The glider is a pattern that travels across the board in

Conway's Game of Life The Game of Life, also known simply as Life, is a cellular automaton devised by the British mathematician John Horton Conway in 1970. It is a zero-player game, meaning that its evolution is determined by its initial state, requiring no furthe ...

. It was first discovered by Richard K. Guy in 1969, while John Conway's group was attempting to track the evolution of the R-

pentomino Derived from the Greek word for ' 5', and " domino", a pentomino (or 5-omino) is a polyomino of order 5, that is, a polygon in the plane made of 5 equal-sized squares connected edge-to-edge. When rotations and reflections are not considered ...

. Gliders are the smallest spaceships, and they travel diagonally at a speed of one cell every four generations, or

c/4

. The glider is often produced from randomly generated starting configurations. The name comes from the fact that, after two steps, the glider pattern repeats its configuration with a

glide reflection In 2-dimensional geometry, a glide reflection (or transflection) is a symmetry operation that consists of a reflection over a line and then translation along that line, combined into a single operation. The intermediate step between reflecti ...

symmetry. After four steps and two glide reflections, it returns to its original orientation. John Conway remarked that he wished he hadn't called it the glider. The game was developed before the widespread use of interactive computers, and after seeing it animated, he feels the glider looks more like an ant walking across the plane.

Importance

Gliders are important to the Game of Life because they are easily produced, can be collided with each other to form more complicated objects, and can be used to transmit information over long distances. Instances of this second advantage are called glider syntheses. For instance, eight gliders can be positioned so that they collide to form a Gosper glider gun. Glider collisions designed to result in certain patterns are also called glider syntheses. Patterns such as blocks, beehives, blinkers, traffic lights, even the uncommon Eater, can be synthesized with just two gliders. It takes three gliders to build the three other basic spaceships, and even the pentadecathlon

oscillator Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...

. Some patterns require a very large number (sometimes hundreds) of glider collisions; some oscillators, exotic spaceships, puffer trains, guns, etc. Whether the construction of an exotic pattern from gliders can possibly mean it can occur naturally, is still conjecture. Gliders can also be collided with other patterns with interesting results. For example, if two gliders are shot at a block in just the right way, the block moves closer to the source of the gliders. If three gliders are shot in just the right way, the block moves farther away. This "sliding block memory" can be used to simulate a counter, which would be modified by firing gliders at it. It is possible to construct

logic gate A logic gate is an idealized or physical device implementing a Boolean function, a logical operation performed on one or more binary inputs that produces a single binary output. Depending on the context, the term may refer to an ideal logic ga ...

s such as ''

AND or AND may refer to: Logic, grammar, and computing * Conjunction (grammar), connecting two words, phrases, or clauses * Logical conjunction in mathematical logic, notated as "∧", "⋅", "&", or simple juxtaposition * Bitwise AND, a boolea ...

'', '' OR'' and '' NOT'' using gliders. One may also build a pattern that acts like a

finite state machine A finite-state machine (FSM) or finite-state automaton (FSA, plural: ''automata''), finite automaton, or simply a state machine, is a mathematical model of computation. It is an abstract machine that can be in exactly one of a finite number o ...

connected to two counters. This has the same computational power as a

universal Turing machine In computer science, a universal Turing machine (UTM) is a Turing machine that can simulate an arbitrary Turing machine on arbitrary input. The universal machine essentially achieves this by reading both the description of the machine to be simu ...

, so, using the glider, the Game of Life is theoretically as powerful as any computer with unlimited memory and no time constraints: it is

Turing complete Alan Mathison Turing (; 23 June 1912 – 7 June 1954) was an English mathematician, computer scientist, logician, cryptanalyst, philosopher, and theoretical biologist. Turing was highly influential in the development of theoretical ...

Hacker emblem

Eric S. Raymond Eric Steven Raymond (born December 4, 1957), often referred to as ESR, is an American software developer, open-source software advocate, and author of the 1997 essay and 1999 book ''The Cathedral and the Bazaar''. He wrote a guidebook for the ...

has proposed the glider as an emblem to represent the

hacker A hacker is a person skilled in information technology who uses their technical knowledge to achieve a goal or overcome an obstacle, within a computerized system by non-standard means. Though the term ''hacker'' has become associated in popu ...

subculture, as the Game of Life appeals to hackers, and the concept of the glider was "born at almost the same time as the

Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, p ...

and

Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, ...

". The emblem is in use in various places within the subculture.

References

External links

Glider
at the LifeWiki
The Glider: Proposal for a Hacker Emblem
{{Conway's Game of Life Cellular automaton patterns