explain xkcd - User contributions [en]

2199: Cryptic Wifi Networks

2019-09-08T10:37:05Z

162.158.134.16: /* Explanation */ +links for DrWho

{{comic
| number = 2199
| date = September 6, 2019
| title = Cryptic Wifi Networks
| image = cryptic_wifi_networks.png
| titletext = They actually showed up on the first scan by the first WiFi-capable device.
}}

==Explanation==
{{incomplete|Created by a Toshiba-U2187-OfficeLink-Net46UHZ. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}

In the comic, a character with a knit cap is on top of a high mountain in a remote location. He sees a Wifi network name listed on his handheld device, perhaps a cellular telephone. Cryptic {{w|Wi-Fi}} (or Wifi) network names, called {{w|Service set (802.11 network)|Service Set Identifiers}} (SSIDs) are part of the joke about not knowing where the corresponding {{w|wireless router}} is located, suggesting they are unexplained phenomena instead of wireless radio devices. Some of the earliest Wifi devices like printers and {{w|internet}} routers advertised cryptic SSIDs, as do many of them today. In 1998, {{w|Lucent}} introduced the [https://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Wavelan-IEEE.html WaveLAN IEEE], the first {{w|integrated circuit}} chip set supporting the IEEE 802.11 wireless {{w|LAN}} protocol, spinning off {{w|Agere Systems}} to produce them in 2000. WiFi followed mid-1990s short-range wireless networks like {{w|Bluetooth}} and radio internet protocols like the 1980s {{w|KA9Q}}, with roots going back to the earliest {{w|ticker tape}} digital telegraphy systems from the mid-1850s. [https://techtalk.gfi.com/the-31-funniest-ssids-ive-ever-seen/ Humorous SSID names] are not uncommon.

The SSID displayed is '''Toshiba-U2187-OfficeLink-Net46UHZ''' which is 33 characters long, unfortunately one character more than are allowed. {{w|Toshiba}} is a multinational electronics conglomerate manufacturing many products including untold multitudes of different kinds of printers over the years. Such devices often have embedded {{w|wireless access point|wireless access points}} including the manufacturer name in the SSID. Many network names contain words like Net, Office or Link. The code might indicate a model U2178 device from Toshiba named (or having an interface program named) OfficeLink, which has a sub-model number or operates on a wireless network designated 46UHZ. That "Hz" is an abbreviation for {{w|Hertz}} suggests that designation may or may not have something to do with the frequency on which the transmitting device operates. Or U2178 could be a serial number for a user or a utility pole. We don't know whether the SSID is connected to a network of more than one or is just one device. The padlock icon indicates that a password is required to communicate. The "join other network" option allows for manually typing SSIDs to attempt to connect with networks which are not configured to display their SSIDs.

While the most likely explanation in an office environment might be a printer plugged in somewhere nearby, other possibilities include a television, cryptocurrency mining rig, speaker, pacemaker, alarm system, fashion accessory, autonomous antimissile defense system node, hobby project, surveillance device, {{w|Loon LLC|balloon}}, distributed denial of service attack platform malware-infested coffee pot, {{w|Starlink (satellite constellation)|satellite}}, vending machine, telecommunication facilities, {{w|Facebook Aquila|solar-powered drone}}, distributed exoskeleton, visiting interstellar civilization, power-to-gas pipeline valve, [http://www.geekculture.com/joyoftech/joyarchives/2340.html ransomware worm nest,] or anything else in the Wifi {{w|Internet of Things}}. Sometimes, the {{w|ionosphere}} reflects radio waves, vastly increasing the distance that they can travel to and from remote locations.

Network names can be used to track the geographic locations of mobile devices, for example in the {{w|Wi-Fi positioning system}}. Google {{w|street view}} equipment records locations of networks to assist with {{w|geolocation}}. Location information can be searched in tools like [https://wigle.net/ Wigle] or [https://openwifimap.net/ OpenWifiMap]. The {{w|Institute of Electrical and Electronics Engineers}} (IEEE) committee number for WiFi is {{w|IEEE 802.11|802.11}} which is composed of sub-committees like {{w|IEEE 802.11ad|802.11ad}}, designing the 60 GHz Multiple Gigabit Wireless System (MGWS) and {{w|IEEE 802.11ay|802.11ay}} working on {{w|MIMO|multiple input, multiple output}} (MIMO) bandwidth enhancements. [https://www.toshibatec.com/cnt/products_overseas/printer2/mobile_printer/b-fp3d/ This Toshiba Wifi printer] supports the "802.11 a/b/g/n" Wifi protocols. The {{w|List of router firmware projects|software which produces SSID listings}} is administered by {{w|List of wireless community networks by region|network communities}} and depends on {{w|Wireless mesh network|mesh configurations}}. Alternatives include [https://news.ycombinator.com/item?id=20861948 bluetooth mesh networks] and other {{w|wireless ad hoc network|''ad hoc'' networks}} to provide internet connectivity services.

The title text indicates that the first WiFi networking client interface displayed unexpected SSIDs. If true, this could potentially rule out all of the alternative explanations other than an alien visitation, a software bug, rogue industrial espionage, time travel, trans-multiverse or trans-dimensional communication, hardware misconfiguration, the {{w|simulation hypothesis}}, or the supernatural. (It is worth noting that cryptic-sounding Wi-Fi networks actually being generated by a time-traveling alien entity as a trap was used as a plot device in the 2013 ''{{w|Doctor Who}}'' episode "{{w|The Bells of Saint John}}".)

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

:[A human with a knit cap and a backpack is checking his phone at the highest mountain in a mountainous landscape.]

:Phone: Available WiFi Networks
:Phone: Toshiba-U2187-OfficeLink-Net46UHZ
:Phone: [in gray] Join other network

:[Caption below the comic:]
:Tech Trivia: No one actually knows what devices produce those cryptic WiFi networks. They just appear at random across the Earth's surface.

{{comic discussion}}

Disappearing Sunday Update

2019-08-05T04:02:05Z

162.158.134.16: /* Explanation */

{{comic
| number = 2185
| date = August 5, 2019
| title = Disappearing Sunday Update
| image = disappearing_sunday_update.png
| titletext = This comic won't exist in the archives. NOTHING IS REAL.
}}

==Explanation==
{{incomplete|Created by UNUSUAL MEANS. Please mention here why this explanation isn't complete. Do NOT delete this tag too soon.}}
The comic claims to be a special Disappearing comic that will disappear Monday August 5th, and is an advertisement for the upcoming book "How To".
This includes a drawing of the cover, on set of pages, and a sampling of the table of contents of the book.
The second part of the comic apologizes for various bots that automatically catalog xkcd comics that might break because of this special comic.
This website is one example assigning the comic a number of 2185 despite the comic not having a designated number. The comic even broke the xkcd site its self as the previous comic (2184) has a next button that links to comic 2185 (which does not exist) and displays a [http://http.cat/404 404] error.
One of the bot methods mentioned may be in reference to [http://www.xkcd.com/2180 2180 : Spreadsheets] where Cueball debates making a real program to do a task, or to use a spreadsheet instead.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
~SPECIAL DISAPPEARING SUNDAY COMIC~

I'm posting this ephemeral sunday update to let you know that I wrote a book! It's a guide to solving everyday problems in terrible ways using science.

It comes out next month, and it's available for preorder now.

[Arrow to image of book] The cover looks like this

[Arrow to image of sample pages of the book] and the inside looks like this.

Chapters include:
How to charge your phone
How to throw a pool party
How to move
How to build a lava moat
How to ski

[Another image of sample pages]

You can learn more and preorder it at xkcd.com/how-to

and read an excerpt at blog.xkcd.com

If you read xkcd through unusual means, including apps, custom screen-scraping systems, google reader clones, twitter bots, bash scripts, gopher portals, lynx-based ascii art browsers, third-party sceond life feeds, rfc 2549, or massive google docs sheets full of =IMPORTHTML() and =IMAGE() formulas, I hope this ephemeral ghost comic doesn't break them too badly.

It will disappear with the normal monday update.

(At least, I think it will. I've never tried this before. So I'm honestly not sure what the server will do.)
{{comic discussion}}

2079: Alpha Centauri

2018-12-01T23:52:34Z

162.158.134.16: s/likely water/possibly water/g i seem so excited by this planet i keep looking at this page. i looked at that chart again and saw only around 30% of the area indicated water, so I guess that's possibly not likely.

{{comic
| number = 2079
| date = November 30, 2018
| title = Alpha Centauri
| image = alpha_centauri.png
| titletext = And let's be honest, it's more like two and a half stars. Proxima is barely a star and barely bound to the system.
}}

==Explanation==
{{incomplete|Created by a SOLAR SAIL. It would be good to enumerate similar projects. Do NOT delete this tag too soon.}}
{{w|Alpha Centauri}} is the closest star system to our solar system, being 4.37 {{w|light-year}}s away. As such, there are numerous ongoing plans and projects to journey to, and explore the star system, especially since {{w|Proxima Centauri b}} was found in 2016 to possibly have liquid water oceans and a very thin atmosphere. Ponytail announces such a project using a {{w|Voyager program|Voyager}}-like probe.

However, the offscreen person is against her idea, for the strange logic that "Alpha Centauri sucks". He says that he looked "online" and that the system "only has three stars". This is a pun regarding online reviews. Online rating systems, such as {{w|Yelp}}, often use {{w|Star (classification)|star rating system}}s, with more stars indicating higher quality, up to an arbitrary maximum, such as five stars to indicate the best rating. Thus 3 stars out of 5 stars in a 5-star rating system would theoretically be a "middling" rating, equating to a C grade, whereas in a 10-star rating system 3 stars out of 10 stars would be very poor quality. The Alpha Centauri star system has 3 ''physical'' {{w|star}}s: Alpha Centauri A, Alpha Centauri B, and Proxima Centauri. The offscreen person has misconstrued this fact of the system as some kind of review.

A previous comic, [[1098: Star Ratings]], points out that star ratings below 4 out of 5 tend to be seen as "crap".

The title text furthers the pun. Some online star rating systems also allow partial stars, such as a half-star, to allow more precision in rating (i.e. rating 2.5 stars instead of forced to chose 3 stars or 2 stars), or display an average collective rating as partial stars (i.e. showing 2.5 stars when five people have rated 3 stars and five people have rated 2 stars). Alpha Centauri's "half star" refers to Proxima Centauri, a {{w|red dwarf}}, which is a type of low-mass star. According to the offscreen person, this barely qualifies it to be a star. Furthermore, Proxima Centauri is nearly 13,000 AU (0.21 light years) away from the other 2 stars in the system, so it was long unknown whether Proxima Centauri was gravitationally bound to the Alpha Centauri star system.

===Calculations===
All numbers are rounded after subsequent calculations.

4.367 light years / 35 years = 0.12477 light years/year

0.12477 light years/year * 5.879e+12 miles/light year = 733,484,000,000 miles/year

733,484,000,000 miles/year / 365 days/year / 24 hours/day = 83,000,000 Miles/hour / 1.60934 miles/kilometer = 134,000,000 Kilometers/hour

According to [https://www.space.com/41447-parker-solar-probe-fastest-spacecraft-ever.html space.com] the fastest spacecraft ever will be the Parker Solar Probe which will reach 430,000 mph (692,000 km/h) as it reaches its closest point orbiting the sun. This is just over half of 1% of the needed speed of the Alpha Centauri vehicle proposed in the comic. The Voyager 1 spacecraft, launched in 1977, is currently traveling at about 38,000 mph (61,000 km/h).

The above math assumes a constant speed, and requires a speed of ~0.0001c. Assuming a constant acceleration from rest (non-relativistic math follows):

35*365.25*24*60*60 = 1.10e+9 seconds in 35 years

4.367 * 5.879e+12 = 2.57e+13miles, 4.13e+13 km, 4.13e+16 m.

x = 1/2*a*t2

a = 2*x*t -2

Assuming constant acceleration to the halfway point and constant deceleration to the destination, (otherwise you streak through the system, barely observing anything):

ttrip = 2*thalfway

a = 2*2.06e+16*(5.50e+8) -2 = 0.136 m/s2, roughly 1/80 gravity.

vhalfway = a*thalfway.

Top Speed: 75,000,000 m/s ~ 1/4*c.

Assuming E = F*d, 0.136*1*4.13e+16 = 5.37e15 Joules will be required for each kilogram carried to Alpha Centauri in 35 years.

This would require an unimaginable amount of mass for a conventional chemical rocket, is a completely impractical power requirement for any sort of passive solar sail concept.

Further, the top speed is fast enough to require a recalculation using relativistic physics to model the problem. This means that the energy budget will need to increase, as the relativistic mass of the probe will increase, requiring more force (and thus more energy) to accelerate and decelerate near its top speed than this calculation returns.

[https://en.wikipedia.org/wiki/Breakthrough_Starshot Active], laser based propulsion methods require currently non-existent and purely specualtive laser and materials technologies, as well as a powerplant equivalent to 12,500 of the [https://www.power-technology.com/features/feature-largest-nuclear-power-plants-world/ World's Largest Nuclear Plant] to transport sub-gram masses on this timescale. This also assumes that any probes can be steered accurately enough across interstellar distances to come close enough to image with any resolution the bodies they will be passing at a non-trivial fraction of c.

Short of FTL travel or near-perfect mass-energy conversion technology, transporting more than fraction of a gram of material to Alpha Centauri in a human lifetime will be unachievable. Short of an enormous breakthrough in power generation, transporting even a fraction of a gram is impossible.

Nonetheless, [http://breakthroughinitiatives.org/challenges/3 Breakthrough Starshot] is attempting to send many gram-sized probes to Alpha Centauri within the century. Following current technological trends, they expect the efficiency of laser-based propulsion to increase by launch time, allowing launches driven by an unreasonably-large-but-achievable amount of power. The top speed needed is halved by refraining from slowing at all at the destination: the probes will aim a distance away from the target, so that it traverses by slowly enough for a camera to rotate and track it, even at near-light speeds. To account for error and space dust, the plan is to launch many tiny probes simultaneously. They may only be able to accomplish their goal if they can get enough funding to actually affect the global economy enough to make the technologies they require more efficient to produce. Launches would additionally burn incredible quantities of natural gas.

==Transcript==
:[Ponytail stands on a podium giving a presentation in front of a slide with an image of a [https://wikipedia.org/wiki/Voyager_1 Voyager-like] spacecraft.]
:Ponytail: Our probe can reach Alpha Centauri in under 35 years.
:Offscreen voice: We should go somewhere else. Alpha Centauri sucks.
:Ponytail: Huh? It's the closest, most convenient system!
:Offscreen: Yeah, but I checked online and it only has three stars.

{{comic discussion}}

[[Category:Comics featuring Ponytail]]
[[Category:Space probes]]
[[Category:Online reviews]]

Talk:2073: Kilogram

2018-11-16T17:34:23Z

162.158.134.16:

I didn't know that weights and currencies could be converted 1:1, that's cool! [[User:Fabian42|Fabian42]] ([[User talk:Fabian42|talk]]) 16:37, 16 November 2018 (UTC)

I wish they ''had'' redefined the kilogram a little bit. It would have been neat if 1 kg was exactly the weight of 1 dm^3 (1 litre) of water under one atmosphere of pressure. Right now it's soooo close. It's a good enough estimate for simple maths, but whenever you tell people that a litre of water weighs one kilogram the pedants comes out of the woodworks... [[User:Kapten-N|Kapten-N]] ([[User talk:Kapten-N|talk]]) 16:50, 16 November 2018 (UTC)

Up until 1964 a litre (and therefore actually the metre too) used to be defined as the volume that water with mass 1kg takes. But this is not good for exact measurements not only because you need exactly reproducable temperature, pressure (not so problematic, because you can measure them and then calculate the divergence) and gravity (not so easy to measure, because you need an exact mass and exact masses are impossible to keep the same), but also because you need pure water free of any polutions of other stuff (hard and expensive) and even free of tiny amounts of isotopes which are deuterium and tritium (even way more expensive).
Because the water that was used then was never close to pure the actual weight of water nowadays is 0.99997kg at 4°C and 1.013bar and I don't know which value for g. There is also another definition which I like, but is hard to measure in real life scenarios: E=mc². A kilogramm should be 1/c² of the mass which anything becomes heavier that you accelerate by the energy of one Joule. --[[Special:Contributions/162.158.90.150|162.158.90.150]] 17:11, 16 November 2018 (UTC)

Actually, for the new definition of the kilo using the Kibble balance you need to measure the gravity... [[Special:Contributions/162.158.134.16|162.158.134.16]] 17:34, 16 November 2018 (UTC)

Welp, looks like 1 kg, a.k.a. 1 lb, a.k.a 2.2 lb, is now officially defined to have zero mass.
[[Special:Contributions/172.69.50.28|172.69.50.28]] 16:56, 16 November 2018 (UTC)
:…or infinite. [[User:Fabian42|Fabian42]] ([[User talk:Fabian42|talk]]) 16:59, 16 November 2018 (UTC)
::What I understand: the joke is not (only) about 1 (old) kg = 1 (old) lb, but (also) about 1 new kg = 1 old lb... or 1 new lb = 1 old kg :^) Or about a ring of positive characteristic --[[Special:Contributions/188.114.102.94|188.114.102.94]] 17:08, 16 November 2018 (UTC)

Talk:54: Science

2018-06-28T22:56:01Z

162.158.134.16: Had to call out the obvious error in the inverted axis of the graph

It's also commonly called "Microwave Background Radiation" because where the radiation peaks at 160.4 GHz is in the microwave range of the electromagnetic spectrum. --[[User:Dangerkeith3000|Dangerkeith3000]] ([[User talk:Dangerkeith3000|talk]]) 18:02, 13 March 2013 (UTC)

;Error - Inverted graph!
Am I the only one who came here confused because the graph is wrong? The shape of the graph is clearly that of blackbody radiation - on a wavelength axis! However Randall titles the axis GHz (pointing right) which is the inverse of wavelength (of course on a wavelength axis, the curve should not extend down to zero). But look up the graph on Wikipedia, and notice that it's on a wavelength scale and looks exactly like this - even better, google "black body radiation" images, and notice how ~95% of them show the radiation on a wavelength scale for some reason. But scroll down, and eventually you'll see one on a frequency scale. It looks quite different!
Also, the blackbody radiation is known for its rather sharp high frequency cutoff (or low wavelength), which Randall accidentally got inverted here, and placed at zero... It shows much more dramatically on frequency axis, which is why you can very clearly see that this graph is NOT a radiation graph on a frequency axis - it goes on to infinity.
Anyway, sorry for the rant - but it's Science bitches, and axis' matter! Especially if you are going to invert one of them! - Richard [[Special:Contributions/162.158.134.16|162.158.134.16]] 22:56, 28 June 2018 (UTC)

;Title Text Meaning

As can easily be seen from the page's history, Dgbrt and I have been locked in a minor edit war over the meaning of the title text. I claim that Randall is simply complimenting the readers who happen to know what the formula and curve mean. Dgbrt thinks otherwise; I will let him explain his interpretation.

Please add to this discussion so we may come to a consensus on its meaning. Thanks. --[[User:Quicksilver|Quicksilver]] ([[User talk:Quicksilver|talk]]) 23:18, 25 August 2013 (UTC)

Glad to oblige. I think we need to draw a distinction between what Randall means and what some people might like him to mean. Many people don't agree that the universe started with a Big Bang, whether because they're cosmologists who support an alternative scientific theory, or because they're young earth Creationists who hold that God created the universe about 6000 years ago, or because they're philosophers who hold it self-evident that something can't come out of nothing, or for whatever reason.

Now, I'm not going to say which of those (if any) I believe, because it really doesn't matter in this context - and neither is it important (''in this context'') what Quicksilver or Dgbrt believes. What we have to keep clear in our minds is that this site is about explaining the cartoons, not projecting particular philosophical standpoints onto Randall's mildly ambiguous phrasing. (When he wrote it, I doubt very much whether he realised he was writing ambiguously.)

The xkcd series, throughout its history, shows not only Randall's firm belief in the scientific method for establishing plausible explanations of the way the universe works, but also his antipathy towards historical explanations that seem to be at odds with observable evidence and even historical record. See #803 and #1255 for obvious examples.

Given Randall's known love of science and the absence of any firm clues that he was being heavily ironic and running massively against type, I think we have to conclude that he was either praising those who could identify the science he was talking about, or just possibly was trying to cause a Wikipedia search spike! --[[User:BinaryDigit|BinaryDigit]] ([[User talk:BinaryDigit|talk]]) 07:17, 8 April 2014 (UTC)

So no one's gotten the bonus points yet?! He was asking to identify the science in question. When he says "It works", I'm sure he was not meaning that blackbody radiation works. This graph was the key to one of the biggest leaps in human understanding.--[[User:ChrisfromHouston|ChrisfromHouston]] ([[User talk:ChrisfromHouston|talk]]) 06:23, 8 September 2014 (UTC)
:He meant that Science in general works. And this is just an example that proves this point. And he has explained what the graph is on his own page in the shop. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 20:16, 30 April 2015 (UTC)

1842: Anti-Drone Eagles

2017-05-26T12:29:41Z

162.158.134.16: reverted to citation needed (a citation isn't actually necessary here)

{{comic
| number = 1842
| date = May 26, 2017
| title = Anti-Drone Eagles
| image = anti_drone_eagles.png
| titletext = It's cool, it's totally ethical--they're all programmed to hunt whichever bird of prey is most numerous at the moment, so they leave the endangered ones alone until near the end.
}}

==Explanation==
{{incomplete|People at work.}}
Law enforcement and security agencies often use birds of prey to combat drones flying unlawfully over restricted sites. This is often more cost effective than using technological means (such as scramblers and counter-drones) and safer for the public than using conventional weaponry (such as shotguns).
See for example http://www.bbc.com/news/av/world-europe-35750816/eagles-trained-to-take-down-drones.
Eagles, being predators, have natural tendencies to attack the central components of drones while avoiding the sharp and spinny bits.

[[Cueball]] argues that this is unethical as it forces rare animals to put their lives at risk, and compares it to using police dogs for traffic control, which people would generally frown upon. {{Citation needed}}

[[Megan]] thinks both ideas (eagles and dogs) sound cool, but she understands the ethical argument against using them for traffic control.

[[Black hat]], on the other hand, goes a step further and says that he has created a drone that hunts the eagles. In the title text, he continues that is ethical because they (only the title text mentions that there are several of such drones) only target the most populous species first, although they will eventually eradicate the endangered ones once they bring down the number of all birds of prey. He seems to {{tvtropes|ComicallyMissingThePoint|miss the point}} that it is not merely the relative number of birds that creates the ethical problem, but the fact that animals' lives are being put at direct risk by humans.

==Transcript==

(Cueball, Black Hat and Megan are standing.)

Cueball: Everyone loves these eagles that take down drones, but ... I dunno.

Megan: You gotta admit, it's pretty cool.

(Close-up on Cueball's face)

Cueball: Yeah, but ... training rare animals to hurl themselves at whirling machinery can only get us so far, you know?

(Regular shot)

Cueball: At some point, it's like releasing police dogs onto highways to attack speeding motorcycles.

Megan: Also cool, but I see your point.

Black Hat: Plus, I just finished my autonomous drone that hunts eagles.

Cueball: Man, ''you'' are an entirely separate class of problem.

{{comic discussion}}

[[Category:Comics featuring Black Hat]]
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]