Eater 2

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Eater 2
x = 7, y = 7, rule = B3/S23 3bob2o$b3ob2o$o$b3ob2o$3bobo$3bobo$4bo! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C Still life
Pattern type Strict still life
Number of cells 19
Bounding box 7 × 7
Frequency class 36.0
Discovered by David Buckingham
Year of discovery Unknown

Eater 2 (or block on hat siamese hat) is an eater that was found by David Buckingham in the 1970s.[1] Mostly it works like the standard eater (see eater 1) but with two slight differences that make it useful despite its size; it takes longer to recover from each bite and it acts like an eater in two directions. The first property means that, among other things, it can eat a glider in a position that would destroy an eater 1 due to the latter recovering too quickly before all of the sparks have cleared. This novel glider-eating action is occasionally of use in itself, and combined with the symmetry means that an eater 2 can eat gliders along four different paths.

An eater 2 variant noticed by Stephen Silver in May 1998 that is useful for obtaining smaller bounding boxes is shown below. Note that the canonical version of eater 2 is a strict still life because the outside 15-cell component is not stable without the block (it is, rather, an inductee), but the eater 2 variant below is a pseudo still life because it is made up of an aircraft carrier, block and hat, each of which are stable.

Eater 2 can also be used to eat objects other than gliders. For example, one of them can eat a lightweight or middleweight spaceship, two of them can eat a 60P5H2V0, and so on. Eater 2 catalysts can be found in many stable conduits such as RNE-19T84 and boojum reflector. Its symmetry is exploited in 35P12.1 and p196 pi-heptomino hassler.

It serves as the logo of Catagolue.

Glider synthesis

On January 29, 2004 Mark Niemiec found a 9-glider synthesis of a variation of eater 2 that consists of a hat, a block, and a table. On October 9th, 2014, David S. Miller found a natural eater 2 in a soup from Adam P. Goucher's apgsearch script[2], from which Tanner Jacobi derived a 6-glider synthesis.[3] Another 6-glider recipe with moderate clearance and better adjustability was found by gmc_nxtman on July 14, 2017, involving a boat, a pi-heptomino and a teardrop.[4]


Main article: List of common still lifes

The canonical eater 2 ranks about 400th out of 45,759 in the list of 19-cell still lifes. This puts it barely in the top 1%.


x = 6, y = 9, rule = B3/S23 2o$o$2bob2o$b2ob2o2$b2ob2o$2bobo$2bobo$3bo! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ THUMBSIZE 2 ]]
Eater 2 variant (click above to open LifeViewer)
RLE: here Plaintext: here

See also


  1. Dean Hickerson's oscillator stamp collection. Retrieved on March 14, 2020.
  2. David S. Miller (October 10, 2014). Re: apgsearch: a high-performance soup searcher (discussion thread) at the forums
  3. Tanner Jacobi (November 8, 2014). Re: Soup search results (discussion thread) at the forums
  4. gmc_nxtman (July 14, 2017). Re: Thread for your unsure discoveries (discussion thread) at the forums

External links