He is the pre-eminent physicist in the US, the king of string theory, but the soft-spoken Prof Edward Witten is content to let his work do the talking, writes Seán O'Driscoll.
Prof Edward Witten pauses for thought between sentences, between words and even between syllables. The pauses increase when the conversation moves from mathematical equations to personal memories, as if his own emotions have been crammed to the back of his mind by his huge need for storage space.
The sometimes excruciatingly long wait for answers is worth it, if only because his brain could hold the answers to some of the universe's most profound questions: What created the big bang? What is reality? Are there more dimensions than we see? Is there more than one universe? And, given Witten's polite rejection of God, how did we get here?
To that end, Witten has become the de facto king of string theory, the most influential area of theoretical physics and one that hopes to unite Einstein's general theory of relativity with quantum mechanics. This connects the very large with the very small in a unifying theory that would open up a massive new area of exploration and could offer key clues about the origins of the Big Bang.
Under Witten's version of the universe, everything - light, radio waves, people, planets, newspapers, are all made up of tiny strings that vibrate at different frequencies, each frequency determining whether the strings are defined as energy (X-rays, visible light, ultra-violet) or matter (me, you, rocks, Jupiter, a table).
For string theory to work, however, our universe would have to have 10 dimensions, not the four to which we are accustomed (length, breadth, height and time).
The other six dimensions, string theory suggests, are tiny and tucked up under our own, as if our entire universe was sitting on top of curled-up newspapers.
I visited Witten, the most referenced physicist in America, at his modest Princeton office, just steps away from where Einstein exhausted the last years of his life trying in vain to find a unifying theory of the universe.
Witten is tall, swarthy and surprisingly soft spoken, his voice sometimes dropping so low that I have to switch my tape recorder to full volume to hear a mild "possibly" at the end of one sentence.
If I understand him correctly, string theory operates on a level one billion, billion, billion times smaller than a full stop at the end of a newspaper sentence. "Let me think about that for a moment," he says, looking out the window at the grassland in front of his office. "No, I think your figure is too large. I like to say that it's one billion, billion times smaller than an atom."
It is the small scale of his work that has landed Witten into serious controversy this summer. Two eminent scientists, one a former string theorist, the other a cosmologist, both wrote books suggesting that most string theorists have no idea what they are talking about and that string theory is fundamentally flawed.
Their main argument rests on philosopher Karl Popper's belief that all scientific theories must be "falsifiable" to be credible and string theory simply cannot be proven or disproven.
Peter Woit suggested in his recent book Not Even Wrong: The Failure of String Theory that the exotic and impenetrable science of string has gone the way of 1970s deconstructionist literary criticism - a pretentious world of prima donnas churning out unsubstantiated theories for gullible undergrads.
Prof Witten has not read the anti-string theory books and is so mild-mannered in his response that his voice trails off completely. "I don't think it's terribly useful to have things in the public domain, it tends to turn into a very public situation that unfairly favours the critic," he says.
To show that his theories are more than mere conjecture, he is very animated about the new Large Hadron Collider, which is expected to start operation near Geneva in November 2007. The largest and most expensive science experiment ever created, it will smash billions of protons together, racing them to almost the speed of light.
The colossal amounts of information generated will be analysed by 1,800 scientists from 165 universities and laboratories in 35 countries and could silence some string theory critics.
While Witten would be "very disappointed" if the collider did not offer some clues to the relationship between the fundamental forces of the universe, he does not carry any illusions that it can "prove" string theory.
"It would take extremely optimistic assumptions to reach a situation where it would prove string theory. More realistically is to find a significant piece of the puzzle, but it's hard to know, it's anyone's guess what's going to happen," he says.
Witten stands up and points out Einstein's Princeton office, located in the next building, but says that he does not feel Einstein's presence and isn't driven by emulation of his famous predecessor. He laughs while recalling that his father, also a Princeton physics professor, almost ran over an absent-minded Einstein when he wandered out in the middle of the road near the college.
Despite the family's deep emersion in theoretical physics, Witten's brother, Matt, a writer on Law & Order, CSI Miami and many other legal dramas, shares little of his brother's or father's interest in theoretical physics.
Witten himself began his career as a political journalist, writing in The Nation and The New Republic before working for anti-Vietnamese war presidential candidate George McGovern. Any slight regrets about not continuing in politics? "None at all," he says. "I realised that I didn't have the right skills for that. Working in politics requires a kind of common sense that I just don't possess. I can assure you I'm far better off where I am now. Wherever that might be."