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Glider synthesis (or glider construction) is the construction of an object by means of glider collisions. It is generally assumed that the gliders should be arranged so that they could come from infinity  that is, gliders should not have had to pass through one another to achieve the initial arrangement.
Four main characterizing features of a synthesis are the geometry, reaction speed, reaction multiplicity, and glider cost. Of particular interest is slow salvo synthesis: unidirectional synthesis where every stage has a glider cost of one, and thus the number of stages (i.e., the multiplicity) is equal to the total cost. Perhaps surprisingly, anything that is glider synthesizable is also slow salvo synthesizable.
In the 1990s, glider syntheses for all still lifes and known oscillators with at most 14 cells were found by David Buckingham. Almost all of these were successfully reduced to a synthesis cost of less than 1 glider per live cell, or "1 glider per bit". A collaborative effort ending in May 2014 completed glider syntheses of all still lifes with 17 or fewer cells. A second, longer effort completed all the 18bit still lifes in November 2014. Later optimization projects reduced the maximum cost of construction for 15bit and 16bit still lifes to less than one glider per bit.

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Did you know...

 ... that two completely different types of oblique spaceships, the waterbear and the halfbaked knightship, were constructed in 2014?
 ... that no Caterpillartype spaceships were completed for almost ten years after the original Caterpillar was constructed in 2004, but that two different designs, the waterbear and the centipede, were finished in 2014?
 ... that the first spiralgrowth pattern in Conway's Life was constructed in 2014?
 ... that among known glider recipes for irreducible objects, the Gemini spaceship has the largest known minimal recipe, currently 173,449 gliders — the runnerup being the Parallel HBK with a 38,380glider synthesis?
 ... that it was shown in 2014 that any salvo of gliders, no matter how tightly packed, can be constructed by crashing together gliders whose initial positions are farther apart than any chosen finite distance?
 ... that no spaceships with velocities other than c/4 diagonal (glider), c/2 orthogonal (*WSS variants), and c/12 diagonal (Corderships) had known glider syntheses until 2003, when a 2c/5 spaceship gun was constructed?
 ... that after ten years with no new small spaceship syntheses, a glider construction was found for the c/7 loafer in 2013 less than three hours after its discovery?
 ... that glider constructions for three previously inconstructible spaceships (the dart, the crab, and the Parallel HBK) were discovered in 2014?
 ... that glider constructions for the B29, X66, halfX66 with HWSS, Pushalong 1, 25P3H1V0.1, 30P5H2V0, 30P4H2V0.4, a pufferfish spaceship, and the weekender were discovered in 2015 — after fifteen years of intermittent efforts in the case of the weekender?
 ... that since 2014, more new spaceship syntheses have been completed than were found in all the years between 1970 and 2013?

