Aurispector writes in with news that the Yale team that recently discovered an attractive force between two light beams in waveguides has now found a corresponding repulsive force. "'This completes the picture,' [team lead Hong] Tang said. 'We've shown that this is indeed a bipolar light force with both an attractive and repulsive component.' The attractive and repulsive light forces Tang's team discovered are separate from the force created by light's radiation pressure, which pushes against an object as light shines on it. Instead, they push out or pull in sideways from the direction the light travels. Previously, the engineers used the attractive force they discovered to move components on the silicon chip in one direction, such as pulling on a nanoscale switch to open it, but were unable to push it in the opposite direction. Using both forces means they can now have complete control and can manipulate components in both directions. 'We've demonstrated that these are tunable forces we can engineer,' Tang said."