Walter Kohn shared the 1998 Nobel prize for chemistry, but in his 86 years he has never taken a university course in the subject. That was not by choice, as Kohn described to me when I caught up with him earlier today: it was due to the Second World War.

Although born an Austrian, Kohn automatically became a German citizen in 1938 when his country was taken over. He had just turned 15 and was angry that events had forced him to cancel his birthday party. Four years later, having fled Austria (initially for the UK), Kohn wound up in Toronto where the family that eventually took him in introduced him to a professor who advised Kohn to enrol in a demanding maths and physics programme at Toronto University.

The course also required Kohn to take a course in chemistry, but the chairman of the university’s chemistry department took the “absolutely rigid” position that he couldn’t allow any German into the building because of the war. Things looked unpromising. But then the dean of the faculty intervened and had Kohn admitted as a “special student” who would not take the chemistry component of the course.

For Kohn, who has been a US citizen since 1957, it was the events of the war that drove him towards science. Having been thrown out of his school when he he was 15, he ended up at a Jewish gymnasium in Vienna where the director, a physics teacher and (Kohn would later learn) a former assistant of Einstein, inspired him. “I was able to forget, at least temporarily, the brutalities that went on [both Kohn’s parents were killed in Auschwitz] and appreciate the beauty of science.” Kohn had no interest in nor apparent talent for mathematics while at his previous school.

I was able to forget the brutalities that went on and appreciate the beauty of science.

Rejecting the pacifist stance of his father, Kohn joined the Canadian Infantry Corps during the last year of the war, and decades later was active in attempts to end the US–Soviet nuclear arms race. His commitment to a humane and peaceful world explains why he chose not to talk about his Nobel-prize winning work – the development of density functional theory, which allowed researchers to calculate complex chemical reaction systems comprising up to 1000 atoms – at this year’s meeting, but instead to discuss “an Earth powered predominantly by solar and wind energy.”

Kohn sees it as his responsibility as a member of the human race to do something about the looming energy crisis. He says that oil and gas (which provide 60% of the world’s energy) will be replaced with wind and solar energy by the middle of the century. He admits energy costs will rise, but reckons this green new world can be realized with existing technology.

Oil and gas will be replaced with wind and solar energy by the middle of the century.

Although Kohn spent several years working on semiconductors such as silicon, which are the main material in solar cells, he admits that his status as a Nobel laureate has helped him gain influence in energy matters.

“The Nobel prize has opened doors that without the Nobel prize I would have liked to go through but might not have been able to,” he says. Kohn was a member of the science advisory committee of the US Department of Energy during the Bush administration, although he says eventually he saw the committee partly as a cover for the non activity of the then US government on the energy/climate problem.

Kohn has worked on an unusual breadth of topics throughout his career — starting in maths, completing a thesis in nuclear physics, working on quantum electrodynamics, then solid state physics, and finally chemistry. He says it’s easy to think of himself of as a physicist rather than a chemist, yet the fact is his work lies on the border between the two subjects.

“I feel bi-cultural,” says Kohn. “In my view, my work has been more influential in chemistry than in physics, and since getting the Nobel prize the chemistry community has received me very warmly.” He adds that chemistry has the edge when it comes to making contributions to mankind. “Physicists emphasize general principles more than chemists, who tend to deal with specific systems. But what I find attractive about chemistry is that it is so enormously useful in people’s lives.”

So is Kohn, who still goes into his office every day despite having officially retired over a decade ago, a physicist or a chemist?

I made my own mind up after asking him if he ever wished he’d stuck with the quantum field theory for which his thesis adviser, Julian Schwinger, went on to share the 1965 Nobel prize in physics (and which paved the way for the standard model of particle physics).

His face suddenly broke into a broad smile. “We had this tremendous block for about two decades where we had equations that we thought were OK, such as the Dirac equation, but when you ran them through all these infinities turned up – it was like running into a brick wall every time,” recalls Kohn.

“What these guys — Schwinger, Feynman and Tomonga – did, going around this block in their own ways, was fantastic – and then they compared it with experiment and BANG! It was right on the nose. I’ve never experienced a more exhilarating scientific revolution in my life.”

Walter Kohn will take part in a panel discussion about the role of chemistry in renewable energy on Tuesday 30 June.

 » Matthew Chalmers completed a PhD in physics and works as a freelance writer. i-ec50973aaa80d157198edd29ee8b77f8-chalmers45.jpg