The Meaning of Life
Written by Mike James   
Article Index
The Meaning of Life
The Gun And The Computer
Implementing Life
The CA Universe

By now you are probably getting the idea. Life isn't predictable!

In fact Life is so difficult to understand that even simple questions proved very difficult to answer.

For example, are there any patterns which grow without end? In 1969 Conway discovered an interesting little pattern of five cells which he called a glider.

 

glider

 

Five cells that walk across the Life universe

 

What made this interesting was that a glider walks its way across the Life universe and behaves like a basic particle that can be used to build other shapes.

 

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Indeed some physicists were so taken with the idea that they conducted experiments that involved firing gliders at targets and seeing what happened – just like particle physics using million dollar accelerators. In many ways it was the discovery of the glider that lead on to the rest of the developments in the study of life. 

The study of the different shapes that do particular things is very much like the classification that particle physicists used to try and make sense of the huge number of "elementary" particles that they encountered. The job of the particle physicists was easy by comparison with the life physicist because particles have comparatively simple behavior but a group of cells in life can change in many ways. 

Many simple groups were named early on - beehive, loaf and so on. Shapes that are periodic are easy to spot and there are named examples for many periods in the catalog but discovering new ones is an on going task.  At the moment for example there is no known pattern with a period of 19.  

There are lots of other challenges and if you want to know the current status visit the Game of Life Status page

 

The Glider Gun

However the real breakthrough came in 1970 when, in order to win a $50 prize that Conway had offered for proof that there was a configuration that would grow without bound, Bill Gosper discovered the glider gun. Conway believed that a pattern that grew indefinitely was impossible and that his $50 was safe.

 

gun

A glider gun – you can see two gliders moving off down and to the right

This complicated arrangement of cells fired a new glider every 30 generations. At last it was proved that there were patterns which grew without limit because the gun added five cells every 30 generations.

 

gospergun

 

More important, however, was the fact that with a glider gun you could now begin to build machines in Life space!

 

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Experimenting With Gliders

The invention of the Glider Gun opened up a whole new world. 

The streams of gliders could be used as if they were electric currents and thus logic gates and memory could be built.

Soon a complete Life computer was constructed proving that the simple rule, involving only local behavior of each cell, gave rise to a something as complicated as a digital computer. In other words, it was equivalent to a universal Turing machine that could compute anything that could be computed. 

Yes it is another amazing idea. You start off from a simple rule and you can build a pattern that acts as a universal Turing machine. This means that the rules of Life contain within them all of the computing power you could require. It means that Life is as complicated as any system that can be used to create a computer. 

Many people also take it to mean that what you can find in the Life universe isn't limited in anyway and certainly isn't any less complex than ours - so perhaps looking for life forms in Life isn't silly.

 

turing

A Universal Turing Machine (In Golly - see later)

After the glider gun, all sorts of interesting shapes were discovered – oscillators, movers, emitters and so,. 

The most important thing to notice is that even today Life is an experimental subject, very little if anything has been proved theoretically.



 
 

   
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