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 = 180, y = 60, rule = B3/S23:T100,58
$180o2$180o2$180o2$180o2$180o2$180o2$74o2b3o2b3o2b94o$75b2o3b2o3b2o8b
o$74o3b2o3b2o3bob2obo4b83o$89b2o5bo$74o17b89o$92bo$74o19b87o$93bo4bo$
74o19b2o4b81o$93bo5bo4bo$74o19b2o4b2o4b75o$93bo5bo5bo4bo$74o19b2o4b2o
4b2o4b69o$93bo5bo5bo5bo4bo$74o19b2o4b2o4b2o4b2o4b63o$93bo5bo5bo5bo5bo
$74o19b2o4b2o4b2o4b2o4b63o$93bo5bo5bo5bo4bo$74o19b2o4b2o4b2o4b69o$93b
o5bo5bo4bo$74o19b2o4b2o4b75o$93bo5bo4bo$74o19b2o4b81o$93bo4bo$74o19b87o
$92bo$74o17b89o$89b2o5bo$74o3b2o3b2o3bob2obo4b83o$75b2o3b2o3b2o8bo$74o
2b3o2b3o2b94o2$180o2$180o2$180o2$180o2$180o2$180o2$180o!
#C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]]
#C [[ THUMBSIZE 2 ZOOM 9.2 HEIGHT 500 GPS 15 AUTOSTART ]]
#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.