All photosynthetic organisms contain a light gathering antenna, which absorbs photons and passes excitation energy to a reaction center complex, which carries out electron transfer reactions to convert electronic excitation energy into chemical energy. The antenna complexes are extremely diverse and permit photosynthetic organisms to live in remarkably different environments, including deep-sea hydrothermal vents. These organisms live off the ultraweak geothermal black body radiation given off by the hot vent. The use of the “red edge” effect as a possible means of life detection on extrasolar planets and the prospects for photosynthetic life on other worlds will also be discussed.