Chapter 30 - Nuclear Reactions and Elementary Particles - Learning Path Questions and Exercises - Conceptual Questions - Page 1029: 15

Although the virtual exchange particles are unobservable by themselves, the forces created by them can be predicted. These predictions agree with experiment. So, their existence can be verified.

Although the virtual exchange particles are unobservable by themselves, the forces created by them can be predicted. These predictions agree with experiment. So, their existence can be verified.