Sky & Telescope - January 2024 - 29

83%
Fraction of world's
population living under
light-polluted skies in 2016
SOURCE: F. FALCHI ET AL. /
SCIENCE ADVANCES 2016
$50 billion
Global spending on
light that escapes
to space
SOURCE:
DARKSKY INTERNATIONAL
1.28 - 2.56
2.56 - 5.12
5.12 - 10.24
10.24 - 20.5
20.5 - 41
>41
tions of nighttime lights - and the amount of that light -
increased by about 2% per year. That's roughly double the rate
of global population growth during the same period of time.
Meanwhile, the brightness of the night sky seen from the
ground has continued to rise. Ten years of Globe at Night
observations show a steep increase: an average of 10% per
year at the level of country-size land areas. Much of the
light causing this increase seems to be concentrated in and
around cities. As the human population becomes increasingly
urban, more people than ever are separated from the
stars. While on a clear night under pristine skies the unaided
eye might see as many as 4,500 stars, an observer in a large
city might see 35 or fewer.
But light pollution is about much more than whether
we can see the stars at night. We know that artificial light
at night has a harmful effect on nearly all plant and animal
species studied to date (see page 34). A clear link exists
between ALAN exposure and adverse human health outcomes,
but the influence of outdoor light sources specifically
is largely unknown. And we know that, in at least some cases,
racial minorities are exposed to more ALAN. A growing number
of Indigenous individuals have also expressed concern
about light pollution's impact on their living cultural traditions
(see sidebar, page 33).
From an economic perspective, the wasted energy represented
by ALAN escaping into the night sky is thought to
account for about 1% of the world's greenhouse-gas emissions.
And although outdoor lighting is often installed in the belief
that its presence discourages crime and enhances personal
security, no compelling evidence bears out that conclusion.
How We Got Here
There are several reasons that may explain how and why we
use outdoor lighting as we now do. One is that the cost of
generating light has plummeted, due to the energy-efficiency
gains of white LEDs since their introduction to the international
market in the early 2000s. LEDs cost more up front,
but thanks to the long-term energy savings, the overall
operating cost is much lower compared to earlier lighting
technologies, making LEDs appealing to an increasingly large
sk yand tele scope .o r g * JANUARY 2024 29

http://skyandtelescope.org

Sky & Telescope - January 2024

Table of Contents for the Digital Edition of Sky & Telescope - January 2024

Contents
Sky & Telescope - January 2024 - Cover1
Sky & Telescope - January 2024 - Cover2
Sky & Telescope - January 2024 - 1
Sky & Telescope - January 2024 - Contents
Sky & Telescope - January 2024 - 3
Sky & Telescope - January 2024 - 4
Sky & Telescope - January 2024 - 5
Sky & Telescope - January 2024 - 6
Sky & Telescope - January 2024 - 7
Sky & Telescope - January 2024 - 8
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Sky & Telescope - January 2024 - 81
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Sky & Telescope - January 2024 - 83
Sky & Telescope - January 2024 - 84
Sky & Telescope - January 2024 - Cover3
Sky & Telescope - January 2024 - Cover4
Sky & Telescope - January 2024 - SA1
Sky & Telescope - January 2024 - SA2
Sky & Telescope - January 2024 - SA3
Sky & Telescope - January 2024 - SA4
Sky & Telescope - January 2024 - SA5
Sky & Telescope - January 2024 - SA6
Sky & Telescope - January 2024 - SA7
Sky & Telescope - January 2024 - SA8
Sky & Telescope - January 2024 - SA9
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