The idea that light can move matter is not new—Johannes Kepler suspected as much some 400 years ago when he noticed that the tails of comets always point away from the Sun. That suspicion was formalized in 1871 with James Clerk Maxwell’s prediction of radiation pressure—the force imparted on a body by refracted, reflected, or absorbed light—and confirmed in 1900, when Pyotr Lebedev observed the effect in experiments.
But it wasn’t until the 1970s that what is now the most widely recognizable application of optical forces came to fruition: the optical trap. Optical manipulation has since become a mainstay in science research; 1 it has been used to tug at strands of DNA (see Physics Today, January 2006, page 26), to grab aerosol particles, and to cool atoms to microkelvin temperatures (see the article by Claude Cohen-Tannoudji and William Phillips, Physics Today, October 1990, page 33))....
