Graham Farmelo in The Guardian:
Something is rotten in the state of physics. In spite of all the smug talk about the amazingly accurate predictions made by modern models of the most fundamental forces, things go terribly awry if these theories are used to estimate the energy of empty space. A perfectly reasonable back-of-an-envelope calculation that theoreticians have been making for decades overestimates the observed energy by no less than a trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion. This may be the most inaccurate estimate made by conventional theories in the entire history of science.
The eminent mathematician and physicist Roger Penrose identifies several possible sources of the rot. Fashion, Faith and Fantasy in the New Physics of the Universe is based on a series of lectures with the same title that he gave 13 years ago in Princeton. With his usual modesty, he tells us that he was “apprehensive” about presenting his nonconformist ideas there, as that New Jersey town is home to several of the world’s leading theoreticians, many of whom are unsympathetic to his perspective. Some of these leading physicists are among the pioneers of string theory, the only candidate for a unified and fundamental description of nature at the deepest level. This fashionable and mathematically beautiful theory has attracted a global following over the past three decades, but has yet to make a prediction that has been verified by experiment. String theory is the focus of Penrose’s first chapter. He begins by reminding us of kindergarten science, before putting his foot firmly on the accelerator. A little over a hundred pages later, we are contemplating “branes”, the exotic entities that may exist in the deeply subnuclear world, and pondering whether the mathematical forms of nature’s laws have something called “supersymmetry”, which has not shown its face in the most recent experiments at Cern’s Large Hadron Collider, to the great disappointment of many physicists.