By the decision of the intergovernmental General Conference in the International Bureau of Weights and Measures, on May 20, the measurement system was updated. This event is dedicated to an article published in the Los Angeles Times.
Metrologists abandoned obsolete material standards and tied the values to the universal coefficient — Planck’s constant (this fundamental physical constant of quantum theory relates the energy of a quantum of electromagnetic radiation to its frequency). The famous Parisian kilogram standard Le Grand K, used since 1889, and its copies all over the world turned into historical artifacts and lost their original meaning for the International System of Units (SI). The redefinition of units of measurement is timed to the World Day of Metrology, which is celebrated on May 20.
Scientists have been making gradual SI reform for several decades. This system was adopted in 1960 and identified seven basic units of measurement: kilogram, meter, second, ampere, kelvin, mole, and candela. This year the time has come for an official redefinition for four of them: a kilogram, a mole (measuring the amount of a substance), an ampere (a unit of electrical discharge) and a kelvin (which determines the thermodynamic temperature).
The most "problematic" unit for scientists was the kilogram, because its material standard of the XIX century from platinum and iridium was losing weight year after year. Over the past 130 years, Le Grand K has decreased by approximately 50 micrograms.
To solve the problem, metrologists turned to quantum physics. A sophisticated and constantly improving device called the Kibble scale was invented to establish the relationship between mass and electric power back in the 1970s. However, it was only in the 21st century that scientists were able to modernize it so much that he “learned” to measure the value of the Planck constant with high accuracy. The binding of standard units of measure to this constant coefficient in the Universe made it possible to calculate ideal standards and determine their constant values.
- Kibble Scale NIST-4 Option
- © nist.gov
“Unlike a physical object, the main constant is unchanged. Now the kilogram has the same mass on Earth, on Mars, and even in the Andromeda galaxy, ”says Stephan Schlamminger, a physicist at the National Institute of Standards and Technology (NIST) in Gaithersburg (USA).
Metrologists are confident that redefining the kilogram, mole, ampere, and kelvin represents a turning point for all of humanity.
“The ability to conduct increasingly accurate measurements is an integral part of the development of our species,” says NIST director, metrologist Walter Copan.
At the same time, for most people on the planet, changes in the measurement system will be completely invisible, metrologists are sure. The use of unchanged mathematical standards will concern scientists who are engaged in physics.
"From now on, scientists are not guided by the weight of platinum and iridium in Paris, but by the laws of physics," said Ian Robinson, a researcher at the US National Physical Laboratory.