The earth at night as viewed from a space, in a composite image from NASA.

The world is not as dark as it used to be. Streetlights, parking lot security lights, office building lights, and neon signs shine all through the night. Light pollution can come directly from light bulbs, or it can bounce off of dust and water droplets in the air, creating a bright haze called skyglow. This 24-7 illumination can be seen from space, and it has negative effects on humans and wildlife. But there are ways to dim the lights and reduce their effects—and save energy in the process.

Astronomers have long aware of the problems associated with nighttime illumination—it makes stars disappear. Big telescopes are built away from big cities for this reason, although bright lights have a way of encroaching. QUEST blogger Ben Burress talks about light pollution and astronomy here and here.

Non-astronomers are affected by nighttime lighting, too; exposure to light at night affects our circadian rhythm, the 24-hour cycle deep inside our bodies. Seeing light at night can cause sleep disorders. And long-term exposure to light at night has been linked to breast cancer, because light inhibits the production of melatonin, which slows the growth of cancer cells.

Exposure to light affects animals, too. Anyone who has sat next to a porch light on a summer evening knows that moths are drawn to light—along with a multitude of other insects. Outdoor lights disturb insects’ nighttime navigation, and affect their feeding and mating. Lizards are often found feeding on the tasty insect snacks that gather around lights. Often, these lizards are not normally nocturnal—staying up at night gives them access to a “night-light niche” and an abundant food source. It also creates the opportunity for interactions between animals that would never meet in the dark conditions of previous centuries. Some lizards get a double benefit, basking in the warmth given off by artificial lights (incandescent lights are really inefficient; most of the energy they use goes to producing heat, not light).

Night lights make birds sing at odd hours, and mess with their mating and migration schedules. During migration, birds are drawn to the light from tall buildings and towers, resulting in deadly collisions.

Sea turtles are perhaps the most famous example of animals affected by light. Hatchlings swim towards the light—historically the horizon above the ocean. But now that beaches are backed by well-lit condos and hotels, baby turtles crawl further onshore instead of out to sea. There is evidence that sea turtles are drawn to light with short wavelengths, and using bulbs with longer wavelengths or using filters that cut out short light wavelengths reduces the number of baby turtles crawling in the wrong direction.

Simple fixes, like different bulbs or shades that focus light on the ground, can do a lot to re-darken the night sky, as does turning off unnecessary lighting. Dimmer, more efficient bulbs that provide enough light for human needs—but not too much—are a step in the right direction, and can save on energy costs. Dark sky conservation and stricter lighting ordinances will help.

I was surprised by the negative health effects of exposure to nighttime lighting—something to keep in mind as I work late into the night, basking like a lizard in the glow of my computer screen.

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Counting craters on a Lunar Reconnaissance Orbiter image
of the Moon's surface. NASA/LRO

Ever been out on a clear, lazy night and tried to count the stars–or the kind that fall from the sky during a meteor shower? How about craters on the Moon, or distant galaxies in deep space?

If you like this kind of work, there is a job for you! Several, in fact….

In this day of the Internet and electronic databases, our ability to store, process, share, and, yes, be overwhelmed by information is greater than ever before. In fact, our ability to analyze data is only outmatched by our capacity to acquire it—which offers some pleasing challenges: buried in the riches of data of our Universe that we are piling up around us, there is plenty of opportunity for just about anyone to grab a shovel and dig in, sharing in the adventure of exploration of the Universe around us!

Okay, that was the sales pitch, here are some details.

Count some stars! Subject: stars visible to the naked eye; what's being investigated: the impact of urban light pollution on our access to the simple wonders of the night sky. Every year, Windows to the Universe conducts the Great Worldwide Star Count citizen science project, enabling anyone who can look up at the night sky and count some of the stars there to participate in real science. We're already into the Count, which runs this year from October 31st through November 12th. For details on how to participate, check out their website.

Results from the Great Worldwide Star Count are presented in a global map showing the "limiting magnitude" from thousands of locations where citizen scientists observed. The limiting magnitude is a measure of brightness of the faintest star that can be seen from a given location.

How about craters on the Moon? Looking at the Moon through a small telescope, you can count some of the largest craters—those that are typically at least a mile or so across. By virtue of the powerful LROC camera on NASA's Lunar Reconnaissance Orbiter (LRO), the surface of the Moon is rabidly being photographed to a level of detail that reveals craters as small as a foot and a half across!

Craters are a fantastically rich source of information regarding the history of our solar system, each one a record of a single meteoroid impact which, when examined in context with all the rest, allows scientists to forensically piece together the puzzle of the formation of the Moon and our region of the solar system.

While there are estimated to be at least 300,000 lunar craters with diameters of about half a mile or greater on the side of the Moon facing the Earth, smaller craters are estimated into the millions, and microcraters are most likely uncountably common.

This means science needs your help! And you can give it, at Moon Zoo. Log onto the Moon Zoo website, register yourself as an official lunar explorer, and have at it, friend. Examining LRO images of the Moon's surface, you will count and classify craters and boulders, and mark unusual and interesting lunar features, as you explore. There are so many images that have been acquired by LRO that in many cases you will be the first person ever to lay eyes on the particular patches of the Moon you examine—you might even run across something remarkable, like a derelict lunar robot from the 1960s (it's happened!). Best of all, your work will count, your data feeding into a growing database from Moon Zoo explorers all over the world.

A sibling site to Moon Zoo—Galaxy Zoo—lets you examine and classify galaxies imaged by the Hubble Space Telescope. And since there are millions upon millions of unclassified galaxies that have been caught in Hubble's telescopic net, you'll be covering unexplored territories of space and contributing to our planet's understanding of the Universe….

There's a lot of work to do out there, and the glittering treasure trove of data just keeps getting larger and larger—so get to work!

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Composite image showing centers of urban light emission
Credit: NASAWant a chance to do some "citizen" science, contribute to an international investigation, and have some fun to boot? An opportunity is coming up in March: Globe At Night. All you need is your eyes….

The problem is summed up in two words: light pollution. A good deal of light produced by human civilization–streetlights, porch lights, shopping malls, security lighting, night time work lights, store fronts, parking lot lights, billboards, neon signs, the list is lengthy–shines or reflects upward into the atmosphere, there scattering off of suspended particles, like dust grains, water droplets, ice crystals and the like.

The scattered light shines back down from the sky, and we see it as a dull nocturnal glow, sometime faint, and sometimes quite pronounced. The amount of scattering particles in the air has an effect on the brightness of the night sky, but the root of the matter is the amount of light sources whose light escapes upward. The closer you are to the heart of an urban area, the more light pollution you will be subjected to.

So what? What's so harmful about that sky glow? Sometimes it can even look kind of pretty….

Well, the fact is, if you've never seen a clear night sky far from sources of major light pollution, you may not appreciate what you're missing: the sight of a clear and dark night sky in which you can literally see thousands of stars. And if you have seen a pristinely dark night sky before, think about the fact that, in 2008, half the population of the Earth was living in cities, many of whom may never have been out of their urban worlds, and for whom the night sky is naturally a dull version of day with a handful of washed out stars above.

There are also effects of light pollution on wildlife that include disturbance of day/night sleep cycles, less cover of darkness from predators, and even effects on plant life.

Globe At Night is a program that's been going on for a few years now whose aim is to measure and monitor the varying levels of light pollution around the world by using individual people as the instruments of measurement.

And it's pretty simple to participate in. The idea is that the brighter the light pollution is in any given location, the few stars you can see. The faintest stars quickly become drowned out in the sky glow, leaving only the brighter ones for your eyes to pick out. All you have to do is go outside on one or more nights in the last half of March, find the constellation Orion (which is pretty easy to find, even in a city), and count the number of stars you see there. Then, report your count through the Globe At Night website, where you'll also be able to see the observations of everyone else around the world, as well as find full instructions for participating.

Now, calendars marked? Know where Orion is? Have a sweater handy? You're all set….

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The Milky Way in the skies of Death Valley's
Devil's Racetrack. Credit: Dan Duriscoe, U.S. National
Park ServiceI just got back from my semi-yearly pilgrimage to my favorite spot on Earth: Death Valley National Park. My main reasons for returning to this place again and again have mostly to do with hiking in the stunning natural beauty of the place, reconnecting with good times in my childhood, and reflecting spiritually on life, the Universe, and everything.

But, I can't go to a place like that and not feel more connected with outer space. Not only is the night sky a celestial spectacle–but it's darned cold there too, this time of year! Cold, like space. Each turn of the Earth through its own shadow is like a quick dip in the icy pool of space….

After twilight had faded, after the campfire had burned to embers–and as the frigid cold of the desert winter night started seeping through my layers of clothing–I lay down on the picnic bench and raised my binoculars to my eyes…

…and that's all I had to do. Arcing overhead was the section of the Milky Way around the constellations Cassiopeia, Perseus, Andromeda, Pegasus–a section of the sky rich in a variety of "deep sky" objects (objects typically only visible through binoculars or telescopes).

There was the Double Cluster in Perseus–a pair of "open" clusters of stars.

Open clusters are stars bound together gravitationally, still clinging to each other after their "group infancy" in the gaseous cloud that gave birth to them. Stars in these clusters are young–and because of their youth, open clusters often contain a number of large, bright, blue stars that shine brilliantly–but which have short life spans as stars go, being more prolific hydrogen-burners (gas guzzlers). (In a word, you can't find an old blue giant star.)

You can't avoid seeing open clusters in this region; the place is positively littered with them….

This is also where the famous Andromeda Galaxy can be found, in the constellation Andromeda (where else?). What's special about the Andromeda Galaxy? For one, it's the closest large galaxy to our own, as well as the most distant object in the Universe that can be seen with the unaided human eye (without telescopic help). Looking at the Andromeda is like looking through a peephole into the realm beyond our Milky Way…

I could go on and on yakking about what I got to see in the clear, dark Death Valley skies last week, so I'll have to stop myself now. Suffice to say that with a dark sky, a pair of binoculars, and a segment of the Milky Way in view, encountering the celestial wonders of the Universe in a very personal way is like shooting ducks in a barrel.

But don't let the light polluted skies of the Bay Area stop you from trying it from your own backyard; there's a lot to behold despite the city lights…

Benjamin Burress is a staff astronomer at The Chabot Space & Science Center in Oakland, CA.