7
sense more directly observable, by means of instruments that were designed as
nomological machines (Cartwright, 1999).
The ceteris paribus condition is critical for the characterization of the transduction effect, given the dependency of the transduced height on the context—air pressure in particular—and the instrument’s features, including the kind of liquid used
and the material of which the tube is made (typically some sort of glass). It was only
on the basis of such a condition that fixed points were discovered, so that, e.g.,
ceteris paribus, water boils always at the same temperature. This was a fundamental
enabler of the establishment of scales of temperature, which were initially created
without a strong theoretical understanding of temperature and its relation to thermal
expansion, and instead were mainly based on models of data, typically with the
assumption of linearity of values between the fixed points (Bringmann & Eronen,
2015). The compatibility of the results produced by different instruments was hard
to achieve, and in consequence so was the construction of a socially agreed thermometric scale (Celsius and Fahrenheit being only the two remnants of a larger set of
once-proposed scales). But this multiplicity of instruments, able to produce at least
partially compatible results, also helped advance our knowledge of temperature: the
observed transduction effects implemented in different instruments share a common
cause, which is also the same physical property that we perceive and describe in
terms of warmer or colder. This standpoint was further supported by the discovery
of other temperature-related transduction effects, independent of thermal expansion, for example the thermoelectric effect, such that differences of temperature are
transduced to differences of electric potential (i.e., voltage). The hypothesis of the
existence of temperature, as the cause of multiple, independent but correlated
effects, was thus strongly corroborated.
Temperature has some other interesting features for our conceptual metrological
perspective. It is an intensive property, i.e., “one that is independent of the quantity
of matter being considered”
7
(the temperature of a thermally homogeneous body
does not change by removing a part of the body), and nevertheless it has a fundamental connection with several additive/extensive properties, and in particular heat
energy, which spontaneously flows from bodies at a higher temperature to bodies at
a lower temperature. Moreover, the temperature of a gas is equivalent to the average
kinetic energy of its molecules, where thus a property at the macroscopic level (temperature) is explained in terms of a property at the microscopic level (molecular
kinetic energy).
Finally, the measurement of temperature and its development are also interesting
with respect to scale types. While historically temperature was considered to be
only an ordinal property, the scientific and technological advances resulting from
the adoption of the experimental method led to thermometric scales (including the
previously mentioned Celsius and Fahrenheit scales), which are interval scales,
because of the lack of knowledge of a “natural zero”, common to all scales. (Compare
to the case of length and mass: even though many scales of length and mass were
7 www.britannica.com/science/temperature.
1.2 Some familiar and not-so-familiar contexts for measurement
sense more directly observable, by means of instruments that were designed as
nomological machines (Cartwright, 1999).
The ceteris paribus condition is critical for the characterization of the transduction effect, given the dependency of the transduced height on the context—air pressure in particular—and the instrument’s features, including the kind of liquid used
and the material of which the tube is made (typically some sort of glass). It was only
on the basis of such a condition that fixed points were discovered, so that, e.g.,
ceteris paribus, water boils always at the same temperature. This was a fundamental
enabler of the establishment of scales of temperature, which were initially created
without a strong theoretical understanding of temperature and its relation to thermal
expansion, and instead were mainly based on models of data, typically with the
assumption of linearity of values between the fixed points (Bringmann & Eronen,
2015). The compatibility of the results produced by different instruments was hard
to achieve, and in consequence so was the construction of a socially agreed thermometric scale (Celsius and Fahrenheit being only the two remnants of a larger set of
once-proposed scales). But this multiplicity of instruments, able to produce at least
partially compatible results, also helped advance our knowledge of temperature: the
observed transduction effects implemented in different instruments share a common
cause, which is also the same physical property that we perceive and describe in
terms of warmer or colder. This standpoint was further supported by the discovery
of other temperature-related transduction effects, independent of thermal expansion, for example the thermoelectric effect, such that differences of temperature are
transduced to differences of electric potential (i.e., voltage). The hypothesis of the
existence of temperature, as the cause of multiple, independent but correlated
effects, was thus strongly corroborated.
Temperature has some other interesting features for our conceptual metrological
perspective. It is an intensive property, i.e., “one that is independent of the quantity
of matter being considered”
7
(the temperature of a thermally homogeneous body
does not change by removing a part of the body), and nevertheless it has a fundamental connection with several additive/extensive properties, and in particular heat
energy, which spontaneously flows from bodies at a higher temperature to bodies at
a lower temperature. Moreover, the temperature of a gas is equivalent to the average
kinetic energy of its molecules, where thus a property at the macroscopic level (temperature) is explained in terms of a property at the microscopic level (molecular
kinetic energy).
Finally, the measurement of temperature and its development are also interesting
with respect to scale types. While historically temperature was considered to be
only an ordinal property, the scientific and technological advances resulting from
the adoption of the experimental method led to thermometric scales (including the
previously mentioned Celsius and Fahrenheit scales), which are interval scales,
because of the lack of knowledge of a “natural zero”, common to all scales. (Compare
to the case of length and mass: even though many scales of length and mass were
7 www.britannica.com/science/temperature.
1.2 Some familiar and not-so-familiar contexts for measurement