Geoscience Reference
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be described statistically (movements, interactions at a distance and
collisions of quantum particles, atoms and molecules). We can, for
example, place this limit at the level of biological cells, the cells being
in some way the smallest macroscopic systems, but their contents are
relevant for much of the microscopic world (strictly speaking,
intracellular organelles are also macroscopic and the base sequences at
the heart of a gene on a strand of deoxyribonucleic acid (DNA) can be
described in a mechanistic way).
Another theoretical intermediate limit distinguishes isolated or
closed systems from open systems. It is this point that we will now
tackle.
1.1.3.
The Earth is a “closed” system
In thermodynamics, a system is called “isolated” when it does not
exchange energy nor matter with the outside world. The term “matter”
is theoretically useless here, when we consider that from a physicist's
point of view, according to Einstein's theory of general relativity,
matter is only a particular form of energy. This only accounts for the
principle of conservation of energy, matter being only an
approximation for the scales of time and space relevant to the life of
mankind or the history of humanity.
By virtue of the second law of thermodynamics, an isolated system
naturally evolves toward a situation of equilibrium, which is known as
“thermodynamic death”. In our own perceptions, such a system does
not exist because any attempt to observe it would, in fact, break its
isolation. It is therefore only theoretical and can only give rise to non-
refutable hypotheses whose scientific character can be discussed
[POP 62] (such as the cosmological hypothesis of multiverses where
universes evolve in isolation from one another).
Conversely, a system is called “open” when it exchanges energy
and matter with the outside world. In this case, the system can depart
from a situation of thermodynamic equilibrium to reach, eventually, a
stationary situation without equilibrium (regulation) whose
maintenance is assured by the transformation of a flux of energy during
