Degrees of separation

by John Q on April 20, 2004

Following up the links on Eszter’s last post, I discovered that she shares with me an Erdos number of 3 (Eszter via Aronov and O’Rourke, mine via Fishburn and Wakker). This is pretty good for social science academics.

We thought this was worth a CT post, and came up with another issue. Although Movable Type and other systems encourage group blogging, they don’t, as far as I’m aware, allow for jointly authored posts. This is of particular interest since it’s at least arguable that a joint post would count as co-authorship for Erdos number purposes (this comes back to the question, frequently discussed on this blog, of whether and how blog contributions should be listed on vitas). But more generally, it would seem as if joint posts would be worthwhile for at least some purposes.

The Erdos number site asserts that numbers as high as 15 have been found, but that nearly everyone with a finite Erdos number is below 8. This seems about right, though mean, median and modal numbers must grow over time.



eszter 04.20.04 at 9:33 am

I reposted it on my blog signed as a joint post, but that required creating a separate account. Such an approach is too tedious for a group blog with 15 members though. There are too many possible permutations for joint posts.


Joseph O'Rourke 04.20.04 at 11:53 am

I am along the path from Eszter to Erdos that establishes her Erdos number. With Erdos now collaborating only with the angels, I cannot lower my number below 2. But Eszter can still decrement. In general the numbers drift downward over time, heading toward the source.

It will be interesting to see if another mathematician X emerges with enough respect and activity to warrant the honor of the community tracking X-numbers.


Brian Weatherson 04.20.04 at 8:56 pm

I don’t have an Erdös number yet, but if a couple of written but unpublished papers get published I believe I’ll have an Erdös number of 6. Since philosophers tend as a rule to write very few joint authored papers, there could be some very long Erdös chains winding through our part of the world.


matt 04.20.04 at 10:05 pm

At the risk of seeming dumb, what’s an erdos number?


eszter 04.20.04 at 10:23 pm

There were a few links in the post that lead to relevant info, but here’s a direct link to an explanation:


Matt Weiner 04.20.04 at 10:26 pm

Matt, Paul Erdos was a mathematician who went from place to place staying with mathematicians and co-authoring papers with them.
The Erdos number reflects how close you are to collaborating with Erdos. It is calculated as follows:
If you are Erdos, your number is 0.
If you have co-authored a paper with someone whose Erdos number is n, your Erdos number is at most n+1.
Inductive closure clause: Your Erdos number is the highest number consistent with the above.
My Erdos number is also 3, if you count forthcoming publications (Nuel Belnap-Joel Spencer-Erdos; see this page, via Eszter). Before that I think I probably had a high but finite Erdos number but I have no way of calculating it.
As the generations pass, I think the numbers will creep up very slowly, as there become fewer people with number 1 to collaborate with, then fewer with number 2, etc. But we won’t be around to see that happen.

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