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.
Wasted artificial exterior light going to sky glow, glare, and
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.
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.
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?
Light shining into
eyes rather than on
objects of interest.
Street Lights – and Glare
Full cut off light
In illumination zone
out of illumination zone
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
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!
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
See this person. In the next image she has only moved about 5 feet.
Here we see a student on the walkway.
Where is she now? (She only moved about 5 feet.)
Here she is! Feel safer with globe lights now? Why is she hard to see?
Unshielded Fixture – “globe light”
• Minimizes glare.
• Minimizes light
• Minimizes light
• Controls light output
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!
Here a good deal of the light (and energy) is wasted,
and the glare may be too high for comfort.
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!
When most of the light goes
up – into space, it is wasted!
It simply lights up the clouds
above us or the underbellies
Credit: NOAA Digital Archive
1999 – USA wasted a billion dollars
on the misuse of outdoor light!
2010 – USA
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
Dark Sky Communities with
light pollution ordinances now:
as well as other recognized
Dark Sky Reserves and Parks
Good Lighting ≠ No Lighting
Some cities and states are now
enacting light pollution ordinances.
City vs. Dark site
Aug 14 2003
during a blackout.
House lit inside by generator.
Aug 15 2003
Handsome light Day and Night – no light directed upward at night!
Credit: Night Sky Network
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?)
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.)
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.
n Maximizes the desired effects by minimizing the
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