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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]


Backrake is another term for a backwards rake. Some xWSS-based examples are shown below.

Name Image Period Population Bounding box Discoverer
Backrake 1 Backrake1.png 8 88 27*18 Jason Summers, 2001
Backrake 2 Backrake2.png 12 65 19*26 David Buckingham
Backrake 2 reduction Wwei23backrake.png 12 39 20*6 wwei23, 2022
Backward version of Space rake Backward space rake.png 20 65 20*22 Unknown
Backrake 3 Backrake3.png 64 124 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.[2][3][4][5] In May 2021, the first elementary oblique rake was found: a (2,1)c/6 rake based on the recently-discovered sprayer.[6] The first clean c/6 orthogonal rake was found by May13 and reduced by iNoMed in November 2021.[7]

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


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

External links