On November 16, 2018, at the 26th meeting of the General Conference on Weights and Measures (CGPM), a resolution was adopted that introduced historical changes into the International System of Units (SI). This decision, effective from May 20, 2019, established that the SI units of measurement will be defined by means of a set of seven fixed…

The United States is one of only three countries in the world that remain uncommitted to the metric system. Perhaps to policymakers the decision to hang on to miles, pounds, and gallons is one of tradition. However, as a physics teacher I have seen firsthand how growing up with U.S. Customary Units (commonly called by the pseudonym "British…

Plans are under way to redefine the International System of Units (SI) around 2018. The new SI specifies the values of certain physical constants to define units. This article explains the new SI in order to provide a resource for high school teachers as well as for advanced students already familiar with the pre-2018 SI.

Since much of SI is based on physics and mathematics, physics teachers have the background to teach SI. We present this review and summary in a series of SI notes in order to help teachers answer many questions about the SI that often are, or should be, asked (for example, in workshops for teachers). SI should not be considered a jargon to set…

As all physicists know, all units are arbitrary. The numbering system is anthropocentric; for example, the Celsius scale of temperature has 100 degrees between the boiling point of water at STP and the freezing point of water. The number 100 is chosen because human beings have 10 fingers. The best units might be based on physical constants, for…

Lists official SI units, temporarily accepted non-SI units, accepted non-SI units, and multipliers for SI units. (MLH)

Discusses legislation related to SI (International Systems of Units) in the United States. Indicates that although SI metric units have been officially recognized by law in the United States, U.S. Customary Units have never received a statutory basis. (JN)

Describes a card game that demonstrates that most metric units used in beginning physics are composed of six fundamental units. (MLH)

Demonstrates, using specific problems, how various energy units can be converted to joules and power units to watts. Conversion tables are provided for power, energy, generation values, thermal insulation, consumption values, sunlight, with tables also on metric prefixes and time conversions. (SK)

Traces the events leading to the creation of the International Bureau of Weights and Measures (BIPM). Discusses how the units have been represented by their standards, and investigates how the original metric system evolved into the International System of Units (SI), focusing on the meter, second, kilogram, and electrical units. (SK)