Special Circumstances

Critical Opalescence

From Clockwork Science By Freeman J. Dyson, a review of Einstein's Clocks, Poincaré's Maps: Empires of Time by Peter Galison. (published in the New York Review of Books, Vol 50, Num 17, Nov 6, 2003 temporary url)

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.

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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."

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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.

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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.