Measure for Measure

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  • Stephan Schlamminger looks at the origins of the Planck constant and its current role in redefining the kilogram.

    • Stephan Schlamminger
    Measure for Measure
  • Alberto Moscatelli surveys a series of experiments on the electron g-factor that marked the departure from the Dirac equation and contributed to the development of quantum electrodynamics.

    • Alberto Moscatelli
    Measure for Measure
  • Optical-lattice clocks have pushed the limits of frequency measurement — to such an extent that a tiny difference in altitude affects the clock's tick rate, as Hidetoshi Katori elucidates.

    • Hidetoshi Katori
    Measure for Measure
  • Narrowing down the value of the Hubble constant has been problematic — probably a manifestation of the dark-energy mystery, writes Barbara Ryden.

    • Barbara Ryden
    Measure for Measure
  • Klaus von Klitzing tells the story of the quantum Hall effect's impact on metrology.

    • Klaus von Klitzing
    Measure for Measure
  • Temperature measurement standards rely on highly reproducible states of matter — including eutectic points, as Jonathan Pearce explains.

    • Jonathan Pearce
    Measure for Measure
  • Every now and then, an extra second is added to an earthly year — a cause for trouble and debate, as Felicitas Arias has been witnessing.

    • Felicitas Arias
    Measure for Measure
  • Nick van Remortel demystifies natural unit systems — and advises what to do when you see a mass expressed in GeV.

    • Nick van Remortel
    Measure for Measure
  • The most precise measurements of the atomic masses of the proton and the electron make use of Penning traps, and for the latter, a hydrogen-like ion, as Edmund Myers explains.

    • Edmund G. Myers
    Measure for Measure
  • The bit is a proper unit of measurement and should be recognized as such, argues Iulia Georgescu.

    • Iulia Georgescu
    Measure for Measure
  • Michel Van Camp and Olivier de Viron are attracted to the fluctuations in the Earth's gravitational pull.

    • Michel Van Camp
    • Olivier de Viron
    Measure for Measure
  • Some concepts are useful but difficult to quantify, as Philip Ball illustrates with the property of hydrophobicity.

    • Philip Ball
    Measure for Measure
  • Yuqin Zong sheds light on photometry's fundamental unit.

    • Yuqin Zong
    Measure for Measure
  • Enrico Massa and Giovanni Mana expound on the substance of the Avogadro constant.

    • Enrico Massa
    • Giovanni Mana
    Measure for Measure
  • Vincent Icke paints a portrait of the bewildering cosmological constant.

    • Vincent Icke
    Measure for Measure
  • François Piquemal tells the story of the ampere, which bridges mechanical and electromagnetic units.

    • François Piquemal
    Measure for Measure
  • Despite intensified efforts, measurements of the gravitational constant continue to fail to converge, as Terry Quinn explains.

    • Terry Quinn
    Measure for Measure
  • Michael de Podesta discusses the current definition of the kelvin — and why it is worth changing one last time.

    • Michael de Podesta
    Measure for Measure