Til stede på nettet fra november 1995: 17. årgang - 16. skoleår               Nordreisa videregående skole             Ingen gjestebok for øyeblikket

Generelle lenker:    Store norske leksikon        Engelsk Wikipedia        Ordbøker       Matematisk atlas      Rekke-leksikon     Vitensentre i Norge     Matematikerbiografier
  I
Telefon:   77 77 01 00
Telefaks:  77 76 53 73
E-post:

Privatpost:
Artikler
Grunnskolepensum
Hoderegning
Casio kalkulator
MathCad
Lenkesamling

Matematikere
Matematikkrommet

Matematisk tankegang
Spill
Talleksikon
Talltyper
VG1T - 2011/12
1: Matematikken rundt oss
TI-nspire       GeoGebra
Egenvurdering
2: Lineære funksjoner

TI-nspire       GeoGebra
Egenvurdering
3: Potenser/Logaritmer
TI-nspire       GeoGebra
Egenvurdering
4:Sannsynlighetsregning
TI-nspire       GeoGebra
Egenvurdering
5: Algebra
TI-nspire       GeoGebra
Egenvurdering
6: Trigonometri
TI-nspire       GeoGebra
Egenvurdering
7: Grafer og ulikheter
TI-nspire       GeoGebra
Egenvurdering
8: Derivasjon
TI-nspire       GeoGebra
Egenvurdering
Repetisjon
Brøkregning
Negative tall

Vekstfaktor
VG1P - 2008/09
1: Matematikken rundt oss
2: Grafiske framstillinger
3: Geometri
4: I yrke/kunst/arkitektur
5: Økonomi
6: Sannsynlighetsregning
7: Funksjoner
 VG2-R1 - 2010/11
1:Kombinatorikk/sannsynl.
    Teori           Elektronisk
2:Bevis og bevisføring
    Teori           Elektronisk
3:Vektorer
    Teori           Elektronisk
4:Algebra
    Teori           Elektronisk
5:Grenseverdi/derivasjon
    Teori           Elektronisk
6:Funksjonsdrøfting
    Teori           Elektronisk
7:Geometri
    Teori           Elektronisk

VG3-R2 - 2011/12

Læreboka:
Start
Kapittel 1
Test 1 - løsning
Fasit, innhold, læreplan
1: Trigonometri

    Teori           Elektronisk
2: Vektorer i rommet

    Teori           Elektronisk
3: Trigonometriske funk.

    Teori           Elektronisk
4: Integrasjon

    Teori           Elektronisk
5: Diff.-likninger 1. orden

    Teori           Elektronisk
6: Følger og rekker

    Teori           Elektronisk
 
VG3 R2 - 2010/11
7: Diff.-likninger 2. orden

    Teori           Elektronisk

2MX - 2006/07

1: Likninger, ulikheter
2: Eksponentialfunksjoner
3: Trigonometri
4: Derivasjon
5: Sannsynlighetsregning
6: Vektorer
7: Integrasjon

3MX - 2007/08

1: Rekker
Niels Henrik Abel
2: Trigonometri
3: Vektorer i rommet
4: Integralregning
Sophus Lie
5: Sannsynlighetsregning
6: Periodiske funksjoner
7: Vektorfunksjoner

Diverse artikler

Abelkonkurransen
Arkitektmatematikk
Bruer og tangens
Buer og egg

Formlikhet
Gamle enheter
Grunnstofftabellen
Inflasjon
Kalender
Likninger
Mangekanter
Nipunktsirkelen
PC - mangekanter
π på jordkloden
Perpetuum mobile
Personnummer
Pytagoras
Rubiks kube
SI - målesystemet

Tallkåserier 3MX
Teknologihistorie
Teodolitt
Triangulering
Jakten på den hellige gral
Dialekter
Privat

Du er besøkende nr.
Hit Counter

(Teller nullstilt 23. august 2007)

Sist endra: mandag, 20. august 2007 14:55:39  -  Hans Isdahl

Rubiks kube - historikk og løsning

Er det noen som husker denne?

Ideen med å presentere kuben på disse matematikksidene henger sammen med tankegangen bak løsning av kuben: Både metodikk i tankegangen, løsning av puslerier samt antall kombinasjoner er viktige momenter i matematisk tankegang. Derfor lenkes denne sida fra generelle matematikksider samt fra sannsynlighetsregninga - dvs. kombinatorikken.

wpeE.jpg (15810 bytes)

Antall plasseringer av de 27 - egentlig 26 - småkubene er interessant matematikk:

bullet

Den midterste kuben, nr. 27, fins ikke. Vi har 26 småkuber å forholde oss til.

bullet

De midterste på hver side, 6 stykker på de 6 sideflatene, er umulig å flytte i forhold til hverandre. De er konstruert som et tredimensjonalt kors, kryss.

bullet

De 8 hjørnebitene som vi ser 3 sider av, kan hver plasseres på 8 ulike plasser i 3 ulike posisjoner. Hvor mange muligheter? (Kanskje vi må redusere med 3 posisjoner: Plasserer vi dem fritt, kan kanskje ikke kuben løses...)

bullet

Og de 12 midtpåsideterningene kan plasseres på 12 ulike steder, hver av dem i 2 ulike posisjoner. (Her må vi helt sikkert redusere: Den siste - for eksempel - kan ikke plasseres fritt, men må stå i én av de to posisjonene.)

Hvor mange mulige kombinasjoner blir dette?

 

Historikk        Løsning        Hvor fort kan det gjøres?

Løsning på kuben - eller i det minste utfordrende knep for å løse den.
  1. Løs øverste lag.
  2. Løs midterste lag, dvs. få de 4 kantene på plass.
  3. Få de 4 nederste hjørnene på plass.
  4. Snu de 4 nederste hjørnene så de ligger riktig.
  5. Få de 4 nederste kantene på plass.
  6. Snu de 4 nederste kantene så de ligger riktig.

Hvor fort kan det gjøres? Les i Guinness' rekordbok, eller se på denne karen! Det ser ut til at det bare går 18,5 sekunder... (Verdensrekorden i hurtigløsning i Guinness' rekordbok var 22,95 sekunder. Den terningen må være innsatt med såpe for å gli godt!)

Løs øverste lag:

Fordi dette er en del av matematikkundervisninga, gir jeg ingen hjelp her! Vær oppmerksom på at 6 brikker alltid ligger fast i kuben, de 6 som vi bare kan se ei side på og som ligger midt på hver sin side. Lag f.eks. øverste side BLÅ!

Symbolbruk - Du ser alltid på ei side med 3 x 3 ruter, 3 rader og 3 kolonner; dreininger er bare nitti grader pr. symbol!

bullet

Venstre kolonne opp  eller ned

bullet

Midtre kolonne opp eller ned

bullet

Høyre kolonne opp eller ned

bullet

Øvre rad mot høyre eller mot venstre

bullet

Midtre rad mot høyre eller mot venstre

bullet

Nedre rad mot høyre eller mot venstre

bullet

Fremre lag dreid nitti grader mot høyre/med klokka

bullet

Fremre lag dreid nitti grader mot venstre/mot klokka

Løs midterste lag, dvs. få de 4 kantene på plass:

Slik skal kuben se ut når du har løst midterste lag - dersom du begynte med blått øverst:

Og slik ser den ut når du skal begynne på midterste lag:

Dette er metoden for å få kanten opp fra bunnen og til kanten til høyre:

 

Prøv speilvendt variant for å få til denne flyttinga!

Hvis den kanten du skal ha opp ligger rett plassert, men vridd, må du få en annen kant opp først, slik at din kommer ned.

Få de 4 nederste hjørnene på plass:

Nå snur du kuben slik at den gjenstående sida ligger på toppen:

Konsekvens:
bulletForrest til venstre urørt
bulletBakerst venstre vris mot klokka
bulletForrest høyre bakover mot klokka
bulletBakerst høyre framover mot klokka

 

Konsekvens:
bulletBakerst til venstre urørt
bulletBakerst høyre vris mot klokka
bulletForrest venstre til høyre mot klokka
bulletForrest høyre til venstre mot klokka

Snu de 4 nederste hjørnene så de ligger riktig.

Figurene til høyre antyder at samme hva slags problem av de 7 du må stå igjen med, er metoden den samme, men må kanskje brukes to eller tre ganger:

Konsekvens:

bulletForrest høyre urørt
bulletBakerst venstre vris mot klokka
bulletBakerst høyre mot klokka
bulletForrest venstre mot klokka

 



Få de 4 nederste kantene på plass.

Dette må kanskje gjøres flere ganger...

Konsevens:

bulletForrest midt urørt
bulletVenstre midt til høyre og vippes
bulletHøyre midt til bakerst og vippes
bulletBakerst midt til venstre og vippes

 

Snu de 4 nederste kantene så de ligger riktig.

Enten står du igjen med "fiskemønsteret" der midtene foran og til høyre må vippes:


Eller du står igjen med "H-mønsteret" der midtene foran og bak må vippes.

Hvis alle fire må vippes, bruker du en av disse to metodene to ganger.


Oversettelsen og enkle omskrivinger har jeg gjort, forfatteren er: dennyd@gte.net

Men det går jo an å bygge seg en kubeløser i lego:

PREAMBLE

This robot solves the 3x3x3 Rubik's Cube®.

I started to think about this problem in about August of 2000. In Jan 2001 fellow Mindstorms forums user 'agiecco' announced his intention to work on a robotic solution and, simultaneously, I saw that Rubik's Cubes were on sale at www.target.com. So I bought a couple of cubes and started getting down to business...

I produced a 'late beta' version in mid-April 2001 that was a little clunky. The final version (presented here) is smooth and fairly reliable.

MECHANICS

To achieve a cube solution, you must be able to rotate the whole cube by 90° in two orthogonal axes, and be able to turn a face by 90° relative to the rest of the cube.

I opted to use the left and right grabbers to turn the faces; the yellow grabber can rotate the left face by an 90°; the green grabber can rotate the right face by 90°; or they can both turn simultaneously while the bottom grab is open to rotate the whole cube through 90°.

The bottom gabber holds the center 'slice' of the cube when the left or right grabber is turning a single face, and also provides a 90° turn for rotating the whole cube.

The tricky part is to re-orient the cube between moves to present the next face to be turned by the left or right grabber.


Lubricating cube PROBLEMS SOLVED

1. The cube faces are generally too stiff for LEGO elements to turn

This problem was solved by a tip I found on Lars Petrus's Speed Cubing page: lubricate the cube with silicone spray lubricant. I got an aerosol can of LubriMatic Heavy Duty Silicone Lubricant from my local ACE hardware store and squirted some inside the cube. After wiping off the excess spray you must rotate the cube faces for about 30 minutes to prevent the solvent in the spray dissolving the cube body and sticking it solid. Once you have done this, the result is a fairly slick cube.

Wedging the cube open

However, I found that some of the faces still got stuck because the springs inside the cube were too stiff, so I pushed some wedges (actually, plastic knives) in between the cube slices and left them over night to force the springs inside the cube to loosen up. After this treatment the cubes handled very well.


2. Getting enough torque

Even with a treated cube, getting enough torque to turn the cube faces was going to be a problem. I remembered the system that Jin Sato used on the thigh joints of MIBO -- worm gear to the outer 56t ring of the large Technic turntable. This gives torque to spare for turning the faces of a treated cube.

3. LEGO grabbers don't grip strongly enough

My early attempts at building a cube solver were all stymied by grips that slipped. The worm-56t gave enough torque to turn, but the fingers couldn't hang on and the grip was simply pried apart as the grabber rotated around the stationary cube face. I thought about changing the device's name to ButterFingers.

I rebuilt the left and right grabbers six times (and the bottom grabber four times) trying elastic bands, Technic shocks, and pneumatics, before I came up with an adequate grip mechanism. In the present version, an axle runs from a motor through the center of the large Technic turntable to a worm screw. The worm screw turns two 24t gears mounted either side of the worm inside the body of the grabber. Each end of the 24t axles terminates with an 8t gear outside the body of the grabber, and these 8ts engage with 24t-s on either end of the axles which carry the grabber's fingers. This system can be strained quite tight without risk of gear slippage, and also allows the large turntables to rotate 180° without any significant loss of grip.

For the bottom grabber I had to use a slightly different arrangement (same gear combinations) because the fingers of the green and yellow grabs kept catching on the external 24ts of the bottom grab. Eventually I managed to work out how to mount all the gears internally in the 4-stud width of large Technic turntable.

Side grab gear train (typical for 2)
Bottom grab gear train


4. Precision of movement

Having solved these problems, there was still the problem of 'slop' or 'gear lash' in the left and right drive trains.

Most of this was absorbed in the beta version by putting rotation sensors on the worm drive axles that rotate the grabs. However, the worm screws are a *tiny* bit too short to fit snugly -- they travel a little when the motor direction is reversed. To cure this I tried a suggestion from John Barnes and cut thin shims out of the plastic insert tray from inside a LEGO box. Two shims on each drive axle fixed the worm gear nicely in position so that the gear lash (although still detectable) was *nearly* within the tolerance of the cube for repeated turning.

However, the rotation sensors for the LEFT and RIGHT grabbers occasionally lost track of their position and had to be manually tweaked during a solution. There was also the problem that the rotation sensors were on the same axle as the worm screw turning the turntable. This meant that when the cube was a little stiff, even if the worm screw had performed the correct number of rotations to turn the cube face 90°, the LEGO pieces of the grabber had enough flex that the grabber was slightly twisted and the face did not make it all the way around to the 90° point.

Therefore, I abandoned rotation sensors and put two touch sensors at the limits of the quarter turn of the turntable (similar to the bottom grabber). I built a 'toucher' attached to the rotating part of the large turntable, and this seemed to compensate better for the twisting of the other LEGO elements of the grabber during stiff turns.

The disadvantage of the touch sensor approach, of course, is that the grabbers can no longer make a full 180° turn, so there is more time taken repositioning the side grabbers. The robot averages one face rotation every 30 seconds (i.e., a 20 rotation solution takes about 10 minutes). The final problem is making sure that the faces of the cube are kept in orthogonal alignment. A standard Rubik's Cube has side dimensions *just* larger than 7 LEGO studs. Fortunately there is enough flex in the joints of LEGO Technic to absorb the tiny additional dimension. Each grabber arm is fitted with reverse slopes that force the cube into the correct orthogonal alignment as the grabbers close.


CubeScan software screenshot 5. Establishing the initial (unsolved) state of the cube

The longest part of the this project involved writing the color-recognition software. I downloaded the Logitech Quick Cam SDK from the Logitech Developer's site (the LEGO Vision Cam is a repackaged Logitech Quick Cam) and used VB5 to write a fairly decent program (click the Code link for source). The color recognition is fairly robust (about one error every two cubes when well-calibrated), but not perfect, so I incorporated a feature that requires you to confirm that each face has been correctly scanned (and, optionally, allows you to correct the input manually) before it scans the next face.


The software requires calibration with a solved cube under the particular lighting conditions, and it is quite finicky about changes in lighting conditions. I also left in the earlier manual input option so that you can get a solved cube for calibration, or in case anyone who doesn't have a Vision Cam wants to try this.

Briefly, the software sends a message to the top RCX asking it to present one face of the cube to the video camera. The computer captures a frame from the video camera, and scans a 50x50 pixel area of each color patch to find the median red, green and blue (RGB) color values for each color patch on the face. The RGB values are converted to CIE X Y y coordinates, and then the CIE values are trigonometrically compared to the calibration values to find the closest match. The computer then asks the robot to show it the next face, and the process is repeated until all the faces have been scanned.

CubeSolver, lighting
6. General solution to the Rubik's cube

There are any many general solutions to the 3^3 Rubik's Cube on the internet (see here for a partial list). However, most of these produce a sequence of moves involving 50 or 60 face rotations. Given that CubeSolver moves quite slowly (averages about 30 seconds between face rotations), I wanted a relatively short sequence of moves. Fortunately, I found some C source code by Mike Reid on the internet which implements Herbert Kociemba's solution method: it provides short solutions (< 40 face rotations). I ported this code to Microsoft Visual C++ and recompiled it as an OCX for use in Visual Basic. I must say that Mike did a very decent job with his code -- move sequences are generated quickly, with a length usually about 20 moves or less.

Den offisielle Rubik-sida, http://www.rubiks.com/, inneholder denne historikken:

BRIEF HISTORY OF THE CUBE
Every invention has an official birth date. For the Cube this date is 1974 when the first working prototype came into being and a patent application was drafted. The place was Budapest, the capital of Hungary. The inventor's name is now a household word. At the time, Erno Rubik was a lecturer in the Department of Interior Design at the Academy of Applied Arts and Crafts in Budapest.

Although 1974 marks the inauguration of the Cube, the processes that led to the invention began a few years earlier, nor was the identity of the inventor a fortuitous accident. Erno Rubik had a passionate interest in geometry, in the study of 3D forms, in construction and in exploring the hidden possibilities of combinations of forms and material in theory and in practice.

In the course of his teaching, Erno Rubik preferred to communicate his ideas by the use of actual models, made from paper, cardboard, wood or plastic, challenging his students to experiment by manipulating clearly constructed and easily interpreted forms. It was the realization that even the simplest elements, cleverly duplicated and manipulated, yield an abundance of multiple forms that was the first step on the long road that led finally to the Cube.

Although possibly the most original of all invented puzzles, the Cube was not created in a vacuum. Its classical antecedents are great puzzles in their own right. The Tangram, originating from ancient China, merely consists of 5 triangles, a square and a parallelogram, simple elements that yield a multitude of interesting figures. The Pentomino, invented by Solomon W Golomb, has 12 different elements, each one made up of five squares joined together, displaying all the possible configurations of the five combined squares. Pentomino poses the fascinating geometric problem of constructing various rectangles. Piet Hein's Soma Cube is, in a sense, a three dimensional version of Pentominos. It resembles Rubik's Cube both in shape and in the large number of ways its seven elements can be assembled into a 3x3x3 cube. Finally, there is Sam Loyd's well known 15 puzzle, with it's numbered tiles locked together yet moving separately, so that by pushing them about they can be set in sequential order and scrambled at will. Viewing these puzzles places Rubik's Cube in a context and highlights just what a breakthrough creation the Cube really is.

What Erno Rubik's set out to do was create a three dimensional object, of high aesthetic value, which was not only richer in configuration variations and more of a mental challenge than any puzzle in existence, but would also continue to be ONE, SELF-CONTAINED WHOLE, throughout its manifold transformations.

This objective seemed at first as impossible to achieve as the 3-axial rotation of the Cube appears on first encounter. After conceiving the idea of the 3x3x3 Cube, Erno Rubik first tried to hold together the elements of a simpler, 2x2x2 cube, by means of an elastic rubber construction that threaded its way through all 8 elements. Even at this simple level it soon became clear that such a device could not work. The alternatives then available, such as magnets and the obvious tongue and grooves system, could not cope with the complexity of the different junctions and movements that each element required. Erno Rubik realized that only a totally original concept could provide a satisfactory solution.

The inspiration came on a lazy, summer day as he was watching the Danube flow by. Rubik's eye was attracted by some pebbles, whose sharp edges have been rubbed and smoothed away in the course of time bringing into being rounded shapes of great but simple beauty. The interior of the Cube elements had to have the same rounded architecture. The brilliant interior mechanism, which is basically cylindrical, took some time to reach its final form. For ease of manipulation, the balance between tightness and looseness had to be just right, tolerances had to be exact. Finally, the 54 outer surfaces of the individual elements were given their colors. Lots of different decorative patterns, with numbers and symbols as well as diverse color combinations were tried, but none of them worked nearly as well as the six simple but distinct colors, each one unifying and differentiating one single face of the Cube.

When the Cube was complete, Erno Rubik demonstrated it to his students and let some of his friends play with it. The effect was instantaneous. Once somebody laid his hands on the Cube it was difficult to get it back!

The compulsive interest of friends and students in the Cube caught its creator completely by surprise and it was months before any thought was given to the possibility of producing it on an industrial scale.

Eventually a manufacturer took on the job of tooling up for mass production and making the puzzle available to the public at large. Given the inner complexity of the Cube, and the then prevailing economic conditions in communist Hungary, this was by no means an easy undertaking. It is to the credit of the two men at the helm of the toy production firm of Politechnika, President Lehel Takacz and Chief Engineer Ferencz Manczur that they at once perceived enough merit in the Cube to accept this task. The process of turning the hand made object into thousands of low cost, mass manufactured units was slow. It took the best part of three years, but at last, towards the end of 1977 the first Cubes appeared on the shelves of the Budapest toyshops.

During 1978, without any promotion or publicity, the Cube began very slowly to make its way through the hands of fascinated youths into homes, playgrounds and schools. Word of mouth spread the news and by the beginning of 1979 there were enthusiastic circles of Cube devotees in various parts of Hungary.

With the country being both physically and culturally behind the iron curtain at the time, the growing popularity of the Cube did not cross over to the West for quite some time. Not surprisingly, two men of Hungarian origin who had established their lives in the West built the bridge, which eventually enabled the Cube to cross the divide.

Dr Tibor Laczi, born in Budapest, educated in Vienna and employed by a major German computer manufacturer "discovered" the Cube on one of his frequent business trips to Hungary. He fell in love with it, and sensing its potential consumer appeal, brought it to the Nuremberg Toy Fair in February 1979 in the hope of finding a potential German toy distributor. He did not meet with a great deal of success but he did stumble across an individual who at that point of the Cube's history was destined to make a crucial difference.

Tom Kremer, a successful toy and game inventor himself, whose mother language was also Hungarian, ran at the time his own marketing and licensing company. Seven Towns Ltd., based in London, was widely respected throughout the international toy industry as a product developer working not only with its own ideas but also representing professional inventors from all over the world.

The two men made a pact, there and then, to translate the Hungarian success of the Cube onto the world stage. Dr Ladzi headed back to Hungary to pave the way with the prevailing Hungarian bureaucracy whilst Tom Kremer set off on a world tour of toy manufacturers. He was convinced that to realize the Cube's full commercial potential it had to have the marketing muscle, the promotional power and distribution network of a major international company. Unfortunately he found none of the leading players in the field shared his enthusiasm. Although impressed by the Cube, the general view within the industry estimated its prospects to be poor. Its "faults" were numerous: Too difficult and expensive to manufacture, impossible to demonstrate its fascination on TV, too abstract, too cerebral, too quiet, a challenge for the esoteric academic mind rather than a puzzle meant for the young and the general public.

Undeterred by this universal rejection, and spurred on by his firm belief in the exceptional quality of the toy, Tom Kremer, now armed with a convincing marketing plan, continued his search for a viable partner. After many disappointments, he succeeded in persuading Stewart Sims, Vice President of Marketing of the Ideal Toy Corporation, to come to Hungary, to see with his own eyes the Cube in play. It was now September 1979, by which time the Cube had gained a sufficient degree of popularity to be seen occasionally in the street, on trams, in cafes, each time in the hands of someone turning and twisting it, completely absorbed. After five days of convoluted negotiations between a skeptical American capitalist and an obstinate communist organization largely ignorant of the operation of a free market, with Laczi and Kremer desperately holding the two sides together, an order for one million cubes was signed amidst much handshaking and great relief all round.

In the meanwhile, quite independently of these developments, David Singmaster, an English mathematician, became deeply interested in the theoretical problems and ramifications raised by the Cube in his own field. He wrote a newspaper article in June 1979, the first one to appear outside Hungary, which brought the Cube to the attention of academic circles world wide and led indirectly to another milestone in its history: an article in Scientific American, with a cover picture, by Douglas Hotstadter an acknowledged authority in the field of Recreational Mathematics.

Apart from a small seepage across the Hungarian borders, the Cube made its international debut at the Toy Fairs of London, Paris, Nuremberg and New York in January/February, 1980. With Erno Rubik demonstrating his own creation, the Cube made an immediate impact. The trade buyers were impressed, orders rolled in. There was just one problem: there were no Cubes! Western quality standards and packaging norms meant drastic changes in the Hungarian manufacturing process. This, as with any change under a communist in regime, was slow in coming. Communication between New York and Budapest, given the linguistic and cultural differences, despite the frequent interventions of Tom Kremer, were not easy.

The flow of products from Hungary began in May 1980. As soon as the Cube found its way into the hands of consumers it became evident that the initial order of one million pieces for the first year would not be anywhere near sufficient to meet the growing demand. From the very beginning it was a characteristic of the Cube that no matter how fast production increased, demand grew faster. Contrary to what the leaders of the Toy Industry had expected, for the next two and a half years the problem was not one of selling Cubes but of supplying them. From 1 million the figures started to grow quickly to 2, to 3, to 5 million and then, in 1981 exploded exponentially. Production centers had to expand from Hungary to Hong Kong, Taiwan, Costa Rica and Brazil, taking up the capacities of many separate factories in each center.

The challenge of trying to master the Cube, to be able to restore all of its six sides to the original colors seemed to have a mesmeric effect on an amazing variety of individuals right across age, occupation, wealth and social standing. Grandmothers, bank managers, baseball players, pilots, librarians, park attendants could be seen working away at their Cubes at any hour of the day. In restaurants the Cube would feature on tables side by side with salt and pepper pots, handled with greater frequency than either. But it was the young, schoolboys and students, who were in the vanguard of what was fast becoming a massive movement that swept across the world. They were the ones who proved most adept at solving the puzzle; they were the ones to form special cubists clubs, to organize competitions, to suffer from Rubik's wrist playing continuously for hours and days with an object that simply could not be put down.

The difficulty of solving the Cube and the absolute compulsion to solve it generated over 60 books offering desperately needed help. They in turn generated more addicts, displaying with evident pride their newly acquired prowess.

After winning the highest prize for outstanding inventions in Hungary, in 1980 the Cube won top toy awards in Germany, France, Britain and the U.S. by 1981 it entered the New York Museum of Modern Art as an exhibit. The Cube achieved such a universal presence and penetrated so deeply the fabric of our society that "Rubik's Cube", by 1982 a household term, became part of the Oxford English Dictionary.

It is difficult to estimate the total number of Cubes sold throughout the world. In the period of 1980-1982, partly because demand far outstripped supply, a huge variety of pirate, unauthorized products of inferior quality came onto the market from opportunistic Taiwanese, Korean and Hong Kong vendors. Although the Ideal Toy Corporation won a number of court cases in Holland, Britain, the U.S. and other countries, it was impossible to stem the tide. It is safe to assume that the figure exceeds 100 million, it is certain that it was significantly greater than that.

Interestingly, the legal defense of the Cube was never based on the original patent, this only applied in Hungary. It was the "Rubik" trademark, Erno Rubik's copyright on the object itself and the "passing off" laws, which secured, and continues to secure adequate protection of the Cube against unauthorized copies in all countries throughout the world.

In effect, as the Cube was initially created as a one-off object, with an inherent artistic merit, the Rubik copyright applies not only to the 3D object itself but also to any graphic representation of it in print or on screen, until 70 years after the creator's death.

Given the extraordinary volumes of sales, both legitimate and illegitimate, it was inevitable that eventually a saturation point would be reached. The market in Cubes collapsed, shops and factories remaindered their stocks and for some time from 1983 onwards the Cube became unavailable. The Ideal Toy Corp. was bought by CBS and CBS itself got out of toys in 1985.

The toy business being largely fashion oriented, the industry gave up on the Cube, considering it a fad, albeit an unprecedented one. Not so Tom Kremer. He had always considered the Cube to be one of the all time great classic toys, worthy to be placed alongside such permanent fixtures as Monopoly, Scrabble and Mr. Potato Head. So in 1985 his company, Seven Towns, acquired all the rights to the "Rubik's Cube". Biding their time, they re-introduced the Cube, without any hype, very gradually in selected key markets, beginning in 1991. Compared to the giant waves of the early eighties, sales were just a trickle in the first few years. However, in 1995, Oddzon a dynamic Californian based company took over the distribution of the Cube with dramatic results. In 1996 in the US alone over 300,000 Cubes were sold with the numbers growing in 1997 and 1998. In Japan, where Tsukuda is still the faithful original Rubik's Cube distributor, sales have exceeded 100,000 in 1997 and in Britain sales are also pushing the 100,000 mark. The pattern is the same world over. The Cube is staging a come back.

But now, in its second incarnation, the Cube is part of a family of puzzles and games which bear the stamp of the genius who created the greatest three dimensional puzzle the world has ever known.

Erno Rubik has not changed much over the years. Working closely with Seven Towns, he is still deeply engaged in creating new games and puzzles, and remains one of the principal beneficiaries of what proved to be a spectacularly successful invention.