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article imageWhy aliens would know its Christmas on Earth

By Stephen Morgan     Dec 19, 2014 in Lifestyle
When Christmas comes the world lights up, literally. Those decorations you've put on the house won't just brighten up the neighbourhood, but they could be sending a message to aliens that a festive season is underway.
NASA satellites having been tracking changes in how Earth looks from space when Xmas celebrations are in full swing. What they found is that a very visible change takes place in the luminosity of major population centres.
When you switch on those Xmas lights, the night time images of Earth brighten by up to 20 to 50 percent. After Black Friday and Thanksgiving in the US, the lights gradually increase peaking between Christmas and New Year.
The NASA website describes the findings of the Suomi NPP, a joint NASA/National Oceanic and Atmospheric Administration (NOAA) mission. Its satellites carry an instrument called the Visible Infrared Imaging Radiometer Suite (VIIRS), which can observe and detect the glow of lights in cities and towns worldwide.
Image of Christmas lights in Northern Europe
Image of Christmas lights in Northern Europe
An article in the Telegraph reports that scientists used computer programmes to filter out the effects of moonlight, clouds and air particles to focus on city lights and provide high-quality information on light output across the globe. The original intention of the mission was to determine patterns in urban energy use linked to greenhouse gas emissions.
The Huffington Post quotes Miguel Román, a research physical scientist at NASA Goddard and member of the Suomi NPP Land Discipline Team, who said the images help show how people make decisions with energy.
"More than 70 percent of greenhouse gas emissions come from urban areas, If we're going to reduce these emissions, then we'll have to do more than just use energy-efficient cars and appliances. We also need to understand how dominant social phenomena, the changing demographics of urban centers, and socio-cultural settings affect energy-use decisions."
However, what they also found was light intensity from population centres increased by up to 50 percent in urban areas, particularly the suburbs, but also in city centres by around 20 to 30 percent, in what might be called "the fairy lights factor."
Christmas lights in the Eastern US seen from space
Christmas lights in the Eastern US seen from space
NASA reports that they focused on the U.S. West Coast from San Francisco and Los Angeles and cities south of a rough imaginary line from St. Louis to Washington, D.C. They also investigated lighting patterns in 30 major towns in Puerto Rico, which is renowned for its night time festivities and because it has one of the longest Christmas holiday periods.
Christmas lights seen from space  Southern California
Christmas lights seen from space, Southern California
Eleanor Stokes, a NASA Jenkins Graduate Fellow and Ph.D. candidate at Yale University's School of Forestry and Environmental Studies, New Haven, Connecticut, explained that "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."
They also found that in countries like Egypt and the Gulf states lighting increased markedly during Ramadan, when fasting during day time means activities for eating and celebrating have to be moved to after sunset.
With regards to the effect in the US, NASA reported that despite the country's cultural diversity, the increases in lights seen from space in the Xmas period is massive.
NASA image of Christmas lights in NE USA
NASA image of Christmas lights in NE USA
"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," said Román. "These lighting patterns are tracking a national shared tradition."
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