CoG Colloquium with Prof. Renato Renner

What does it mean to observe something? Does every experiment have one definite outcome? And does the world have definite facts before someone measures them?

These questions sit at the heart of modern physics. Quantum theory is the most successful scientific theory ever developed, yet it still leaves us with a deep puzzle about what exactly happens during a measurement.

The famous “Wigner’s Friend” thought experiment pushes this tension to the limit by asking what happens when the observer doing the measurement is also treated as part of the quantum system. If quantum theory applies to everything, it should also apply to laboratories, measuring devices, and observers themselves. But when different observers’ perspectives are combined, contradictions can appear. Does this mean that quantum theory breaks down?

In this colloquium, Prof. Renato Renner will explain why these questions are not just a philosophical curiosity, but have direct relevance for all of physics, including the research done at the Center of Gravity. Because they also directly connect to some of the deepest puzzles in modern gravitational physics, including black holes, information loss, and quantum gravity.

The talk will explore how Wigner’s Friend may teach us something essential about the limits of observation, the role of perspective, and the search for a consistent theory of nature.

Reception

17:00-18:00 with snacks and drinks