A 5th century medallion showing what is perhaps the only portrait we have of Galla Placidia (388-450 c.e.), the last (and the only) Western Roman Empress. The inscription says "Domina Nostra, Galla Placidia, Pia, Felix, Augusta," that is "Our Lady, Galla Placidia, Pious, Blessed and Venerable." A contemporary of such figures as Saint Augustine, Saint Patrick, Attila the Hun, and – perhaps – King Arthur, Placidia had the rare chance of being able to do something that past Roman Emperors never could do; take the Empire to its next stage which was to be, unavoidably, its demise.
As I was preparing this essay on Empress Galla Placidia, I found myself giving an impromptu talk on the subject to my students in chemistry on the last lesson before Christmas. Later on, I thought that I could write my essay in the form of that talk. So, here it is. It is much expanded in comparison to what I said to my students on that occasion, but still it maintains the essence of it. I have added headings and some figures.
Introduction: chemistry of an empire
I think there won't be a lecture in chemistry, today. We are close to Christmas, there are just a few of you, and so it is better to skip a long and boring lecture; we'll have it after the pause for the holidays. So, we could simply leave for a coffee but, maybe, we could use this time we have in a different way. You know, there is a subject that I work on when I have some free time: Roman history. So, I was thinking that, instead of giving you a lecture in chemistry, I could speak to you about that. How would you like to hear the story of a Roman princess who married a barbarian king and then became Empress of Rome?
Now, I see from your faces that - yes - you would like to be told this story! But note that perhaps it is a subject that is not so far from chemistry as you might think. You see, civilizations can be seen as huge chemical reactions and you know that chemical reactions tend to flare up and then subside; it is what we call "chemical kinetics," you have studied that. The same happens for empires; they tend to flare up and then disappear; that's what happened to the Roman Empire, as you know. So, civilizations and chemical reactions can be studied using similar methods; it is a field of science that goes under the name of "system dynamics". In a sense, there are forces pushing people to do things just like there are forces pushing molecules to react. In chemistry we call those forces “chemical potentials”, about people we might use the term “destiny” or "karma" or something like that. But perhaps the difference is not so great.
But don't worry about equations. I said that today I was going to tell you a story, and I am going to do it. It is the story of Galla Placidia; born a Roman princess, then Queen of the Goths, and, in the end, Empress of Rome. It is a great story of love, sex, and war. So, let's start!
The fall of Rome.
Now, I am asking you to close your eyes and forget for a moment where you are. Forget that you are in a classroom, forget that you are students of chemistry, forget that you live in the 21st century. Try to imagine something that existed way back in time: ancient Rome in the first years of the 5th century of our era, fifteen hundred years ago.