6 ms·
Why is C the symbol for the speed of light? (2004)
- kqr 2y agoI realise now I had probably only thought of c as a natural companion to v because of Qwerty keyboards...
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- madcaptenor 2y agoOkay, now why is m slope? I'd also wondered why r is the correlation coefficient but it turns out it's the "regression" coefficient, as in how strong the regression to the mean is.
- fuzzfactor 2y agoKind of reminds me of a mountain you're going to climb :)
- madcaptenor 2y agoFrom a bit of googling I see some people say it's from French "monter", meaning to climb, which does come from the same root as English "mountain".
- JdeBP 2y agoA lot of these conventions just develop according to what notation sticks, like how π caught on almost 3 millennia after the ratio was treated as a constant. And not all of them are even as universal as one might think. mx+c is not. Charles Hutton used y = ax + b for the equation of a "right line" in xyr 1811 A Course of Mathematics, for example.
- seba_dos1 2y agoI used y = ax + b all the time in school. This is the first time I encounter mx + c.
- anthk 2y agoFor a Basque speaker as me, m was ideal because malda in Basque means... slope :)
- Keyframe 2y agoOkay, now why is m slope? the great divide between US and Europe :D should be a - a, b, c, d... why m though, indeed?
- kqr 2y agoWait, is m slope? I learned it with k (for coefficient) for the slope, and m for the intercept (I don't know why m in that case though).
- xeonmc 2y agoCould also stand for Speed of Causality.
- Wistar 2y ago[flagged]
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- matt3210 2y agoBecause it’s the fastest programming language
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- silisili 2y agoYep but some are claiming this makes the speed of light incredibly unsafe and unpredictable. A small but loud group of scientists are working to replace c with a crab emoji in most literature going forward.
- benob 2y agoI definitely though of the programming language at first. Although the speed of light is a bit presumptuous to qualify the speed of C, I now wonder why every benchmark is against C, and not some other language.
- Someone 2y agoPartly because it is fairly fast, partly because, whatever you’re running your language on, chances are better that you can run a C compiler on it than that you can run most other languages.
- mike_ivanov 2y ago
- bregma 2y agoC is the Roman numeral representing 100. You can't go faster than 100% of the speed of light. QED.
- racl101 2y agoQuod Erat Demonstrandum.
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- jihadjihad 2y agoThat's celerious
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- Dwedit 2y agoYou need "C" to be the symbol for the speed of light to make the joke from Animanics work.
- hiccuphippo 2y agoThe one where they spell acme backwards?
- racl101 2y agoe m c α
- travisgriggs 2y agoLink? I was a big animaniacs fan, but not recalling this one.
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- havaloc 2y agoC you later?
- gnarlynarwhal42 2y agoCool to see a local school on here. Off-topic but their botanical gardens and Cactus/Desert garden is a really enjoyable afternoon.
- JdeBP 2y agoI wonder whether this is the Philip Gibbs that set up viXra.
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- zabzonk 2y agoA and B were already used. Somewhere.
- raverbashing 2y agoB non-ironically was (I guess) - it means magnetic field. A, no idea. Also might I add the speed of light is (lower-case) c, not C
- annodomini2019 2y agoWouldn't a have been used for acceleration?
- hehbot 2y agoMagnetic Vector Potential?
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- N7lo4nl34akaoSN 2y ago[flagged]
- pyuser583 2y agoIt wasn't the symbol for the speed of light, it was the symbol for the Lorenz Constant.
- poulpy123 2y ago[flagged]
- simonjanssen 2y agoSomewhat off-topic, but here's "A joke about measurement": https://www.youtube.com/watch?v=KmfdeWd0RMk https://www.youtube.com/watch?v=KmfdeWd0RMk
- wnissen 2y agoMy immediate guess based on no specific knowledge was “arbitrary constant while they were figuring things out” and it sounds like that’s not far from the truth. The process of discovery is often far more protracted than it seems when one is reading about it decades after the fact.
- DrNosferatu 2y ago_C_elerity?
- 762236 2y agoThe 'short version' is very well written and to the point. (I didn't read the long version, so my lack of comment on that isn't a criticism of it)
- Vox_Leone 2y ago"As for c, that is the speed of light in vacuum, and if you ask why c, the answer is that it is the initial letter of celeritas, the Latin word meaning speed." Isaac Asimov in "C for Celeritas (1959)" 'https://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/c.html https://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLig...
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- antirez 2y agoBecause of the language
- hangonhn 2y agoI was always taught that it stood for "constant", which is what the speed of light is in every frame of reference and I've never stopped to question it because it made sense. But it seems that usage actually predates Einstein according to the above article. It's interesting how a good story can be used to sell something that's not entirely true and I never stopped to question it.
- throw-qqqqq 2y ago> Why is C the symbol for the speed of light? Because C++ and Rust wasn’t invented when they formalized it! … I’ll see myself out
- fsckboy 2y ago>This usage can be traced back to the classic Latin texts in which c stood for "celeritas" meaning "speed". The uncommon English word "celerity" is still used when referring to the speed of wave propagation in fluids not to mention the more common "acceleration"
- froh 2y agoyes! and that is composite * "a-/ad-" towards * "celeritas" speed the second derivative, of sorts: towards+speed
- DiogenesKynikos 2y agoIndeed, and c_s ("c subscript s") is commonly used to denote the speed of sound.
- munificent 2y agoYes, the very next sentence in the article: The same Latin root is found in more familiar words such as acceleration and even celebrity, a word used when fame comes quickly.
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- tonymet 2y agoC is for "Cochranes", named after Zefram Cochrane
- AnonymousPlanet 2y agoI thought it was because C is fast (compared to most other languages)
- bee_rider 2y agoBut light is fast compared to all other things, not just most other things. It is the fastest thing. So, this can’t be it, otherwise Fortran would be traveling back in time… wait, is Fortran traveling back in time?
- awesome_dude 2y agoC is for cookies, and that's good enough for me!
- ck2 2y agoI always thought it was because it's not the speed of LIGHT It's the speed of causality But it still blows my mind the universe expands faster than C https://en.wikipedia.org/wiki/Cosmological_constant#/media/File:Lambda-Cold_Dark_Matter,_Accelerated_Expansion_of_the_Universe,_Big_Bang-Inflation.jpg https://en.wikipedia.org/wiki/Cosmological_constant#/media/F...
- formerly_proven 2y ago'cause you don't c it coming
- throwawayk7h 2y agoPlease fix the title, it's _c_, not _C_.
- idoubtit 2y agoI never understood the appeal of title case. It brings nothing valuable, but sometimes leads to stupid mistakes like this, or raises ambiguities that hamper my reading. I hope the American influence won't make this practice more common in British English. But it's not just about the country: The Washington Post has sane titles, like every British newspaper I've read, while The New York Times Has Elite Titles With Many Big Letters.
- mmooss 2y agoWhile I prefer the aesthetics of only an initial capital in the title, title case in prose helps us distinguish the title from the rest of the sentence.
- pepa65 2y agoThere are more suitable typographical techniques of accomplishing the same result.
- pezezin 2y agoI am glad to see that I am not the only one who thinks the same. My mother language doesn't use title case, maybe it's why I find it ugly. Another thing that I also find really annoying is using commas instead of "and" in headlines. It just makes reading them much harder for no obvious benefit.
- 9rx 2y agoTechnically it is the character with Unicode code point U+1D450. But HN arbitrarily removes it from the string upon submission, so, since we're approximating, C will do.
- xenadu02 2y agoc is technically the speed of causality. The speed at which perturbations in the fields that make up the universe propagate. The speed of light is a consequence of this, not the cause. Calling c the "speed of light" is putting the cart before the horse. Photons (being massless) have 100% of their velocity in the spatial dimensions and no velocity in the time dimension. They move at the maximum speed that any change in the electrostrongweak force can propagate in our universe because they are not free to do anything else. From a photon's POV a trip across the entire universe happens instantaneously - taking no time whatsoever.
- belter 2y ago> c is technically the speed of causality. How does this notion reconcile with seemingly instantaneous quantum phenomena like spooky action at a distance?
- jlawson 2y agoQuantum entanglement ("spooky action at a distance") doesn't allow for communication, so there's no causality between the particles.
- belter 2y agoThanks for the answer. I had forgotten about the No-communication theorem. This led me into another rabbit hole :-) of why c is 299,792,458 m/s and for example not 499,792,458 m/s or some other value, and the fundamental constants that bring this value. [1] Is there a current theory that tries to justify those constants that bring the current value of c ? Are those values the ones that must be, for the current Universe to be feasible? [1] https://arxiv.org/abs/hep-ph/0205340 https://arxiv.org/abs/hep-ph/0205340
- pixl97 2y agoI'm not sure if there is a good theory on why it ends up being this speed, but if any of the constants were even slightly different we wouldn't be in this universe to talk about it. https://en.wikipedia.org/wiki/Fine-tuned_universe https://en.wikipedia.org/wiki/Fine-tuned_universe
- rakoo 2y agoI've always learned that "speed" is something that can be used to describe an object aka something with mass. When something without mass travels (basically information) you use "celerity", because it's not talking about the "same" thing
- themaninthedark 2y agoI thought c stood for clock speed and that is how we know we are in a simulation.
- TZubiri 2y agoBecause god coded it on C
- Aardwolf 2y agoThought something similar, it's all because they wrote C instead of the actual c in the title
- borntoolate 2y agoBecause C++ is object oriented.
- DarkNova6 2y agoBecause C++ wasn't invented yet.
- anacrolix 2y agoc. Not C
- 9rx 2y agoNeither. It should be https://www.compart.com/en/unicode/U+1D450 https://www.compart.com/en/unicode/U+1D450 But HN is broken and the character disappears upon submission, so we have to approximate it with a symbol that looks similar. C is similar enough.
- nhatcher 2y agoPrevious discussion: https://news.ycombinator.com/item?id=36904892 https://news.ycombinator.com/item?id=36904892 (45 comments, 139 points)
- CHB0403085482 2y agoCelerity is the new FLASH villian? Haha.
- Surac 2y agoas a programmer I would answer: well c ist the fastes way to construct a complete bogus programm :)
- WaNumberLookup 2y agoAn interesting question : )
- smallmouth 2y agoIt is because light is the only part of the radiation spectrum you c.
- Suppafly 2y ago> Why is C the symbol for the speed of light? I'm not sure why that would be an interesting question. Sure it's probably constant or causality or something else, but really most mathematical symbols exist because someone wrote a paper using that symbol and other people adopted it.