In physics and the philosophy of science, instant refers to an infinitesimal interval in time, whose passage is instantaneous.
'[1] The continuous nature of time and its infinite divisibility was addressed by Aristotle in his Physics, where he wrote on Zeno's paradoxes.
The philosopher and mathematician Bertrand Russell was still seeking to define the exact nature of an instant thousands of years later.
[2] In 2024, John William Stafford used algorithms to demonstrate that a time difference of zero could theoretically continue to expand (in various ways) to infinity, and subsequently described a new concept that he referred to as instantaneous.
As of October 2020[update], the smallest time interval certified in regulated measurements is on the order of 397 zeptoseconds (397 × 10−21 seconds).