Essential idea: Since 1948, the Système International d’Unités (SI) has been used as the preferred language of science and technology across the globe and reflects current best measurement practice.

Nature of science: (1) Common terminology: Since the 18th century, scientists have sought to establish common systems of measurements to facilitate international collaboration across science disciplines and ensure replication and comparability of experimental findings. (2) Improvement in instrumentation: An improvement in apparatus and instrumentation, such as using the transition of cesium-133 atoms for atomic clocks, has led to more refined definitions of standard units. (3) Certainty: Although scientists are perceived as working towards finding “exact” answers, the unavoidable uncertainty in any measurement always exists.

Understandings:

Applications and skills:

• Using SI units in the correct format for all required measurements, final answers to calculations and presentation of raw and processed data

• Using scientific notation and metric multipliers

• Quoting and comparing ratios, values and approximations to the nearest order of magnitude

• Estimating quantities to an appropriate number of significant figures

Guidance:

• SI unit usage and information can be found at the website of Bureau International des Poids et Mesures

• Students will not need to know the definition of SI units except where explicitly stated in the relevant topics in this guide

• Candela is not a required SI unit for this course

• Guidance on any use of non-SI units such as eV, MeV c^-2, Ly and pc will be provided in the relevant topics in this guide

International-mindedness:

• Scientific collaboration is able to be truly global without the restrictions of national borders or language due to the agreed standards for data representation

Theory of knowledge:

• What has influenced the common language used in science? To what extent does having a common standard approach to measurement facilitate the sharing of knowledge in physics?

Utilization:

• This topic is able to be integrated into any topic taught at the start of the course and is important to all topics

• Students studying more than one group 4 subject will be able to use these skills across all subjects

• See Mathematical studies SL sub-topics 1.2–1.4

Aims:

• Aim 2 and 3: this is an essential area of knowledge that allows scientists to collaborate across the globe

• Aim 4 and 5: a common approach to expressing results of analysis, evaluation and synthesis of scientific information enables greater sharing and collaboration