# Quantum fluctuations and momentum

1. Nov 21, 2011

### e2m2a

The Lamb shift showed that quantum fluctuations could have a real, measurable effect on the orbits of electrons. Since these fluctuations can impact the momentum of mass, is it possible that quantum fluctuations could impact electro-magnetic momentum, such as the momentum of photons?

For example, given a cubic volume of space, suppose a photon has an initial momentum h/λ (initial) as it enters perpendicular to the plane of one face of the cubic space. If the photon travels through the space, statistically the electron should have a certain number of collisions with the quantum virtual particles within this space before it reaches the opposite face, and would this not decrease the initial momentum of the photon, such that h/λ (final) < h/λ (initial)?

2. Nov 21, 2011

### Bill_K

The Lamb Shift is due to several effects, but mostly it's the effect that vacuum fluctuations have on the photons in the Coulomb field. Not the electron, as you seem to be saying. the energy level of the electron changes because it moves in a modified Coulomb field.

Also you seem to be picturing the photon's interaction as a series of billiard ball collisions that would tend to decrease its momentum. This of course is not so. The interactions are just as likely to increase its momentum as decrease it, and in fact they will average out.