Over the past two weeks I had the pleasure of giving a series of colloquia at RWTH Aachen, U. “La Sapienza” Rome, U. of Zurich, Santa Fe, and ITC Harvard, presenting some recent work on a new and exciting frontier: the use of gravitational waves to probe the nature of dark matter.

The idea is simple. Real black holes do not live in vacuum. They are embedded in environments that may contain gas, stars, and perhaps dense concentrations of dark matter. If those surroundings affect the motion of compact objects spiralling inward, they can leave subtle but potentially measurable imprints on the gravitational-wave signal. With future detectors such as LISA, these effects may come within observational reach.

What makes this direction so interesting is that it adds a new perspective to a very old problem. For decades, dark matter has been pursued through collider experiments, direct detection, and more conventional astrophysical observations. Gravitational-wave astronomy may now offer a different angle: not by looking for dark matter directly in the laboratory, but by using the dynamics of black holes as a way of exploring the dark sector.

This is still a young area, but one that is beginning to gather energy – at the intersection of gravitational-wave physics, cosmology, black-hole astrophysics, and particle theory.

I am very grateful to all the colleagues and hosts in Aachen, Sapienza, UZH, the Santa Fe Institute, and Harvard for the invitations, the hospitality, and the stimulating conversations.

Here is the video of my colloquium at ITC Harvard:

Last week I had the pleasure of visiting the Santa Fe Institute, where I was hosted by Melanie Mitchell, a SFI professor working at the intersection of artificial intelligence, cognitive science, and complex systems, and also a recent finalist of the Cosmos Prize.

The Santa Fe Institute (SFI) is a rather unusual place in the scientific landscape. Founded in the 1980s by a group of physicists, economists and biologists, it was conceived as a space where researchers could explore problems that do not belong neatly to a single discipline. Complexity science is the common language: systems in which many interacting parts produce collective behavior, from biological evolution and ecosystems to markets, social institutions and artificial intelligence.

What makes SFI special is its intellectual atmosphere. People are encouraged to move freely across disciplinary boundaries, asking questions that might sound naïve in a specialized department but that sometimes turn out to be exactly the right ones. Conversations shift between physics, anthropology, computer science, economics and philosophy, and one is constantly reminded that many of the most interesting scientific problems live between fields rather than inside them.

During my visit I gave a seminar on dark matter, focusing on the epistemology of discovery: how scientists infer the existence of invisible phenomena, how competing models evolve, and how the limits of observation shape our understanding of the universe.

But the highlight of the visit was really the opportunity to spend time in individual conversations with SFI scholars.

With Sam Bowles, one of the leading thinkers on the evolution of cooperation and economic behavior, we discussed how institutions can shape human preferences and social norms. We also talked about the deeper political tension this raises: societies depend on norms such as trust, reciprocity and civic responsibility, yet attempts to deliberately cultivate such norms immediately raise fears of social engineering. One of his most striking observations was that institutions influence behavior less through explicit persuasion than through the daily patterns of interaction they create. Interestingly, he also pointed to nationalism, despite its dangers, as historical evidence that human beings are capable of expanding their circle of solidarity far beyond immediate kin or tribe. Can globalism help us do the same across national (and other) boundaries?

With Fred Cooper, our conversation moved in a very different direction. We discussed forms of knowledge that precede conceptualization: ways of engaging with reality that are not primarily analytical. That discussion unexpectedly evolved into a short session of Buddhist meditation exercises, exploring attention and perception as tools for understanding the world before it is framed in concepts.

I also had fascinating discussions with Cris Moore and Melanie Mitchell about the role of artificial intelligence in science and society. One refreshing aspect of these conversations was how quickly the discussion moved beyond the familiar polarized narratives that dominate public debate: the oscillation between technological doom and utopian optimism. When those voices are absent, the discussion becomes far more interesting and nuanced.

With James Holehouse, we discussed the role of regulation in complex systems, from biological organisms to social institutions, as well as the importance of communicating science effectively to the broader public. We also talked about writing for general audiences and the challenges of translating scientific ideas without oversimplifying them.

Finally, I had a stimulating exchange with Marina Dubova about the role of concepts in science. Her work explores a deceptively simple question: what epistemic functions do scientific ontologies actually play? Her answer — which resonates strongly with my own interests — is that scientific concepts are not merely labels for things in the world. They are perspectives that shape every stage of scientific work, from the way data are collected to how results are interpreted and communicated. In that sense, improving scientific concepts cannot be separated from understanding how those concepts have already shaped the scientific process itself.

The visit was also an opportunity to learn more about the history of New Mexico and Santa Fe, including the complex history and present status of Native American communities. Santa Fe itself is a remarkable place: a city where Indigenous traditions, Spanish colonial history, and contemporary culture coexist in a unique way. The local art scene is particularly vibrant, with galleries, museums and public spaces that reflect this rich cultural history.

In the end, what makes the SFI memorable is not (only) the work being done, but the conditions they create for thought. Unstructured interactions, bold questions, and conversations opening freely onto unexpected terrain. The SFI remains one of those rare places where this still happens.

I just returned from an inspiring conference in Göttingen, organised by the German Physical Society to celebrate 100 years of quantum physics.

It was in the summer of 1925 that Werner Heisenberg, seeking relief from his hay fever on the island of Helgoland, drafted the paper that changed physics forever. Back in Göttingen, together with Max Born and Pascual Jordan, he developed the first mathematical framework of the new theory — known as matrix mechanics — which marked the birth of modern quantum physics.

The conference was a chance to look back at that extraordinary moment in history, but also to see how far the field has come. We heard fascinating talks from Nobel Prize winners and leading scientists — Anton Zeilinger, Serge Haroche, Wojciech Zurek, Klaus von Klitzing, Beate Heinemann, Jürgen Renn and many others — who are pushing the frontiers of quantum physics today. A highlight was a round table I joined with Zeilinger, Zurek and Fröhlich, discussing what quantum physics has taught us — and what mysteries remain.

In my own talk, I spoke about the “quantum roots of the universe”. I began with astronomy as it stood in 1925, when Henrietta Leavitt’s work on Cepheid stars and Edwin Hubble’s discovery of the Andromeda galaxy were just emerging, at the very same time quantum mechanics was being born in Göttingen. From there, I turned to today’s puzzles: dark matter, dark energy, and the Big Bang, and I also showed how future gravitational-wave observatories may help us solve these mysteries. If you’re curious, here are my slides (link to pdf, 8Mb).

The meeting was also the occasion to pay respect to the many great scientists buried in Göttingen. The city’s cemetery is the resting place of nine Nobel laureates and other towering figures, including Max Planck, Max Born, Max von Laue, Karl Schwarzschild, David Hilbert, and many others who shaped the history of modern science.

Another memorable moment was the conference dinner at the historical Gauss Observatory, allegedly built to lure Carl Friedrich Gauss to Göttingen as director. Gauss, later celebrated as the princeps mathematicorum — the prince of mathematicians — made it his scientific home. Dining in that setting was a special way to connect with Göttingen’s outstanding scientific heritage.

A huge thank you to the organisers — Stefan Kehrein, Thomas Weitz, Johanna Stachel and many others — for a wonderful and memorable meeting.