Spaceship: Difference between revisions
added to the history section, but it still needs references (I wrote it based on what I know, so there might be some mistakes) |
added a new section (spaceship types), as well as some unnamed spaceships which are (to my knowledge) correct |
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{{Glossary}} | {{Glossary}} | ||
[[Image:lwss.gif|framed|right| | [[Image:lwss.gif|framed|right|The lightweight spaceship in [[Conway's Game of Life]]]]A '''spaceship''' (much less commonly referred to as a '''glider'''<ref>{{cite web|url=http://www.argentum.freeserve.co.uk/lex_g.htm#glider |title=Glider |work=The Life Lexicon |publisher=Stephen Silver |accessdate=April 18, 2009}}</ref> or a '''fish'''<ref>{{cite web|url=http://www.argentum.freeserve.co.uk/lex_f.htm#fish |title=Fish |work=The Life Lexicon |publisher=Stephen Silver |accessdate=April 18, 2009}}</ref>) is a finite pattern that returns to its initial state after a number of generations (known as its [[Period#Spaceships|period]]) but in a different location. | ||
| Line 7: | Line 7: | ||
==Spaceship Speed== | ==Spaceship Speed== | ||
{{main|Speed}} | {{main|Speed}} | ||
The speed of a spaceship is the number of cells that the pattern moves during its period. This is expressed in terms of ''c'' (the metaphorical "speed of light") which is one cell per generation; thus, a spaceship with a period of five that moves two cells to the left during its period travels at a speed of 2c/5. All known spaceships in life travel either orthogonally ( | The speed of a spaceship is the number of cells that the pattern moves during its period. This is expressed in terms of ''c'' (the metaphorical "speed of light") which is one cell per generation; thus, a spaceship with a period of five that moves two cells to the left during its period travels at a speed of 2c/5. All known spaceships in life travel either orthogonally (only horizontal or vertical displacement) or diagonally (equal horizontal and vertical displacement) at one of the twelve known speeds; however spaceships traveling in other directions and at different speeds have been constructed in other two dimensional cellular automata<ref>{{cite web|url=http://fano.ics.uci.edu/ca/ |title=Gliders in Life-Like Cellular Automata |publisher=David Eppstein|accessdate=April 18, 2009}}</ref>, and it is known that Life has spaceships that travel in all rational directions at arbitrarily slow speeds (see [[universal constructor]]). | ||
==History== | ==History== | ||
| Line 19: | Line 19: | ||
The most recently discovered spaceship speed is the diagonal c/6 [[seal]], found by [[Nicolay Beluchenko]] in 2005<ref>{{cite web|url=http://pentadecathlon.com/lifeNews/2005/09/c6_diagonal_spaceship_1.html |title=c/6 Diagonal Spaceship |work=Game of Life News |publisher=H. Koenig}}</ref>. | The most recently discovered spaceship speed is the diagonal c/6 [[seal]], found by [[Nicolay Beluchenko]] in 2005<ref>{{cite web|url=http://pentadecathlon.com/lifeNews/2005/09/c6_diagonal_spaceship_1.html |title=c/6 Diagonal Spaceship |work=Game of Life News |publisher=H. Koenig}}</ref>. | ||
{| class="wikitable" | {| class="wikitable" | ||
|- | |- | ||
| Line 60: | Line 59: | ||
| [[weekender]] | | [[weekender]] | ||
| [[:Category:Patterns found by David Eppstein|David Eppstein]] | | [[:Category:Patterns found by David Eppstein|David Eppstein]] | ||
| 2000 | | [[:Category:Patterns found in 2000|2000]] | ||
|- | |- | ||
! 17c/45 | ! 17c/45 | ||
| Line 73: | Line 72: | ||
|- | |- | ||
! c/5 Diagonal | ! c/5 Diagonal | ||
| | | 295P5H1V1.1 | ||
| [[:Category:Patterns found by Jason Summers|Jason Summers]] | | [[:Category:Patterns found by Jason Summers|Jason Summers]] | ||
| [[:Category:Patterns found in 2000|2000]] | | [[:Category:Patterns found in 2000|2000]] | ||
| Line 87: | Line 86: | ||
| [[:Category:Patterns found in 1991|1991]] | | [[:Category:Patterns found in 1991|1991]] | ||
|- | |- | ||
|} | |} | ||
==Spaceship types== | |||
{{main|Types of spaceships|Spaceship types}} | |||
Although Spaceships are most commonly categorized by their speed and direction, other categorizations have been applied to spaceships with similar components, properties, or appearances. One such categorization is the symmetry of spaceships; spaceships can be bilaterally symmetric, Such as Tim Coe's snail, may exhibit [[Types_of_spaceships#Glide_symmetric_spaceship|glide symmetry]], such as the glider, or may be asymmetric, such as the caterpillar. Other, somewhat subjective categorizations have also been made, such as the [[greyship]], a spaceship filled with large amounts of static, live cells, or [[Types_of_spaceships#Smoking_ship|Smoking ships]] that produce large [[spark]]s, a notable example of which is the [[schick engine]]. A spaceship may also support another component which would not function as a spaceship on its own; these additional components are often referred to as tagalongs, and spaceships created using these reactions are known as [[Types_of_spaceships#Flotilla|flotilla]]. a well known example of spaceship tagalong is the [[overweight spaceship]], which is unstable on its own but may be 'escorted' by smaller spaceships. | |||
{| class="wikitable" | {| class="wikitable" | ||
|- | |- | ||
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| lightweight spaceship | | lightweight spaceship | ||
| [[:Category:Patterns with 9 cells|9]] | | [[:Category:Patterns with 9 cells|9]] | ||
|- | |||
! c/3 | |||
| 25P3H1V0.1 and 25P3H1V0.2 | |||
| [[:Category:Patterns with 25 cells|25]] | |||
|- | |||
! c/4 | |||
| 46P4H1V0.1 | |||
| [[:Category:Patterns with 46 cells|46]] | |||
|- | |||
! 2c/5 | |||
| 30P5H2V0.1 | |||
| [[:Category:Patterns with 30 cells|30]] | |||
|- | |- | ||
! c/5 | ! c/5 | ||
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| glider | | glider | ||
| [[:Category:Patterns with 5 cells|5]] | | [[:Category:Patterns with 5 cells|5]] | ||
|- | |||
! c/5 Diagonal | |||
| 67P5H1V1.1 | |||
| [[:Category:Patterns with 67 cells|67]] | |||
|- | |- | ||
! c/6 Diagonal | ! c/6 Diagonal | ||
| Line 126: | Line 146: | ||
| [[:Category:Patterns with 134 cells|134]] | | [[:Category:Patterns with 134 cells|134]] | ||
|} | |} | ||
==See also== | ==See also== | ||
Revision as of 01:00, 19 April 2009
A spaceship (much less commonly referred to as a glider[1] or a fish[2]) is a finite pattern that returns to its initial state after a number of generations (known as its period) but in a different location.
Spaceship Speed
- Main article: Speed
The speed of a spaceship is the number of cells that the pattern moves during its period. This is expressed in terms of c (the metaphorical "speed of light") which is one cell per generation; thus, a spaceship with a period of five that moves two cells to the left during its period travels at a speed of 2c/5. All known spaceships in life travel either orthogonally (only horizontal or vertical displacement) or diagonally (equal horizontal and vertical displacement) at one of the twelve known speeds; however spaceships traveling in other directions and at different speeds have been constructed in other two dimensional cellular automata[3], and it is known that Life has spaceships that travel in all rational directions at arbitrarily slow speeds (see universal constructor).
History
the four smallest spaceships in life, the glider, lightweight spaceship, middleweight spaceship and heavyweight spaceship, were all found by hand in 1970. For almost twenty years spaceship development was limited to adding tagalongs to the known c/2 spaceships. Significant advances in spaceship technology came in 1989, when Dean Hickerson began using automated searches based on a depth-first backtracking algorithm. These searches found orthogonal spaceships with speeds of c/3, c/4, and 2c/5, and also the first spaceship to move at the speed of c/4 diagonally other than the glider, dubbed the big glider. Hickerson also found a way to combine switch engines to create the first diagonal c/12 spaceship. The next new spaceship speed to be discovered was the orthogonal c/5 snail, found by Tim Coe in 1996, with a program he had designed using breadth first searching, and which could split tasks between multiple CPUs[4]. In the following year David Bell found a smaller c/5 spaceship using Lifesrc, a program based on Hickerson's search algorithm[5].
In March of 1998 David Eppstein created gfind, a search program that used a combination of breadth first search and depth first iterated deepening[6], and in 2000 he used this program to find the first spaceship to travel at the speed of 2c/7 orthogonally, the weekender. A search by Paul Tooke using the same program found the first c/6 orthogonal spaceship, the dragon, later that year. Also in 2000, Jason Summers found the first c/5 diagonal spaceship using David Bell's Lifesrc program.
In 2004 Gabriel Nivasch, with the help of Jason Summers and David Bell, finished construction on the caterpillar, the first known orthogonal 17c/45 spaceship. The caterpillar's design is unique in that it is made entirely of simple component parts and reactions, including many gliders and small orthogonal c/2 spaceships[7].
The most recently discovered spaceship speed is the diagonal c/6 seal, found by Nicolay Beluchenko in 2005[8].
| 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 | 295P5H1V1.1 | Jason Summers | 2000 |
| c/6 Diagonal | seal | Nicolay Beluchenko | 2005 |
| c/12 Diagonal | Cordership | Dean Hickerson | 1991 |
Spaceship types
- Main article: Spaceship types
Although Spaceships are most commonly categorized by their speed and direction, other categorizations have been applied to spaceships with similar components, properties, or appearances. One such categorization is the symmetry of spaceships; spaceships can be bilaterally symmetric, Such as Tim Coe's snail, may exhibit glide symmetry, such as the glider, or may be asymmetric, such as the caterpillar. Other, somewhat subjective categorizations have also been made, such as the greyship, a spaceship filled with large amounts of static, live cells, or Smoking ships that produce large sparks, a notable example of which is the schick engine. A spaceship may also support another component which would not function as a spaceship on its own; these additional components are often referred to as tagalongs, and spaceships created using these reactions are known as flotilla. a well known example of spaceship tagalong is the overweight spaceship, which is unstable on its own but may be 'escorted' by smaller spaceships.
| Speed | Smallest known | Minimum # of cells |
|---|---|---|
| c/2 | lightweight spaceship | 9 |
| c/3 | 25P3H1V0.1 and 25P3H1V0.2 | 25 |
| c/4 | 46P4H1V0.1 | 46 |
| 2c/5 | 30P5H2V0.1 | 30 |
| c/5 | spider | 58 |
| c/6 | dragon | 102 |
| 2c/7 | weekender | 36 |
| 17c/45 | caterpillar | 11880063 |
| c/4 Diagonal | glider | 5 |
| c/5 Diagonal | 67P5H1V1.1 | 67 |
| c/6 Diagonal | seal | 170 |
| c/12 Diagonal | 4-engine Cordership | 134 |
See also
Notes
- ↑ "Glider". The Life Lexicon. Stephen Silver. Retrieved on April 18, 2009.
- ↑ "Fish". The Life Lexicon. Stephen Silver. Retrieved on April 18, 2009.
- ↑ "Gliders in Life-Like Cellular Automata". David Eppstein. Retrieved on April 18, 2009.
- ↑ Tim Coe. "c/5 Orthogonal spaceship". Paul's Page of Conway's Life Miscellany. Retrieved on April 18, 2009.
- ↑ David Bell. "New c/5 spaceship". Paul's Page of Conway's Life Miscellany. Retrieved on April 18, 2009.
- ↑ David Eppstein. "Searching for Spaceships (PDF)". Retrieved on April 18, 2009.
- ↑ Gabriel Nivasch. "The 17c/45 Caterpillar spaceship". Gabriel Nivasch's Game of Life page.
- ↑ "c/6 Diagonal Spaceship". Game of Life News. H. Koenig.
External links
- Spaceship at the Life Lexicon