According to Heisenberg's Uncertainty principleIn words this means that the uncertainty in energy of a state or particle times the uncertainty in greater than
This means that ifwe cannot tell the energy apart from zero, or alternatively that the principle of conservation of energy is not violated as long as the sum of all the particles of that exist for a timeis less thanIn fact space is seething with these 'virtual particles' that come into existence for a short time and then disappear. The particles are created as sets of particle – antiparticle pairs. Each particle has the same mass and energy but opposite charge as it's antiparticle. Suppose a particle has a massthen it has energybecause of it's mass. The total mass energy of the particle antiparticle pair isSo that conservation of energy is not violated we must have the lifetime of the particlesThis means that the larger the mass the shorter the lifetime of the particles. The speed of a particle can be at most c, so by extension the range of the particles is limited to a distance
Virtual particles have real physical effects. The force particles that mediate the physical forces are virtual particles. Some forces are associated with force particles that have zero mass, hence infinite lifetime and infinite range – gravity and the electromagnetic force - and some forces are associated with force particles that have mass and so have lifetimes and by extension ranges that are limited by Heisenberg's Uncertainty principle. The exchange of a virtual photon between two electrons resulting in repulsion is illustrated below.