://icarly.wikia.com/wiki/Derf Derf] - a fictional integer between 5 and 6
**George Carlin's [http://www.urbandictionary.com/define.php?term=bleen Bleen] - a fictional integer between 6 and 7
**[http://www.scp-wiki.net/scp-033 SCP-033] - a fictional number that causes freaky things to happen

*'''Site of the Battle of 4.108''' is another map joke, implying that 4.108 is an actual location, where an eponymous battle was previously fought. It may be a reference (or homage) to the {{w|Battle of Wolf 359}}, a famous military conflict in the fictional universe of Star Trek.

*An '''Unexplored''' region obscures the line approximately ranging all values from from 4.5 to 6.7. In the days when the Earth was still being mapped out, territories that had yet to be properly explored and charted were labelled in a similar manner. The placement of the '''Unexplored''' region on the number line indicates that all numbers in that range, including the integers 5 and 6, are completely unknown. This is, of course, patently ridiculous, and the humor seems to derive solely from how nonsensical and unbelievable it is.

*It is often the case in the media that "It has been 7 years..." or "In the last 7 years..." etc. It is made to seem like a believable statistic but cannot always be true. Alternatively, it is intended as an absurd joke that the number 7 is just "not to be believed".

*'''8''' is not the largest even prime, nor is it a prime at all. The largest even prime is 2. A joke intended for those who clearly know that the claim is false.

*The last entry seems to be a reference to {{w|discrete mathematics}}, which rarely deals with numbers higher than 9. It finishes off the tone of the comic that seems to be shaping the number line terms of what is commonly useful to certain areas of applied mathematics, rather than a complete, accurate version of the number line.

The title text is a literalism joke implying that Wikipedia would like its "{{w|List of numbers}}" page to include every number from negative infinity to infinity. It could also be a reference to {{w|Gödel's incompleteness theorems}}, which [[Randall]] has used as comic fodder before [[468: Fetishes]]. Gödel's theorems roughly assert that a number theory could never be fully complete. The equivalent for just a sheer list of numbers is {{w|Cantor's diagonal argument}}, which is a "proof of the uncountability of the real numbers." Therefore, if Wikipedia ever did have a "List of numbers", it would perforce forever be incomplete, no matter how much it was expanded. Both Gödel's incompleteness theorems and Cantor's diagonal argument feature prominently in {{w|Gödel, Escher, Bach}} by {{w|Douglas Hofstadter}}, to whom Randall devoted later comic [[917: Hofstadter]].

== Transcript ==
:[Number line ranging from -1 to 10.]
:[Arrow pointing left, towards negative numbers] Negative "imitator" numbers (do not use)
:[Line right before the number one] 0.99... (actually 0.0000000372 less than 1)
:[Line at the golden ratio.] Φ - Parthenon; sunflowers; golden ratio; wait, come back, I have facts!
:[Line at a region between two and 2.2] forbidden region
:[Line at Euler's number.] e
:[Line a bit before 3] 2.9299372 (e and pi, observed)
:[Line at π.] π
:[Line at 3.5 with a ribbon as the numeral] Gird - accepted as canon by orthodox mathematicians
:[Line a bit after 4.] site of battle of 4.108
:[Blob between 4.5 and 6.5 labeled unexplored.]
:[Line at seven.] Number indicating a factoid is made up ("every 7 years...", "science says there are 7...", etc)
:[Line at eight.] Largest even prime
:[Line at 8.75.] If you encounter a number higher than this, you"re not doing real math

{{comic discussion}}
[[Category:Math]]
[[Category:Wikipedia]]

Talk:681: Gravity Wells

2014-08-21T00:19:29Z

108.162.216.86:

Why is Earth's well's depth listed as 5478km but as 6379km in the inset?
Compare with Mars which has 1286 in both places.
[[Special:Contributions/87.174.225.131|87.174.225.131]] 07:21, 12 April 2013 (UTC)
:Best guess is either a goof, or that the lower number is just for Earth itself, while the greater number is for the Earth/Moon system as a whole. Proportionally speaking, we have the largest moon in the solar system, so maybe it wouldn't nicely fit in the Earth well as easily as Mars's and Jupiter's moons do.--[[User:Druid816|Druid816]] ([[User talk:Druid816|talk]]) 08:28, 12 April 2013 (UTC)

: It ''may'' be the height needed to go from one gravity well to another. You don't have to get all the way up to escape speed for that.

: Randall wasn't kidding about the Sun being "very very far down"; its well is 100 times deeper than Jupiter's!
:[[User:Wwoods|Wwoods]] ([[User talk:Wwoods|talk]]) 19:47, 12 April 2013 (UTC)

:: OTOH, from the table above i'm thinking that the 5.4 might be the Venus figure, and it was wrongly placed besides Earth...
:: Secondly, what i found interesting was that the Earth's 6.4 looks so much like its radius! I wonder if it's merely a coincidence, or there's a connection between the two... -- [[Special:Contributions/141.101.99.233|141.101.99.233]] 21:25, 30 October 2013 (UTC)
:::The table is great, it must be included in the article; layout and time is just my problem right now. PRO TIP: Do not care about the x-axis.--[[User:Dgbrt|Dgbrt]] ([[User talk:Dgbrt|talk]]) 22:18, 30 October 2013 (UTC)
: The fact that the density of the Earth is 5478 kilograms per cubic kilometer makes me pretty sure it is a typo. [[User:Fewmet|Fewmet]] ([[User talk:Fewmet|talk]]) 03:04, 4 July 2014 (UTC)
:: Hehe, you might be right. That's the best explanation. It would be a strange coincidence otherwise. But your units are wrong: a cubic kilometer of water, ice-cream or Natalie Portmans would be already something like a billion kilograms. Or a trillion, if you are American. Oh, you might be American. In this case: happy 4th of July! -[[Special:Contributions/188.114.102.35|188.114.102.35]] 12:39, 4 July 2014 (UTC)
:::Thanks for catching that (and for the July 4 wishes). It should be kilograms per cubic meter. Looking into that, though, leaves me less sure that is the origin of the problem. I thought I had multiple sources for Earth having a density of 5478 kg/m3, but can find only [//atharvatutorials.com/doc/physics_paper.docx one] (and not a very compelling one at that). I have sounder sources for [//www.universetoday.com/26771/density-of-the-earth/ 5513 kg/m3]. [//nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html 5514 kg/m3], [//www.wolframalpha.com 5515 kg/m3], [//www.esa.int/Our_Activities/Space_Science/Venus_Express/Venus_compared_to_Earth 5520 kg/m3] and [//principles.ou.edu/earth_planet/ 5540 kg/m3]. It may be trivial in that all round to 5500 kg/m3.
::It was corrected on the poster version. Earth's well in the main graphic is marked as 6379km, just like the inset.[[Special:Contributions/108.162.216.86|108.162.216.86]] 00:19, 21 August 2014 (UTC)

:::I solved for the wells on Earth, Moon and Mars using the equation Randall gave and masses and equatorial radii from NASA, getting 6371 km, 287 km and 1286 km, respectively. [[User:Fewmet|Fewmet]] ([[User talk:Fewmet|talk]]) 23:07, 5 July 2014 (UTC)
The Oberth Effect mentioned in the title text is [//www.askamathematician.com/2013/01/q-how-does-the-oberth-effect-work-and-where-does-the-extra-energy-come-from-why-is-it-better-for-a-rocket-to-fire-at-the-lowest-point-in-its-orbit/ well-explained here] (assuming you are not intimidated by the algebra in squaring a binomial). The gist of it is that using a bit of fuel in a rocket thrust will increase the rocket’s kinetic energy . The higher the kinetic energy at the time of the thrust, the greater the increase in kinetic energy. It works because the energy of the fuel goes into increasing the kinetic energy of the ship and the kinetic energy of the spent fuel. The faster you go, the greater the portion of the energy the ship gets.

The “gravity assist” is also known as the slingshot effect. The [//en.wikipedia.org/wiki/Gravity_assist#Explanation Wikipedia explanation] is good, especially with its diagram. In it a spaceship (or other body) accelerates toward a planet (or moon, star, etc.) in the same direction that body was going. The ship picks up a little of the body’s momentum and so goes faster, although only according to an external reference frame. An observer at rest with respect to that other body would actually see the ship approach and depart with the same speed.

The title text reference to orbital speed is unclear to me. I suppose it just means that the given gravity wells assume you are at rest on the surface of the planet. Then being in orbit (and necessarily having an orbital speed) would mean you are part way out of the well already. [[User:Fewmet|Fewmet]] ([[User talk:Fewmet|talk]]) 02:57, 4 July 2014 (UTC)

Talk:1397: Luke

2014-07-27T13:06:26Z

108.162.216.86:

Vader: *turns fleshlight on* An invisible blade? That is quite interesting. I should build one of these myself. (Alternately, ''I find your lack of blade disturbing'')[[Special:Contributions/103.22.201.239|103.22.201.239]] 05:55, 21 July 2014 (UTC)
:I was assuming that if you go ahead and turn on the fleshlight, you would get a column of a sticky white plasma shooting out insteaed [[Special:Contributions/199.27.133.205|199.27.133.205]] 18:51, 21 July 2014 (UTC)

What are these "connection to previous comic" things? They seem random and arbitrary. [[Special:Contributions/199.27.133.205|199.27.133.205]] 06:15, 21 July 2014 (UTC)
:There usually seems to be a point of contact with the previous comic. That a connection is usually there means it probably isn't coincidental but is part of the ingredients for making each new comic. So yes they do seem random and arbitrary because the content of the connection doesn't mean anything. The point is just that every comic is connected to the previous comic. The explanations of the connections may be incorrect. I thought I'd put these connection sections in to see how people feel about having a regular connection section. [[User:Rfvtg|Rfvtg]] ([[User talk:Rfvtg|talk]]) 06:33, 21 July 2014 (UTC)
::It may be a good idea, but I see no connection, just a lame pun. There usually dorsn't seem to be much of a connection anyways.[[Special:Contributions/173.245.48.130|173.245.48.130]] 07:14, 21 July 2014 (UTC)
::I don't think there's a real connection. I think that you're finding arbitrary segues, because you can segue between just about any two topics if you try. Try this - pick two random xkcd, and see if you can't find a "connection". [[Special:Contributions/108.162.249.209|108.162.249.209]] 11:57, 21 July 2014 (UTC)
:::I agree. This is the most stupid idea I have seen here on explain. Please remove them again. Thay make no sence and spoils the nice look of this great page. [[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 13:37, 21 July 2014 (UTC)

Anyone want to mention that this is probably referencing is a weird quirk of the films? We never see Luke construct a lightsaber (unless I missed something), and it's easy to assume that it's actually... I think Ben Kenobi's or Yoda's, maybe (for prequel enthusiasts) even Qui Gon's... After all, if Obi kept Anakin's, maybe he'd also keep Qui-Gon's, and any others, and end up leaving at least one green sabre on the Falcoln. Anyway, my point is, Randall noticed that this line of dialogue isn't really explained, and Luke is probably going along with Darth's assumption to save face... And then took the awkward situation to new heights. I can't tell if I'm being a total idiot here or if I'm on to something. Or option three, it's something glaringly obvious but needs a mention to explain the comic in context [[Special:Contributions/141.101.99.234|141.101.99.234]] 10:29, 21 July 2014 (UTC)
:Vader would probably recognize his mentors' lightsabers at first glance. Yes, it could be another unknown dead Jedi's saber, but it just as likely that Luke constructed one of his own, given he does not react in an obvious way to the suggestion. (Ignoring the Star Wars EU, which probably details exactly how Luke constructed the device.) Besides, we are shown Kenobi's, Yoda's and QG's lightsabers in the movies.[[Special:Contributions/103.22.201.239|103.22.201.239]] 11:39, 21 July 2014 (UTC)
:There exists a deleted scene from Star Wars VI that shows Luke building his new lightsaber: [https://www.youtube.com/watch?v=_ayT0EZwbks] [[Special:Contributions/108.162.254.53|108.162.254.53]] 13:45, 21 July 2014 (UTC)
:: Why would we need to see him build it? He lost his in the previous film. And he now has a snazzy new green one, along with much improved skill. The obvious conclusion is he built it. Vader then sees it and confirms that this is a mark Luke has gotten stronger. There is no reason to doubt that he built it. And before the prequels and such, we wouldn't have imagined there were thousands lying around. Now everyone and anyone has a light saber even up to Luke's time. When the movie came out, it was never clear how many Jedi there ever were. But it seemed to have been a very small number. [[Special:Contributions/108.162.215.212|108.162.215.212]] 23:49, 21 July 2014 (UTC)
:: I may be (mis)remembering something from the D6-based Star Wars tabletop RPG system (1980s, prior to this current D20 malarky), or something else "canon-derived-but-not-actually-canon" but ''personally'' creating one's own lightsabre is supposed to be something special. Obtaining/refining the crystals/whatever and tuning the device to work better with one's own Force Ability makes for a more harmonious relationship between Jedi/Apprentice Jedi and his or her weapon. Luke starts off 'raw' in the force (only with the innate and untrained ability) and with another individual's device (albeit his father's, which may count for something, the way these things work) but then like the various mythological instances of warrior-cum-blacksmiths (or blacksmith-cum-warriors) forging their own blade, something (even if only the Law of Narrativium) makes this self-made artefact singularly suitable for the fighting style of the creator/wielder. Or allows them to tune their still developing fighting style to the 'personality' of the weapon, if it is a two-way street.
:: Naturally, how far any of this can be extended towards the ''Fleshlight'' is very much arguable. Although if ''it'' is personally designed and built, to suit their own 'needs' then it's probably much better at the function it is intended to fulfil than an off-the-shelf or a (*shudder*) borrowed or ''hand-me-down'' one... [[Special:Contributions/141.101.99.233|141.101.99.233]] 00:08, 22 July 2014 (UTC)
:Boy, we're plumbing the depths of Star Wars geekdom here, aren't we? :) I think one other thing you folks are overlooking is that Vader is ''smart'' and ''powerful''. He can see and deduce things that most other people can't, mostly due to his powerful connection to the Force. In the movie, I believe that when he says "I see you've constructed a new light saber", he's not only remarking on its visible newness, but he properly senses Luke's memory of having done so. This fits, given a number of other lines later in the movie where Vader remarks on Luke's feelings, especially in "betraying" Leia as his sister. So even more than when he sees the saber itself, Vader probably knew well ahead of time that Luke had built one, part of his "rite of passage" to become a Jedi. (Personally, all of this makes the fleshlight joke that much funnier, IMO. :)) [[User:KieferSkunk|KieferSkunk]] ([[User talk:KieferSkunk|talk]]) 16:02, 22 July 2014 (UTC)
This comic reminds of Vader's Little Princess and Darth Vader and Son by Jeffrey Brown.[[Special:Contributions/141.101.104.183|141.101.104.183]] 13:48, 21 July 2014 (UTC)

Isn't ''which he apparently brought with him on the attack on the Forest Moon of Endor'' a pretty big assumption, given a white background? Seems more likely they're on Hoth (Or in his son's bedroom).[[Special:Contributions/108.162.216.86|108.162.216.86]]

;Vibrate?

Fleshlights don't vibrate do they? [[Special:Contributions/108.162.246.202|108.162.246.202]] 18:14, 21 July 2014‎ (UTC)
:It's an available option. [[Special:Contributions/199.27.133.39|199.27.133.39]] 18:29, 21 July 2014 (UTC)
: It wasn't an available option when I bought mine :([[Special:Contributions/108.162.216.86|108.162.216.86]]

"turn on" seems to be a pun. To switch on vs. to excite sexually. Sebastian --[[Special:Contributions/141.101.104.167|141.101.104.167]] 19:10, 21 July 2014 (UTC)

Talk:356: Nerd Sniping

2014-04-30T17:55:32Z

108.162.216.86:

Just because the problem contains an infinite series (or parallel) doesn't mean that it's unsolvable. It's tricky, certainly, and getting the "true" answer involves some rather heavy math, but it's not impossible. Indeed, Google shows that it's already been answered. [[Special:Contributions/76.122.5.96|76.122.5.96]] 20:42, 20 September 2012 (UTC)

I've always had an issue with this problem for one simple reason. In an infinite set of resistors, there is no space to apply a charge, thus there is no resistance. Ohm's law states Resistance = Voltage / I(current). So, in a system where there is no current (creating a divide by zero error), and there is no voltage (no change in electron work capacity, because we don't have a way to excite the electrons, because there is no power) Resistance is incalculable. [[User:Lcarsos|lcarsos]] ([[User talk:Lcarsos|talk]]) 22:22, 20 September 2012 (UTC)

We live in 3 dimensions, just place a battery above the grid with wires going to the 2 points. --[[Special:Contributions/84.197.34.154|84.197.34.154]] 22:59, 24 October 2012 (UTC)

:Not everybody does... --[[Special:Contributions/85.159.196.14|FlatlandDweller]] 11:08, 15 November 2012 (UTC)

This problem is "unsolvable" only if you try to just use the basic methods for finite networks.
There is a page on this at [http://mathpages.com/home/kmath668/kmath668.htm http://mathpages.com/home/kmath668/kmath668.htm] that reports that the cited points have a resistance of '''4/pi - 1/2''' ohms (.773234... ohms).
The 1/2 ohm resistance between adjacent nodes is actually well known.
[[User:Divad27182|Divad27182]] ([[User talk:Divad27182|talk]]) 05:05, 5 October 2012 (UTC)

Solution here as well: http://mathworld.wolfram.com/news/2004-10-13/google/ [[User:Potie15|Potie15]] ([[User talk:Potie15|talk]]) 03:50, 18 March 2013 (UTC)

Nowhere it is said that the problem is unsolvable, just that it is interesting. Of course, the sniping is more effective is the problem is also difficult to solve, because otherwise the victim would get over it quickly. [[User:Dargor17|Dargor17]] ([[User talk:Dargor17|talk]]) 17:47, 16 June 2013 (UTC)

That method for parallel resistors is wrong. You don't divide resistances by the number of paths, you sum the reciprocals and then take the reciprocal of that. The method described only works if every resistor has the same value. While that's true in this problem, it's misleading to pass that off as a method that works for all cases. --[[Special:Contributions/173.245.55.60|173.245.55.60]] 03:32, 1 April 2014 (UTC)
:Good point. I made some slight alterations to clarify that we are assuming the resistors are equal. It seems a better solution than getting into the more complex version of the problem. --[[User:BlueMoonlet|BlueMoonlet]] ([[User talk:BlueMoonlet|talk]]) 12:20, 1 April 2014 (UTC)

Amazing. From the first comment the discussion is diverted from discussing the comic, to discussing the problem presented in the comic. The commentators have been nerd sniped by a demonstration of nerd sniping. Randall is just that good. [[Special:Contributions/108.162.216.86|108.162.216.86]] 17:55, 30 April 2014 (UTC)

547: Simple

2014-01-17T05:24:18Z

108.162.216.86: /* Explanation */

{{comic
| number = 547
| date = February 23, 2009
| title = Simple
| image = simple.png
| titletext = Actually, I think if all higher math professors had to write for the Simple English Wikipedia for a year, we'd be in much better shape academically.
}}

==Explanation==
[[Cueball]] seems to be attending a meeting in a physics facility that has a particle accelerator. The Physicist asks him his thoughts about the Tertiary F.E.L guidance system that is a component of the particle accelerator. This sounds like the normal kind of jargon that you would hear in such a meeting.

As the text below the comic says, Cueball has spent the previous night reading {{w|simple:|the Simple English Wikipedia}}, a simplified version of Wikipedia intended to be easier to understand than the original, and now he finds himself talking in the same simple style. This makes him sound somewhat child-like and uneducated, but in fact he has clearly communicated the ramifications of relying on a sub-system that is known to be faulty. The accelerator would not perform its intended function, and may even be damaged.

From the title text, Randall believes that if people teaching advanced mathematics followed this style, their subject would be more accessible. The implication is that more people would be drawn to studying mathematics and that (naturally) the world would be a better place because of this!

This concept was later revisited in [[1133:_Up_Goer_Five| 1133 Up Goer Five]].

==Transcript==
:Friend: Do you have any thoughts regarding the particle accelerator's tertiary F.E.L. Guidance System?
:Cueball: We can't put the broken part in the machine. It wouldn't smash the right tiny things together. Then the machine might break.
:Cueball: That would be very bad.
:I spent all night reading simple.wikipedia.org, and now I can't stop talking like this.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Physics]]
[[Category:Language]]
[[Category:Wikipedia]]