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Why Washington and Baltimore are different colors from space
Why Washington and Baltimore are different colors from space
PHOTOGRAPHY By DW Rowlands (Contributor) September 21, 2020
A view of the Washington (left) and Baltimore (right) regions from space. by NASA / International Space Station Expedition 63 Crew licensed under Creative Commons.
On July 15, the crew of the International Space Station posted a nighttime photo of our region from space on Twitter, likening Washington and Baltimore to “two galaxies swirling near each other.” This photo gives us the opportunity to make a number of observations about the region.
DC and Baltimore City are different colors at night
The first thing that stands out when one looks at the ISS crew’s photo nighttime lighting in our region is that the Washington region looks orange while the Baltimore region looks white. If they actually were galaxies, this would imply that Washington was significantly older and made up of mature stars fusing helium instead of hydrogen, or else that it was significantly further away and retreating at a high velocity. What is actually going on, however, is something more mundane: a difference in the District’s and Baltimore City’s street lighting choices.
Baltimore recently completed a program, called Bmore Bright, to replace all of the city’s street lights with modern LED street lights, which are more energy efficient and have longer lifespans than the various types of high-energy discharge lamps that have historically been used for street lighting.
While the District is currently in the planning phases of a similar project, only 5% of the street lights in DC are currently LEDs, while 86% are high-pressure sodium high-energy discharge lamps. While LED street lights are designed to replicate the color distribution of sunlight, and so appear white, high-pressure sodium lamps have a distinctly orange glow, giving the District its orange appearance in the photo.
The District’s consistent use of high-pressure sodium lamps also helps the DC-Maryland border stand out fairly clearly in the map: the close-in Maryland suburbs are lit with a variety of types of street lights, unlike the District’s consistent orange glow. Likewise, in Baltimore, the Seagirt Marine Terminal and Mid-Atlantic Terminal port facilities stand out because their orange sodium-lamp illumination contrasts sharply with the city’s white LED streetlights.
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PHOTOGRAPHY By DW Rowlands (Contributor) September 21, 2020
A view of the Washington (left) and Baltimore (right) regions from space. by NASA / International Space Station Expedition 63 Crew licensed under Creative Commons.
On July 15, the crew of the International Space Station posted a nighttime photo of our region from space on Twitter, likening Washington and Baltimore to “two galaxies swirling near each other.” This photo gives us the opportunity to make a number of observations about the region.
DC and Baltimore City are different colors at night
The first thing that stands out when one looks at the ISS crew’s photo nighttime lighting in our region is that the Washington region looks orange while the Baltimore region looks white. If they actually were galaxies, this would imply that Washington was significantly older and made up of mature stars fusing helium instead of hydrogen, or else that it was significantly further away and retreating at a high velocity. What is actually going on, however, is something more mundane: a difference in the District’s and Baltimore City’s street lighting choices.
Baltimore recently completed a program, called Bmore Bright, to replace all of the city’s street lights with modern LED street lights, which are more energy efficient and have longer lifespans than the various types of high-energy discharge lamps that have historically been used for street lighting.
While the District is currently in the planning phases of a similar project, only 5% of the street lights in DC are currently LEDs, while 86% are high-pressure sodium high-energy discharge lamps. While LED street lights are designed to replicate the color distribution of sunlight, and so appear white, high-pressure sodium lamps have a distinctly orange glow, giving the District its orange appearance in the photo.
The District’s consistent use of high-pressure sodium lamps also helps the DC-Maryland border stand out fairly clearly in the map: the close-in Maryland suburbs are lit with a variety of types of street lights, unlike the District’s consistent orange glow. Likewise, in Baltimore, the Seagirt Marine Terminal and Mid-Atlantic Terminal port facilities stand out because their orange sodium-lamp illumination contrasts sharply with the city’s white LED streetlights.
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