Star Trek-style tractor beams may be possible

Science : Four separate groups of physicists have independently arrived at similar ideas for a tractor beam. Each method uses a Bessel beam, a special type of laser beam made of overlapping light waves that all travel at an angle relative to the direction of the beam. Light beams exert a forward push on objects; a Bessel beam exerts less than usual. To overcome the small push that Bessel beams still exert, the material properties of the object to be moved and the polarization and synchronization of the individual light waves within the beam are adjusted so that the object re-radiates more light forward along the beam, rather than back toward its source. The radiated light acts as a reverse thruster more powerful than the weak forward push of the Bessel beam. The resulting pull would only be powerful enough to move something the size of a grain of salt, however, not a spaceship. It would be powerful enough to manipulate biological specimens at the cellular level, for example.