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Why is c the symbol for the speed of light? (1997)

math.ucr.edu

41–47 of 47 posts

Re: Why is c the symbol for the speed of light? (1997)

#41

> Weber apparently meant c to stand for "constant" in his force law, but there is evidence that physicists such as Lorentz and Einstein were accustomed to a common convention that c could be used as a variable for velocity. 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 pr…

All hail Weber’s Electrodynamics!

Re: Why is c the symbol for the speed of light? (1997)

#42

I always remember c as the c onstant speed of light [in a vacuum], but never pondered the actual origin beyond the perhaps rudimentary algebra “x, y, z are variables and a, b, c are constants”. I don’t think I thought c came from “constant”, because that’s a very English-centric view of science, but the annoying thing about reading a smart article like this is that it’s impossible to explore the depths of how your mi…

I think it would have been 'k' if it stood for "constant" since most of them were German-speakers or collaborating with them.

k was already in use as Boltzmann's constant by that time, I think:

https://en.wikipedia.org/wiki/Boltzmann_constant

Re: Why is c the symbol for the speed of light? (1997)

#43
post #7

> The same Latin root is found in more familiar words such as acceleration and even celebrity, a word used when fame comes quickly. According to the OED, celebrity comes from the Latin “celebritās, [the] state of being busy or crowded, festival, games or other celebration characterized by crowded conditions, reputation, renown, fame, frequency or commonness.” https://www.oed.com/dictionary/celebrity_n?tab=etymology#9…

Yeah, a celebrity is someone who is celebrated. The “quick rise to fame” explanation seem like a folk-etymology.

Re: Why is c the symbol for the speed of light? (1997)

#44
post #11

It is so, so refreshing to actually get an answer straight up instead of 6 paragraphs about the context, and how the author came to learn it, and what confusion might be, and how other constants have other names etc.

Right! Most articles I stumble upon nowadays is filled with everything besides the answer until I scroll to the bottom.

Modern web article on why c is used for speed of light:

"When Sonia returned to her apartment on a warm, New York summer evening, little did she expect that ... "

Re: Why is c the symbol for the speed of light? (1997)

#45
post #21
post #11

It is so, so refreshing to actually get an answer straight up instead of 6 paragraphs about the context, and how the author came to learn it, and what confusion might be, and how other constants have other names etc.

Its from 1997.

2004

Re: Why is c the symbol for the speed of light? (1997)

#46

> Weber apparently meant c to stand for "constant" in his force law, but there is evidence that physicists such as Lorentz and Einstein were accustomed to a common convention that c could be used as a variable for velocity. 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 pr…

> Although the c symbol was adapted from Weber's constant, it was probably thought appropriate for it to represent the velocity of light later on because of this Latin interpretation.

Why do you say that?

> So history provides an ambiguous answer to the question ...

You provide an ambiguous answer, with no evidence (unless I misunderstand). That's not history.

Re: Why is c the symbol for the speed of light? (1997)

#47
The use of "c" as the symbol for the speed of light can be traced back to the pioneering work of the French physicist Augustin-Jean Fresnel in the early 19th century.

In his research on light and optics, Fresnel used the letter "c" to represent the speed of light in his equations and formulas. The choice of "c" was likely influenced by the Latin word "celeritas" and its association with speed.

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