Will Smart Lighting Bring Back Galileo's Night Sky?
In 1669, Galileo, the father of Modern Physics and Observational Astronomy, had trained a telescope on the night sky. During the subsequent year, 1670, he published his observations in a booklet (Sidereus Nunciu) Starry Messenger. In this booklet, he had described the fascinating worlds of the night sky, beautiful constellations, the milky way, and twinkling stars casting shadows on a moonless night. He had shown the world the power and magic of the night sky(nocturnal world), which enable humans to navigate the globe and explore the Moon.
Our universe is filled with light (radiant electromagnetic energy travelling in transverse waves at different wavelengths (360 nm- 760 nm)). Even on a moonless night, the earth is illuminated by the light from our galaxy's millions of stars. Space dust diffuses the sun's rays to create a distinct nighttime glow (zodiacal light). Thanks to the light scattering effect, particulate matter of the earth's atmosphere scatter all available photons to provide brightness enabling humans to perceive the surrounding. But the human can not do certain tasks in the moonlight or starlight, which can only be possible in sunlight. But human ingenuity had conquered the limitation of nature and discovered artificial light. The journey of modern artificial light has started with the invention of the incandescent bulb by Humphry Davy in the18th century. Today, artificial lighting has become an integral part of modern life, enabling humans to do all the previously only possible tasks during the sunlight.
But the advent of industrialization, rapid urbanization, and advances in artificial lighting technology from incandescent light to now white LED (Light-emitting diode) has altered the once Galileo's pristine night sky world. As the sun sets, artificial lighting starts brimming across the urban landscape in the indoor setting (residential, commercial, industrial) and an outdoor setting. In an outdoor setting (highways, parking areas, and sports complexes), lighting enhances public safety and security. Commercial buildings also use outdoor lighting in their billboard to advertise their products and services during the night. The root cause of light pollution is poor lighting practices and usage of short-wavelength white-blue light. Poorly targeted light trespass to the unintended area or escape into the sky, creating an urban sky glow over inhabited areas. Unshielded light creates excessive glare, which strict pupils and causes pedestrians and motorists' visual discomfort on highways. Excessive and inappropriately focussed lighting has adversely affected human health and accelerated the extinction of nocturnal animals, birds (migratory wetland birds, singing birds, and ocean birds), wetland amphibians (frog/toad), sea turtles, fishes (salmon), and flies.
The Cycles of light (sunlight) and darkness (moonlight/starlight) determines the circadian rhythm in humans. In response to the circadian rhythm, the human body produces melatonin hormone. Melatonin has antioxidant properties and induces sleep, boosts the immune system, lowers cholesterol, and ensures the proper functioning of the thyroid, pancreas, ovaries, testes, and adrenal glands. Nighttime exposure to artificial light can adversely affect circadian rhythm (biological clock) and suppress melatonin production, enhancing risks for obesity, depression, sleep disorders, diabetes, and breast cancer.
Apart from climate change and habitat loss, light pollution is one of the major reasons for the extinction of many bird species of the avian world. Excessive artificial light at night (ALAN) disrupts avian species' natural circadian rhythms and disturbs their predator-prey relationships, migration, and pattern habitat connectivity. It also decreases their ability to detect seasonality, causing them to migrate untimely and missing ideal climatic conditions for nesting and foraging. Often disoriented songbirds, wetland migrating birds (warblers, tanagers, vireos, and grosbeaks), and Seabirds (burrow-nesting petrels and shearwaters) met with a fatal collision with low-rise buildings, towers, skyscrapers, and structures near the seashore.
Artificial lighting near wetland can disrupt nocturnal activities (croaking as part of the breeding process) of wetland amphibians (such as frogs and toads), causing extinction. Sea turtles live in the ocean, hatch at night on the beach, and go back to the sea by detecting the ocean's bright horizon. But due to artificial lights, hatchlings draw away from the ocean. Some fish species such as salmon are susceptible to light pollution as ALAN affects their migratory behaviour and makes them vulnerable to predators. Many predators exploit the fatal attraction of nocturnal pollinators (such as Eastern fireflies and many moths species) to the artificial light, causing depletion of key food web species. It is now confirmed that the real culprit behind light pollution is poor outdoor lighting practices, and short-wavelength white-blue light (more than 3000k colour temperature) produced by an LED light. But unlike other pollution, light pollution can be reversed by replacing all high colour temperature outdoor lighting (more than 3000k) with warm low colour temperature (less than 3000k) such as High-pressure sodium, Halogen, filtered LED (less than 3000k).
Whether it is urban or environmentally sensitive areas, the lighting's objective must be needed visibility and not too much brightness. In that context, LPS (low-pressure sodium), which emits only a narrow spectrum of pumpkin-coloured light, can be used for lighting near astronomical observatories and environmentally sensitive locations such as a sanctuary, wetland, animal park, and reserve, and shoreline. Usage of reflectors on the highway can drastically reduce lighting needs on highways. In the urban context, civic authorities can use low colour temperature (less than 3000k) high-pressure sodium lights (emits orange colour light), or in case of the need for white light, they can use metal halide and filtered LED (less than 3000k) with optimum brightness, proper shielding. (Pointing downward) to stop the escape of light space.
As LED can produce light with low minimum electricity thresholds, it can be dimmed to much lower illumination levels when less light is needed. Capitalizing on LEDs s these unique characteristics, Smart lighting uses adaptive controls such as dimmers, timers, and motion sensors in LED light fixtures, which enable civic authorities to use outdoor light only on the specific need of that area. The beauty of smart lighting is that it only illuminates needed brightness. It stops illuminating when there is no object or person, or animal near the vicinity of the street. It enhances visibility without creating light pollution.
#Smart lighting technology has the potential not only to reduce light pollution but also to bring back Galileo's night sky. All policymakers worldwide eliminate the blue-white light and universally installs smart lighting technology across all outdoor lighting fixtures and properly shield all lighting fixtures.