The legend of chess and the secret of exponential growth

The victory of Dacsina ensured a prosperous future for the kingdom and its subjects; however, the king could not find peace after the loss of his son and for this reason he spent his days tracing the movements of the troops in a box filled with sand, in order to understand where he had gone wrong and whether he could have somehow saved his son's life.

Having learned of this sad story, a young Brahmin named Lahur Sissa, humble and poor, repeatedly asked to be received by the king, but his request was always refused because the sovereign's state of mind was not suitable for receiving visitors. One day, finally, given his persistence, Iadava agreed to receive Sissa.

Standing before his sovereign, the young Brahmin showed the king the game he had invented for him: a board divided into sixty-four squares on which two groups of pieces were arranged, one white and one black. The various pieces could move according to established rules in a harmonious game of attack and defense centered around the most important piece, the one that could determine defeat or victory, namely the King. Sissa, in honor of Iadava, called this game shah, which in Persian means "king". Today it has been passed down to us with the name of chess.

By playing chess, Iadava understood that in order to win a battle it was necessary to sacrifice even the most important pieces, just as had happened in the battle of Dacsina, and that therefore the sacrifice of his son had not been in vain, but had been necessary to win the battle, which had brought prosperity and peace to the inhabitants of his kingdom.

To show his gratitude, Iadava offered Sissa to ask for anything he wished. The humble Brahmin asked to receive only rice. As for the quantity, the request was to place one grain of rice on the first square of the chessboard and to double the number on each subsequent square (one on the first, two on the second, four on the third, and so on). Surprised by such a modest request, the king agreed, but then realized that to fill the entire chessboard, the rice production of the whole world would not be enough.

To be precise, the solution to what is also known as Sissa's problem amounts to more than 18 quintillion grains of rice (18,446,744,073,709,551,615), which corresponds roughly to more than 500 trillion kilograms of rice, far exceeding current global production.