6 ms·

I have no problem with people trying to do this in principle. I really don't care enough, but other people can. The symbol "tau", however, is an especially po

by amalcon 16y ago

I have no problem with people trying to do this in principle. I really don't care enough, but other people can. The symbol "tau", however, is an especially poor choice for a trigonometric symbol, because it's also used for torque. You won't get many physics teachers to change over if every time you try to calculate a torque from a force and radius, you run into a symbol conflict.

Groxx 16y ago
How many symbols aren't in use, though? If you've got a notably better one, the "manifesto" may consider changing, but they seem (to me) to have pretty good reasons for choosing tau.
- amalcon 16y ago
  I'd ideally prefer to pick one that isn't used in angular things. Because non-English, non-Greek glyphs are somewhat underused for this sort of thing, and because of visual similarity to pi, I'd suggest the hebrew Het or Russian л. However, I really have no problem with continuing to use the multi-glyph symbol 2pi.
  - samatman 16y ago
    Too much visual similarity to pi is a recipe for many factor-of-two errors.
  - vorg 16y ago
    Why a multi-glyph symbol 2π when a single-glyph symbol 2π would be better. By creating a new symbol by joining the bottom-right of the 2 to the topleft of the π, we can make a new one-glyph symbol, perhaps put it next to € in Unicode. And instead of saying two words "Two Pi", we could say it as one word "Twopi", with stress on the first syllable, much like the word "teenager" used to be spoken and written as two words a century ago.
    - Groxx 16y ago
      I like the idea of "Twopi". Looks like it could be pronounced like "Toupee". (yes, it'd be a mispronunciation, but people do that) Do you also favor the almighty interrobang‽
      - deleted 16y ago
        [deleted]
      - eru 16y ago
        We pronounce the constant as pee in German anyway. (No confusion with bodily fluids there.) Or we might as well go with dvapee (Russian), or tsveypee (German (zweipi, written so that you can pronounce it the English way and it'll come out ok)). We can go for pronouncing the thingy pipi. (Though would lead to confusion with bodily fluids in German.)
    - amalcon 16y ago
      You know, I really don't care that much about the 2pi thing, but this is just cool enough that I might be able to get behind it.
ScotterC 16y ago
My first thought exactly. Mechanical engineers and physicists appreciate where Tau is at the moment. But as someone notes, there is always symbol conflicts.
- techiferous 16y ago
  "at the moment" very funny ;)
mhartl 16y ago
I mention torque in the manifesto, but I wasn't specific enough in this case, and I've added an example addressing this issue at http://tauday.com/#sec:four_arguments http://tauday.com/#sec:four_arguments. The short version is that when necessary you can easily add a subscript to avoid ambiguity, such as tau_R for rotational torque. (Superscripts work, too. Particle physicists deal with pions, which are represented by the letter pi, but all the symbols have superscripts indicating their electric charge. As a result, no one ever confuses them with the number.)
- amalcon 16y ago
  The thing is, torque is a particularly bad thing to conflict with. While you're not using torque every time you work with pi, you usually end up using pi every time you work with torque. edit: It's much like using i for both sqrt(-1) and for current. Electrical engineers need to use both of these all the time, so they often use j for sqrt(-1) instead.
  - krschultz 16y ago
    Or you could use M for moment and stop using tau for torque. Most mechanical engineers talk about moments with M instead of tau.
    - amalcon 16y ago
      The electrical engineering thing demonstrates that you're unlikely to get a particular discipline to change its own notation. It would have made much more sense in retrospect to change current to something other than i, but that's not what happened.
      - nooneelse 16y ago
        As an electrical engineer (by way of physics and math), I'll use any other damn letter that makes sense for current that you want, and try to sway my fellows too. I just haven't seen a good option yet. What have you got? "c"... no good, speed of light for one; and also current needs good a good alteration for DC vs AC, "c" and "C" look too similar when written by someone else's hand (and "C" is crap in equations anyway since it can look too much like a "("). Current is a flow, but "f" is well used. Any good suggestions?
TheBurningOr 16y ago
I would argue though that the torque example is a particularly problematic symbol conflict as any equations involving torque are by definition going to include many, many references to the circle constant. Yes there are other symbol conflicts in math, but usually they are separated by logical fields (you generally are not doing using e when dealing with the charge of an electron constant (except in the case that you are dealing with magnitude of the electric field as a function of distance) and even when you are, it is hardly a problem because you never use the natural logarithmic constant except as a power function). I think the appropriate change here though would be to change the symbol for torque to say, 'q' or something. Probably not going to happen, but wouldn't be as much of an issue.
- samatman 16y ago
  I would suggest a change to uppercase Gamma, which looks like a T, kinda. Also, it has always struck me as a looking kind of like a moment arm. Something like this is bound to happen if mathematics pedagogy moves to tau as the circle constant, which it should. The math department has no motivation to respect physics convention, and the physics department will just have to get in line, eventually.
  - graywh 16y ago
    Or physicists/engineers will do their own thing, as seen by using j = sqrt(-1). Also, uppercase gamma is already used, too. http://en.wikipedia.org/wiki/Gamma_function http://en.wikipedia.org/wiki/Gamma_function
    - samatman 16y ago
      Granted, but interference with mechanical torque is unlikely. Greek letters are pretty polysemantic in the context of maths and physics.
jb55 16y ago
These arguments are assuming that tau would be a total replacement for pi in all situations. Why not just keep using pi in situations where you are doing calculations with torque?
- jacobolus 16y ago
  The point of tau (or pi) is to do calculations with angles. One of the main uses of angles in physics is calculations having to do with torque. Basically, using pi for calculations that might involve torque is giving away one of the situations where tau would be most useful.
mhartl 16y ago
This torque issue was really bothering me, and I finally realized why: I was pretty sure I'd already seen torque represented by a letter other than tau. Sure enough, I checked my copy of Introduction to Electrodynamics by David Griffiths, which is a popular (and truly great) intermediate E&M text, and there it was on p. 162: torque written as N = r X F. The same usage appears in several other places in that book, and Introduction to Electrodynamics is a standard text, so I'm confident that other sources use it as well. So we see that the idea of using a letter other than tau for torque is not some theoretical possibility—it has already happened, and in a standard textbook to boot. I've updated the manifesto with a note to this effect at http://tauday.com/#sec:four_arguments http://tauday.com/#sec:four_arguments. I realize that this may not convince you, but I urge you to reserve the right to change your mind about tau. After all, I changed my mind about pi. ;-)
- eru 16y ago
  And there are only so many letters in the alphabet(s). Although I have to admit common usage hasn't really exhausted the hebrew alphabet, yet. And when the Chinese finally take over, we will have enough short symbols to last us for millenia.
- Kadin 16y ago
  I remember vaguely from my time using Griffiths' book that he uses a lot of non-standard (or at least not the same as other, more introductory textbooks) notation. He pretty freely reassigns the symbols used by things that you're supposed to understand, in order to free them up for other purposes. Or at least that's my vague recollection. It's been a few years now since I've cracked open his Electrodynamics. It was a pretty decent book though, better than a lot of textbooks (I kept it and still have my edition around somewhere, something that I didn't do if I thought a textbook was crummy).
- amalcon 16y ago
  Interesting. N may not be such a great symbol to use for torque, because the equation relating it to force and radius is a cross-product. In that context, N often refers to a "normal" vector. Still, it's apparently in use somewhere, which is interesting.

by amalcon 16y ago

Groxx 16y ago

How many symbols aren't in use, though? If you've got a notably better one, the "manifesto" may consider changing, but they seem (to me) to have pretty good reasons for choosing tau.

amalcon 16y ago
I'd ideally prefer to pick one that isn't used in angular things. Because non-English, non-Greek glyphs are somewhat underused for this sort of thing, and because of visual similarity to pi, I'd suggest the hebrew Het or Russian л. However, I really have no problem with continuing to use the multi-glyph symbol 2pi.
- samatman 16y ago
  Too much visual similarity to pi is a recipe for many factor-of-two errors.
- vorg 16y ago
  Why a multi-glyph symbol 2π when a single-glyph symbol 2π would be better. By creating a new symbol by joining the bottom-right of the 2 to the topleft of the π, we can make a new one-glyph symbol, perhaps put it next to € in Unicode. And instead of saying two words "Two Pi", we could say it as one word "Twopi", with stress on the first syllable, much like the word "teenager" used to be spoken and written as two words a century ago.
  - Groxx 16y ago
    I like the idea of "Twopi". Looks like it could be pronounced like "Toupee". (yes, it'd be a mispronunciation, but people do that) Do you also favor the almighty interrobang‽
    - deleted 16y ago
      [deleted]
    - eru 16y ago
      We pronounce the constant as pee in German anyway. (No confusion with bodily fluids there.) Or we might as well go with dvapee (Russian), or tsveypee (German (zweipi, written so that you can pronounce it the English way and it'll come out ok)). We can go for pronouncing the thingy pipi. (Though would lead to confusion with bodily fluids in German.)
  - amalcon 16y ago
    You know, I really don't care that much about the 2pi thing, but this is just cool enough that I might be able to get behind it.

ScotterC 16y ago

My first thought exactly. Mechanical engineers and physicists appreciate where Tau is at the moment. But as someone notes, there is always symbol conflicts.

techiferous 16y ago
"at the moment" very funny ;)

mhartl 16y ago

I mention torque in the manifesto, but I wasn't specific enough in this case, and I've added an example addressing this issue at http://tauday.com/#sec:four_arguments http://tauday.com/#sec:four_arguments. The short version is that when necessary you can easily add a subscript to avoid ambiguity, such as tau_R for rotational torque. (Superscripts work, too. Particle physicists deal with pions, which are represented by the letter pi, but all the symbols have superscripts indicating their electric charge. As a result, no one ever confuses them with the number.)

amalcon 16y ago
The thing is, torque is a particularly bad thing to conflict with. While you're not using torque every time you work with pi, you usually end up using pi every time you work with torque. edit: It's much like using i for both sqrt(-1) and for current. Electrical engineers need to use both of these all the time, so they often use j for sqrt(-1) instead.
- krschultz 16y ago
  Or you could use M for moment and stop using tau for torque. Most mechanical engineers talk about moments with M instead of tau.
  - amalcon 16y ago
    The electrical engineering thing demonstrates that you're unlikely to get a particular discipline to change its own notation. It would have made much more sense in retrospect to change current to something other than i, but that's not what happened.
    - nooneelse 16y ago
      As an electrical engineer (by way of physics and math), I'll use any other damn letter that makes sense for current that you want, and try to sway my fellows too. I just haven't seen a good option yet. What have you got? "c"... no good, speed of light for one; and also current needs good a good alteration for DC vs AC, "c" and "C" look too similar when written by someone else's hand (and "C" is crap in equations anyway since it can look too much like a "("). Current is a flow, but "f" is well used. Any good suggestions?

TheBurningOr 16y ago

I would argue though that the torque example is a particularly problematic symbol conflict as any equations involving torque are by definition going to include many, many references to the circle constant. Yes there are other symbol conflicts in math, but usually they are separated by logical fields (you generally are not doing using e when dealing with the charge of an electron constant (except in the case that you are dealing with magnitude of the electric field as a function of distance) and even when you are, it is hardly a problem because you never use the natural logarithmic constant except as a power function). I think the appropriate change here though would be to change the symbol for torque to say, 'q' or something. Probably not going to happen, but wouldn't be as much of an issue.

samatman 16y ago
I would suggest a change to uppercase Gamma, which looks like a T, kinda. Also, it has always struck me as a looking kind of like a moment arm. Something like this is bound to happen if mathematics pedagogy moves to tau as the circle constant, which it should. The math department has no motivation to respect physics convention, and the physics department will just have to get in line, eventually.
- graywh 16y ago
  Or physicists/engineers will do their own thing, as seen by using j = sqrt(-1). Also, uppercase gamma is already used, too. http://en.wikipedia.org/wiki/Gamma_function http://en.wikipedia.org/wiki/Gamma_function
  - samatman 16y ago
    Granted, but interference with mechanical torque is unlikely. Greek letters are pretty polysemantic in the context of maths and physics.

jb55 16y ago

These arguments are assuming that tau would be a total replacement for pi in all situations. Why not just keep using pi in situations where you are doing calculations with torque?

jacobolus 16y ago
The point of tau (or pi) is to do calculations with angles. One of the main uses of angles in physics is calculations having to do with torque. Basically, using pi for calculations that might involve torque is giving away one of the situations where tau would be most useful.

mhartl 16y ago

This torque issue was really bothering me, and I finally realized why: I was pretty sure I'd already seen torque represented by a letter other than tau. Sure enough, I checked my copy of Introduction to Electrodynamics by David Griffiths, which is a popular (and truly great) intermediate E&M text, and there it was on p. 162: torque written as N = r X F. The same usage appears in several other places in that book, and Introduction to Electrodynamics is a standard text, so I'm confident that other sources use it as well. So we see that the idea of using a letter other than tau for torque is not some theoretical possibility—it has already happened, and in a standard textbook to boot. I've updated the manifesto with a note to this effect at http://tauday.com/#sec:four_arguments http://tauday.com/#sec:four_arguments. I realize that this may not convince you, but I urge you to reserve the right to change your mind about tau. After all, I changed my mind about pi. ;-)

eru 16y ago
And there are only so many letters in the alphabet(s). Although I have to admit common usage hasn't really exhausted the hebrew alphabet, yet. And when the Chinese finally take over, we will have enough short symbols to last us for millenia.
Kadin 16y ago
I remember vaguely from my time using Griffiths' book that he uses a lot of non-standard (or at least not the same as other, more introductory textbooks) notation. He pretty freely reassigns the symbols used by things that you're supposed to understand, in order to free them up for other purposes. Or at least that's my vague recollection. It's been a few years now since I've cracked open his Electrodynamics. It was a pretty decent book though, better than a lot of textbooks (I kept it and still have my edition around somewhere, something that I didn't do if I thought a textbook was crummy).
amalcon 16y ago
Interesting. N may not be such a great symbol to use for torque, because the equation relating it to force and radius is a cross-product. In that context, N often refers to a "normal" vector. Still, it's apparently in use somewhere, which is interesting.