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the mystery to know a little about it. Eor far more marvelous is the truth than any artists of
the past imaginedl Why do the poets of the present not speak of it? What men are poets who
can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane
and ammonia must be silent?
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was out with his girl friend the night after he realized that nœuclear reaclions
must be going on in the stars in order to make them shine. She said “Look at
how pretty the stars shinel” He said “Yes, and right now I am the only man in
the world who knows h# they shine.” She merely laughed at him. She was not
impressed with being out with the only man who, at that moment, knew why
stars shine. Well, it is sad to be alone, but that is the way it is in this world.
Tt is the nuclear “burning” of hydrogen which supplies the energy of the sun;
the hydrogen is converted into helium. Eurthermore, ultimately, the manufacture
Of various chemical elements proceeds in the centers of the stars, from hydrogen.
'The stuff of which +e are made, was “cooked” once, in a star, and spit out. How
do we know? Because there is a clue. The proportion of the diferent isotopes——
how much C†?, how much CÌỞ, etc., is something which is never changed by
chemical reactions, because the chemical reactions are so mụch the same for the
two. The proportions are purely the result oŸ uclear reactions. By looking
at the proportions of the isotopes in the cold, dead ember which we are, we
can discover what the ƒurznace was like in which the stuf of which we are made
was formed. That furnace was like the stars, and so it is very likely that our
elements were “made” in the stars and spit out in the explosions which we call
novae and supernovae. Astronomy is so close to physics that we shall study many
astronomical things as we go along.
3-5 Goeology
We© turn now to what are called earth sciences, or geologụ. First, meteorology
and the weather. Of course the wstruwments of meteorology are physical instru-
ments, and the development of experimental physics made these instruments
possible, as was explained before. However, the theory of meteorology has never
been satisfactorily worked out by the physicist. “Well,” you say, “there is nothing
but aïr, and we know the equations of the motions of air.” Yes we do. “So 1Í we
know the condition of air today, why can't we figure out the condition oŸ the air
tomorrow?” Eirst, we do not rzeallu know what the condition is today, because
the air is swirling and twisting everywhere. It turns out to be very sensitive, and
even unstable. If you have ever seen water run smoothly over a dam, and then
turn into a large number of blobs and drops as it falls, you wiïll understand what
Ï mean by unstable. You know the condition of the water before it goes over the
spillway; 1È is perfectly smooth; but the moment it begins to fall, where do the
drops begin? What determines how big the lumps are goïng to be and where
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they will be? That is not known, because the water is unstable. ven a smooth
mmoving mass 0Ý air, in going over a mountain turns into complex whirlpools and
eddies. In many fields we fñnd this situation of #wrbulent fiou that we cannot
analyze today. Quickly we leave the subject of weather, and discuss geologyl
The question basic to geology is, what makes the earth the way it is? 'Phe
most obvious processes are in front of your very eyes, the erosion processes of
the rivers, the winds, etc. Ït is easy enough to understand these, but for every
bit of erosion there is an equal amount of something else going on. Mountains
are no lower today, on the average, than they were in the past. There must
be mountain- forrming processes. You will ñnd, if you study geology, that there
re mountain-forming processes and volcanism, which nobody understands but
which is half of geology. The phenomenon of volcanoes is really not understood.
What makes an earthquake is, ultimately, not understood. It is understood
that 1ƒ something is pushing something else, it snaps and will slide—that is all
ripht. But what pushes, and why? The theory is that there are currents inside
the earth—circulating currents, due to the diference in temperature inside and
outside—which, in their motion, push the surface slightly. Thus if there are two
opposite circulations next to each other, the matter will collect in the region
where they meet and make belts of mountains which are in unhappy stressed
conditions, and so produce volcanoes and earthquakes.
'What about the inside of the earth? A great deal is known about the speed of
cearthquake waves through the earth and the density of distribution of the earth.
However, physicists have been unable to get a good theory as to how dense a
substance should be at the pressures that would be expected at the center of the
earth. In other words, we cannot fñgure out the properties of matter very well in
these circumstances. We do much less well with the earth than we do with the
conditions of matter in the stars. The mathematics involved seems a little too
dificult, so far, but perhaps it will not be too long before someone realizes that
1t is an important problem, and really works it out. The other aspect, of course,
is that even iƒ we did know the density, we cannot fgure out the circulating
currents. Nor can we really work out the properties of rocks at high pressure.
W© cannot tell how fast the rocks should “give”; that must all be worked out by
experIment.
3-6 Psychology
Next, we consider the science of ps/chology. Incidentally, psychoanalysis
1s not a science: i§ is at best a medical process, and perhaps even more like
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witch-doctoring. It has a theory as to what causes disease—lots of different
“spirits,” etc. The witch doctor has a theory that a disease like malaria is caused
by a spirit which comes into the air; i§ is not cured by shaking a snake over it,
but quinine does help malaria. So, If you are sick, Ï would advise that you go to
the witch doctor because he is the man in the tribe who knows the most about
the disease; on the other hand, his knowledge is not science. Psychoanalysis has
not been checked carefully by experiment, and there is no way to fnd a list of
the number of cases in which it works, the number of cases in which it does not
WOrk, ©WC.
The other branches of psychology, which involve things like the physiology
of sensation——what happens in the eye, and what happens in the brain—are, If
you wish, less interesting. But some small but real progress has been made in
studying them. One of the most interesting technical problems may or may not
be called psychology. The central problem of the mind, if you will, or the nervous
system, is this: when an animal learns something, it can do something diferent
than i% could before, and its brain cell must have changed too, if it is made out
of atoms. nw +0ha£t tuay is ?t djƒerent? We do not know where to look, or what
%o look for, when something is memorized. We do not know what iÿ means, or
what change there is in the nervous system, when a fact is learned. 'This is a
very important problem which has not been solved at all. Assuming, however,
that there is some kind of memory thing, the brain is such an enormous mass
of interconnecting wires and nerves that it probably cannot be analyzed in a