One of the exciting characteristics of metrology is its intimate relationship between fundamental physics and the leading edge of technology which is needed to perform advanced and challenging experiments and measurements. This title includes a set of lectures which present the relevant progress in Metrology.

Over the last decade of the 20th century, many improvements took place in the field of metrology and fundamental constants. These developments and improvements are discussed in this book. The old caesium SI second definition has found a new realization with the fountain approach, replacing the classical thermal atomic beam. The use of cold atom techniques, slowed down and cooled, has opened a number of unexpected avenues for metrology and fundamental constants, one of these possibilities being the atom interferometry. Another development was the demonstration of the possiblility of performing a direct frequency division in the visible, using short femtosecond pulses. Many other developments are also discussed.

The object of this NATO Advanced Study Institute was to pre sent a tutorial 'introduction both to the basic physics of recent spectacular advances achieved in the field of metrology and to the determination of fundamental physical constants. When humans began to qualify their description of natural phenomena, metrology, the science of measurement, developed along side geometry and mathematics. However, flam antiquity to modern times, the role of metrology was mostly restricted to the need of commercial, social or scientific transactions of local or at most national scope. Beginning with the Renaissance, and particularly in western Europe during the last century, metrology rapidly developed an international character as a result of growing needs for more accurate measurements and common standards in the emerging indus trial society. Although the concerns of metrology are deeply rooted to fundamental sciences, it was, until recently, perceived by much of the scientific community as mostly custodial in character.

The reliability and accuracy of systems of measurement continue to advance. We are about to enter a period of the most stable measurement system we can imagine with the anticipated new definitions of the SI units of measurement; a direct link between fundamental physics and metrology which will eliminate the current definition of the kilogram, until now based upon an artifact. This book presents selected papers from Course 185 of the Enrico Fermi International School of Physics, held in Varenna, Italy, in July 2012 and jointly organized with the Bureau International des Poids et Mesures (BIPM). The papers delivered at the school covered some of the most advanced topics in the discipline of metrology, including nano-technologies; quantum information and quantum devices; biology and medicine; food; surface quality; ionising radiation for health, environment, art and archaeology; and climate. The continuous and striking advances in basic research concerning atomic frequency standards operating both in the visible range and at microwave levels and the applications to satellite systems are also considered, in the framework of a historical review of the international organization of metrology, as are the problems inherent in uncertainty statements and definitions. This book will be of interest to all those whose work involves scientific measurement at the highest levels of accuracy.

The question of a possible temporal variation of the fundamental constants was raised by Paul Dirac in his "large number hypothesis" in 1937. Today it appears in the context of the search for a unified theory of the fundamental interactions. It touches both fundamental and applied physics, as the postulate of the unalterability of the constants is the foundation for modern metrology. The book presents reviews written by leading experts in the field. Focussing on the question of variations of the fundamental "constants" in time or space, the chapters cover the theoretical framework in which variations are expected and the search for variations of quantities like the fine-structure constant, the electron/proton mass ratio, g-factors of proton and neutron etc. in astrophysical and geophysical observations and in precision experiments with atomic clocks and frequency standards.

Metrology is the study of measurement. It includes all theoretical and practical aspects of measurement and may be divided into three subfields: Scientific or fundamental metrology concerns the establishment of measurement units, unit systems, development of new measurement methods, realization of measurement standards and the transfer of traceability from these standards to users in society. This handbook contains articles dealing with general topics of measurement and articles on particular subjects in mechanics and acoustics, electricity, optics, temperature, time and frequency, chemistry, medicine and particles. The contributions of the first part are sumamrized as follows. Introduction Units Fundamental Constants Fundamentals of Materials Measurement and Testing Measurement of Mass Desnity Measurement and Instrumentation of Flow Ultrasonics Measurement of Basic Electromagnetic Quantities Quantum Electrical Standards Metrology of Time and Frequency Temperature Measurement Metrology in Medicine

It is now widely recognized that measurement data should be properly analyzed to include an assessment of their associated uncertainty. Since this parameter allows for a meaningful comparison of the measurement results and for an evaluation of their reliability, its expression is important not only in the specialized field of scientific metrology, but also in industry, trade, and commerce. General rules for evaluating and expressing the uncertainty are given in the internationally accepted ISO Guide to the Expression of Uncertainty in Measurement, generally known as the GUM. Evaluating the Measurement Uncertainty details the theoretical framework on which the GUM is based and provides additional material on more advanced topics such as least-squares adjustment and Bayesian statistics. The book does not require previous knowledge other than elementary calculus and can be read as a complement to the GUM or as a stand-alone reference source. It stresses fundamental principles and illustrates their applications through numerous examples taken from many different fields of metrology. The book includes practical guidance as well as theoretical aspects, resulting in an invaluable resource for metrologists, engineers, physicists, and graduate students involved with measurements in academia and industry.