Theoretical Physics in the 21st Century

I gave a talk at the Zürich Theoretical Physics Colloquium for Sustainability Week 2021. I was excited to get a chance to speak both about the future of theoretical physics and the climate crisis.

You can see a video of my talk, and also my slides: links in blue on my slides lead to more information.

Title: Theoretical Physics in the 21st Century.

Time: Monday, 8 March 2021, 15:45 UTC (that is, Greenwich Mean Time).

Abstract: The 20th century was the century of physics. What about the 21st? Though progress on some old problems is frustratingly slow, exciting new questions are emerging in condensed matter physics, nonequilibrium thermodynamics and other fields. And most of all, the 21st century is the dawn of the Anthropocene, in which we will adapt to the realities of life on a finite-​sized planet. How can physicists help here?

Hosts: Niklas Beisert, Anna Knörr.

14 Responses to Theoretical Physics in the 21st Century

  1. ecoquant says:

    I’m not a physicist, even if I my B.S. is in Physics. But what I’m intrigued about is the applicability of certain concepts to biology, even how life forms exploit complicated physical phenomena.

    One that I’ve been intrigued by (references available if wanted) is fluid boundary layers. Whether a creature is anchored to the floor of a stream, or is growing on the floor of a forest, they are enveloped in a boundary area, the first of water flow, the second of air flow. Both settings see creatures learning to exploit this. In the first, when they want to eat, they’ll extend tendrils or tentacles up into the flow regime, and pull them back. In the second, in the case of mosses, they’ll grow setae tall enough to probe the flow layer and that’s where they’ll dump spores.

    I’ve also thought that the geometry of sessile creatures like mosses and lichens might contribute to their vitality. Certainly, acrocarpous mosses like Polytrichum have a neat trick of curving their leaves in, forming a kind of tube.

    This serves two functions. It protects water in the interior from evaporation, protecting against desiccation. Also, in the absence of water, when rain is about, the capillary action of the tube conducts water within it to be stored, and surface tension assures that actually it’s held as well as if it were entirely enclosed. Recall the relative importance of surface tension of water for things at this scale. So physics gives us the ability to imagine correctly what the needs and realities are for creatures at different scales.

    The connection with climate disruption is deep. While mosses, I daresay, will have no trouble as a division to survive anything we accidently or not throw at them (they’ve been around since the Ordovician), they have also changed the world’s climate on their own, albeit slowly.

    This can matter because mosses aren’t the only plants that play boundary layer games. Indeed, there isn’t a boundary layer, there are boundary layers, depending upon the intensity of flow that’s to be avoided or exploited. For Earth, trees can be considered being in a boundary layer, even if, when doing so, they sap energy of storm systems which need to flow over them. There are even engineering problems which could be informed: Build enough wind turbines, and they will sap energy out of passing storm systems (Jacobson, 2021, section 6.9.1).

    I don’t know if there are systems of bounds which could be constructed to describe, say, atmospheric flow over forested lands, versus flow over deserts, and, say, a Sankey Diagram of where trapped energy from local flow eddies goes in terms of its interaction with the local biosphere and how much goes elsewhere. These might be useful.

  2. Keith Harbaugh says:

    John, have you written an explanation of what Urs, David Corfeld, and David Roberts are talking about in this thread: ?
    Is there, somewhere, anything introductory on that?

    • John Baez says:

      That thread is about a brand-new paper by Urs Schreiber and Hisham Sati. I used to work on higher categories and physics, but not anymore. It’s not the sort of thing where one can just read a bit now and then and then explain it to everyone. This is an introduction to some of Urs Schreiber’s ideas:

      • Branislav Jurco, Christian Saemann, Urs Schreiber, Martin Wolf, Higher structures in M-theory.

      • Keith Harbaugh says:

        Thanks very much for that reference. There is quite a tower of ideas and theories that they have ascended.

  3. bhaugen says:

    That was a great presentation! Hoping the slides become available soon, and I can cite them.

    • Yes, I was there. Certainly better than nothing. I see the problem with flying to conferences. (Fortunately, I live in the middle of Europe and can (and do) drive to most conferences with my electric car.) However, as the famous quote (see below) says, conferences are like medieval pilgrimages. Yes, there is a goal, but things which happen along the way are at least as important, and most of those don’t happen with video conferences. One could even argue that the ostensible purpose of conferences can be fulfilled without an actual conference these days, but there is no substitute for other stuff.

      The modern conference resembles the pilgrimage of medieval Christendom in that it allows the participants to indulge themselves in all the pleasures and diversions of travel while appearing to be austerely bent on self-improvement. To be sure, there are certain penitential exercises to be performed—the presentation of a paper, perhaps, and certainly listening to the papers of others. But with this excuse you journey to new and interesting places, meet new and interesting people, and form new and interesting relationships with them; exchange gossip and confidences (for your well-worn stories are fresh to them, and vice versa); eat, drink and make merry in their company every evening; and yet, at the end if it all, return home with an enhanced reputation for seriousness of mind. Today’s conferees have an additional advantage over pilgrims of old in that their expenses are usually paid, or at least subsidised, by the institution to which they belong, be it a government department, a commercial firm, or, most commonly perhaps, a university.

                            —David Lodge

      • John Baez says:

        Phillip wrote:

        One could even argue that the ostensible purpose of conferences can be fulfilled without an actual conference these days, but there is no substitute for other stuff.

        Maybe we can return to the old style of pilgrimages where people walk a hundred kilometers or so to get to a conference, talking with other like-minded people on the trip. It could easily be more productive of new ideas than flying somewhere and flying back.

        • There are things like that, such as a cosmology conference which consists of non-trivial hikes in the Alps. But the problem is that most people still have to get to the Alps. :-|

          Probably the main reason that people in the U.S., emit 4 times as much carbon dioxide as in Switzerland is the lack of efficient public transportation.

          But, of course, one needs to concentrate on actual problems. In a populist move (because opinions have changed), more and more parties are advocating a speed limit on German highways for environmental reasons. As John said in his talk, you have to look at the numbers. A speed limit on German highways would reduce Germany’s carbon-dioxide emissions by a whopping one half of one per cent. If done at all, there should be exceptions for electric cars, at least if charged with green energy, and of course it is absurd to have a huge SUV which uses more fuel going slow than a subcompact travelling at twice the speed.

        • I’ve sometimes seen people fly in just to give their talk, or even for the opening speech. (The only thing more absurd would be flying in just to give the conference summary.). Those are usually relatively well known people, and the conference thinks that it is worth it to have them (and pays their way), and it strokes the egos of those invited. But, at least these days, one can probably find a better version of the talk on the web. The main point of a conference are the many conversations which take place outside of the talks. For that reason, I prefer to go to conferences where everyone stays and eats in the same place.

          Then there are those people who stay almost a week or whatever, but then leave a few hours or a day earlier. I’m convinced that many of those aren’t actually going somewhere important, but want people to think that they are. :-|

          On the other hand, electric planes are being developed, and if charged with green electricity, we can fly again with a good conscience.

    • John Baez says:

      Bob Haugen wrote:

      Hoping the slides become available soon, and I can cite them.

      Thanks! Here they are:

      Theoretical physics in the 21st century.

      Later a video should become available… they need to edit it a bit first.

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