Something About the Number of Possible Chess Moves

Maybe I should Stick to Twenty Squares!

I am still trying to find something to get involved with, and since I had written a few posts referencing The Chessmen of Doom (1989), I thought I’d go for at least one more. A few months ago, I mentioned how many books in the Johnny Dixon series mention chess. (I also mentioned three books in the series do not...did you figure out which three?). More to the point, I wondered how many games Johnny, Professor Childermass, and Fergie played and how many more they could have played. That is, how many possible chess games are there?

Turns out, it’s a thing. David Kinney noted the following bit at Popular Science about the vastly, hugely, mind-bogglingly big number back in 2010:

According to Jonathan Schaeffer, a computer scientist at the University of Alberta who demonstrates A.I. using games, "The possible number of chess games is so huge that no one will invest the effort to calculate the exact number." Some have estimated it at around 10100,000. Of those, 10120 games are "typical": about 40 moves long with an average of 30 choices per move.

This number is the Shannon Number, and I’ll let Dr. James Grime speak about it in his Numberphile video: