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{{Glossary}}
{{Glossary}}
A '''rake''' is a [[puffer]] whose debris consists of [[spaceship]]s. A rake is said to be forwards, backwards or sideways according to the direction of the spaceships relative to the direction of the rake. Originally the term "rake" was applied only to forward c/2 [[glider]] puffers. Many people prefer not to use this term in the case where the puffed spaceships travel parallel or anti-parallel to the puffer, as in this case they do not rake out any significant region of the Life plane (and, in contrast to "true" rakes, these puffers cannot travel in a stream and so could never be produced by a [[gun]]).
A '''rake''' is a [[puffer]] whose debris consists entirely of [[spaceship]]s. A rake is said to be forwards, backwards or sideways according to the direction of the spaceships relative to the direction of the rake. Originally the term "rake" was applied only to forward c/2 [[glider]] puffers. Many people prefer not to use this term in the case where the puffed spaceships travel parallel or anti-parallel to the puffer, as in this case they do not rake out any significant region of the Life plane (and, in contrast to "true" rakes, these puffers cannot travel in a stream and so could never be produced by a [[gun]]).


==Backrakes==
A rake whose debris contains spaceships, but does not solely consist of them, is often called a '''puffrake''' or '''dirty rake'''. The [[glider-producing switch engine]] is one example, as it produces both [[gliders]] and a thick field of other stationary objects.
'''Backrake''' is another term for a backwards rake. [[Backrake 1]] is a [[period]] 8 example that was found by [[Jason Summers]]. [[Backrake 2]] is a period 12 example by [[David Buckingham]]. Other examples include the backwards version of [[space rake]], and [[backrake 3]].


==Important rakes==
A rake may also refer to [[crawler]]s interacting in such a way as to produce spaceships.<ref>{{Cite web|url=http://www.gabrielnivasch.org/fun/life/caterpillar#TOC-Pi-crawlers|title=The Caterpillar spaceship|author=Gabriel Nivasch|accessdate=30 July 2016}}</ref>
The first rake to be constructed was the [[space rake]] sometime around 1971. It and the other early rakes had [[speed]] c/2, though rakes of other velocities have since been built. [[:Category:Patterns found by Dean Hickerson|Dean Hickerson]]'s construction of [[Cordership]]s in [[:Category:Patterns found in 1991|1991]] made it easy for c/12 diagonal rakes to be built, although no one actually did this until [[:Category:Patterns found in 1998|1998]], by which time [[:Category:Patterns found by David Bell|David Bell]] had constructed c/3 and c/5 rakes (in May [[:Category:Patterns found in 1996|1996]] and September [[:Category:Patterns found in 1997|1997]], respectively). [[:Category:Patterns found by Jason Summers|Jason Summers]] constructed a 2c/5 rake in June [[:Category:Patterns found in 2000|2000]] (building on work by [[:Category:Patterns found by Paul Tooke|Paul Tooke]] and [[:Category:Patterns found by David Bell|David Bell]]) and a c/4 orthogonal rake in October [[:Category:Patterns found in 2000|2000]] (based largely on reactions found by David Bell).  Ivan Fomichev completed the first 2c/7 rake, the [[weekender distaff]], on May 22, [[:Category:Patterns found in 2014|2014]]
 
== Backrakes ==
'''Backrake''' is a rake that produces [[backward glider]]s or other backward spaceships. Some [[xWSS]]-based examples are shown below.
 
{|class="wikitable sortable" style="margin-left:auto; margin-right:auto; clear:both; text-align:center"
! [[Period]] !! Name !! Image !! [[Population]] !! [[Bounding box]]!! Discoverer
|-
|8||[[Backrake 1]]||[[File:Backrake1.png|96px]]||88||{{times|27|18}}||[[Jason Summers]], [[2001]]
|-
|rowspan=2|12||[[Backrake 2]]||[[File:Backrake2.png|96px]]||65||{{times|19|26}}||[[David Buckingham]]
|-
|[[backrake_2#reduction|Backrake 2 reduction]]||[[File:wwei23backrake.png|96px]]||39||{{times|20|6}}||[[Aleph]], [[2022]]
|-
|rowspan=2|16||[[Coe ship]] backrake|| ||60||{{times|22|17}}||unknown
|-
|[[31P8H4V0]] backrake|| ||79<!--66 if one removes the reactants and block preimage in the 31P8H4V0-->||{{times|18|26}}||[[Caleb R. Hilton]], 2025
|-
|20||Backward version of [[Space rake]]||[[File:Backward space rake.png|96px]]||65||{{times|20|22}}||Unknown
|-
|24||[[Schick engine]] backrake|| ||56||{{times|22|20}}||[[Paul Schick]], 1973<ref>{{CiteLifeline|vol=9|pages=page 5}}</ref>
|-
|64||[[Backrake 3]]||[[File:Backrake3.png|96px]]||124||{{times|22|103}}||Unknown
|-
|}
 
== Important rakes ==
The first rake to be constructed was the [[space rake]] sometime around 1971. It and the other early rakes had [[speed]] c/2, though rakes of other velocities have since been built. [[Dean Hickerson]]'s construction of [[Cordership]]s in {{year|1991}} made it easy for c/12 diagonal rakes to be built, although no one actually did this until {{year|1998}}, by which time [[David Bell]] had constructed c/3 and c/5 rakes (in May {{year|1996}} and September {{year|1997}}, respectively). [[Jason Summers]] constructed a 2c/5 rake in June {{year|2000}} (building on work by [[Paul Tooke]] and [[David Bell]]) and a c/4 orthogonal rake in October {{year|2000}} (based largely on reactions found by David Bell).  Ivan Fomichev completed the first 2c/7 rake, the [[weekender distaff]], on May 22, {{year|2014}}. Multiple [[c/10 orthogonal]] rakes were made with copperhead technology in {{year|2016}}.<ref name="post28969" /><ref name="post28979" /><ref name="post33383" /><ref name="post38695" /> In May {{year|2021}}, the first [[elementary]] [[oblique]] rake was found: a [[(2,1)c/6]] rake based on the recently-discovered [[sprayer]].<ref name="message841117178475577365" /> The first clean [[c/6 orthogonal]] rake was found by [[May13]] and reduced by [[iNoMed]] in November {{year|2021}}.<ref name="post137751" />


The smallest possible period for a rake is believed to be 7, which could be achieved by a 3c/7 orthogonal backwards glider puffer. The smallest period found to date is 8, attained by [[backrake 1]].
The smallest possible period for a rake is believed to be 7, which could be achieved by a 3c/7 orthogonal backwards glider puffer. The smallest period found to date is 8, attained by [[backrake 1]].


==See also==
== See also ==
*[[:Category:Rakes|List of rakes]]
* {{CategoryLink|Rakes}}
 
== External links ==
* {{LinkWikipedia|Rake_(cellular_automaton)}}
* {{LinkLexicon|lex_r.htm#rake}}
 
== References ==
<references>
<ref name="post28969">{{LinkForumThread
|format = ref
|title  = Re: is this c/10 spaceship known?
|p      = 28969
|author = Nora Brown
|date  = March 20, 2016
}}</ref>
<ref name="post28979">{{LinkForumThread
|format = ref
|title  = Re: is this c/10 spaceship known?
|p      = 28979
|author = Matthias Merzenich
|date  = March 20, 2016
}}</ref>
<ref name="post33383">{{LinkForumThread
|format = ref
|title  = Re: is this c/10 spaceship known?
|p      = 33383
|author = christoph.r
|date  = July 19, 2016
}}</ref>
<ref name="post38695">{{LinkForumThread
|format = ref
|title  = Re: is this c/10 spaceship known?
|p      = 38695
|author = christoph.r
|date  = December 26, 2016
}}</ref>
<ref name="message841117178475577365">{{CiteDiscord
|format = ref
|channel = cgol
|id = 841117178475577365
|author = Adam P. Goucher
|date = May 9, 2021}}</ref>
<ref name="post137751">{{LinkForumThread
|format = ref
|title  = Re: Spaceship Discussion Thread
|p      = 137751
|author = May13
|date  = November 16, 2021
}}</ref>
</references>


==External links==
__NOTOC__
*[http://www.argentum.freeserve.co.uk/lex_r.htm#rake Rake] at the Life Lexicon

Latest revision as of 14:23, 16 August 2026

A rake is a puffer whose debris consists entirely of spaceships. A rake is said to be forwards, backwards or sideways according to the direction of the spaceships relative to the direction of the rake. Originally the term "rake" was applied only to forward c/2 glider puffers. Many people prefer not to use this term in the case where the puffed spaceships travel parallel or anti-parallel to the puffer, as in this case they do not rake out any significant region of the Life plane (and, in contrast to "true" rakes, these puffers cannot travel in a stream and so could never be produced by a gun).

A rake whose debris contains spaceships, but does not solely consist of them, is often called a puffrake or dirty rake. The glider-producing switch engine is one example, as it produces both gliders and a thick field of other stationary objects.

A rake may also refer to crawlers interacting in such a way as to produce spaceships.[1]

Backrakes

Backrake is a rake that produces backward gliders or other backward spaceships. Some xWSS-based examples are shown below.

Period Name Image Population Bounding box Discoverer
8 Backrake 1 88 27 × 18 Jason Summers, 2001
12 Backrake 2 65 19 × 26 David Buckingham
Backrake 2 reduction 39 20 × 6 Aleph, 2022
16 Coe ship backrake 60 22 × 17 unknown
31P8H4V0 backrake 79 18 × 26 Caleb R. Hilton, 2025
20 Backward version of Space rake 65 20 × 22 Unknown
24 Schick engine backrake 56 22 × 20 Paul Schick, 1973[2]
64 Backrake 3 124 22 × 103 Unknown

Important rakes

The first rake to be constructed was the space rake sometime around 1971. It and the other early rakes had speed c/2, though rakes of other velocities have since been built. Dean Hickerson's construction of Corderships in 1991 made it easy for c/12 diagonal rakes to be built, although no one actually did this until 1998, by which time David Bell had constructed c/3 and c/5 rakes (in May 1996 and September 1997, respectively). Jason Summers constructed a 2c/5 rake in June 2000 (building on work by Paul Tooke and David Bell) and a c/4 orthogonal rake in October 2000 (based largely on reactions found by David Bell). Ivan Fomichev completed the first 2c/7 rake, the weekender distaff, on May 22, 2014. Multiple c/10 orthogonal rakes were made with copperhead technology in 2016.[3][4][5][6] In May 2021, the first elementary oblique rake was found: a (2,1)c/6 rake based on the recently-discovered sprayer.[7] The first clean c/6 orthogonal rake was found by May13 and reduced by iNoMed in November 2021.[8]

The smallest possible period for a rake is believed to be 7, which could be achieved by a 3c/7 orthogonal backwards glider puffer. The smallest period found to date is 8, attained by backrake 1.

See also

References

  1. ↑ Gabriel Nivasch. "The Caterpillar spaceship". Retrieved on 30 July 2016.
  2. ↑ Robert Wainwright (March 1973). Lifeline, vol 9, page 5.
  3. ↑ Nora Brown (March 20, 2016). Re: is this c/10 spaceship known? (discussion thread) at the ConwayLife.com forums
  4. ↑ Matthias Merzenich (March 20, 2016). Re: is this c/10 spaceship known? (discussion thread) at the ConwayLife.com forums
  5. ↑ christoph.r (July 19, 2016). Re: is this c/10 spaceship known? (discussion thread) at the ConwayLife.com forums
  6. ↑ christoph.r (December 26, 2016). Re: is this c/10 spaceship known? (discussion thread) at the ConwayLife.com forums
  7. ↑ Adam P. Goucher (May 9, 2021). Message in #cgol on the Conwaylife Lounge Discord server
  8. ↑ May13 (November 16, 2021). Re: Spaceship Discussion Thread (discussion thread) at the ConwayLife.com forums


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