One-Third of Humanity Can't See the Milky Way Anymore

The Milky Way over Mitten Park and the Green River in Dinosaur National Monument, one of the darkest places in the United States. The galaxy we call home is a sight one-third of humanity can no longer see. Image credit: Dan Duriscoe

The view of an ink-black, star-studded night sky is becoming a rarity—something only a small fraction of humanity can hope to experience, according to the most detailed study of light pollution compiled so far. “Light pollution” refers to the stray light from vehicles, homes, and industry—a form of pollution that’s often overlooked, but which has been on the rise ever since the invention of electric lighting. It now hampers the view of the night sky for the majority of people around the world. According to an international team of scientists, more than 80 percent of the world’s population now live under light-polluted skies. A smaller fraction—about one-third—live under skies that are murky enough to blot out the Milky Way. A summary of their findings was published today in the journal Science Advances.

Although long decried by both professional and amateur astronomers, the effects of unchecked light pollution also threaten to affect our lives and our environment in ways that impact more than just astronomy, according to the project’s lead scientist.

“Life on earth evolved over millions of years, and normally, it’s been light for half the time, during the day, and dark for half the time, at night,” lead author Fabio Falchi, of the Light Pollution Science and Technology Institute in Italy, tells mental_floss. “But in the last few decades, things have changed. Now, over large parts of our planet, we have light all day and also all night.”

Europe, Africa, the Middle East, and India in New World Atlas of Artificial Sky Brightness, as seen in Google Earth. Image credit: Falchi et al. in Science Advances

The extra light can have adverse health effects on humans and other animals, Falchi says, by affecting the production of melatonin, a hormone that helps regulate the circadian rhythms that control the sleep-wake cycle.

Falchi and his colleagues have released an updated and expanded edition of a light pollution atlas they first published more than a decade ago. The New World Atlas of Artificial Sky Brightness was compiled by correlating data from NASA’s Suomi NPP satellite (National Polar-orbiting Partnership) together with some 30,000 ground-based light-level measurements. The result is the most accurate assessment yet of the worldwide effects of light pollution. 

While other kinds of pollution, such as air and water pollution, often take the heaviest tolls in the developing world, light pollution is most pronounced in well-off regions, such as the United States, Europe, and parts of Asia. Some 99 percent of Americans and Europeans live under light polluted skies, the study found. In contrast, in the African nations of Chad, the Central African Republic, and Madagascar, some three-quarters of residents still live under dark skies. In the developed world, some of the darkest skies are found in Canada and Australia. 

Light pollution over Joshua Tree National Park. And yet—as the National Park Service says—the park has some of the darkest skies in southern California. Image credit: Dan Duriscoe

The good news, says Falchi, is that fairly simple measures can be taken to mitigate light pollution. For example, street lights can be equipped with shields that minimize the amount of light that escapes upward. And modern LED lighting can be dimmed more easily than older kinds of lights, allowing them to shine at reduced brightness levels when that’s all that’s needed.

Alan Dyer, a Canadian photographer known for his stunning portraits of the night sky, compares a dark sky to an endangered species of animal—a rare treat which, for some people, is worth traveling a great distance to see. “When you lose contact with the night sky, you really lose contact with your place in the universe,” Dyer tells mental_floss. “There’s nothing in nature that inspires more curiosity, wonder, and awe than looking up at the stars, and particularly the Milky Way.” Based in rural Alberta, Dyer has easier access to dark skies than most North Americans, but over the last 25 years, he’s seen the lights of Calgary, as well as smaller towns, steadily getting brighter.

For Falchi, who lives near Milan in northern Italy, a dark night sky is virtually impossible to find. “A really good night sky is no longer available in Italy,” he says. “I can drive two hours to a fairly good mountain site, but even there, there’s some light pollution.” A few more hours gets him close to the Austrian border, which is darker still, but even there, he notes, the sky is only really dark directly overhead. When he looks southward, toward Italy’s industrial region, an orange glow looms above the horizon. 

Joe Raedle, Getty Images
Why Scientists Are Hunting Down Iguanas in Florida
Joe Raedle, Getty Images
Joe Raedle, Getty Images

In South Florida, iguanas had better watch their backs. That's because scientists are on an unusual hunt to kill them, with the help of captive bolt guns and a $63,000 research grant, according to the Sun Sentinel.

It's not as cruel as it might seem at first glance. The green iguana, native to Central and South America, is an invasive species in Florida. The large lizards—which can grow up to 6 feet long—first made it to Florida in the 1960s, and as their population has exploded, they have expanded farther north. The reptiles damage roads, sidewalks, sea walls, and flood-control canals with their burrows; chomp their way through landscaping; spread Salmonella, largely by pooping in people's backyard pools; and compete with the endangered Miami blue butterfly for precious food resources.

The population boom has caused an uptick in complaints from residents, Florida Fish and Wildlife's Sarah Funck told the Sun Sentinel in 2017, pushing the state to find new strategies to deal with the reptiles. One approach? Hire scientists to hunt them down and kill them.

As part of the Florida Fish and Wildlife research project, 15 University of Florida biologists have been tasked with executing as many iguanas as possible in Broward County (home to Fort Lauderdale and parts of the Miami metropolitan area), setting out in teams of two at night. Armed with flashlights and captive bolt guns—which are often used on animals in slaughterhouses and are considered a humane way of killing an animal instantly and painlessly—the researchers attempt to sneak up on sleeping lizards and shoot them before they can scurry away. They also sometimes dispatch the iguanas by smashing their heads against a hard surface, including the side of a truck or a boat.

They've exterminated 249 lizards so far. They take the dead animals back to the lab to be weighed and measured for their dataset, then deposit the carcasses in a landfill. The iguana killing spree is expected to last into May.

While they have tried trapping the iguanas in county parks, they haven't succeeded in capturing any with that method.

As part of the Fish and Wildlife Conservation Commission's iguana-eradicating efforts, the agency has also been hosting public workshops on how to deter and trap iguanas and has hired a dedicated trapper to control populations on public lands in the Florida Keys. 

[h/t Sun Sentinel]

©AMNH/R. Mickens
7 Technologies That Are Revolutionizing Ocean Exploration
©AMNH/R. Mickens
©AMNH/R. Mickens

The Earth is an ocean planet—more than 70 percent of the surface is covered by seawater. But despite being such an essential part of life, the deepest parts of the world's oceans are still largely unexplored. According to the American Museum of Natural History in New York, merely 10 to 15 percent of the seafloor has been mapped with accuracy, which means we know less about the seafloor than the surface of Mars.

But the state of sea exploration is changing fast. The dark, high-pressure conditions of the ocean depths that once made research there impossible are now being explored with cutting-edge technology. That new tech and the discoveries to come from it are the focus of a new exhibition at the American Museum of Natural History called Unseen Oceans. As museum curator John Sparks said at a press preview, the goal of the exhibition is to show visitors "how little we know, and to tell them how much we're learning so rapidly with technology."

Here are some of the technologies featured in the exhibition, which opens March 12.


One of the biggest recent discoveries made in the field of deep ocean exploration is the proliferation of biofluorescence in the darkest parts of the sea. Realms that look pitch black to human eyes are actually filled with more than 250 species of fish glowing in red, orange, and green hues. One of these species is the catshark, which fluoresces green in the dim blue light that reaches the sea floor. To detect this effect, researchers built a camera that filters out certain wavelengths of light like the shark's eye does. (This is how the sharks see each other in the darkness.) Combined with artificial blue light to enhance the fluorescent color, this equipment allows scientists to record the light show.


Listening to whales vocalize tells us a lot about the way they live and interact, but this is difficult to do when a species spends most of its time in the deep ocean. In order to eavesdrop on beaked whales, scientists needed to fit sophisticated acoustic equipment into a submersible built to explore high-pressure environments. Enter the Deep Ocean REMUS Echosounder, or DOR-E. (REMUS stands for "Remote Environmental Monitoring UnitS.") Developed by marine scientist Kelly Benoit-Bird and her team at the Monterey Bay Aquarium Research Institute, the autonomous underwater vehicle can reach depths up to 1970 feet and has enough battery life to record a day's worth of deep-sea audio. The device was named for Finding Nemo's Dory because it "speaks whale," according to Unseen Oceans.


Family looking at museum exhibit
©AMNH/D. Finnin

Collecting specimens at the bottom of the ocean isn't as simple as collecting them on land; researchers can't just step out of their submersible to pick up a mollusk from the seabed. The only way to retrieve a sample at such depths is with a machine. When these machines are designed to be bulky and rigid to withstand the intense water pressure around them, they can end up crushing the specimen before scientists have the chance to study it. So-called soft grippers are a clever alternative. Memory foam evenly distributes the force around the creature being handled, and Kevlar lace keeps the fingers from spreading when they inflate with water. Even with its squishy construction, the mechanism is sturdy enough to work at depths reaching 1000 feet.


A remotely operated vehicle (ROV) can explore the tight, crushing pockets of the ocean that human divers can't reach. This technology is often costly and limited to research teams with big budgets. A new company called OpenROV aims to make underwater drones more accessible to everyday explorers. Their signature ROV, Trident, starts at just $1500.


Topography exhibit in museum.
©AMNH/D. Finnin

Sometimes the easiest way for scientists to get a view of the bottom of the ocean is by sending equipment to space. Satellites in orbit can estimate measurements of the peaks and valleys shaping the seabed by beaming radar pulses towards Earth and calculating the time it takes for them to bounce back. While this method doesn't provide a terribly accurate map of the ocean floor, it can be used to gauge depths in even the most remote areas.


Autonomous undersea robots come in all shapes and sizes. Mini-autonomous underwater explorers, or m-AUEs, developed by Scripps oceanographer Jules Jaffe are meant to be deployed in large groups or "swarms." The grapefruit-sized devices act like plankton, bobbing at a constant depth in the ocean and measuring factors like water temperature. By studying the underwater explorers, scientists hope to better understand how plankton, major contributors of the Earth's oxygen, thrive and travel through the sea.


Kids looking at museum exhibit.
©AMNH/R. Mickens

This technology is so new, it hasn't hit the water yet. Once it's ocean-ready, researchers plan to attach the miniature suction cups to the bells of jellies. The device automatically measures a jelly's movements and ocean chemistry as the animal swims around. Eventually the jelly regenerates the top layer of its bell, shedding the tag and moving on unharmed. Once detached, the tag floats to the water's surface where it alerts scientists to its location via a VHF antenna and green reflective tape.


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