Today, the definition of 1kg will be calculated by light

Today 20/5, not only is the international measurement day (World Metrology Day) but it will also mark the event: the concept of 1kg will completely change compared to what we know in 130 years by.

Since ancient times, the concept of kg has been defined as a cylindrical platinum-iridium alloy block, called Le Grand K and protected in a basement in the suburbs of Paris. However, every time the scientists processed the cylinder, it lost its atoms and was estimated to have lost a total of 50 micro grams. Thus, starting today, scientists decided to officially define 1 kg as Planck's constant .

Today, next to 1kg, 1 ampere, kelvin and mole are also defined by the new method.

In fact, not wanting to change is changed. Scientists have spent many years studying to prepare for the most logical transition. Today, next to 1kg, 1 ampere, kelvin and mole are also defined by the new method. Scientists say all changes will be easy to update because they do not depend too much on old concepts.

In more detail, 1kg of new definition will be the total volume of a specific number of photons of a particular wavelength. With this change, kg will be determined by two quantities, seconds and meters, which are both physical constants and therefore, more reliable than an artificial object such as an alloy cylinder.

For our normal users, this change will not be so important, but for the scientific community it will be an historic event. It will give researchers a much more precise tool to conduct measurements, which can reaffirm the laws of physics.

Terry Quinn, honorary director of the BIPM International Bureau of Measurement and Weight, said: 'This is the most important decision BIPM has made in the last 100 years. It sounds a bit exaggerated, but perhaps the most important event, at least since 1960, when people accept international measurement systems. "

1. The Kilogram unit is about to be redefined
2. Official: 1 kilogram is no longer 1 kilogram, and so are 3 other basic quantities