Why Is the Night Sky Not So Dark?

The violation of our night sky’s quiet majesty is a crime not only against nature, but also against the spirit and imagination of humanity. In a single generation, light pollution has grown from an almost nonexistent irritant to a problem of national and global proportions. Even today, due to light pollution, many of our generation have never seen the ghostly beauty of the Milky Way, the excitement of a meteor storm, or the wispy, shifting tail of a comet. Very likely, our grandchildren will be denied the opportunity to camp, sleep, or fall in love under a starlit sky. Think about it – most artists, scientists, and philosophers of note throughout history were influenced, inspired, and challenged by the beauty of a pristine night sky.

The impact of light pollution is even greater than you might realize. First, an estimated 30-35 % of all energy produced by artificial light is wasted. Light directed upward wastes energy. Light reflected upward wastes energy. Light directed at areas to which it is not intended wastes energy. The cost of all this waste is upwards of $1-2 billion per year. Second, light pollution contributes to air pollution. The 30-35 % of the energy directed toward the sky requires 6-10 million tons of coal per year to produce. The air pollution caused by burning coal in turn exacerbates light pollution by scattering light from below and blocking starlight from above. A third impact of light pollution is its affect on animals and plants. Excessive artificial light confuses the sleeping patterns, reproductive habits, and migration cycles of turtles, birds and other animals and plants. Forth, light pollution impedes scientific research and discovery by diminishing the capabilities of nearly every ground based observatory in the world. Finally, light pollution limits our imagination, invades our privacy, and robs us of nature’s beauty.

Several misconceptions exist about lighting. First, there is an attitude that if some is good, more is better. Businesses often use 3-6 times the industry recommendations for lighting. Second, many believe that more light improves our performance at night. On the contrary, excessive lighting confuses and interferes with night vision used to drive and performing other activities. Humans actually need very little light to effectively navigate their way or work with their hands at night. A third belief is that lighting increases personal safety and improves property security. Although perceived as a deterrent to crime, studies by the DOJ and the National Institute of Justice show no conclusive evidence that lighting prevents crime.

While the problem of light pollution seems too daunting for any one person to tackle, the solutions are surprisingly straightforward and each of us can contribute to reducing light pollution. First, use only the amount of light necessary for a specific purpose. To accomplish this, use timers on lights and turn off lights when not in use. Second, direct lighting only to areas requiring illumination. To accomplish this most effectively, use a reflective light shield available at most hardware stores. Install the light shield so that no light leaks or reflects above the horizon. This not only reduces light pollution but also reduces waste by requiring less light since all the available light is directed and reflected toward the desired area. Third, use High Pressure Sodium lights instead of common Mercury Vapor lights to yield energy savings of 30-40%. Better yet, use Metal halide lights to yield a 50-70% energy savings. Not only do these lights reduce light pollution, they emit light in specific frequencies that observatories can more easily filter out. Together these solutions not only reduce light pollution but also reduce air pollution and energy waste without affecting the security of people and of property.

From  my back yard near Houston, the incredible 1997 Comet Hale-Bopp appeared as a mere cotton ball, a bit larger than the full moon. From a reasonably dark sky, about 100 miles from downtown Houston, the comet had a tail 10 degrees long or 20 times the diameter of the moon. From a very dark sky such as Fort Davis, TX, the comet’s tail reached half way across the sky (50 times the full moon). It is the dream of many that someday these truly dark skies will be protected from light pollution so that we and our children can continue to enjoy the wonders of the universe. Such naked eye wonders include the Andromeda Galaxy, your shadow cast not only by the moon but by the planet Venus, the zodiac light caused by the suns rays bending around the earth, or the breathtaking view of 10000 stars instead of a few dozen.

There is an organization dedicated solely to preserving and protecting the nighttime environment and our heritage of dark skies through quality outdoor lighting. Its name is the International DarkSky Association (IDA) and its web address is www.darksky.org. IDA provides more information on and opportunities for reducing light pollution and keeps us up to date on plans, successes, and legislation concerning this global problem.

I hope  you realize that light pollution is a big problem, but with simple solutions that each of us can implement. So, the next time one of your children or grandchildren ask “Why is the sky dark at night”, consider not only answering their question scientifically, but also educating their generation on light pollution by discussing an equally intriguing and challenging question that impacts them even more: “Why is the sky not dark at night?”


Photo credit: Kent Biggs

NGC 7771 Galaxy Group (Credit & Copyright: Kent Biggs)


Photo Credit: Kent Biggs (The Great Whirlpool Galaxy http://www.kentbiggs.com/images/galaxies/M51.htm )

The Great Whirlpool Galaxy (Credit & Copyright: Kent Biggs)

17 thoughts on “Why Is the Night Sky Not So Dark?”

  1. I can remember seeing the Milky Way from my aunt and uncle’s farm when I was little. It was astounding. I miss it. We live in the country now, and see tons more stars than we did in the city, but the light pollution from the nearby town and the slightly distant city still hide the Milky Way. 🙁

    1. Indeed they do. My SIL had a place on the lake, and it was just amazing to me to realize the stars were still there. I’d gotten so used to not seeing them. It was heartbreakingly beautiful.

    1. Oh, that sounds lovely! Maybe there’s a whole new industry in this – dark sky travel? (That’s an almost cynical and unhappy thought – I’d rather be able to lay out on the grass in my own back yard at night and see the stars!)

  2. It is not so bad here in India though in the big cities the night sky cannot be really seen. It is however reaching Western standards and soon it will be the same here too.

    1. Well, I guess the only surprise, there, is that you haven’t caught up with us yet. :/ Not a race you should aspire to win, but who can argue against industry and “progress”?

  3. That’s one of the many reasons I like living out here in the country. I marvel each night when I go out with the dog and see lots of stars. Most nights I can see the big dipper. Thanks for the mental pictures and for the actual pictures.

    1. Yes, I guess you would see some, there! I don’t guess I’ve stayed up late enough or really looked, the times I was there – that, or it was overcast. The Big Dipper and Orion are about ALL I can see here in the Houston suburbs. 🙁

    2. By the way, I really can’t take credit for the mental pictures – and certainly not for the actual ones – Kent Biggs is a friend and colleague, and I found this post buried in obscurity (dated 2009) and asked if I could republish it here. He graciously allowed me to. Please click through the links to HIS site for more of his original astrophotography. I can honestly say that I know a real person who has his own observatory. http://www.kentbiggs.com/observatory.htm How cool is THAT?

  4. This is an excellent post, Holly! It is so interesting that you mentioned Hale Bopp and Fort Davis, TX. When Mr. Quantum and I got married, we saw Hale Bopp A couple of weeks before our wedding. We thought of it as ‘our comet.’ We were in the Northeast then and it did put on a spectacular show! After we got married, we lived in Texas (Dallas) until we moved back up north to take care of my parents. Our hope is to move back to Texas, to, (yes, if you guessed it) Fort Davis. We’ve been interested in retiring there specifically for the dark skies.
    We belonged to the Texas Astronomical Society (TAS) while we lived in Dallas. When we moved back up north, we expected, living outside of any major cities, that it would be dark enough here to afford us darker skies than in Dallas. Unfortunately, it is not to be.

    1. Lake Tawakoni (not far from Dallas) is the last place I recall seeing stars so abundant it brought me to tears, realizing they were “still there.” Seriously – I don’t know why I thought the stars had just faded away like clean air or water. Of course they were “still there.” But there’s something overpowering about seeing the proof of it, sometimes.

  5. Thank you so much for this wonderful and educational article.

    As someone who spent his preschool childhood in Rural India, I have some fond but vague memories of the night sky. I am always drawn to it’s beauty and mystique, and the awe and wonder that feeds the imagination and curiosity.

  6. The night sky has become so dark it’s almost creepy.When I was a kid we watched stars but it wasn’t like it is now.When the sun goes down its pitch black right away.I guess all the chemtrails spraying has taken oxygen or nitrogen out of our air thus even on a clear night giving us the sensation of being in a spook house!Man,night is frigging dark!

    1. No, it’s just light pollution, Lee. The stars’ light is almost imperceptible to us when there’s so much artificial light (from parking lots, street lighting, etc.) That’s what this post is about. Not chemtrails or lack of oxygen – and if you go FAR from the city, you can still see the stars clearly. But it’s getting harder and harder to escape the urban light pollution.

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