# Milestone-Proposal talk:GiovanniGiorgi

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## Comments on proposal -- Rich (talk) 19:03, 12 March 2019 (UTC)

### Introduction

I have read the proposal, Docket #:2018-05, carefully and agree that Giovanni Giorgi was essential to the development of what is now known as the International System of Units (SI). My detailed comments follow.

### Exposition

The SI was formally created in 1960 by the 11th General Conference on Weights and Measures (CGPM). As then proposed, the SI had six base units, the ones that concern us here are the meter (m), the kilogram (kg), the second (s), and the ampere (A). Giorgi's essential contribution was to show that by adding one base unit of an electrical nature (the choice of the CGPM was the ampere), the resulting MKSA system could be made coherent. In this case, coherent means that relations between the units follow the relations of physics with no additional numerical factors needed. For instance, the quotient of electrical tension and resistance must equal a current according to Ohm's law. The units in which these quatities are measured reflect the scientific relation, so that A = V/Ω ). That is simple enough. However, constructing a coherent system that included mechanical units was problematic. For instance, electrical power in a coherent system of electrical units, the watt (W), is obviously given by W=V·A. But the unit of power in the cgs system of units that was widely used at the time is the erg, which is orders of magnitude different from the watt used by electrical engineers. Maxwell had suggested that the cgs system could be made coherent with the engineering system of electrical units if the length of the centimeter was increased by a factor of 10^{9} and the mass of the gram was decreased by a factor of 10^{-11}. Maxwell called this the QES system and he didn't really recommend it.

But Giorgi found a way. His solution has two components. The first was to find a system of mechanical units, different from the cgs but nevertheless practical (unlike the QES). By chance, the MKS system would serve his purposes. This was a boon to the International Bureau of Weights and Measures (BIPM) because the defining artefacts of the meter and kilogram had been sanctioned by the CGPM in 1889, with the BIPM having responsibility for conserving these primary standards and providing copies to countries who desired them. But Giorgi's solution required a second component. To use the MKS system for the mechanical units, the magnetic constant (magnetic permeability of vacuum) and the electric constant (the electric permittivity of vacuum) were given values whose numerical components were far from 1 and which also had units. We now take this for granted, e.g. the magnetic constant is *μ*_{0}=4π×10^{-7} henries per meter (identical to the unit newtons per ampere squared); but this was controversial at the time. (Of course the two constants are not independent since their product bears an exact relation to the speed of light, but this was well known.)

### This reviewer's appreciation of Giorgi's most seminal contributions

So Giorgi's contribution was essential and led to the International System of Units, the system that incorporates the engineering units first used by telegraph engineers with the mechanical units of length, mass, and time. Giorgi's solution also eliminated the need for two separate electrical systems, then in use--the cgs-emu system and the cgs-esu system, since these were now combined in a single system.

As the proposers of the Milestone emphasize, Giorgi was a keen advocate of a "rationalized" system of electrical units and had an interesting epistolary exchange on this subject with Oliver Heaviside. However, this was a side issue for the SI and it was even suggested at a preliminary stage that the user could decide whether to use electromagnetic equations that are rationalized or not, because the same results could be obtained. Nevertheless, the final decision was to adopt rationalized equations for use with the SI, and this gives Maxwell's equations the look that they have today--i.e. the absence of any factor of 4π.

The proposers have done a good job of setting out the above issues and showing the historical influence of Giorgi's ideas. I strongly support this Milestone initiative.

### Final remarks

I would now like to comment on the proposers' selection of Supporting materials. I understand that they may have chosen Arthur Kennelly's paper in the *Proceedings of the National Academy of Science* because it is freely available. This is a fine paper and it belongs in the list of Supporting materials. But Kennelly's paper written the same year and published in Transactions of the American Institute of Electronical and Electronic Engineers (merged with IRE in 1962 to become the IEEE) is far more complete and even quite brilliant in its own right, containing much historical context and including a section on "Advantages of the Giorgi System to Students of Electrical Engineering".
This paper is now available from *IEEExplore* but it is not (yet) on open access. It is my strong suggestion that this paper be made available on open access by IEEE in honor of the Milestone now under consideration, and which I strongly support. The paper in question is:
A.E. Kennelly, "I.E.C. Adopts MKS System of Units", *Transactions of the American Institute of Electrical Engineers* ( Volume: **54** , Issue: 12 , Dec. 1935 ) 1373-1384.
doi: 10.1109/T-AIEE.1935.5056934

## Advocate's Statement by Michael P. Polis History Committee Member -- Polismpp1125 (talk) 14:01, 31 May 2019 (UTC)

have been tasked with overseeing the examination of this Milestone proposal (See the Wiki http://ieeemilestones.ethw.org/Milestone-Proposal:GiovanniGiorgi ), and hopefully its final approval.

As a starting point, in evaluating this proposal I have asked two experts, external to the History Committee, recommended by the volunteer Milestones Coordinator and IEEE Histroy Committee Research Coordinator, to assess this submission. The first expert, Professor Alessandro Ferrero, from Politecnico di Milano, Milan, Italy wrote: "I’m fully in favor of this milestone proposal. Giovanni Giorgi represented an important figure in the development of the electrical engineering and in the definition of the system of units. As correctly mentioned in the proposal, he developed the so-called rational theory of electricity, in which he proved, in a very strict and scientifically sound way that the equation of electromagnetism, including Maxwell’s ones, could become effective and unambiguous only if an electrical unit was added to the three fundamental units approved as a consequence of the Meter Convention. He clearly stated that the choice of this unit was arbitrary (it could be the elementary charge unit, the current unit, the voltage unit or the resistance unit) but it was absolutely needed. His preference went to the ampere (unit of current) only because, at that time, the experiment based on the Biot-Savart law appeared to be the only one who allowed the practical implementation of the unit with good accuracy. Nowadays, we know that this is not longer the case, and the recently redefined SI recognizes this. Let me add that the present redefinition of the SI is once again much in debt with Giorgi’s proposal. Indeed the watt (or Kibble) balance experiment, used to relate the kilogram to the Planck constant was originally conceived as an improvement of the ampere balance, that is as an improvement of the experiment used to implement the practical realization of the ampere. As you can see, there is still a lot of Giorgi in the present SI!"

The second expert, Richard Davis, Ph.D.. Emeritus Principal Research Physicist & Consultant, Bureau International des Poids et Mesures/ International Bureau of Weights and Measures, whose complete comments can be found under Comments on proposal -- Rich (talk) 19:03, 12 March 2019 (UTC) on the Wiki wrote: "So Giorgi's contribution was essential and led to the International System of Units, the system that incorporates the engineering units first used by telegraph engineers with the mechanical units of length, mass, and time. Giorgi's solution also eliminated the need for two separate electrical systems, then in use--the cgs-emu system and the cgs-esu system, since these were now combined in a single system."..."The proposers have done a good job of setting out the above issues and showing the historical influence of Giorgi's ideas. I strongly support this Milestone initiative."

1) The Technical Field of the Proposal: Giorgi's rational system of units was at the origin of the SI system of units. The SI System of Units is so broad that it covers all fields of science and engineering.

2) Is the proposal for an achievement rather than for a person? The achievement is the rational system of units that was first proposed in 1901 in Rome by Giovanni Giorgi, a Professor at the University of Rome. His proposal rationalized the equations of electromagnetism and added a fourth unit, electrical in nature, to the three mechanical units of measurements (meter, kilogram, second). His proposal was at the origin of the International System of units (SI) currently used and also called the “Giorgi system”.

3) Does the location being proposed for the milestone plaque have a direct and logical connection with the work (e.g. where the achievement was developed, tested, demonstrated, or installed)? The proposers must supply a copy of a letter of permission from the site owner allowing the mounting of a plaque before the proposal can be submitted. Is the location truly publicly-accessible? The proposed plaque site is the ground floor entrance hall of "La Sapienza" University of Rome, Italy, Faculty of Civil and Industrial Engineering. This site is directly connected to Gorgi who was on the faculty of the University of Rome when he proposed the system of units. The entrance hall is publicly accessible and a letter of permission has been received from the University.

4) Can the plaque site physically support the weight of the plaque? Is there space to fit the plaque’s dimensions? Yes, there are already other historical markers at the site.

5) Is there an IEEE organizational unit(s) willing to sponsor the milestone? This milestone is sponsored by the IEEE Italy Section.

6) Is the work truly a significant achievement vs. an incremental improvement to an existing technology? This was a major improvement over the previous efforts at a standard system of units. As stated in the proposal "The mechanical-centered vision of physics, dominant for nearly all of the 19th century, implied that all the physical phenomena could be explained by the fundamental concepts of mechanics: mass, length and time. ... in this way, all the electromagnetic units had to be derived from the mechanical ones in a rather awkward way... Giorgi’s fundamental achievement was that the group of units more used in practice — those of resistance, capacity, intensity of electric current, difference of potential, and inductance — is fully determined by just one of them taken as fundamental, plus the two units of work and time, the choice being independent from the units of length and mass provided that the electrical and mechanical powers are both to be measured in watts".

7) Were there prior or contemporary achievements of a similar nature? If so, what sets this achievement off from them? Other systems of units were used or proposed prior to the SI system, however,as stated in the proposal, "in every proposed system, some of the units were too large or too small for practical purposes, ... all the systems of units in use were still built on the three fundamental mechanical units of length, mass, and time. All this was solved by Giorgi with his proposal of taking a fourth fundamental unit, electric in nature, so that (the required constants) become fixed in value".

8) Whether the achievement (or the particular version of the technology being proposed) truly led to a functioning, useful, or marketable technology. The SI system is used universally, and today, every scientist and engineer uses this system of units.

9) Is the proposal adequately supported by significant references and citations (minimum of five, but as many as needed to support the milestone), such as patents, contemporary newspaper articles, journal articles, or citations to pages in scholarly books? At least one of the references must be from a scholarly book or journal article. 'Scholarly' is defined as peer-reviewed, with references, and published. The references, adequately establish and support the dates, location and importance of the achievement, and the claims made in the proposal.

10) Are the scholarly references recent? If not, has there been more recent scholarly research which ought to be taken into account? Although the references are not recent, I believe there is really no need for recent references since the SI system of units is so widely used that any current engineering textbook uses, and more or less explains the SI system.

11) If the names of individual persons are mentioned in the citation, care should be taken that those persons are the engineers (as opposed to, say, the program managers) who designed the technology. The only name mentioned is that of Giovanni Giorgi.

12) The citation’s word length must not exceed 70 words (the maximum which will fit on the plaque). 60-65 words are preferred for aesthetic reasons. (Draft of a proposed new citation) In October 1901 in Rome, Giovanni Giorgi, an Italian engineer, and a Professor at the University of Rome, proposed to rationalize the equations of electromagnetism and to add a fourth unit, electrical in nature, to the three mechanical units of measurements (meter, kilogram, second). Giorgi’s proposal is the origin of the International System of units (SI) currently used and named also the “Giorgi system”.

13) Is the citation understandable by the general public (e.g. spell out acronyms, avoid jargon)?
Yes.

14) Milestone plaques are permanent and will be read by future viewers. Is the citation phrased in a way that does not depend on present perspective? Will it be understandable in the future?" Yes.

Based on the above, I strongly recommend approval of this Milestone Proposal.

Michael P. Polis, Member, IEEE History Committee

## Missing details of the proposal -- Administrator4 (talk) 15:26, 17 June 2019 (UTC)

The proposers need to complete the section that describes the relationship of the proposed location of the plaque to the achievement being recognized. Did Giorgi do his work on units at the University of Rome, or somewhere else? He did not become a professor there until 1906. Was the meeting of the Association Ellettrotechnica Italiana where Giorgi presented his paper on 13 October 1901 held at the University of Rome, or at some other place in Rome? The title page of the published paper does not specify.

### Re: Missing details of the proposal -- Fabriziofrezza (talk) 11:40, 6 August 2019 (UTC)

For what concerns the issue about the plaque location, it is impossible to locate the Milestone where the 1901 meeting was held because the original building is no longer there and there is a modern supermarket now. Anyway, since the achievement, in this case, is immaterial, in my opinion, there is no need to locate the plaque in that exact place. There is no doubt that the ideas, expressed in that meeting, formed in Giorgi’s mind after his technical studies performed at “La Sapienza” University, where a few years later he came back as Professor. Moreover, even if in 1901 Giorgi first proposed that the MKS system needed to be extended to a fourth unit associated with Electromagnetism, it was only in 1935 that the International Electrotechnical Commission (IEC) adopted Giorgi's system, without choosing a specific fourth unit: and from 1913 to 1939 Giorgi worked as a Professor in the Engineering Faculty of "La Sapienza" University of Rome.

## -- Amy Bix (talk) 02:03, 5 September 2019 (UTC)

I find the current wording of the citation rather clunky. Possible suggestions for modification:

In 1901, Giovanni Giorgi, professor at the University of Rome, offered an important contribution toward rationalizing the equations of electromagnetism. His proposal added a fourth unit, electrical in nature, to the three mechanical units of measurement (meter, kilogram, second). Giorgi's ideas became the origin of the International System of Units (IS), currently used in all fields of science and engineering.

## Mike Polis comments -- Administrator1 (talk) 13:20, 10 September 2019 (UTC)

In 1901 Giovanni Giorgi first proposed a rationalization the equations of electromagnetism, and adding a fourth unit, electrical in nature, to the three mechanical units of measurements (meter, kilogram, second). While he was a professor at the University of Rome, the International Electrotechnical Commission adopted a version of Giorgi’s system, so that his ideas form the basis of the now universally adopted International System (SI) of units.

## Contents

- 1 Comments on proposal -- Rich (talk) 19:03, 12 March 2019 (UTC)
- 2 Advocate's Statement by Michael P. Polis History Committee Member -- Polismpp1125 (talk) 14:01, 31 May 2019 (UTC)
- 3 Missing details of the proposal -- Administrator4 (talk) 15:26, 17 June 2019 (UTC)
- 4 -- Amy Bix (talk) 02:03, 5 September 2019 (UTC)
- 5 Mike Polis comments -- Administrator1 (talk) 13:20, 10 September 2019 (UTC)