Emma Gao

Light pollution mutes the sky over Los Angeles. “When you have city artificial lighting in the area, it brightens the night sky, just like the sun brightens the sky and turns it into day,” astronomy teacher Dr. Eric Nelson said.

Far above the Earth we inhabit lies an infinite abyss, scattered with universes undiscovered and galaxies unexplored. Through our night sky, we capture a fleeting glimpse of this world sublime, a window into the secrets hidden within the inky darkness of space. But from down below, peering up into this celestial looking glass, something seems amiss. As we gaze upwards, we can’t help but wonder –– where have all the stars gone?

For the past several decades, the visibility of stars in the night sky has slowly waned, a byproduct of the phenomena dubbed light pollution. Light pollution describes the artificial brightness of our night sky, caused by increased human lighting in particularly urban areas. With diminished contrast between light and dark, spatial features like stars become much harder to spot. A recent report shows that there is a 9.6 percent increase in sky brightness every year.

“When you have city artificial lighting in the area, it brightens the night sky, just like the sun brightens the sky and turns it into day,” astronomy teacher Dr. Eric Nelson said. “Same thing with city lights. So if you’re in somewhere like Los Angeles, you can see two or three of the brightest stars and you can see the moon and the planets and that’s about it. You’re not going to pick up anything else.”

In urban centers especially, the prevalence of artificial lighting like LEDs and advertisements washes away any stars in the night sky, drowned out by the brighter lights down below. Paired with environmental factors like cloud patterns and the time of year, light pollution can render certain areas void of any stars. Student astronomy researcher Kaitlyn Wang (12) emphasized the prevalence of light pollution in cities.

“It really depends on the type of day and the cloudiness,” Kaitlyn said. “Clear nights [are] getting more rare, and it’s really sad. The stars disappearing is an effect that happens around the cities because of the light pollution and clouds as well.”

Beyond just the visual impact of stars being erased from the night sky, light pollution also impacts the scientific community at large. For astronomers, the added light can disrupt finer instruments, preventing clear images of celestial bodies. Such a crucial part of their scientific process being hampered has resulted in a shift to viewing from more remote observatories and advanced telescopes, which are inaccessible to some astronomers.

“We just can’t see as deeply into the sky unless we get out of the atmosphere,” Dr. Nelson said. “A lot of ground based telescopes are becoming more and more handicapped, which means that their value gets reduced. And the science that comes out of them is thinning as a result. So it’s getting more and more difficult to actually do night sky observation.”

Even for non-astronomers, light pollution affects life as a whole. For humans, an increased amount of light at night can disrupt sleeping patterns, hindering the production of melatonin. For other species that rely on light, the influx of artificial brightness can also impact behavior and sleep.

“Light pollution causes a humongous amount of issues for some birds that are very sensitive to it and some animals that rely on day night cycles,” physical sciences club president Arnav Swaroop (12) said.

Certain sea turtle populations that rely on moonlight to guide their young have declined in recent years, with the light pollution caused by major coastal cities playing a huge factor. Other species that follow a nocturnal cycle are also affected, like seabirds and frogs, with increased lighting decreasing the contrast between night and day.

As cities expand and urban development takes on new heights, it may seem as if light pollution is an unsolvable problem. However, there’s also cause for hope. Unlike climate change and other environmental issues, light pollution has no permanent consequences. That is, if all human lights were to disappear, all would be resolved with no lasting side effects.

While light pollution remains a large-scale issue, there are many practical solutions that individuals can implement in their own lives, with the simplest being turning off lights when they’re not in-use. Additional steps include replacing LEDs with lights that do emit as much blue light, installing dimmers on light bulbs and closing blinds and windows at night to prevent excess light from going into the atmosphere.

“If you’re interested in not seeing an extinction event, then the impact goes up,” Dr. Nelson said. “The folks and creatures that are affected by light pollution can be affected dramatically. And just because it doesn’t impact you, doesn’t mean that it’s not something that needs to be considered as a serious long term problem.”

Stars emerge over San Jose during the power outage that lasted from Feb. 4 to Feb. 5. (Emma Gao)

How do we reduce light pollution?

• Only keeping lights on when necessary reduces the amount of light emitted into the environment, which minimizes contribution to ambient light.
• Substituting LEDs with alternative lights that emit warmer tones reduces blue light emission, which is a large contributor to light pollution.
• Closing blinds and windows contains indoor light.

By implementing these changes, everyone can play a part in preserving the natural darkness of the night sky as well as the effects of artificial light on ecosystems and human well-being.