25
2.5.2 Zeroth Law of Thermodynamics
Many other things are exceedingly difficult to measure as well. Qualitative or
ephemeral experiences, for instance, defy direct and precise quantification.
Psychological states, aesthetic effects, and changing public opinion, for instance,
can only be described or approximated with heavily qualified statements.
Temperature, however, is measurable once a scale is agreed upon and standardized
instruments are properly calibrated.
The Zeroth Law of Thermodynamics was formalized and labeled in 1935 by the
British physicist Ralph Fowler after the first three laws were already formulated. It
definitively establishes the transitive relation (if A = B and B=C, then A = C)
between thermal systems in order to measure heat. It says that if two thermodynamic systems are each in thermal equilibrium with a third, then they are in equilibrium with each other.
This is important because temperature is an abstract notion. Humans are well
adapted to survive in a thermally active or variable environment. Thermoreceptors
in our skin respond to “hotter than” and “colder than” stimuli as subjective sensations. Our innate physiological grasp of thermal differences, though, cannot provide
a common notion of temperature. Beyond the general subjective and qualitative
nature of human sense perception of thermal energy, sensitivity varies between individuals, and even depends on which part of the body does the sensing, and it generally decreases with age (Stevens and Choo 1998).
Thermometers were invented to express the amount of heat as a quantitative,
numerical representation. The Zeroth Law recognizes the fundamental need to use
and trust instruments to provide a common understanding of the precise amount of
heat in an object or system. In light of today’s challenges to trust stated scientific
facts created in a cultural environment where everything is relative and open to
interpretation, it may help to generalize and extend the Zeroth Law to other instruments of measure where applicable and where enough equivalencies are available to
establish a standard for calibration.
Agreement between various instruments displaying environmental impact information is discussed in Chaps. 7, 8, and 9. In contrast to the complexities inherent in
compound, multistage, and multi-metric analysis such as life cycle assessment,
temperature is a relatively straightforward single indicator. Temperature, nevertheless, requires an agreed upon faith in the accuracy, precision, and overall veracity of
instrumental readout. Most importantly, it depends on the significance and utility of
the information gleaned every time a thermometer is consulted (Fig. 2.1).
When the mercury in a thermometer stops rising or falling, it has achieved thermal equilibrium with the substance it is measuring. If the reading doesn’t change
from one thermodynamic system to another, it is accepted that they are each in
thermal equilibrium with the other. It is so commonplace today that few would now
question the once abstract concept of temperature. Even the most ardent science
denier acquiesces to the Zeroth Law at least tacitly and doesn’t question the underlying faith we each place in measuring the rate at which molecules are moving in a
substance in contact with the surface of the thermometer.
2.5 Sadi Carnot’s Caloric Thermal Energy
2.5.2 Zeroth Law of Thermodynamics
Many other things are exceedingly difficult to measure as well. Qualitative or
ephemeral experiences, for instance, defy direct and precise quantification.
Psychological states, aesthetic effects, and changing public opinion, for instance,
can only be described or approximated with heavily qualified statements.
Temperature, however, is measurable once a scale is agreed upon and standardized
instruments are properly calibrated.
The Zeroth Law of Thermodynamics was formalized and labeled in 1935 by the
British physicist Ralph Fowler after the first three laws were already formulated. It
definitively establishes the transitive relation (if A = B and B=C, then A = C)
between thermal systems in order to measure heat. It says that if two thermodynamic systems are each in thermal equilibrium with a third, then they are in equilibrium with each other.
This is important because temperature is an abstract notion. Humans are well
adapted to survive in a thermally active or variable environment. Thermoreceptors
in our skin respond to “hotter than” and “colder than” stimuli as subjective sensations. Our innate physiological grasp of thermal differences, though, cannot provide
a common notion of temperature. Beyond the general subjective and qualitative
nature of human sense perception of thermal energy, sensitivity varies between individuals, and even depends on which part of the body does the sensing, and it generally decreases with age (Stevens and Choo 1998).
Thermometers were invented to express the amount of heat as a quantitative,
numerical representation. The Zeroth Law recognizes the fundamental need to use
and trust instruments to provide a common understanding of the precise amount of
heat in an object or system. In light of today’s challenges to trust stated scientific
facts created in a cultural environment where everything is relative and open to
interpretation, it may help to generalize and extend the Zeroth Law to other instruments of measure where applicable and where enough equivalencies are available to
establish a standard for calibration.
Agreement between various instruments displaying environmental impact information is discussed in Chaps. 7, 8, and 9. In contrast to the complexities inherent in
compound, multistage, and multi-metric analysis such as life cycle assessment,
temperature is a relatively straightforward single indicator. Temperature, nevertheless, requires an agreed upon faith in the accuracy, precision, and overall veracity of
instrumental readout. Most importantly, it depends on the significance and utility of
the information gleaned every time a thermometer is consulted (Fig. 2.1).
When the mercury in a thermometer stops rising or falling, it has achieved thermal equilibrium with the substance it is measuring. If the reading doesn’t change
from one thermodynamic system to another, it is accepted that they are each in
thermal equilibrium with the other. It is so commonplace today that few would now
question the once abstract concept of temperature. Even the most ardent science
denier acquiesces to the Zeroth Law at least tacitly and doesn’t question the underlying faith we each place in measuring the rate at which molecules are moving in a
substance in contact with the surface of the thermometer.
2.5 Sadi Carnot’s Caloric Thermal Energy