BOOK OF THE DAY - Colm Keena: Quantum: Einstein, Bohr and the great debate about the nature of reality.Manjit Kumar Icon books; 360pp; £20
IN THE early years of the 20th century, young male physicists in England, Germany, France, Denmark, Austria and Switzerland were part of a great collective effort that has transformed the planet on which we live by opening the way for much of what defines the modern world.
Manjit Kumar documents how these scientists strove to identify or describe how the world operates at the atomic or microphysical level. Through their work, they developed the theories that led to the electron microscope, the laser, the computer and the atomic bomb, even though at the heart of it all there was a conundrum that has not yet been resolved.
Early in the 20th century, Albert Einstein floated the idea that light might emerge from atoms not as a continuous wave, but as discreet bits, or quanta. He suggested this because he was troubled by a seeming dichotomy: if matter is energy and made of atoms, and atoms are made of discrete, discontinuous particles, then how can light, a form of energy, flow like a wave from an atom?
During the 1920s and 1930s, the debate over the nature of light and microphysical items such as electrons became increasingly acute. Were they particles, quanta, or were they waves, like the waves that ripple out from the stone dropped in a pond? A gallery of scientific greats was involved: Niels Bohr; Louis de Broglie; Wolfgang Pauli; Max Born; Werner Heisenberg; Paul Dirac; and others.
Later in the century, a scientist born in working-class Belfast in 1928, John Stewart Bell, achieved progress in a way that eluded Einstein and Bohr.
Kumar brings us through the detail of the various advances, confusions and mistakes, and what emerges clearly is a picture of how science works as a great international collective effort. Insights, difficulties and findings are shared through publication, informal correspondence and collaborative effort.
The foundations for the technologies that have made the modern world are documented in this book, but not one of the scientists involved took out a patent.
At the core of the book is quantum mechanics, a theory that implies there is a limit to what can be known about the microphysical level. If you test for the location of an electron, you cannot test for its momentum. If you test for its momentum, you cannot test for its location. The champion of the theory, Niels Bohr, argued that, at the microphysical level, science is not describing a world that exists independently of the experiments that seek to say something about it. "There is no quantum world," he said. "There is only an abstract quantum mechanical description."
Einstein recoiled at this idea. He refused to accept that quantum mechanics was a complete or finished theory, beyond which science would never travel so as to tell us something about an independently existing reality. As we leave the book, all we are told is that Einstein may, after all, have been correct.
The book is a tough read at times, but then there are the pen pictures of the scientists involved and, not least, the political backdrop to their work. In October 1929, the Wall Street Crash occurred. The economic collapse was felt particularly badly in Germany, where discontent soon swept the Nazis into power. In 1933, the Nazis sacked Jews working in their universities, and overnight the universities lost almost half of their theoretical physicists.
Einstein, who had been living in Berlin, spent the rest of his days in the US. As the Jewish intelligentsia fled Hitler, there was a sudden haemorrhaging of German and European intellectual capital, with most of it ending up in the US. A huge transfer of power occurred, much in the way that financial and political power is now slipping, as this review is being written, from the US.
• Colm Keena is an Irish Timesjournalist and a science graduate of Trinity College Dublin