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Comment by DrScump | Hacker News Reader

Why is it always solved in the same final orientation? (red to near left, blue to near right, ...)

It would seem to me that from a truly random start point to the truly fewest-moves solution, the colors would end up facing random orientations for each run.

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Because within the cube, the centerpieces are fixed to a core. And because these define the orientation of the cube and are fixed within the robot you end up having the same orientation every time. This happens with every solving robot that only turns the outer layers of the cube, meaning the inner layers and therefore the centerpieces do not move.

It's mathematically interesting that the optimal solutions (I assume that the robot uses the fewest-moves-possible to get its high-speed results) never require rotating the middle layers.

On closer look it's actually trivial. Any move that requires rotating a middle layer is isomorphic to rotating the top and bottom layers in the other direction. :)

Does that imply that when they remove the cube (note that it is not permanently fixed to the machine), manually twist it (i.e. to shuffle to a random state, as in the video), and replace it, it has to be returned to a certain orientation?

Again, it still solved to the same final colors orientation even after it was removed, hand-shuffled, and replaced.

My apologies if I'm seeing something that isn't there.

Because the machine doesn't rotate the whole cube like a human would during solving.

The middle piece on each side of a Rubik's Cube doesn't move. The machine rotates each side via the drilled holes in each side's middle piece.

Human's don't typically rotate the cube either when they're speed solving. Rotating the whole cube causes you to slow down. We usually do yellow on top, white on the bottom and then you just think of the other four faces as opposing sets relative to each other (blue and green, orange and red).

If you're interested in learning how to solve, here's a link on how to use the Fridrich method. http://ukcubestore.com/fridrich-tutorial.html

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