234 DOC. 20 THEORETICAL ATOMISM
interpret
the law of
energy
balance
as
indicating
that there exists
basically
only one
kind of
energy,
no
matter
how diverse the external manifestations of this
energy
might
be.
For
such
a conception
makes
it
possible
to
understand the law of
conservation of
energy, i.e.,
to
obtain
it
as a
consequence
of the
general
foundations
of
the
theory,
which
appears impossible
on
the
assumption
of
fundamentally
different
kinds of
energy.
Today's physicists
would also consider the reduction of
all
kinds of
energy
to
one
single
kind
as a
highly significant
advance,
but
they
have
no
hopes
of
being
able
to
attain
this
goal
in
the foreseeable future.
People
were more
confident, however,
around the middle of the last
century. Up
to
that time mechanics had
played
such
a
privileged
role
in
the
development
of
physics
that the
assumption
of the
unitary
character of
energy was inseparably
bound
in
the minds of the
physicists
of
those
days
with the
assumption
that
this
unitary energy
must
be conceived
as
mechanical
energy.
Hence
they
were
firmly
convinced that in the final
analysis
all
processes
are
to
be conceived
as
mechanical
processes.
In
the introduction
to
his
essay
of
fundamental
importance,
"Uber die
Erhaltung
der Kraft"
(1847),
H.
Helmholtz
expressed
this
conviction
in
the
following
words: "In the final
analysis,
the task of
the
physical
sciences
is to
reduce natural
phenomena
to
invariant attractive and
repulsive
forces,
the
intensity
of which
depends
on
the distance. The
solvability
of
this
problem
is at
the
same
time the condition for the
complete comprehensibility
of
[2]
nature."
Today we can
state
with
certainty
that this
conviction,
which
was
still,
without
qualification,
the
prevalent one a
few decades
ago,
cannot
be maintained
to its full
extent.
But
it is
now
less
possible
than before
to
deny
that
a
large portion
of
physical
phenomena
can
be reduced
to
mechanical
processes
in
a
highly satisfactory
manner.
It is to
this conviction
regarding
the fundamental
significance
of mechanics for
theoretical
physics
that
we
owe,
first and
foremost,
the kinetic
theory
of
heat,
the
[3]
most
important
features of whose
development
shall be sketched
in
what follows.
I
will
not
always
follow the historical
course
of
development,
which has been
determined
to
a
great
extent
by
the
temporal sequence
in
which certain mathematical
difficulties
were overcome.
Right from the beginning, the kinetic theory of matter borrowed the molecular
theory from chemistry and crystallography. According
to
this theory,
all
physical
substances consist of certain particles of finite size (molecules), which can move only
as a
whole and
are
endowed with
properties
that
are
in
essence
conceived of
as
being
similar
to
those of the solid bodies of
our experience.
Each such molecule consists
of
atoms-as
a
rule,
of
just
a
few atoms. The
skeptical
reader will
now
think that
all
that the molecular
theory probably accomplishes
is
simply
to transfer
to
the
molecules
the
qualities
with which
we
have become
acquainted
in
the bodies from
our
world
of
experience.
It is
of
great importance
here
to
show
that
this
is not
the
case.
Fundamental
Hypotheses of
the Kinetic
Theory
of
Heat.