In September 2021, Pittsburgh, Pennsylvania, became the First Major City to rethink how Urban Lighting will be conducted, Passing a Dark-Sky Ordinance for: Visibility of the Night Sky; use less Energy; help Plants and Animals by maintaining a crisper Day-Night Cycle; to Reduce Glare for better Night Vision; and to Benefit those in Poorer Neighborhoods who are Disproportionately Negatively affected by Wasteful Overlighting.
The City is reviewing Bids to choose a Vendor, by the end of the year, to Replace All of its 35,000 Streetlights, as well as add 8,000 New Ones, in the recommended Color Temperature around the City, according to the Mayor’s Office.
The Ordinance will also affect All newly installed Lighting at City-owned Buildings, Parks, and other Properties, requiring Dark-Sky Principles to be observed. Other Institutions around the City are already getting into the Spirit and joining the effort: The Pittsburgh Zoo and PPG Aquarium; Phipps Conservatory and Botanical Gardens; and the National Aviary, have already announced they will adopt the Ordinance on their Properties.
It largely arose out of the efforts of Astronomer Diane Turnshek, and Architect/Urban Designer Stephen Quick, both Special Lecturers at Carnegie Mellon University. In August, the Astronauts on the International Space Station took some Pictures of Pittsburgh on a clear night. And that's the “before” shot. The Astronauts are going to continue to take Pictures of Pittsburgh, so we will have “during” Pictures and “after” Pictures.
Dark-Sky Lighting uses Technology like: Motion Sensors; Dimmers and Timers; Cooler Temperature Bulbs; and Shielding, which makes sure Light is Directed Down instead of Up, to Reduce Light Pollution while providing enough Lighting for Safety and Comfort.
The City plans to Retrofit existing Streetlights to Dark-Sky-Compliant LED Lights. Pittsburgh's current 4,300 LED Streetlights glow at 5,000 kelvins and give off a Bright Blue-White Glare. The New LED Lights will be at a Lower Temperature and look much Softer and Warmer, as recommended by the International Dark-Sky Association. The notion of “light temperature” has to do with Black-Body Radiation. Let’s say we have an Opaque Metal Sphere that doesn’t reflect any Light, Black Body, and we Heat it so Hot that it Glows. The Higher the Temperature it reaches, the Shorter, Bluer, More-Energetic, the Wavelengths of Visible Light it will Emit.
Stars behave pretty much like Black Bodies, so we can use the Color of a Star to get an idea of its Temperature: Temperaturesare shown in kelvins (K). To get Degrees Celsius, subtract 273.15 (3000 K = 2726.85°C). That in turn is about 4940°F. Proper Nighttime Lighting from Shielded Fixtures keeps Illumination from pouring into the Sky. It also improves Visibility on the ground, making Streets and Highways, Safer. These Shielded Fixtures keep the Light from Shining into our eyes, thereby making it easier to see.
Because Less Energy is Wasted, we don’t have to Pay for outrageous Electric Bills. Take a look at a Cloudy Night over the City. See the white bottoms of the clouds? We should all be appalled at that Waste.
Proper Nighttime Lighting also benefits Animals and Plants, which have evolved, like Humans, in a Day-Night Cycle. Living things need the Dark just as much as they need the Light.
By reducing Nighttime Lighting, we also can improve Human Health. The Adverse Effects, bad Nighttime Lighting has on the Body’s Production of Melatonin and the corresponding Increase in Cancer Rates in Humans.
The International Dark-Sky Association at darksky.org is a great place to start.
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