Slashdot Mirror
Kilogram Gets a New Definition (bbc.com)
Scientists have changed the way the kilogram is defined. Currently, it is defined by the weight of a platinum-based ingot called "Le Grand K" which is locked away in a safe in Paris. On Friday, researchers meeting in Versailles voted to get rid of it in favour of defining a kilogram in terms of an electric current. From a report: The decision was made at the General Conference on Weights and Measures. But some scientists, such as Perdi Williams at the National Physical Laboratory in the UK, have expressed mixed feelings about the change. "I haven't been on this project for too long but I feel a weird attachment to the kilogram," she said. "I think it is such an exciting thing and this is a really big moment. So I'm a little bit sad about [the change]. But it is an important step forward and so the new system is going to work a lot better. It is also a really exciting time, and I can't wait for it to happen."
Le Grand K has been at the forefront of the international system of measuring weights since 1889. Several close replicas were made and distributed around the globe. But the master kilogram and its copies were seen to change -- ever so slightly -- as they deteriorated. In a world where accurate measurement is now critical in many areas, such as in drug development, nanotechnology and precision engineering -- those responsible for maintaining the international system had no option but to move beyond Le Grand K to a more robust definition.
Le Grand K has been at the forefront of the international system of measuring weights since 1889. Several close replicas were made and distributed around the globe. But the master kilogram and its copies were seen to change -- ever so slightly -- as they deteriorated. In a world where accurate measurement is now critical in many areas, such as in drug development, nanotechnology and precision engineering -- those responsible for maintaining the international system had no option but to move beyond Le Grand K to a more robust definition.
The strength of the earth's gravitational field varies. If you are using a Kibble balance to calibrate your weights, how do you compensate for that? Your kilogram mass will vary from location to location.
Google: earth gravitational field
https://earthobservatory.nasa....