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# Teach the New SI

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In November 2018, the world’s measurement experts voted and unanimously approved a revision of the International System of Units (SI) that establishes a measurement system entirely based on physical constants of nature. The changes took effect on World Metrology Day, May 20, 2019. Learn more about the Road to the Revised SI.

• SI Units Card Deck (NIST SP 1297): This fun interactive educational activity is designed to help students enhance their SI understanding, including the Defining Constants, Base Units, Derived Units with Special Names, and Prefixes. With multiple game variations, games may be differentiated for multiple instructional and skill levels. Instructional Level: Grades 3 to Higher Education.

• Meet the Constants: The revised SI rests on a foundation of seven values, which are the same everywhere in the universe. These constants define the seven SI base units, from the second to the candela. Engage with the interactive infographic; click on each of the SI units to see which constants define them.
• Universal Constants: A New Foundation of Measurement (Jason Learning). Follow the work of NIST metrologists as they move to measurements based on universal constants. Lessons and activities focus on physical science and mathematics related to the new International System of Units (SI). Explore themes that include redefining measurement, pursuing accuracy, achieving precision, and measurement process innovation. Instructional Level: Grades 8 to 12.
• Explore Career Role Model Videos for three NIST physicists: Patrick Egan, Darine Haddad, and Toby Herman.
• Highlighted Activities:
• Accuracy vs. Precision (Video). NIST Role Models discuss the concepts of accuracy and precision.
• Accuracy vs. Precision - Focus on Precision. Discuss the definitions of accuracy and precision. Compare and contrast between these terms in daily life. Describe the significance of improvements in accuracy and precision.
• Problems with Precision. Explore situations where little variations caused big problems, including the Mars Climate Orbiter and Gimli Glider mix-ups.
• A Planck to Stand On. Learn about the research of Max Planck and explore a simulation.
• Innovating with Constants.  Consider how the move to universal constants supports scientific innovation.
• NIST International System of Units Match Game. Students spin the wheel to select a SI base unit, then select fundamental constants used to form the base unit.
• Relating SI Units to the 'Defining Constants', Metrologia, Blattner, P. and Brown, Richard, J. C. (May 2024) - DOI 10.1088/1681-7575/ad4cef. The direct relationship of any SI unit to the defining constants is discussed.
• An Introduction to the New SI. Physics Teacher, 55, 1, 16 - 21, Knotts, S., Mohr, P. J., and Phillips, W. D. (January 2017) - DOI: 10.1119/1.4972491. This education article highlights recent changes to the seven (7) International System of Units (SI) base units in terms of fundamental constants.
• What Chemistry Teachers Should Know about the Revised International System of Units (Système International), Journal of Chemical Education, 96, 4, 613 - 617. J. Giunta. (January 30, 2019) - DOI: 10.1021/acs.jchemed.8b00707. Approved SI changes that impact classroom chemistry instruction are discussed.
• Introducing High School Students to the Avogadro Number and the Mole Concept Using Discovery with Calculations Based on Physical Properties of Elements, Crystal Structures, and 28Si Spheres, Journal of Chemical Education, 98, 3, 790 - 795. Bindel, T. H. (January 29, 2021) - DOI: 10.1021/acs.jchemed.0c01132. Explore an instructional approach where students discover the Avogadro number and the mole concept.
• A More Fundamental International System of Units, Physics Today 67, 7, 35. Newell, D. (July 1, 2014)
• What is the Planck Constant (Poster). The Planck Constant is a number that defines the amount to energy in those quanta and expresses how small things can be. Explore this infographic!
• NIST in 90: Measuring Planck's Constant (Video).
• Kibble Balance. Investigate the principles used to realize the kilogram.

Credit: Photo illustration by B. Hayes/NIST
• The Last Artifact documentary (Montana PBS) and companion Grade 5 to 12 educational resources, which document the work that went on behind the scenes to modernize the International System of Units (SI).

### Resources

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Created December 6, 2021, Updated May 30, 2024