Boojum reflector

Boojum reflector
x = 44, y = 32, rule = B3/S23 4bobo6b2o$5b2o6b2o$5bo7$40bo$39bobo$39bobo$20b2o16b2ob2o$20b2o$38b2ob 2o$2b2o34b2obo$bobo39bo$bo40b2o$2o2$34b2o$34b2o4b2o$11b2o27bobo$10bobo 29bo$10bo31b2o$9b2o23b2o$34b2o3$29bo$28bobo$29bo! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ AUTOSTART ]] #C [[ HEIGHT 400 THUMBSIZE 2 ZOOM 10 GPS 20 LOOP 240 ]]
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Pattern type	Stable reflector
Number of cells	60
Bounding box	44 × 32
Angle	180°
Repeat time	202
Colour	Colour-preserving
Discovered by	Dave Greene
Year of discovery	2001
Rules Outer-totalistic rules B3/S23 – B3/S238 # of rules 21 = 2 Isotropic rules B3/S23 – B3/S234c8
Pattern files Plaintext boojumreflector.cells RLE boojumreflector.rle

The boojum reflector is a 180° glider reflector found by Dave Greene in April 2001 as a modification of Paul Callahan's Herschel receiver, winning $100 bounties offered by Alan Hensel and Dieter Leithner. The name is taken from Lewis Carroll's The Hunting of the Snark, referring to the fact that a small 90-degree stable reflector was really what was wanted.

The boojum reflector was both the smallest and fastest known stable reflector, until it was superseded by the rectifier in 2009 and the Snark in 2013.

The boojum reflector produces an unwanted beehive, which is then deleted by a later glider. If the beehive is removed before the latter glider hits it, the glider will leave the reflector. This reaction can be seen in this p226 glider shuttle:

x = 76, y = 50, rule = B3/S23 15bo$14bobo$15bo3$9b2o$9b2o23b2o$b2o31bo$2bo29bobo$2bobo27b2o$3b2o4b2o $9b2o2$43b2o$43bo$41bobo$3bob2o34b2o$b3ob2o$o22b2o19b2o$b3ob2o16b2o11b o7b2o$3bobo31bo$3bobo29b3o$4bo4$52b2o$44b2o5b2o18bo$43bo2bo7bo15bobo$ 38b2o4b2o4bo2bo16bobo$30b2o5b2o14b2ob3o10b2ob3o$30b2o7bo13b5obo15bo$ 50b2o6b3o8b2ob3o$33b2o17bo5b2o9b2obo$32bobo18bo2bob2o$32bo19b2ob5o$31b 2o18bob2o2b3o$51bobo$51bo13b2o$65b2o4b2o$42b2o6b3o18bobo$41bobo29bo$ 41bo31b2o$40b2o23b2o$65b2o3$60bo$59bobo$60bo! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ WIDTH 840 HEIGHT 560 THUMBSIZE 2 ZOOM 10 GPS 20 AUTOSTART LOOP 226 ]]

p226 glider shuttle (click above to open LifeViewer) RLE: here Plaintext: here Catagolue: here

A different type of Boojum shuttle is possible by switching the output gliders and the beehive deleting gliders. The corresponding beehive-glider collision does not become nothing by itself, but the block from that boojum serves as a catalyst for the successful removal.

x = 73, y = 51, rule = B3/S23 14bo$13bobo$14bo3$8b2o$8b2o23b2o$2o31bo$bo29bobo$bobo27b2o$2b2o4b2o$8b 2o2$42b2o$2o40bo$o39bobo$2bob2o34b2o$b2ob2o$22b2o$b2ob2o16b2o18b2o$2b obo37b2o$2bobo25bo$3bo25b2o$29bobo4$41bobo$42b2o25bo$42bo25bobo$29b2o 37bobo$29b2o18b2o16b2ob2o$49b2o$67b2ob2o$31b2o34b2obo$30bobo39bo$30bo 40b2o$29b2o2$63b2o$63b2o4b2o$40b2o27bobo$39bobo29bo$39bo31b2o$38b2o23b 2o$63b2o3$58bo$57bobo$58bo! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ WIDTH 840 HEIGHT 560 THUMBSIZE 2 ZOOM 10 GPS 20 AUTOSTART LOOP 225 ]]

(click above to open LifeViewer) RLE: here Plaintext: here Catagolue: here

In December 20, Luke Kiernan used Barrister to complete a boojum reflector variant with the beehive eaten by surrounding chaos.

x = 52, y = 32, rule = B3/S23 20b2o$20b2o5$4b2o$4bobo$7bo$5b2obo38bo$4bo2bo38bobo$4b2o17bo22bobo$b2o bo19b2ob2o16b2ob3o$bo2bo18b2o2b2o22bo$3bo4b2o35b2ob3o$bob2o3b2o35b2ob o$obo$o2b2o$bobo6b2o$2o2bo5bo3b2o$3b2o2b2obo4bo25b2o$7bo2bob3o26b2o4b 2o$9b2obo5b2o27bobo$17bobo29bo$17bo31b2o$16b2o23b2o$41b2o3$36bo$35bob o$36bo! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ WIDTH 840 HEIGHT 560 THUMBSIZE 2 ZOOM 10 GPS 20 AUTOSTART T 0 PAUSE 2 LOOP 225 ]]

(click above to open LifeViewer)

External links

• Boojum reflector at the Life Lexicon