Space and time must be grainy, not smooth. Otherwise high-energy particles produced in astrophysical processes would not be detectable on Earth.

Physicists suspect that at distances trillions of times smaller than the width of an atom space is not like a smooth sheet. At this scale, they think it is more like a chessboard, with objects disappearing from one square and reappearing in another.

Ditto time. For durations of about 5x10-44 seconds, events are thought to happen in a series of freeze-frames.