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ideas work above that distance. We should also add that the rules of the game
are the quantum-mechanical principles, and those principles apply, so far as we
can tell, to the new particles as well as to the old. "The origin of the forces In
nuelei leads us to new particles, but unfortunately they appear in great profusion
and we lack a complete understanding of their interrelationship, although we
already know that there are some very surprising relationships among them. We
seem gradually to be groping toward an understanding of the world of subatomic
particles, but we really do not know how far we have yet to go in this task.
--- Trang 69 ---
Tho Holeafforte of IPhịgsícs ío hon Scforeeos
3-1 Introduction
Physics is the most fundamental and all-inclusive of the sciences, and has had
a profound efect on all seientifc development. In fact, physics is the present-day
equivalent of what used to be called œ=ø‡ural philosophụ, from which most of our
mmodern sciences arose. Students of many fields ñnd themselves studying physics
because of the basic role it plays in all phenomena. In this chapter we shall
try to explain what the fundamental problems in the other sciences are, but of
course it is Impossible in so small a space really to deal with the complex, subtle,
beautiful matters in these other felds. Lack of space also prevents our discussing
the relation of physics to engineering, industry, society, and war, or even the
most remarkable relationship between mathematics and physics. (Mathematics is
not a science from our point of view, in the sense that it is not a nøÈurøÏ science.
The test of its validity is not experiment.) We must, incidentally, make it clear
from the beginning that iIf a thing is not a science, it is not necessarily bad. For
example, love is not a science. So, if something is said not to be a sclence, it does
not mean that there is something wrong with it; ¡9 just means that it is not a
Sclence.
3-2 Chemistry
The science which is perhaps the most deeply affected by physics is chemistry.
Historically, the early days of chemistry dealt almost entirely with what we now
call inorganic chemistry, the chemistry of substances which are not associated
with living things. Considerable analysis was required to discover the existence oŸ
the many elements and theïr relationships—how they make the various relatively
simple compounds found in rocks, earth, etc. This early chemistry was very
important for physics. 'Phe interaction between the two sciences was very great
--- Trang 70 ---
because the theory of atoms was substantiated to a large extent by experiments
in chemistry. “The theory of chemistry, i.e., of the reactions themselves, was
summarized to a large extent in the periodic chart of Mendeleev, which brings out
many strange relationships among the various elements, and it was the collection
of rules as to which substanece is combined with which, and how, that constituted
inorganic chemistry. All these rules were ultimately explained in principle by
quantum mechanics, so that theoretical chemistry 1s in fact physics. On the
other hand, it must be emphasized that this explanation is 7n pr/nciple. We have
already discussed the diference between knowing the rules of the game of chess,
and being able to play. So it is that we may know the rules, but we cannot play
very well. It turns out to be very dificult to predict precisely what will happen in
a given chemical reaction; nevertheless, the deepest part of theoretical chemistry
must end up in quantum mechanics.
There is also a branch of physics and chemistry which was developed by
both seiences together, and which is extremely important. This is the method
of statistics applied in a situation in which there are mechanical laws, which 1s
aptly called s¿aiistical mechanics. In any chemical situation a large number of
atoms are involved, and we have seen that the atoms are all jiggling around in
a very random and complicated way. If we could analyze each collision, and be
able to follow in detail the motion of each molecule, we might hope to figure out
what would happen, but the many numbers needed to keep track of all these
mmolecules exceeds so enormously the capacity of any computer, and certainly
the capacity of the mind, that it was important to develop a method for dealing
with such complicated situations. Statistical mechanics, then, is the science of
the phenomena. of heat, or thermodynamics. Inorganic chemistry is, as a science,
now reduced essentially to what are called physical chemistry and quantum
chemistry; physical chemistry to study the rates at which reactions occur and
what is happening in detail (How do the molecules hit? Which pieces fly of ñrst?,
etc.), and quantum chemistry to help us understand what happens in terms of
the physical laws.
The other branch of chemistry is organic cherm¿str, the chemistry of the
substances which are associated with living things. Eor a tỉme it was believed that
the substances which are associated with living things were so marvelous that
they could not be made by hand, from inorganic materials. "This is not at all true——
they are just the same as the substances made in inorganie chemistry, but more
complicated arrangements of atoms are involved. Organic chemistry obviously
has a very close relationship to the biology which supplies its substances, and
--- Trang 71 ---
to industry, and furthermore, much physical chemistry and quantum mechanics
can be applied to organic as well as to inorganie compounds. However, the main
problems of organic chemistry are not in these aspects, but rather in the analysis
and synthesis of the substances which are formed in biological systems, in living
things. This leads imperceptibly, in steps, toward biochemistry, and then into
biology itself, or molecular biology.
3-3 Biology
Thus we come to the seience of b2ology, which is the study of living things. In
the early days of biology, the biologists had to deal with the purely descriptive
problem of ñnding out uha¿‡ living things there were, and so they just had to
count such things as the hairs of the limbs of Heas. After these matters were
worked out with a great deal of interest, the biologists went into the rmachiner
inside the living bodies, fñrst from a gross standpoint, naturally, because it takes
some efort to get into the fñner details.
There was an interesting early relationship between physics and biology in
which biology helped physics in the discovery oŸ the conserualion oƒ energu, which
was frst demonstrated by Mayer in connection with the amount of heat taken in
and given out by a living creature.
Tf we look at the processes of biology of living animals more cÌosely, we see
man physical phenomena: the circulation of blood, pumps, pressure, etc. There
are nerves: we know what is happening when we step on a sharp stone, and
that somehow or other the information goes om the leg up. Ït is interesting
how that happens. In their study of nerves, the biologists have come to the
conclusion that nerves are very fñne tubes with a complex wall which is very
thin; through this wall the cell pumps lons, so that there are positive ions on the
outside and negative ions on the inside, like a capacitor. Now this membrane has