Peter Murray-Rust and the Concept of “Pauling Numbers”

Peter Murray-Rust

Peter Murray-Rust

We are delighted, on many levels, to have added Peter Murray-Rust’s blog to our gradually expanding Blogroll.  A faculty member of Churchill College at the University of Cambridge, Dr. Murray-Rust shares our interests in, among other topics, chemistry, xml and open access to information.

He and his team have developed a Chemical Markup Language, or CML, which is designed to help chemists represent chemical information through XML-based encoding.  He is also heavily involved with the open-source and open-data communities in attempting to facilitate the communication of technical knowledge across new media.  His blog, A Scientist and the Web, chronicles his work at the intersection of chemistry and technology, and serves as a combination of work log, diary, and long-term research publication.

Murray-Rust, as he notes in this post, has also written about Linus Pauling in the past.  One item that caught our eye was his suggestion that chemists consider the implementation of “Pauling numbers,” similar to the “Erdös numbers” adopted by mathematicians.  Erdös numbers are named after the famed mathematician Paul Erdös (1913-1996), a giant of the field remembered in nearly equal measure for his incredibly prolific scholarly legacy – his vita tallies nearly 1,500 academic papers, co-authored with 511 of his peers – and his loveably eccentric lifestyle.

(Briefly, Erdös spent the bulk of his career living out of a suitcase.  His habit was to travel from university to university or conference to conference, introduce himself to a colleague, declare that “my brain is open,” and stay until a paper or two had been generated.  He never married and had no children – mathematics was his life.  For those interested in learning more, the highly engaging biography The Man Who Loved Only Numbers: The Story of Paul Erdös and the Search for Mathematical Truth, comes highly recommended.)

The great Paul Erdös

The great Paul Erdös

The Erdös number is a measure of how closely a given scholar was able to collaborate with Paul Erdös at any given point amidst those 1,500 mathematical papers.  Murray-Rust describes the numbers using a definition supplied by Wikipedia:

In order to be assigned an Erdös number, an author must co-write a mathematical paper with an author with a finite Erdös number. Paul Erdös has an Erdös number of zero. If the lowest Erdös number of a coauthor is X, then the author’s Erdös number is X + 1.  Erdös wrote around 1,500 mathematical articles in his lifetime, mostly co-written. He had 504 direct collaborators [now updated to 511]; these are the people with Erdös number 1. The people who have collaborated with them (but not with Erdös himself) have an Erdös number of 2 (6,984 people), those who have collaborated with people who have an Erdös number of 2 (but not with Erdös or anyone with an Erdös number of 1) have an Erdös number of 3, and so forth. A person with no such coauthorship chain connecting to Erdös has an undefined (or infinite) Erdös number.

The Erdös number phenomenon has developed a rather potent subculture – see, for example, the painstakingly detailed Erdös Number Project hosted by Oakland University.  According to the Oakland database, Linus Pauling has an Erdös number of 4.  Murray-Rust is able to generate an Erdös number of 7 for himself, before promptly submitting to disqualification due to his linking paper making its way to Erdös through non-mathematical terrain.

From here Murray-Rust suggests that the world of chemistry follow the mathematicians’ lead and adopt the concept of Pauling numbers as a means through which contemporary chemists might navigate their way through the Pauling family tree.  As author of more than 1,100 publications – though, admittedly, not all on scientific topics – Pauling, whom Murray-Rust describes as “the chemist of the twentieth century,” certainly provides a large data set ripe for the mining.

We should like to add an additional note to something that Peter Murray-Rust mentions near the end of his Pauling Blog post:  “And finally a personal connection Catherine Murray-Rust was in the library at the time that the Pauling collection was being compiled.”  Now the Dean of Libraries at Georgia Tech, Catherine was, for several years, one of our bosses here in the OSU Libraries Special Collections.  We recall with fondness our collaboration together and wish her the very best in her current endeavors.

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