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Physics, Astronomy & Cosmology / Re: Will refinement of measurement standards alter how we think of uncertainty?
« on: 21/11/2018 16:37:44 »
To expand a bit (now that my internet connection is a bit faster!)
If we measure something, we know that there are some uncertainties associated with the procedure itself, which will produce a different number if we repeat the experiment: these are random uncertainties. If we can separate out the random uncertainties to a set of independent uncertainties a, b, c in different parts of the measurement, we add them as though they are random noise, so the amplitude of the overall random or experimental uncertainty is √(a2 + b2 +c2...)
We also know that there are small discrepancies between the national standards or laboratory sub-standards of length, time, voltage, or whatever against which you and I make our individual measurements These contribute to the systematic uncertainty √x2+ y2+z2....) of our measurements.
Defining the units of measurement in terms of fundamental constants means that the systematic uncertainty of anyone's measurement is now reduced to the random uncertainty with which we have determined those constants, and the universal value is now fixed by definition and consensus rather than by reference to a lump of metal or whatever.
If we measure something, we know that there are some uncertainties associated with the procedure itself, which will produce a different number if we repeat the experiment: these are random uncertainties. If we can separate out the random uncertainties to a set of independent uncertainties a, b, c in different parts of the measurement, we add them as though they are random noise, so the amplitude of the overall random or experimental uncertainty is √(a2 + b2 +c2...)
We also know that there are small discrepancies between the national standards or laboratory sub-standards of length, time, voltage, or whatever against which you and I make our individual measurements These contribute to the systematic uncertainty √x2+ y2+z2....) of our measurements.
Defining the units of measurement in terms of fundamental constants means that the systematic uncertainty of anyone's measurement is now reduced to the random uncertainty with which we have determined those constants, and the universal value is now fixed by definition and consensus rather than by reference to a lump of metal or whatever.
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