Deep within a mountain in Italy, scientists have finished the assembly of an experiment more than one decade in the making. The detector of CUORE, short for Cryogenic Underground Observatory for Rare Events, is ready to be cooled down to its operating temperature for the first time.

Ettore Fiorini, the founder of the collaboration, proposed the use of low temperature detectors to search for rare events in 1984 and started creating the first prototypes with his group in Milano. What began as a personal project involving a tiny crystal and a small commercial cooler has grown to a collaboration of 165 scientists loading almost one ton of crystals and several tons of refrigerator and shields.

The CUORE experiment is looking for a rare process that would be evidence that almost massless particles called neutrinos are their own antiparticles, something that would give scientists a clue as to how our universe came to be.

Oliviero Cremonesi, current spokesperson of the CUORE collaboration, joined the quest in 1988 and helped write the first proposal for the experiment. At first, funding agencies in Italy and the United States approved a smaller version: Cuoricino.

“We had five exciting years of measurements from 2003 to 2008 on this machine, but we knew that we wanted to go bigger. So we kept working on CUORE,” Cremonesi says.

In 2005 the collaboration got approval for the big detector, which they called CUORE. That started them on a whole new journey involving growing crystals in China, bringing them to Italy by boat, and negotiating with archeologists for the right to use 2000-year-old Roman lead as shielding material. 

“I imagine climbing Mount Everest is a little bit like this,” says Lindley Winslow, a professor at the Massachusetts Institute of Technology and group leader of the MIT activities on CUORE. “We can already see the top, but this last part is the hardest. The excitement is high, but also the fear that something goes wrong.”

The CUORE detector, assembled between 2012 and 2014, consists of 19 fragile copper towers that each host 52 tellurium oxide crystals connected by wires and sensors to measure their temperature.

For this final stage, scientists built a custom refrigerator from extremely pure materials. They shielded and housed it inside of a mountain at Gran Sasso, Italy. At the end of July, scientists began moving the detector to its new home. After a brief pause to ensure the site had not been affected by the 6.2-magnitude earthquake that hit central Italy on August 24, they finished the job on August 26.

The towers now reside in the largest refrigerator used for a scientific purpose. By the end of October, they will be cooled below 10 millikelvin (negative 460 Fahrenheit), colder than outer space.

Everything has to be this cold because the scientists are searching for minuscule temperature changes caused by an ultra-rare process. It is predicted to occur only once every trillion trillion years and is called neutrinoless double beta decay.

During a normal beta decay, one atom changes from one chemical element into its daughter element and sends out one electron and one antineutrino. For the neutrinoless double beta decay, this would be different: The element would change into its granddaughter. Instead of one electron and one neutrino sharing the energy of the decay, only two electrons would leave, and an observer would see no neutrinos at all.

This would only happen if neutrinos were their own antiparticles. In that case, the two neutrinos would cancel each other out, and it would seem like they never existed in the first place.

If scientists measure this decay, it would change the current scientific thinking about the neutrino and give scientists clues about why there is so much more matter than anti-matter in the universe.  

“We are excited to start the cool-down, and if everything works according to plan, we can start measuring at the beginning of next year,” Winslow says.

Astronomers think the universe might be expanding faster than expected.

If true, it could reveal an extra wrinkle in our understanding of the universe, says Nobel Laureate Adam Riess of the Space Telescope Science Institute and Johns Hopkins University. That wrinkle might point toward new particles or suggest that the strength of dark energy, the mysterious force accelerating the expansion of the universe, actually changes over time.

The result appears in a study published in The Astrophysical Journal this July, in which Riess’s team measured the current expansion rate of the universe, also known as the Hubble constant, better than ever before.

In theory, determining this expansion is relatively simple, as long as you know the distance to a galaxy and the rate at which it is moving away from us. But distance measurements are tricky in practice and require using objects of known brightness, so-called standard candles, to gauge their distances.

The use of Type Ia supernovae—exploding stars that shine with the same intrinsic luminosity—as standard candles led to the discovery that the universe was accelerating in the first place and earned Riess, as well as Saul Perlmutter and Brian Schmidt, a Nobel Prize in 2011.

The latest measurement builds on that work and indicates that the universe is expanding by 73.2 kilometers per second per megaparsec (a unit that equals 3.3 million light-years). Think about dividing the universe into grids that are each a megaparsec long. Every time you reach a new grid, the universe is expanding 73.2 kilometers per second faster than the grid before.

Although the analysis pegs the Hubble constant to within experimental errors of just 2.4 percent, the latest result doesn’t match the expansion rate predicted from the universe’s trajectory. Here, astronomers measure the expansion rate from the radiation released 380,000 years after the Big Bang and then run that expansion forward in order to calculate what today’s expansion rate should be.

It’s similar to throwing a ball in the air, Riess says. If you understand the state of the ball (how fast it's traveling and where it is) and the physics (gravity and drag), then you should be able to precisely predict how fast that ball is traveling later on.

“So in this case, instead of a ball, it's the whole universe, and we think we should be able to predict how fast it's expanding today,” Riess says. “But the caveat, I would say, is that most of the universe is in a dark form that we don't understand.”

The rates predicted from measurements made on the early universe with the Planck satellite are 9 percent smaller than the rates measured by Riess’ team—a puzzling mismatch that suggests the universe could be expanding faster than physicists think it should.

David Kaplan, a theorist at Johns Hopkins University who was not involved with the study, is intrigued by the discrepancy because it could be easily explained with the addition of a new theory, or even a slight tweak to a current theory.

“Sometimes there's a weird discrepancy or signal and you think 'holy cow, how am I ever going to explain that?'” Kaplan says. “You try to come up with some cockamamie theory. This, on the other hand, is something that lives in a regime where it's really easy to explain it with new degrees of freedom.”

Kaplan’s favorite explanation is that there’s an undiscovered particle, which would affect the expansion rate in the early universe. “If there are super light particles that haven't been taken into account yet and they make up some smallish fraction of the universe, it seems that can explain the discrepancy relatively comfortably,” he says.

But others disagree. “We understand so little about dark energy that it's tempting to point to something there,” says David Spergel, an astronomer from Princeton University who was also not involved in the study. One explanation is that dark energy, the cause of the universe’s accelerating expansion, is growing stronger with time.

“The idea is that if dark energy is constant, clusters of galaxies are moving apart from each other but the clusters of galaxies themselves will remain forever bound,” says Alex Filippenko, an astronomer at the University of California, Berkeley and a co-author on Riess’ paper. But if dark energy is growing in strength over time, then one day—far in the future—even clusters of galaxies will get ripped apart. And the trend doesn’t stop there, he says. Galaxies, clusters of stars, stars, planetary systems, planets, and then even atoms will be torn to shreds one by one.

The implications could—literally—be Earth-shattering. But it’s also possible that one of the two measurements is wrong, so both teams are currently working toward even more precise measurements. The latest discrepancy is also relatively minor compared to past disagreements.

“I'm old enough to remember when I was first a student and went to conferences and people argued over whether the Hubble constant was 50 or 100,” says Spergel. “We're now in a situation where the low camp is arguing for 67 and the high camp is arguing for 73. So we've made progress! And that's not to belittle this discrepancy. I think it's really interesting. It could be the signature of new physics.”

Imagine a mansion.

Now picture that mansion at the heart of a neighborhood that stretches irregularly around it, featuring other houses of different sizes—but all considerably smaller. Cloak the neighborhood in darkness, and the houses appear as clusters of lights. Many of the clusters are bright and easy to see from the mansion, but some can just barely be distinguished from the darkness. 

This is our galactic neighborhood. The mansion is the Milky Way, our 100,000-light-years-across home in the universe. Stretching roughly a million light years from the center of the Milky Way, our galactic neighborhood is composed of galaxies, star clusters and large roving gas clouds that are gravitationally bound to us.

The largest satellite galaxy, the Large Magellanic Cloud, is also one of the closest. It is visible to the naked eye from areas clear of light pollution in the Southern Hemisphere. If the Large Magellanic Cloud were around the size of the average American home—about 2,500 square feet—then by a conservative estimate the Milky Way mansion would occupy more than a full city block. On that scale, our most diminutive neighbors would occupy the same amount of space as a toaster.

Our cosmic neighbors promise answers to questions about hidden matter and the ancient universe. Scientists are setting out to find them.

What makes a neighbor

If we are the mansion, the neighboring houses are dwarf galaxies. Scientists have identified about 50 possible galaxies orbiting the Milky Way and have confirmed the identities of roughly 30 of them. These galaxies range in size from several billion stars to only a few hundred. For perspective, the Milky Way contains somewhere between 100 billion to a trillion stars. 

Dwarf galaxies are the most dark-matter-dense objects known in the universe. In fact, they have far more dark matter than regular matter. Segue 1, our smallest confirmed neighbor, is made of 99.97 percent dark matter.

Dark matter is key to galaxy formation. A galaxy forms when enough regular matter is attracted to a single area by the gravitational pull of a clump of dark matter.

Projects such as the Dark Energy Survey, or DES, find these galaxies by snapping images of a segment of the sky with a powerful telescope camera. Scientists analyze the resulting images, looking for the pattern of color and brightness characteristic of galaxies. 

Scientists can find dark matter clumps by measuring the motion and chemical composition of stars. If a smaller galaxy seems to be behaving like a more massive galaxy, observers can conclude a considerable amount of dark matter must anchor the galaxy.

“Essentially, they are nearby clouds of dark matter with just enough stars to detect them,” says Keith Bechtol, a postdoctoral researcher at the University of Wisconsin-Madison and a member of the Dark Energy Survey.

Through these methods of identification (and thanks to the new capabilities of digital cameras), the Sloan Digital Sky Survey kicked off the modern hunt for dwarf galaxies in the early 2000s. The survey, which looked at the northern part of the sky, more than doubled the number of known satellite dwarf galaxies from 11 to 26 galaxies between 2005 and 2010. Now DES, along with some other surveys, is leading the search. In the last few years DES and its Dark Energy Camera, which maps the southern part of the sky, brought the total to 50 probable galaxies. 

Dark matter mysteries

Dwarf galaxies serve as ideal tools for studying dark matter. While scientists haven’t yet directly discovered dark matter, in studying dwarf galaxies they’ve been able to draw more and more conclusions about how it behaves and, therefore, what it could be. 

“Dwarf galaxies tell us about the small-scale structure of how dark matter clumps,” says Alex Drlica-Wagner of Fermi National Accelerator Laboratory, one of the leaders of the DES analysis. “They are excellent probes for cosmology at the smallest scales.”

Dwarf galaxies also present useful targets for gamma-ray telescopes, which could tell us more about how dark matter particles behave. Some models posit that dark matter is its own antiparticle. If that were so, it could annihilate when it meets other dark matter particles, releasing gamma rays. Scientists are looking for those gamma rays. 

But while studying these neighbors provides clues about the nature of dark matter, they also raise more and more questions. The prevailing cosmological theory of dark matter has accurately described much of what scientists observe in the universe. But when scientists looked to our neighbors, some of the predictions didn’t hold up.

The number of galaxies appears to be lower than expected from calculations, for example, and those that are around seem to be too small. While some of the solutions to these problems may lie in the capabilities of the telescopes or the simulations themselves, we may also need to reconsider the way we think dark matter interacts. 

The elements of the neighborhood

Dwarf galaxies don’t just tell us about dark matter: They also present a window into the ancient past. Most dwarf galaxies’ stars formed more than 10 billion years ago, not long after the Big Bang. Our current understanding of galaxy formation, according to Bechtol, is that after small galaxies formed, some of them merged over billions of years into larger galaxies. 

If we didn’t have these ancient neighbors, we’d have to peer all the way across the universe to see far enough back in time to glimpse galaxies that formed soon after the big bang. While the Milky Way and other large galaxies bustle with activity and new star formation, the satellite galaxies remain mostly static—snapshots of galaxies soon after their birth. 

“They’ve mostly been sitting there, waiting for us to study them,” says Josh Simon, an astronomer at the Carnegie Institution for Science.

The abundance of certain elements in stars in dwarf galaxies can tell scientists about the conditions and mechanisms that produce them. Scientists can also look to the elements to learn about even older stars. 

The first generation of stars are thought to have looked very different than those formed afterward. When they exploded as supernovae, they released new elements that would later appear in stars of the next generation, some of which are found in our neighboring galaxies.

“They do give us the most direct fingerprint we can get as to what those first stars might have been like,” Simon says.

Scientists have learned a lot about our satellites in just the past few years, but there’s always more to learn. DES will begin its fourth year of data collection in August. Several other surveys are also underway. And the Large Synoptic Survey Telescope, an ambitious international project currently under construction in Chile, will begin operating fully in 2022. LSST will create a more detailed map than any of the previous surveys’ combined. 

Use this interactive graphic to explore our neighboring galaxies. Click on the abbreviated name of the galaxy to find out more about it. 

The size of each galaxy is listed in parsecs, a unit equal to about 3.26 light-years or 19 trillion miles. The distance from the Milky Way is described in kiloparsecs, or 1000 parsecs. The luminosity of each galaxy, L⊙, is explained in terms of how much energy it emits compared to our sun. Right ascension and declination are astronomical coordinates that specify the galaxy's location as viewed from Earth. 

Read extra descriptive text about some of our most notable neighboring galaxies (the abbreviations for which appear in darker red).

As a general rule, theorist Nima Arkani-Hamed does not get involved in physics bets.

“Theoretical physicists like to take bets on all kinds of things,” he says. “I’ve always taken the moral high ground… Nature decides. We’re all in pursuit of the truth. We’re all on the same side.”

But sometimes you’re in Copenhagen for a conference, and you’re sitting in a delightfully unusual restaurant—one that sort of reminds you of a cave—and a fellow physicist gives you the opportunity to get in on a decade-old wager about supersymmetry and the Large Hadron Collider. Sometimes then, you decide to bend your rule. “It was just such a jovial atmosphere, I figured, why not?”

That’s how Arkani-Hamed found himself back in Copenhagen this week, passing a 1000-Krone bottle of cognac to one of the winners of the bet, Director of the Niels Bohr International Academy Poul Damgaard.

Arkani-Hamed had wagered that experiments at the LHC would find evidence of supersymmetry by the arbitrary date of June 16, 2016. Supersymmetry, SUSY for short, is a theory that predicts the existence of partner particles for the members of the Standard Model of particle physics

The deadline was not met. But in a talk at the Niels Bohr Institute, Arkani-Hamed pointed out that the end of the gamble does not equal the end of the theory.

“I was not a good student in school,” Arkani-Hamed explained. “One of my big problems was not getting homework done on time. It was a constant battle with my teachers… Just give me another week! It’s kind of like the bet.”

He pointed out that so far the LHC has gathered just 1 percent of the total amount of data it aims to collect.

With that data, scientists can indeed rule out the most vanilla form of supersymmetry. But that’s not the version of supersymmetry Arkani-Hamed would expect the LHC to find anyway, he said.

It is still possible LHC experiments will find evidence of other SUSY models—including the one Arkani-Hamed prefers, called split SUSY, which adds superpartners to just half of the Standard Model’s particles. And if LHC scientists don’t find evidence of SUSY, Arkani-Hamed pointed out, the theoretical problems it aimed to solve will remain an exciting challenge for the next generation of theorists to figure out.

“I think Winston Churchill said that in victory you should be magnanimous,” Damgaard said after Arkani-Hamed’s talk. “I know also he said that in defeat you should be defiant. And that’s certainly Nima.”

Arkani-Hamed shrugged. But it turned out he was not the only optimist in the room. Panelist Yonit Hochberg of the University of California, Berkeley conducted an informal poll of attendees. She found that the majority still think that in the next 20 years, as data continues to accumulate, experiments at the LHC will discover something new.

Astronomers Edwin Hubble and Milton Humason in the early 20th century discovered that galaxies are moving away from the Milky Way. More to the point: Every galaxy is moving away from every other galaxy on average, which means the whole universe is expanding. In the past, then, the whole cosmos must have been much smaller, hotter and denser. 

That description, known as the Big Bang model, has stood up against new discoveries and competing theories for the better part of a century. So what is this “Big Bang” thing all about?

The Big Bang happened everywhere at once. 

The universe has no center or edge, and every part of the cosmos is expanding. That means if we run the clock backward, we can figure out exactly when everything was packed together—13.8 billion years ago. Because every place we can map in the universe today occupied the same place 13.8 billion years ago, there wasn't a location for the Big Bang: Instead, it happened everywhere simultaneously.

The Big Bang may not describe the actual beginning of everything. 

“Big Bang” broadly refers to the theory of cosmic expansion and the hot early universe. However, sometimes even scientists will use the term to describe a moment in time—when everything was packed into a single point. The problem is that we don’t have either observations or theory that describes that moment, which is properly (if clumsily) called the “initial singularity.” 

The initial singularity is the starting point for the universe we observe, but there might have been something that came before. 

The difficulty is that the very hot early cosmos and the rapid expansion called “inflation” that likely happened right after the singularity wiped out most—if not all—of the information about any history that preceded the Big Bang. Physicists keep thinking of new ways to check for signs of an earlier universe, and though we haven’t seen any of them so far, we can’t rule it out yet.

The Big Bang theory explains where all the hydrogen and helium in the universe came from. 

In the 1940s, Ralph Alpher and George Gamow calculated that the early universe was hot and dense enough to make virtually all the helium, lithium and deuterium (hydrogen with a neutron attached) present in the cosmos today; later research showed where the primordial hydrogen came from. This is known as “Big Bang nucleosynthesis,” and it stands as one of the most successful predictions of the theory. The heavier elements (such as oxygen, iron and uranium) were formed in stars and supernova explosions.

The best evidence for the Big Bang is in the form of microwaves. Early on, the whole universe was dense enough to be completely opaque. But at a time roughly 380,000 years after the Big Bang, expansion spread everything out enough to make the universe transparent. 

The light released from this transition, known as the cosmic microwave background (CMB), still exists. It was first observed in the 1960s by Arno Penzias and Robert Wilson. That discovery cemented the Big Bang theory as the best description of the universe; since then, observatories such WMAP and Planck have used the CMB to tell us a lot about the total structure and content of the cosmos.

One of the first people to think scientifically about the origin of the universe was a Catholic priest. 

In addition to his religious training and work, Georges Lemaître was a physicist who studied the general theory of relativity and worked out some of the conditions of the early cosmos in the 1920s and ’30s. His preferred metaphors for the origin of the universe were “cosmic egg” and “primeval atom,” but they never caught on, which is too bad, because …

It seems nobody likes the name "Big Bang." 

Until the 1960s, the idea of a universe with a beginning was controversial among physicists. The name “Big Bang” was actually coined by astronomer Fred Hoyle, who was the leading proponent of an alternative theory, where universe continues forever without a beginning.

His shorthand for the theory caught on, and now we’re kind of stuck with it. Calvin and Hobbes’ attempt to get us to adopt “horrendous space kablooie” has failed so far.

The Big Bang is the cornerstone of cosmology, but it’s not the whole story. Scientists keep refining the theory of the universe, motivated by our observation of all the weird stuff out there. Dark matter (which holds galaxies together) and dark energy (which makes the expansion of the universe accelerate) are the biggest mysteries that aren't described by the Big Bang theory by itself. 

Our view of the universe, like the cosmos itself, keeps evolving as we discover more and more new things. But rather than fading away, our best explanation for why things are the way they are has remained—the fire at the beginning of the universe.

When Spencer Axani was an undergraduate physics student, his background in engineering led him to a creative pipe dream: a pocket-sized device that could count short-lived particles called muons all day.

Muons, heavier versions of electrons, are around us all the time, a byproduct of the cosmic rays that shoot out from supernovae and other high-energy events in space. When particles from those rays hit Earth’s atmosphere, they often decay into muons.

Muons are abundant on the surface of the Earth, but in Axani’s University of Alberta underground office, shielded by the floors above, they might be few and far between. A pocket detector would be the perfect gadget for measuring the difference.

Now a doctoral student at Massachusetts Institute of Technology, Axani has nearly made this device a reality. Along with an undergraduate student and Axani’s adviser, Janet Conrad, he’s developed a detector that sits on a desk and tallies the muons that pass by. The best part? The whole system can be built by students for under $100.

“Compared to most detectors, it’s by far the cheapest and smallest I’ve found,” Axani says. “If you make 100,000 of these, it starts becoming a very large detector. Instrumenting airplanes and ships would let you start measuring cosmic ray rates around the world.”

Particle physicists deal with cosmic rays all of the time, says Conrad, a physics professor at MIT. “Sometimes we love them, and sometimes we hate them. We love them if we can use them for calibration of our detectors, and we hate them if they provide a background for what it is that we are trying to do.”

Conrad used small muon detectors similar to the one Axani dreamed about when leading a neutrino experiment at Fermi National Accelerator Laboratory called MiniBooNE. When a professor at the University of Alberta proposed adding mini-muon detectors to another neutrino experiment, Axani was ready to pitch in.

The idea was to create muon detectors to add to IceCube, a neutrino detector built into the ice in Antarctica. They would be inserted into IceCube’s proposed low-energy upgrade, known as PINGU (Precision IceCube Next Generation Upgrade).

First, they needed a prototype. Axani got to work and quickly devised a rough detector housed in PVC pipe. “It looked pretty lab,” Axani said. It also gave off a terrible smell, the result of using a liquid called toluene as a scintillator, a material that gives off light when hit by a charged particle.

Over the next few months, Axani refined the device, switching to an odorless plastic scintillator and employing silicon photomultipliers (SiPM), which amplify the light from the scintillator into a signal that can be read. Adding some electronics allowed him to build a readout screen that ticks off the amount of energy from muon interactions and registers the time of the event.

Sitting in Axani’s office, the counter shows a rate of one muon every few seconds, which is what they expected from the size of the detector. Though it’s fairly constant, even minor changes like increased humidity or heavy rain can alter it.

Conrad and Axani have taken the detector down into the Boston subway, using the changes in the muon count to calculate the depth of the train tunnels. They’ve also brought it into the caverns of Fermilab’s neutrino experiments to measure the muon flux more than 300 feet underground.

Axani wants to take it to higher elevations—say, in an airplane at 30,000 feet above sea level—where muon counts should be higher, since the particles have had less time to decay after their creation in the atmosphere.

Fermilab physicist Herman White suggested taking one of the the tiny detectors on a ship to study muon counts at sea. Mapping out the muon rate around the globe at sea has never been achieved. Liquid scintillator can be harmful to marine life, and the high voltage and power consumption of the large devices present a safety hazard.

While awaiting review of the PINGU upgrade, both Conrad and Axani see value in their project as an educational tool. With a low cost and simple instructions, the muon counter they created can be assembled by undergraduates and high school students, who would learn about machining, circuits, and particle physics along the way—no previous experience required.

“The idea was, students building the detectors would develop skills typically taught in undergraduate lab classes,” Spencer says. “In return, they would end up with a device useful for all sorts of physics measurements.”

Conrad has first-hand knowledge of how hands-on experience like this can teach students new skills. As an undergraduate at Swarthmore College, she took a course that taught all the basic abilities needed for a career in experimental physics: using a machine shop, soldering, building circuits. As a final project, she constructed a statue that she’s held on to ever since.

Creating the statue helped Conrad cement the lessons she learned in the class, but the product was abstract, not a functioning tool that could be used to do real science.

“We built a bunch of things that were fun, but they weren’t actually useful in any way,” Conrad says. “This [muon detector] takes you through all of the exercises that we did and more, and then produces something at the end that you would then do physics with.”

Axani and Conrad published instructions for building the detector on the open-source physics publishing site arXiv, and have been reworking the project with the aim of making it accessible to high-school students. No math more advanced than division and multiplication is needed, Axani says. And the parts don’t need to be new, meaning students could potentially take advantage of leftovers from experiments at places like Fermilab.

“This should be for students to build,” Axani says. “It’s a good project for creative people who want to make their own measurements.”

Science can produce astounding images. Arcs of electricity. Microbial diseases, blown up in full color. The bones of a long-dead beasts. The earth, a hazy blue marble in the distance. 

But scientific progress is not always so visually dramatic. In laboratories in certain fields, such as high-energy particle physics, the stuff that excites the scientists might be hidden within the innards of machinery or encrypted as data.

Those labs need visual translators to show to the outside world the beauty and significance of their experiments. 

Reidar Hahn specializes in bringing physics to life. As Fermilab’s house photographer, he has been responsible for documenting most of what goes on in and around the lab for the past almost 30 years. His photos reveal the inner workings of complicated machinery. They show the grand scale of astronomical studies. 

Hahn took up amateur photography in his youth, gaining experience during trips to the mountains out West. He attended Michigan Technological University to earn a degree in forestry and in technical communications. The editor of the school newspaper noticed Hahn’s work and recruited him; he eventually became the principal photographer. 

After graduating, Hahn landed a job with a group of newspapers in the suburbs of Chicago. He became interested in Fermilab after covering the opening of the Tevatron, Fermilab’s now-decommissioned landmark accelerator. He began popping in to the lab to look for things to photograph. Eventually, they asked him to stay.

Reidar says he was surprised by what he found at the lab. “I had this misconception that when I came here, there would be all these cool, pristine cleanrooms with guys in white suits and rubber gloves. And there are those things here. But a lot of it is concrete buildings with duct tape and cable ties on the floor. Sometimes, the best thing you can do for a photo is sweep the floor before you shoot.”

Hahn says he has a responsibility, when taking photos for the public, to show the drama of high-energy physics, to impart a sense of excitement for the state of modern science.

Below, he shares the techniques he used to make some of his iconic images for Fermilab.

The Tevatron

“I knew they were going to be shutting down the Tevatron—our large accelerator—and I wanted to get a striking or different view of it. It was 2011, and it would be big news when the lab shut it down. 

“This was composed of seven different photos. You can’t keep the shutter open on a digital camera very long, so I would do a two-minute exposure, then do another two-minute exposure, then another. This shot was done in the dead of winter on a very cold day; It was around zero [degrees]. I was up on the roof probably a good hour.

“It took a little time to prepare and think out. I could have shot it in the daylight, but it wouldn’t have had as much drama. So I had fire trucks and security vehicles and my wife driving around in circles with all their lights on for about half an hour. The more lights the better. I was on the 16th floor roof of the high-rise [Fermilab’s Wilson Hall]. I had some travelling in other directions, because if they were all going counter-clockwise, you’d just see headlights on the left and taillights on the other end. They were slowly driving around—10, 15 miles an hour—and painting a circle [of light] with their headlights and taillights. 

“This image shows a sense of physics on a big scale. And it got a lot of play. It got a full double spread in Scientific American. It was in a lot of other publications.

“I think particle physics has some unique opportunities for photography because of these scale differences. We’re looking for the smallest constituents of matter using the biggest machines in the world to do it.”

SRF cavities

“This was an early prototype superconducting [radio-frequency] cavity, which is used to accelerate particles. Every one of those donuts there forces a particle to go faster and faster. In 2005, these cavities were just becoming a point of interest here at Fermilab. 

“This was sitting in a well-lit room with a lot of junk around it. They didn’t want it moved. So I had to think how I could make this interesting. How could I give it some motion, some feel that there’s some energy here?

“So I [turned] all the room lights out. This whole photo was done with a flashlight. You leave the shutter open, and you move the light over the subject and paint the light onto the subject. It’s a way to selectively light certain things. This is about four exposures combined in Photoshop. I had a flashlight with different color gels on it, and I just walked back and forth. 

“I wanted something dynamic to the photo. It’s an accelerator cavity; it should look like something that provides movement. So in the end, I took the gels off, and I dragged the flashlight through the scene [to create the streak of light above the cavity]. It could represent a [particle] beam, but it just provides some drama. 

“A good photo can help communicate that excitement we all have here about science. Scientists may not use [this photo] as often for technical things, but we’re also trying to make science exciting for the non-scientists. And people can learn that some of these things are beautiful objects. They can see some kind of elegance to the equipment that scientists develop and build for the tools of discovery.”

Scintillating material

“This was taken back in ’93. It was done on film—we bought our first digital camera in 1998. 

“This is a chemist here at the lab, and she's worked a lot on different kinds of scintillating compounds. A scintillator is something that takes light in the invisible spectrum and turns it to the visible spectrum. A lot of physics detectors use scintillating material to image particles that you can't normally see.

“[These] are some test samples she had. She needed the photo to illustrate various types of wave-shifting scintillator. I wanted to add her to the photo because—it all goes back to my newspaper days—people make news, not things. But the challenge gets tougher when you have to add a person to the picture. You can’t have someone sit still for three minutes while making an exposure.

“There’s a chemical in this plastic that wave-shifts some type of particle from UV to visible light. So I painted the scintillating plastic with the UV light in the dark and then had Anna come over and sit down at the stool. I had two flashes set up to light her. [The samples] all light internally. That’s the beauty of scintillator materials. 

“But it goes to show you how we have to solve a lot of problems to actually make our experiments work.”

Cerro Tololo Observatory

“This is the Cerro Tololo [Inter-American] Observatory in Chile, taken in October 2012. We have a lot of involvement in the Dark Energy Survey, [a collaboration to map galaxies and supernovae and to study dark energy and the expansion of the universe]. Sometimes we get to go to places to document things the lab’s involved in.

“This one is hundreds of photos stacked together. If you look close, you can see it’s a series of dots. A 30-second exposure followed by a second for the shutter to reset and then another 30-second exposure.  

“The Earth spins. When you point a camera around the night sky and happen to get the North Star or Southern Cross—this is the Southern Cross—in the shot, you can see how the Earth rotates: This is what people refer to as star-trails. It’s a good reminder that we live in a vast universe and we’re spinning through it.

“We picked a time when there’s no moon because it’s hard to do this kind of shot when the moon comes up. Up on the top of the mountain, they don’t want a lot of light. We walked around with little squeeze lights or no lights at all because we didn’t want to have anything affect the telescopes. But every once in awhile I would notice a car go down from the top, and as it would go around the corner, they’d tap the brake lights. We learned to use the brake lights to light the building. It gives some drama to the dome.

“You’ve got to improvise. You have to work with some very tight parameters and still come back with the shot.”