After being passed up for the honor last year, three scientists who made essential contributions to the LIGO collaboration have been awarded the 2017 Nobel Prize in Physics.

Rainer Weiss will share the prize with Kip Thorne and Barry Barish for their roles in the discovery of gravitational waves, ripples in space-time predicted by Albert Einstein. Weiss and Thorne conceived of the experiment, and project manager Barish is credited with reviving the struggling experiment and making it happen.

“I view this more as a thing that recognizes the work of about 1000 people,” Weiss said during a Q&A after the announcement this morning. “It’s really a dedicated effort that has been going on, I hate to tell you, for as long as 40 years, people trying to make a detection in the early days and then slowly but surely getting the technology together to do it.”

A third founder of LIGO, scientist Ronald Drever, died in March. Nobel Prizes are not awarded posthumously.

According to Einstein’s general theory of relativity, powerful cosmic events release energy in the form of waves traveling through the fabric of existence at the speed of light. LIGO detects these disturbances when they disrupt the symmetry between the passages of identical laser beams traveling identical distances.

The setup for the LIGO experiment looks like a giant L, with each side stretching about 2.5 miles long. Scientists split a laser beam and shine the two halves down the two sides of the L. When each half of the beam reaches the end, it reflects off a mirror and heads back to the place where its journey began.

Normally, the two halves of the beam return at the same time. When there’s a mismatch, scientists know something is going on. Gravitational waves compress space-time in one direction and stretch it in another, giving one half of the beam a shortcut and sending the other on a longer trip. LIGO is sensitive enough to notice a difference between the arms as small as 1000^th the diameter of an atomic nucleus.

Scientists on LIGO and their partner collaboration, called Virgo, reported the first detection of gravitational waves in February 2016. The waves were generated in the collision of two black holes with 29 and 36 times the mass of the sun 1.3 billion years ago. They reached the LIGO experiment as scientists were conducting an engineering test.

“It took us a long time, something like two months, to convince ourselves that we had seen something from outside that was truly a gravitational wave,” Weiss said.

LIGO, which stands for Laser Interferometer Gravitational-Wave Observatory, consists of two of these pieces of equipment, one located in Louisiana and another in Washington state. The experiment is operated jointly by MIT, Weiss’s home institution, and Caltech, home institution for Barish and Thorne. The experiment has collaborators from more than 80 institutions from more than 20 countries. A third interferometer, operated by Virgo, recently joined LIGO to make the first joint observation of gravitational waves.

Browsing YouTube late at night, Fermilab Technical Specialist Derek Plant stumbled on a series of videos that all begin the same way: a large vehicle—a bus, semi or other low-clearance vehicle—is stuck on a railroad crossing. In the end, the train crashes into the stuck vehicle, destroying it and sometimes even derailing the train. According to the Federal Railroad Administration, every year hundreds of vehicles meet this fate by trains, which can take over a mile to stop.

“I was just surprised at the number of these that I found,” Plant says. “For every accident that’s videotaped, there are probably many more.”

Inspired by a workplace safety class that preached a principle of minimizing the impact of accidents, Derek set about looking for solutions to the problem of trains hitting stuck vehicles.

Railroad tracks are elevated for proper drainage, and the humped profile of many crossings can cause a vehicle to bottom out. “Theoretically, we could lower all the crossings so that they’re no longer a hump. But there are 200,000 crossings in the United States,” Plant says. “Railroads and local governments are trying hard to minimize the number of these crossings by creating overpasses, or elevating roadways. That’s cost-prohibitive, and it’s not going to happen soon.”

Other solutions, such as re-engineering the suspension on vehicles likely to get stuck, seemed equally improbable.

After studying how railroad signaling systems work, Plant came up with an idea: to fake the presence of a train. His invention was developed in his spare time using techniques and principles he learned over his almost two decades at Fermilab. It is currently in the patent application process and being prosecuted by Fermilab’s Office of Technology Transfer.

“If you cross over a railroad track and you look down the tracks, you’ll see red or yellow or green lights,” he says. “Trains have traffic signals too.”

These signals are tied to signal blocks—segments of the tracks that range from a mile to several miles in length. When a train is on the tracks, its metal wheels and axle connect both rails, forming an electric circuit through the tracks to trigger the signals. These signals inform other trains not to proceed while one train occupies a block, avoiding pileups.

Plant thought, “What if other vehicles could trigger the same signal in an emergency?” By faking the presence of a train, a vehicle stuck on the tracks could give advanced warning for oncoming trains to stop and stall for time. Hence the name of Plant’s invention: the Ghost Train Generator.

To replicate the train’s presence, Plant knew he had to create a very strong electric current between the rails. The most straightforward way to do this is with massive amounts of metal, as a train does. But for the Ghost Train Generator to be useful in a pinch, it needs to be small, portable and easily applied. The answer to achieving these features lies in strong magnets and special wire.

“Put one magnet on one rail and one magnet on the other and the device itself mimics—electrically—what a train would look like to the signaling system,” he says. “In theory, this could be carried in vehicles that are at high risk for getting stuck on a crossing: semis, tour buses and first-response vehicles,” Plant says. “Keep it just like you would a fire extinguisher—just behind the seat or in an emergency compartment.”

Once the device is deployed, the train would receive the signal that the tracks were obstructed and stop. Then the driver of the stuck vehicle could call for emergency help using the hotline posted on all crossings.

Plant compares the invention to a seatbelt.

“Is it going to save your life 100 percent of the time? Nope, but smart people wear them,” he says. “It’s designed to prevent a collision when a train is more than two minutes from the crossing.”

And like a seatbelt, part of what makes Plant’s invention so appealing is its simplicity.

“The first thing I thought was that this is a clever invention,” says Aaron Sauers from Fermilab’s technology transfer office, who works with lab staff to develop new technologies for market. “It’s an elegant solution to an existing problem. I thought, ‘This technology could have legs.’”

The organizers of the National Innovation Summit seem to agree.  In May, Fermilab received an Innovation Award from TechConnect for the Ghost Train Generator. The invention will also be featured as a showcase technology in the upcoming Defense Innovation Summit in October.

The Ghost Train Generator is currently in the pipeline to receive a patent with help from Fermilab, and its prospects are promising, according to Sauers. It is a nonprovisional patent, which has specific claims and can be licensed. After that, if the generator passes muster and is granted a patent, Plant will receive a portion of the royalties that it generates for Fermilab.

Fermilab encourages a culture of scientific innovation and exploration beyond the field of particle physics, according to Sauers, who noted that Plant’s invention is just one of a number of technology transfer initiatives at the lab.

Plant agrees—Fermilab’s environment helped motivate his efforts to find a solution for railroad crossing accidents.

“It’s just a general problem-solving state of mind,” he says. “That’s the philosophy we have here at the lab.”

Editor's note: A version of this article was originally published by Fermilab.

Fermi National Accelerator Laboratory’s yearlong 50th anniversary celebration culminated on Saturday with an Open House that drew thousands of visitors despite the unseasonable heat.

On display were areas of the lab not normally open to guests, including neutrino and muon experiments, a portion of the accelerator complex, lab spaces and magnet and accelerator fabrication and testing areas, to name a few. There were also live links to labs around the world, including CERN, a mountaintop observatory in Chile, and the mile-deep Sanford Underground Research Facility that will house the international neutrino experiment, DUNE.

But it wasn’t all physics. In addition to hands-on demos and a STEM fair, visitors could also learn about Fermilab’s art and history, walk the prairie trails or hang out with the ever-popular bison. In all, some 10,000 visitors got to go behind-the-scenes at Fermilab, shuttled around on 80 buses and welcomed by 900 Fermilab workers eager to explain their roles at the lab. Below, see a few of the photos captured as Fermilab celebrated 50 years of discovery.

Early in the morning, physicist Roy Beck Barkai boards a bus in Tel Aviv bound for Jordan. By 10:30 a.m., he is on site at SESAME, a new scientific facility where scientists plan to use light to study everything from biology to archaeology. He is back home by 7 p.m., in time to have dinner with his children.

Before SESAME opened, the closest facility like it was in Italy. Beck Barkai often traveled for two days by airplane, train and taxi for a day or two of work—an inefficient and expensive process that limited his ability to work with specialized equipment from his home lab and required him to spend days away from his family.  

“For me, having the ability to kiss them goodbye in the morning and just before they went to sleep at night is a miracle,” Beck Barkai says. “It felt like a dream come true. Having SESAME at our doorstep is a big plus."

SESAME, also known as the International Centre for Synchrotron-Light for Experimental Science and Applications in the Middle East, opened its doors in May and is expected to host its first beams of particles this year. Scientists from around the world will be able to apply for time to use the facility’s powerful light source for their experiments. It’s the first synchrotron in the region and the first international research center in the Middle East. 

Beck Barkai says SESAME provides a welcome dose of convenience, as scientists in the region can now drive to a research center instead of flying with sensitive equipment to another country. It’s also more cost-effective.

Located in Jordan to the northwest of the city of Amman, SESAME was built by a collaboration made up of the countries of Cyprus, Egypt, Iran, Israel, Jordan, Pakistan, Turkey and the Palestinian Authority—a partnership members hope will improve relations among the eight neighbors.

“SESAME is a very important step in the region,” says SESAME Scientific Advisory Committee Chair Zehra Sayers. “The language of science is objective. It’s based on curiosity. It doesn’t need to be affected by the differences in cultural and social backgrounds in these countries. I hope it is something that we will leave the next generations as a positive step toward stability.”

Protein researcher and a University of Jordan professor Areej Abuhammad says she hopes SESAME will provide an environment that encourages collaboration. 

“I think through having the chance to interact, the scientists from around this region will learn to trust and respect each other,” she says. “I don’t think that this will result in solving all the problems in the region from one day to the next, but it will be a big step forward.”

The $100 million center is a state-of-the-art research facility that should provide some relief to scientists seeking time at other, overbooked facilities. SESAME plans to eventually host 100 to 200 users at a time. 

SESAME’s first two beamlines will open later this year. About twice per year, SESAME will announce calls for research proposals, the next of which is expected for this fall. Sayers says proposals will be evaluated for originality, preparedness and scientific quality. 

Groups of researchers hoping to join the first round of experiments submitted more than 50 applications. Once the lab is at full operation, Sayers says, the selection committee expects to receive four to five times more than that.

Opening up a synchrotron in the Middle East means that more people will learn about these facilities and have a chance to use them. Because some scientists in the region are new to using synchrotrons or writing the style of applications SESAME requires, Sayers asked the selection committee to provide feedback with any rejections. 

Abuhammad is excited for the learning opportunity SESAME presents for her students—and for the possibility that experiences at SESAME will spark future careers in science. 

She plans to apply for beam time at SESAME to conduct protein crystallography, a field that involves peering inside proteins to learn about their function and aid in pharmaceutical drug discovery. 

Another scientist vying for a spot at SESAME is Iranian chemist Maedeh Darzi, who studies the materials of ancient manuscripts and how they degrade. Synchrotrons are of great value to archaeologists because they minimize the damage to irreplaceable artifacts. Instead of cutting them apart, scientists can take a less damaging approach by probing them with particles. 

Darzi sees SESAME as a chance to collaborate with scientists from other Middle Eastern countries and promote science, peace and friendship. For her and others, SESAME could be a place where particles put things back together.

Particle accelerators are the engines of particle physics research at Fermi National Accelerator Laboratory. They generate nearly light-speed, subatomic particles that scientists study to get to the bottom of what makes our universe tick. Fermilab experiments rely on a number of different accelerators, including a powerful, 500-foot-long linear accelerator that kick-starts the process of sending particle beams to various destinations.

But if you’re not doing physics research, what’s an accelerator good for?

It turns out, quite a lot: Electron beams generated by linear accelerators have all kinds of practical uses, such as making the wires used in cars melt-resistant or purifying water.

A project called Accelerator Application Development and Demonstration (A2D2) at Fermilab’s Illinois Accelerator Research Center will help Fermilab and its partners to explore new applications for compact linear accelerators, which are only a few feet long rather than a few hundred. These compact accelerators are of special interest because of their small size—they’re cheaper and more practical to build in an industrial setting than particle physics research accelerators—and they can be more powerful than ever.

“A2D2 has two aspects: One is to investigate new applications of how electron beams might be used to change, modify or process different materials,” says Fermilab’s Tom Kroc, an A2D2 physicist. “The second is to contribute a little more to the understanding of how these processes happen.”

To develop these aspects of accelerator applications, A2D2 will employ a compact linear accelerator that was once used in a hospital to treat tumors with electron beams. With a few upgrades to increase its power, the A2D2 accelerator will be ready to embark on a new venture: exploring and benchmarking other possible uses of electron beams, which will help specify the design of a new, industrial-grade, high-power machine under development by IARC and its partners.

It won’t be just Fermilab scientists using the A2D2 accelerator: As part of IARC, the accelerator will be available for use (typically through a formal CRADA or SPP agreement) by anyone who has a novel idea for electron beam applications. IARC’s purpose is to partner with industry to explore ways to translate basic research and tools, including accelerator research, into commercial applications.

“I already have a lot of people from industry asking me, ‘When can I use A2D2?’” says Charlie Cooper, general manager of IARC. “A2D2 will allow us to directly contribute to industrial applications—it’s something concrete that IARC now offers.”

Speaking of concrete, one of the first applications in mind for compact linear accelerators is creating durable pavement for roads that won’t crack in the cold or spread out in the heat. This could be achieved by replacing traditional asphalt with a material that could be strengthened using an accelerator. The extra strength would come from crosslinking, a process that creates bonds between layers of material, almost like applying glue between sheets of paper. A single sheet of paper tears easily, but when two or more layers are linked by glue, the paper becomes stronger.

“Using accelerators, you could have pavement that lasts longer, is tougher and has a bigger temperature range,” says Bob Kephart, director of IARC. Kephart holds two patents for the process of curing cement through crosslinking. “Basically, you’d put the road down like you do right now, and you’d pass an accelerator over it, and suddenly you’d turn it into really tough stuff—like the bed liner in the back of your pickup truck.”

This process has already caught the eye of the U.S. Army Corps of Engineers, which will be one of A2D2’s first partners. Another partner will be the Chicago Metropolitan Water Reclamation District, which will test the utility of compact accelerators for water purification. Many other potential customers are lining up to use the A2D2 technology platform.

“You can basically drive chemical reactions with electron beams—and in many cases those can be more efficient than conventional technology, so there are a variety of applications,” Kephart says. “Usually what you have to do is make a batch of something and heat it up in order for a reaction to occur. An electron beam can make a reaction happen by breaking a bond with a single electron.”

In other words, instead of having to cook a material for a long time to reach a specific heat that would induce a chemical reaction, you could zap it with an electron beam to get the same effect in a fraction of the time.

In addition to exploring the new electron-beam applications with the A2D2 accelerator, scientists and engineers at IARC are using cutting-edge accelerator technology to design and build a new kind of portable, compact accelerator, one that will take applications uncovered with A2D2 out of the lab and into the field. The A2D2 accelerator is already small compared to most accelerators, but the latest R&D allows IARC experts to shrink the size while increasing the power of their proposed accelerator even further.

“The new, compact accelerator that we’re developing will be high-power and high-energy for industry,” Cooper says. “This will enable some things that weren’t possible in the past. For something such as environmental cleanup, you could take the accelerator directly to the site.”

While the IARC team develops this portable accelerator, which should be able to fit on a standard trailer, the A2D2 accelerator will continue to be a place to experiment with how to use electron beams—and study what happens when you do.

“The point of this facility is more development than research, however there will be some research on irradiated samples,” says Fermilab’s Mike Geelhoed, one of the A2D2 project leads. “We’re all excited—at least I am. We and our partners have been anticipating this machine for some time now. We all want to see how well it can perform.”

Editor's note: This article was originally published by Fermilab.

Science stories usually catch the eye when there’s big news: the discovery of gravitational waves, the appearance of a new particle. But behind the blockbusters are the thousands of smaller stories of science behind the scenes and daily life at a research institution. 

As the Department of Energy’s Fermi National Accelerator Laboratory celebrates its 50th anniversary year, employees past and present have shared memories of building a lab dedicated to particle physics.

Some shared personal memories: keeping an accelerator running during a massive snowstorm; being too impatient for the arrival of an important piece of detector equipment to stay put and wait for it to arrive; accidentally complaining about the lab to the lab’s director.

Others focused on milestones and accomplishments: the first daycare at a national lab, the Saturday Morning Physics Program built by Nobel laureate Leon Lederman, the birth of the web at Fermilab.

People shared memories of big names that built the lab: charismatic founding director Robert R. Wilson, fiery head of accelerator development Helen Edwards, talented lab artist Angela Gonzales.

And or course, employees told stories about Fermilab’s resident herd of bison.

There are many more stories to peruse. You can watch a playlist of the video anecdotes or find all of the stories (both written and video) collected on Fermilab’s 50th anniversary website.

In a project called SENSEI, scientists are using innovative sensors developed over three decades to look for the lightest dark matter particles anyone has ever tried to detect.

Dark matter—so named because it doesn’t absorb, reflect or emit light—constitutes 27 percent of the universe, but the jury is still out on what it’s made of. The primary theoretical suspect for the main component of dark matter is a particle scientists have descriptively named the weakly interactive massive particle, or WIMP.

But since none of these heavy particles, which are expected to have a mass 100 times that of a proton, have shown up in experiments, it might be time for researchers to think small.

“There is a growing interest in looking for different kinds of dark matter that are additives to the standard WIMP model,” says Fermi National Accelerator Laboratory scientist Javier Tiffenberg, a leader of the SENSEI collaboration. “Lightweight, or low-mass, dark matter is a very compelling possibility, and for the first time, the technology is there to explore these candidates.”

Sensing the unseen

In traditional dark matter experiments, scientists look for a transfer of energy that would occur if dark matter particles collided with an ordinary nucleus. But SENSEI is different; it looks for direct interactions of dark matter particles colliding with electrons.

“That is a big difference—you get a lot more energy transferred in this case because an electron is so light compared to a nucleus,” Tiffenberg says.

If dark matter had low mass—much smaller than the WIMP model suggests—then it would be many times lighter than an atomic nucleus. So if it were to collide with a nucleus, the resulting energy transfer would be far too small to tell us anything. It would be like throwing a ping-pong ball at a boulder: The heavy object wouldn’t go anywhere, and there would be no sign the two had come into contact.

An electron is nowhere near as heavy as an atomic nucleus. In fact, a single proton has about 1836 times more mass than an electron. So the collision of a low-mass dark matter particle with an electron has a much better chance of leaving a mark—it’s more bowling ball than boulder.

Bowling balls aren't exactly light, though. An energy transfer between a low-mass dark matter particle and an electron would leave only a blip of energy, one either too small for most detectors to pick up or easily overshadowed by noise in the data.

“The bowling ball will move a very tiny amount,” says Fermilab scientist Juan Estrada, a SENSEI collaborator. “You need a very precise detector to see this interaction of lightweight particles with something that is much heavier.”

That’s where SENSEI’s sensitive sensors come in.

SENSEI will use skipper charge-couple devices, also called skipper CCDs. CCDs have been used for other dark matter detection experiments, such as the Dark Matter in CCDs (or DAMIC) experiment operating at SNOLAB in Canada. These CCDs were a spinoff from sensors developed for use in the Dark Energy Camera in Chile and other dark energy search projects.

CCDs are typically made of silicon divided into pixels. When a dark matter particle passes through the CCD, it collides with the silicon’s electrons, knocking them free, leaving a net electric charge in each pixel the particle passes through. The electrons then flow through adjacent pixels and are ultimately read as a current in a device that measures the number of electrons freed from each CCD pixel. That measurement tells scientists about the mass and energy of the particle that got the chain reaction going. A massive particle, like a WIMP, would free a gusher of electrons, but a low-mass particle might free only one or two.

Typical CCDs can measure the charge left behind only once, which makes it difficult to decide if a tiny energy signal from one or two electrons is real or an error.

Skipper CCDs are a new generation of the technology that helps eliminate the “iffiness” of a measurement that has a one- or two-electron margin of error. “The big step forward for the skipper CCD is that we are able to measure this charge as many times as we want,” Tiffenberg says.

The charge left behind in the skipper CCD can be sampled multiple times and then averaged, a method that yields a more precise measurement of the charge deposited in each pixel than the measure-one-and-done technique. That’s the rule of statistics: With more data, you get closer to a property’s true value.

SENSEI scientists take advantage of the skipper CCD architecture, measuring the number of electrons in a single pixel a whopping 4000 times.

“This is a simple idea, but it took us 30 years to get it to work,” Estrada says.

From idea to reality to beyond

A small SENSEI prototype is currently running at Fermilab in a detector hall 385 feet below ground, and it has demonstrated that this detector design will work in the hunt for dark matter.

Skipper CCD technology and SENSEI were brought to life by Laboratory Directed Research and Development (LDRD) funds at Fermilab and Lawrence Berkeley National Laboratory (Berkeley Lab). LDRD programs are intended to provide funding for development of novel, cutting-edge ideas for scientific discovery.

The Fermilab LDRDs were awarded only recently—less than two years ago—but close collaboration between the two laboratories has already yielded SENSEI’s promising design, partially thanks to Berkeley lab’s previous work in skipper CCD design.

Fermilab LDRD funds allow researchers to test the sensors and develop detectors based on the science, and the Berkeley Lab LDRD funds support the sensor design, which was originally proposed by Berkeley Lab scientist Steve Holland.

“It is the combination of the two LDRDs that really make SENSEI possible,” Estrada says.

Future SENSEI research will also receive a boost thanks to a recent grant from the Heising-Simons Foundation.

“SENSEI is very cool, but what’s really impressive is that the skipper CCD will allow the SENSEI science and a lot of other applications,” Estrada says. “Astronomical studies are limited by the sensitivity of their experimental measurements, and having sensors without noise is the equivalent of making your telescope bigger—more sensitive.”

SENSEI technology may also be critical in the hunt for a fourth type of neutrino, called the sterile neutrino, which seems to be even more shy than its three notoriously elusive neutrino family members.

A larger SENSEI detector equipped with more skipper CCDs will be deployed within the year. It’s possible it might not detect anything, sending researchers back to the drawing board in the hunt for dark matter. Or SENSEI might finally make contact with dark matter—and that would be SENSEI-tional.

Editor's note: This article is based on an article published by Fermilab.

More than a mile up in the San Gabriel Mountains in Los Angeles County sits the Mount Wilson Observatory, once one of the cornerstones of groundbreaking astronomy. 

Founded in 1904, it was twice home to the largest telescope on the planet, first with its 60-inch telescope in 1908, followed by its 100-inch telescope in 1917. In 1929, Edwin Hubble revolutionized our understanding of the shape of the universe when he discovered on Mt. Wilson that it was expanding. 

But a problem was radiating from below. As the city of Los Angeles grew, so did the reach and brightness of its skyglow, otherwise known as light pollution. The city light overpowered the photons coming from faint, distant objects, making deep-sky cosmology all but impossible. In 1983, the Carnegies, who had owned the observatory since its inception, abandoned Mt. Wilson to build telescopes in Chile instead.

“They decided that if they were going to do greater, more detailed and groundbreaking science in astronomy, they would have to move to a dark place in the world,” says Tom Meneghini, the observatory’s executive director. “They took their money and ran.” 

(Meneghini harbors no hard feelings: “I would have made the same decision,” he says.)

Beyond being a problem for astronomers, light pollution is also known to harm and kill wildlife, waste energy and cause disease in humans around the globe. For their part, astronomers have worked to convince local governments to adopt better lighting ordinances, including requiring the installation of fixtures that prevent light from seeping into the sky. 

Many towns and cities are already reexamining their lighting systems as the industry standard shifts from sodium lights to light-emitting diodes, or LEDs, which last longer and use far less energy, providing both cost-saving and environmental benefits. But not all LEDs are created equal. Different bulbs emit different colors, which correspond to different temperatures. The higher the temperature, the bluer the color. 

The creation of energy-efficient blue LEDs was so profound that its inventors were awarded the 2014 Nobel Prize in Physics. But that blue light turns out to be particularly detrimental to astronomers, for the same reason that the daytime sky is blue: Blue light scatters more than any other color. (Blue lights have also been found to be more harmful to human health than more warmly colored, amber LEDs. In 2016, the American Medical Association issued guidance to minimize blue-rich light, stating that it disrupts circadian rhythms and leads to sleep problems, impaired functioning and other issues.)

The effort to darken the skies has expanded to include a focus on LEDs, as well as an attempt to get ahead of the next industry trend. 

At a January workshop at the annual American Astronomical Society (AAS) meeting, astronomer John Barentine sought to share stories of towns and cities that had successfully battled light pollution. Barentine is a program manager for the International Dark-Sky Association (IDA), a nonprofit founded in 1988 to combat light pollution. He pointed to the city of Phoenix, Arizona. 

Arizona is a leader in reducing light pollution. The state is home to four of the 10 IDA-recognized “Dark Sky Communities” in the United States. “You can stand in the middle of downtown Flagstaff and see the Milky Way,” says James Lowenthal, an astronomy professor at Smith College.

But it’s not immune to light pollution. Arizona’s Grand Canyon National Park is designated by the IDA as an International Dark Sky Park, and yet, on a clear night, Barentine says, the horizon is stained by the glow of Las Vegas 170 miles away.

In 2015, Phoenix began testing the replacement of some of its 100,000 or so old streetlights with LEDs, which the city estimated would save $2.8 million a year in energy bills. But they were using high-temperature blue LEDs, which would have bathed the city in a harsh white light. 

Through grassroots work, the local IDA chapter delayed the installation for six months, giving the council time to brush up on light pollution and hear astronomers’ concerns. In the end, the city went beyond IDA’s “best expectations,” Barentine says, opting for lights that burn at a temperature well under IDA’s maximum recommendations. 

“All the way around, it was a success to have an outcome arguably influenced by this really small group of people, maybe 10 people in a city of 2 million,” he says. “People at the workshop found that inspiring.”

Just getting ordinances on the books does not necessarily solve the problem, though. Despite enacting similar ordinances to Phoenix, the city of Northampton, Massachusetts, does not have enough building inspectors to enforce them. “We have this great law, but developers just put their lights in the wrong way and nobody does anything about it,” Lowenthal says. 

For many cities, a major part of the challenge of combating light pollution is simply convincing people that it is a problem. This is particularly tricky for kids who have never seen a clear night sky bursting with bright stars and streaked by the glow of the Milky Way, says Connie Walker, a scientist at the National Optical Astronomy Observatory who is also on the board of the IDA. “It’s hard to teach somebody who doesn’t know what they’ve lost,” Walker says.

Walker is focused on making light pollution an innate concern of the next generation, the way campaigns in the 1950s made littering unacceptable to a previous generation of kids. 

In addition to creating interactive light-pollution kits for children, the NOAO operates a citizen-science initiative called Globe at Night, which allows anyone to take measurements of brightness in their area and upload them to a database. To date, Globe at Night has collected more than 160,000 observations from 180 countries. 

It’s already produced success stories. In Norman, Oklahoma, for example, a group of high school students, with the assistance of amateur astronomers, used Globe at Night to map light pollution in their town. They took the data to the city council. Within two years, the town had passed stricter lighting ordinances. 

“Light pollution is foremost on our minds because our observatories are at risk,” Walker says. “We should really be concentrating on the next generation.”