Light Pollution, part I
"In most cities the sky looks as though it has been emptied of stars, leaving behind a vacant haze that mirrors our fear of the dark and resembles the urban glow of dystopian science fiction." —Verlyn Klinkenborg, Our Vanishing Night
The night sky filled with stars is a true wonder. This stunning spectacle has much to teach us about our species as it's accompanied our evolution for centuries, serving as inspiration for literature, the arts, guidance, and science advancement.
But in all probability, today's generations will sadly be negated the chance to witness the expanse above us brimming with billions of stars, all because "light pollution" is skyrocketing.
Children may never experience the thrilling awe and fascination that derives from the observation of the myriad of astral objects that inhabit our celestial vault, and hence we risk losing our collective memory of this heritage that's been with since time immemorial.
The below images serve to illustrate what we and our children are losing out because of this phenomenon:
Read under the cut!
What is "Light" Pollution?
The excessive and needless artificial lighting that leaks into the atmosphere is referred to as light pollution. One's ability to observe the night stars is greatly diminished by this, and nocturnal creatures suffer significant harm as a result.
Typically, two types are defined, depending on the wavelength of the photons emitted:
Light pollution is found in the visible spectrum and is caused by photons in the optical wavelength (wavelengths comprised between 400 nm and 700 nm)
Radio spectrum pollution, due to photons emitted in radio wavelengths (frequency between 0 and 300 GHz, i.e. with a wavelength greater than 1 mm)
Both constitute issues for astronomical observation, though "light pollution" is more noticeable since, well, we can physically see it in our day to day lives.
From Revolution to Pollutant
Even though this kind of pollution can occur during the day, the contrast of nighttime darkness amplifies its affects. According to estimates, skyglow affects 23 percent of the planet's surface area and 83 percent of the world's population lives in light-polluted areas.
Light pollution, a significant urbanisation-related adverse impact, is held responsible for deteriorating ecosystems, endangering human health, and degrading aesthetic settings.
Between 1992 and 2017, it grew by at least 49% globally.
[Sources: NIH:The new world atlas of artificial night sky brightness by Fabio Falchi et al ; MPPDI: "First Estimation of Global Trends in Nocturnal Power Emissions Reveals Acceleration of Light Pollution" ]
Here's a comparison of how light pollution has affected India through the years:
[Sources: NIH:The new world atlas of artificial night sky brightness by Fabio Falchi et al ; MPPDI: "First Estimation of Global Trends in Nocturnal Power Emissions Reveals Acceleration of Light Pollution" ].
What is "Light Pollution"?
The excessive and needless artificial lighting that leaks into the atmosphere is referred to as light pollution. One's ability to observe the night stars is greatly diminished by this, and nocturnal creatures suffer significant harm as a result.
How can we measure Light Pollution? The Bortle Scale
This scale serves as a method for assessing the degree of light pollution in a specific region: basically, it measures the disturbance from light pollution as well as the astronomical observability of celestial objects.
There are nine different levels of light pollution, with Class 1 being an excellent dark-sky location and Class 9 being an inner city sky - below is an image taken from Stellarium to give you an idea of what we're talking about:
Drivers of Light Pollution:
When analysing this phenomenon, there's two main players driving this rift between clear night skies and light pollution disturbances:
the lighting systems in cities
the constellations of private satellites in low orbit, such as the Starlink system (this also concerns radio spectrum pollution).
On the one hand, the excessive emission of light from an increasing number of artificial sources is making astronomical observations from the ground progressively more difficult or even impossible in many parts of the world. And the areas of our planet that display a heavy output of artificial light at night are expanding.
On the other hand, the growth in the number of satellites in low orbit greatly increases the "brightness" of the observable sky and this in turn disturbs astronomical observations, both from the ground and, sometimes, even from space as recently witnessed by the Hubble Space Telescope.
The concentration of photons produced by man in the atmosphere, and artificial light at night (or artificial light at night, hence the acronym ALAN) are to be considered an environmental pollutant to all effects: as they fully fall within the definition of "anthropogenic pollutant" given by the United Nations in 1979 and as such must be regulated.
And it's not just a matter of terminology: various scientific articles on the biological and physiological consequences of light pollution on human and animal behaviour, and therefore on the quality of life, underline many problematic issues.
Effects on Wildlife:
Anywhere that human light seeps into the natural world, an element of an animal's life—their migration, their breeding, their ability to seek and eat—is impacted.
One of ecology's hottest subjects right now is artificial nighttime lighting, which is the subject of a study explosion targeted at identifying and measuring its ecological impacts. Nearly every week brings new information about how the wrong kind of light in the wrong location at the wrong time is impacting species, including microbes, moths, and mammals, on land, in waterways, and at sea. This is made possible by methodical long-term field studies, remote tracking, and manipulative tests.
A well studied instance of this that has been the subject of the most research involves marine turtles:
Sunlight reflected off the ocean was the brightest object on the beaches for hundreds of years before humans learned to "control" and fend off darkness - sea turtle hatchlings intuitively know to move toward the brightest source of light. But because coastal towns saturate the night with their bright lights, the hatchlings lose their their sense of direction and travel toward the cities rather than the sea, where they perish from dehydration or end up in being preyed upon, without ever making it to the protection of the ocean. Every year, Florida alone experiences hundreds of thousands of hatching deaths because of light pollution. [source: The City Dark. Dir. Ian Cheney. Perf. Ian Cheney. Wicked Delicate Films, 2012. DVD]
So while humankind has reaped significant advantages from the use of artificial, the downside is that it has altered signals for the timing cues of many biological activities. It has also disrupted the normal daily, seasonal, and lunar light patterns as experienced by a variety of species.
After all, life developed in the presence of the daily rising and lowering of the sun, the monthly waxing and waning of the moon, and the seasonal variations in day duration. These cycles serve as the most significant signals for many actions and biological processes because they are the most predictable fluctuations in the natural world.
The Issue with modern LEDs:
The change to bright, white LED streetlights is altering the colour of the night, thanks to industrialisation and the creation of LED illumination. Low-pressure sodium lights produce clear orange light, while older high-pressure sodium lights primarily release yellow light. LEDs, on the other hand, produce a wide variety of wavelengths, with a striking peak in the blue spectrum.
Blue light is the most harmful to wildlife, and the wider the spectrum, the greater the effect on different species. Additionally, blue light is more powerfully diffracted, enhancing the brightness of the faint, diffuse light pollution known as sky glow. [source: J.Bennie et al / Journal of ecology, 2016]
What's the impact on astronomic observation?
Astronomers are well aware of the bad effects of the ALAN, the rise in background radiation that makes it more or less difficult to conduct astronomical study by utilising the maximum potential of their telescope, based on its severity.
If they had previously solved the problem by constructing new telescopes farther and further away from cities, due to the rise in light pollution, there are now essentially no more remote locations on Earth that simultaneously meet all the requirements for the installation of an observatory (i.e., the absence of light pollution, a significant number of clear nights, etc)
The problem, however, is not limited to awareness and inaction. Legislation – or rather, the lack of adequate legislation – also plays a primary role. There is currently a complete lack of coordinated regulation and supervision at a global level, a lack of clear international protocols for the management of orbital traffic and minimum standards have not been defined for the environmental impact of satellites and light pollution in general.
"We are left with the growing unease of witnessing the inevitability, in slow motion, of an avoidable disaster in low Earth orbit," writes Aparna Venkatesan, professor of physics and astronomy at the University of San Francisco and member of the committee on pollution, in his editorial.
The regulation of space as a human setting is still implicit.
Inexorably fewer nights and hours per night are available for true astronomical exploration, and if action isn't taken to address this, light pollution and satellite constellation contamination of the observable night sky will become predominant: we risk entering a period of possibly irreparable harm in low Earth orbit without actively applying the precautionary principle to orbital space because of the general balance of excess pollution.
Dr.Falchi and coworkers warn that if the current course of events is not changed, "soon looking up at the sky you will see tens, hundreds, thousands of satellites crossing the vault at any moment and no human will be able to admire the night sky as it has always been possible to do."
However, even if work could be done to make the satellites less apparent to the naked eye, a telescopes' lens would is far sharper and has greater resolution, meaning that a lot of other issues would still remain unresolved, such as : increased sky backdrop brightness, air pollution from launch exhaust and detritus, and orbital traffic.
«Since it is not too late to stop all this, we scientists and first of all citizens should take action to stop this attack (from above with satellites and from below with ALAN) on the natural night and on the intangible cultural heritage of the starry skies» , says Dr.Falchi at the end of his commentary article. [Source: Media INAF, editoriale online]
It's time to think about outlawing mega-constellation launches and urging a sharp decline in light pollution caused by the ALAN. Undoubtedly, the world requires a "new deal" for the evening.
