This is from a Yahoo article on Rubik's Cube:
One may suppose God would use a much more efficient algorithm, onethat always uses the shortest sequence of moves; this is known as God'sAlgorithm. The number of moves this algorithm would take in the worstcase is called God's Number. At long last, God's Number has been shown to be 20."
The research, published online, ends a 30-year search for the mostefficient way to correctly align the 26 colored cubes that make up Erno Rubrik's 1974 invention.
"It took fifteen years after the introduction of the Cube to find the first position that probably requires 20 moves to solve," the team said. "It is appropriate that fifteen years after that, we prove that twenty moves suffice for all position."