Dirac Number 2
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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