String theory is acceptable

If you want to understand the universe, you have to look into the smallest details: into the world of hadrons, electrons, gluons and quarks. This shows what holds our cosmos together in its innermost being. In order to explore these foundations of the universe, physicists have been building particle accelerators for several decades. Tiny building blocks of matter with extreme energy collide in it, for example hydrogen atomic nuclei. The reaction products of the collisions reveal which primal forces and which elementary particles shape our world.

But also the largest accelerator to date, the 27 kilometer long one Large Hadron Collider at the research center Cern near Geneva, could not answer all questions. That is why the physicists are now proposing to build an even more powerful particle cannon - in a 100-kilometer-long ring tunnel, 500 meters underground. Anyone who has ever seen today's cathedral-sized experimental setups in the underground of Cern can hardly imagine that it can be even bigger, even more powerful.

Physics is in a crisis - it is questionable whether a new accelerator will offer the way out

Two questions arise: Who should pay for it? And: How sure can you be that the next accelerator will answer the last questions in physics? One can argue about both. The at least 20 billion euros for the FCC, as the mega project at Cern is called, should be spent on pressing human issues such as climate protection, say influential scientists with some right. But playing off research areas against each other is tricky. Then, for example, manned space travel would have to be put to the test as quickly as possible. It is perhaps more spectacular than a particle accelerator, but scientifically far less productive. And as for the often-cited aspect of the International Space Station that unites people: Thousands of bright minds from all over the world also work together on a mission at CERN.

Seen in this way, 20 billion euros should be acceptable, especially when dozens of nations participate. It would only be a fraction of what the space station costs. And for the understanding of the universe it would be a great step forward to learn what the dark matter haunted in space consists of or how gravity fits in with the other forces in particle physics. The laws of gravity are not yet compatible with quantum physics.

But will a new giant accelerator quench the thirst for knowledge? Here the physicists, especially the theorists among them, find themselves in need of explanation. For years they have piled up mountains of mathematical formulas to complete the physical worldview. Many of their hotly debated theories are of mathematically impressive elegance, such as "supersymmetry" or "string theory". But they all have one flaw: none of these ideas can be confirmed in the measurement data of the particle accelerator. Physics is in a real crisis. It is questionable whether an even larger particle accelerator offers the way out.

Sure, science also has to venture into uncharted waters to find new territory. But there is currently a tempting amount of uncharted territory in real-life questions; World food, renewable energies, climate protection and resource consumption are just a few of them.