A Theoretical Foundation for the Laws of Conservation
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The four-element philosophers, including Empedocles (490–435 B.C.),
Pythagoras and his followers (from 5th century B.C. on), Philolaus (480 B.C.–
?), Plato (427–347 B.C.) and Aristotle (384–322 B.C.), claimed that there is not
one basic element but four: earth, water, air, and fire. The Egyptians had long
recognized four elements with qualities of male or female. For example, earth is
male when it has the form of boulders and crags; female when it is cultivable land.
When air is windy, it is male; when cloudy or sluggish, female. The Chinese,
as early as the 12th century B.C., had five elements, the previous four and wood,
together with five virtues, tastes, colors, tones, and seasons.
Among his physical ideas of matter, Aristotle introduced a fifth element. This
element cannot be “generated, corrupted, or transformed.” This pure, eternal, ethe-
real substance makes up the heavens and all their unchangeable objects. Beneath
the lunar sphere, the many products of the terrestrial four elements ceaselessly
transform. He pointed out that, although all substances of the four elements are
individually “generated, corrupted, and transformed, the universe as a whole is
ungenerated and indestructible.” Thus, in him a conservation of matter concept
can be found.
Anaxagoras (510–428 B.C.) in his “seeds” idea was unwilling to submerge
the tremendous varieties in things into any common denominator. He preferred
to accept the immediate diversity of things as is. With his philosophy, every
object is infinitely divisible. No matter how far an object is divided, what is left
would have characteristics of the original substance. That brings us to the very
interesting question of the transformation of matter. If all substances are derived
from unique seeds of themselves, how can one substance develop into another?
The contribution of Anaxagoras’ concept of seeds was its refinement, its idea
of taking substances as they are and breaking them down minutely in order to
know more about them. One main weakness of the concept is passing down the
complexities of a large-scale object to unseen miniatures of itself. Since these
miniatures were infinitely divisible, a fundamental unit was lacking.
The Leucippus–Democritus atom (500–55 B.C.) combined features of the
Ionian single element, Anaxagoras’ seeds, and Empedocles’ four elements and yet
was an improvement over all of them. “Atom” means “not divisible” in Greek.
This term was intentionally chosen by Democritus to emphasize a particle so small
that it could no longer be divided. To Leucippus and Democritus, the universe
originally and basically consisted entirely of atoms and a “void” in which atoms
moved. Eternally, the atom is indestructible and unchanging. Atoms are all of the
same substance, but by their various sizes and shapes, they can be used to explain
the large variety of objects they compose. Individual atoms, solid, eternal, and
indestructible, always maintain their identity in uniting or separating. It is the union
and separation of atoms that is temporary and that results in the transformation of
objects. The result is the principle of conservation of matter: Matter is neither
created nor destroyed but is transformed. However, after the atomists, the idea
of Plato and Aristotle on the nature of matter might seem almost an anticlimax.