BIPMi
BIPMi, or the BIPM International Prototype of the Meter, is a physical artifact that serves as the international standard for the meter, the base unit of length in the International System of Units (SI). It is maintained by the Bureau International des Poids et Mesures (BIPM) in Sèvres, France. The BIPMi is a platinum-iridium alloy bar that is 1 meter long at the temperature of melting ice. It was adopted as the standard for the meter in 1889, replacing the previous standard, the meter bar of the Archives in Paris.
The BIPMi is used to calibrate national prototypes of the meter, which are then used to calibrate
In 2019, the BIPM announced plans to redefine the meter in terms of the speed of light,