In October 1901, a very successful Italian scientist and engineer Giovanni Giorgi showed at the congress of the Associazione Elettrotecnica Italiana (A.E.I.) in Rome that a coherent system of units could be achieved by adding an electric unit to the three mechanical units (centimetre, gram, second) of the existing CGS system. The event can be considered as the birth of what is now known as the International System of Units, or SI.

The history surrounding the birth of SI is an example of how the world of international standardization can truly deliver a solution that meets past, present and future market needs.

The birth of SI is inseparably linked to the personality of Professor Giovanni Giorgi. This far-sighted Italian anticipated future needs and provided as early as 1901 not only suggestions for a coherent system of units, but a full-fledged solution. His case also shows that being ahead of one’s time can draw more criticism than being behind. But fortunately, Giovanni Giorgi had the satisfaction of witnessing how, after many years of seemingly endless debate, his original proposals were accepted without major changes.

This saga is, however, not merely of historical interest. We know that specific styles of art, literature, technology, etc., tend to be superseded by later ones. Here again, Giovanni Giorgi’s legacy is exceptional. Far from being challenged by any better system, the SI (International System of Units) keeps proving its worth.

Readers may know that in Switzerland laws are not imposed by government and that even parliament does not have the power of final endorsement because this is the privilege of its citizens. In a similar way, the SI was accepted by the appropriate organizations, but a perfectly democratic vote took place and is still taking place in an informal but highly efficient way: this is the everyday use of Giovanni Giorgi’s system by the international engineering community.

All historical information presented in these pages comes from the book: "1901-2001, Celebrating the Centenary of SI - Giovanni Giorgi's Contribution and the Role of SI", published in 2001 by the IEC for the 100^th anniversary of the International System of Units.

Examples of units (covering Electricity and magnetism, Light) come from ISO's SI Guide.