Instant

In physics and the philosophy of science, instant refers to an infinitesimal interval in time, whose passage is instantaneous. In ordinary speech, an instant has been defined as "a point or very short space of time," a notion deriving from its etymological source, the Latin verb instare, from in- + stare ('to stand'), meaning 'to stand upon or near.'^[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]

As of October 2020^[update], the smallest time interval certified in regulated measurements is on the order of 397 zeptoseconds (397 × 10⁻²¹ seconds).^[3]

18th and 19th century usage

Instant (usually abbreviated in print to inst.) can be used to indicate "Of the current month". For example, "the 11th inst." means the 11th day of the current month, whether that date is in the past, or the future, from the date of publication.^[4][5][6]

See also

• Infinitesimal
• Planck time
• Present