The Shannon number, named after Claude Shannon, is a conservative lower bound (not an estimate) of the game-tree complexity of chess of 10120, based on an average of about 103 possibilities for a pair of moves consisting of a move for White followed by one for Black, and a typical game lasting about 40 such pairs of moves.
https://en.wikipedia.org/wiki/Shannon_number
| Number of moves | Number of possible games |
|---|---|
| 1 | 20 |
| 2 | 400 |
| 3 | 8,902 |
| 4 | 197,281 |
| 5 | 4,865,609 |
| 6 | 119,060,324 |
| 7 | 3,195,901,860 |
| 8 | 84,998,978,956 |
| 9 | 2,439,530,234,167 |
| 10 | 69,352,859,712,417 |
After each player has moved 5 times each (10 ply) there are 69,352,859,712,417 possible games that could have been played.
So they are saying that the number of possible moves in a chess game is:
1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,
000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,
000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,
000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,
000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,
000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,
Mike
Thats like "universe scale" numbers