I used to go for a walk every night. It was a pleasant habit—exercise, fresh air, quiet time alone to think. I made a point, whenever possible, of walking in an area away from the city lights, where the sky was dark enough that I could get a good look at the stars. I knew how to pick out some of the constellations, though I could never quite understand how anyone could see a goat or an archer in the patterns of stars. Seeing shapes in clouds is one thing, but mentally connecting the dots to form a complex picture didn’t really work for me. That’s not to say I didn’t see anything in the stars, though. As I looked at a particular star, I would think about the possibility of life in outer space, the chance that a planet circling that star may be home to people like me—or unfathomably different beings. I’d think about how Earth is just another one of those countless planets and the sun just another one of those countless stars. And picking my favorite star of the moment, I’d say to myself, “Someday I’ll find a way to go there.”

Looking at the stars and thinking about them in this way always had a very calming effect on me. I felt as though it gave me a sense of proportion, that it put my own crises and ambitions in perspective. It didn’t make me feel insignificantly small; instead, it made me feel somehow privileged to be able to see and understand what may be out there, and to realize I’m a part of something so big.

Nowadays I don’t notice the stars very often, and when I do, I don’t usually think about them as I once did. But every now and then, I’ll be on a trip—an island, a desert, a rural getaway somewhere—and again the stars will catch my attention. Invariably I’ll wonder why I hadn’t noticed them in so long. Is it just that I’m older and busier? That may be part of it, but a bigger part is that the lights of the city often make it very hard to see the stars, always focusing my attention on the surface of my own planet. This is one consequence of the increasing problem of light pollution.

The term “pollution” is apt because excess or unwanted light can be an irritation or even a safety hazard. Like air pollution, light pollution is typically a by-product of machines and devices that were intended to make our lives easier, more convenient, and safer. Another similarity is that light pollution can be reduced greatly with careful attention to design. But because most people have become accustomed to light pollution as a fact of life, there is usually little incentive to worry about it when designing or purchasing lighting products.