But if you surrounded an event with a sphere of sensors, there is still an upper limit. The number of sensors is a function of sphere radius, and whether they a

But if you surrounded an event with a sphere of sensors, there is still an upper limit. The number of sensors is a function of sphere radius, and whether they are limited to the surface of the sphere (which is reasonable since tightly packed sensors will, in general, get in the way of other sensors). A sphere 1km across has a surface are of 4pi1km^2 which is roughly 10^7m^2. If you had 1cm^2 sensors then you get 10^4 sensors per m^2, which means you get 10^11 sensors total. At 11k fps (10^4) that's a total of 10^15 fps. Note that Planck time is 10^-44 so such an arrangement probably wouldn't help for detecting quantum gravity because you'd run out of matter in the universe before you could construct the sensors.