Astronomers reflect on light pollution: Some nighttime lighting projects are a waste of resources

　　
Experts Wang Tianhou and Tang Zhenghong are explaining the impact of light pollution on ecology

　　If you live in a bustling city, how long has it been since you last saw a brilliant starry sky? Tang Zhenghong, a researcher at the Shanghai Astronomical Observatory of the Chinese Academy of Sciences, revealed today in a lecture that during the 13 years from 1994 to 2007, the night sky background brightness at Shanghai's Sheshan Observatory became approximately 20 times brighter. He reflected that some places' massive nighttime lighting projects are truly a waste of resources.

　　Sheshan Observatory's night sky background became 20 times brighter in 13 years

　　Tang Zhenghong stated that over 13 years, the night sky background brightness at Sheshan Observatory has brightened from magnitude 19 to magnitude 15.8, equivalent to becoming 20 times brighter. The night sky background at internationally excellent observatories is generally below magnitude 21.5, "that is to say, about 200 times darker than Sheshan Observatory."

　　He believes that any light directed into the sky at night will make the sky brighter, and the improper use of lighting in cities will cause light pollution that directly reduces the detection capability of telescopes. Tang Zhenghong explained that light pollution is divided into three types: white-bright pollution caused by glass curtain walls and glazed tile walls during the day; artificial daylight caused by strong light at night; and colored-light pollution. Light pollution affects not only astronomy enthusiasts, but for every person living in a city, it pollutes the visual environment, and prolonged exposure can also cause harm to the human body.

　　Tang Zhenghong stated that compared with other types of environmental pollution, light pollution is actually the easiest to remedy. As long as changes are made in the design and installation of lighting fixtures, light pollution can be transformed into good lighting. For example, adjusting the direction of illumination and using good lampshades can achieve the goal of not producing upward-directed light.

　　Hangzhou Bay Bridge lighting causes multiple bird collision deaths

　　Another expert, Professor Wang Tianhou from the School of Life Sciences at East China Normal University, also revealed a phenomenon during his speech: after the Hangzhou Bay Cross-Sea Bridge was built, staff discovered many incidents of bird collision deaths caused by lighting. However, he also noted that such reports are relatively rare within cities themselves. Tang Zhenghong explained that birds may die from collisions caused by lighting possibly because birds use sunlight to determine their migration direction, and the artificial lights mislead them.

　　Reports of bird collisions in cities are relatively rare. Some people believe this is due to high levels of urban noise or the abundance of scattered light sources in cities. Wang Tianhou frankly admits that there is no scientific experiment or evidence to support this speculation.