There is something particular with public lectures: they are meant to convey, in an hour or so, some — allegedly technical — message to a wilfully listening non-expert audience by precisely avoiding as much as possible any reference to esoteric concepts and jargon.
Such an undertaking appears at first sight to be quite impossible. After all, experts in all kinds of disciplines go through years of hardship and study at school/college/university before they can comprehend the newest or more subtle aspects of their subjects.
But does that matter actually? And, more importantly for the subject at hand, does it matter for a public lecture? I am inclined to say that it doesn’t.
In October 1931 Albert Einstein addressed a letter to the State University of New York at Albany in which he shared his views on education. In this letter he famously summarised his views on educational content by using the quote “education is that which remains, if one has forgotten everything “. In light of such a statement, when preparing a public lecture, I simply ask myself “what would my story look like if I had forgotten every technical bits about it?” and this sets the technical level I am aiming for.
Regardless of whether I am successful or not at this particular task, I find that I gain a lot myself with regards to my own understanding of the subject by seeking alternative non-technical narratives of some theoretical explanation of a natural phenomenon. Of course, I do hope that this enriched understanding eventually transpires during the delivery of the lecture itself. I believe that in addition to facilitating communication, this newly obtained understanding may also help in teaching and research as well. The history of physics is full of examples where the equations describing a phenomenon may not survive a paradigm change while the meta-narratives surrounding them remain mostly untouched (the concept of electron for example has survived both the quantum and quantum field theory revolutions for example and, maybe more subtly, the concept of energy is born from alternative narratives of Newtonian’s mechanics and has now outlived it in many respects).
Ok, fair enough, but if a public lecture cannot be technical and must be relatively short, what can the public expect of it then?
I personally aim for surprises in the spirit of how trained physicists may feel the first time they read the 1979 book Surprises in Theoretical Physics by Rudolf Peierls. A surprise, in this case, would be something that I say or show which would cause a mild cognitive dissonance in most people having a priori knowledge on the subject, in the same way that it surprised me the first time I was confronted to it. Of course, the goal is not to bring about discomfort in the audience but to surprise them enough that they will think about it after the lecture. Good sources of inspiration for me in that respect are the now quite popular Youtube Channels Veritasium and Vsauce.
Ultimately though, I strive to make contagious the many questions — and their manyfold tentative answers — I and many others may have about the natural world, no matter how naive they may look at first glance. And if by some miracle and a lot of hard work I can achieve this, then this is the best reward I can possibly ask for.