Retiring the One Kilogram Standard

in #steemstem5 years ago

kilo (1).jpg


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.

KB (1).jpg


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.


Yes, it is long past time that this last of the fundamental SI units was updated to have a non specific reference and moved to a real universal reference... The others were redefined a while ago, this is the last hold out.

It's strange that they didn't all get updated at the same time. But then again, the original artifacts were probably held in different countries so I'm sure some nations enjoyed the prestige of housing the artifact. I'm just speculating. I dont actually know.

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Probably nothing that political... There was a redefinition that had the 7 base units be derived from the 7 fundamental constants. So, fixing the constants at a particular value instead of the other way around.

Possibly might have something to do with being able to accurately and precisely measure certain things before it can be definitely accepted... Plus, slow moving wheels off organisation... Especially if you are proposing to change fundamental measurement ideas... No big deal for every day life, but pretty important for experimental physicists (and other fields).,

It will be replaced by a measurement based on mathematics

This very same thing happened to the meter years ago.

The metre was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole – as a result the Earth's circumference is approximately 40,000 km today. In 1799, it was redefined in terms of a prototype metre bar (the actual bar used was changed in 1889). In 1960, the metre was redefined in terms of a certain number of wavelengths of a certain emission line of krypton-86. In 1983, the current definition was adopted.

That's interesting. I wasn't aware of that. It makes sense though.

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