Deeper still into the foundations of physics

08 January 2025 News item

You may have calculated something, but that doesn't mean you understand it. This is the basic idea behind the Radboud Centre for Natural Philosophy, which officially open its doors in January with a two-day international conference. This will realize a dream of Klaas Landsman, professor of Mathematical Physics, who in 2022 acquired the Spinoza Prize, a sum of 2.5 million euros. He put all the money into this new Centre. ‘Our finest work is yet to come.’

Over the past century, the natural sciences delivered one breakthrough after another. On a microscopic scale, quantum mechanics describes the behavior of matter and energy, on a galactic scale, black holes have been brought into focus, and the discovery of the Higgs-particle completed the so-called Standard Model of particle physics. And a new generation of particle accelerators and telescopes promises even more results to uncover the foundations of the natural sciences.

These results are fruits of a beneficial use of mathematics. ‘Physics leans on both experiments and mathematics for its breakthroughs,’ says Landsman, ‘but experiments to confirm some really crucial predictions exist only in theory for now.’ He mentions the temperature of black holes, essential knowledge for better understanding, ‘but it is unthinkable for the time being to be able to measure them.'

Triangle of thoughts

For Landsman, a new step towards understanding is only conceivable with a ‘triangle of thought’, read: a new life in the relationship between mathematical physics, philosophy and history of science. A new life, because this fusion was already common sense for the founding fathers of physics: Newton and Einstein already successfully united these three disciplines. Disciplinary maturing, but therefore far-reaching specialization, is something of the last two centuries, and has reached its limits for Landsman. 'I myself was working too much on my own, now I can let it all converge in this new institute. Our best work is now going to come,'

With his Spinoza grant, Landsman has assembled a dream team of young scientists, with three associate professors and three PhD-students. The triangle in question, also the Centre’s symbol, refers to the famous ‘Penrose Impossible Triangle’, also known from the work of M.C. Escher: what you see can be true and false at the same time. Thus the Centre’s basic question: what scientists measure looks solid, but does it coincide with ‘reality'? And what does the latter concept actually mean?

‘We thought we had a better and better grasp of processes, but fundamentally nothing is well understood,’ says Landsman. One of the three PhD-students is Silvester Borsboom, who has recently delved intensely into entropy, a basic concept in thermodynamics. ‘It drives you crazy,’ he exclaims. The further he dives into the subject, the less he understands it. 'It's all been calculated in detail, but conceptually it doesn't make much sense. Despite all those calculations, it is not clear what entropy is. Physics has failed to clarify things conceptually.'

Fundamental knowledge

Physicist and philosopher Kian Salimkhani is delighted to be involved in the new Centre. ‘The most pressing questions in our field benefit greatly from interdisciplinary work, for us in particular combining mathematics and physics, both past and present, with conceptual, philosophical insights.’ He too points to the limited perspective of viewing matter only through the lens of physics. ‘Even the best physical theories are just models for a set of observed phenomena, without ultimately explaining the mechanisms behind them.’

A major theme in the work of Salimkhani encompasses in one sentence: what is ‘fundamental’ knowledge? Physics aims to shed light on fundamental properties, or say research into the fundamental structure of the world, he explains. But to understand what this ‘fundamentality’ entails, Salimkhani says, one has to look outside the realm of physics. Scientific case studies that can lead to further understanding are scarce, he says. At this point, there is a world to be won for philosophical reflection, precisely at the cutting edge of physics research. ‘These can help us bring clarity to what we mean when we talk about fundamental knowledge.’

Irrevocably paradoxical

The newly formed institute bears some resemblance to a few other centers around the world, though these can mostly be found in departments of philosophy. What is special about the Nijmegen Centre, besides the prominent role of mathematics, is that it moves freely within the three pillars of the triangle. ‘Accommodating this kind of research in a philosophy faculty has the disadvantage that the physicists then don't take you as seriously,’ says Borsboom. 'That they have to work with philosophers who don't understand physics very well. Even big names in physics can then be heard saying: ’Shut up, just let us just calculate’'.

The new Centre aims to further help science by setting up new experiments. Not so much those to be carried out with devices, but as thought experiments. These often involve the formulation of paradoxes, which for Borsboom is pre-eminently the field of activity of philosophers. Borsboom: ‘If you really dive deeply into the nature of matter, nature turns out to be irrevocably paradoxical.’

Impossible Triangles of Thought | Opening programme Radboud Center for Natural Philosophy | 9 and 10 January | https://rcnp.science.ru.nl/events/launch.html

Landsman's ‘dream team’ consists of three associate professors (Marij van Strien, Kian Salimkhani and Manus Visser), together with the PhD-students Silvester Borsboom and Karla Weingarten (the third PhD follows later this year).

Contact information

Organizational unit: Faculty of Science, Institute for Mathematics, Astrophysics and Particle Physics, Mathematics
Theme: Philosophy, Laws of nature