杏吧原创

SPOILER alert: we have no answer for the question 鈥渨hat is real?鈥� We can鈥檛 describe matter in terms of a wave or a particle; it is both and neither. We are stuck in the place that Erwin Schr枚dinger described in 1926: 鈥淚t would depend on the taste of the observer which he now wishes to regard as real鈥� There is certainly no criterion for reality if one does not want to say.鈥�

Nor do we have a good handle on why quantum things such as atoms can be in two states at once while we, who are nothing but agglomerations of these entities, simply can鈥檛. All we have are 鈥渋nterpretations鈥� of experimental results. Choosing one is also a matter of taste.

How has all this remained unresolved for so long? That is the question Adam Becker is really answering in his impressive debut, What Is Real? While he points out that 鈥渜uantum physics works鈥�, just putting it to work to build the modern world is disingenuous because it means, he says, 鈥減apering over a hole in our understanding of the world 鈥� and ignoring a larger story about science as a human process鈥�.

Becker handles the physics with aplomb, though the ins and outs of quantum experiments are not his main concern. (Philip Ball鈥檚 excellent new book Beyond Weird is more discursive there, making a great companion to Becker鈥檚.) His real strength is the excavation of stories that show how deeply quantum physics was in thrall to the personalities of its developers.

The cast is colourful and expansive, and provides engaging drama. We have the towering figure of Niels Bohr imposing his 鈥淐openhagen interpretation鈥� on the theory. Then there鈥檚 languid and aloof Hugh Everett III, struggling against Bohr to create the many-worlds interpretation, and the almost-beatified John Bell, whose sublime work shed so much light on the mystery of quantum entanglement. Of course there was also David Bohm and his headstrong defiance of both McCarthyism and Copenhagenism, and Max Planck鈥檚 courageous but failed attempts to defend Jewish scientists from Hitler鈥檚 frenzy.

Planck鈥檚 heroic failure may have changed history, forcing a brain drain that altered the geography of atomic weapons research. But the subsequent US success with physics had its own fallout. After the second world war, when physics was primarily a resource for creating military superiority, distracting discussions about quantum theory were frowned upon. US physicists were quietly trained to 鈥渟hut up and calculate鈥�, as Cornell University physicist David Mermin wrote.

鈥淧hysicist Murray Gell-Mann said that Niels Bohr brainwashed a whole generation of theorists鈥�

Becker traces the roots of this attitude back to the Copenhagen interpretation. Fudged and fumbled into being by Bohr in the late 1920s, it says we can only talk about the results of experiments, not what is happening within unobserved quantum systems. For decades, it was gospel. As physicist Murray Gell-Mann put it in 1976: 鈥淣iels Bohr brainwashed a whole generation of theorists.鈥�

But it could have been so different. In the mid-1930s, mathematician Grete Hermann demolished a proof, written by the renowned John von Neumann, that the Copenhagen interpretation was the only possible one. Her work was ignored. As Becker says: 鈥淚t鈥檚 hard to imagine that her gender had nothing to do with the reception of her work in 1935, a time when women were still generally not allowed to teach at universities.鈥�

The subtext running through this hugely enjoyable book is that, if we still have a long way to go before we understand reality, we may only have our own prejudices to blame. The story so far is of dazzling insights, flawed male scientists 鈥� and very few female ones. It鈥檚 a key acknowledgement that should help to ensure that writing the next chapters of the quantum tale is open to all.

This article appeared in print under the headline 鈥淩eality checks鈥�