The Metre Is Defined Through the Speed of Light
At the 1983 General Conference on Weights and Measures, concluding October 21, delegates adopted a definition of the metre tied to the speed of light.
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A New Standard for Length
At the 1983 General Conference on Weights and Measures, concluding October 21, delegates adopted a definition of the metre tied to the speed of light.
From an Object to a Physical Constant
The new formulation replaced the previous krypton-radiation definition. It linked length to the distance light travels in vacuum during a specified fraction of a second.
Why Change the Definition?
Improved lasers and frequency measurements made the new approach more reproducible. A measurement standard must be realizable in laboratories, not merely memorable in a textbook.
The Length Did Not Suddenly Change
Redefinition did not make ordinary rulers longer or shorter. Its purpose was to improve the foundation and precision of measuring the same unit.
An International Agreement
The resolution demonstrates how scientific standards depend on coordinated decisions. A constant of nature becomes useful in measurement through agreed definitions and practical methods.
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