How does this change affect? On Friday, November 16, the 26th General Conference on Weights and Measures was held in the French city of Versailles, where several dozen countries voted in favor of overthrowing Le Grand Kilo and redefining the kilogram and three other standard measuring units: the ampere, for the electric current; the kelvin, for the temperature, and the mole, which describes the quantity of a chemical substance. Until now, it had been determined by the grandfather of all kilos: a metal cylinder enclosed in a vault in France. Made of an alloy resistant to corrosion of 90% platinum and 10% iridium. His role has been crucial, as the basis for the world-accepted system for measuring mass, called the Grand K. His copies are distributed around the world, with his own reference, as close as possible to the original From now on, the seven units in the International System of Units will no longer be defined according to material objects; they will be established only by abstract constants of nature. So, instead of using the classical kilogram as a criterion, scientists will use the Planck constant to define a kilogram, which would vary the mass by about 50 micrograms less (0.000000005 kg). No one who is outside an advanced physics laboratory will notice the change. Although the new formula will not affect your bathroom scale, the change is expected to have practical applications in computing, nanotechnology, pharmaceuticals, the study of climate change and other sciences where accurate measurements are required. The Planck constant, h (6.62 * 10-34 m2 kg / s), is the quantum mechanical quantity that relates mass to energy through E = mc2, one of the most popular equations in physics. The redefinition of the kilogram using a universal constant has been an exhausting project, involving decades of research in laboratories around the world, the result of two Nobel prizes in quantum physics and the construction of some of the most intricate machines ever made. How is quantum related to weight in kilos? How will it be measured? Here is the difficult part. The balance Kibble, invented in 1975 by the physicist Bryan Kibble, has an electromagnet that pulls on one side of the scale and a weight on the other. The electromagnets generate a force, like the cranes that are used to lift and move the old cars. The impulse of the electromagnet, the force it exerts, is directly related to the amount of electrical current that passes through its coils. There is, therefore, a direct relationship between electricity and weight. Then, in principle, scientists can define a kilogram, or any other weight, in terms of the amount of electricity needed to counteract its strength. By measuring the current flow through the electromagnet with extraordinary precision, researchers can calculate the mass to an accuracy of 0.000001%. This advance has made the Grand K give way to the small h.