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as complicated as that, no matter where it is. Curiosity demands that we ask
questions, that we try to put things together and try to understand this multitude
Of aspects as perhaps resulting from the action of a relatively small number of
elemental things and forces acting in an infnite variety of combinations.
For example: Is the sand other than the rocks? That is, is the sand perhaps
nothing but a great number of very tiny stones? Is the moon a great rock? lf
we understood rocks, would we also understand the sand and the moon? Is the
wind a sloshing of the air analogous to the sloshing motion of the water in the
sea? What common features do diferent movements have? What is common to
diferent kinds of sound? How many diferent colors are there? And so on. In
this way we try gradually to analyze all things, to put together things which at
first sipht look diferent, with the hope that we may be able to reduce the number
Of đjƒerent things and thereby understand them better.
--- Trang 52 ---
A few hundred years ago, a method was devised to fnd partial answers to
such questions. seruation, reason, and ezperiment make up what we call the
sctentifltc mmethod. We shall have to limit ourselves to a bare description of our
basic view of what is sometimes called ƒundaœmnental phụsícs, or fundamental ideas
which have arisen from the application of the scientific method.
'What do we mean by “understanding” something? We can imagine that this
complicated array of moving things which constitutes “the world” is something
like a great chess game being played by the gods, and we are observers of the
game. We do not know what the rules of the game are; all we are allowed to do
1s tO œ0øứch the playing. Of course, iŸ we watch long enough, we may eventually
catch on to a few of the rules. The rules oƒ the game are what we mean by
fundamental phụsics. ven 1ƒ we knew every rule, however, we might not be able
to understand why a particular move is made in the game, merely because it is
too complicated and our minds are limited. If you play chess you must know
that it is easy to learn all the rules, and yet it is often very hard to select the
best move or to understand why a player moves as he does. So it is in nature,
only much more so; but we may be able at least to fñnd all the rules. Actually,
we do not have all the rules now. (Every once in a while something like castling
is going on that we still do not understand.) Aside from not knowing all oŸ the
rules, what we really can explain in terms of those rules is very limited, because
almost all situations are so enormously complicated that we cannot follow the
plays of the game using the rules, much less tell what is going to happen next.
Woe must, therefore, limit ourselves to the more basic question of the rules of the
game. lf we know the rules, we consider that we “understand” the world.
How can we tell whether the rules which we “guess” at are really right iŸ we
cannot analyze the game very well? There are, roughly speaking, three ways.
Pirst, there may be situations where nature has arranged, or we arrange nature,
to be simple and to have so few parts that we can predict exactly what will
happen, and thus we can check how our rules work. (In one corner of the board
there may be only a few chess pieces at work, and that we can fgure out exactly.)
A second good way to check rules is in terms of less specific rules derived from
them. For example, the rule on the move of a bishop on a chessboard is that 1t
moves only on the diagonal. One can deduce, no matter how many moves may
be made, that a certain bishop will always be on a red square. So, without being
able to follow the details, we can always check our idea about the bishop's motion
by fñnding out whether it is always on a red square. Of course it will be, for a long
tỉme, until all of a sudden we fñnd that it is on a biack square (what happened of
--- Trang 53 ---
course, is that in the meantime it was captured, another pawn crossed for queening,
and iÈ turned into a bishop on a black square). That is the way ïÈ is in physics.
For a long time we will have a rule that works excellently in an over-all way, even
when we cannot follow the details, and then some tỉme we may discOVer a nu
ru"e. From the point of view of basic physics, the most interesting phenomena,
are of course in the me places, the places where the rules do not work——not the
places where they đo workl "That is the way in which we discover new rules.
The third way to tell whether our ideas are right is relatively crude but
probably the most powerful of them all. 'That is, by rough approzzmafion. While
we may not be able to tell why Alekhine moves £Ö⁄4s particular piece, perhaps we
can rzøoughi understand that he is gathering his pieces around the king to protect
1t, more or less, since that is the sensible thing to do in the circumstances. In
the same way, we can often understand nature, more or less, without being able
to see what euerw liitle piece is doïng, ïn terms of our understanding of the game.
At first the phenomena of nature were roughly divided into classes, like heat,
electricity, mechanics, magnetism, properties of substances, chemical phenomena,
light or optics, x-rays, nuclear physics, gravitation, meson phenomena, etc.
However, the aim is to see cømplete nature as diferent aspects of one seÈ oŸ
phenomena. 'Phat is the problem in basic theoretical physics, today——to ƒnd
the laus behind ezperiment; to œmalgamate these classes. Historically, we have
always been able to amalgamate them, but as time goes on new things are found.
Woe were amalgamating very well, when all of a sudden x-rays were found. hen
we amalgamated some more, and mesons were found. 'Therefore, at any siage
of the game, it always looks rather messy. A great deal is amalgamated, but
there are always many wires or threads hanging out in all directions. That is the
situation today, which we shall try to describe.
Some historic exarmples of amalgamation are the following. First, take heat
and mechanics. When atoms are in motion, the more motion, the more heat the
system contains, and so hea£ and aÏÌ temperature e[ffects cœn be representcd bụ
the lats oƒ rmmechanics. Another tremendous amalgamation was the discovery of
the relation between electricity, magnetism, and light, which were found to be
diferent aspects of the same thing, which we call today the electrormnagnetic teld.
Another amalgamation is the unification of chemical phenomena, the various
properties of various substances, and the behavior of atomic particles, which 1s
in the quantwm rmmechanics oƑ chemistru.
The question is, of course, is it going to be possible to amalgamate euerwthing,
and merely discover that this world represents diferent aspects of ønme thing?
--- Trang 54 ---
NÑobody knows. All we know is that as we go along, we find that we can amalga-
mate pieces, and then we find some pieces that do not ft, and we keep trying to
put the jigsaw puzzle together. Whether there are a ñnite number of pieces, and
whether there is even a border to the puzzle, is of course unknown. It will never
be known until we fñnish the picture, If ever. What we wish to do here is to see
to what extent this amalgamation process has gone on, and what the situation
1s at present, in understanding basic phenomena in terms of the smallest set of
principles. 'To express ï§ in a simple manner, 0hœ‡ œre thứngs made öoƒ and hou)
ƒeu clements are there?
2-2 Physics before 1920