astronomy Credit : Jeff Hapeman Have you seen this lately? Keep the Sky DARK at Night http://antwrp.gsfc.nasa.gov/apod/image/0609/aurora_hapeman_bi

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Credit : Jeff Hapeman

Have you seen this lately?

Keep the Sky DARK at Night

Dark Sky Organization – IDA
Images are credited to International Dark Sky Association unless otherwise noted.

Approximately 70% of the world’s population

cannot see the Milky Way; many have never seen it.

Photo Credit:

William Keel,

University of

Alabama

Light Pollution:
Wasted artificial exterior light going to sky glow, glare, and

light trespass.

Jupiter

Elements of Light Pollution

Light pollution travels about 200

miles and impacts birds, bats and

other animals as well as humans.

The Washington Post reported a connection between light pollution and breast cancer

in its Feb. 20 news story “Lights at Night Are Linked to Breast and Colon Cancer;

Study Bolsters Theory About Interference With Production of Key Hormone.”

Sky glow – wasted, misdirected light

shining up in the night sky. Light clutter

can affect aviation.

NSN 5

Sky Glow
Lots of light scattering off particles in the air giving
the appearance of a glowing sky. See any stars?

Light Pollution = wasted

energy and money. Light

that goes upward does

not help us see better at

night on Earth’s surface.

NSN 6

Glare
Too much background light – can you see the stop sign
in the foreground? Can you even read the sign below it?
Do you think older drivers can see the stop sign in the glare?

Glare-

Light shining into

eyes rather than on

objects of interest.

Street Lights – and Glare

Full cut off light

(FCO)
Sag light

Same

In illumination zone

out of illumination zone

NSN 8

Light Trespass

Would you be able to sleep if your bedroom
windows faced this neighbor’s light? (below)
What about the impact on your health?

Negative impacts on

human health include:

immune systems issues,

higher risk of breast cancer

and disruption of circadian

rhythms.

It is illegal to send fumes

over a neighbor’s yard, so

why is sending unwanted

bright light onto neighbor’s

property still permitted?

LA 1988 Night Sky is already Lost!

LIGHT POLLUTION:

Any adverse effect of

artificial light including sky

glow, glare, light clutter,

decreased visibility at night,

energy waste , and light

trespass with its associative

negative impacts on health

and the environment.

Why not just install fixtures

that reduce glare, provide

better visibility, save energy

and don’t trample on the

environment?

NSN 10

See this person. In the next image she has only moved about 5 feet.

Here we see a student on the walkway.

NSN 11

Where is she now? (She only moved about 5 feet.)

NSN 12

Here she is! Feel safer with globe lights now? Why is she hard to see?

NSN 13

Unshielded Fixture – “globe light”

NSN 14

Shielded
Fixture

• Minimizes glare.

• Minimizes light

directed upward.

• Minimizes light

trespass.

• Controls light output

and direction.

Shielded fixtures and full cutoff lights

can reduce glare and light scattering

(important to pilots) by directing light

downward where it is needed!

Now there is nowhere to hide!

NSN 15

Here a good deal of the light (and energy) is wasted,
and the glare may be too high for comfort.

NSN 16

An optimal design! Note the added light
near the entrances where there is more need.

Lighting triggered via motion detectors can also save energy and reduce light

pollution as well as increase safety by highlighting any unexpected motion!

Bad Lighting = Wasted Energy

Motion sensors can save energy and increase safety

by bringing attention to any unexpected activity!

Bad Lighting

When most of the light goes

up – into space, it is wasted!

It simply lights up the clouds

above us or the underbellies

of airplanes!

USA “nightlights”
Credit: NOAA Digital Archive

1999 – USA wasted a billion dollars

on the misuse of outdoor light!

2010 – USA

even brighter!

Only satellites can see this light –

not much help for us on Earth’s surface.

Bad Lighting = Wasted Energy

Above: Tucson 1950

Below: Tucson 1990 – 30 years ago

Lost Sky due to Tucson’s Light Dome!

Kitt Peak – world’s largest

collection of optical

telescopes

southwest

of Tucson

Light
Pollution

Good Lighting
Dark Sky Communities with

light pollution ordinances now:

Flagstaff, AZ

Harmony, FL

Sharon, GA

as well as other recognized

Dark Sky Reserves and Parks

Note:

Good Lighting ≠ No Lighting

Some cities and states are now

enacting light pollution ordinances.

Comparisons

City vs. Dark site

Ontario, Canada

Aug 14 2003

during a blackout.

House lit inside by generator.

Ontario, Canada

Aug 15 2003

Handsome light Day and Night – no light directed upward at night!

Credit: Night Sky Network

24

Typical car lot? Much better!

Glare No Glare

Earth at Night

Credit: C. Mayhew & R. Simmon (NASA/GSFC,

NOAA/NGDC, DMSP Digital Archive)

Wasted energy concerns are related to

the irresponsible use of outside lighting.

What about adverse effects on plant

and animal life and reproduction?

(Sea turtles and trees for instance?)

NSN 26

Light pollution is a global issue with local solutions.

Consider the economic impact of wasted energy and the environmental impact of misused light.

“THE EARTH – We have only one Earth.
A beautiful island in space, and a jewel without price,

It is the only known home of life in all Creation.
To us it may seem indestructible and its resources inexhaustible,
Yet it is nothing but a speck of dust, adrift in a hostile Universe.
Treated badly, it could become a barren wasteland devoid of life.

Treated wisely, it can be a safe home for us and our children forever.
The choice is ours.” (Peter E. Spargo, Cape Town, 4 December 1988.)

NSN 27

Why should we care? (a review)

• We save money and energy;

• We improve safety for motorists and pedestrians;

• We increase security;

• We benefit animals and animal habitats;

• We improve the quality of life, decrease negative health impacts;

• We lessen greenhouse gas emissions that contribute to global warming;

• We preserve the starry night.

25% of energy in the USA goes to lighting! We need to reduce this

consumption which will in turn reduce our carbon dioxide output.

Good Lighting

n Maximizes the desired effects by minimizing the
adverse effects:

n Respects the habits & habitats of animals & plants

n Focuses light down so less is needed – Conserves energy

n Decreases glare, light trespass, and sky glow

n Increases safety and security:

n Enables aging or disabled eyes to see better at night.

n Increases visibility (e.g., sharper contrast, fewer shadows)

n Maintains human health:

n Circadian rhythm (which can impact immunology)

n Sleep disorders (due to light trespass and blue light)

n Provides good (nighttime) ambiance

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