Chapter 9: Fundamental Physics

Section 8: The Relationship of Space and Time

Discreteness in time

In present-day physics, time, like space, is always assumed to be perfectly continuous. But experiments—the most direct of which are based on looking for quantization in the measured decay times of very short-lived particles—have only demonstrated continuity on scales longer than about 10^-26 seconds, and there is nothing to say that on shorter scales time is not in fact discrete. (The possibility of a discrete quantum of time was briefly discussed in the 1920s when quantum mechanics was first being developed.)

From Stephen Wolfram: A New Kind of Science [citation]