Quantum, By Manjit Kumar

Collisions with the solace of quantum

Dr Johnson furiously rejected Bishop Berkeley's contention that the world was nothing but a collection of our ideas and impressions and that therefore when you walked out of a room (assuming there was no one else in it) it ceased to exist. "I refute it thus!" Johnson proclaimed, kicking at a stone. Though he started out as a relativist, Albert Einstein was driven into becoming the Dr Johnson of the 20th century, forever kicking out at the most fantastical formulations of quantum theory.

Manjit Kumar's Quantum is a super-collider of a book, shaking together an exotic cocktail of free-thinking physicists, tracing their chaotic interactions and seeing what God-particles and black holes fly up out of the maelstrom. He provides probably the most lucid and detailed intellectual history ever written of a body of theory that makes other scientific revolutions look limp-wristed by comparison. Sex, suicide and genocide get a look-in too, but in the end the fate of the world seems to hang on the random trajectories of invisible specks of matter.

Ironically, Einstein gave a kick-start to the theory he ultimately sought to overthrow. One of his early papers talks of "light-quanta" (later "photons"), not so much a "ray" as a stream of bullets. Nobody took him seriously. Then Niels Bohr, the Danish physicist, pulled together Planck, de Broglie, Heisenberg and Schrödinger and gave coherence to theories of incoherence and discontinuity. Bohr imposed a vision of the micro-universe as an asylum of high-speed schizoid anarchists and lottery-playing paradoxes.

Light is both wave and particle simultaneously. The Uncertainty Principle prohibits you from knowing everything you want to know. On the other hand, you can have a cat in a box which is both alive and dead.

Knowing the mind of God was implicit in classic Newtonian science. After the "Copenhagen interpretation", it wasn't clear if God really knew what he was doing in the first place. Which is why Einstein objected, "God does not play dice". All over Europe and America, Einstein and Bohr locked horns, with Einstein dreaming up experiments that would pin down these pesky particles and Bohr letting them out of the box all over again.

Their argument hinged on whether the universe was or was not "observer-independent". Bohr argued that if every observation subtly altered the very thing you were looking at then all we can ever have is a bundle of theories and measurements. "Do you think the moon ceases to exist just because you have stopped looking at it?" was Einstein's withering retort.

Entangled particles are the telepathic identical twins of the quantum realm. Even though separated by interstellar spaces, they still resonate instantaneously to each other's vibe. Einstein derided "spooky action at a distance", but this absurdity has now been experimentally demonstrated. God has been caught playing dice.

The truth is out there. Yet the very notion of "out" and "there" reveals the subtle human-centred, "anthropic" perspective that pervades our most empirical observations. It is as if the two antagonists in this great debate, Einstein and Bohr, are as entangled as the strands of a double helix.

Although Kumar (I think) throws in his lot with the quantum side of the equation, he remains classical and clinical in methodology and style. He keeps the "I" hygienically removed from all the argument, as if everything really was being observed by a neutral god. But as Bertrand Russell once pointed out, if you want to be strictly objective, you can't say, "There is a dog". You ought to say, "I see a canoid patch of colour."

Andy Martin's latest book is 'Stealing the Wave' (Bloomsbury)