Video: A student at Florida Institute of Technology shows how a robot can solve a Rubik’s cube, thanks to software called Cube Explorer (Footage courtesy Florida Institute of Technology)
ERIK AKKERSDIJK holds the world record for doing it in 7.08 seconds (watch a video). Thibaut Jacquinot does it with one hand (watch a video). Seventeen-year-old Joey Gouly likes to do it blindfolded and Zbigniew Zborowski has done it a staggering 3390 times in one day. They are all experts at solving the Rubik’s cube, the must-have toy of the 1980s and one of the most popular games in history.
Since the first world championship was established in 1982, the record for solving the Rubik’s cube has been slashed from 19 seconds to just over 7 seconds. But it’s not just gamers who are interested in solving the Rubik’s cube. Mathematicians are just as fascinated by this toy. For them, the question is: how many moves are needed to solve a maximally jumbled-up Rubik’s cube? In other words, what is the smallest number n for which you can be sure that no configuration will require more than n moves to solve?
The answer isn’t as straightforward as it might seem. If you take a completed cube and jumble it up by rotating its faces at random 25 times, it’s obvious that you can solve that cube in 25 moves. But that’s no guarantee that it couldn’t be solved in fewer than 25 moves, and mathematicians are interested in the optimal solution – the shortest way to solve any given configuration. Admittedly it’s a bit of a fringe problem, but mathematicians take this issue deadly seriously; ...