In Memoriam

Anders J. Thor

(Email June 30, 2011): Dear Colleagues,

As you may know I'm in favour of defining the SI base unit for mass by fixing the value of the mass of carbon 12, not by fixing the value of the Planck constant. You say that many would say that we have lost this battle already. I don't think so.. This is not the end. It is not even the beginning of the end. It is the end of the beginning (Winston Churchhill 1942). For your information I attach my personal views.

Best regards
The International System of Units, Système International d'Unités, (international abbreviation SI), used worldwide both in everyday commerce and in science, is devised around seven independent base quantities: time, length, mass, electric current, temperature, luminous intensity, and amount of substance. In response to ever-increasing demands for accuracy, the definitions of the units for measurement of these quantities evolve over time.

The organizations that maintain the SI system, also known by their French initials, are the BIPM (International Bureau of Weights and Measures, Bureau international des poids et mesures), the CGPM (General Conference on Weights and Measures, Conférence générale des poids et mesures) and the CIPM (International Committee for Weights and Measures, Comité international des poids et mesures).

At its 24th meeting (October 2011), the CGPM adopted a Resolution on the possible future revision of the SI, called the “New SI”. The BIPM has expressed its commitment “to encourage communication, awareness and debate on the possible revision of the SI”, and many scientists and metrologists have raised serious unanswered criticisms about many aspects of the New SI, (see Documents).

The official committees that decide on the New SI Proposal meet behind closed doors, with observers expressly forbidden, and have refused to answer basic questions about their proposal, in particular questions concerning their proposed redefinitions of the kilogram and the mole (see FABNAQ's). Although the official BIPM journal Metrologia has published a few papers describing some of the criticisms of the New SI, many researchers feel the journal is strongly biased toward the New SI Proposal, and papers critical of the New SI are routinely rejected.

Thus a spirited ad hoc online debate on the merits of the New SI has emerged. was established in order to make these concerns about the proposed New SI open to the public, scientists and lay observers alike, to facilitate participation in the debate, and to establish a permanent scientific record of the main issues and concerns.

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