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The new SI: units of measurement based on fundamental constants

24 - 25 January 2011 09:00 - 17:00

 

Organised by Dr Terry Quinn CBE FRS, Professor Ian Mills FRS and Professor Patrick Gill

From the origins of the metric system, when the metre was a fraction of the arc of the Paris meridian and the kilogram the weight of a cubic decimetre of water, the ultimate goal has been a system of measurement based on invariant quantities of nature. After more than 200 years we are now within reach of achieving this. While the kilogram is still defined as the mass of a Pt-Ir cylinder kept in a vault in Sèvres, serious plans now exist to redefine the kilogram by fixing the numerical value of the Planck constant h; and the ampere, kelvin and mole by fixed numerical values for e, k and NA. With the metre already being defined by the speed of light and the second by an atomic microwave transition, but likely soon to be redefined by an optical transition of much higher frequency, we shall have at last achieved what the savants of the 18th century had sought. The Discussion Meeting will review the relation of the International System of Units to the fundamental constants of physics and progress towards the redefinitions.

The biographies and audio files are available below.

The proceedings of this meeting are scheduled to be published in a future issue of Philosophical Transactions A.

Organisers

  • Professor Ian Mills FRS

    Ian Mills is an emeritus professor of Molecular Spectroscopy in the School of Chemistry at the University of Reading.  After graduating with a D.Phil. in high resolution infrared spectroscopy from St. John’s College, Oxford, in 1954, followed by research fellowship positions at the University of Minnesota and in Theoretical Chemistry at the University of Cambridge, he was appointed to a Lectureship in Chemistry at the University of Reading in 1957.  He was promoted to a Readership in 1964, and to a Personal Professorship in 1966, from which he retired in 1995.  He has about 180 publications in various aspects of high resolution spectroscopy and the application of quantum mechanics to the analysis of molecular spectra, and he was elected to Fellowship of the Royal Society in 1996. He has held a variety of positions in the Faraday Division of the Royal Society of Chemistry, and in IUPAC, and at the BIPM, related to his interests and publications in the language of science.  Since 1995 he has been President of the Consultative Committee on Units at the BIPM. 

  • Professor Patrick Gill

    Patrick Gill is a Senior NPL Fellow at the National Physical Laboratory in Teddington, Middlesex. He received his D.Phil in 1976 from the University of Oxford for gas laser research at the Clarendon Laboratory, and then joined the National Physical Laboratory, developing iodine-stabilised lasers for length metrology. He started research into laser-cooled single trapped ion optical frequency standards during the 1980s. He was appointed an NPL Individual Merit scientist in 1992, and subsequently a Senior NPL Fellow in 1997. Currently, he leads the optical frequency standards research activities at NPL, with interests in optical clocks for redefinition of the second, applications to fundamental physics and clock technology for future aerospace applications. He has published over 100 papers in peer-reviewed journals. He is a visiting professor in physics at the University of Oxford and Imperial College London. 

  • Dr Terry Quinn CBE FRS, BIPM

    Biography

    Terry Quinn obtained a B. Sc in physics at the University of Southampton in 1956, then a D. Phil. at the University of Oxford in 1963. From 1962 to 1977 he was at the National Physical Laboratory working on temperature and later mass measurement. He moved to the International Bureau of Weights and Measures (BIPM) at Sèvres, France, in 1977 as Deputy Director becoming Director in 1988 until his retirement in 2003. While at the BIPM, in addition to being much involved with the organization of international metrology and the development of the proposal to redefine the units of the SI in terms of fundamental constants, he participated in work related to balances, fine suspensions and mass standards. Latterly he led work on the determination of G using a torsion strip balance, the final result being published in 2013. He was elected a Fellow of the Royal Society in 2001.