Virtual Particles
Transient quantum field fluctuations that mediate interactions between real particles, constrained in lifetime by the energy-time uncertainty principle.
Governing formula
ΔE Δt ≥ ℏ / 2, q² ≠ m² c² (Off mass-shell)
SI unit
Transient Quantum Fluctuation
In depth
Virtual particles do not obey the relativistic energy-momentum relation (off mass-shell). They exist temporarily during interaction vertices in Feynman diagrams, transferring momentum and quantum numbers between real particles.
Examples in the real world
Virtual photon exchange mediating electrostatic repulsion between two colliding electrons.