Thanks to novel inventions and advanced technology, human being, a diurnal species, now can enjoy a nocturnal life as we do under the Sun. Nowadays, we have engineered the night to receive us by filling it with light. Nevertheless, this engineering comes with serious consequence, that is, light pollution, also known as photopollution or luminous pollution. This is a form of environmental degradation, which results from the excessive artificial lightings. Its sources include street lamps, neon signs, billboards, offices, and illuminated sporting venues. Instead of directly lightening objects, these artificial beams refract and scatter around everywhere unexpectedly. Hence, they not only obscure the starring night but cause damage to both our environment and human bodies. Therefore, light pollution is not even more a scientific issue to experts but a global problem to everyone.
According to the International Dark-Sky Association (IDA), this environmental pollution can be classified into four types: light trespass, over-illumination, glare, and light clutter. The first type is light trespass, which occurs as unnecessary light enters one’s property. When an intense beam outside causes sleep deprivation, this condition can be called light trespass. For instance, Hong Kong has a serious light trespass problem due to countless luminous ornaments of skyscrapers. Despite some 30 to 40 citizens annually complaints about light abuse, Hong Kong still ignites the night sky to demonstrate its prosperity. The second type is over-illumination, which stems from the excessive waste of light. Improper lighting designs in the workplace, inadequate lighting maintenance, and 24-hour commercial advertisements all contribute to over-illumination. A survey conducted by the U.S. Department of Energy Source suggests that some 30 to 60 percent of energy is wasted by commercial advertising uses, two times than average U.S. residential