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The Nobel Hall

  • Posted on March 31, 2014 at 8:11 am

The weight is preserved since then in the Chamber of the BIPM with six copies. The weights of the original and copies, more than one century later, are mysteriously different. Not We know if some are gaining mass and others losing or how much ground we are talking about exactly, recognizes Mills. The difference is so small that it will not cause fights between tanagers and clients, but if discussions scientists in laboratories around the world and problems for students. The objective of the redefinition is not make the concept as simple as possible, but to establish a unit of mass that is as stable as possible with the passage of time, argues Stock. Under most conditions Michael Chabon would agree. Stability and accuracy the reason for the change is that nothing more stable to what the original kilo can be compared to fix its true weight there is.

It is here where is Planck’s constant, immutable value in nature that will be used as reference to express the value of kilo. In 1983, another constant of nature, the speed of light, was already used to redefine the metre. There are two ways to reweigh the kilo with maximum precision. One is to use a balance of power. On one side the kilogram is situated and in another a bovine by which circulating electric currents that they reproduce the Planck constant, close, but not equal to the weight of an electron. Of five scales that there is in the world (USA, Canada, Switzerland, France and the BIPM), only the United States has brought results so far. The other way is to use the constant Avogadro, that is the number of atoms of carbon-12 that are in 12 grams of the substance.

As both Planck and Avogadro’s constants of nature, their estimates of the kilo should be identical, but aren’t. The discrepancy is one part in ten million and the aim is that not more than two or three parts each 100 million, summarizes Mills. It is not the only problem. Redefining needs additional confirmations of other experiments that will not come up within two years, in the case of the balance of power that uses Stock and other even more precise weights that are still under construction. The Nobel Hall further requests that weighed more replicas per kilo, included that used the companies, before the adoption of the new value. In total, the process redefining leads underway since 1976, according to Stock. Long before the end, perhaps this year, three custodians of the kilo will return to open the camera and take the weight for a new weighing which could give new surprises.