• not_woody_shaw@lemmy.world
      link
      fedilink
      English
      arrow-up
      5
      ·
      6 days ago

      It’s a room made from platinum-iridium, and kept in a triple-locked vault at the International Bureau of Weights and Measures in France.

      • grozzle@lemm.ee
        link
        fedilink
        English
        arrow-up
        3
        ·
        6 days ago

        unfortunately, opening the door changes the temperature, so in practice instruments are calibrated from copies of the room built at other metrology institutions around the world.