48Does Dark Energy Really Exist? By Timothy Clifton and Pedro G. FerreiraThe observations that led astronomers to deduce the existence of dark energy could have another explanation: our galaxy may lie at the center of a giant cosmic void.40Saving the Honeybee By Diana Cox-Foster and Dennis van EngelsdorpThe mysterious ailment called colony collapse disorder has wiped out large numbers of the bees that pollinate our crops. The causes turn out to be surprisingly complex, but solutions are emerging.56The Evolution of Primate Color Vision By Gerald H. Jacobs and Jeremy NathansAnalyses of primate visual pigments show that our color vision evolved in an unusual way and that the brain is more adaptable than generally thought.64The Post-Traumatic Stress Trap By David DobbsA growing number of experts assert that overdiagnosis of post-traumatic stress disorder may compound the suffering of soldiers who are actually afflicted with depression, brain trauma or other problems or who are simply taking time to adjust.70The Dawn of Miniature Green Lasers By Shuji Nakamura and Michael RiordanSemiconductors can generate laser light in all colors except one. But new techniques for growing laser diodes could soon make brilliant full-spectrum displays a reality.76Preventing the Next Pandemic By Nathan WolfeAn international network for monitoring the flow of viruses from animals to humans might help scientists head off global epidemics.