Glider destruction

x = 14, y = 14, rule = B3/S23 o$b2o$2o8$12bo$11bobo$10bobo$11bo! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ HEIGHT 600 WIDTH 600 THUMBSIZE 2 ZOOM 18 X 5 Y -1 GPS 20 THEME Book AUTOSTART T 0 PAUSE 2 T 183 PAUSE 2 LOOP 184 ]] A one-glider destruction of the barge still life (click above to open LifeViewer)

Glider destruction of a target pattern is accomplished by hitting the target pattern with gliders that can be rewound arbitrarily far back in time.

In a sense, glider destruction is "the opposite" of glider construction: a glider synthesis is a recipe for constructing the target in surrounding empty space; a glider destruction is a recipe for reducing the target to empty space.

In Conway's Game of Life, for many target objects, glider destruction is significantly easier than glider construction. For example, out of all still lives with 11 or fewer alive cells, only long ship, canoe, very long ship and loaf siamese loaf cannot be cleanly destroyed by a single glider; all of these still lives have 2-glider destructions. Only three out of 12-bit still lives (ship-tie, long³ ship, long⁶ snake) require two gliders for clean destruction.

Cleanup in staged glider synthesis

Some of the most efficient known glider syntheses for various objects require additional gliders to clean up any extra objects produced along with the target, for example this 5G synthesis of cis-boat with nine:

x = 36, y = 22, rule = B3/S23 o11bo$b2o8bo$2o9b3o$16b2o$16bobo$7b3o6bo$9bo$8bo12$34b2o$33b2o$35bo! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ HEIGHT 540 WIDTH 720 THUMBSIZE 2 ZOOM 12 X 5 Y -1 GPS 20 THEME Book AUTOSTART T 0 PAUSE 2 T 77 PAUSE 2 GPS 10 T 90 PAUSE 3 LOOP 91 ]]

A five-glider synthesis of cis-boat with nine, featuring glider destruction of a block (click above to open LifeViewer)

Related problems

As of September 2023, the following questions are unsolved:

• What is the smallest still life without a two-glider destruction?
• Is there a target that is cleanly destroyed by any single hitting glider?
• Is there a "glider-proof" target that can withstand a collision with any single hitting glider?
• Is there a finite target that cannot be destroyed by an unidirectional slow salvo of single gliders?
• Is there a finite target that cannot be destroyed by any number of gliders from any directions, one glider at a time?
• Is there an "invulnerable" target that cannot be destroyed by any interaction from outside?
• Is there a target where every collision between it and a single glider settles into ash with a higher population than the target?

A 8492-bit still life is known (long⁴²⁴³ ship), such that every collision between it and a single glider settles into ash with lower population.

See also

• Lifeline Volume 7, page 1
• Engineered diehard
• Seeds of Destruction
• Fly-by deletion
• IceNine
• Tutorials/Glider syntheses#Assisted cleanup

External links

• indestructible pattern (discussion thread) at the ConwayLife.com forums
• Indestructible object- it’s time we answer the question (discussion thread) at the ConwayLife.com forums
• Glider Destruction Of Still Lives, Oscillators, Etc. (discussion thread) at the ConwayLife.com forums
• Structures resistant to attack (discussion thread) at the ConwayLife.com forums
• Re: Life has been proven omniperiodic. What next? (discussion thread) at the ConwayLife.com forums