explain xkcd - User contributions [en]

2321: Low-Background Metal

2021-03-12T01:47:39Z

172.68.65.106: Added comma for clarity.

{{comic
| number = 2321
| date = June 17, 2020
| title = Low-Background Metal
| image = low_background_metal.png
| titletext = The only effect on the history books were a few confusing accounts of something called 'Greek fire.'
}}

==Explanation==
In this comic, a team including [[Megan]] and [[Black Hat]] who have invented a {{w|time travel}} machine presents it and their problems to [[Cueball]]. Time travel is a common trope in science fiction, and specifically [[:Category:Time travel|here on xkcd]], and such a discovery would be likely to change the world as we know it. However, Megan and Black Hat's machine requires the use of "low-background" metal, which is in short supply.

Megan explains that, while delicate equipment is often shielded from radiation by lead, metal produced in modern times is contaminated by {{w|nuclear fallout}} in the atmosphere, which means that the shielding itself has enough radioactivity to interfere with highly delicate equipment. In order to shield this equipment, "low-background metal" is salvaged from sunken ships. Lead ingots from Roman cargo have been used in experiments. The Roman lead was produced before atmospheric nuclear tests occurred{{Citation needed}} and therefore did not have resulting {{w|radionuclides}} in the air used in its manufacture. When it is extracted, lead is naturally contaminated with the radioactive isotope Pb-210, with a 22 year half-life. Because it has spent many centuries continually underwater, it is both shielded from radioactive particles, and has had time for natural radioactivity to fade.

The number of shipwrecks of that age that can be found and successfully salvaged for metal is quite small, which puts this material in short supply. Megan mentions that they have only enough for a single trip. The team realizes (apparently at [[Black Hat]]'s suggestion), that a solution is to use their single trip to take modern military hardware back to the era of the {{w|Roman Empire}} and use it to sink multiple ships. This would both provide for many more shipwrecks to salvage, and give the team a good idea of where those wrecks were, when they returned to modern times. They could also specifically target ships that were in waters that are well-suited for salvage operations.

However, while this might be a pragmatic solution, going back in time to sink ships and murder the occupants doesn't seem like a particularly morally acceptable solution, not to mention opening up potential {{w|time travel paradoxes}} such as what if one of the ship occupants killed was an ancestor to one of the protagonists? If this were a real scenario, there would probably be less drastic solutions available, such as purchasing quantities of lead from the time (would need to convincingly impersonate a local and have something that could be used as currency) and dropping them in the ocean from a (rented) non-destroyed ship, which as a bonus eliminates the need to extract it from the charred remains of a ship later.

Using time travel to retrieve items from the past that are not available in the present is a frequent trope in time travel-related media. Frequently, it is done with the goal of [https://allthetropes.org/wiki/Time_Travel_for_Fun_and_Profit making money], but other purposes are used as well. In the Star Trek movie {{w|Star Trek IV: The Voyage Home|The Voyage Home}}, time travel is used to retrieve whales and transport them to the present. In the book {{w|Timeline (novel)|Timeline}}, time travel is used to record historical events for entertainment purposes. In the movie {{w|Avengers: Endgame}}, time travel is used to retrieve minerals important to a future plan.

{{w|Low-background steel}} is the most famous kind of low-background metal, used in real life for highly sensitive particle detectors in physics and medicine, and is salvaged from ships sunk before 1945 (the {{w|Trinity (nuclear test)|Trinity nuclear test}}). Since this is steel, the ships used typically date back to World War I or World War II.

The title text refers to {{w|Greek fire}}, which was an incendiary weapon invented and employed by the Byzantine empire. It was a flammable liquid, famously said to burn on water, that was used in naval combat to set fire to enemy ships. As it was a closely-guarded military secret, many of the details have been lost to time, and modern chemists have only been able to develop educated guesses of what it ''probably'' was. Randall proposes a rather outlandish alternative hypothesis: that all records of Greek fire were actually in reference to the modern weapons used by the time travelers. It is also notable that, if the time machine was taken to the time of the classical Roman empire, Greek fire would not yet have been a known term. Perhaps the weapon wielded by the time travelers was later conflated with the Byzantines' weapon, or perhaps the time machine was taken to a period a few centuries later than classical Rome.

In [[1063: Kill Hitler]] a single-use time machine is available. It is also used by Black Hat. However, due to the way the time machine in this comic is used, it must be assumed that they can use it again after the salvage of lead from the sunken ships.

==Transcript==
:[Black Hat stands behind Megan who addresses Cueball who stands on the other side of a table with a machine. The machine is a rectangular box with a small dome with one large and two small antennas on top. It seems to point in Cueball's direction as it has a broad protrusion at the back and protrusion at the front that gets smaller towards the tip. The word "Time" is written on the side, and below that is possibly more illegible text.]
:Megan: Our time machine works.
:Megan: But we're almost out of low-background metal.
:Cueball: What's that?

:[Close-up on Megan who lifts her hand palm up.]
:Megan: Modern metal is contaminated by fallout from nuclear testing, and lead also has natural radioactivity that fades over time.
:Megan: To shield sensitive equipment, physicists use lead from sunken Roman ships.
:Megan: But shipwreck lead is hard to find.

:[Back to the original setting, Megan has turned to Black Hat, who has his hand on his chin.]
:Black Hat: How much do we have?
:Megan: Enough for one trip through time.
:Black Hat: ''Hmmm...''

:[The three are now in a helicopter, with Megan piloting, Cueball as a passenger in the back, and Black Hat firing a flamethrower at a Roman ship beneath them through the window behind the cockpit. Two sailors with Roman type helmets are looking on as the stern of their ship catches fire. One of them throwing his arms out to the side. The intact sail is still up behind them and behind that another sailor jumps into the water, down to a fourth sailor already in the water. Two already-burning ships can also be seen to the left of the ship under attack. One is burning all over, with the mast still up but the sail long gone, and the third ship is almost completely sunk, but the part above the water is aflame. Seven small clouds are around the helicopter in the sky.]
:Flamethrower: ''Fwooosh''

{{comic discussion}}

[[Category:Comics featuring Megan]]
[[Category:Comics featuring Black Hat]]
[[Category:Comics featuring Cueball]]
[[Category:Time travel]]
[[Category:Physics]]

Talk:1890: What to Bring

2021-02-04T18:53:56Z

172.68.65.106:

Presumably water in a gun fight _might_ work if the guns involved are particularly old fashioned (e.g. see [https://en.wikipedia.org/wiki/Flintlock Flintlock]) [[Special:Contributions/162.158.154.55|162.158.154.55]] 06:35, 15 September 2017 (UTC) A flintlock style uses a metal 'frizzen' which hinges over the 'pan' into which the priming power is placed. This not only protects the powder from the weather (and a splash), but also keep the powder in the pan as the firearm is moved about. When the mechanism is fired, the flint comes striking down on the surface of the frizzen which both opens the cover and directs sparks into the pan. The type of firearm that might be made inactive with a splash of water is an older design called the matchlock which held a lit cord or match in a mechanism over the open pan. The gun is fired by allowing the match to fall into the pan and detonating the powder.
:Water in a gun fight would also work if the guns are water guns or if the fight is against the Wicked Witch of the West [[Special:Contributions/172.68.65.198|172.68.65.198]] 15:09, 17 March 2020 (UTC)

I see that bringing a lid to a knife or gun fight might serve as some sort of a shield? [[Special:Contributions/141.101.107.66|141.101.107.66]] 06:52, 15 September 2017 (UTC)

If your lid is big enough, you can extinguish a wood fire too [[Special:Contributions/141.101.105.240|141.101.105.240]] 09:50, 15 September 2017 (UTC)

Is this Randall being political about the situation with North Korea? Maybe I'm reading too much into it, although the world would probably be a better place if more people (and countries) followed the tag text. [[User:Fluppeteer|Fluppeteer]] ([[User talk:Fluppeteer|talk]]) 10:29, 15 September 2017 (UTC)

But what if... you bring a wood fire... TO A KNIFE FIGHT?! Also, I'm not the only person thinking about BOTW's lowest-defense shield, am I? [[User:OriginalName|OriginalName]] ([[User talk:OriginalName|talk]]) 11:24, 15 September 2017 (UTC)

US Military personnel use "lid" as a euphemism for their uniform hat. I think that interpretation is represented in the drawing for "lid to a knife fight". [[Special:Contributions/162.158.74.201|162.158.74.201]] 12:57, 15 September 2017 (UTC)

Using a gun to extinguish fire probably was influenced by this official tweet of a sheriff 5 days ago [https://mobile.twitter.com/pascosheriff/status/906712903868469249 "To clarify, DO NOT shoot weapons @ #Irma. You won't make it turn around & it will have very dangerous side effects"], which was necessary after stupid people started to try to fight the hurricane with guns. Sebastian --[[Special:Contributions/172.68.110.94|172.68.110.94]] 15:23, 15 September 2017 (UTC)

The sentence "which often come with lids suited to making an airtight seal" is inaccurate. Lids don't form an airtight seal, and airtightness is not necessary to extinguish a pan fire.--[[User:Pere prlpz|Pere prlpz]] ([[User talk:Pere prlpz|talk]]) 23:58, 15 September 2017 (UTC)

The phrase "don't bring a knife to a gun fight" is not a statement of general naive lack of preparation, but is specifically used to advocate literal firearms as a means of defense over literal knives. The "gun fight" refers to encounters with armed criminals who, the phrase suggests, will still use their gun to your disadvantage whether or not you are capable of fighting back. It has been subverted occasionally as an implied threat (usually in drama rather than reality) when the situation is reversed, i.e. the criminal is armed with a knife and the would-be victim is armed with a gun. The violence implied by "a gun fight" tends to restrict more metaphorical use of the phrase. The title text seems to be based in the original meaning, with the implication that Randall expects a gun being used against an armed criminal to escalate violence. {{unsigned ip|162.158.74.231|20:08, 16 September 2017}}
:Struggling to work out whether this comment is tongue in cheek, or for real.[[Special:Contributions/162.158.155.32|162.158.155.32]] 16:31, 18 September 2017 (UTC)
:Hmmm... Since I don't see the humour in this comment if it was meant as a joke, and trolling is just pointless, I'm going to go ahead and treat it as a serious comment. No. Just no. A literal knife to a literal gun fight would be where the saying came from, but even then only as a metaphor or simile, as an issue easily understood. It should be obvious to anyone who knows how guns work that the gun would have an almost complete advantage. The saying actually means being on unequal footing in some conflict, where the person being warned is trying to attack or go against someone who is better prepared. The stereotypical jock trying to argue a point against the captain of the debate team (presumably the captain being the most experienced at making logical well-reasoned arguments, and as such would have no problem winning such an argument). A brand new private in the army challenging a multi-stipe sargeant to a fist fight (presumably anyone who has risen to the rank of sargeant and gained several stripes besides is quite experienced at fighting). A child challenging an Olympic medalist to a race (besides being an adult, presumably someone who has won a medal has tremendous ability at whatever kind of race this is). "Bringing a knife to a gunfight" is a common SAYING to describe such situations. [[User:NiceGuy1|NiceGuy1]] ([[User talk:NiceGuy1|talk]]) 04:01, 19 September 2017 (UTC)

Just noticed that the comic on xkcd got a little correction: The "Water to a knife fight" Cueball was missing an arm. --[[Special:Contributions/162.158.202.202|162.158.202.202]] 23:12, 17 September 2017 (UTC)
:Here's still the old image. Can anyone update it? --[[Special:Contributions/162.158.202.52|162.158.202.52]] 21:59, 22 September 2017 (UTC)

The gun is the only thing with two uses, so it's ''obviously'' the most useful. [[User:1337357|1337357]] ([[User talk:1337357|talk]])
:A nuke would neutralize all of these threats, so obviously it would be the "most" useful. But nuking a wood fire to put it out would probably be overkill. Randall isn't trying to say that something is the "most" useful, he's just showing us different scenarios.[[User:Herobrine|Herobrine]] ([[User talk:Herobrine|talk]]) 13:13, 1 October 2017 (UTC)

Is this a co-violence matrix?

This should probably be in the Charts category, but I can't figure out how to do so. [[Special:Contributions/172.68.65.106|172.68.65.106]] 18:53, 4 February 2021 (UTC)

421: Making Hash Browns

2021-01-19T01:48:48Z

172.68.65.106: /* Explanation */

{{comic
| number = 421
| date = September 5, 2008
| title = Making Hash Browns
| image = making_hash_browns.png
| titletext = There are at least fourteen ways this could go badly (seventeen if that fork is a dangerous crossbreed.)
}}

==Explanation==
[[Cueball]] is attempting to make {{w|hash browns}}. A hash brown is a way of serving a potato where the potato has been diced or shredded in some way, then pan-fried. Cueball's method for making hash browns, though, is rather unique. He is throwing potatoes into the air and striking them with a flaming tennis racket at his friend, who is holding a tray with a dangerously tilting half filled glass balanced on top. He (the friend) is also holding a fork in the other hand.

The idea is that the tennis racket would simultaneously dice the potato, fry it, and then launch the completed product towards his friend's plate. In reality, this probably wouldn't do much. To properly {{w|Pan frying|pan-fry}} food, it must be cooked in a pan with some oil to lubricate the food, with enough time for the heat to transfer through the oil and spread properly through the food. Hitting a potato with a flaming tennis racket would not cook it as it would strike it too quickly, and it probably wouldn't dice it either unless the wire of the racket is incredibly sharp. Cueball would probably just end up batting a not even hot, uncooked, unprepared potato at his friend, while simultaneously burning his own hand. In the case that the wires did actually cut through the potato, then the potato would not be moved forward but actually end up behind the racket.

The title text comments on how many ways this experiment could go badly (14), and jokes that there are even more potential problems (17) if the fork Cueball's friend is holding is a cross-breed (see [[419: Forks and Spoons]] which was published only four days earlier. By reading this comic it should be clear what could go wrong if they were included in the equation - 3 more ways would be a low estimate...)

It's unclear what Randall may or may not have had on his mind with regards to specific ways the situation in the comic could go wrong. But here are several potential ways the activity could go wrong without including {{w|Sporks}}:
#Cueball could burn himself with the flaming tennis racket.
#The can of gasoline could leak and then Cueball could drop the racket, causing a fire to spread.
#Cueball may fail to hit the potato and it would get dirty from the ground.
#Cueball may fail to hit the potato and whack himself with the aforementioned flaming tennis racket.
#Cueball may fail to hit the potato and hurt himself as it lands on his face.
#Cueball may hit the potato and knock the plate out of his friend's hand, smashing it.
#Cueball may hit the potato and knock the glass out of his friend's hand, smashing that instead.
#Cueball might hit his friend's arms with a potato (flaming hot or not) causing the friend to drop the plate,thereby spilling glass,porcelain,a potato,and Orange juice everywhere.
#Cueball might instead hit the potato at his friend's head.
#Cueball could accidentally launch the tennis racket itself (if he has exceptionally poor grip) at his friend.
#Cueball could drop the tennis racket onto the can of gasoline, causing it to explode.
#Cueball's friend may lose his balance with the plate, dropping it and/or the glass onto the ground.
#Even if none of the above happened, Cueball would fail to actually ''cook'' the potato,
#Likewise, Cueball would probably not succeed in dicing the potato.
#And he could miss hitting his friend's plate.
#A {{w|velociraptor}} could appear out of nowhere and eat the potato, then proceed to devour Cueball and his friend. (A possibility which likely plagues Randall's mind daily.)

==Transcript==
:[Cueball stands holding a flaming tennis racket. He is throwing a potato in the air as if to serve like a tennis ball. Behind him is a red gas can and a sack of potatoes. Across from him is a another person holding a fork in one hand and balancing a serving tray with a glass holding an orange liquid in it.]

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics with color]]

2369: All-in-One

2021-01-15T05:22:01Z

172.68.65.106: /* Functions completely unrelated to printing or scanning */

{{comic
| number = 2369
| date = October 7, 2020
| title = All-in-One
| image = all_in_one.png
| titletext = Changes with this update: If you use the combined scan-shred function, it now performs them in that order instead of the reverse, saving a HUGE amount of CPU time.
}}

==Explanation==
This is an xkcd-style parody of an {{w|all-in-one printer}}, a printer which typically can perform several functions, usually printing, scanning, copying, and faxing. This machine starts off with fairly standard printer functions but quickly becomes absurd. The machine is accordingly oversized, making room for all the status indicators and (presumably) the extra internal parts required to accomplish the uncommon functions.

The title text says that if both the "scan" and "shred" options are selected, it now scans things ''before'' trying to destroy them. Previously the machine destroyed documents and then scanned the pieces and tried to reconstruct them, which takes a large amount of processing power, as the attempts to recover the German Stasi Documents have shown, in addition to the fact that it is extremely hard to correctly scan shredded and crumpled documents.{{Citation needed}} The possibility of doing so raises the possibility that this printer itself is a even more complex computer than one would expect a multi-function printer to be, or that its driver can monopolize a host computer. It is also worth noting that if one selects "copy" and "shred" one could also just do nothing with the same effect (apart from generating some shredded paper, and assuming that there was nothing noteworthy about the original physical document).

===List of functions===
 Certain functions are lit green, indicating they are in use. To show which ones are in use, they are highlighted green (selected).

====''Functions that most all-in-one printers do''====
*'''{{w|Printer (computing)|Print}}''' (selected): The most common function that a printer needs to do. A digital document or graphic exists on a computer, is sent to the printer and the printer transfers the document onto paper using ink or toner.
*'''{{w|Photocopier|Copy}}''': A copy function allows a user to place a document on the integrated/linked scanning bed and the printer will immediately make a copy of the document as if a traditional 'analogue' photocopier.
*'''{{w|Fax}}''' (selected): A fax function sends a scanned document by telephone to another telephone number. The receiver fax machine will reconstruct the document and print it. A machine that has this function is usually also able to act as a receiver for faxes sent from elsewhere, though that setting wouldn't be visible in this configuration group.
*'''{{w|Image scanner|Scan}}''': A scan function is used to optically scan images or documents into digital forms so that they can be used by computers. It can be seen as the reverse operation of the printer function.
*'''{{w|Collate}}''' (selected): To sort multiple copies of printed documents into sequences of individual page order, usually across multiple output trays having one sequence for each copy, especially before binding.
*'''{{w|Staple (fastener)|Staple}}''' (selected): To staple together multipage documents, especially for each collated copy. This function is usually found only in high-end printers.

====''Functions that relate to printers or scanners, that most cannot do''====
*'''Staple Removal''': Although mechanical removal of staples can be done by various devices, it's often not a ''simple'' task. Staples can be bent and mangled in many ways, and detaching them from paper without causing damage can require fairly complex intelligence.
*'''{{w|Paper shredder|Shred}}''': A shredder function is used to destroy paper for privacy or security by cutting it into strips or fine particles. Normally this task is handled by another specialised machine called a shredder, but this time it is already inbuilt into the printer.
*'''{{w|Translate}}''': If the paper text is in another language, this would presumably translate it for you — after scanning and {{w|Optical character recognition|OCRing}}. This would actually be a helpful function and may be available on recent scanner-printers, although usually in the software that comes with the printer, on the host computer, rather than inside the printer itself.
*'''Add those {{w|Perforation|perforated}} edge strips that are so fun to tear''': In an earlier era, {{w|dot matrix printers}} and {{w|line printer|line printers}} were the common standard, and used a type of {{w|continuous stationery}}, which was manufactured with perforated strips along each side, with regularly spaced holes which allowed spiked wheels to advance the paper through the printer. Tearing these strips off after printing was once a standard task when using a printer. This type of stationery is now obsolete, but many people of Randall's generation become oddly nostalgic about removing the strips from the old style of paper -- the strips are kind of fun to play with. Note that the old stationery was designed such that the remaining page typically had a "standard" paper width, with the strips adding additional width. It's unclear if this function is adding ''perforations'' to standard paper, which would leave it too narrow once the resulting edge strips were removed, or is somehow adding perforated ''strips'' to it.

====''Functions completely unrelated to printing or scanning''====
*'''Summarize''': Presumably this function would summarize a printed material for the user. Similar to the translate function, a document would need to be scanned and OCRed first. Then a machine learning algorithm would comprehend the text and reduce it in length while keeping the important points. {{w|Automatic_summarization|Automatic text summarization}} does exist, although the technology is not as widely used as automatic translation.
*'''{{w|plagiarism|Plagiarize}}''': This function is unclear. Maybe it would plagiarize a paper for a certain subject? It would also be legally questionable. (Maybe it plagiarizes printer techniques, in which case this might be useful, though only in edgecases)
*'''Roll''': This function would probably roll up paper into a roll, like how the newspaper is rolled up for distribution by paperboys.
*'''Burn''': Perhaps the printer has this function for greater assurance that sensitive information will be irretrievably destroyed. Historically, some printers could be at risk of catching fire if they jammed in a particular way, and so the "{{w|lp0 on fire}}" error code was created to signal that it should be investigated urgently.
*'''Eat''': A printer is often said to "eat" paper by mangling either the input or output. Printer failure is also the modern descendant of the classic excuse for late homework, "{{w|the dog ate my homework}}".
*'''{{w|paper airplane|Fold airplane}}''': This function makes paper airplanes out of paper stored in the printer, or documents being printed. Paper airplane folding machines [https://www.youtube.com/watch?v=MSdb_Rpv5p0 are a thing], so it'd be possible to design something to fold an origami flower, as well.
*'''{{w|Origami}} flower''': Similar to the previous one, this function makes flowers using the origami paper folding process.
*'''{{w|Corrugate}}''': {{w|Corrugated fiberboard}} or cardboard is a kind of crinkled paper sandwiched between two sheets. This provides structural strength for low weight. Printers that jam can produce a paper that looks corrugated, but this is not an intended function, and corrugated fiberboard is not made with printers.
*'''{{w|Papier-mâché}}''': (Literally "chewed paper") is a composite construction material consisting of paper pieces, bound with an adhesive, often a flour paste. The printer could use its "shred" and "eat" functions to produce the necessary materials, and any leftovers could be composted with the "biodegrade" function.
*'''{{w|Découpage}}''': An art form where paper printed with decorative images is glued onto an object (typically boxes, but also furniture) and covered with many layers of varnish so that the images appear painted onto the object.
*'''Notarize''' (selected): A {{w|notary public}} is a person certified by a government to attest that certain kinds of legal documentation are legitimate and executed. All-in-one printers and scanners may be able to recognize certain signs of legitimacy (e.g. the {{w|EURion constellation}}), but unless this printer has some tactile sensation, it cannot certify the identity of the person who signed the document as a human can.
*'''{{w|Biodegrade}}''': This would biodegrade the paper. Whether this would send it to an organic waste plant (which would be helpful) or actually house a composter inside the printer (which would be gross){{Citation needed}} is unknown.
*'''Crumple and throw at trash like basketball''' (selected): Many people, when done with a piece of paper, will crumple it up and throw it into a trash can from a distance as if playing basketball. This wouldn't be a very useful feature in a printer, especially relative to its complexity. For one thing, it would prevent the person who printed the document from using it (even if the user intends to throw away the paper eventually, presumably they need to use it at least once or they wouldn't print it), and it would also deny the user one of the few pleasures available in the office environment.

==Transcript==
:[A large printer-like machine, with the label All-in-One Paper Processor on the top left of it. There are three columns of functions, with a few of them having a green light. At the top of the machine is a "paper feed" tray. At the bottom of the machine, is a large hole, for outputting the paper.]

:'''Column 1'''
:*Print (lit green)
:*Copy
:*Fax (lit green)
:*Shred
:*Scan
:*Translate
:*Summarize
:*Plagiarize
:*Collate (lit green)

:'''Column 2'''
:*Staple (lit green)
:*Remove staples
:*Add those perforated edge strips that are so fun to tear
:*Roll
:*Burn
:*Eat

:'''Column 3'''
:*Fold airplane
:*Origami flower
:*Corrugate
:*Paper-mâché
:*Découpage
:*Notarize (lit green)
:*Biodegrade
:*Crumple and throw at trash like a basketball (lit green)

{{comic discussion}}

[[Category:Comics with color]]