Evaluating Potential Spectral Impacts of Various Artificial Lights on Melatonin Suppression, Photosynthesis, and Star Visibility

Introduction

The article Evaluating Potential Spectral Impacts of Various Artificial Lights on Melatonin Suppression, Photosynthesis, and Star Visibility is an analysis of the effect of artificial lightning on environment. The article documents a variety of tests conducted on plants and cells to see the safety and possible issues of using artificial lighting. Specifically, as it relates to our class, it studies how well plants are able to undergo photosynthesis in various lighting conditions.

Summary

The articles begins in the introduction with a brief history of how artificial lighting presence has gradually grown and become more involved our lives. It discusses how people lived before the lightbulb spending most of their days outside receiving enough sunlight and how the creation of the light bulb has caused more time spent inside. The main focus is how so many people used artificial light at night or ALAN for short. 99% of the people in the US and Europe are exposed to ALAN. Artificial light at night isn't just affecting humans but rather the environment around them. The author mentions various studies the artificial light had effects reproduction, communication and habitats of nocturnal animal species.

However, ALAN isn't just affecting fauna, but flora too. There have been documented issues with trees adjusting to season variations. This has to do with ALAN stimulating photosynthesis in plants when it does not normally occur. The growth, development, and reproduction of plants has been effected as these plants need certain wavelengths, duration, and intensity of light. The article then begins to discuss the effects on humans. Artificial mostly has a large impact on circadian systems and physiological functions. The circadian systems is basically summed up as the systems that manages the sleep and awake cycle. The author also bring up studies showing higher risk of certain cancers, obesity, diabetes, and depression. However, it is not all doom and gloom. The author brings up the benefits such as that artificial light has proven to work in light therapy for seasonal affective disorder.

The third and final main topic of the article is the reduction of star visibility in the night sky. ALAN is around four times greater than illumination from a starry night sky. Light pollution from a variety of sources such as street lamps, billboards, etc used different wavelengths of light than natural light sources and begin to block out the sky. This allows us to see less and less and you must travel far from the cities to actually see the true beauty of the night sky with the naked eye.

The article begins to then detail the methods it used for each step of the experiment. Most importantly in photosynthesis it notes the need for a clear definition of wavelength and intensity of light to be used. Each species of plant had a variety of different action spectrum. Action spectrum is a graph of the rate physiological activity when under certain wavelengths. There are a variety of different chlorophyll structures of molecules that are more sensitive to different wavelengths. The two main focuses of the article Chlorophyll a and chlorophyll b are mostly found in vegetables and plants. They absorb more efficiently the blue and red part of the spectrum. Accessory pigments such as carotenes can also take part in photosynthesis which absorb blue light much greater than red. The author decides to choose a global action spectrum which is fit for an average vegetation type.

Critical Assessment

The main point of the article is proposing three new indices to characterize the lamp spectrum. The authors created the indices to allow for quick estimation of the possible impacts of certain lights on melatonin suppression, photosynthesis, and star visibility.

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