The Babylonians thought it was the tail of their goddess Tiamat. The ancient Greeks believed it endowed Hercules with his godlike abilities. But it wasn’t until 1610, when Galileo used his telescope to take a closer look at the Milky Way that he discovered it was stars. All stars.
And now scientists say that our view of those stars is being washed out by human light sources that continue to brighten our skies.
Losing the 'Way'
An international group of scientists recently updated the World Atlas of Artificial Sky Brightness, which measures the amount of artificial light that reflects off the atmosphere back down onto Earth. High-resolution satellite data produced new maps of the world’s light pollution with 45 times more spatial resolution than before. A preliminary look at the new data reveals that one-third of humanity is now unable to see the Milky Way in the night sky. “We now have a couple generations of people that live in areas that are cut off from viewing of astronomical features," explains Dr. Chris Elvidge, a physical scientist at NOAA’s National Centers for Environmental Information and a member of the team that updated the atlas. “People no longer have that view and the connection that view gives them to the cosmos.”
Courtesy of the authors of The New World Atlas of Artificial Sky Brightness. Prepared with ArcGlobe software by Nataliya Rybnikova.
As cities expand to accommodate rising populations, their artificial light output increases as well. This obscures the night sky from astronomers, hindering their ability to study the stars. The additional artificial lighting also has adverse effects on wildlife. “Every year the research just keeps coming in and the number of different species that are affected by light pollution just keeps growing and growing” says Cheryl Ann Bishop, Communications Director for the International Dark-Sky Association (IDA). A moth fluttering around a light bulb as if stuck in a trance is a common enough occurrence but it’s also an example of how artificial lights can impact local ecosystems," explains Cheryl. Bats prey on moths and artificial lights have eased their hunt for food. The bats are drawn towards the light, away from their normal habitats, changing the local ecosystem.
Safety concerns are a leading cause of the increase in artificial lighting but research on its effectiveness is inconclusive. Humans have an instinctual fear of what is lurking in the dark and it’s one of the biggest challenges when convincing municipalities to address light pollution. “Good lighting will make you safer but that doesn’t mean more light,” explains Cheryl. The human eye is designed to accept light but saturating it with bright, improperly shielded lights actually makes it more difficult to see in the dark.
Ways to bring the lights down
Things aren’t all bad though. Lighting manufacturers are increasingly being asked to produce “dark sky friendly” products such as shielded residential light fixtures and directional flagpole lighting. The IDA approves these devices and promotes them to consumers. “We’re not anti-light … we’re not going to go backwards, but we want to make sure it’s done responsibly,” says Cheryl. The scientists involved in the study hope that this atlas will help bring awareness to the issue. “There’s ... a lot of other things happening in the world,” notes Dr. Elvidge. “It’s really good we are aware of it (light pollution) and maybe over time we can improve the situation.”
The Milky Way may be lost to many humans now but there are people working to bring it back for future generations.