# Kilogram has received a new definition. Revolutionary changes to the SI system

**At the General Conference on Weights and Measures in Paris, representatives from 60 countries voted to redefine the International System of Units (SI), which changes the global definition of the kilogram, ampere, kelvin and mole. All these units will now be defined by the fundamental constants of nature.**

In 1889, by decision of the General Conference on Weights and Measures, the standard of the kilogram was established. It is a cylinder made of an alloy of platinum and iridium, który has since been stored under sterile conditions in a safe in the International Bureau of Weights and Measures in Sèvres near Paris. „La Grand K”, because that is its name, has several copies in S aloneèvres, and many countries purchased their own copies, including Poland in 1951.

But the standard will no longer be needed. As of May 20 next year, the kilogram will be calculated based on Planck’s constant. Today, scientists from around the world gathered in Paris voted unanimously to change the way SI units are defined. Starting next year, the kilogram, ampere, kelvin and mole will be defined by the fundamental constants of nature.

The decision will ensure the stability of the entire system in the future and open the way for the application of new technologies, including quantum technologies. Of course, the size of the units will not change. A kilogram will continue to be a kilogram. What will change is the wayób of their determination.

As long as stability „La Grand K” could only be confirmed by porównanie with identical copies, which is a potentially inaccurate process, Planck’s constant is ready to be used anytime, anywhere. It will not be necessary to go to Sèvres to poreóto know the mass with the standard. Kilogram, no more and no less, will be móhead get anyone without having to refer to a metal cylinder locked in a safe.

– The redefinition of the SI is a landmark moment of scientific progress, said Martin Milton, director of the International Bureau of Weights and Measures. – Using the fundamental constants observed in nature as the basis for important concepts such as mass and time means that we have a stable basis with which toórym we can expand our scientific knowledge, develop new technologies and meet society’s greatest challenges – explained.

IT'S OFFICIAL – the science community has voted! All of the SI units will be defined by fundamental constants of nature as of May 20, 2019! #SIRedefinitionhttps://t.co/U1V0TFxXLG pic.twitter.com/xpcddbAAmV

— NPL (@NPL) November 16, 2018

– Today is the culmination of dozens ofów years of scientific workóIn dealing with measurements around the world. We will no longer be bound by the limitations of the objectóIn our measurement of the world. We have universal units available, whichóre could pave the way for even greater accuracy and even accelerate scientific progress – Admitted Barry Inglis, director of the International Committee for the Scientific and Technological Cooperation (ICS). Weights and Measures.

The new definitions affect four of the seven basic SI units: kilogram, ampere, kelvin and mole; and all units derived from them, such as volt, ohm and joule.

Kilogram (mass) will be determined on the basis of Planck’s constant. The ampere (current) will be determined by the elementary electric charge. Kelvin (temperature) based on Boltzmann’s constant, and the mole (amount of matter) through Avogadr’s constant. The revised SI will retain its usefulness and facilitate technical innovation.

There have already been similar changes before. By 1967, the unit of time – second – was calculated as a fraction of a day (specifically, 1/86400th of a day). In 1967, the General Conference on Weights and Measures established that a second is a time równy 9192631770 radiation vibrations of the cesium-133 atom. The same was true of the meter. Since 1983, a meter is the distance that light travels in prófife at 1/299792458 of a second. Previously, there was a meter standard locked in a safe in the Sèvres in the form of a metal rod, and even before that it was a fraction of the length of a meridian. The speed of light in pró¿ny and the frequency of cesium-133 radiation are fundamental constants and remain unchanged.

Redefinition of the second was the basis of technology, whichóra has changed sposób communication around the world via GPS and the Internet. The new changes will have far-reaching effects on science, technology, trade, health and the environment, and many other areas of life.

When it comes to at least a kilogram, accurate measurement is crucial in many areas, such as the development of theój leków or precision engineering. Current technologies show that porówn the pattern with Sèvres with its copies spread around the world, shows discrepancies. When it comes to about 50 parts per billion, less than the weight of a single eyelash, it doesn’t matter at all to a mere mortal, but in nanotechnology it does colossally. In today’s world, such discrepancies are unacceptable.

It is also important to remember that units such as the newton, pascal or tesla are defined by the kilogram. So any discrepancy or change in the pattern, even by a speck of dirt, affects the derived units.

Sourceóbackground: NPL, BBC, fot. Greg L/ Wikimedia Commons/ CC BY-SA 3.0. Pictured is a kilogram standard from Sèvres