Retiring the One Kilogram Standard
Often when we think of priceless artifacts, the kind that are locked away someplace in a vault, what comes to mind are images of crown jewels and gemstones, or perhaps maybe a valuable piece of art work. However, sometimes precious artifacts have a more scientific purpose to them.
Such is the case of a small platinum-iridium metal cylinder that has been stored away in a vault in France for over a century. The cylinder is the one kilogram standard which all kilograms have been calibrated to for the last 129 years. It has also been used to calibrate essentially all of the scales that we use today, which makes the object extremely important. In fact the one kilogram cylinder is so precious that it has only ever been handled four times in its entire existence.
But, despite its lack of handling, many in the scientific community have doubts about the cylinders accuracy. Like any physical object, the one kilogram cylinder is subject to deterioration. Even within the three glass bell jars where it sits, dust and other natural pollutants accumulate on the object which in turn need to be cleaned off of its surface.
Though the practice of cleaning may seem innocuous at first, it can actually have a detrimental effect over time, as even microscopic scratches on the artifacts surface essentially alter the very definition of what it is meant to represent – one kilogram.
To date, scientists estimate that the cylinder has strayed from its original measurement by up to 50 micrograms, so in May of 2019 it will retire from its role of being the one kilogram standard. It will be replaced by a measurement based on mathematics – specifically the Planck’s constant.
An apparatus known as a “Kibble balance,” which uses the Planck constant and electromagnetic force to precisely measure the mass of an object, will become the new standard to which the kilogram is measured.
Scientists say that the general public won’t really notice a difference once the change takes place. For the general public, the precise weight of objects tends to only matter when it comes to shopping for produce at the grocery store and these processes will essentially remain the same. The change would only really be noticed when things that are extremely small are measured such as those used for quantum and nanotechnologies. Nonetheless, it’s a pretty interesting bit of news taking place in the scientific community – at least in this writer’s opinion.
Thanks for Reading
CBC News. (12 November, 2018). Scientists are redefining the kilogram
Clara Moskowitz. (1 November, 2018). Redefining the Kilogram. Scientific America.
National Institute of Standards and Technology: U.S. Department of Commerce. (17 May, 2018). Redefining the world’s measurement system.