Thanks for the heads up, this had escaped me. Perhaps they proved their result only non-constructively, so we know it can be done in 20 moves, but we don't know how. Counting a slice turn as one move would be a little brazen.

By face rotations I didn't mean rotating or orienting the whole cube. I meant actual turns of cube faces against the rest of the cube. I am sorry if my choice of terms is misleading. English is not my native language.

Distance 16 to 20 are estimates. Their sum is known, but not the exact distribution.

I wouldn't say they're cheating, but I am a bit dissatisfied with their way of counting moves. Rotating a face by 180 degrees is not an elementary move to me. I'd like to know god's number in elementary moves.

There is no scientific way of deciding what is worth preserving and what isn't. That's why we have politics. To ridicule the cautious has always been a political strategy. Sometimes it was necessary for progress, sometimes it led to desaster. Those who think they know the outcome in advance are just as superstitious as the overly-cautious.

So x-rays must be completely harmless if I can't "detect" them? Think of airplane noise, as it is permanent near large airports. Would be ridiculous to claim it seeds tumors in human bodies. It just disturbs attentiveness, concentration, calmness, sleep. If you are a sensitive person, these disturbances may severely affect your quality of life. Noises can be heard, i.e., "detected", so there's no dispute as to the possible harm they can do. But how adequate are these criteria? Consciousness is not a system monitor. It is a bonus that some species were endowed with. The human body is not a robot. Our physiological systems were not designed. They're not just modules with interfaces. Their behaviour is not just determined by a set of formal rules and a specified input. They're not circuit boards. When our bodies and their functions gradually evolved in nature's history, they were not exposed to electromagnetic fields of the quality that is in question now. As long as life is not understood (and it isn't, unless we'll have succeeded in building living cells from scratch), it is not unreasonable to be cautious. The cancer claim is notorious because any lesser claim is not shocking enough to make it to the news. It is a suicide bomb of reputation: You get some attention at the expense of credibility.