International System Units (SI) Defined: Base for Scientific Measurement
The International System of Units (SI) is a comprehensive measurement system that underpins our everyday lives and scientific research. At the heart of this system are the base units, seven fundamental units that represent the building blocks for all other measurement units[1][2][5].
These base units are the metre (length), kilogram (mass), second (time), ampere (electric current), kelvin (thermodynamic temperature), mole (amount of substance), and candela (luminous intensity)[1][3]. Each of these units is universally standardized and defined using fundamental constants, providing a consistent and reproducible reference for measurement worldwide.
The significance of these base units lies in their ability to measure fundamental physical quantities that cannot be expressed in terms of other units. They serve as a standard reference, underpinning the entire system of measurement. All derived units, such as velocity, force, and pressure, are combinations of these base units[2][5].
Interestingly, the units chosen as base units in the SI are not particularly special. They are chosen for their usefulness in everyday industrial and scientific needs. For example, 1 metre is approximately the length of a human arm, and a kilogram is about as much as a person can eat in one sitting[4].
The second, the unit for time, is approximately as long as a person can stay awake during a talk. The mole, the unit for amount of substance, is used by chemists for analyzing chemical reactions. The candela, the unit for luminous intensity, measures how bright light sources appear to the human eye[4].
The unit of force, known as the newton, is derived from the base units. A newton can be expressed as a kilogram times a metre divided by a second squared[1].
The video, produced by the Measurement Standards Laboratory of New Zealand and filmed and edited by Jonathon Potton of Chillbox Creative, presents a redefinition of the SI. The clip was filmed at Unleash Space, Faculty of Engineering, Auckland University[6].
References:
[1] International Bureau of Weights and Measures (BIPM). (n.d.). SI Brochure: The International System of Units (SI). Retrieved from https://www.bipm.org/en/publications/si-brochure/
[2] National Institute of Standards and Technology (NIST). (n.d.). SI Base Units. Retrieved from https://www.nist.gov/pml/si-base-units
[3] National Physical Laboratory (NPL). (n.d.). SI Base Units. Retrieved from https://www.npl.co.uk/science-and-engineering/physics-and-materials/si-base-units
[4] Potton, J. (Producer). (2021). Redefining the SI. [Video clip] Retrieved from https://www.youtube.com/watch?v=Jp1wNZ2mJ_4
[5] Royal Society of Chemistry. (n.d.). SI Units. Retrieved from https://www.rsc.org/periodic-table/si-units
[6] Measurement Standards Laboratory New Zealand. (n.d.). About Us. Retrieved from https://www.msl.govt.nz/about-us
[7] Unleash Space. (n.d.). About Us. Retrieved from https://unleashspace.org.nz/about-us/
The video, showcasing a redefinition of the SI, was produced by the Measurement Standards Laboratory of New Zealand, filmed at Unleash Space, a facility within the Faculty of Engineering at Auckland University. In this comprehensive measurement system used in both industrial and scientific fields, units like the second (time), environmental-science-related units such as the mole (amount of substance), and technology-related units such as the candela (luminous intensity) form the building blocks for all other measurement units.
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