Outdoor Lighting

NASA Image

This is a picture of waste. Wasted light equals wasted energy. Light visible from space after dark is not helping anyone on Earth. Light shining into space is of no help in finding directions, no help in avoiding pitfalls and curbs. No help in avoiding assault. It is all conspicuous waste. This wasted light also represents tremendous amounts of environmental damage such as habitat loss and water pollution from mining, air pollution and acid rain and global climate change from burning of fossil fuels - all to shine light into space. And, it makes the stars more difficult to see.

This is a picture of light pollution.

Let's work together to direct the light we need at night down to where we use it.

NASA Image

What can you do to reduce light pollution?

From the International Dark-Sky Assocation (IDA):

Just remember that dark sky friendly lighting does not mean dark ground. Use outdoor light at night only when and where it is needed and at appropriate lighting levels. Use fully shielded, light efficient fixtures aimed downward where it is needed. Incorporate timers and sensors to shut off lights when not in use.

Locally, in Athens, OH, we have an Outdoor Lighting Ordinance...

City of Athens
Outdoor Lighting Ordinance
Adopted on July 7, 2003

Section 21.03.25 Outdoor Lighting

OUTDOOR LIGHTING MAY BE ERECTED IN ACCORDANCE WITH THE FOLLOWING RESTRICTIONS:

(A) LIGHT POLLUTION AND GLARE – ANY LUMINAIRE WITH A LAMP OR LAMPS RATED AT A TOTAL OF MORE THAN 1800 LUMENS, AND ALL FLOOD OR SPOT LUMINARIES WITH A LAMP OR LAMPS RATED AT A TOTAL OF MORE THAN 900 LUMENS, SHALL NOT EMIT ANY DIRECT LIGHT ABOVE A HORIZONTAL PLANE THROUGH THE LOWEST DIRECT-LIGHT-EMITTING PART OF THE LUMINAIRE.

(B) LIGHT TRESPASS – LIGHTING SHALL BE DESIGNED TO MINIMIZE ILLUMINATION OF ADJACENT LOTS AND STREETS. IN NO CASE SHALL ILLUMINATION EXCEED 0.1 HORIZONTAL OR VERTICAL FOOTCANDLES AT THE PROPERTY LINE.

What is a lumen?
We typically buy bulbs based on the wattage, which describes the total power used by the bulb. But not all of this power is emitted as visible light; some escapes as heat. The number of lumens describes the power that is actually emitted as visible light. Packaging for bulbs and lamps usually indicates the number of lumens, as well as watts. It’s right on the box!
For reference, a 60-watt incandescent bulb emits approximately 1000 lumens! A threshold of 1800 lumens would correspond approximately to a 100-watt incandescent bulb. Typical streetlights in Athens produce 16,000 lumens.

What is a footcandle?
A footcandle is a unit describing the power in visible light falling per unit area on a surface. Specifically, a footcandle is a lumen per square foot. The number of footcandles detected by a light meter may depend on the orientation of the meter. It is common for footcandles to be specified as “horizontal footcandles”, corresponding to the meter detector held in a horizontal position; or “vertical footcandles”, with the meter held in a vertical position.

For reference, the full Moon produces an illumination on the ground of approximately 0.017 (horizontal) footcandles. The Illuminating Engineering Society of North America recommends a minimum of 0.2 footcandles for illumination of pedestrian and parking areas with light use. An unshielded 60-watt (100 lumen) incandescent bulb would produce illumination of 0.1 footcandles or less at distances of 28 feet or more.

Light Pollution and Wildlife

Light pollution has an affect on the natural world. From the Folly Beach Turtle Watch Program:

Practice and Preach "Lights out for Turtles!"

Artificial lights affect the nesting and hatching of sea turtles. Brightly lit beaches are a deterrent to nesting females and a deathtrap for hatchlings. Instead of being attracted by the natural light of the moon and starlight on the surf, hatchlings move toward the brighter beams of streetlights, porch and deck lights, floodlights, interior lights, car headlights, flashlights, etc. They fail to find their way to the ocean quickly and become the victims of ghost crabs and gulls, or die from dehydration in the morning sun. Dark beaches are critical to sea turtle survival. Help educate others about the importance of "lights out for sea turtles!"

For more information about the Folly Beach sea turtles and what folks in Folly Beach are doing to protect them, click here.

Photo Credit: Paul Christopher - July 3, 2010

The Effects of Light Pollution on Migratory Birds

In 1968, the 100 story John Hancock Center in Chicago was completed. It wasn't long after that dead birds were found at the base of the building each morning, especially during the migration seasons of spring and fall. These were migratory birds that were thrown off their course by the lights on the building - causing them to crash into the building. William Beecher of the Chicago Academy of Sciences showed these dead birds to the media and to the building's owners in the hope that they would dim the lights during the times of migration. It didn't happen right away, but it did happen. This was the beginning of the "Lights Out" movement. Now Chicago is a model for dimming the lights on the tall buildings from dusk to dawn during spring and fall, and the "Lights out" movement has spread across the country.

The National Audubon Society has taken a leading role in protecting migratory birds from light pollution through the "Lights Out!" movement.