Foto de stock - 20 May 2019, Bavaria, Munich: A high-purity silicon sphere (l) of the Physikalisch-Technische Bundesanstalt (PTB) weighing exactly one kilogram can be seen in the Deutsches Museum next to a copy of the original kilogram. The sphere has a diameter of 9.37 centimeters and is cut from a single crystal. In the future, the sphere can be used to determine what a kilogram is. Photo: Sven Hoppe/dpa. - Munich/Bavaria/Germany

Imagen: 20 May 2019, Bavaria, Munich: A high-purity silicon sphere (l) of the Physikalisch-Technische Bundesanstalt (PTB) weighing exactly one kilogram can be seen in.

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