Heinrich Päs - Five Way Interview

Heinrich Päs is a German theoretical physicist and professor at TU Dortmund University. He received a PhD from the University of Heidelberg for research at the Max-Planck-Institut in 1999, held postdoc appointments at Vanderbilt University and the University of Hawaii, and an Assistant Professorship at the University of Alabama. His research on particle physics, cosmology and the structure of space and time was on the cover of the Scientific American and the New Scientist magazine. It also got included in the collector's edition Ultimate Physics: From Quarks to the Cosmos, next to a piece by Stephen Hawking. His latest book is The One.

Why physics?

Physics helps us to make sense of the universe. Both in the narrow sense, understood as space and time, stars and galaxies and the entire cosmic history, as in the more broad sense, as the myriad minds and things that populate the cosmos. Physics concepts help to elucidate economy and biology, neuroscience, information technology and traffic jams, weather, climate and pandemics, sports, music, arts, the list goes on… In that sense physics is something like a life philosophy that avails us to tackle all sorts of problems and questions. As such it makes our lives better and more easy, but for me the probably most important aspect is that it connects us to what the universe, deep down at the foundation really is. 

Why this book?

This is a book for everyone who wants to know what quantum mechanics, our best scientific theory, tells us about the fundamental reality. Everyone has heard about quantum mechanics, but few people realize that quantum mechanics usually isn’t taught as a theory about nature, but as a theory about our knowledge of nature. A humanity, rather than science. As soon as quantum mechanics is taken serious as a model for nature, it reveals a remarkable consequence, namely that the universe itself has to be understood as quantum object, and all seemingly individual objects in the universe are merged into this indivisible whole. This happens by fiat of a quantum process called 'entanglement', the topic of the 2022 physics Nobel prize. The universe itself, understood as a single quantum object, is the foundation physics should be based on. This is where physics should start, not with constituents as assumed in particle physics or string theory.   

Will it ever be possible to make testable predictions that distinguish this approach from others?

Adopting the universe as a quantum object doesn’t imply that we already have a concrete theory describing this quantum object. It is more a philosophy that should inspire theory building which isn’t a simple task. Once we have such theories, they will make predictions, and if we are lucky some of these predictions will be testable with the technological possibilities we have. In addition, there are gaps and open questions in our understanding of nature, such as how to describe gravity as a quantum field, what happens to information falling into black holes, why the mass of the Higgs boson is so small, and why the density of the dark energy accelerating the expansion of the universe is so tiny. My hope is that a paradigm shift away from constituents to quantum cosmology may help us to answer these questions.   

What’s next?

In fact physicists have already started to adopt a philosophy that takes quantum mechanics serious and puts it first. Research in this directions includes ideas that space and time may not be fundamental but emergent from a fundamental quantum reality beyond space and time. These are first steps only, not a comprehensive theory yet. Still, this past December, a group of physicists has published in Nature how such ideas are studied with Google’s quantum computer, by running a quantum algorithm that can be understood as a 'wormhole', a shortcut through space and time, in a 2-dimensional toy universe. Another consequence of entanglement may be that the physics at high energies and short distance scales isn’t independent of the physics at low energies and large distance scales. Earlier this year I have attended a workshop at the European center for particle physics CERN, where such phenomena and their possible consequences for particle physics have been discussed.  

What’s exciting you at the moment?

In physics I’m excited to ponder about such ways to probe a quantum notion of the universe and universal entanglement. My professional expertise is in neutrino physics, and neutrinos are tiny particles that interact extremely weakly. As a consequence, they are ideal probes for quantum processes. What’s more, a giant neutrino telescope in Antarctica has seen neutrinos with extremely high energies that originated long ago in far-away galaxies, properties that may help to elucidate a quantum nature of space and time.

I’m also interested in history and philosophy, and especially in the Renaissance age, which was pivotal in reviving ancient ideas about how everything is a part of one unified whole, ideas that are amazingly similar to what quantum mechanics teaches us about the universe today.  

But I’m most excited to see my three-year old son growing up. He loves water and the ocean, and we have a small sailboat. So I hope we can go sailing together this coming summer.

Interview by Brian Clegg - See all of Brian's online articles or subscribe to a digest free here