Full Idea
Thermometers assume the length of the fluid or gas is a function of temperature, and different substances yield different results. It was decided that different thermometers using the same substance should match, and air was the best, but not perfect.
Gist of Idea
Thermometers depend on the substance used, and none of them are perfect
Source
Reiss,J/Spreger,J (Scientific Objectivity [2014], 4.1)
Book Reference
'Stanford Online Encyclopaedia of Philosophy', ed/tr. Stanford University [plato.stanford.edu], p.17
A Reaction
[summarising Hasok Chang's research] This is a salutary warning that instruments do not necessarily solve the problem of objectivity, though thermometers do seem to be impersonal, and offer relative accuracy (i.e. ranking temperatures). Cf breathalysers.
Related Idea
Idea 6792 If theories need observation, and observations need theories, how do we start? [Bird]