In a small lecture room at Penn State, Oxford mathematician and physicist Roger Penrose lectures to a packed crowd of colleagues and students. The soft-spoken 62-year-old professor is one of the world's leading experts on general relativity and quantum mechanics, the two complex theories that explain just about everything that happens in our universe. His talk today, however, appears to concern a small bundle of tubes, which he hastily sketches on the blackboard.
The bundle could be any one of a dozen different exotic entities from Penrose's menagerie of mathematical and physical objects-- "supertwistors," "wormholes," and "worldtubes"--all space-time oddities now second nature to his audience.
Yet this particular bundle turns out to be an unfamiliar one to his listeners, even though it is, in fact, far more mundane. It is an arrangement of protein structures found in all living cells. According to Penrose, these structures could play a very special role in the universe: they may enable the brain, which is essentially a clump of the same sort of matter that makes up rocks and stars, to generate the mind, that intangible, unbounded entity that provides us with an inner voice, imagination, emotions, thought, and our very sense of self.
Although the subject may seem a little far afield for this gathering, Penrose contends it is well within the group's purview. The quest for the ultimate laws of nature has taken physicists to such wondrous locales as the interiors of massive black holes and the unimaginably small islets of matter conjured up in particle accelerators. Penrose maintains that the trail ultimately snakes closer to home, right through the three and a half pounds of grayish goo jiggling in our skulls. To understand the mind, he says, you need new physics--and, almost paradoxically, uncovering this new physics may very well depend on new conceptions of mind.
Penrose first advanced the argument for a deep, if somewhat vague, connection between the mind and physics in his 1989 surprise best- seller, The Emperor's New Mind. In that book he suggested that consciousness is created by some mysterious quantum mechanical phenomenon that takes place in brain cells. Unfortunately, brain cells seem an improbable locale for quantum mechanical antics. The well-known weirdness of quantum behavior appears almost exclusively in isolated subatomic particles, and it easily becomes masked in large and crowded systems of atoms, such as exist in ordinary matter--and cells. At the time, Penrose was unable to provide any hints as to how that conflict might be resolved. But during the past year he has found a way. Penrose can now point to a component of brain cells that appears to be an ideal conduit for quantum mechanical phenomena. That component, known as a microtubule, is Penrose's nominee for the physical root of consciousness.
