Kilogram: Introduction | NIST - National Institute of Standards and ...
2018年5月14日 · For more than a century, the kilogram (kg) — the fundamental unit of mass in the International System of Units (SI) — was defined as exactly equal to the mass of a small …
Kilogram: The Past | NIST
2018年5月14日 · For almost a century and a half, much of the world used a highly polished, golf ball-sized cylinder of a platinum alloy as the international standard for mass measurement — a …
Definitions of SI Base Units | NIST
2019年5月29日 · The kilogram is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015 ×10 −34 when expressed in the unit J s, which is equal to kg m 2 …
SI Units - Mass | NIST - National Institute of Standards and …
2011年3月30日 · The SI unit of mass is the kilogram (kg). In science and technology, the weight of a body in a particular reference frame is defined as the force that gives the body an …
Kilogram: The Present | NIST - National Institute of Standards and ...
2018年5月14日 · But modern measurement science has moved away from using physical objects or other substances as standards. Before May 20, 2019, the kilogram was the lone remaining …
Kilogram: The Future - NIST
2018年5月14日 · Starting on May 20, 2019, the kilogram is officially defined in terms of a quantum-mechanical quantity known as the Planck constant (h), which will be given an exact …
Kilogram: Mass and Planck's Constant | NIST - National Institute of ...
2018年5月14日 · How could the SI kilogram unit — embodied in a single lump of metal cast in the 19th century — be redefined in terms of an invariant of nature and scaled up or down …
Kilogram: Focus on History | NIST
On May 20, 1875, 17 different countries signed the Treaty of the Meter (also called the Meter Convention) to establish new international prototypes for mass and length. In addition to …
The NIST Do-It-Yourself Kibble Balance (Made with LEGO® Bricks!)
2018年5月14日 · For more than a century, the kilogram — the fundamental mass unit in the International System of Units (SI) — was defined as exactly equal to the mass of a small …
Kilogram: Disseminating the New Kilogram | NIST - National …
2018年5月14日 · Deploying the Kilogram by Magnetic Levitation. Even though researchers now have a new definition of the kilogram, they still need to disseminate it via physical artifacts …