Description As anyone who has stood in a hardware store knows, light bulbs come in a wide range of types and colors. Incandescent bulbs have a warm glow similar to sunlight, while more energy efficient gas-discharge bulbs come in a variety of shades. Some of the differences in artificial lighting are visible in photographs taken by astronauts aboard the International Space Station. For instance, several distinct colors of electric light are visible in this image of the Tsushima Strait, the shallow body of water that separates southern Japan and South Korea. A member of the Expedition 37 crew took this photograph on October 11, 2013. A cluster of fishing boats is the source of the bluish light near the center of the image. The fisherman are likely luring Todarodes pacificus—a species known as the Japanese flying squid—to the surface with bright xenon bulbs. The city lights on the Korean side of the strait tend to have an orange glow, while those on the Japanese side are greener. The difference is related to the distribution of mercury vapor, metal halide, and high-pressure sodium lamps—the bulb types most often used for street and outdoor lightning. Mercury vapor lights tend to be green, high-pressure sodium is orange, and metal-halide lamps are bright white. Image # ISS037-E-12066