13th July: The Rubik's Cube

13 July is the birthday of Dr. Erno Rubik, born 1944, the inventor of the Rubik's cube.

1. The Rubik's cube is the world's best selling puzzle game. 350 million of them had been sold by 2009.
2. Dr. Rubik didn't set out to make a puzzle. He wanted to show his students how to make an object with moving parts that could be moved independently of each other without the whole thing falling apart. It was only when he scrambled it and then tried to put it back again that he realised it was a puzzle.
3. Rubik obtained Hungarian patent HU170062 for his "Magic Cube" in 1975, and it appeared in Budapest toy shops in 1977. An international deal was signed in 1979, so its first appearance at toy fairs worldwide was in 1980.
4. It could have been called "The Gordian Knot" or "Inca Gold" - both names were considered before "Rubik's Cube" was chosen.
5. A standard Rubik's Cube measures 5.7 cm (approximately 2¼ inches) on each side and has twenty-one pieces - a single core piece consisting of three intersecting axes holding the six centre squares in place, and twenty smaller plastic pieces called "cubies" or "cubelets" which fit around it.
6. Marketing blurb says that the cube has "millions" of permutations. The actual figure is approximately 43 quintillion. If there were as many standard sized Rubik's cubes as permutations they would cover the Earth's surface 275 times. If you allow for taking the cube apart there would be 519 quintillion permutations, although only one in twelve of these would be solvable.
7. The first cube-solving championship was held in 1981 in Munich and was organised by the Guinness Book of World Records. The Cubes were moved 40 times and lubricated with petroleum jelly. Jury Froeschl from Munich won, solving the cube in 38 seconds. The current world record was set by Collin Burns of the United States in April 2015 with a time of 5.25 seconds. A cube has been solved in the even shorter time of 3.25 seconds: by a robot: CubeStormer III, built using Lego Mindstorms and a Samsung Galaxy S4.
8. There are also contests and records for variations of cube solving methods. These include: solving it blindfolded (the solver has to memorise the permutation before the blindfold goes on. The record is held by Marcin Kowalczyk of Poland - 21.17 seconds (including memorisation) in 2014; solving the cube with one hand (record 6.88 seconds by Feliks Zemdegs in 2015); solving the cube with the feet (record Gabriel Pereira Campanha in 25.14 seconds in 2014). There are also people who try to solve the cube underwater in a single breath.
9. The standard cube is 3x3x3. A Greek inventor, Panagiotis Verdes, patented the means to make cubes up to 11x11x11 in 2003. A 17x17x17 model exists and the record for solving that one is seven and a half hours, by Kenneth Brandon. Computer software can go even further and simulate 100×100×100 and 1,000×1,000×1,000 cubes, and four or five dimensional cubes.
10. The largest cube ever built was 30 feet tall and was built by a team of artists in Seattle for the Burning Man festival in 2009. It was even possible to solve it, by using an electronic control station.