Summary:
Christmas lights are helping scientists understand how cities light up at night.

Full article:
(CNN) -- Those lights you put up for the holidays don't just brighten your neighborhood -- they are providing NASA with new data about how cities illuminate the night. Just how much brightness do the traditional Christmas lights add across the United States? Between the day after Thanksgiving and New Year's Day, nighttime lights in many major U.S. cities shine 20% to 50% brighter than average, according to NASA. The data comes from satellite imagery -- from the NOAA/NASA Suomi National Polar-orbiting Partnership satellite -- and the use of an algorithm to account for other sources of light. The NASA team examined light output in 2012 and 2013 in 70 cities during a study of urban energy use. The increased brightness is more pronounced in suburban areas, according to NASA. "In most suburbs and outskirts of major cities, light intensity increased by 30 (percent) to 50 percent," NASA said in a statement. "Lights in the central urban areas did not increase as much as in the suburbs, but still brightened by 20 (percent) to 30 percent." The changes in brightness during the holidays is not unique to the United States. The researchers also found that cities in the Middle East are brightened during the holy month of Ramadan. Light use in Saudi Arabian cities increased by 60% to 100% during Ramadan, NASA reported. Cairo also shone brighter. Best places to see Christmas lights in the U.S.