Today, as I isolate myself with my family, observing social distancing while the world’s economies topple like flaming dominoes, the effect of small things, even things we cannot see on, well, everything, and the inextricable interconnectedness of all things great and small, hits home. It’s an idea that really begins with Alexander von Humboldt, who is the focus of a new and crucial exhibition, Alexander von Humboldt and the United States: Art, Nature, and Culture, at the Smithsonian American Art Museum. As “going viral” recovers its original, deadly serious meaning in our time, Humboldt’s brief six-week visit to the young United States in 1804 went viral in the current sense of the term. His visit and ideas might be said to be the vector that transformed the scientific, political and…