Did you know that the kilogram has been inaccurate all along?

If you’ve made unsuccessful attempts at losing weight and blamed it on the accuracy of the kilogram, you’re not going to be able to do that anymore! Apparently, the kilogram, one of the seven units of measure, is not as accurate as it should be. But now the Planck Constant, which is an important value in quantum physics named after the physicist Max Planck, will be the basis of the new and more accurate kilogram unit.  

In the international system of units, the kilogram is the only unit still defined by a physical object. Since 1889, in a vault near Paris, under three glass domes lies a four-centimetre cylinder made of platinum and iridium that defines our current kilogram. All the scales in the world refer to this kilogram. However, the tricky part of basing a unit of measure on a block of metal is that since the ‘original kilogram’ has lost weight over the years, all the world’s scales are slightly off, about 50 millionths of a gram to be precise. Clearly, a new standard which doesn't change over time was the need of the hour.

Using a state-of-the-art device called the Kibble balance for measuring mass, the National Institute of Standards and Technology (NIST) has now made an extremely precise determination of Planck’s constant. Electromagnetic forces are used to balance a kilogram mass. These forces are provided by a coil of wire between two permanent magnets.

The new measurement of Planck's constant is 6.626069934 x 10-34 kg-m2/s according to NIST. The uncertainty is only 13 parts per billion. The previous measurement in 2016 had an uncertainty of 34 parts per billion. These new results have been accepted for publication in the journal Metrologia and will redefine the entire International System of Units by 2018 after consideration by The Committee on Data for Science and Technology (CODATA).

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For industries that require precision in measurements such as pharmaceuticals and food testing, the effects of this change will trickle down to every part of the process. For the rest of us, watching our weight is probably going to be the same, perhaps with the uncertainty reduced to only 13 parts per billion.

Source:

National Institute of Standards and Technology (NIST)
DOI: 10.1088/1681-7575/aa7bf2
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