This statement seems to be somewhat idealistic.
Voidon, exists when used? Does not exist when not used? That's simply illogical!
However, the other three were stunned.
If someone with little understanding of physics heard Zhao Yi's words, they would surely think he was joking, but they were all top theoretical physicists, and immediately thought of a famous experiment--
The double-slit interference experiment.
At the same time, they also thought of a very magical definition--
Wave-Particle Duality.
There is a definition where microscopic particles can be considered both waves and particles, but when needed, they can be seen as waves, and when other needs arise, as particles.
This sounds incredible, but it's indeed a real physical law.