The speed of light in a vacuum provides a convenient universal relationship between distance and time, so in physics (particularly in quantum physics) and often in chemistry, a jiffy is defined as the time taken for light to travel some specified distance.
The speed of light in a vacuum provides a convenient universal relationship between distance and time. A jiffy is defined as the time. This was in physics (particularly in quantum physics) and often in chemistry. This time is taken for light. This was to travel some specified distance.