A lightspeed bubble is a type of negative spaceship traveling through the zebra stripesagar. The center of the bubble is simple empty space, and the length and/or width of the bubble can usually be extended to any desired size.
Below is a small stabilized section of agar containing a sample lightspeed bubble, found by Gabriel Nivasch in August 1999. The bubble travels to the left at the speed of light, so it will eventually reach the edge of any finite patch and destroy itself and its supporting agar.
x = 58, y = 58, rule = B3/S23:T58,58
$58o2$58o2$58o2$58o2$58o2$58o2$9o2b3o2b3o2b37o$10b2o3b2o3b2o8bo$9o3b2o
3b2o3bob2obo4b26o$24b2o5bo$9o17b32o$27bo$9o19b30o$28bo4bo$9o19b2o4b24o
$28bo5bo4bo$9o19b2o4b2o4b18o$28bo5bo5bo4bo$9o19b2o4b2o4b2o4b12o$28bo5b
o5bo5bo4bo$9o19b2o4b2o4b2o4b2o4b6o$28bo5bo5bo5bo5bo$9o19b2o4b2o4b2o4b
2o4b6o$28bo5bo5bo5bo4bo$9o19b2o4b2o4b2o4b12o$28bo5bo5bo4bo$9o19b2o4b2o
4b18o$28bo5bo4bo$9o19b2o4b24o$28bo4bo$9o19b30o$27bo$9o17b32o$24b2o5bo
$9o3b2o3b2o3bob2obo4b26o$10b2o3b2o3b2o8bo$9o2b3o2b3o2b37o2$58o2$58o2$
58o2$58o2$58o2$58o2$58o!
#C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]]
#C [[ THUMBSIZE 2 ZOOM 9.2 HEIGHT 500 GPS 15 AUTOSTART LOOP 115 PAUSE 1 ]]
#C Will it be better if people can see the sides of the torus?
An open problem related to lightspeed bubbles was whether large extensible empty areas could be created whose length was not proportional to the width (as it must be in the above case, due to the tapering back edge). This was solved in February 2017 by Arie Paap;[1] a simple period-2 solution is shown below.