Spaceship

A lightweight spaceship

A spaceship (or, much less commonly, a fish) is a finite pattern that reappears (without additions or losses) after a number of generations (known as its period) and is displaced by a non-zero amount. By far the most naturally-occurring spaceships are the glider, lightweight spaceship, middleweight spaceship and heavyweight spaceship.

It is known that there exist spaceships travelling in all rational directions and at arbitrarily slow speeds (see universal constructor). Before 1989, however, the only known examples travelled at c/4 diagonally (gliders) or c/2 orthogonally (everything else). In 1989, Dean Hickerson started to use automated searches to look for new spaceships, and had considerable success. Other people have continued these searches using tools such as lifesrc and gfind, and as a result there are now a great variety of known spaceships travelling at ten different velocities.

Speed First discovered Discoverer Year of discovery c/2 Lightweight Spaceship John Conway 1970 c/3 ? Dean Hickerson 1989 c/4 ? Dean Hickerson 1989 c/5 Snail Tim Coe 1996 2c/5 ? Dean Hickerson 1991 c/6 Dragon Paul Tooke 2000 2c/7 Weekender David Eppstein 2000 17c/45 Caterpillar Gabriel Nivasch 2004 c/4 Diagonal Glider Richard Guy 1970 c/5 Diagonal ? Jason Summers 2000 c/6 Diagonal Seal Paul Tooke 2000 c/12 Diagonal Cordership Dean Hickerson 1991

Speed Smallest known Minimum # of cells c/2 Lightweight Spaceship 9 c/5 Spider 58 c/6 Dragon 102 2c/7 Weekender 36 c/4 Diagonal Glider 5 c/6 Diagonal Seal 170 c/12 Diagonal 4-engine Cordership 134

See also

• List of spaceships
• Spaceship terminology
• Types of spaceships

External links

• Spaceship at the Life Lexicon