Shannon number

The Shannon number, 10¹²⁰, is an estimate of the complexity of the chess game tree. It was first calculated by Claude Shannon, the father of information theory. Shannon calculated it in his publication Programming a computer to play chess.

According to his calculation, an average of 40 moves are made in a chess game, while each player chooses a single move out of about 30 possible ones (in fact, there may be zero possibilities as in cases of check). killed or drowned, or as many as 218). Thus, we have that (30×30)⁴⁰ are possible, i.e., 900⁴⁰ different chess games. Approximately, it is said to be equal to 10¹²⁰, a value obtained by solving the equation: 900⁴⁰=10^x. Solving, we have: x=40×log 900