Quincey, P G
(2016)
*Natural units in physics, and the curious case of the radian.*
Phys. Educ., 51 (6).
065012

## Abstract

Sets of natural units, like "atomic units", are sometimes used to simplify the equations of physics. This choice of units can be seen as a way of paring down equations to show the relationships between quantities in their simplest form, in specialised situations, while still being correct. The unit system used for teaching, the SI, is instead designed primarily to be a set of units that can be applied consistently across all areas of science and industry. The SI also gives priority to emphasising the distinction between different quantities, by (most of the time) giving different units to different quantities, rather than producing the simplest possible equations.

It is not widely appreciated that the SI treats the radian as the natural unit for angle, the only unit to be treated this way, with consequent issues for clear distinctions between quantities involving angles. The system that the SI would become if this anomaly were removed is presented. Rather than advocating this major change to the SI itself, it is proposed to highlight the existence of the underlying system to clarify how angles relate to physics, to make it easier to include angles in software calculations, and as an example of how the choice of unit system affects the equations we use.

Item Type: | Article |
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Keywords: | natural units, SI units, systems of measurement units, angle, radian |

Subjects: | Environmental Measurement Environmental Measurement > Air Quality and Airborne Particulates |

Identification number/DOI: | 10.1088/0031-9120/51/6/065012 |

Last Modified: | 02 Feb 2018 13:13 |

URI: | http://eprintspublications.npl.co.uk/id/eprint/7258 |

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