Events can correlate with one another in unpredictable ways. I have encountered three examples—as follows.

At a conference at Cornell University on heavy-ion effects in solids, during cocktail hour, I met a guy who came from Finland. I noted that I knew only one person from there—one who had visited Cornell during earlier years—Juha-Pekka Hirvonen. The response was, “He’s my thesis professor!”

The next scene is in the dining car of the auto train, from the Reston station near the District of Columbia to Sanford near Orlando, Florida. It is a relaxed atmosphere with no passenger stops until arrival down south, and my wife and I naturally started talking with the lady who shared the dinner table with us. She turned out to be from Warren, Ohio. Remembering a fellow in my dorm during the freshman year in college, “I know only one person from Warren. His name is Bill Letson.” Her response: “He’s our best friend and trusted family lawyer.”

While waiting near a reception desk at the Mayo Clinic in Rochester, Minnesota, I heard a fellow checking in with his name, “Cartwright.” I restrained myself from saying I know only one person with that name (I knew of two, one of whom was dead). I did approach him to ask if his first name was Brian. After a “Yes,” I asked whether the University of California at Berkeley, Buford Price, and CR-39 meant anything to him.

He replied, “Yes, yes, and yes. Who are you?” I identified myself as a long-time associate of his PhD professor, Buford Price, and therefore well aware of the important work he had done with Price in developing the special nuclear-track-detecting plastic CR-39. Because it is sensitive to alpha particles, CR-39 allows radon measurements of improved quality. It is widely used in such applications (and many others). One example rom our work at Union College is using the tracks in CR-39 eyeglass lenses to find average radon exposure of the wearers.

These encounters are unexpected and surprising. I wonder whether there are some hidden connections that make their occurrence statistically more reasonable than they first appear. For the first example, the fact that Hirvonen had been at Cornell earlier increases the likelihood that he would send a student for a meeting in his area at a place he knew well. But it still looks unlikely that the student and I would meet.

The other two cases do not suggest to me any likely hidden connections. The events—riding on a train and going to a medical facility—are not ones that suggest any mechanism for expecting close associations.

What is one to make of these three events happening to a single person? One alternative is to assume that over time one accumulates so many associations and personal contacts that connections become much more likely than one recognizes. Another possibility is that the results of my experience are just unusual excursions from those of the average person. (If it were not, I would have not written this note.) It would be helpful to know whether readers of this note feel they have had an unusual abundance of similar experiences. (My e-mail is given below.)

It is an often-quoted idea that by a series of no more than six associations, one can connect any two people on earth. However, the old radio program “Twenty Questions” showed that 20 attempts were often not sufficient to establish the route from a thought to its identification. So, while six may make something possible, the probability may be low.

Meanwhile, some years ago, in a long line of people awaiting a tour of the Vatican, my mother—who was seldom inclined to preserve silences—struck up a conversation with a nice-looking English couple just ahead of her. The man turned out to be a professor at Harvard.