Originally posted by THUDandBLUNDER
What is your least upper bound for the longest possible game of chess?
If I understand your question correctly, your asking the maximum numbers of moves that can be done in a chessgame.
The answer is pretty easy, infinite. Rules like the 50-movesrule do not limit the length of the longest possible game. The problem with this rule (and with the threefoldrepetition rule) is that it needs to be claimed by either one of the players. If none do, the game goes on. (and on and on and on).
With that out of the way your question would proberbly be, but how long can a game last if one does claim a draw as soon as he/she can. OK then our problem would be the 50-moves rule stating that a draw may be claimed if there where no captures or pawn moves for 100 half-moves. The best thing to do is to start moving with the Knights and on the 50th move you play e2-e3 (or another pawn black or white). You can keep this up for quite a while but eventually you will have to capture and or promote. Enough with the talk lets calculate.
On a chessboard we've got a total of 16 pawns good for 7 moves each.
We've got a total of 30 pieces wich can be captured (capture the pawns after they've been promoted.) good for 1 move each.
Knowing this you should say the longest possible game should last (16x7+30) x 50 = 7.100 moves. But this is incorrect because in order to create passed pawns you need to capture with your pawn which wastes a move. In order to create 16 passed pawns you need to "waste" at least 7 moves. which shortens your game with a total of 7 x 50 = 350 moves. So the longest possible game by your means is 7.100 - 350 = 6.750 moves. (I hope your not playing by the limit of 40 moves in 2 hours).
Hope this answers your question.
A more interesting question to my would be. Know we know the longest possible game, what are the number of different games that can be played. I know the result would be a higher number the the total of drops of water on this planet. But still it is limited. I however don't know how to calculate this. (I get stuck on move 2 for white :-)) Has anyone else ever tried?