Light Impacts
Hue and timing determine whether rays are beneficial or detrimental
By Janet Raloff
This is part two of a two-part series on lighting’s environmental and human impacts. Part I: “Illuminating Changes,” is available here.
![](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2006/05/5877.jpg?resize=100%2C150&ssl=1)
![](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2006/05/5878.jpg?resize=150%2C100&ssl=1)
![](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2006/05/5879.jpg?resize=150%2C105&ssl=1)
Erin Chesky was a sleep-troubled teen, typical of many. Despite going to bed early each night, this honor roll student struggled to doze off—sometimes lying awake until 3 a.m. Each morning, she fought equally hard to wake up at 5:30, in time to eat breakfast and catch the school bus. Forever tired, “I was like a zombie,” she recalls.