All Screwed Up; November 2003; Scientific American Magazine; by George Musser; 2 Page(s)

You'd think we'd have figured out light by now. Kids learn about prisms and lenses in elementary school, people wear Maxwell's equations on T-shirts, and the quantum version of those equations is the most precise theory in science. Yet knotted up within the theory is a phenomenon that physicists are still unraveling: an unexplored property of light.

In addition to color (which depends on the wavelength of the electromagnetic wave) and polarization (the orientation of the wave), light beams can also possess orbital angular momentum (the shape of the wave fronts). Optics researchers discovered this property a decade ago, but for some reason this realization has failed to propagate much beyond a small community of specialists [see "Hands of Light," Innovations, Scientific American, August]. It has barely been noticed even by those with the greatest need to exploit every conceivable aspect of light-namely, astronomers.