Dirac Number 2

1 The Number

My master's thesis adviser was Prof. Christie Eliezer, who was one of Dirac's very few research students (he worked under Dirac in the early 1940's). Since Eliezer worked with Dirac, he gets a Dirac number of 1 (analogous to 1 hop between nodes on the Internet). I get number 2 since I worked with someone who worked with Dirac.

The reason Dirac had so few students was, in part, due to his taciturn nature. Actually, taciturn does not capture the effect it could have on you. You really had to experience it to fully comprehend its impact (See Section 2.2). There is a famous story about Leopold Infeld who dreamt of working with Dirac. When he finally got to meet him as part of an interview for a research position, he came away in tears because nothing was said and Infeld knew immediately he could never cope with that total lack of personal interaction.

2 Dirac in Australia 1975

Dirac came to Australia in 1975. I don't recall why. Eliezer and I flew to Adelaide to visit him while he was visiting the Physics Dept. at the University under the auspices of Prof. Angus Hurst. On the weekend we went for a hike (Figure 1). It was rather cold, so people had their jackets and coats on. Naturally, only Cambridge types would be caught dead in a suit in the Australian outback.

Figure 1: The Proof (sort of): Dirac and Eliezer (middle) walking in the Adelaide Hills. I, of course, am the "genius" behind the camera; therefore, I forever lost the opportunity to say "This is me with Dirac!"

2.1 Up a Gum Tree

Dirac had a thing about trees. I had read somewhere that someone went to visit Dirac at his home in Cambridge and his wife (Wigner's sister) answered the door. When the visitor enquired if Dirac was home, she said that he was home, but he was up a tree.

During our walk (Figure 1), I had some confirmation of this story. I was walking in front of Dirac with some other people when I suddenly heard something like an animal moving quickly off to one side of the track. I turned around to discover to my astonishment that it was Dirac. He had taken off like a rocket up the slope (in Sunday suite and shoes, mind you) toward a gum tree. Apparently, he was fascinated by a particular tree and wanted to get a closer look at it. I was impressed at how he virtually sprinted up the hill, given that he was in his mid seventies!

Here is another explanation of Dirac's penchant for trees:

English physicist and Cambridge University professor Paul Dirac was an avid mountain climber and occasionally ascended such well-known peaks as Mount Elbruz in the Caucasus. In preparation for such excursions, Dirac would often climb trees in the hills just outside Cambridge - wearing the same black suit in which he was invariably seen around the university campus.

2.2 Dinner with Dirac

A dinner party was thrown for Dirac while he was in Adelaide. It was buffet style. While Dirac's wife was holding court in the dining room (some of us thought she was a real Brunhilde), Dirac snuck off into an adjacent, darkened room to eat his dinner. Since I noticed his stealthy departure, I soon followed and sat down beside him. This is where I suddenly learnt that he did not respond to small-talk at all.

To get around this silent treatment, I decided to ask him a physics question; about black holes, I think. Still no answer. It was impossible to know whether he hadn't heard the question, didn't have an answer (and was possibly embarrassed) or just didn't want to answer. It turned out to be none of these. Given that small talk is a social lubricant, it's quite distressing to get no response. It's like trying to loosen a rusty nut on a car wheel. You don't know whether to keep trying or simply give up. Physicists don't usually give up easily.

Suddenly, after what seemed like many minutes or possibly even tens of minutes, a very considered reply came back. It sounded like this. The trouble is even the mere idea of Dirac contributing to a conversation was by then so totally unexpected that I couldn't remember my own question, and I wasn't about to restart the process.

2.3 Dirac's Monoploe

Dirac gave three lectures while he was in Adelaide; all of which were quite boring because he talked about things he had done some 40 or 50 years ago (at that time) without providing any personal insight into how he developed some of those ideas.

The more exciting thing, it turned out, was news that Blas Cabrera at Stanford was claiming to have seen Dirac's magnetic monopole. If such a thing really existed, it would account for the size of the electric charge. I remember that Dirac got on the phone and talked with the experimental physicist Luis Alvarez at Berkeley. Dirac finally told us that he didn't believe Cabrera's results. He was right, but there was a hint of irony in that the inventor of the monopole didn't really believe in them.

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On 18 Apr 2006, 15:40.