Tower of Hanoi on the Web


Legend has it that a group of Eastern monks are the keepers of three towers on which sit 64 golden rings. Originally all 64 rings were stacked on one tower with each ring smaller than the one beneath. The monks are to move the rings from this first tower to the third tower one at a time but never moving a larger ring on top of a smaller one. Once the 64 rings have all been moved, the world will come to an end.

Until recently I have believed with my reference Dictionary of Mathematics that the Tower of Hanoi puzzle is of ancient Indian origin, as the above rather widespread legend would also suggest. But it seems that it was actually invented from scratch probably together with the accompanying legend only in 1883 by the French mathematician Edouard Lucas. At least there is no known written record about the puzzle or the legend prior to 1883.

Professor Lucas called his invention "Tower of Hanoi". The singular refers to just one tower of disks to be dismantled and reassembled on a different peg. My dictionary and many other sources from the past 25 years use the plural, "Towers of Hanoi". This could reflect a growing belief in the ancient origin of the puzzle (the legend speaks about three towers - one could imagine three pyramidal pagodas with rather thin golden rings placed on their slanting roofs), or it could simply reflect the fact that the language is a living entity whose continuous evolution is impossible to stop. I have done a little survey of the sites listed below, and I found that about 26 of them respect the name given to the puzzle by its inventor and use the singular "Tower of Hanoi", whereas about 29 of them use the plural "Towers of Hanoi".

Illustration from the box of the original Tower of Hanoi puzzle of E. Lucas