2
L. Rondoni
anymore: although nobody drunk it, it evaporated, leaving only dark stains in the
cup. Let some thousand years pass; even the table has deteriorated, and maybe the
cup like our city have undergone massive destruction, because of war, earthquakes,
hurricanes etc. Several billion years later, the Earth is vaporised by the explosion of
the Sun, and still later the Milky Way has undergone a destructive collision with the
Andromeda galaxy.
Has our coffee ever reached a stationary state? A state in which its physical
properties do not change in time? Has any of the small or large objects that we
mentioned ever been in a thermodynamic stationary state? Do stationary states exist?
Why is thermodynamic so much concerned with equilibrium states, a special kind
of stationary states?
Thermodynamics is a most successful branch of Physics describing macroscopic
objects, and Physics is the realm of quantitative—hence mathematical—theories
meant to describe and predict the being and becoming of natural phenomena. They
are motivated by the irresistible human drive to understand the existent and give life to
new realities. The formulation of a correct theory requires and inspires experiments
(not just experiences) that involve measurements of relevant quantities, in order
to test its validity. Measurements should then provide objective data, that become
intelligible within the mathematical framework constituting the theory. Objective
means that they do not depend on the observer, i.e. their significance stands for a
passer-by whether that person is aware or is not aware of the measurement: if water
in a pot is 90
◦ C hot, those immersing a hand in it will be burned, whether they knew
or did not know that a temperature measurement had previously been performed;
whether a measurement had been performed or not performed.
The goal of thermodynamics is to investigate the consequences of fundamental
principles such as the conservation of energy, the impossibility of perpetual motion,
etc. Its second law has been described by Lieb and Yngvason [1] as follows:
The second law of thermodynamics is, without a doubt, one of the most perfect laws in
physics. Any reproducible violation of it, however small, would bring the discoverer great
riches as well as a trip to Stockholm. The world’s energy problems would be solved at one
stroke. It is not possible to find any other law (except, perhaps, for super selection rules
such as charge conservation) for which a proposed violation would bring more skepticism
than this one. Not even Maxwell’s laws of electricity or Newton’s law of gravitation are so
sacrosanct, for each has measurable corrections coming from quantum effects or general
relativity. The law has caught the attention of poets and philosophers and has been called
the greatest scientific achievement of the nineteenth century.
Describing the behaviour of matter at the scale of our daily life—what we call the
macroscopic world—not all kinds of measurements are of thermodynamic concern;
only measurements that can be performed with certain tools, following certain protocols are considered. This should be understood, because measurement tools and
protocols necessarily affect the picture of reality one gets. Indeed, different measurement tools probe different properties of reality, and yield different descriptions of
even the very same objects. Wearing glasses that allow only radiation around 510–
530 THz makes the whole world look either yellow or black. Other glasses yield a
different picture.
L. Rondoni
anymore: although nobody drunk it, it evaporated, leaving only dark stains in the
cup. Let some thousand years pass; even the table has deteriorated, and maybe the
cup like our city have undergone massive destruction, because of war, earthquakes,
hurricanes etc. Several billion years later, the Earth is vaporised by the explosion of
the Sun, and still later the Milky Way has undergone a destructive collision with the
Andromeda galaxy.
Has our coffee ever reached a stationary state? A state in which its physical
properties do not change in time? Has any of the small or large objects that we
mentioned ever been in a thermodynamic stationary state? Do stationary states exist?
Why is thermodynamic so much concerned with equilibrium states, a special kind
of stationary states?
Thermodynamics is a most successful branch of Physics describing macroscopic
objects, and Physics is the realm of quantitative—hence mathematical—theories
meant to describe and predict the being and becoming of natural phenomena. They
are motivated by the irresistible human drive to understand the existent and give life to
new realities. The formulation of a correct theory requires and inspires experiments
(not just experiences) that involve measurements of relevant quantities, in order
to test its validity. Measurements should then provide objective data, that become
intelligible within the mathematical framework constituting the theory. Objective
means that they do not depend on the observer, i.e. their significance stands for a
passer-by whether that person is aware or is not aware of the measurement: if water
in a pot is 90
◦ C hot, those immersing a hand in it will be burned, whether they knew
or did not know that a temperature measurement had previously been performed;
whether a measurement had been performed or not performed.
The goal of thermodynamics is to investigate the consequences of fundamental
principles such as the conservation of energy, the impossibility of perpetual motion,
etc. Its second law has been described by Lieb and Yngvason [1] as follows:
The second law of thermodynamics is, without a doubt, one of the most perfect laws in
physics. Any reproducible violation of it, however small, would bring the discoverer great
riches as well as a trip to Stockholm. The world’s energy problems would be solved at one
stroke. It is not possible to find any other law (except, perhaps, for super selection rules
such as charge conservation) for which a proposed violation would bring more skepticism
than this one. Not even Maxwell’s laws of electricity or Newton’s law of gravitation are so
sacrosanct, for each has measurable corrections coming from quantum effects or general
relativity. The law has caught the attention of poets and philosophers and has been called
the greatest scientific achievement of the nineteenth century.
Describing the behaviour of matter at the scale of our daily life—what we call the
macroscopic world—not all kinds of measurements are of thermodynamic concern;
only measurements that can be performed with certain tools, following certain protocols are considered. This should be understood, because measurement tools and
protocols necessarily affect the picture of reality one gets. Indeed, different measurement tools probe different properties of reality, and yield different descriptions of
even the very same objects. Wearing glasses that allow only radiation around 510–
530 THz makes the whole world look either yellow or black. Other glasses yield a
different picture.