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Paolo de Leva submitted this long posting while my moderator's message was
still being processed, so it would be cruel not to distribute it. Paolo
always has a great multicultural and historical perspective.
But please, no more after this.
--
Ton van den Bogert, Biomch-L co-moderator
http://www.Biomch-L.org
> -----Original Message-----
> From: Paolo de Leva [mailto
aolo.deleva@tiscalinet.it]
> Sent: Thursday, November 08, 2007 4:04 PM
> To: BIOMCH-L
> Subject: R: Torque or moment about a joint
>
> Dear subscribers,
>
> Ton van den Bogert is right: "it would be great if we could
> agree on this".
> However, in this case we have two separate and widely
> accepted standards.
> Standards, not opinions. There has been a widely known
> precedent: SI (Systeme International d'Unites) versus the
> British system. Forgive me for the lack of detail (I am
> swamped of work right now):
>
> 1) The SI was born in the 18th century; its mother was the
> French revolution, it became adult in the late 20th century.
>
> 2) Today it is not yet completely accepted in US, but it
> will. May be in 10, 50, 100 or more years, but it will.
> Indeed, nobody can honestly deny that the SI is the best
> system, not even those who keep using a different system.
> They do so just because they are used to. The change is too
> expensive for
> them: a desired good that they cannot afford to buy.
>
> 3) I am not going to compare BIOMCH-L with the France of the
> 18th century.
> This is not the point.
>
> 4) The point is that "torque" versus "momentum" is a war that
> nobody can win. Both standards have strong weaknesses! (see
> for instance the etymological notes in my previous messages).
>
> 5) To win a war, a third, less questionable name is probably
> needed. For
> instance:
>
> - "rotor" (if John Paul says that a torque produces only torsion,
> please indulge me and let me say that a rotor can produce any
> kind of rotation :-), or
> - "angular force" or "rotational force", as opposed to "(linear)
> force" (notice that Joseph Louis Lagrange introduced in the
> late 18th century the "generalized force", 6 numbers including
> force and force moment).
>
> 6) Too many students learn physics in USA, or studying
> textbooks written by US physicists (including international
> students). The influence of USA universities on the
> scientific community is terrific.
>
> 7) Do we know how many scientists (not only biomechanists)
> are used to use or chose to use the word torque as a synonym
> of moment in their studies (including physicists)?
>
> 8a) I suspect that "moment" was the word initially used by
> everybody. My guess is that "Torque" was adopted by
> physicists (probably stealing it from
> engineers) to substitute moment, because they did not like
> the aspecificity and ambiguity of the word "moment" (it comes
> from "movimentum", it also means "instant"; what has that got
> to do with rotation?). This change was intentional, not casual.
>
> 8b) There was also another change, which is probably related:
> Newton called "quantity of motion" the quantity that we now
> call (in English) "linear momentum" (Italian: "quantità di
> moto"; Spanish: "cantidad de movimiento").
> And "moment of the quantity of motion" the quantity that we
> now call "angular momentum". Not difficult to imagine that
> the change was welcome!
> Again "quantity of motion" is too generic. As you see, the
> rationale is similar.
>
> 9) Notice that the SI prescribes the name of the unit
> ("Newton metre"), but as far as I know it does not give a
> preference about the name of the quantity ("moment of force"
> or "torque").
>
> 10) An optimistic observation: at least this is not a very
> expensive change.
> A new non-questionable name for this quantity may be accepted
> faster than the whole SI. There is no need of a revolution.
>
> 11) Pessimistic: possibly, other terminological "fixes" are
> needed in other chapters of physics. They won't accept a
> change in a single word, if other questionable words exist. A
> representative international committee (ISO) is the only
> organization that can solve this problem. And most likely,
> the committee will be mainly composed of physicists.
>
> In short: it does not matter if we agree on using the word
> "moment". We are not going to convince the other half of the
> word. Terminology evolves, but changes are expensive and
> nobody will ever accept questionable changes.
> Etymologically, "moment" is a questionable word. Moreover, I
> suppose that the river of history is flowing in the opposite
> direction! We are just advocating a return to the past. We
> are not starting a revolution, but resisting against a
> revolution started a long ago.
>
> With kind regards,
>
> Paolo de Leva
still being processed, so it would be cruel not to distribute it. Paolo
always has a great multicultural and historical perspective.
But please, no more after this.
--
Ton van den Bogert, Biomch-L co-moderator
http://www.Biomch-L.org
> -----Original Message-----
> From: Paolo de Leva [mailto
aolo.deleva@tiscalinet.it]> Sent: Thursday, November 08, 2007 4:04 PM
> To: BIOMCH-L
> Subject: R: Torque or moment about a joint
>
> Dear subscribers,
>
> Ton van den Bogert is right: "it would be great if we could
> agree on this".
> However, in this case we have two separate and widely
> accepted standards.
> Standards, not opinions. There has been a widely known
> precedent: SI (Systeme International d'Unites) versus the
> British system. Forgive me for the lack of detail (I am
> swamped of work right now):
>
> 1) The SI was born in the 18th century; its mother was the
> French revolution, it became adult in the late 20th century.
>
> 2) Today it is not yet completely accepted in US, but it
> will. May be in 10, 50, 100 or more years, but it will.
> Indeed, nobody can honestly deny that the SI is the best
> system, not even those who keep using a different system.
> They do so just because they are used to. The change is too
> expensive for
> them: a desired good that they cannot afford to buy.
>
> 3) I am not going to compare BIOMCH-L with the France of the
> 18th century.
> This is not the point.
>
> 4) The point is that "torque" versus "momentum" is a war that
> nobody can win. Both standards have strong weaknesses! (see
> for instance the etymological notes in my previous messages).
>
> 5) To win a war, a third, less questionable name is probably
> needed. For
> instance:
>
> - "rotor" (if John Paul says that a torque produces only torsion,
> please indulge me and let me say that a rotor can produce any
> kind of rotation :-), or
> - "angular force" or "rotational force", as opposed to "(linear)
> force" (notice that Joseph Louis Lagrange introduced in the
> late 18th century the "generalized force", 6 numbers including
> force and force moment).
>
> 6) Too many students learn physics in USA, or studying
> textbooks written by US physicists (including international
> students). The influence of USA universities on the
> scientific community is terrific.
>
> 7) Do we know how many scientists (not only biomechanists)
> are used to use or chose to use the word torque as a synonym
> of moment in their studies (including physicists)?
>
> 8a) I suspect that "moment" was the word initially used by
> everybody. My guess is that "Torque" was adopted by
> physicists (probably stealing it from
> engineers) to substitute moment, because they did not like
> the aspecificity and ambiguity of the word "moment" (it comes
> from "movimentum", it also means "instant"; what has that got
> to do with rotation?). This change was intentional, not casual.
>
> 8b) There was also another change, which is probably related:
> Newton called "quantity of motion" the quantity that we now
> call (in English) "linear momentum" (Italian: "quantità di
> moto"; Spanish: "cantidad de movimiento").
> And "moment of the quantity of motion" the quantity that we
> now call "angular momentum". Not difficult to imagine that
> the change was welcome!
> Again "quantity of motion" is too generic. As you see, the
> rationale is similar.
>
> 9) Notice that the SI prescribes the name of the unit
> ("Newton metre"), but as far as I know it does not give a
> preference about the name of the quantity ("moment of force"
> or "torque").
>
> 10) An optimistic observation: at least this is not a very
> expensive change.
> A new non-questionable name for this quantity may be accepted
> faster than the whole SI. There is no need of a revolution.
>
> 11) Pessimistic: possibly, other terminological "fixes" are
> needed in other chapters of physics. They won't accept a
> change in a single word, if other questionable words exist. A
> representative international committee (ISO) is the only
> organization that can solve this problem. And most likely,
> the committee will be mainly composed of physicists.
>
> In short: it does not matter if we agree on using the word
> "moment". We are not going to convince the other half of the
> word. Terminology evolves, but changes are expensive and
> nobody will ever accept questionable changes.
> Etymologically, "moment" is a questionable word. Moreover, I
> suppose that the river of history is flowing in the opposite
> direction! We are just advocating a return to the past. We
> are not starting a revolution, but resisting against a
> revolution started a long ago.
>
> With kind regards,
>
> Paolo de Leva