Science in the Making 9780231890182

Citation preview

Science IN THE MAKING

Science IN THE MAKING J O E L H. H I L D E B R A N D

Sili? COLUMBIA

New York and London

UNIVERSITY

PRESS

T H E L E C T U R E S IN THIS BOOK W E R E ORIGINALLY AT C O L U M B I A U N I V E R S I T Y

IN

DELIVERED

1956

AS THE NINTH IN T H E SERIES KNOWN AS THE BAMPTON L E C T U R E S IN AMERICA

COPYRIGHT ©

1957

COLUMBIA UNIVERSITY PRESS, NEW

COLUMBIA

P A P E R B A C K EDITION

1962

MANUFACTURED IN THE UNITED STATES OF A M E R I C A

YORK

CONTENTS

THE SEARCH FOR KNOWLEDGE

FALSE PATHS

SCIENCE HAS ITS CATHEDRALS

KNOWLEDGE AND POWER

NOTES

FIGURES

1.

AN EXAMPLE OF SCIENTIFIC ANALOGY

2.

ABSORPTION OF LIGHT BY IODINE

11

3.

SOLUBILITY OF IODINE, I92O

15

4.

SOLUBILITY OF IODINE, 1956

16

5.

IMAGINARY CROSS SECTION OF A LIQUID

18

6.

DISTRIBUTION FUNCTIONS OF XENON AND ARGON

19

7.

LINEARITY OF SOLUBILITY CURVES

25

8.

THE PERIODIC SYSTEM, 1947 AND 1952

43

9.

FREQUENCY OF OCCURRENCE OF ODD AND EVEN NUMBERS AMONG TWELVE DICE

10.

49

ELECTRIC CELL UTILIZING THE REACTION,

Zn + C u + + = Z n + + + Cu 12.

48

FREQUENCY DISTRIBUTION OF HEIGHTS AMONG 18,750 MEN

11.

8

65

ELECTRIC CELL FOR THE REACTION,

Pb + Br2 = PbBr2

79

Science IN THE MAKING

THE SEARCH FOR KNOWLEDGE

novel, The Romance of Leonardo da Vinci, by Merezhkovski, there is an account of a "Duel of Learning" that took place at the court of Duke Ludovico il Moro in Milan in the year 1498. There were gathered "sundry doctors, deans, and magisters of the University of Pavia, in quadrangular red caps, in scarlet silk capes, lined with ermine, in gloves of violet chamois, with gold-embroidered pouches at their belts. The ladies of the court were in gorgeous ball apparel. At Moro's feet, on either side of his throne, sat Madonna Lucrezia and Countess Cecilia." The "Duel" began with a theological debate on the Immaculate Conception of the Virgin Mary. Next came a medical disputation upon questions such as these: Are handsome women more prolific than homely ones? Was the healing of Tobith with fish gall natural? Is woman an imperfect creation of nature? "A philosophical contest followed as to whether the very first matter of all were multiform or unique." The debate waxed loud and acrimonious. Soon the Countess Cecilia proposed to the Duke that he ask Leonardo to take part in the tourney. Leonardo begged to be excused, but the ladies importuned him. They suggested topics: "Tell us how men shall fly," said I N THE GREAT HISTORICAL

4

SCIENCE

IN

THE

MAKING

one; "of magic would be better," said another; "of black magic . . . . of necromancy . . . . something as awful as possible—and no mathematics." Leonardo reluctantly yielded. His topic was sea shells. He began telling them of "the petrified marine animals, the imprints of seaweeds and corals, found in caves and mountains . . . witnesses of how, since times immemorially ancient, the face of the earth had changed." He concluded his exposition by saying, "I am positive that the study of fossilized animals and plants, which has hitherto been despised by men of science, will give us the beginning of a new science of the earth, of her past and her future." His exposition was received with hostility. One man, a feeble old dean, would not take him seriously because he was neither a doctor nor a magister, merely an artist. The rector of the university preferred to explain the existence of fossil shells high on the sides of mountains as the work of the universal deluge. Leonardo skillfully explained why this could not be. The court astrologer proposed his solution, that the petrifactions had been "formed by the magical action of the stars." Leonardo refuted this likewise. An old doctor of scholastics then took the floor; he maintained that "the disputation was being carried on improperly," because "either the problem . . . belonged to the lower, 'mechanical,' knowledge, foreign to metaphysics, in which case there was nothing to be said of it, inasmuch as they had not convened here to contend over subjects not related to philosophy, or else the problem was related to the true, higher knowledge,—to dialectics; in such case, it must

THE

SEARCH

FOR

KNOWLEDGE

5

even be discussed in accordance with the laws of dialectics, raising the subjects to pure mental contemplation." "There is no higher or lower knowledge," Leonardo replied, "but one only, flowing out of experimentation." Of the metaphysics of Aristotle, of Plato, of Plotinus, he said, "In science they have taken the false path. They desired to fathom that which is inaccessible to knowledge, while that which was accessible they contemned. They have entangled themselves and others for many ages. For, in considering subjects not open to proof, men cannot come to any agreement. Where there are no sensible deductions, their place is taken by shouts. But he that knoweth hath no need of shouting." Upon this bedlam broke loose, but Leonardo was silent. "He perceived his isolation among these people, . . . saw the uncrossable abyss that separated them from him." That abyss, so dramatically depicted by Merezhkovski, is no longer uncrossable, but it is still deep enough to present a formidable obstacle to common understanding. Prejudice and passion still intrude into many discussions of political and social matters that should be resolved upon the basis of knowledge and reason. Few laymen appreciate the vital role played by scientists in maintaining modern civilization. Scientists are often regarded as "narrow specialists," and "mere technicians," to be tolerated because of the practical by-products of scientific research, though their motives and methods may be neither shared nor understood.

6

SCIENCE

IN

THE

MAKING

Now most scientists would like to live in a society that had more respect, as A. P. Sloan has aptly put it, "for the power and beauty, not just the utility, of unrestricted human thought." 1 W e believe that we have something to offer more important even than the material, economic by-products of our work. Scientists have gradually developed means for distinguishing truth from error that were not available to speculative philosophers. Plato said, in the Phaedo, "This was the method I adopted: I first assumed some principle, which I judged to be the strongest, and then I affirmed as true whatever seemed to agree with this, whether relating to the cause or to anything else; and that which disagreed I regarded as untrue." And again, in the Republic, he said, "And let us dismiss the heavenly bodies, if we intend truly to apprehend astronomy, and render profitable instead of unprofitable that part of the soul which is naturally wise." Plato was an exceedingly intelligent man, but we of lesser brain power have learned some things Plato did not know about how to attack certain kinds of problems. Scientists have discovered ways of gaining knowledge that have much to offer for the effective pursuit of knowledge in all of its forms. My purpose in this and the subsequent lectures is to describe some of these ways. I do it from the down-to-earth standpoint of a daily worker, from the inside, not as a historian of science, nor as a logician, analyzing what is called "scientific method" from without. I do not disparage these approaches, but they seem to me to have been followed more often and exhaustively than the one I am using.

THE

SEARCH

FOR

KNOWLEDGE

J

I distinguish two aspects of science; one may be designated content, the other, enterprise. The one is, as the dictionary says, "classified knowledge"; the other is the ways in which scientists work and think. The one is the way we write up our results, in papers and books, in the passive voice, giving the impression that we start with precise measurements and proceed by strict logical steps to incontrovertible conclusions. The other is the way we really do it—starting with hunches, making guesses (most of which prove to be wild), making many mistakes, going off on blind roads before hitting on one that seems to be going in the right direction. That is science in the making. A student asked me to define chemistry. I replied, "Chemistry is what chemists do and how they do it." It is that aspect of science, with material drawn mainly from the kind of science I and my friends practice, which I wish to describe. The procedure, when not obstructed by pedantry, is natural and intuitive. A beautiful instance of it occurred years ago while I was trying to assist a young girl, very dear to me, to gain a geometric concept of the formula for the area of a circle. I drew a circle within a square and added the minor diameters, dividing the square into four equal smaller squares, as shown in Figure 1. "You see," I said, "that the area of each of the small squares is r 2 , and that the area of the large one is 41 2 . You see, also, that the area of the circle is less than 41 2 . The number is 3.1416, approximately 3%. It is so important that we designate it by the Greek letter pi, and write area of a circle = irr 2 ."

8

SCIENCE

IN

THE

MAKING

She then drew an ellipse, although she did not remember its name, drew an oblong about it, added the two diameters, and asked me, "Is the area of this [outlining the ellipse] ir times this [pointing to the line marked a] times this [b]?" As a matter of fact, it is. Her analogy was not a proof, but it well illustrates the way in which scientists get the hunches that they then proceed to verify by laborious logic and experiment. Scientific method is often defined as if it were a set procedure, to be learned, like a recipe, as if anyone could SMALL SQUARE LARGE V

A

SQUARE

AREA r2 4r2 7Tr2

CIRCLE ( 7T = - 3 !/7 )

^

AREA

b )

SMALL

OBLONG

Ob

LARGE

OBLONG

4ob

ELLIPSE 77" 0 b Figure i. An example of scientific analogy. become a scientist simply by learning the method. This is as absurd as it would be to assume that a person could become a great artist by learning a "method" of painting pictures or that one can become a good teacher simply by taking a course in methods of teaching. That there is no such thing as the scientific method, one might easily discover by asking several scientists to define it. One would find, I am sure, that no two of them would ex-

THE

SEARCH

FOR

KNOWLEDGE

g

actly agree. Indeed, no two scientists work and think in just the same ways. I shall therefore not presume to discuss scientific method, but rather the methods of scientists. W e proceed by common sense and ingenuity. There are no rules, only the principles of integrity and objectivity, with a complete rejection of all authority except that of fact. The main motivation of scientists is curiosity, an urge to see and understand, to discover order in the vast complexity of nature. Our motives, like those of other men, are mixed. W e are flattered by honors, such as election to the National Academy of Sciences, a medal, an increase in salary, appointment as Bampton Lecturer. But these rewards are not the main driving force to scientific achievement. I know of no great scientist who selected his calling under the illusion that it would be a good way to get rich. The richest rewards are the excitement of searching and the satisfaction of finding. Those of us who have experienced them do not regard Archimedes as at all queer because, after lying in his bath and thinking about the buoyancy of his body in the water, he suddenly sprang out and rushed away, exclaiming, "Eureka, I've found it." Because I am trying to give, not an objective, analytical description of science, but a subjective impression, as felt by a scientist, of "inside science" (to borrow from John Gunther), it seems appropriate to draw heavily upon my own experience, where I best know the successive steps of speculation and experiment, by telling the story of the gradual development of a theory of solubility.

ÍO

SCIENCE

IN

THE

MAKING

The term "theory" as used in physical science, usually refers not to any simple statement, such as a hypothesis that has gained some degree of credibility, but rather to a complex of concepts and interrelations, sometimes so considerable as to require a whole book to set it forth. The Kinetic Theory of Gases has grown into a vast array of equations dealing with the behavior of gases; their compressibility, thermal expansion, specific heat, viscosity, liquefaction, etc. Atomic Theory now includes our great and ever increasing understanding of atomic structure and its relation to the physical and chemical properties of the elements and their compounds. These and others are among the finest achievements of the human mind and are comparable to the great works of literature and the fine arts. They are the "cathedrals," the beautiful structures erected by the effort of many men. I shall discuss one of them at some length in the third lecture. In order to illustrate some of the procedures used by experimental scientists, I wish to tell the story of the building of a theory of solubility. This structure is hardly one of the great cathedrals, and it is not finished, bu,t the building procedures are none the less typical, and they are the ones I can best describe from first-hand experience. All of the steps, I am sure, are so simple that anyone who tries can follow them easily. I was a young instructor at the University of Pennsylvania when I became interested in the colors of solutions of iodine in various solvents: ranging from violet, through red, to brown and yellow. These colors are so beautiful

THE

SEARCH

FOR

KNOWLEDGE

11

as to lend an aesthetic element to their study. But I am so constructed as to be interested but not satisfied by the contemplation of beautiful color; I became very curious to learn how these different solvents could so alter the color of iodine. T h e most obvious piece of pertinent information was the virtual identity of the violet color of the vapor of iodine with the violet of its solutions in carbon disulfide, carbon tetrachloride, hexane, chloroform, and others. N o experienced scientist relies upon his visual impression of color. He knows that his unaided senses can fool him badly, andhe turns to instruments wherever possible. I had almost no apparatus at my disposal, least of all a spectrophotometer to measure light absorption at all wave lengths such as we have today. But my eyes did not deceive me that time, as may be

o

UJ m 800 a. to 6 0 0 CD