Gun

A gun is a stationary pattern that emits spaceships (or rakes) repeatedly forever. The most common type of guns are glider guns, which emit gliders (the most well-known of which is the Gosper glider gun), though guns that emit other spaceships such as lightweight spaceships are known.

Pseudo-period guns

A pseudo-period gun (as opposed to a true-period gun) is a gun that emits a period n stream of spaceships (or rakes) via a mechanism that oscillates with a period different from n -- this period will necessarily be a multiple of n. Pseudo period n glider guns are known to exist for all periods greater than or equal to 14, with smaller periods being impossible. The first pseudo p14 gun was built by Dieter Leithner in 1995.

True-period guns

A true-period gun (as opposed to a pseudo-period gun) is a gun that emits a period n stream of spaceships (or rakes) via a mechanism oscillates with period equal to n. True period n guns are known to exist for all periods greater than 61, but only a few smaller periods have been achieved, namely 22, 24, 30, 44, 46, 48, 50, 54, 55, 56 and 60. Credits for these small period guns are: p30, p46 and p60 by Bill Gosper in 1970-1971, p44 by David Buckingham in 1992, p50 by Dean Hickerson in 1996, p24 and p48 by Noam Elkies in 1997, p54 and p56 by Dieter Leithner in early 1998, p55 by Stephen Silver in late 1998 and p22 by David Eppstein in 2000.

See also

• List of guns

External links

• Gun at the Life Lexicon