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The new SI: units of measurement based on fundamental constants

Event

Starts:

January
242011

09:00

Ends:

January
252011

17:00

Location

The Royal Society, London, 6-9 Carlton House Terrace, London, SW1Y 5AG

Overview

 

Sr+ ion optical clock chamber, courtesy of NPL.

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.

Event organisers

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Schedule of talks

Session 1

7 talks Show detail Hide detail

Welcome

Mr Stephen Cox

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Introduction

The Rt Hon David Willetts MP, Minister for Universities and Science

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Adapting the International System of Units to the 21st century (with Professor Ian Mills FRS)

Dr Terry Quinn CBE FRS, BIPM

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Adapting the International System of Units to the 21st century (with Dr Terry Quinn CBE FRS)

Professor Ian Mills FRS

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The Avogadro constant: counting atoms in a single-crystal 28Si sphere

Dr Peter Becker

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The watt balance: determination of the Planck constant and redefinition of the kilogram

Dr Michael Stock

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Quantum Hall Effect and Metrology

Professor Klaus von Klitzing ForMemRS

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Session 2

4 talks Show detail Hide detail

The role of the international prototype of the kilogram after the redefinition of the SI units

Dr Richard Davis

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Quantum theory of microscopic and macroscopic mass

Professor Christian Bordé

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A new definition for the mole based on the Avogadro constant: a journey from physics to

Dr Martin Milton

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SI and non-SI units for biological quantities

Dr Adrian Bristow

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Session 3

5 talks Show detail Hide detail

The Boltzmann constant from the speed of sound in a not quite spherical cavity

Accurate radiometry from space: an essential tool for climate studies

Dr Nigel Fox

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Spectroscopy of muonic hydrogen: determining the proton charge radius

Dr François Nez

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Ultracold atoms and precise time standards (with Dr Gretchen Campbell)

Dr William D. Phillips

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Ultracold atoms and precise time standards (with Dr Bill Phillips )

Dr Gretchen Campbell

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Session 4

4 talks Show detail Hide detail

Learning from: length, time and the redefined SI metre

Dr John Hall

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When should we change the definition of the second?

Professor Patrick Gill

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Metrology of time in the context of general relativity

Dr Bernard Guinot

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Dr Terry Quinn CBE FRS

The new SI: units of measurement based on fundamental constants The Royal Society, London 6-9 Carlton House Terrace London SW1Y 5AG UK