# question about new Rubik's cube proof (all solutions require \<= 20 moves)

**URL:** <https://boards.straightdope.com/t/question-about-new-rubiks-cube-proof-all-solutions-require-20-moves/549863>\
**Category:** Factual Questions\
**Created:** [August 10, 2010, 7:46pm UTC](https://boards.straightdope.com/t/question-about-new-rubiks-cube-proof-all-solutions-require-20-moves/549863 "2010-08-10T19:46:09Z")\
**Posts on this page:** 4\
**Page:** 2

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**Author:** ![Arnold\_Winkelried](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@Arnold\_Winkelried](https://boards.straightdope.com/u/Arnold_Winkelried)\
**Post date:** [August 11, 2010, 10:42pm UTC](https://boards.straightdope.com/t/question-about-new-rubiks-cube-proof-all-solutions-require-20-moves/549863/21 "2010-08-11T22:42:07Z")

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Update:

I e-mailed the guys at the webpage. They were very friendly and told me the following:  
The “superflip” they show has a 22-move process because they are using a java app to display the way to get to a certain position, and the java app calculated a 22-move solution. The page clearly states that it should be possible in 20 moves.

It is standard in the cubing community to count a 180° turn is one move instead of two. If you count 180° turns as two moves (which I thought you should do), then the “God’s number” (minimum number of moves to solve a worst-case scenario) would be somewhere between 26 and 29 moves.  
From the e-mail, discussing the case where 180° turns count as two moves:

> [@](#):
>
> Interestingly, only one position is known to require 26 moves–superflip composed with “Pons Asinorum” (perhaps the most well-known symmetric pattern other than the solved state).

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**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\
**Post date:** [August 11, 2010, 11:29pm UTC](https://boards.straightdope.com/t/question-about-new-rubiks-cube-proof-all-solutions-require-20-moves/549863/22 "2010-08-11T23:29:54Z")

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I presume that what they’re calling “Pons Asinorum” is the checkerboard? L2R2F2B2U2D2?

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**Author:** ![Arnold\_Winkelried](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@Arnold\_Winkelried](https://boards.straightdope.com/u/Arnold_Winkelried)\
**Post date:** [August 11, 2010, 11:54pm UTC](https://boards.straightdope.com/t/question-about-new-rubiks-cube-proof-all-solutions-require-20-moves/549863/23 "2010-08-11T23:54:33Z")

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I would assume so. That’s how it’s defined here  
[http://www.math.ucf.edu/~reid/Rubik/patterns.html](http://www.math.ucf.edu/~reid/Rubik/patterns.html)

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**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\
**Post date:** [August 12, 2010, 8:54pm UTC](https://boards.straightdope.com/t/question-about-new-rubiks-cube-proof-all-solutions-require-20-moves/549863/24 "2010-08-12T20:54:13Z")

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I’m surprised that there are multiple positions at the maximum number of moves. I had intuitively believed that there would be a single most difficult possible position, an “anti-solved” state.

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