• jballs
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    1 year ago

    Exactly. Just as every kid learns in kindergarten. A kilogram is the weight of 1,000 cubic cms of water. A liter is the volume of 1 kilogram of water. And a second is the fixed numerical value of the caesium frequency, ΔνCs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9192631770 when expressed in the unit Hz, which is equal to s−1.