marcelo_gleiser's picture
Appleton Professor of Natural Philosophy, Dartmouth College; Author, The Island of Knowledge
To Unify or Not: That is the Question

I grew up infused with the idea of unification. It came first from religion, from my Jewish background. God was all over, was all-powerful, and had a knack for interfering with human affairs, at least in the Old Testament. He then appeared to have decided to be a bit shyer, sending a Son instead, and only revealing Himself through visions and prophecies. Needless to say, when, as a teenager, I started to get interested in science, this vision of an all-pervading God, stories of floods, commandments and plagues, started to become very suspicious. I turned to physics, idolizing Einstein and his science; here was a Jew that saw further, that found a way of translating this old monotheistic tradition into the universal language of science.

As I started my research career, I had absolutely no doubt that I wanted to become a theoretical physicist working on particle physics and cosmology. Why the choice? Simple: it was the joining of the two worlds, of the very large and the very small, that offered the best hope for finding a unified theory of all Nature, that brought together matter and forces into one single magnificent formulation, the final Platonist triumph. This was what Einstein tried to do for the last three decades of his life, although in his days it was more a search for unifying only half of the forces of Nature, gravity and electromagnetism.

I wrote dozens of papers related to the subject of unification, even my Ph.D. dissertation was on the topic. I was fascinated by the modern approaches to the idea, supersymmetry, superstrings, a space with extra, hidden dimensions. A part of me still is. But then, a few years ago, something snapped. It probably was brought by a combination of factors, a deeper understanding of the historical and cultural processes that shape scientific ideas. I started to doubt unification, finding it to be the scientific equivalent of a monotheistic formulation of reality, a search for God revealed in equations. Of course, had we the slightest experimental evidence in favor of unification, of supersymmetry and superstrings, I'd be the first popping the champagne open. But it's been over twenty years, and all attempts so far have failed. Nothing in particle accelerators, nothing in cryogenic dark matter detectors, no magnetic monopoles, no proton decay, all tell-tale signs of unification predicted over the years. Even our wonderful Standard Model of particle physics, where we formulate the unification of electromagnetism and the weak nuclear interactions, is not really a true unification: the theory retains information from both interactions in the form of their strengths or, in more technical jargon, of their coupling constants. A true unification should have a single coupling constant, a single interaction.

All of my recent anti-unification convictions can crumble during the next few years, after our big new machine, the Large Hadron Collider, is turned on. Many colleagues hope that supersymmetry will finally show its face. Others even bet on possible signs of extra dimensions revealed. However, I have a feeling things won't turn out so nicely. The model of unification, which is so aesthetically appealing, may be simply this, an aesthetically appealing description of Nature, which, unfortunately, doesn't correspond to physical reality. Nature doesn't share our myths. The stakes are high indeed. But being a mild agnostic, I don't believe until there is evidence. And then, there is no need to believe any longer, which is precisely the beauty of science.