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The Man Who Found God’s Number

by David Joyner

Year of Award: 2015

Award: Pólya

Publication Information: College Mathematics Journal, vol. 45, no. 4, September 2014, pp. 258-266.

Summary (adapted from the MAA Prizes and Awards booklet for MathFest 2015)David Joyner splendidly recounts the tale of two problems---and the taleof two triumphs. In the early 1980s, high school junior Tomas Rokicki began losing his hearing, and received a Rubik’s Cube as a gift. As Tom’s hearing began to decline, he continued his work at solving a fundamental problem associated with Rubik’s cube: determining the minimum number of moves required to solve the cube from a worst-case scenario “scrambled” position. This number has come to be called “God’s number.”

The author goes on to describe the mathematics of Rubik’s Cube. The Rubik’s Cube group G is a subgroup of the symmetric group on 48 letters. The reader is led through an overview of the technical features of the structure of G. Meanwhile, the reader learns that Tom earned a Ph.D. in computer science at Stanford, while suffering from greater and greater hearing loss. But breakthroughs continued to be made in both the determination of God’s number and in the science and technology of restoration of hearing loss. With the help of supercomputer time donated by Google and by Sony pictures, in 2010, Tom and his colleagues determined that God’s number in the face-turn metric is 20. 

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About the Author: (From the MathFest 2015 MAA Prizes and Awards Booklet)

David Joyner received his Ph.D. in mathematics from the University of Maryland, College Park. He held visiting positions at the University of California San Diego, Princeton, and the Institute for Advanced Study before joining the United States Naval Academy in 1987, where he is now professor. He received the USNA’s Faculty Researcher of the Year award in 2007. His hobbies include writing, chess, and photography.