Rubik’s 5x5x5 (Professor) and TouchCube

I’m old enough to have been around during the first release of the Rubik’s Cube, back in the 1970s. I was something of an aficionado at the time, owning a Rubik’s Cube, the 4x4x4 Rubik’s Revenge, and a drawerful of other Rubik inventions and inspirations. Eventually, I moved on to other interests, and the drawer got busy collecting dust.

I recently picked up two additional entries in the Rubik’s universe, the TouchCube and the 5x5x5 Rubik’s Professor.

The TouchCube’s price has dropped considerably from its release last year; its MSRP is $150, but it can be gotten fairly easily (as I did) for a third of that. That’s not surprising to me, because while it’s a pretty little gizmo, it doesn’t add much to the traditional solving experience, and it can be very frustrating.

It contains an accelerometer, so that moves can allegedly only be made on the top side, but its touch sensitivity can be erratic, causing both unintended moves and unregistered intended moves. Indeed, for me, the added challenge of the TouchCube was how long it would take me to solve it, even though I’m reasonably good at solving a traditional cube. Several times, I’d come close only to have the touch sensitivity and the limitation of moves to the top side only conspire to confuse me and cause me to lose my place.

Overall, the TouchCube is far more useful as an objet d’art than as a functional puzzle. The good news at our house is that our one-year-old son is entranced by it, meaning it can act as a decent distraction device.

The Professor is more interesting. Like the Revenge, solving the Professor consists of two major steps: Aligning the cubes so that you have an unsolved 3x3x3 Rubik’s Cube, and then solving the Cube.

The Revenge has a so-called parity issue: Once you solve it to a Cube state, it’s possible that one pair of edge cubes is reversed. This can’t be easily detected until the Cube has been solved. I seem to recall there’s some sort of method for reversing the pair, but I prefer to minimize the number of things I actually have to memorize, so when I ran into the parity issue I’d just scramble the Revenge and start again.

The Professor also has a parity issue, but it’s much easier to detect. Once you have the Professor solved to an embedded scrambled Cube, it can be solved using standard Cube strategy, every time. For this reason, I’m left with the impression that the Professor is actually easier than the Revenge to solve, but that may also have something to do with the decades that have elapsed since I last tried a Revenge.

There are various tutorials online on how to solve the Professor and the Cube. These are my strategies, meant as I said to minimize what I have to actually memorize. I’m not trying to solve as quickly as possible; rather, my goal is relaxation and fun.

The first major step to solving the Professor is to move the cubes around to create a scrambled Cube. At the end of this step, the 9 squares at the center of each side will be a single color, and the 3 non-corner edge pieces on each of the 12 edges will be matched. (There are apparently accepted names for each of these individual cubes, but I’m not one for jargon. Minimal memory and all that.)

To accomplish this first major step, first complete these minor steps, in order:

  1. Pick a color and solve the 3×3 center. This is the easiest step.
  2. Solve the opposite 3×3 center.
  3. Pick one of the remaining four colors and, without disturbing the first two colors, solve its 3×3 center.
  4. Pick one of the remaining three colors and solve.
  5. The preceding steps are fairly easy, albeit increasingly difficult. Finally, solve the 3×3 centers for the remaining two sides. This can be a bit more difficult and frustrating, but through trial and error and practice, you’ll get there.

At this point, you’ll have solid 3×3 centers on all six sides, but the edge pieces will be mixed up. Look for trios and put them together, always being careful to return the 3×3 centers after each trio is grouped. Keep in mind that you don’t have to put the trios in the correct place at this point, just that you want to group all the edge trios together.

What I do is pick opposing sides (orange and red, for instance) and use these to hold the grouped trios. There are twelve trios to group, and this allows me to hold eight of them, leaving the four in the center still messed up.

The Professor can then be solved to the scrambled Cube state using a single memorized algorithm and a bit of patience. Looking down on the cube:

  1. Rotate the two levels closest to your body one rotation to the right (clockwise on the axis).
  2. Rotate the one level closest to your right one rotation toward your body (counterclockwise on the axis).
  3. Rotate the one level closest to your body one rotation to the right (clockwise on the axis).
  4. Rotate the one level closest to your right one rotation away from your body (clockwise on the axis).
  5. Rotate the two levels closest to your body one rotation to the left (counterclockwise on the axis).

This algorithm affects only three trios, leaving the other nine intact. The trios affected are the ones to the left and right of the top level and the one on the left side of the cube closest to your body.

It is possible to solve two of the four remaining trios and have the other two unsolved. This is the parity problem of the Professor, and there’s a shortcut for solving it, but in my own experience (and despite what the tutorials I’ve seen have said), I’ve found that it’s possible to resolve the parity through a little bit of forethought, without having to use the shortcut. By all means, though, memorize the shortcut if you prefer.

Once you’ve grouped all twelve trios, you have a Rubik’s Cube with a fat middle level. It can now be solved according to whatever technique you prefer. (I may post my own technique at a later date, for whatever it’s worth.)

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