What does a kilogram weigh? Middle school science classes often teach that the unit is based on the weight of water—specifically a cube of water, a tenth of a meter on each side, at just above freezing. This used to be the case, but it isn’t actually true anymore—since 1875, the kilogram has been defined by one specific platinum cylinder, known affectionately as “Le Grande K” and officially as “the International Prototype Kilogram,” or IPK. It stands stands an inch-and-a-half high and wide and is housed in a vault outside Paris, inside three concentric glass containers to protect it from dust and other weight-altering debris. Every scale in the world—even those that measure in pounds—is ultimately based on the IPK, which was commissioned by the General Conference on Weights and Measures. But the IPK’s uniqueness may be its downfall. That’s why in 2005, the International Committee for Weights and Measures proposed that the kilogram be slightly redefined, anchored not to a physical object but to some fundamental property of nature that could be easily replicated in labs across the world. After several deferrals, the international community of metrologists (scientists who study measurements; yes this is a real thing) has decided to use theoretical math to help redefine the kilogram. They are doing this via the “Planck constant,” the number that relates a particle’s frequency, meaning how fast it goes through its wavelike motion, to its energy. From there, using Einstein’s famous E=mc² equation, we can convert that calculated energy into mass. So in the end, we can discern the precise mathematical relationship between particle frequency and weight, which means that we can define the kilogram by particle frequency instead of by an object. And particle frequency is something that we can use in multiple places, without compromising anything. But, the Planck constant is very, very small. That makes it very, very difficult to complete the above calculation—it is so difficult, in fact, that scientists don’t expect to complete it until 2018. One major part of the problem is that we still don’t have a precise measurement for the Planck constant. So a bunch of researchers are trying to calculate one. http://www.businessinsider.com/scientists-change-how-much-a-kilogram-weighs-2016-7
Umm ... first they say they want something that can be "easily replicated in labs", and then they chose something that takes years to figure out. I hope this only means the initial calculation, and from that, replication will be easier, as proposed?
