Why is string theory a mess

Order in chaos

"I play the piano myself. The oldest plays the violin, the daughter plays the piano, then a cellist comes, then a flutist, then two violinists."

He loved the music. For example the fugues by Bach with their symmetrical structure and their almost mathematical beauty. Werner Heisenberg was also interested in symmetry and beauty in his creative field, physics.

As a 23-year-old Heisenberg became a revolutionary in the natural sciences: in 1925 he founded quantum mechanics, one of the cornerstones of modern physics. It describes the microcosm, i.e. the world of molecules and atoms. Visibility quickly fails because of this theory: In the world of quanta, chance reigns, because in some situations particles can behave completely unpredictably.

Nevertheless, quantum mechanics is considered to be the most successful theory of the 20th century. Countless technical inventions are based on it, including CD players, microprocessors and solar cells. In 1932 Heisenberg received the Nobel Prize in Physics for his contributions to quantum mechanics. And:

"Out of about a hundred scientific papers, at least 80 are very outstanding: The indeterminacy relations that he had found in order to interpret quantum mechanics. Then in 1929 he founded the quantum field theory. In 1932 he introduced the nuclear forces", "

says Helmut Rechenberg, head of the Werner Heisenberg archive. During the Second World War, Heisenberg was involved in the uranium project. On behalf of the National Socialists, it was supposed to sound out the extent to which the newly discovered nuclear fission could be used for civil or military purposes. Heisenberg's role in the uranium project is controversial to this day. Then, in the fifties, he tried to hit the jackpot - a "Unified Theory of Elementary Particles".

"" A whole lot of new elementary particles were discovered after the war. And you could also see that they transform into one another. Then Heisenberg said: Aha, I'll make a new theory. It should contain a kind of primordial field, a primordial substance that is not identical to any elementary particle. And he made a proposal in 1958 and tried to apply it. "

On February 24, 1958, Heisenberg presented his "Unified Theory of Elementary Particles" to the professional world at the Physics Colloquium of the University of Göttingen. In doing so, he tried to put the chaos of the elementary particles in order in one fell swoop. The core of the theory should be a single formula. It became known as the "universal formula" - a term that Heisenberg himself found misleading. His theory should not be about explaining the whole world with a single formula, but only the world of the smallest particles.

"This term 'universal formula', which we physicists do not love at all, is probably due to the fact that it is a law of nature that perhaps has a somewhat more general character than the laws of nature that are otherwise often formulated in physics Theory is correct, then it is a basic structure of nature, which of course is also decisive for the world on a large scale. "

Heisenberg assumed that all particles, since they can transform into one another, are made of one and the same substance.

"I just want to understand the elementary particles as different forms into which the energy has to move in order to become matter. These forms are probably essentially the only forms that exist. I don't think that one should talk about them, that these elementary particles can be broken down further. "

Most colleagues were skeptical of Heisenberg's hypothesis. And indeed: in the 1960s it turned out to be a mistake. At that time it was discovered that the elementary particles can very well be broken down further into so-called quarks. This made Heisenberg's theory obsolete. The Nobel Prize laureate had failed - similar to Albert Einstein, by the way, who had also been looking for a universal formula. But the vision of the two scientists lives on - as a hypothesis called string theory.

"" Strings are small threads or small loops. In string theory one imagines that all matter in the universe is made up of these small strings ","

says Dieter Lüst from the Max Planck Institute for Physics in Munich. Only: Nobody knows whether this theory is true. And that means: Physicists are still looking for an equation that describes the structure of matter in a single formula.