Instant, moment, minute, second, flash, jiffy, twinkling, split second are comparable when they mean a particular point of time or a stretch of time of almost imperceptible duration.
Instant and moment are often used interchangeably, but instant carries so much stronger a suggestion of infinitely small duration that it is better fitted than moment for contexts that imply urgency, extreme transiency, or inconceivable swiftness,
Moment, on the other hand, is particularly serviceable when the word or the context carries the implication of a definitely apprehended, even though extremely brief, point of time,
Minute and second technically apply to measured fractions of an hour, but in the present relation minute, even more than moment, suggests an appreciable though short duration of time, and second, quite as much as instant, suggests its imperceptible duration.
Flash suggests duration comparable to that of a flash of lightning; the term is therefore often used when incredible speed in movement, action, or thought is implied.
Jiffy is found chiefly in the phrase in a jiffy , equivalent to very quickly or directly.
Twinkling, often with an added “of the eye,” suggests the quickness of a wink or blink.
Split second, basically denoting a fractional part of a second, heightens the implication of brevity as expressed by second.