Ethan Dipietro
Redefining the World’s Measurement System
The French revolution of 1789 allowed the newly independent citizens to create their own system of measurement and redefine units. At the time, there were thousands of confusing traditional units of measure and the French sought to replace it with what they considered a rational system, in keeping with Enlightenment ideals, that would be based on simple multiples of 10. In 1791, the French National Assembly directed the French Academy of Sciences to undertake this project and replace the system. The Academy decided that in order to ensure invariability, the system would be based on a natural physical unit.
The French decided to use the length of one ten-millionth of the distance from the equator to the North Pole to define a meter. Astronomer Pierre-François-André Méchain took 10,000 readings to get the latitude and mailed it to France, yet soon discovered an error of 0.2 mm in the distance between the equator and the North Pole. The gram was defined through the metre and was established as equal to the mass of one cubic centimetre of water at its maximum density. Méchain’s error was built into the kilogram since the gram was based on the meter. The French minted a cylinder weighing 1,000 times the mass of a gram and defined it as the kilogram. The kilogram is the “gold standard” for measuring mass and its standard definition is “a plum sized thing”. It is the only physical object that is used as a unit of measurement; it is the only physical standard.
In 1799, it was declared that “the Metre and Kilogram of the Archives” were the legal standards for all measurements in France with the moto that these new units would be “for all people, for all time”. While, this system was certainly a step up from the thousands of traditional measurements (using units such as the length of a thrown rock), the use of a physical standard has not held up its accuracy in the modern era.
The physical kilogram cylinder is called, “The Grand K” and is kept underground, locked up in a building near Paris. In 1989, the keepers of the “Grand K” placed the original onto a scale with a copy on the other side and soon realized the Grand K had become lighter. They tested the weight of the “Grand K” against all different copies from around the world and found that it had, in fact, lost weight most likely through cleaning processes and natural decay . Even though it was losing weight, since it is the standard, by definition it still weighs exactly one kilogram. This makes all other measurements using the kilogram as a unit, inaccurate and “wrong”, proving the limitations of using a physical object as a standard unit of measurement. In 2014, scientists began trying to redefine the kilogram into a number that the entire scientific community could agree on. Scientists put the “Grand K” onto one side of an equal arm balance and used a magnet (withholding physical contact with the other side) that exerted an invisible force in order to balance the scale. The force equaled the same weight as the “Grand K” and scientists worked to convert this force into a number to define a kilogram.
However, in November of 2018 in Versailles, France an international group of scientists from sixty countries unanimously voted to redefine the International System of Units (metric system). Through this decision, the metric system will now be entirely based on on constant fundamental properties of nature. The kilogram will be now be defined by the Planck constant, a fundamental constant of quantum physics that relates the energy a photon carries with the frequency of its electromagnetic wave. This constant is very small (approximately 6 × 10-34 m2 kg/s) and can only be measured with a precise piece of equipment called a Kibble balance.
This new definition goes back to the original French motto of the metric system that sought to create a measurement system that transcended language barriers and universalized measurements. Therefore, it makes it possible to carry out more accurate measurements anywhere in the world and does not need to be calibrated to a specific physical artifact. Even someone unfamiliar with the measurement system on Earth can still understand these units and could record measurements with the same level of accuracy as we do. While the “Grand K” changed its weight slightly over time, Planck’s constant will never change and will thus stay consistent for all of time.
This change will not visibly affect our everyday lives; at the supermarket, one will not notice a change in a pound of swiss cheese. This change is only expected to affect manufacturers of specialized, microelectronic scientific instruments who will need to change their products in the future to accommodate this revised system to determine the measures of ohms and volts. The extremely small change in the definition of a kilogram will impact these measurements since they involve mass at the electron level. One crucial benefit of this new system is that it will allow pharmaceutical companies to accurately measure chemicals that are a million times smaller than a standard kilogram, allowing doses to be more precise. Unlike with a physical constant, accuracy does not decrease at sizes that are much larger or smaller than the accepted standard, allowing more accurate measurements of milligram/microgram masses. This new system is scheduled to be implemented in mid-May of 2019 and will allow all object’s mass (from a nail to a car) to be measured with the same instrument at equal levels of accuracy and precision.
Bibliography
Arc Of Meridian. (2019). In Merriam Webster. Retrieved January 13, 2019 from https://www.merriam-webster.com/dictionary/arc of meridian
Crane, L. (2018, November 16). Kilogram to be Defined by Planck Constant Instead of a Lump of Metal. Retrieved January 13, 2019, from https://www.newscientist.com/article/2185705-kilogram-to-be-defined-by-planck-constant-instead-of-a-lump-of-metal/
The Editors of Encyclopaedia Britannica. (2018. November 19). Metric System. In Encyclopædia Britannica. Retrieved January 13, 2019 from
https://www.britannica.com/science/metric-system-measurement
Materese, R. (2018, December 06). A Turning Point for Humanity: Redefining the World's Measurement System. Retrieved January 13, 2019 from https://www.nist.gov/si-redefinition/turning-point-humanity-redefining-worlds-measurement-system
Nasser, L. (2014, July 9). The Meter: The Measure of a Man | Radiolab. Retrieved January 13, 2019 from https://www.wnycstudios.org/story/meter-measure-man
Planck's Constant. (2019). In Merriam Webster. Retrieved January 13, 2019 from https://www.merriam-webster.com/dictionary/Planck%27s%20constant
≤ kg [Radio series episode]. (2014, July 13). In Radiolab. New York: WNYC. Retrieved January 13, 2019 from https://www.wnycstudios.org/story/kg
Redefining the World’s Measurement System
The French revolution of 1789 allowed the newly independent citizens to create their own system of measurement and redefine units. At the time, there were thousands of confusing traditional units of measure and the French sought to replace it with what they considered a rational system, in keeping with Enlightenment ideals, that would be based on simple multiples of 10. In 1791, the French National Assembly directed the French Academy of Sciences to undertake this project and replace the system. The Academy decided that in order to ensure invariability, the system would be based on a natural physical unit.
The French decided to use the length of one ten-millionth of the distance from the equator to the North Pole to define a meter. Astronomer Pierre-François-André Méchain took 10,000 readings to get the latitude and mailed it to France, yet soon discovered an error of 0.2 mm in the distance between the equator and the North Pole. The gram was defined through the metre and was established as equal to the mass of one cubic centimetre of water at its maximum density. Méchain’s error was built into the kilogram since the gram was based on the meter. The French minted a cylinder weighing 1,000 times the mass of a gram and defined it as the kilogram. The kilogram is the “gold standard” for measuring mass and its standard definition is “a plum sized thing”. It is the only physical object that is used as a unit of measurement; it is the only physical standard.
In 1799, it was declared that “the Metre and Kilogram of the Archives” were the legal standards for all measurements in France with the moto that these new units would be “for all people, for all time”. While, this system was certainly a step up from the thousands of traditional measurements (using units such as the length of a thrown rock), the use of a physical standard has not held up its accuracy in the modern era.
The physical kilogram cylinder is called, “The Grand K” and is kept underground, locked up in a building near Paris. In 1989, the keepers of the “Grand K” placed the original onto a scale with a copy on the other side and soon realized the Grand K had become lighter. They tested the weight of the “Grand K” against all different copies from around the world and found that it had, in fact, lost weight most likely through cleaning processes and natural decay . Even though it was losing weight, since it is the standard, by definition it still weighs exactly one kilogram. This makes all other measurements using the kilogram as a unit, inaccurate and “wrong”, proving the limitations of using a physical object as a standard unit of measurement. In 2014, scientists began trying to redefine the kilogram into a number that the entire scientific community could agree on. Scientists put the “Grand K” onto one side of an equal arm balance and used a magnet (withholding physical contact with the other side) that exerted an invisible force in order to balance the scale. The force equaled the same weight as the “Grand K” and scientists worked to convert this force into a number to define a kilogram.
However, in November of 2018 in Versailles, France an international group of scientists from sixty countries unanimously voted to redefine the International System of Units (metric system). Through this decision, the metric system will now be entirely based on on constant fundamental properties of nature. The kilogram will be now be defined by the Planck constant, a fundamental constant of quantum physics that relates the energy a photon carries with the frequency of its electromagnetic wave. This constant is very small (approximately 6 × 10-34 m2 kg/s) and can only be measured with a precise piece of equipment called a Kibble balance.
This new definition goes back to the original French motto of the metric system that sought to create a measurement system that transcended language barriers and universalized measurements. Therefore, it makes it possible to carry out more accurate measurements anywhere in the world and does not need to be calibrated to a specific physical artifact. Even someone unfamiliar with the measurement system on Earth can still understand these units and could record measurements with the same level of accuracy as we do. While the “Grand K” changed its weight slightly over time, Planck’s constant will never change and will thus stay consistent for all of time.
This change will not visibly affect our everyday lives; at the supermarket, one will not notice a change in a pound of swiss cheese. This change is only expected to affect manufacturers of specialized, microelectronic scientific instruments who will need to change their products in the future to accommodate this revised system to determine the measures of ohms and volts. The extremely small change in the definition of a kilogram will impact these measurements since they involve mass at the electron level. One crucial benefit of this new system is that it will allow pharmaceutical companies to accurately measure chemicals that are a million times smaller than a standard kilogram, allowing doses to be more precise. Unlike with a physical constant, accuracy does not decrease at sizes that are much larger or smaller than the accepted standard, allowing more accurate measurements of milligram/microgram masses. This new system is scheduled to be implemented in mid-May of 2019 and will allow all object’s mass (from a nail to a car) to be measured with the same instrument at equal levels of accuracy and precision.
Bibliography
Arc Of Meridian. (2019). In Merriam Webster. Retrieved January 13, 2019 from https://www.merriam-webster.com/dictionary/arc of meridian
Crane, L. (2018, November 16). Kilogram to be Defined by Planck Constant Instead of a Lump of Metal. Retrieved January 13, 2019, from https://www.newscientist.com/article/2185705-kilogram-to-be-defined-by-planck-constant-instead-of-a-lump-of-metal/
The Editors of Encyclopaedia Britannica. (2018. November 19). Metric System. In Encyclopædia Britannica. Retrieved January 13, 2019 from
https://www.britannica.com/science/metric-system-measurement
Materese, R. (2018, December 06). A Turning Point for Humanity: Redefining the World's Measurement System. Retrieved January 13, 2019 from https://www.nist.gov/si-redefinition/turning-point-humanity-redefining-worlds-measurement-system
Nasser, L. (2014, July 9). The Meter: The Measure of a Man | Radiolab. Retrieved January 13, 2019 from https://www.wnycstudios.org/story/meter-measure-man
Planck's Constant. (2019). In Merriam Webster. Retrieved January 13, 2019 from https://www.merriam-webster.com/dictionary/Planck%27s%20constant
≤ kg [Radio series episode]. (2014, July 13). In Radiolab. New York: WNYC. Retrieved January 13, 2019 from https://www.wnycstudios.org/story/kg
