Interferometer (IMAGE)

Physikalisch-Technische Bundesanstalt (PTB)

Interferometer

Caption

Just like all of the other units, the kilogram will be defined via a natural constant as of May 2019. A constant was selected for this whose unit contains the kg and whose value can be measured with high accuracy. A decision was made in favor of Planck's constant h. Its value was determined by means of two independent experiments: the Avogadro experiment (here, the atoms contained in a perfect silicon monocrystalline sphere are counted), and the Kibble balance. On this photo: the special interferometer which was developed for the Avogadro experiment.

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