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posted by chromas on Monday May 20 2019, @07:42PM   Printer-friendly
from the progress-is-centimetering-along-nicely dept.

We measure stuff all the time – how long, how heavy, how hot, and so on – because we need to for things such as trade, health and knowledge. But making sure our measurements compare apples with apples has been a challenge: how to know if my kilogram weight or metre length is the same as yours.

Attempts have been made to define the units of measurement over the years. But today – International Metrology Day – sees the complete revision of those standards come into play.

You won't notice anything – you will not be heavier or lighter than yesterday – because the transition has been made to be seamless. Just the definitions of the seven base units of the SI (Système International d'Unités, or the International System of Units) are now completely different from yesterday.

[...] The challenge now though is to explain these new definitions to people – especially non-scientists – so they understand.

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  • (Score: 2) by maxwell demon on Tuesday May 21 2019, @07:01AM (1 child)

    by maxwell demon (1608) on Tuesday May 21 2019, @07:01AM (#845731) Journal

    Actually, the definition of the meter wasn't changed, only reformulated.

    FTFA:

    In the 2018 revision of the SI, the definitions of four of the SI base units – the kilogram, the ampere, the kelvin and the mole – were changed. Their new definitions are based on fixed numerical values of the Planck constant (h), the elementary charge (e), the Boltzmann constant (k), and the Avogadro constant (NA), respectively.

    Further, the definitions of all seven base units of the SI are now uniformly expressed using the explicit-constant formulation. Specific mises en pratique have been drawn up to explain the realization of the definitions of each of the base units in a practical way.

    --
    The Tao of math: The numbers you can count are not the real numbers.
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  • (Score: 2) by maxwell demon on Tuesday May 21 2019, @07:02AM

    by maxwell demon (1608) on Tuesday May 21 2019, @07:02AM (#845732) Journal

    Small correction: It wasn't TFA, but the second link in the quote.

    --
    The Tao of math: The numbers you can count are not the real numbers.