Thursday, 14 October 2010

The Amazing Story of Quantum Mechanics

Captain Quantum

The Amazing Story of Quantum Mechanics: A math-free exploration of the science that made our world by James Kakalios

New Scientist, 16 October 2010

“EXTRAVAGANT Fiction Today, Cold Fact Tomorrow” was the bold claim of Amazing Stories, the first American magazine devoted to science fiction. Beginning in the 1930s, these sci-fi pulps and comics envisaged that by the year 2000 we would be living in a world with domed underwater cities and travelling in flying cars and by jetpacks. Instead we have mobile phones, laptops and DVDs.

The predictions were off, says James Kakalios, because implicit in the promise of flying cars is the availability of lightweight power supplies capable of producing enormous quantities of energy. In fact, the capacity of batteries to act as reservoirs of energy is limited by the chemical and electrical properties of atoms – and we cannot change the physics of atoms.

This is Kakalios’s cue to explain the key concepts of quantum mechanics and show how these ideas account for the properties of metals, insulators and semiconductors – and how they underlie the magnetic properties of atoms that let us store vast amounts of data on computer hard drives and build MRI scanners that can see inside the human body.

The physicists who developed quantum theory and the fans of sci-fi pulps had one thing in common, says Kakalios, and that is a willingness to suspend disbelief as they accepted the impossible as real. Three such quantum facts were: light is an electromagnetic wave that is actually composed of chunks of energy; matter is composed of particles that exhibit a wave-like nature; and both light and matter have a property called spin that can only have certain values.

Having provided the reader with these counter-intuitive notions, Kakalios looks at the problems they solved. To help explain Planck’s discovery of the quantum, the photoelectric effect, the quantum atom, wave-particle duality, Schrödinger’s wave equation, the probabilistic interpretation of the wave function, the uncertainty principle and more besides, comic-loving Kakalios enlists a legion of superheroes, from Superman to Dr Manhattan.

In addition to his bright-blue appearance, Jon Osterman aka Dr Manhattan, appears to have gained control of his quantum- mechanical wave function. This, the starting point for Kakalios’s highly readable presentation of quantum ideas, give him the ability to alter his size at will, to teleport himself and others from one place to another, and to experience the past, present and future simultaneously.

The scientist as a world- changing hero is an apt description for the physicists who developed quantum mechanics, Kakalios believes. He has a point. The discoveries by a handful of physicists back in the 1920s and 1930s of the rules that govern how atoms interact with light and each other continue to shape and change the world we live in.