How long is the longest possible chess game?

I've been thinking about this question for a while, and I feel like I've come up with a decent answer. Do you agree/disagree with my reasoning?

If both players collaborate to play an extremely long game of chess, what is the greatest possible number of moves in the game? (EDIT: The 50-move rule/threefold repetition are immediately enforced.)

My reasoning: Obviously, the main restrictors here are the following rules:

• Threefold repetition
• 50-move rule

However, since both players are collaborating, the former will be much less of an issue than the latter.

Now let's make the assumption that threefold repetition is immaterial; I feel confident that it can be avoided in most cases.

Now, suppose each pawn can promote, which gives us (50)(16*6)+49=4849 moves, since it takes 6 moves to reach the endof the board, there are 16 pawns, and we start with 49 moves, plus 50 extra for every pawn move.

But then there are also captures. In addition to those 4850 moves, there are 30 pieces that can be captured.

Hence, there are 4849+30(50)=6349 moves in the longest possible chess game.

Alright, I lied. If you've been keeping up, one obvious problem should have come to mind: Pawns cannot jump over each other.

Yep, that's an issue. If we are going to try to get around this by letting pawns capture each other, we'll lose a lot of possible pawn moves (at least 100/capture).

Then, instead, we can capture pieces. However, we are still going to lose 50 moves since we will be moving a pawn and capturing a piece simultaneously.

We need to do this 8 times, so there are 6349-8(50)=5949 moves in the longest possible game of chess.

If both players are truly collaborating to play the longest possible game neither is likely to claim a draw after repetion or 50 moves. :p

Exactly. One would have to imagine since this would be the case, that the longest possible game of chess is actually infinate moves long.

True. A draw by repitition or 50 move rule needs to be claimed. In theory if neither player claims the draw then a game can go on forever.

Well, if it was interesting to the OP then that's enough. Personally speaking I was actually interested enough to read through the enitre post.

Chess will be solved by quantum computing. The problem is, I don't know when they will be able to use computers at that tiny level. The answer is probably much less than 4300 whatever moves that many people claim. It's not too important to know this though.

Wow, everyone. I didn't mean for this to be a spam-fest. It was just an interesting problem I created.

You can assume that the 50-move rule is automatically enforced.

I'm actually not sure about your first solution. Having messed with some of Smullyan's problems I feel like you need to play through some games regarding the pawn captures in concrete positions because you may be missing something counting captures. Maybe I'm wrong and it will work but I'd have to see not all your moves played out but all your captures (or one example line with all your captures,) which is long, but totally doable and something you might want to do considering how much time you've devoted to the problem. It's not always intuitive counting vs what happens on the board. Changing the rules of chess for this problem does irk me a, though. It makes it less elegant. Also changing the rules to make draws easeir to achieve is the opposite of the way pretty much everyone wants to go when they do suggest changing the draw rules again which seems to come up every couple years.

What is the "50 move rule?"

I think that bound is too high.  The reason I think it is too high is that the paawns have to get past each other and it seems the only way to do that is with some captures on the way.  Since a capture also advances a pawn to the next rank you are allowing too may moves. 

Finding the exact answer is a serious pain in the butt. 

I once played an online game where my opponent rejected my draw offers. The game was clearly a draw. He kept making quick moves hoping to win by time. But it ended in a draw due to a 50 move rule.

my guess is around 17,919,808,491,568

If in 50 consecutive moves neither side captures a piece or moves a pawn, then either side can claim a draw.

thanks, macer75

Until one of the players dies.

Theoretically unlimited, neither player has to claim a draw at the 50-move rule.

The longest game with a decisive result (1-0 or 0-1) is 250-ish.

Was this ever a problem in the days a adjournments?

I've had a 350 move decisive game.

On chess.com?

Check out some of the tournaments here on c.c.