A modern computer CPU can execute something like a million instructions.
Light, traveling at one foot per nanosecond, covers 186 miles.
How short an interval can humans perceive? I’m not sure but my own experience with auditory stimuli, trying to resolve one click into two clicks closely spaced in time, back when I was learning about heart sounds, is on the order of 10 milliseconds.
But how fast can you act? Surely much slower than you can perceive! Acting requires formulating the intent to do something in your motor cortex (thought process), then telling the spinal cord, which then activates muscles. The body is fast but not that fast – I don’t think you can literally do anything in the time frame of one millisecond because your nervous system is too slow.
Durations of action potentials – electrical impulses that mediate nerve transmission – are on the order of many milliseconds; transmission speeds are no faster than about 100 meters/second, so to go one meter (from brain to fingertips) takes at least 10 msec just to cover distance, not counting processing along the way.
Even nematocysts, the stinging cells on the tentacles of us jellyfish, take hundreds of milliseconds to fully discharge their coiled tubules ref. But wait, my fellow cnidarians! When our nematocysts are triggered there is an initial deployment of a stylet, like a microscopic harpoon. According to this site,
Nüchter and colleagues used a state-of-the art camera to finally resolve the kinetics of nematocyst discharge. With exposure times as short as 200 ns, they were just able to capture nematocysts in motion for the first time…What they found was truly astounding. Discharge of the barbed stylet was complete in about 700 ns (0.0000007 s), which makes it one of the fastest biological events ever measured.
So there you have it, @ucme, poetic irony and all: Jellyfish take less than a thousandth of a millisecond to grab prey.