The Scientist as Rebel (27 page)
Read The Scientist as Rebel Online
Authors: Freeman J. Dyson
Kuhn believed in the primacy of ideas, but not to the exclusion of everything else. And in his new book, Galison is telling us that he still believes in the primacy of tools, but not to the exclusion of everything else. As I came to the final chapter of the book, I could almost hear
him shouting, “One thing you people need to understand: I am not a Galisonian.”
Galison uses the phrase “critical opalescence” to sum up the story of what happened in 1905 when relativity was discovered. Critical opalescence is a strikingly beautiful effect that is seen when water is heated to a temperature of 374 degrees Celsius under high pressure. 374 degrees is called the critical temperature of water. It is the temperature at which water turns continuously into steam without boiling. At the critical temperature and pressure, water and steam are indistinguishable. They are a single fluid, unable to make up its mind whether to be a gas or a liquid. In that critical state, the fluid is continually fluctuating between gas and liquid, and the fluctuations are seen visually as a multicolored sparkling. The sparkling is called opalescence because it is also seen in opal jewels which have a similar multicolored radiance.
Galison uses critical opalescence as a metaphor for the merging of technology, science, and philosophy that happened in the minds of Poincaré and Einstein in the spring of 1905. Poincaré and Einstein were immersed in the technical tools of time signaling, but the tools by themselves did not lead them to their discoveries. They were immersed in the mathematical ideas of electrodynamics, but the ideas by themselves did not lead them to their discoveries. They were also immersed in the philosophy of space and time. Poincaré had written a philosophical book,
Science and Hypothesis
, which Einstein studied, digging deep into the foundations of knowledge and criticizing the Newtonian notions of absolute space and time. But the philosophy by itself did not lead them to their discoveries. What was needed to give birth to the theory of relativity was a critical moment, when tools, ideas, and philosophical reflections jostled together and merged into a new way of thinking. Galison would like to put an end to the argument between Kuhnians and Galisonians. In this book he takes his position squarely in the middle: “Attending to moments of critical
opalescence offers a way out of this endless oscillation between thinking of history as ultimately about ideas or fundamentally about material objects.”
The one question that Galison’s metaphor of critical opalescence does not answer is why Einstein discovered the theory of relativity as we know it and Poincaré did not. The theories discovered by Poincaré and Einstein were operationally equivalent, with identical experimental consequences, but there was one crucial difference. The difference was the use of the word “ether.” The wave theory of light, and the theories of electric and magnetic forces that were developed in the nineteenth century, were all based on the idea of ether. James Clerk Maxwell, who unified the theories of light and electromagnetism in 1865, was a firm believer in ether. Electric and magnetic forces behaved like mechanical stresses in a solid medium with suitable properties of rigidity and elasticity. Therefore, it was believed, a solid medium must exist, pervading the whole of space and carrying the electric and magnetic stresses. Light waves must be shear waves in the same elastic medium. The all-pervading solid medium was given the name “ether.”
The essential difference between Poincaré and Einstein was that Poincaré was by temperament conservative and Einstein was by temperament revolutionary. When Poincaré looked for a new theory of electromagnetism, he tried to preserve as much as he could of the old. He loved the ether and continued to believe in it, even when his own theory showed that it was unobservable. His version of relativity theory was a patchwork quilt. The new idea of local time, depending on the motion of the observer, was patched onto the old framework of absolute space and time defined by a rigid and immovable ether. Einstein, on the other hand, saw the old framework as cumbersome and unnecessary and was delighted to be rid of it. His version of the theory was simpler and more elegant. There was no absolute space and time and there was no ether. All the complicated explanations of
electric and magnetic forces as elastic stresses in the ether could be swept into the dustbin of history, together with the famous old professors who still believed in them. All local times were equally valid. In order to calculate with Einstein’s version of relativity, all you needed to know was the rule for transforming from one local time to another. In the competition for public recognition, the clarity and simplicity of Einstein’s argument gave him an overwhelming advantage.
Poincaré and Einstein only met once, at a conference in Brussels in 1911. The meeting did not go well. Einstein afterward reported his impression of Poincaré: “Poincaré was simply negative in general, and, all his acumen notwithstanding, he showed little grasp of the situation.” So far as Einstein was concerned, Poincaré belonged with the ether in the dustbin of history. But Einstein underestimated Poincaré. Einstein did not know that Poincaré had just then written a letter recommending him for a professorship at the Swiss Federal Institute of Technology in Zürich. Here is what Poincaré had to say about Einstein:
What we must above all admire in him, is the facility with which he has adapted to new conceptions and from which he knows how to draw the consequences. He does not remain attached to classical principles, and, in the presence of a problem of physics, is prompt to envision all the possibilities.… The future will show more and more the value of Mr. Einstein, and the university that finds a way to secure this young master is assured of drawing from it great honor.
Poincaré bore no grudge against his young rival. He was still driven by the same generous impulse that made him rush into the coal mine at Magny thirty-two years earlier. A year after the meeting with Einstein in Brussels, Poincaré was dead. Einstein never saw Poincaré’s letter and never knew that he had misjudged him.
Looking back upon this history, I disagree with Galison’s conclusion. I do not see critical opalescence as a decisive factor in Einstein’s victory. I see Poincaré and Einstein equal in their grasp of contemporary technology, equal in their love of philosophical speculation, unequal only in their receptiveness to new ideas. Ideas were the decisive factor. Einstein made the big jump into the world of relativity because he was eager to throw out old ideas and bring in new ones. Poincaré hesitated on the brink and never made the big jump. In this instance at least, Kuhn was right. The scientific revolution of 1905 was driven by ideas and not by tools.
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Norton, 2003.
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A.K. Peters, 2002.
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The theme of this review, the question whether tools or ideas were dominant in the revolution of 1905, is discussed in a wider context in the chapter “Scientific Revolutions” in my book
The Sun, the Genome and the Internet
(Oxford University Press, 1999). There I came to the conclusion that the majority of revolutions are tool-driven, the revolution of 1905 being one of the notable exceptions.
THE WORLD ON A STRING
IN THE GOLDEN
years of the Liberal Party in England, before the First World War, Herbert Asquith was the patrician prime minister and Winston Churchill was an obstreperous young politician. At question time in the House of Commons, Churchill frequently challenged Asquith with provocative statements and awkward questions. After one of these Churchillian assaults, Asquith lamented, “I wish I knew as much about anything as that young man knows about everything.” Reading
The Fabric of the Cosmos: Space, Time, and the Texture of Reality
,
1
this eloquent book in which Brian Greene lays out before us his vision of the cosmos, I feel some sympathy for Asquith. Asquith expresses my reaction to the book precisely.
I recommend Greene’s book to any nonexpert reader who wants an up-to-date account of theoretical physics, written in colloquial language that anyone can understand. For the nonexpert reader, my doubts and hesitations are unimportant. It is not important whether Greene’s picture of the universe will turn out to be technically accurate. The important thing is that his picture is coherent and intelligible and consistent with recent observations. Even if many of the details later turn out to be wrong, the picture is a big step toward
understanding. Progress in science is often built on wrong theories that are later corrected. It is better to be wrong than to be vague. Greene’s book explains to the nonexpert reader two essential themes of modern science. First it describes the historical path of observation and theory that led from Newton and Galileo in the seventeenth century to Einstein and Stephen Hawking in the twentieth. Then it shows us the style of thinking that led beyond Einstein and Hawking to the fashionable theories of today. The history and the style of thinking are authentic, whether or not the fashionable theories are here to stay.
In his book
The Elegant Universe
, published in 1999, Greene gave us a more detailed and technical account of string theory, the theory to which his professional life as a physicist has been devoted. The earlier book was remarkably successful in translating the abstruse and abstract ideas of string theory into readable prose. Early in his new book he gives a brief summary of string theory as he expounded it in
The Elegant Universe
:
Superstring theory starts off by proposing a new answer to an old question: what are the smallest, indivisible constituents of matter? For many decades, the conventional answer has been that matter is composed of particles—electrons and quarks—that can be modeled as dots that are indivisible and that have no size and no internal structure. Conventional theory claims, and experiments confirm, that these particles combine in various ways to produce protons, neutrons, and the wide variety of atoms and molecules making up everything we’ve ever encountered.
Superstring theory tells a different story. It does not deny the key role played by electrons, quarks, and the other particle species revealed by experiment, but it does claim that these particles are not dots. Instead, according to superstring theory, every particle is composed of a tiny filament of energy, some hundred billion billion times smaller than a single atomic nucleus (much smaller
than we can currently probe), which is shaped like a little string. And just as a violin string can vibrate in different patterns, each of which produces a different musical tone, the filaments of superstring theory can also vibrate in different patterns. But these vibrations don’t produce different musical notes; remarkably, the theory claims that they produce different particle properties. A tiny string vibrating in one pattern would have the mass and the electric charge of an electron; according to the theory, such a vibrating string would be what we have traditionally called an electron. A tiny string vibrating in a different pattern would have the requisite properties to identify it as a quark, a neutrino, or any other kind of particle. All species of particles are unified in superstring theory since each arises from a different vibrational pattern executed by the same underlying entity.
This is a fine beginning for a theory of the universe, and maybe it is true. To be useful, a scientific theory does not need to be true, but it needs to be testable. My doubts about string theory arise from the fact that it is not at present testable. Greene discusses in his Chapters 13 and 14 the prospects for experimental tests of the theory. The experiments that he describes will certainly open new doors to the understanding of nature, even if they do not answer the question whether string theory is true.
The Fabric of the Cosmos
covers a wider field than
The Elegant Universe
and paints it with a broader brush. There is not much overlap between the two books. Only Chapter 12 of the new book, which summarizes the earlier book and gives us the gist of string theory without the details, overlaps strongly. Greene himself suggests that readers who have read
The Elegant Universe
should skim through Chapter 12. Except for this chapter, the two books cover different subjects and can be read independently. Neither is a prerequisite for reading the other. The new book is easier, and should preferably be
read first. Readers who got stuck halfway through
The Elegant Universe
may find the new book more digestible.
In the history of science there is always a tension between revolutionaries and conservatives, between those who build grand castles in the air and those who prefer to lay one brick at a time on solid ground. The normal state of tension is between young revolutionaries and old conservatives. This is the way it is now, and the way it was eighty years ago when the quantum revolution happened. I am a typical old conservative, out of touch with the new ideas and surrounded by young string theorists whose conversation I do not pretend to understand. In the 1920s, the golden age of quantum theory, the young revolutionaries were Werner Heisenberg and Paul Dirac, making their great discoveries at the age of twenty-five, and the old conservative was Ernest Rutherford, dismissing them with his famous statement, “They play games with their symbols but we turn out the real facts of Nature.” Rutherford was a great scientist, left behind by the revolution that he had helped to bring about. That is the normal state of affairs.
Fifty years ago, when I was considerably younger than Greene is now, things were different. The normal state of affairs was inverted. At that time, in the late 1940s and early 1950s, the revolutionaries were old and the conservatives were young. The old revolutionaries were Albert Einstein, Dirac, Heisenberg, Max Born, and Erwin Schrödinger. Every one of them had a crazy theory that he thought would be the key to understanding everything. Einstein had his unified field theory, Heisenberg had his fundamental length theory, Born had a new version of quantum theory that he called reciprocity, Schrödinger had a new version of Einstein’s unified field theory that he called the Final Affine Field Laws, and Dirac had a weird version of quantum theory in which every state had probability either plus two or minus two. Probability, as common sense defines it, is a number between zero and one expressing our degree of confidence that an event will happen. Probability one means that the event always
happens; probability zero means that it never happens. In Dirac’s Alice-in-Wonderland world, every state happens either more often than always or less often than never. Each of the five old men believed that physics needed another revolution as profound as the quantum revolution that they had led twenty-five years earlier. Each of them believed that his pet idea was the crucial first step along a road that would lead to the next big breakthrough.
