Getting a new perspective; Michio Kaku was inspired by watching fish in a pond

Credit: Chris Callas/COSMOS

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It was Einstein's unfinished business. The world's best-known and most prolific physicist was driven in his latter years to find a single set of laws for the universe: laws that would apply as readily to the chaotic BeBop of sub-atomic particles as to the majestic waltz of galaxies in deep space.

Einstein failed. But on the 100th anniversary of E=mc², a new generation of physicists is carrying the torch and offering the answer to Life, the Universe and Everything. They say the answer is string theory.

Problem is, string theory is too weird for most people to understand. Some scientists even say it's more fiction than science.

Not Michio Kaku. One of the world's best-known theoretical physicists, and one of the key players in string theory, he is a professor at the City University of New York. Not only is Kaku 'sold' on string theory - and one of the earliest players in its development - he is also a passionate proselytiser. He has just completed a world tour for his third popular science book, Parallel Worlds, and is working with the BBC on a documentary series.

But it is not just the desire to spread the word about string theory, physics and the intrinsic value of science that drives him to engage the public. Kaku believes that the very future of the human race is on the line. "We're at a precipice; we are experiencing the birth pangs of a 'Type 1 Civilisation'. And there's no guarantee we'll make it."

I MET MICHIO KAKU in San Francisco, and I must confess to great trepidation before the interview. He is an imposing man. Besides being an author of popular books (his earlier book, Hyperspace, was a global bestseller), he's also written one of the key textbooks of quantum field theory and, together with Keiji Kikkawa of Osaka University in Japan, published two of the seminal papers describing string field theory. I imagined he would not suffer fools lightly.

Nevertheless, repeated desperate efforts to get a handle on this field had led me nowhere. Or rather, to some very weird places: extra dimensions and parallel universes. Somehow this was supposed to follow from the proposition that the fundamental building block of matter is not the quark [atom-smashing physicists have shown that the protons and neutrons at the heart of atoms are actually composed of quarks] but something even smaller - a million billion times smaller - a vibrating string.

Presumably all could be fathomed - if only I understand N-dimensional mathematics. But my background is in biology, and I feared I would be quite incapable of asking him anything intelligent.

As it happened, the night before the interview, I had dinner with three bright, mathematically proficient engineers and a Stanford University neuroscience professor. As a last resort, I asked them for help. What would they ask Michio Kaku?

To my great relief, their difficulties were the same as mine. On my right, a brilliant PhD engineer from Odessa, candidly admitted: "I really can't conceive of extra dimensions." To my left, another smart engineer offered his view that physicists had gone awry by taking mathematical concepts like zero and infinity in a literal way. He believed they were only meant to be used in a symbolic way. Surprisingly, it was the neuroscience professor who was the most receptive to string theory. He offered, "It's up to these physicists to get us out of the mess we're in. We may have to get off this planet."

And so, I found my opening line for the interview. I gingerly suggested that the new physics of string theory seems to affront some people (especially engineers) as if they suspect 'real science' had been hijacked. The silver-haired, avuncular Kaku fixed me with kindly brown eyes and settled into what was clearly a familiar role: that of the patient, tolerant, and at times mischievous college professor. It also became immediately clear that the tussle between engineers and physicists was nothing new.

Physicists and engineers have long failed to see eye to eye, he began. "Engineers want to build bridges; physicists want to understand fundamental laws," he said. "Engineers disdained Einstein's theories, but those equations ultimately resulted in the atom bomb." Einstein was Kaku's hero. He first heard of Albert Einstein at the age of eight, when he learned the great scientist had died and left behind a book with an unsolved mystery. "I wanted to know what was in that book; to me it was more fascinating than any adventure story. What problem was so difficult the great Einstein himself couldn't solve it?

"Today we believe that [the answer to Einstein's quest for the unified field theory] is string theory. It also makes the engineers' eyes go crazy, because we are talking about universes that are unseen." Having expertly trussed his sacrificial engineer to the whipping stand, Kaku proceeded to explain the quest that has captivated him since the age of eight.