On Oct. 1 this year – a rare, almost cloud-free night across the continental United States – NASA snapped a series of natural light photos of the country with the Suomi-NPP satellite. The satellite orbits 512 miles (824 km) high in a polar orbit and is named for the late Verner Suomi, a pioneer in satellite meteorology.
Suomi-NPP satellite views showing Earth at night – narrated
Unlike many communications satellites, which orbit around Earth’s equator, Suomi-NPP circles the planet from pole to pole. As Earth rotates beneath it, the satellite sees a different slice of the planet each orbit. Over time, all the slices add up to give Suomi a complete picture of the Earth below.
That night, not only was it mostly clear across the U.S. but the moon was three days before new. The little bit of light it cast was not enough to illuminated the ground or atmosphere, allowing for good contrast between lights and landscape.
Cities large and small stand out while highways festoon the darkness like strings of holiday lights. I’m always intrigued by the latest images of Earth at night because they let us gauge how bright our planet is becoming. One of the most appalling examples of recent light pollution comes from oil drilling and exploration in the Bakken formation in western North Dakota. A dozen years ago it was one of the darkest places on the planet. Now lights spread across more than a 100 miles (160 km) of high prairie.
You may have noticed a change in lighting type in your own city. Most roads and byways are illuminated by pink-orange high pressure sodium lights. They work well when boxed in shielded housings that focus the light downward onto the streets where it’s needed. Unfortunately, many sodium lights are unshielded, sending light sideways and upward. Light in those directions not only creates unwanted glare but seriously brightens the night sky, robbing many of the joy of stargazing.
Recently, much more energy-efficient LED (light-emitting diode) lights are now being packaged in ornamental as well as standard streetlighting. I’ve seen the change in my own city of Duluth, Minn. While these lights have tremendous energy benefits, they are INTENSELY bright, much more so than the “old-fashioned” sodiums.
As long as they’re shielded, light spill and glare are relatively well-controlled (though light reflected off snow becomes a bigger problem), but I’m concerned that low-cost LEDs will proliferate in ornamental and building and parking lot illumination. Much of that lighting is unshielded and heavy on glare, making driving at night more difficult and preserving what dark sky is left more challenging.
I encourage you to learn all you can about the new lighting and work with you local city councils and town boards to explain how LED lighting can be used wisely to make everyone happy – stargazers, drivers and those who walk at night. For help and more information, drop by the International Dark-Sky Association website.