h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Hey there!

I made you (unwillingly) participate to something of a sociology experiment, see http://smallworld.sociology.columbia.edu/. I hope you don't mind ?

Well I saw the email and it does look fascinating; I would like to take part. Not sure I am 100% on the details: my mission, should I accept it, is to contact someone I know however slightly, that may be a step closer to my target person. Am I on the right track?

If so am I a link in a chain or the start of a new one?

The "six steps of connection" seems like the assertion that the Rubik cube can't be more than 12 twists away from solution -- because 12 (or whatever number it is) will generate enough diversity to create all possible patterns. Has that been proved?

As far as I know, you are on the right track. I believe you're a link in a chain I just started. I've started a few others last summer, but they never got further than myself .

As for Rubik's cube (which is a nice comparison), there is an explicit algorithm involving 29 moves, and it has been proved that there exists a 'best algorithm' (funnily enough called 'God's algorithm') involving something between 25 and 29 steps if I remember well. Check http://web.usna.navy.mil/~wdj/rubik_nts.htm or other links at http://trucsmaths.free.fr/rubik.htm#Sites.

Thanks for that Toy Box!

My birthday present to myself arrived early today -- a 4x4x4 and a 5x5x5 Rubik cube! Whoooarr!

Happy birthday Recumbentman !

Have you checked the 4-dimensional Rubik's cube as well ?

I developed a method for solving the 4x4x4 rubik's cube many years ago and I forgot it many years ago too. I've never seen the 5x5x5. Perhaps you could lend me your one when you've solved it. I recently saw a (Rubik's?) dodecahedron which looked interesting.

Have to confess: I haven't dare unwrap the 5x5x5 yet!

I came close to solving the 4x4x4 (that is adapting the solution from the book about the 3x3x3) but then the dog chewed one centre piece, which is why I bought another (anyone got a spare centre piece from a 4x4x4? Will pay postage and send a thankyou gift). (Yellow for preference.)

In the heady days of 1981 I read the Scientific American article on the 3^3 and decided to solve it for myself over a fortnight's holiday in Tenerife. Which I did, just; a cumbersome and incomplete algorithm. They said in the article that it should take a fortnight, but they didn't say that involved near-divorce and waking up in the middle of the night remembering what it was you had forgotten two days ago. A very pleasant thing to have done, hellish at the time.

As far as I remember, in 1978 it took me fourteen days to restore my first Rubik cube to its original state, and another three to perfect a general solution. I don't think it took anything like as long to figure out the 4x4x4 because I already knew how to think about it.

Were they there in 1978? I think I got mine in 81. My son who was 11 at the time learnt the book algorithm from me, and instantly halved my best time.