Is there a new definition of kg?

The kilogram (kg) has been used as a standard mass measurement since the French revolution, based on the exact mass of a metal block being stored in Paris. However, kilograms may be about to be created for a new, more precise definition and for the first time there will be no need to reference a particular material.

Is the kilogram about to be redefined?

Scientists specializing in mass and measurement units developed a method of describing kilograms by measuring the exact number of atoms in a piece of silicon . They hope, it will overcome the gradual change in the mass of the International kg Model currently being used as the basic reference for the weight measurement unit around the world.

Kg is currently being identified by a cylindrical specimen, about the size of a golf ball, made up of 90% platinum and 10% iridium, which is being stored in France.(Photo: Wikimedia Commons)

Over time, cylindrical specimens, which consisted of 90% platinum and 10% iridium, lost small amounts of metal due to erosion as well as packaging and transporting it. The weight of the standard kg sample decreased by 0.0001g, which is equivalent to the weight of a dust particle, in the last century, meaning it will become less accurate.

The researchers now discover that they can create a precise, reliable and unmodified kg determination using mathematical quantities.

Dr. Giovanni Mana from the Italian National Metrology Research Institute and his colleagues developed a new definition by calculating a mathematical constant, called the Avogadro number - the number of atoms or molecules in a certain physical volume. The number they found " big enough to reach " - 602,214129 a six-million powers (or 602 with 21 zero), is much larger than the number of grains of sand on Earth or the number of stars in Space.

It allows the number of silicon atoms in 1kg to be calculated with an accuracy of approximately 20 atoms per billion, through the definition it is related to the number of Avogadro. This number is then attached to another mathematical constant called Planck's constant , which is used to describe the behavior of quantum particles.

Both numbers need to match.

The new definition, if recognized, could allow scientists to change the way they determine 1kg after decades of research.

First proposed in 1795, kg was originally determined by using the weight of water in a cube of 10cm3 volume at the melting point of water. In 1799, this determination was changed, based on a piece of platinum, but then, kg was defined as the mass of a cylindrical block of 39.7mm composed of 90% platinum and 10% iridium.

All other kilogram calculations are now based on this golf ball -sized metal block, which is being kept at the Office of international weight and measurement units near Sevres, near Paris. .

According to Dr. Mana, the new definition of kg will eventually free scientists from having to use a certain object under the control of the French authorities. He stressed: " In measurement, it is important to ensure independence and democracy, avoid the dictatorship of a single country or laboratory".

Kg is currently the only standard measure based on a physical artifact. Other units, such as meters and seconds, have been defined without reference to a specific object. For example, 1 meter was originally defined in 1793 as 10 / million distance from the equator to the North pole, but it is now defined as 1/299792458 the distance the light moves in a vacuum environment in 1 second.

The new definition of kilograms still needs to get the approval of scientists at the Global Conference on Weight Measurements and International Metrology Systems taking place in the coming time.