Physicists have proposed a new kind of force that acts between empty spaces. The effect has yet to be tested experimentally, but it is thought it may be felt on a molecular scale.
Aurel Bulgac, a scientist at the University of Washington in the United States, and Andreas Wirzba, at Forschungszentrum Julich, one of the Helmholtz research centres in Germany, outlined the theoretical work in the journal Physical Review Letters .
They believe the effect would be similar to the Casimir force. This is the slight attraction that is felt between two narrowly separated metallic plates in a vacuum. The Casimir force is driven by an imbalance in the fleeting electromagnetic fields that occur in the vacuum between the plates and in the space that lies beyond them. This gently pushes the plates together.
Bulgac and Wirzba's force involves two or more cavities separated by non-interacting particles, such as a sea of electrons. If the wavelengths associated with those electrons are comparable to the dimensions of the spaces, the new effect may come into play. As electron waves bounce back and forth between the cavities, they are either repelled or attracted.
The effect may be able to act over a longer range than the weakly attractive van der Waals force between molecules.