273: Electromagnetic Spectrum

Explain xkcd: It's 'cause you're dumb.
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Electromagnetic Spectrum
Sometimes I try to picture what everything would look like if the whole spectrum were compressed into the visible spectrum.  Also sometimes I try to picture your sister naked.
Title text: Sometimes I try to picture what everything would look like if the whole spectrum were compressed into the visible spectrum. Also sometimes I try to picture your sister naked.


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Please include the reason why this explanation is incomplete, like this: {{incomplete|reason}}

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This is a play on the Electromagnetic Spectrum where it shows a large piece of the spectrum and what each wavelength/frequency corresponds to. The first two scales at the bottom show the wavelength λ (in Meters) and the frequency f (in Hertz). Both values are related as λ=c/f, where c is the speed of light. The last line showing Q(Gal²/Coloumb) is just nonsense, Cal could be Gallon and Coloumb is maybe a typo for Coulomb.

In 1887 the Michelson–Morley experiment proved for the first time that the aether theory was wrong. The year 1897 must be a typo by Randall. Nevertheless, after that time many physicists like Hendrik Lorentz or Joseph Larmor were still working on some aether theories, it was solved to an "non-aether" theory by Albert Einsteins theory of Special Relativity in 1905.

The comic in detail

The wavelength starts at high values on the left and decreasing in a logarithmic scale to the right. Because f=c/λ the frequency is starting at low values and increasing in a logarithmic scale.

Power and Telephone

  • Slinky waves by a coil
  • The human audio spectrum (from 20Hz to 20KHz). The "high-pitched noise in empty rooms" refers to tinnitus.
  • The "wave" in a stadium.
  • CIA (Secret) is a joke about all the wiretapping on phones and more.

Radio and TV

  • "Shouting car dealership commercials" is a pun to all the massive advertising on cars.
  • HAM radio is a private amateur radio used for communication. "Kosher radio" is playing with ambiguousness of the word HAM. Kosher is a Jewish law for food.
  • Some frequencies of famous broadcast stations.
  • The rays controlling Steve Ballmer are just nonsense. The real Balmer series does belong to visible and ultraviolet light.
  • AM Amplitude modulation, VHF Very high frequency, and UHF Ultra high frequency are frequency ranges approved to commercial broadcasting companies.
  • Cell phone cancer rays is playing with the belief of many people that cell phones may cause cancer (see also 925: Cell Phones).
  • Aliens belong to a range slightly higher than the frequencies used by human communications. So they can't hear us.


  • SETI is the "Search for ExtraTerrestrial Intelligence" project trying to find messages from aliens. Since aliens working at different frequencies there is still no result.
  • WIFI is the standard for wireless computer communications.
  • FHF is maybe "Fulminant high frequency", it just does not exit.
  • Gravity waves belong to fluid dynamics, do not mix it up with Gravitational wave.
  • Brain waves could be a reference to Neural oscillation.
  • Sulawesi is just an island in the Indian Ocean and belonging to Indonesia.


  • This is just a pun to microwaves, no entry is at this frequency range.

IR (infrared)

Visible light

  • At the bottom it is split into "visible light" and "visible dark", of course darkness is not visible.
  • The human visible spectrum is shown by all colors, including octarine, the colour of magic on the Discworld.
  • On top there are two absorption spectra, Hydrogen and Helium. This most common elements at our sun do block some small frequencies from the light the sun does emit.
  • Depends is a brand of underwear for adults experiencing urinary or fecal incontinence. The color is consequently yellow.
  • Tampax is a brand of tampon. The color is red.

UV (ultraviolet)

  • Ultraviolet light can not be seen by humans but it causes out tan. No entries here.

Miller light

Empty section

  • "Main Death Star Laser" is just a reference to Star Wars.

Censored under Patriot Act

  • No entry because it's censored.


Gamma/Cosmic rays


[Everything is one big panel.]
The Electromagnetic Spectrum
These waves travel through the electromagnetic field. They were formerly carried by the aether, which was decommissioned in 1897 due to budget cuts.
Other waves:
  • Slinky waves [Cueball and Megan hold the ends of a tangled slinky.]
  • Sound waves [There is a snippet of a frequency band. Between 20 Hz and 20 KHz is labeled "Audible Sound." Towards the top is a line labeled "That high-pitched noise in empty rooms."]
  • The wave [A row of people does a wave.]
[Three parallel scales are across the bottom. The first is lambda (m), ranging from 100Mm to 100fm; second is f (Hz), which starts at 1 Hz and reaches 100 THz about 2/3 of the way along, after which the labels read "other entertaining greek prefixes like peta- exa- and zappa-"; last is Q (Gal^2/Coloumb), whose labels are 17, 117, pi, 17, 42, theta, e^pi-pi, -2, 540^50, and 11^2. Above the scales and lined up accurately with the first two are the following:]
  • Power & Telephone (100Mm to 1km)
  • Radio & TV (1km to somewhere between 1m and 10cm); above that are many boxes showing subranges (AM, VHF, UHF, 14/7 NPR pledge drives, a very thin band for the space rays controlling Steve Ballmer, 99.3 "The Fox," 101.5 "The Badger," 106.3 "The Frightened Squirrel," cell phone cancer rays, CIA, ham radio, kosher radio, shouting car dealership commercials.)
  • Microwaves (a bit more than 10cm to a bit more than 1mm); it also has subranges (aliens, just below SETI, wifi, FHF, brain waves, sulawesi, gravity)
  • Toasters (about 1mm to about 100 micrometers)
  • IR (about 100 micrometers to somewhere between 1 micrometer and 1 nm); above that is a bell graph labeled "Superman"s heat vision," with a motorcycle driving up the left side labeled "Jack Black's Heat Vision."
  • Visible light (and, under it, visible dark); above that is a bell graph labeled "sunlight." There's a breakout chart above it showing the visible spectrum from 700nm (red) to 450nm (violet). There's an arrow pointing to where octarine would be, somewhere off to the side. Above that are bars showing the absorption spectra for hydrogen, helium, Depends(R) (yellow only) and Tampax(R) (red only).
  • UV (about 100nm to about 10nm)
  • Miller Light (a thin bar around 10nm)
  • An unlabeled section with a thin line above it showing the frequency of the main death star laser
  • A blocked-off portion labeled "Censored Under Patriot Act."
  • X-rays (from about 1nm to about 10pm); a line above shows the frequency of mail-order x-ray glasses. Somewhere vaguely above the 10pm mark is a potato.
  • Gamma/cosmic rays (10pm and smaller); above that is a bar marked Sinister Google Projects which also trails off into higher frequencies, and blogorays, which are slightly lower.

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"Light particles were formerly carried by the aether, which was decommissioned in 1897 due to budget cuts." Ohh, this is so INCOMPLETE, just read the comic, I still laughing and I can't stop. --Dgbrt (talk) 18:20, 6 July 2013 (UTC)

Now why did Randall Munroe go with the old 1960s notion of putting gamma/cosmic rays at the high end of the spectrum. Back then certain events in detectors were thought to be caused by photons of higher frequency than gamma rays, but now those are known to instead be made by very energetic charged nuclei not electromagnetism. Thus "cosmic rays" not part of EM spectrum at all. --RalphSiegler (talk) 15:07, 7 July 2013 (UTC)

Any help here is welcome!

...but please discuss major changes here before. The page is still marked as incomplete, I am happy about any new ideas.--Dgbrt (talk) 21:42, 15 July 2013 (UTC)

Going forward, I'll assume Wikipedia's "Be bold" guideline applies to this wiki (although not part of the wikimedia project), too. Thus, I'll continue to make changes I consider uncontroversial without first discussing them, if I'm sufficiently confident in them, including major ones. In judging how controversial a potential change might be, I'll take the respective article's edit history and talk page into account. I try to write good edit summaries, so these should usually give you my reason or motivation for making the edit it question. If you revert them, please do tell why you disagree with the specific edit (except that is hasn't previously been discussed) in the edit summary or on the talk page, so that a discussion can actually start.
--Das-g (talk) 12:49, 6 August 2013 (UTC)
Some suggestions
  • The year 1897 might refer to Joseph Larmor's publication about the later so-called Lorentz transformation.
  • "The Wave" might also refer to the experiment/novel.
  • The actual electromagnetic spectrum of toasters is (mostly) in the IR range.
  • I'm pretty sure there is some kind of joke w.r.t censorship and the Patriot Act (afaik the Patriot Act is actually more the opposite of censoring, though i.e. making more information available—to intelligence agencies)
  • I agree with User:Das-g that X-Ray glasses unlikely refer to full-body scanners

--Chtz (talk) 00:23, 16 July 2013 (UTC)

Mail-order X-Ray glasses

I doubt "mail-order X-Ray glasses" is a reference to full body scanners, for the following two reasons:

  1. Full body scanners are heavy and bulky equipment. While —if you'd manage to order one— you can probably have it shipped to a destination of your choice, delivery will most likely not happen by mail, which would be the definition of a mail order.
  2. While it might be possible to connect certain VR goggles or similar glasses-like periphery to some full body scanners, they are usually operated with screens that do not resemble spectacles.

In my opinion, it's much more likely that a once popular a novelty item that could actually be ordered from catalogues/adverts and could sent by mail (because it was flat and light, consisting of cardboard and plastic foil) is being referenced.
-- Das-g (talk) 21:34, 29 July 2013 (UTC)

It's been a week and there have not been any replies, so if there still aren't any for another week (i.e. until 2013-08-13) I'll consider my first change to this article undisputed and re-do it. However, I will not re-do my second change without explicitly putting it up for discussion here on the talk page, first, as I expect it to be a bit more controversial. (I'll put the second change up for discussion if/when I re-do the first change, as the second only makes sense if the first is acceptable, anyway.)
--Das-g (talk) 12:08, 6 August 2013 (UTC)
Because there still weren't any replies, I've redone my first change.
--Das-g (talk) 22:30, 13 August 2013 (UTC)
X-ray glasses and your sister

Is the second sentence of the title text ("Also sometimes I try to picture your sister naked.") a reference to how X-Ray Specs were sometimes advertized?
--Das-g (talk) 22:30, 13 August 2013 (UTC)

"Gal" could refer to 1cm/s2, or a galileo. http://en.wikipedia.org/wiki/Gal_%28unit%29173.245.56.208 05:34, 12 January 2015 (UTC)

Regarding the reference to microwave ovens in the explanation, I would like to point out that comic 843:Misconceptions references the list of common misconceptions, which in the Food and Cooking section clearly states that microwaves don't work at the frequency of water but instead uses dialectric heating to cook food. Obviously that comic is later than this one, but it should be considered for the explanation above. Thanks! GeniusBooks (talk)


I think that Sulawesi is a reference to 256: Online Communities (and 802: Online Communities 2). In all cases it is an item that does not really fit in (although in the Online Communities case the relationship to the rest of the drawing is quite obvious, with Sulawesi being the only real island among a set of fictional islands)-- 22:04, 21 November 2015 (UTC)