# A definition of a Kelvin – I'm sceptical!

I found this news on one of those insulting web climate extremist blogs which I read so that other people don’t have to.

Michael R. Moldover, Weston L. Tew & Howard W. Yoon

The past 25 years have seen tremendous progress in thermometry across the moderate temperature range of 1 K to 1,235 K. Various primary thermometers, based on a wide range of different physics, have uncovered errors in the International Temperature Scale of 1990, and set the stage for the planned redefinition of the kelvin.

Nature Physics 12, 7–11 (2016) doi:10.1038/nphys3618 07 January 2016

Rather than fixing the scale at the triple point of water,
The International Committee for Weights & Measures
recommends using the energy equivalent as given by Boltzmann’s equation .

Current definition:
The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.

Proposed redefinition:
The magnitude of the kelvin as the unit of thermodynamic temperature is to be set by fixing the numerical value of the Boltzmann constant to be equal to exactly 1.38065X×10−23 when it is expressed in the unit s−2·m2·kg·K−1, which is equal to J·K−1.

I’m surprised at the supposed “current definition” because last time I looked at this for the purposes of creating precision temperature calibration devices the standard was a hotch potch of methods. In some ranges it was based on PT100 thermometers, in others on gas bulb thermometers – in other words, temperature was neither defined by any fundamental physical relationship nor was it consistently defined through its range.
So, in principle I would support a unit based on fundamental physics but after decades watching the farcical non-science that has come from pursuing “theoretical” approaches to science which ignore the practical realities of what is actually needed, I am very sceptical whether this is being done because it is better – or because someone just feels it ought to be done despite the lack of any rhyme reason or improvement.

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### 1 Response to A definition of a Kelvin – I'm sceptical!

1. Nigel Boyle says:

I am very sceptical that anyone would ever understand it!