A negative spaceship is a a type of signal traveling through a periodic agar such as zebra stripes. The leading edge of the signal removes the agar, and the trailing edge rebuilds the agar some time later. The distance between the two edges is sometimes adjustable, as shown in lightspeed bubble. The central part of the "spaceship" may consist of dying sparks or even simple empty space.

... that the first stable reflector was found in October 1996, and the first fast stable reflector appeared in 2013, allowing the construction of oscillators of all periods ≥43 ticks?

... that twenty-four spaceship velocities have been constructed, including five infinitely adjustable families of ships?

... that there are 71 distinct ways for two gliders to collide, but it is unknown how many distinct 3-glider collisions there are?

... that to display the smallest known gun pattern for a Gemini spaceship at 1 cell = 1 pixel, on a standard-density video monitor, a screen over one mile square would be needed?

... that no odd-period glider guns were known before 1995, when a period 565 p5-spark-assisted B-heptomino loop was constructed by David Buckingham?

... that even though the speed limit for spaceships is c/2 in a vacuum, in a medium of stripes agar there are "spaceships" that can travel at lightspeed along the stripes, or two thirds of lightspeed perpendicular to the stripes?