Asked by: Lillia Nelson (age 10), Hampshire
When you watch a film, the cinema projects a series of still frames one after the other, but you perceive it as continuous motion because each frame is only shown for about 40 milliseconds.
In fact, under ideal conditions we can spot a flicker in a light even if it lasts for just 25 milliseconds. Our other senses react at different speeds, though. Hearing is much faster, with a time resolution of just three milliseconds, but touch can only manage 50 milliseconds. Smell and taste are the slowest and can take more than a second to react to a new sensation.