It’s not just your neighbours and people around you who can see your Christmas lights. It has been proven that the combined effect of holiday lights in cities as well as suburbs is so powerful that the difference from normal lighting conditions can be detected even from space. From The Huffington Post:
NASA reports that satellite images show certain cities shine between 20 percent and 30 percent brighter during the holiday season. And out in the suburbs, some areas shine as much as 50 percent brighter.
“It’s a near ubiquitous signal. Despite being ethnically and religiously diverse, we found that the U.S. experiences a holiday increase that is present across most urban communities,” Miguel Roman, a research physical scientist at NASA Goddard and one of the leaders of the study, said in a news release. “These lighting patterns are tracking a national shared tradition.”
In the above map, the green dots represent areas where lights are up to 50 percent brighter in December. “Overall, we see less light increases in the dense urban centers, compared to the suburbs and small towns where you have more yard space and single-family homes,” Eleanor Stokes, a NASA Jenkins Graduate Fellow and co-leader of the study, said in the news release.
The measurements were taken by the NOAA/NASA Suomi National Polar-orbiting Partnership (Suomi NPP) satellite over three years. The effect isn’t limited to the U.S. during Christmas. In fact, the researchers first noticed the difference in light levels in images of Cairo taken during the Muslim holiday of Ramadan.