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Erdos Numbers

I sometimes moonlight as a math teacher or tutor and was having a discussion with some students about Erdos numbers while we looked at a graphic that represented exponential growth. Erdos was a famously collaborative mathematician who left behind many, many coauthors. I explained to the group that mathematicians and sometimes other academics keep track of their Erdos numbers.

“Do you have an Erdos number?”

“Yes.” The kids started passing me their math workbooks to sign. “Guys, this doesn’t count as coauthoring. Anyway, you don’t want to have a 5 or a 6—that’s not a great number,” I told them.

The following day, one kid said he might have an Erdos number because he wrote a story with another kid and that kid’s dad was a scientist and he probably had an Erdos number.

“Did your friend coauthor with his dad?”

“Uh, no.”

“Then your friend doesn’t have an Erdos number.” I told the group they should just learn a lot math before all the 1s and 2s retire and then try to find someone to write with when they grow up. Of course, that feels very far away when you are 10 or 11.

So, after thinking about it on my walk home, I reached out to an emeritus professor of mathematics who I know a little and asked if he might be willing to coauthor an article with the kids about his experiences meeting and working with Erdos. Professor Reznick met Erdos as a student and later as a professor and has an Erdos number of 1 (and a low Kevin Bacon number as well). He was willing to help, so I emailed the editor of the local paper to see if he’d like to run such an article. The parents and school were on board, and so the kids began to work on their questions for Professor Reznick.

They met the professor for the first time in person after the article came out and had a very nice hour with him. He showed them Pascal’s triangle and they asked him about Erdos’s ping pong skills.