The theory of Democritus and Leucippus held that everything
is composed of "atoms", which are physically, but not geometrically,
indivisible; that between atoms lies empty space; that atoms are
indestructible; have always been, and always will be, in motion; that there are
an infinite number of atoms, and kinds of atoms, which differ in shape, and
size. Of the mass of atoms, Democritus said "The more any indivisible
exceeds, the heavier it is." But his exact position on weight of atoms is
disputed.[1]
Democritus, along with Leucippus and Epicurus,
proposed the earliest views on the shapes and connectivity of atoms. They
reasoned that the solidness of the material corresponded to the shape of the
atoms involved. Thus, iron atoms are solid and strong with hooks that lock them
into a solid; water atoms are smooth and slippery; salt atoms, because of their
taste, are sharp and pointed; and air atoms are light and whirling, pervading
all other materials.[28] Democritus
was the main proponent of this view. Using analogies from our sense
experiences, he gave a picture or an image of an atom that distinguished them
from each other by their shape, their size, and the arrangement of their parts.
Moreover, connections were explained by material links in which single atoms
were supplied with attachments: some with hooks and eyes others with balls and
sockets.[29]
The Democritean atom is an inert solid (merely excluding
other bodies from its volume) that interacts with other atoms mechanically. In contrast, modern,
quantum-mechanical atoms interact via electric and magnetic force fields and
are far from inert.
Lucretius, describing atomism in his De
rerum natura gives very clear and compelling empirical arguments for
the original atomist theory. He observes that any material is subject to
irreversible decay. Through time, even hard rocks are slowly worn down by drops
of water. Things have the tendency to get mixed up: mix water with soil and you
get mud, that will usually not un-mix by itself. Wood decays. However, we see
in nature and technology that there are mechanisms to recreate 'pure' materials
like water, air, metals. The seed of an oak will grow out into an oak
tree, made of similar wood as historical oak trees, the wood of which has
already decayed.
The conclusion is that many properties of materials must
derive from something inside, that will itself never decay, something that
stores for eternity the same inherent, indivisible properties. The basic
question is: why has everything in the world not yet decayed, and how can
exactly the same materials, plants, animals be recreated again and again? One
obvious solution to explain how indivisible properties can be conveyed in a way
not easily visible to human senses, is to hypothesize the existence of 'atoms'.
These classical 'atoms' are nearer to our modern concept of 'molecule' than to
the atoms of modern science. The other big point of classical atomism is that
there must be a lot of open space between these 'atoms': the void. Lucretius
gives reasonable arguments that the void is absolutely necessary to
explain how gasses and fluids can change shape, flow, while metals can be
molded, without changing the basic material properties.
The atomistic void hypothesis was a response to the
paradoxes of Parmenides and Zeno,
the founders of metaphysical logic, who put forth difficult to answer arguments
in favor of the idea that there can be no movement. They held that any movement
would require a void—which is nothing—but a nothing cannot exist. The
Parmenidean position was "You say there 'is' a void; therefore the void is
not nothing; therefore there is not the void."
The atomists agreed that motion required a void, but simply
ignored the argument of Parmenides on the grounds that motion was an observable
fact. Therefore, they asserted, there must be a void.
[…]
No comments:
Post a Comment