Thursday, June 9, 2011

My Erdös Number

Many people have heard of the "6 Degrees of Kevin Bacon" game, introduced in 1994, where you try to connect a famous person to the actor Kevin Bacon within 6 connections, e.g. X acted in a movie with Y who acted in a move with Kevin Bacon gives a Bacon Number of 2 for actor X and 1 for actor Y.  The idea of six degrees of separation originated in the early 20th century (of course, not with Kevin Bacon) when Frigyes Karinthy conjectured that any 2 people could be connected through at most 5 people.  This was the basis of the Small World Experiment in 1967 by social psychologist Stanley Milgram.

Long before the Bacon Number in the entertainment industry was the Erdös Number (you can also view the Erdös Number Project page) in mathematics.  Paul Erdös was a prolific mathematician authoring the most academic papers in history, many of those in collaboration with others (at least 1,525).  It became a anecdotal measure of prominence in the field to have a low Erdös Number.  So much so, that the American Mathematical Society has a tool to calculate your Erdös Number based on their database of mathematical papers (click here to go to the tool and select the "Use Erdös" button, try "Einstein, A" and you should see his Erdös Number is 2).  Studies seem to show that, if a person has a finite Erdös Number (meaning, have you published a paper with another author that you can use to start your connection), that number is at most 15 with a median number of 5.  It turns out that my number is 5:

1: Paul Erdős & Mark Kac
    Erdös, P.; Kac, M. "The Gaussian law of errors in the theory of additive number theoretic functions",  Amer. J. Math.  62,  (1940). 738–742.
2: Mark Kac & Subrahmanyan Chandrasekhar
    Chandrasekhar, S., Kac, M., Smoluchowski, R., "Marian Smoluchowski: his life and scientific work. Chronological table and bibliography compiled by Alojzy Burnicki. Edited and with a preface by Roman Stanisław Ingarden", PWN---Polish Scientific Publishers, Warsaw, 2000. 141 pp. ISBN: 83-01-00671-4.
3: Subrahmanyan Chandrasekhar & James B. Hartle
    Chandrasekhar, S., Hartle, J. B., "On crossing the Cauchy horizon of a Reissner-Nordström black-hole",  Proc. Roy. Soc. London Ser. A  384  (1982), no. 1787, 301–315.
4: James B. Hartle & Kip S. Thorne
    Thorne, Kip S., Hartle, James B., "Laws of motion and precession for black holes and other bodies",  Phys. Rev. D (3) 31 (1985), no. 8, 1815–1837.
5: Kip S. Thorne & Amber L. Stuver
    B. Abbott, et al., "Detector description and performance for the first coincidence observations between LIGO and GEO," Nucl. Instrum. Methods A 517 (2004), 154 – 179. 

Special thanks to Nathan Urban for finding this low Erdös Number for me (using the tool listed above) - the best I was able to come up with was 8 with a manual search.

NOTE:  I have a revised Erdös Number of 4 - see my next blog post.

Do you have an Erdös Number?  Post it and your connections as a comment below!

Random picture for today's blog: an honest to goodness black widow spider I found dead behind the LIGO Science Education Center today (in Louisiana):