The night sky doesn’t change very much, or so we are told. Aristotle (384–322 BC) set the stage for this assumption with his philosophy of the unchanging starry realm. His teachings persisted for almost 2,000 years. After it was adopted by religion, to question it was heresy. Observers of the night sky slowly chipped away at these teachings by witnessing changes in the night sky. Eventually, these observations could no longer be ignored. The night sky does change, although slowly.
To be fair, changes in the universe occur very slowly, spanning millions of human lifetimes. Some stars have lived as long as the human species, and others have been around for billions of years. Closer to home and with greater rapidity, the planets orbit the sun, and the rotation of Earth ushers the celestial objects across our sky every night.
You might think that one clear dark night is as good as the next, but I don’t think so.
Consider a walk in a park, a symphony or the theatre. Our experience will be different with each exposure. Our awareness and imagination is different every day. Our memory is as much about what we bring to the experience as the event itself.
The presentation of a play is organic—it changes with every performance. During a walkabout, the smell of the air, the sun’s heat and the passersby can never be repeated exactly the same. The flavours of good food vary with the spices and preparation. And as we get older, our aches and pains seem more dominant. Real life is not boring!
We experience a summer’s night. There are many distractions during the day. Each one is like a different spice that alters our experience, but at night, the visual landscape is subdued, distractions are muted or hidden, and our other senses are magnified.
The late-evening dew after a hot, dry day intensifies the scent of the soil, grass, flowers and trees. Without the sound of traffic, our hearing is focused on the sounds of crickets and frogs. More subtle than those sounds are the leaves rustled by a breeze, and the “sigh” that’s produced when the wind blows through needle clusters of pine trees. Most birds are quiet after dark, but there are a few nocturnal species that call out around wetlands and lakes.
Night is an environment and ecosystem, and all our senses combine to create a memorable experience. Not the least of which is our sensitive night vision, which reveals the stars, completing the memory of night.
None of these stimuli are repeated quite the same. Every night creates a new memory, and missing any one of these stimuli weakens the experience.
Photographic images can’t do it justice, even though the stars dominate our vision. The light level is low, which “removes the colours from our sight” (so sang the Moody Blues in “Nights in White Satin” in 1967). And there is a visual texture to the sky—it looks “grainy” because of the reduced visual acuity of our night vision.
During an early-summer evening, the hazy band of the Milky Way rises like a fog bank above the eastern horizon. In late summer, it has rotated across the sky, such that it stands almost vertically above the southwestern horizon.
You and your children may not experience the night as we have in the past. Our ability to see the night sky is changing at an accelerating rate. Look at the first image in this essay. Lights now line the shoreline, and the light from hamlets, towns and cities causes the sky to glow. Most of this light is not natural and, sadly, most of this light is not necessary.
Outdoor lighting has been increasing by 2.2 percent per year—much faster than the population growth. Why is this getting worse? We should be saving energy, not using more of it.
Using more energy-efficient lighting has led to the installation of more and brighter light fixtures, increasing the use of energy for all-night lighting. Lights are now being installed where previously we did not think they were necessary. Also, the emitted white light blinds our night vision and overwhelms the natural night. The light fixtures create a small illuminated patch at the expense of seeing the distant treeline, which provides our peace of mind with a “sense of place” and has taken the night sky from our children.
Fifty years ago, you could see the Milky Way from the suburbs of major cities, but now that is virtually impossible. More importantly, the loss of darkness and the stars at night impacts our physical and mental health. Artificial light at night changes our body’s natural mechanisms to fight disease, including cancer.
How could we let this happen? Only in the last 20 years has outdoor lighting become so bright that these issues have become obvious to medical researchers and philosophers. The night sky becomes featureless and no longer worthy of our attention. As we lose the experience of nature, we lose our perceived connection to it.
There is hope on the horizon. It begins with national and international programs to “protect the night” and the 60 percent of all life that depends on it.
We have Dark-Sky Preserves. Public and commercial parks and even municipalities that want to reduce their impact on the environment can work toward achieving this designation by limiting the amount of light pollution they emit. Technology is making this much easier, but applicants must still make the effort to use light carefully.
The Royal Astronomical Society of Canada (RASC) manages the Canadian program that recognizes the protection of large rural areas and even large urban parks. The critical requirement is the Canadian Guidelines for Outdoor Lighting (CGOL, pronounced “seagull”), which is available, along with the application requirements, on the RASC website (rasc.ca/dark-sky-site-guidelines). These are the only lighting guidelines based on human vision and the sensitivity of wildlife to artificial light.
The International Dark Sky Association in Tucson, Arizona, has its own program (darksky.org/our-work/conservation/idsp/become-a-dark-sky-place). The association’s outdoor lighting requirement is not as eco-centric, but it will designate sites around the world.
However, these programs recognize protected areas, whereas wildlife do not stay within our surveyed boundaries. We have the ability and technology to cut light pollution at the source by using lighting with low ecological impact. These products have been developed in Canada, and now other manufacturers are beginning to copy the technologies.
How can your town get on board? The scientific research has defined the course with the following four easily achieved principles.
- Do shield light fixtures so that no light shines beyond your property. This cuts glare and light trespass and reduces the amount of energy you use for lighting.
- Do not use white light. The blue colour that makes it look white amplifies the sensation of glare, and is the most bio-disruptive light we produce. We can use shielded low-power “bug lights” around your home, and municipalities should use fully shielded amber LED street lights.
- Do not over-light. The lighting industry recommends a reasonable light level on residential streets. Do not exceed them. With shielded amber lights, we can see better with less.
- Schedule the light based on need. Rush hour is typically over by 10 p.m., so lighting levels for peak traffic can be dimmed for most of the night.
Some local governments have developed or are considering developing policies that illuminate their town to many times the industry safety levels, but there are consequences. Over-lighting creates distraction and glare, which slows reaction times and undermines visibility, safety and security, and the higher cost is carried by all taxpayers—not just the city officials or politicians who make these decisions.
Now that we know what we are losing and that there are solutions, we need to reduce the use of white light and unshielded fixtures. Your neighbours won’t do it unless you ask, and cities won’t do it unless you demand it of your elected officials.
One of Canada’s foremost writers and educators on astronomical topics, the Almanac has benefited from Robert’s expertise since its inception. Robert is passionate about reducing light pollution and promoting science literacy. He has been an astronomy instructor for our astronauts and he ensures that our section on sunrise and sunset, stargazing, and celestial events is so detailed and extensive it is almost like its own almanac.