02/07/2012 19:22 BST | Updated 01/09/2012 06:12 BST

Beyond the Standard Model: The String Controversy

In a couple of days, the final results on the search for the Higgs boson at CERN will be publicised, so in the meantime, I would like to dwell a bit on what comes after. Indeed, if the Higgs is found, this will only have confirmed, once more, that the Standard Model of Particle Physics was right, and was able to predict the existence of a new, exotic particle.

But the Standard Model has been around since the 70s, and, for all its predictive power in particle physics, it suffers from major shortcomings: for instance, it becomes completely inappropriate when dealing with gravity. For this reason, most of the work of theoretical physicists for the last 40 years has endeavoured to find a deeper, all-encompassing theory, a Grand Unified Theory (a GUT...).

One of the serious contenders for the title today is superstring theory, a rather elegant theory that postulates that all known phenomena are actually manifestations of the vibrations of microscopic strings (too small to be observed with our present technology), in nine or 10 dimensions of space.

Fascinating on a purely aesthetic level (as Brian Greene puts it, the Universe of string theory is "nothing but music"), this theory has also sparked a truly interesting controversy in the physics community, best illustrated by the publication in the past decade of books such as The Elegant Universe (Brian Greene) or The Cosmic Landscape (Leonard Susskind) on the "pro-string" side, and The Trouble With Physics (Lee Smolin) or Not Even Wrong (Peter Woit) on the other side (Greene's and Smolin's books especially provide a good, balanced overview of the subject).

Indeed, string theory today occupies a rather unique position in the world of theoretical research: it has, for nearly 30 years, concentrated the efforts of hundreds among the brightest physicists of our generation, and yet has still, as even string theorists themselves admit, not been formulated definitely in the form of a unique set of equations, making equally unique (and falsifiable) predictions, which is how most scientists define a physical theory. In fact, the name "string theory" is somewhat misleading, in that the "theory" today is more of a set of intuitions and ideas on what the end product may look like (although it must be conceded that even in its incomplete form, some rather interesting predictions have been extracted from it, such as those concerning black-hole entropy).

This curious state of affairs has led scientists to adopt different attitudes towards string theory: some claim it is "not even wrong", in that it can, in its current form, neither be proved nor disproved using experimental data, while others believe that eventually a unique theory will emerge, making predictions about our world, but that this would necessitate a better understanding of the theory than we have today.

An even more extreme attitude (though more marginal) is that string theory is right, but that humans are simply not clever enough to grasp it fully, the argument being that if you asked a dog to understand even rudimentary physics, this would prove beyond its intellectual means, so that in the end there is no reason why the human mind should not possess similar limits in understanding the physical world.

This last example is of course quite extreme, but usefully illustrates one of the most common reproaches made to string theorists: they have come up with something that is nothing more than an interesting hypothesis, and when they find that this hypothesis leads to unmanageable equations, they try and change the "rules of the game" rather than admit they have hit a dead end, which raises the question as to whether or not string theory may actually be damaging to science.

Indeed, although the idea that string theory will eventually prove beyond the grasp of humans is not one shared by the majority of the string community, the fact that some scientists are in such awe of their own creation that they are willing to believe it true but ineffable does reveal an alarming streak of fanaticism in this area of research.

But, in the end, what must be borne in mind is that the over-confidence of some string theorists is simply the result of their brainchild being "the only game in town" (or if not the only one, certainly the most popular), and unfortunately, as Lee Smolin argues in his book, this has got more to do with academic sociology than science...