A question on energy I was pleased to see the GreenLight article “Making energy personal” (October, p. 35) on photocatalytic water conversion. In my opinion, this is the only long-term solution to our energy problems. Of course, this subject has been researched for years, primarily with TiO2 and similar photocatalysts. MIT professor Daniel G. Nocera is performing very valuable work in this field. However, one sentence in the article – “A catalyst for hydrogen gas existed previously” – made it sound as if he produced oxygen from water only. If chemistry has not changed, water is composed of both hydrogen and oxygen. If you remove oxygen, what happens to the hydrogen? If the process is truly catalytic, the hydrogen must go somewhere. It is not used up in the reaction. The ultimate goal is to split water with photons (sunlight), using a catalyst that is stable and robust. The products are hydrogen and oxygen, which, when separated, can be used in fuel cells. Vernon Porter, PhD Murphy, Texas Photonics to the rescue I received the October issue of Photonics Spectra and was immediately impressed with it and its contents. I was especially interested in the editorial, “Things are looking up.” In it, Federal Reserve Chairman Ben Bernanke is reported to have said that we have turned a corner on the recession and that it is time to prepare for the recovery. Your comments reflect an attitude appropriate to this industry and are welcomed by all. As you know, work continues in all areas of quantum physics as industry races to develop ultraefficient solar power, and next-generation nuclear power, waste harvesting and other technologies that will turn America once and for all into an energy-independent nation. We are currently in a paradigm shift in terms of our thinking about our future energy-needy economy and how best to satisfy its growing demands. I’m aware of ambitious plans such as capturing the energy of lightning. Perhaps most esoteric of all is so-called “spherical pinch” geometry, which will allow high-energy lasers to fuse light hydrogen nuclei in the world’s first cryogenic laser-pumped fusion experiment. The discovery of light led humanity out of darkness eons ago. Now, light will lead us to a new age. Keep up the good work. Joseph V. Marsh Ararat, N.C. Errata A paragraph in the article by Boston Micromachines Corp., titled “Adaptive Optics in Biological Imaging with Two-Photon Microscopy” (December 2009, p. 42), was edited to imply that Dr. Michelle Day has employed adaptive optics (AO) in her work. The sentences should have read: “With the addition of AO, calibration issues would be significantly reduced, increasing the availability of the instrument. By implementing AO, the need for expertise in calibrating the instrument on a regular basis also would be reduced, leading to a lower cost of operation.” In “The Search for Other Earths” (October, p. 40), the Keck telescope image of the HR 8799 planetary system was attributed incorrectly. The image was provided courtesy of Christian Marois (Herzberg Institute of Astrophysics), Bruce Macintosh (Lawrence Livermore National Laboratory) and the W.M. Keck Observatory. Clarification An acknowledgment of assistance was missing from the article “The Search for Other Earths” in the October 2009 issue: Optical Research Associates (ORA) gratefully acknowledges the assistance of Dr. Wesley Traub and Michael Devirian of the Jet Propulsion Laboratory in Pasadena, Calif., whose expertise and insight were invaluable during research for this article. ORA also would like to acknowledge David W. Kuntz of Technical Marketing Services in Rancho Palos Verdes, Calif., for his contributions.