Tobias Hürter: How Heisenberg mastered the art of unlearning

When I was in high school, I had a pretty clear idea of how the universe worked. What atoms look like, how the physical world unfolds like clockwork. It was clear, but it was wrong. Since then, I have learned that the world, atoms and all, worked very differently from how I imagined. Unlearning is difficult, it’s unsettling. You need to let go of your closely held beliefs.

This story is not about me in particular, of course. It is a universal human story, a story about how our knowledge advances: to grow, it has to shrink sometimes. A fascinating instance of this pattern took place a century ago. Back then, a young man much smarter than me thought he knew mostly everything about the workings of the universe. His name was Werner Heisenberg, he was born in 1901, raced through his physics studies in Munich, my hometown, and was what we call Überflieger in German: a high flyer, an achiever.

In the summer of 1922, he went to Göttingen to attend a lecture by Niels Bohr – the famed Danish physicist and inventor of the ‘Bohr atom’ – in which he described the electrons orbiting around the nucleus, like planets around the sun. After the lecture, Heisenberg was able to point out an error in Bohr’s calculations. Bohr, impressed by Heisenberg’s sharpness, invited him to take a walk together. Proud young Heisenberg must have felt on top of the world. He knew it all.

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As the two physicists were wandering over the hills of Göttingen, Bohr surprised Heisenberg with a confession. Bohr didn’t believe in the Bohr atom. It may look nice, like a poem or a painting, but it can’t be right. Heisenberg was stunned. Bohr believed that in order to understand atoms, we must learn what it means to understand. In Bohr, Heisenberg had found his intellectual father figure. The man from whom to learn and against whom to rebel. Heisenberg strived to be the one to solve the enigma of the atoms.

Three years later, the summer of 1925. Heisenberg, Bohr and their colleagues were stuck in their search of a new theory of the microcosmos. Atoms and their constituents seemed to behave strangely beyond imagination, sometimes like waves, sometimes like particles, sometimes spontaneously jumping around. Heisenberg wasn’t feeling well, which had to do with another kind of particles: pollen. He was struck down by hay fever and fled to the island of Heligoland far out in the North Sea, bare from blooming plants. His face was so red and swollen that his landlady on Heligoland presumed that he had been beaten up by sailors.

In the austerity of Heligoland, Heisenberg fully understood what Bohr had said all those years ago: how childish it was to imagine atoms as miniature solar systems. In his mind, Heisenberg extinguished the sun and erased the orbits of the electrons. It was the crucial step of Heisenberg’s unlearning. He was free to ask: what do we really know about atoms and electrons from our observations, and how can we cast it into a rigorous theory? He formulated the first version of quantum mechanics, arguably the most precise and successful physical theory of all time. 

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Rarely someone has the ability to unlearn like Heisenberg. But we have the opportunity to follow him in his unlearning and learning. That is what I tried in my new book The Age of Uncertainty. It’s about the creation of quantum mechanics a century ago, a story I found fascinating and inspiring.

Heisenberg was alone when he arrived at quantum mechanics, but he was no loner. It was a group of extraordinary minds who undertook the journey together: Bohr, Heisenberg, Albert Einstein, Marie Curie, Max Planck, Erwin Schrödinger, Wolfgang Pauli and others. Likely no single one of them would have been able to find the theory, which is bizarre by measures of traditional physics. To some of them, for example Einstein and Schrödinger, it seemed so bizarre that they became dissidents and rejected Heisenberg’s theory. The Age of Uncertainty tells of their conversations, their fights and friendships. It sheds light on the question of why some of them, like Heisenberg, were ready to unlearn the traditional way of thinking and to embrace a new kind of physical theory, while others weren’t. Yes, it has to do with personality and stubbornness, with youth and age, but also with the time in which they were living.

A century ago, it was a time of huge social, political, cultural and technological upheaval. Monarchies tumbled, radio came up, pictures began to move, aeroplanes began to roam the skies. Wars were fought with new kinds of weapons. It was an age of uncertainty: a time to unlearn – as it is today. Let’s learn to unlearn as Heisenberg and others did then.

You can buy The Age of Uncertainty by Tobias Hürter from The Big Issue shop on Bookshop.org, which helps to support The Big Issue and independent bookshops.

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