Teaching Astronomy

Commentary: How Killer Black Holes Saved Astronomy[1]

As a physics professor at a small college, I teach a variety of courses to a student body that is diverse in both preparedness and interests. My courses range from general-education physics and astronomy to upper-level courses on advanced physics topics. In each setting, I have found that integrating popular and historical readings into the curriculum has a substantive and positive effect on the student learning experience.

When I started my career, I quickly realized that curriculum design should be much more thoughtful and nuanced than simply choosing a textbook. Despite the time and effort publishers spend to produce accessible and engaging astronomy textbooks, I found that my students struggled with the voluminous texts and their formal tone.

Evidence of that struggle emerged when I assigned open-book quizzes that consisted of basic questions addressed in the text—from simple definitions to foundational concepts in physics and astronomy. The majority of my students have performed poorly on those quizzes, with class averages typically in the C range, even though all the answers came directly from the textbook. Whether students weren’t reading or they were reading without any substantive comprehension, the reality was that they arrived in class without the necessary background to review examples, collaborate in groups, or contribute to class discussions. If I didn’t find a way to engage and motivate my students, the astronomy course was destined to become an experience that neither instructor nor students enjoyed.

While researching different textbook options, I came to realize that the majority of introductory astronomy textbooks have similar writing, content, and design elements. Therefore, adopting a new textbook would not solve the problems my students were having. My experience in teaching the general astronomy course was what first motivated me to explore and develop my curriculum.

After several years of exploration, I have arrived at an approach that allows for the technical treatment of physics and astronomy topics within their historical, cultural, and social contexts. I complement the technical content of a textbook with reading and writing assignments derived from popular and historical science publications. I have found that approach to be successful at engaging students regardless of grade level, major, or interests.

I had read Neil deGrasse Tyson’s Death by Black Hole1 and had noted its breadth of topics. A compilation of short essays written for Natural History magazine, it spans subjects from science and numerical literacy to the history and fundamental physics of various astronomy phenomena. I decided to use it in my general-education astronomy course to complement the technical assignments of a standard textbook. I emphasized reading and writing assignments. The idea wasn’t to replace the textbook but to drive student interest and motivate learning. The textbook, then, would be a resource that expands on topics covered in the readings.

My astronomy course meets for three 50-minute lectures and one 3-hour lab each week. Students typically read two chapters—roughly 20 pages—from Death by Black Hole each week and write a 1- or 2-page response. I set aside 20 minutes of weekly class time to discuss the reading and the students’ responses. It is important that they not simply summarize a reading; a thoughtful response allows the student to consider what the reading means and to connect it to personal experiences and anecdotes. In the lab, we expand on problem solving and the quantitative aspects of the course. Without such an arrangement, adopting the reading-and-writing approach may require a reduction in course topics or content.

In Tyson’s broad-ranging book I have found appropriate reading assignments to complement every textbook chapter covered throughout the semester. For example, in the chapter that gives the book its title, Tyson describes what would happen as you fall into a black hole (he uses the term “spaghettification”). Students read this chapter as the course begins to explore extreme environments in the universe, including black holes, quasars, and gamma-ray bursts.

I implemented this approach in my astronomy course in 2013, and since 2015 I have included a question on the midterm exam that asks students to discuss the value of reading Death by Black Hole and whether they would recommend the book to a friend interested in learning about astronomy. The feedback has been overwhelmingly positive, and the learning environment and level of student engagement are the healthiest I have ever experienced.

I have used the same approach with much success in my advanced courses. Mark Kidger’s Cosmological Enigmas2 and Death by Black Hole have made wonderful companion texts in a mid-level astrophysics course. The approach works well for exploring the people behind paradigm shifts throughout the history of physics. In that context, I use Faraday, Maxwell, and the Electromagnetic Field by Nancy Forbes and Basil Mahon3 in my upper-level electricity and magnetism course, and I use Thirty Years That Shook Physics by George Gamow4 and Quantum by Manjit Kumar5 in my modern physics course to enhance a learning experience that is often focused on technical and abstract content.

I highly recommend the above titles for your courses, but I am nearly convinced that the specific readings used are irrelevant. I am constantly searching for new books and texts to incorporate into my reading lists and am working to expand the courses for which I use this curriculum design. What makes this approach so compelling for students is the opportunity to explore the historical, cultural, and social contexts of the subjects found in textbooks. If your readings address those topics, I am confident they will have the same effect on your courses.

Perhaps it is hyperbole to say killer black holes saved my astronomy course, but the reality is difficult to ignore. By using popular and historical readings to complement technical content, I have seen dramatic improvement in student participation and learning in all my courses. I highly recommend using popular and historical science writings in the ways I’ve outlined here.


  1. 1. N. D. Tyson, Death by Black Hole: And Other Cosmic Quandaries, W. W. Norton (2007).
  2. 2. M. Kidger, Cosmological Enigmas: Pulsars, Quasars & Other Deep-Space Questions, Johns Hopkins U. Press (2007).
  3. 3. N. Forbes, B. Mahon, Faraday, Maxwell, and the Electromagnetic Field: How Two Men Revolutionized Physics, Prometheus Books (2014).
  4. 4. G. Gamow, Thirty Years That Shook Physics: The Story of Quantum Theory, Doubleday (1966).
  5. 5. M. Kumar, Quantum: Einstein, Bohr, and the Great Debate about the Nature of Reality, W. W. Norton (2008).
  6. © 2017 American Institute of Physics.

[1] By Joseph Ribaudo, “How Killer Black Holes Saved Astronomy,” Physics Today (70, 7, July 2017, pp. 10-11). Joseph Ribaudo is at Utica College, Utica, New York (jsribaud@utica.edu). doi: http://dx.doi.org/10.1063/PT.3.3609


Juno Delivers Stunning New Views of Great Red Spot

Juno Delivers Stunning New Views of Great Red Spot[1]

Scientists and the public are dazzled by images from the spacecraft’s close encounter with Jupiter’s largest—and the Solar System’s most famous—storm

An artistic rendition of the NASA Juno spacecraft flying over Jupiter’s Great Red Spot. Credit: NASA/JPL/Björn Jónsson/Seán Doran


Humanity has just gained its best-ever views of Jupiter’s Great Red Spot, a storm large enough to swallow Earth whole that has raged for centuries in the gas-giant planet’s atmosphere.

Snapped earlier this week [week of June 9, 2017] by NASA’s basketball court–size solar-powered Juno spacecraft, the new images from just 9,000 kilometers above Jupiter reveal never-before-seen details of the Great Red Spot and its turbulent surroundings that raise just as many questions as they answer. Scientists know the feature is generally anticyclonic—spinning counterclockwise. They also know it is much higher and colder than most of Jupiter’s upper atmosphere; it might better be called the Great Cold Spot because it rises far above the surrounding clouds, expanding and cooling as it goes. Like most of Jupiter’s cloud deck, it is rich in ammonia. What they still do not know is how the storm has endured for so long, or how deep it swirls into Jupiter. In recent decades it has slowly become more circular than oval, for reasons unknown, leading some researchers to suspect it is on the verge of dissipating. No one fully understands the origins of its reddish color, either.

Although studied for centuries through small ground-based telescopes, the Spot only received its first close-ups in the latter half of the 20th century through a progressive series of close encounters with NASA’s Pioneer, Voyager and Galileo spacecraft—as well as through detailed remote monitoring by the Hubble Space Telescope and other observatories. With each additional observation, researchers have gradually gained a deeper understanding of the storm’s—and Jupiter’s—dynamic nature, and the latest are no exception.

“This week’s images of the Great Red Spot are the best yet, surpassing those from Voyager,” says John Rogers, a veteran observer of the giant planet and director of the Jupiter section of the British Astronomical Association. “Although the improvement in resolution and quality is incremental, not a big leap, it has crossed a threshold to reveal small-scale waves and tiny shadow-casting clouds in the Great Red Spot which were never seen before.”

The new observations are “going to enable great comparisons with what we saw from the Galileo spacecraft 20 years ago—and Voyager 20 years before that,” says Amy Simon, an expert in planetary atmospheres at NASA Goddard Space Flight Center. “We can certainly say it has evolved a lot in 20 years—it’s much rounder, of course, but the changes to the shear in the internal cloud structures catch my eye; more swirls and turbulence in areas that used to be completely stretched apart into long streaks. We’ll have to analyze that to fully understand how the Great Red Spot is changing over time.”

Already, some researchers are speculating about subtle shadows and color gradations in the Spot, which the new images suggest are most intense near its towering center. That would help validate a recent theory for its coloration, which posits that the red color is a sunburn of sorts. Arising from ultraviolet light bombarding ammonia and trace hydrocarbons lofting high into Jupiter’s stratosphere, the Spot’s hues would thus be most intense where it reaches highest above the surrounding clouds.

According to Michael Wong, a planetary scientist at the University of California in Berkeley, the overarching takeaway from these new images is how relatively blinkered most of our earlier views have been. Wong used the Hubble Space Telescope to monitor Jupiter concurrently with Juno’s close encounter with the Great Red Spot. “When you go to Juno’s images, the areas with the finest structure are the areas that seemed plain in the Hubble image,” Wong says. “Like a fractal, we see detail at the limit of the resolution no matter what scale we observe.”

In a broad sense, whereas these new vistas come courtesy of Juno, which launched in 2011 and swooped into polar orbit around Jupiter just over a year ago, their true source is the spacecraft’s most modest instrument—a camera called JunoCam considered so scientifically unremarkable that it was given a barebones operational budget and officially included only for “public outreach.”

Those limited resources mean that JunoCam’s scientists rely on a small army of volunteer “citizen scientists” using backyard telescopes to flag transient features in the Jovian atmosphere as “points of interest” for the instrument to observe. Each feature is given a fanciful name, such as Mortyland, Hotspot Tail and Carl Sagan’s Jawbreaker. Because of Juno’s swooping polar orbit that takes it breathtakingly close to the planet, most of JunoCam’s images of these features are distorted into an hourglass shape due to foreshortened horizons; the colors are pale, the outlines of clouds hazy. A second group of amateurs then extracts awe-inspiring details from these raw images after Juno beams them home. Steadily streaming onto JunoCam’s Web site, their best-processed images correct for distortion, enhance colors and sharpen contrast in a way that leaves professionals spellbound.

In the aftermath of a raw-image dump, “about every five minutes I refresh my screen, and each time I find there are more of these beautiful, hugely valuable products,” says Candice Hansen, lead scientist for NASA’s JunoCam team. “We have a tiny, little team because this is an outreach instrument, so the public is really our team—we are relying heavily on our amateur cadre.” To demonstrate, she pulls up a zoomed-in image of the Spot incrementally processed by two of JunoCam’s star volunteers—a first pass by Gerald Eichstädt, a mathematician in Stuttgart, Germany, and a second pass by Seán Doran, a visual artist in London.

“These guys in particular—Gerald and Seán—gave us products from Juno’s earlier encounters with Jupiter that showed all these ‘little’ storms just 25, 50 kilometers wide popping up from the cloud tops of the planet’s south tropical zone,” Hansen says. “The storms sort of remind me of squall lines. And here they are, on top of the Great Red Spot! It almost looks frothy…. These are the kinds of details you get when you suddenly have high enough resolution. I can’t tell you what this means for atmospheric dynamics but I’m sure it’s important, and I’m sure that once we get this sorted out it will be a real science result.”

“We really use ‘amateur’ in air quotes for them,” says Glenn Orton, a JunoCam co-investigator at the NASA Jet Propulsion Laboratory. “They really know what they’re doing—and they work for free.”

Eichstädt began working with JunoCam in 2013, when he processed some images of Earth the instrument captured as it looped around our planet to pick up speed en route to Jupiter. Ever since, he has been embroiled in developing a proprietary software “pipeline” for enhancing JunoCam’s images, which requires careful calibration to remove noise from faulty detector pixels as well as modeling variables such as the angle of illumination from the Sun, the absorption of light by the planet and the trajectory of the spacecraft. All together, he says, the routine takes a few hours to produce one processed image—giving him plenty of time and insight to ponder finer details that most others might fail to notice.

Among other things, he has noticed small numbers of individual bright pixels scattered in and around his processed images of the Spot. “Those have been left over by my patching algorithm, and are therefore likely to be no camera artifacts but instead energetic particle hits [from Jupiter’s intense radiation environment] or, with a lot of luck, lightning.” First witnessed in Jupiter’s clouds as rare flashes of scattered light by Voyager 1 in its 1979 flyby and observed decades later by the Galileo orbiter, Jupiter’s lightning is thought to be an indirect tracer of the planet’s water content. Voyager’s and Galileo’s observations suggest each thunderbolt emerges from deep in the atmosphere below Jupiter’s high ammonia clouds, in regions where temperatures and pressures reach the triple point of water and whirling maelstroms of vapor, rain and hail build up immense electric charges. Lightning, however, has never been seen before in the Spot—and Eichstädt is first to say his preliminary comments are only tentative speculations that require much more detailed follow-up.

That will come later, with further close observations by Juno—not only with JunoCam but also its eight other instruments that can measure the planet’s temperature, its magnetic and gravitational fields, microwave emissions from its deep interior, and more. The gravitational and microwave measurements in particular could soon reveal just how far the Spot extends into Jupiter—whether it floats like an iceberg near the top of the atmosphere, or instead bores deep into the planet’s innards.

The spacecraft will in coming years be plunged into Jupiter’s atmosphere, bringing the mission to a fiery end designed to avoid contaminating any of the planet’s astrobiologically interesting icy moons. JunoCam itself may expire much sooner, as early as this fall, due to the intense radiation around the planet, mission planners say. But its legacy will endure—Eichstädt, Doran and other intensive image-processors say their best work is yet to come.

“Two years ago I wasn’t sure if this would work at all,” Hansen says. “I would just tell people, ‘we don’t have a backup imaging team waiting in the wings, so we are just going to put the images out there and see if we get any takers!’ It’s wonderful to see this has actually succeeded, really beyond my wildest dreams.”

[1]Lee Billings on July 13, 2017 in Scientific American

Search for Dark Matter

Physicists Go Deep in Search of Dark Matter[1]

A laboratory buried nearly a mile beneath South Dakota is at the forefront of a global push for subterranean science

A worker gazes into the darkness of the Sanford Underground Research Facility’s “4850 level,” a cavern nearly a mile deep in the Homestake mine that houses state-of-the-art physics experiments. Credit: Sarah Scoles









The elevator that lowers them 4,850 feet down a mine shaft to a subterranean physics lab isn’t called an elevator, the physicists tell me. It’s called The Cage. It descends at precisely 7:30 A.M.—the same time it leaves the surface every day—and doesn’t wait around for stragglers.

I show up on time, and prepare to board with a group of scientists. We look identical: in coveralls blinged out with reflective tape, steel-toed boots, an emergency breathing mask and a lamp that clips to the belt and loops over the shoulder.

An operator opens the big yellow door, directs us inside and then closes The Cage. Soon it begins bumping down at 500 feet per minute. The operator’s headlamp provides the only light, tracing along the timber that lines the shaft. We descend for 10 minutes, silently imagining the weight of the world above us increasing. Water trickling down the shaft’s walls provides an unsettling sound track.

This place—the Sanford Underground Research Facility (SURF) in Lead, S.D.—hosts experiments that can only be conducted deep under Earth’s surface. Entombed beneath the Black Hills by thousands of feet of solid rock, these experiments are shielded from much of the background radiation that bathes the planet’s surface. Here scientists can more easily detect various elusive cosmic messengers that would otherwise be swamped by the sound and fury at the surface—neutrinos that stream from our Sun and from distant exploding stars or other hypothetical particles thought to make up the mysterious dark matter that acts as a hidden hand guiding the growth of galaxies. Such particles are so dim that they’re drowned out aboveground: Looking for them there is a bit like looking for a spotlight shining from the Sun’s surface. But these are the very particles scientists must study to understand how our universe came to be. And so, from the depths of Earth where even the very closest star does not shine, they are glimpsing some of the most ancient, distant and cataclysmic aspects of the cosmos.

This place was not always science-centric: For more than 100 years its labyrinth of deep chambers and drippy, dirt-floored tunnels was a gold mine called Homestake. Today, stripped of much of its precious ore, the facility has become a figurative gold mine for researchers as the U.S.’s premier subterranean lab. This fall SURF will debut a new experiment at the frontiers of physics: CASPAR, which mimics the conditions at the cores of stars where atoms of hydrogen and other light elements fuse to release energy, forming as a by-product the more substantial elements required for building asteroids, planets, mines and mammals. This year physicists are also starting to build equipment for an experiment called LUX–ZEPLIN (LZ), which will try to detect particles of dark matter as soon as 2020.

It is all part of a trend unfolding around (as well as within) the globe, as scientists construct or repurpose buried infrastructure in places like Minnesota, Japan, Italy, China and Finland to peer deep into the cosmos from deep underground, seeking to learn why the universe is the way it is—and maybe how humans got here at all.

Inside The Cage, the riders have leaned their heads back against the walls, eyes closed for a quiet moment before work. They look up as the elevator lurches to a stop and the door opens onto a rounded, rocky hallway, covered in netting to protect against rock slides and cave-ins. The light is yellow, with a spectrum not unlike the Sun’s.

“Just another day in paradise,” one of the passengers says as the operator releases us into this alien environment. We walk away from The Cage, our only conduit to the surface, and toward the strange science that—like extreme subterranean organisms that survive without sunlight—can only happen here.

Cosmic Messengers in a Mine

En route to our first destination, the LZ dark-matter experiment, we walk through a section of the mine called the Davis Lab. Its name descends from late physicist Ray Davis, who visited the town of Lead in the 1960s with a science experiment in mind. Back then Lead and next-door Deadwood looked much like they look now, with one-floor casinos and a bar bearing a sign that reads “Historic Site Saloon No. 10 Where Wild Bill Was Shot.” Davis had asked the owners of the Homestake Mine if he could use a small slice of that vast space to search for solar neutrinos.

Neutrinos are nearly massless particles with no electrical charge. They move almost as fast as light itself. They are barely subject to the effects of gravity and are immune to electromagnetism. In fact, they hardly interact with anything at all—a neutrino might just zip straight through the atoms of any corporeal object in the universe in the way a motorcycle can split lanes straight through traffic. Physicists and astronomers love neutrinos because their cosmic shyness keeps them pristine. Each carries imprints, like birthmarks, from the explosions and radioactive decays that unleashed them on the cosmos. By studying them, scientists can learn about the inner workings of supernovae, the first moments after the big bang, and the seething hearts of stars—including our Sun, which is what Davis wanted to investigate. In the 1960s, theorists had already predicted that neutrinos should exist, but no one had yet found them in the physical world.

The mining company decided to let Davis try to become the first person to do so.

Toiling away on Homestake’s “4850 level”—the “floor” 4,850 feet below the surface—Davis built a neutrino detector that became operational in 1967. Over the course of the next quarter century he extracted what he came for: actual neutrinos, not just theoretical ones on paper. As the first person to directly detect the particles—and so prove they existed at all—Davis won the 2002 Nobel Prize. He was one of the first to show that, sometimes, to best connect with deep space, humans have to travel farther from it, deep inside the planet itself.

During the initial decades of the Davis experiment, the Homestake Mine continued sending a steady stream of gold to the surface, ultimately producing nearly three million pounds of the precious metal during its lifetime—the most of any mine in the Western Hemisphere. But in 2002 when the price of an ounce dropped too low for the mine to turn a profit, Barrick Gold Corp. shut it down and later donated the facility to the State of South Dakota.

The state—with funding from billionaire T. Denny Sanford and the U.S. Department of Energy—expanded on Davis’s legacy and turned the whole operation into a physics lab: today’s SURF, with the original Davis Campus at its core.

Setting Up Shop

As we enter the Davis Campus, we snap elastic-ankle booties over our shoes and are gifted a sticker. “It’s always sunny on the 4850,” it says. The evidence does not support this conclusion.

Our guide, Mark Hanhardt, doesn’t have such a sticker, but he does have a Ghostbusters patch on the upper arm of his coveralls. He later refers to the dark matter that LZ will look for as “ghost particles.” He is, then, the buster to which his patch refers. He’s a jolly guy, with a smile—the eyes-and-mouth kind—always in between his beard and short haircut. An experiment-support scientist, he is also the son of a former Homestake miner called Jim Hanhardt. Jim was laid off when Homestake stopped mining—but he got a different belowground job back when SURF took over, becoming a technical support lead in 2008. For a few years, before his father’s recent death, the two toiled together in this subterranean space—a common story around Lead. Everyone in town seems to know or share blood with someone who works in the lab, because SURF hired back many miners and contracted with local companies for blasting and construction work. Hanhardt’s daily work, then, is carrying on dual legacies—one familial, one scientific. “There’s already been one Nobel from down here,” Hanhardt says, gesturing for us to follow him down the hallway. “Maybe there will be more.”

Hanhardt walks along the platform toward the high-ceilinged room that SURF employees are currently preparing for LUX-ZEPLIN. Most of the space belongs to an immense and empty water tank—three and a half times as tall as me, and across whose diameter four and a half of me could lie down. Hanhardt calls it the “giant science bucket.” Once it had been filled with 72,000 gallons of water and shielded an experiment called LUX, which operated from October 2014 to May 2016. At the time LUX was the world’s most sensitive seeker of dark matter—more attuned to the universe’s most mysterious particles than any other experiment on the planet.

Decades of observations with telescopes have hinted the universe is full of invisible matter that neither emits nor reflects light but outweighs all the visible stars, gas and galaxies combined. This dark matter has apparently shaped some of those galaxies into spirals, and may even be what made their matter glom together into galaxies in the first place. No one knows exactly what the dark matter is made of, but most physicists agree it is likely composed of at least one kind of undiscovered subatomic particle. But just as one cannot say for sure what Sasquatch looks like until you spy one on a remote camera or ensnare one in a trap, scientists can’t say what dark matter is until they capture some.

LUX tried to do just that. During its nearly yearlong run, a 350-kilogram canister of liquid xenon sat nested like a matryoshka doll inside the giant water tank, which isolated the xenon from the intrepid background of run-of-the-mill cosmic rays that manage to penetrate even this far underground. The xenon, denser than solid aluminum, waited hopefully for hypothetical dark matter particles to tunnel through thousands of feet of Earth, ending up in South Dakota after their interstellar—or even intergalactic—journeys. If a particle of dark matter struck an atom of xenon, the collision would produce a flash of light. Electrons would then spin out of the collision, making a second flash. Detectors lining the tank’s interior would pick those up and send a signal back to scientists, who could rewind the reaction to study the particles that first sparked the fireworks.

In October 2016 SURF scientists began dismantling LUX and carting its xenon, like miners, to the surface. The setup had seen nothing. Dark matter had stayed true to its name.

To tenacious physicists, that just meant they needed a bigger, better bucket in which to collect dark matter: LUX-ZEPLIN. When it debuts in 2020, this follow-on experiment will still be the best in the world: 70 times as sensitive as its predecessor, thanks in large part to its 10 metric tons of liquid xenon—as compared with LUX the First’s puny third of a metric ton. The scientific collaboration, which involves 250 scientists from the U.S., the U.K., Portugal, Russia and South Korea, launched construction in February.

Hanhardt sticks his head inside the silvery cylinder of the empty water tank and whispers “Helloooo.” The tiny sound seems to echo almost endlessly, bouncing on the tank walls and throwing itself back at us as evidence of his existence.

Deep Physics

SURF occupies one of the world’s deepest scientific spaces, more than twice as far down as the Soudan Underground Laboratory in Minnesota, which is in a former iron mine. The Super-Kamiokande lab, which focuses on neutrinos like Davis did, occupies the Mozumi zinc mine in Japan, 3,300 feet underground. The deepest physics facility in the world, though, is China’s Jinping Lab, which takes advantage of the tunnels beneath a hydroelectric dam. It has a dark matter detector and a neutrino experiment called PandaX. Using existing infrastructure, as these labs do, means scientists can focus on building their experiments instead of blasting rock. And it means they can rely on local workers who already know how to help maintain the snaking caverns that might otherwise flood, collapse or fill with poisonous gases. Italy is the first country to complete a belowground lab, Gran Sasso, for the express purpose of doing research. It took them 30 years.

Each of these far-flung facilities is racing to be the first to make breakthrough discoveries about elusive dark matter and ghostly neutrinos. But for the end-result science to emerge at its best, the facilities need one another—and one another’s data—to be better, faster and stronger than they can manage on their own. Together, they form an ecosystem that supports science that can’t be done on the surface.

A Pint-Size Star Is Born

SURF, since its genesis, has been expanding beyond the Davis Campus to other parts of the mine—of which there are plenty. The new “campus” is so far away that to visit it we take a railway cart, rumbling down darkened tracks through cavernous spaces like pickax-wielders of old. Cool air still blows past us, somehow flowing into this nether realm fresh from the surface world almost a mile above. Hallway lights pass at intervals, glowing then receding in slow, strobelike procession until we reach what is called the Ross Campus and the CASPAR experiment. CASPAR is a particle accelerator—but one that fits in a regular-size room. A series of tubes, the air sucked from them by vacuum pumps, snakes across tables that run all the way across the room, then bend back into a farther open space. From one end a beam of particles streams through the tubes, its path bent by magnets. At the other end sits a target. When the beam bull’s-eyes it, the collision triggers the fusion processes that happen inside stars, when small atoms join to build larger ones. These processes happen deep inside stellar cores all across the universe, and have created essentially all the elements heavier than helium (elements astronomers call “metals,” even when they are not down in mines).

All those “metals” comprise you, me, these tubes, this cavity, SURF, the ecosystem of underground labs, Earth, and everything you may (or may not) care about. But scientists do not actually understand the details of how stars fuse elements. And because they cannot fly into the center of a star, they have instead traveled toward the center of the planet. Here, shielded from stray radiation and particles that bombard Earth’s surface, they can much more clearly see the particles and radiation from their own experiment, rather than from the Sun or space.

When we arrive, a batch of graduate students and three professors are huddled over several computers, trying to get that beam as just-right as it can be. The mini accelerator itself is on the other side of a door next to them. It looks like a kid’s chemistry set, minus the colorful liquids.

Physicist Michael Wiescher, from the University of Notre Dame, steps away from his colleagues to tell me what they are doing. He speaks quietly, perhaps trying not to disturb them. He needn’t worry, though: Their attention is as focused as the experiment’s beam.

That’s because it’s a big day down here: Wiescher and the others, from Notre Dame and the South Dakota School of Mines, are just starting to launch the beam toward their target. Soon they will make their own pint-size stars, farther from outer space than most people ever go. Their first experiments will examine the details of a process called “helium burning.” In the burning’s first stage, an important interaction happens when three helium nuclei alchemize into one carbon—the atom that by definition makes molecules “organic.” In actual stars this only happens with age: After stars like the Sun have burned through most of the hydrogen fuel at their cores, and have evolved into red giant stars, they begin to fuse helium instead. But here in SURF, in a bathroom-size setup, CASPAR can learn about burning helium any day the scientists see fit, and so learn how to create again and again the elements that became us—fast-forwarding the Sun’s clock while rewinding our own. “It’s not just physics,” says Hanhardt, who stands watch as the team works, “It’s philosophy.” It deals, in other words, in the big questions: How, literally, did we get here? Why, cosmically? These queries have scientific answers but existential implications, the science having moved into territory previously only occupied by religion.

European researchers, Wiescher tells me, are two years behind in their work on a similar project called LUNA–MV at Gran Sasso. China is building its own—JUNA. But CASPAR will (any day now) start cooking first. After the CASPAR team gets a few results on their own, they plan to merge data with some of these other teams, and will let scientists come down to this cave to do their own experiments with the CASPAR equipment. Someday soon—when CASPAR opens up for collaborators, when LZ begins its search—SURF will be robust and bustling in the way of the gold mine’s heyday, back when a single neutrino experiment squatted in a corner.

One of the computer-focused scientists says, “We have 100 percent beam transmission!” and then a smiling grad student—Thomas Kadlecek, from the South Dakota School of Mines—turns to me and Wiescher. He likes it down here, he says. His grandfather was a miner back when it was Homestake. With that, he quickly turns away again goes back to his work, leaning on a rack of electronics.

I later find out his grandfather died in Homestake. Just as one generation of stars fuels the next—South Dakota’s previous underground generations inspire the ones that follow. “They identify with the mine,” Wiescher explains. “It’s incredible.”

[1] Sarah Scoles on July 11, 2017 in Scientific American

Childe Harold’s Pilgrimage Inspiration

Childe Harold’s Pilgrimage Inspiration

Texas State’s “Celestial Sleuth” identifies Lord Byron’s stellar inspiration[1]

What do the moon, Jupiter and the largest volcanic eruption in recorded history have in common? Exactly 200 years ago they all combined to inspire renowned British Romantic poet Lord Byron in writing “Childe Harold’s Pilgrimage,” the work that made the poet famous.

So impressed was Lord Byron that he devoted three stanzas to a spectacular evening twilight that he observed in Italy during August of 1817. “The Moon is up…” he wrote in the fourth canto, published in 1818, “…A Single Star is at her side.” The stanzas hold enough clues to link the scene to the real events that inspired it—including the massive 1815 eruption of Tambora in Indonesia.

Texas State University astronomer, physics professor and Texas State University System Regents’ Professor Donald Olson has applied his distinctive brand of celestial sleuthing to the question of identifying the object next to the moon. Olson determined that Lord Byron’s famed “Star” was actually the planet Jupiter. What’s more, by happy coincidence, the moon and Jupiter are aligning on several dates this summer so that modern viewers can view a twilight scene very much like the one Lord Byron observed exactly 200 years ago.

Olson publishes his findings in the August 2017 issue of Sky & Telescope magazine.

Byron and Hobhouse

Byron’s personal letters and manuscripts provided significant clues. The poet insisted in a note to his first edition of the poem that the fanciful description of the twilight sky was not a creation of his fertile imagination, but an actual event he had observed while riding in Italy with his close friend, John Cam Hobhouse:

“The above description may seem fantastical or exaggerated to those who have never seen an Oriental or an Italian sky – yet it is but a literal – and hardly sufficient delineation of an August evening (the eighteenth) as contemplated in one of many rides along the banks of the Brenta near La Mira.

Byron began writing the fourth canto of “Childe Harold’s Pilgrimage” shortly after moving to the Villa Foscarini on the Brenta Canal in La Mira on June 14, 1817. On July 31, Hobhouse joined him as a houseguest, and the two began daily rides along the canal. Byron’s manuscripts express doubt about the exact date of the memorable twilight, but Hobhouse’s diary is more definitive:

“Wednesday August 20th 1817: Ride with Byron.  Return over the other side of the river from Dolo … Riding home, remarked the moon reigning on the right of us and the Alps still blushing with the gaze of the sunset.  The Brenta came down upon us all purple – a delightful scene, which Byron has put in three stanzas of his “Childe Harold.”

Dian’s Crest

With the date confirmed by Hobhouse, Olson traced Byron’s ride along the Brenta Canal and used astronomical software to recreate the twilight sky as it would have appeared on August 20, 1817. Byron writes:

“While, on the other hand, meek Dian’s crest
Floats through the azure air – and island of the blest!”

Byron’s readers would have understood “Dian’s Crest” as a clear reference to Diana, the Roman goddess of the Moon, who was often depicted with a crescent as a diadem or crest over her forehead. Olson found that’s exactly what Byron would have seen—a waxing gibbous Moon, a day past first quarter, in the evening sky with the brilliant planet Jupiter unusually close by.

Using the same astronomical software, Olson also determined that on several dates during the summer of 2017 this celestial scene will repeat, allowing modern viewers to catch a glimpse, at least in part, of the sky that inspired Byron’s stanzas exactly 200 years ago.

Iris of the West

The stanzas offer one other intriguing clue. Lord Byron writes:

“Heaven is free
From clouds, but of all colours seems to be
Melted to one vast Iris of the West”

In Greek mythology, Iris was the goddess of the rainbow. Byron’s phrasing indicates unusually vivid colors in the cloudless, twilight sky. But what would cause the sky to stand out to capture Byron’s imagination in such a way?

The answer may lie in the 1815 eruption of Tambora, the most powerful volcanic eruption in recorded history. In the February 2004 issue of Sky & Telescope magazine, Olson connected the blood-red sky in Edvard Munch’s most famous painting, The Scream, with the 1883 eruption of Krakatoa. The spectacular “Krakatoa twilight” was the result of dust, gas and aerosols ejected into the upper atmosphere by the volcano, producing remarkable hues in twilight skies worldwide.

The April 1815 eruption of Tambora was far more powerful than Krakatoa. Observers the world over for the next three years noted brilliantly colored sunsets and twilights attributed to the eruption. It is likely that Byron observed a “Tambora Twilight” as the backdrop for his observation of the moon and Jupiter that August evening in 1817.

Childe Harold’s Pilgrimage, Canto IV

Stanza XXVII.
The Moon is up, and yet it is not Night –
Sunset divides the sky with her – a Sea
Of Glory streams along the Alpine height
Of blue Friuli’s mountains; Heaven is free
From clouds, but of all colours seems to be
Melted to one vast Iris of the West,
Where the Day joins the past Eternity;
While, on the other hand, meek Dian’s crest
Floats through the azure air – an island of the blest!

Stanza XXVIII.
A Single Star is at her side, and reigns
With her o’er half the lovely heaven; but still
Yon sunny Sea heaves brightly, and remains
Rolled o’er the peak of the far Rhaetian hill,
As Day and Night contending were, until
Nature reclaimed her order – gently flows
The deep-dyed Brenta, where their hues instil
The odorous Purple of a new-born rose,
Which streams upon her stream, and glassed within it glows,

Stanza XXIX.
Filled with the face of Heaven, which, from afar,
Comes down upon the waters; all its hues,
From the rich sunset to the rising star,
Their magical variety diffuse:
And now they change; a paler Shadow strews
Its mantle o’er the mountains; parting Day
Dies like the Dolphin, whom each pang imbues
With a new colour as it gasps away –
The last still loveliest – till – ‘tis gone – and All is gray.

[1] Jayme Blaschke, “Texas State's 'Celestial Sleuth' identifies Lord Byron's stellar inspiration,” Texas State University (June 26, 2017)

Hints of Extra Dimensions in Gravitational Waves

Hints of Extra Dimensions in Gravitational Waves?[1]

Researchers from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) in Potsdam found that hidden dimensions – as predicted by string theory – could influence gravitational waves. In a recently published paper they study the consequences of extra dimensions on these ripples in space-time, and predict whether their effects could be detected.

Merging black holes generate gravitational waves. These ripples in space-time might be used to unveil hidden dimensions.







LIGO’s first detection of gravitational waves from a black-hole binary in September 2015 has opened a new window onto the universe. Now it looks like with this new observing tool physicists cannot only trace black holes and other exotic astrophysical objects but also understand gravity itself. “Compared to the other fundamental forces like, e.g. electromagnetism, gravity is extremely weak,” explains Dr. David Andriot, one of the authors of the study. The reason for this weakness could be that gravity interacts with more than the three dimensions in space and one dimension in time that are part of our everyday experience.

Extra dimensions

Extra dimensions that are hidden because they are very small are an indispensable part of string theory—one of the promising candidates for a theory of quantum gravity. A theory of quantum gravity, unifying quantum mechanics and general relativity, is sought after in order to understand what happens when very large masses at very small distances are involved, e.g. inside a black hole or at the Big Bang.

“Physicists have been looking for extra dimensions at the Large Hadron Collider at CERN but up to now this search has yielded no results,” says Dr. Gustavo Lucena Gómez, the second author of the paper. “But gravitational wave detectors might be able to provide experimental evidence.”

The researchers discovered that extra dimensions should have two different effects on gravitational waves: they would modify the “standard” gravitational waves and would cause additional waves at high frequencies above 1000 Hz. However, the observation of the latter is unlikely since the existing ground-based gravitational wave detectors are not sensitive enough at high frequencies.

On the other hand, the effect that extra dimensions can make a difference in how “standard” gravitational waves stretch and shrink space-time might be easier to detect by making use of more than one detector. Since the Virgo detector will join the two LIGO detectors for the next observing run this might happen after late 2018/beginning of 2019.

[1] Max Planck Institute for Gravitational Physics, Albert Einstein Institute,.“Hints of Extra Dimensions in Gravitational Waves?,”(June 28, 2017)

Does Dark Energy Exist?

Does Dark Energy Exist? (Op-Ed)[1]

This image of the Type 1a supernova remnant 0509-67.5 was made using data from NASA’s Hubble Space Telescope and Chandra X-ray Observatory. Analyses of Type 1a supernovae’s motion through space has led astronomers to conclude that the universe’s expansion is accelerating, driven by a mysterious force called dark energy. Credit: NASA, ESA, and B. Schaefer and A. Pagnotta (Louisiana State University, Baton Rouge); NASA, ESA, CXC, SAO, the Hubble Heritage Team (STScI/AURA), J. Hughes (Rutgers University)

Newsflash: the universe is expanding. We’ve known that since the pioneering and tireless work of Edwin Hubble about a century ago, and it’s kind of a big deal. But before I talk about dark energy and why that’s an even bigger deal, I need to clarify what we mean by the word “expanding.”

The actual observation that you can do in the comfort of your own home (provided you have access to a sufficiently large telescope and a spectrograph) is that galaxies appear to be receding from our own Milky Way. On average, of course: galaxies aren’t simple creatures, and some, like our a-little-too-close-for-comfort neighbor Andromeda, are moving toward us. [The Universe: Big Bang to Now in 10 Easy Steps]

This recession is seen in the redshifting of light from those galaxies. The fingerprint frequencies of certain elements are shifted down to lower frequencies, exactly like they are for the Doppler effect. But to explain the cosmological observations as a simple Doppler shift requires a few head-scratching conclusions: 1) We are at the center of the universe; 2) Galaxies have preposterous mechanisms that propel them through space; and 3) The universe conspires to make galaxies twice as far away from us move exactly twice as fast.

That seems like a bit of a stretch, so astronomers long ago reached a much more simple conclusion, one powered by the newfangled general theory of relativity: the space itself between galaxies is expanding, and galaxies are just along for the ride.

Going big

Edwin Hubble established the expansion of the universe by cataloging nearby galaxies (after discovering that there is such a thing as “nearby galaxies”). But the story of dark energy doesn’t get told by neighborhood redshifts. The game of cosmology in the latter half of the 20th century was to go deep. Way deep, which is challenging because deep-space objects are a little dim.

Thankfully, nature gave scientists a break (for once). A certain sub-sub-subclass of supernova explosions, known as Type 1a, has two useful characteristics. Because Type 1a supernovae tend to happen from roughly the same scenario—a white dwarf accretes gas from an orbiting companion until a critical threshold is reached, a nuclear chain reaction goes haywire and boom—they have roughly the same absolute brightness.

By comparing the observed brightness of a Type 1a supernova to the known true brightness (calibrated using handy nearby sources), a little high-school trigonometry reveals a distance. But wait, there’s more! Since Type 1a supernovae contain the same mix of elements, we can easily identify their fingerprint frequencies and measure the redshift, and hence a speed.

Distance and speed all in one measurement. How convenient. [Supernova Photos: Great Images of Star Explosions]

Going long

Type 1a supernovae are relatively rare—only a small handful will light up each galaxy every century. But since there are so many galaxies in the universe, they’re constantly popping off somewhere. And they’re insanely bright, too. For a few weeks, a single explosion can outshine its entire host galaxy. That’s hundreds of billions of stars for those of you keeping track.

As the light travels to our telescopes from a distant supernova, the expansion of the universe will stretch it out to longer wavelengths. The further in the past the supernova exploded, the longer the light has traveled to reach us, and the more stretching it has accumulated.

So a single supernova redshift measurement gives us the total amount of universal stretch in the intervening billions of years between us and the explosion. By performing multiple measurements at multiple distances, we can build a cosmic growth chart, mapping the expansion of the universe as a function of its age.

And that’s where dark energy enters the fray.

Going dark

In the 1990s, after a decade of technology development, the stage was finally set for supernovae to shed some light on the expansion of the universe. Specifically, its deceleration. In a universe full of matter, the expansion should slowly be wearing out as its gravitational pull tugs back. We didn’t know how much matter was in the universe, but a measurement of the cosmic growth chart would help pin it down.

Easy, peasy.

At first the results were promising: two competing groups both provided initial results of a detectable deceleration rate, but with necessarily large error bars (they were just getting started, after all). But in the coming months, things started to go downhill.

As more supernovae data came back from the surveys, the measured deceleration shrank. Then vanished. Then reversed.

It appeared that the expansion of the universe was accelerating.

Both groups frantically tried to figure out the bugs in their data-analysis pipelines. Surely something was amiss, and each was worried that the other group might steal its thunder by publishing a sound measurement while it was still fiddling with its codes.

But the data refused to budge. Nervously, cautiously, the groups reached out to each other: “Do you see what we see?”

It was then that the groups began to appreciate what the universe was telling them. Two competing teams, using different telescopes, different datasets and different methodologies, were independently coming to the same conclusion. Our universe wasn’t slowing down, but speeding up.

They published their work almost 20 years ago. In the meantime, after several independent lines of evidence all pointed to the same conclusion, they shared in a Nobel Prize for their unexpected discovery. The name for that observed phenomenon—dark energy—sticks with us today, but we still don’t understand it. We don’t know why the expansion of the universe is accelerating, but we do know that it does accelerate.

[1] By Paul Sutter, Astrophysicist “Does Dark Energy Exist? (Op-Ed),” Space.com (June 28, 2017). Paul Sutter is an astrophysicist at The Ohio State University and the chief scientist at COSI Science Center. Sutter is also host of Ask a Spaceman, We Don’t Planet, and COSI Science Now. Sutter contributed this article to Space.com’s Expert Voices: Op-Ed & Insights.

Origin of the Universe

Origin of the Universe[1]

For centuries, people have puzzled over how our Universe began. But the heat just got turned way up on a debate that’s quietly been raging between cosmologists, with 33 of the world’s most famous physicists publishing a letter angrily defending one of the leading hypotheses we have for the origin of the Universe.

The letter is in response to a Scientific American feature published back in February (2017), in which three physicists heavily criticized inflation theory—the idea that the Universe expanded just like a balloon shortly after the Big Bang. The article went as far as claiming that the model “cannot be evaluated using the scientific method“—the academic equivalent of saying it isn’t even real science.

In response, 33 of the world’s top physicists, including Stephen Hawking, Lisa Randall, and Leonard Susskind, have fired back by publishing their own open letter in Scientific American. The Cliff’s note version is this: they’re really angry.

Inflation theory was first proposed by cosmologist Alan Guth, now at MIT, back in 1980. It’s based on the idea that a fraction of a second after the Big Bang, the Universe expanded rapidly, spinning entire galaxies out of quantum fluctuations.

“By the time it slowed down, what had been a tiny, quivering quantum realm was stretched out until it looked smooth and flat, save for speckles of denser matter that later became galaxies, stars, and planets,” writes Joshua Sokol for The Atlantic.

In the following years, Guth’s original idea was improved and updated by Stanford physicists Andrei Linde, and they’ve since spent their careers refining the inflation model—which has become the leading theory for how the Universe was born.

In fact, most of us were taught inflation theory at high school and university when discussing the Universe’s origins.

Guth and Linde, along with cosmologists David Kaiser and Yasunori Nomura, were the ones who recruited the other 29 signees behind this week’s letter.

Interestingly, one of Guth and Linde’s former colleagues, physicist Paul Steinhardt, is part of the trio they’re rallying against. Guth, Linde, and Steinhardt all shared the prestigious Dirac prize “for develop-ment of the concept of inflation in cosmology” back in 2002.

But in the years since, Steinhardt has gone rogue, and has become an active critic of inflationary theory. He was one of the authors of Scientific American’s February feature, originally titled “Pop goes the Universe”, along with Princeton physicist Anna Ijjas, and Harvard astronomer Abraham Loeb.

That article highlighted recent research into the cosmic microwave background, which doesn’t match up with the predictions of inflationary theory.

It also criticized the fact that inflation would have generated primordial gravitational waves, which have never been found.

“The data suggest cosmologists should reassess this favored paradigm and consider new ideas about how the universe began,” summarizes an In Brief wrap up of the article.[2]

That criticism in itself wasn’t a huge deal—these kinds of arguments are healthy in the science world.

But what really pissed off Guth, Linde, and the 31 other signees, was the suggestion that inflationary theory couldn’t actually be tested in the first place, and therefore wasn’t really science.

“They [made] the extraordinary claim that inflationary cosmology ‘cannot be evaluated using the scientific method’ and go on to assert that some scientists who accept inflation have proposed ‘discarding one of [science’s] defining properties: empirical testability,’ thereby ‘promoting the idea of some kind of nonempirical science’,” the physicists write in their open letter.

“We have no idea what scientists they are referring to. We disagree with a number of statements in their article, but in this letter, we will focus on our categorical disagreement with these statements about the testability of inflation.”

Their argument is that inflation theory is based on many models, and there’s no illusion that all of these models are correct. Over the past 37 years, some of the models have made correct, testable predictions – including the average mass density of the Universe, and its flat shape. Many are still unresolved.

But either way, these models are all testable, which means they’re proper science, and they can be proven or disproven depending on the evidence we find in the coming years.

Ryan F. Mandelbaum has done incredible coverage of this feud over at Gizmodo, and points to a blog entry by Sean Carroll, one of the physicists who signed the letter, on the controversy:

“We judge theories by what predictions they make that we can test, not the ones they make that can’t be tested. It’s absolutely true that there are important unanswered questions facing the inflationary paradigm. But the right response in that situation is to either work on trying to answer them, or switch to working on something else (which is a perfectly respectable option). It’s not to claim that the questions are in principle unanswerable, and therefore the field has dropped out of the realm of science.”

The authors of the original article have since responded to the letter with their own extended FAQ on the debate. And they maintain their position—that inflation was once testable, but “what began in the 1980s as a theory that seemed to make definite predictions has become a theory that makes no definite predictions”.

Which takes us right back to where we started… some cosmologists have publicly slammed inflation theory, and others have angrily responded.

Unfortunately there’s no neat resolution to this debate on the horizon, with both sides standing pretty firm. The one thing they both agree on is the fact that inflation theory isn’t perfect, and we should all keep an open mind about what really happened at the birth of our Universe as new data comes in.

Or as Guth told Mandelbaum in the ultimate mic drop when asked what would happen next: “I think we’ll all continue on with our research.”

You can read the original article here[3], the responding open letter here, and the original authors’ response here.

[1] Fiona Macdonald, “Stephen Hawking And 32 Top Physicists Just Signed a Heated Letter on The Universe’s Origin,” (May 12, 2017) Sciencealert.com

[2] Unless you are a subscriber to Scientific American, you cannot view the Brief Summary linked. However, the Cliff Notes version of the Cliff Notes would be “The latest astrophysical measurements, combined with theoretical problems, cast doubt on the long-cherished inflationary theory of the early cosmos and suggest we need new ideas.”

[3] Requires Scientific American subscription to see the entire article.