The Hidden Lights Of
By Tristan Ashton
Y
ou’re out in the country on a warm and moonless night, far from any cities or lights. It’s just you and your dog as the clock ticks slowly towards midnight. It should be absolutely dark…but you see shadows! A soft light permeates the air, casting the trees in ghostly silhouettes—a light whose only source is the Milky Way itself. It seems improbable that the Milky Way, a tight but nebulous band of starlight, could cast visible shadows. And yet in the most remote regions of the world, such as the center of Death Valley or far out in the Pacific Ocean, it becomes a nightly occurrence. How can you possibly measure the stark difference between the Milky Way’s 22
March 2020
soft illuminations with the glowing nightlife of inner cities? El Morro National Monument, with its recent certification as an International Dark Sky Park (IDSP), provides an answer. The Bortle Scale is a measurement created in 2001 to help evaluate the quality of a night sky. In the complete absence of artificial light, the scale bottoms out at a “1,” indicating the darkest skies theoretically possible. In such a site, the glow of the Milky Way casts visible shadows on the ground and the brightest stars can actually impair your night vision! Progressing up the scale to “4” and “5,” the Milky Way is barely detectable, and the number of visible stars drops markedly from several thousand to just a few hundred. Light domes from nearby cities become
