Buy an Erdös number on eBay

Only three more days to buy an Erdös number of 5 on eBay!

For those not in-the-know, the late great Paul Erdös was a prolific mathematician and collaborator, which has made him something of the Kevin Bacon of the mathematics world. Erdös has an Erdös number of zero, any of his 200+ coauthors have an Erdös number of one, anyone who has coauthored a paper with one of them has an Erdös number of two, and so on. Now William Tozier, who has an Erdös number of 4, is selling his collaboration and thus an Erdös number of 5 on eBay. Current high bid is $364.

The interesting thing to me is that the price doesn’t seem to be following scarcity in this case. According to the Erdös Number Project, of the roughly 253,000 people who have collaborated on papers listed in the database of the American Mathematical Society’s Mathematical Reviews (MR), over 80% have an Erdös number, with the mode (most people) and median (mid-point) having an Erdös number of 5. (Heck, even I have an Erdös number of 5, and I’m not a mathematician.) You’d think the real prize would be to collaborate with R.G. Kamalov, who can boast 15 steps in his shortest path to Erdös and thus the largest finite Erdös number identified by the project.