by Steve Koppes, The University of Chicago News Office

UChicago scientists receiving NSF CAREER Awards were Daniel Holz and David Schuster, assistant professors in physics. The NSF presents CAREER Awards to junior faculty members who exemplify the role of teacher-scholars through outstanding research, excellent education, and the integration of education and research.

Holz will use his $600,000 CAREER Award to fund a project titled "Hearing and Seeing the Universe Through Multi-Messenger Astronomy." He will study how black holes and/or dead, compact stars spiral toward one another and eventually merge. These events produce copious gravitational waves, and are thought to be associated with gamma-ray bursts, which are some of the most powerful explosions in the universe.

In particular, Holz explores how the combination of electromagnetic (such as optical, gamma-ray, and X-ray) telescopes and future gravitational-wave observatories can elucidate these spectacular events. "Questions to be explored include how often these sources happen, how we might detect them both in gravitational waves and electromagnetically, and what we might learn from them," Holz said. He is particularly interested in the powerful cosmological measurements that multi-messenger observations will enable.

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KICP Members: Daniel Holz

by Steve Koppes, The University of Chicago News Office

Visitors to the USA Science and Engineering Festival in Washington, D.C. will get a taste of the South Pole Telescope when a traveling exhibit comes their way beginning April 28. The University of Chicago's Kavli Institute for Cosmological Physics will present the exhibit, "100 Years of Exploration @ South Pole: From Survival to Science," which was produced by a studio class at the School of the Art Institute of Chicago.

Part of the exhibit will appear at the World Science Festival, which takes place May 30 to June 3 in New York City, including the June 3 World Science Street Festival in Washington Square Park.

The exhibit was a class project led by Bo Rodda, an adjunct professor of the SAIC's department of architecture, interior architecture and designed objects. He also is a building intelligence and energy efficiency specialist at Argonne National Laboratory, which is a member of the SPT collaboration.

"The students, for the most part, all signed up for the class because they are naturally interested in space and science," said Rodda, whose class met with scientists at UChicago and Adler Planetarium before designing the exhibit.

"Artists and scientists have much more in common than most people would think. At the root of what drives us, I feel, is an insatiable curiosity about the world and a desire to discover. When artists and scientists begin to work together, amazing things happen," he said.

South Pole milestones
Exploration and research at the South Pole passed a milestone on Dec. 14, 2012, the centennial of Roald Amundsen's arrival at the South Pole. The SPT also has passed a milestone, having obtained some major results while completing its initial large survey of the sky. UChicago leads the SPT collaboration, which includes a dozen institutions worldwide.

"These all motivated the notion of looking for ways to share this with broader audiences: to allow them to explore the unique research environment that the Amundsen-Scott South Pole station offers, and to share in the excitement of discovery," said Randy Landsberg, the Kavli Institute's director of education and outreach.

The Kavli-SAIC collaboration sprouted from the 2007 Chicago Festival of Maps. The institute organized a five-day meeting in connection with the multi-institutional festival titled "Cosmic Cartography: Mapping the Universe from the Big Bang to the Present."

The involvement of both institutions in the festival led to a series of collaborative projects, including two UChicago Brinson Lectures at the Art Institute last year, one featuring Astronomer Royal Martin Rees, the other spotlighting Nobel laureate John Mather.

In another joint project, this spring the Art Institute also is offering a course titled "The Leading Edge of Astrophysics," taught by Kathryn Schaffer, a senior researcher at KICP and member of the SPT science team. A series of Kavli postdoctoral scientists have presented guest lectures about their current research as part of the course, then took questions from the students.

Surveys given before and after the presentations document how the presentations may have changed the perceptions that the art students had about scientists. The postdocs also took surveys to record how their interactions with the students may have changed what the scientists viewed as important about communicating their work to a lay audience.

Joint conversations on art and science also are in the offing in an initiative led by SAIC President Walter E. Massey, a former physics professor and vice president for research at UChicago, who also has served as director of Argonne and of the Nationabl Science Foundation.

Enhanced outreach
"We look for things that are of interest to both groups, and this year it came up that the South Pole Telescope collaboration wanted to do more outreach," said Landsberg, who took the exhibit idea to Doug Pancoast, chairman of SAIC's architecture department.

"We had originally just asked for a simple outdoor photography exhibit. We were thinking 10 nice photos mounted, and these guys came up with this engaging interactive exhibit, which is fantastic. The entire process was a wonderful collaborative experience that engaged both the artists and the scientists, and produced a tangible result," Landsberg said.

Exhibit visitors will have the opportunity to don a heavy jacket, gloves and boots and get photographed in front of a giant backdrop of the ceremonial South Pole. At a nearby multi-touch table, visitors also can use their fingers to manipulate electronic images taken at the South Pole and view SPT data.

Leul Bezane, a fourth-year in physics at UChicago, programmed the touch table and formatted its images. Bezane works as a research assistant in Adler's Space Visualization Laboratory and at the Kavli Institute, where he helps program galaxy simulations for Nick Gnedin, associate professor in astronomy & astrophysics.

The rest of the exhibit, though, was the work of the students.

"We had a real client, with real needs, with a real budget, and very, very real deadlines," said Rodda. The students brought interdisciplinary backgrounds to the project, spanning architecture, interior architecture, object design (industrial design), graphic design, education and even sculpture.

"Everyone had a vital role to play and working together they made an incredible exhibit. I am extremely proud of what they have accomplished and I know they are, too," Rodda said.

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KICP Members: John E. Carlstrom; Nickolay Y. Gnedin; Randall H. Landsberg; Tom Plagge; Kathryn Schaffer; Mark Subbarao
KICP Students: Leul Bezane; Lindsey E. Bleem; Abigail T. Crites; Tyler Natoli; Kyle Story
Scientific projects: South Pole Telescope (SPT)

by Steve Koppes, The University of Chicago News Office

Analysis of data from the 10-meter South Pole Telescope is providing new support for the most widely accepted explanation of dark energy - the source of the mysterious force that is responsible for the accelerating expansion of the universe.

The results also are beginning to hone in on the masses of neutrinos, the most abundant particles in the universe, which until recently were thought to be without mass.

The data strongly support Albert Einstein's cosmological constant - a slight amendment to his theory of general relativity and the leading model for dark energy - even though the analysis was based on only a fraction of the SPT data collected and only 100 of the more than 500 galaxy clusters detected so far.

"With the full SPT data set, we will be able to place extremely tight constraints on dark energy and possibly determine the mass of the neutrinos," said Bradford Benson, a postdoctoral scientist at the University of Chicago's Kavli Institute for Cosmological Physics. Benson presented the SPT collaboration's latest findings on April 1 at the American Physical Society meeting in Atlanta.

A series of papers detailing the SPT findings have been submitted to the Astrophysical Journal, written by lead authors Benson; Kavli postdoctoral scientist Ryan Keisler; and Christian Reichardt, postdoc at the University of California, Berkeley.

The results are based on a new method that combines measurements taken by the SPT and X-ray satellites, and extends these measurements to larger distances than previously achieved using galaxy clusters.

The most widely accepted property of dark energy is that it leads to a pervasive force acting everywhere and at all times in the universe. This force could be the manifestation of Einstein's cosmological constant, which effectively assigns energy to empty space, even when it is free of matter and radiation. Einstein introduced the cosmological constant into his theory of general relativity to accommodate a stationary universe, the dominant idea of his day. He later considered it to be his greatest blunder after the discovery of an expanding universe.

In the late 1990s, astronomers discovered that the expansion of the universe appeared to be accelerating, according to cosmic distance measurements based on the brightness of exploding stars. Gravity should have been slowing the expansion, but instead it was speeding up.

Einstein's cosmological constant is one explanation of the observed acceleration of the expanding universe, now supported by countless astronomical observations. Others hypothesize that gravity could operate differently on the largest scales of the universe. In either case, the astronomical measurements are pointing to new physics that have yet to be understood.

Clues to dark energy lurking in 'shadows'
The SPT was specifically designed to tackle the dark energy mystery. The 10-meter telescope operates at millimeter wavelengths to make high-resolution images of the cosmic microwave background radiation (CMB), the light left over from the big bang. Scientists use the CMB in their search for distant, massive galaxy clusters, which can be used to pinpoint the mass of the neutrino and the properties of dark energy.

"The CMB is literally an image of the universe when it was only 400,000 years old, from a time before the first planets, stars and galaxies formed in the universe," Benson said. "The CMB has travelled across the entire observable universe, for almost 14 billion years, and during its journey is imprinted with information regarding both the content and evolution of the universe."

As the CMB passes through galaxy clusters, the clusters effectively leave "shadows" that allow astronomers to identify the most massive clusters in the universe, nearly independent of their distance.

"Clusters of galaxies are the most massive, rare objects in the universe, and therefore they can be effective probes to study physics on the largest scales of the universe," said John Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy & Astrophysics, who heads the SPT collaboration.

"The unsurpassed sensitivity and resolution of the CMB maps produced with the South Pole Telescope provides the most detailed view of the young universe and allows us to find all the massive clusters in the distant universe," said Christian Reichardt, a postdoctoral researcher at the University of California, Berkeley, and lead author of the new SPT cluster catalog paper.

The number of clusters that formed over the history of the universe is sensitive to the mass of neutrinos and the influence of dark energy on the growth of cosmic structures.

"Neutrinos are amongst the most abundant particles in the universe," Benson said. "About one trillion neutrinos pass through us each second, though you would hardly notice them because they rarely interact with ‘normal’ matter."

The existence of neutrinos was proposed in 1930. They were first detected 25 years later, but their exact mass remains unknown. If they are too massive they would significantly affect the formation of galaxies and galaxy clusters, Benson said.

The SPT team has now placed tight limits on the neutrino masses, yielding a value that approaches predictions stemming from particle physics measurements.

"It is astounding how SPT measurements of the largest structures in the universe lead to new insights on the evasive neutrinos," said Lloyd Knox, professor of physics at the University of California at Davis and member of the SPT collaboration. Knox also will highlight the neutrino results in his presentation on Neutrinos in Cosmology at a special session of the APS on April 3.

The South Pole Telescope collaboration is led by the University of Chicago and includes research groups at Argonne National Laboratory, Cardiff University, Case Western Reserve University, Harvard University, Ludwig-Maximilians-Universität, Smithsonian Astrophysical Observatory, McGill University, University of California at Berkeley, University of California at Davis, University of Colorado at Boulder, University of Michigan, as well as individual scientists at several other institutions.

Members of the Kavli Institute for Cosmological Physics participating in the South Pole Telescope collaboration include faculty members John Carlstrom, who leads the effort; Mike Gladders, Wayne Hu, Andrey Kravtsov and Steve Meyer; senior researchers Clarence Chang, Tom Crawford, Erik Leitch and Kathryn Schaffer; postdoctoral scientists Bradford Benson, F. William High, Steven Hoover, Ryan Keisler, Jared Mehl and Tom Plagge; and graduate students Lindsey Bleem, Abby Crites, Monica Mocanu, Tyler Natoli and Kyle Story.

The SPT is funded primarily by the National Science Foundation's Office of Polar Programs. Partial support also is provided by the NSF-funded Physics Frontier Center of the KICP, the Kavli Foundation, and the Gordon and Betty Moore Foundation.

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KICP Members: Bradford A. Benson; John E. Carlstrom; Clarence L. Chang; Thomas M. Crawford; Michael D. Gladders; Fredrick W. High; Stephen Hoover; Wayne Hu; Ryan Keisler; Andrey V. Kravtsov; Erik Leitch; Jared Mehl; Stephan S. Meyer; Tom Plagge; Kathryn Schaffer
KICP Students: Lindsey E. Bleem; Abigail T. Crites; Monica Mocanu; Tyler Natoli; Kyle Story
Scientific projects: South Pole Telescope (SPT)

SpaceRef

Peter Rejcek, Antarctic Sun Editor: Its five-year mission: To survey the early universe for massive galaxy clusters, a search designed to understand more about one of cosmology's greatest mysteries -- dark energy. Mission complete. Now it's time for something new.

The South Pole Telescope (SPT), the largest such instrument ever installed at the U.S. Antarctic Program's research station at the bottom of the world, completed its scan of 2,500-square degrees of night sky at the end of the 2011 winter. The 10-meter telescope has spied hundreds of previously unseen galaxy clusters, including the most massive ever detected, since seeing its first light at the beginning of the 2007 South Pole winter.

"We're trying to understand what dark energy could be, and our way of looking at it is to see the structures involved," explained John Carlstrom, principal investigator for the experiment, which includes dozens of collaborators. "The project as a whole has been more successful than any of us thought."

Galaxy clusters, thanks to the pull of gravity, are the largest structures to have evolved in the cosmos. The SPT hunts for them using the Sunyaev-Zel'dovich (SZ) effect -- a small distortion in the cosmic microwave background (CMB), a "glow" left over from the Big Bang some 14 billion years ago. Such distortions are created as background radiation passes through a large galaxy cluster -- effectively creating a shadow from the cluster in the microwave background.

In 2008, the telescope detected its first galaxy clusters using the SZ effect. Two years later, astronomers announced the discovery of the most massive galaxy cluster yet, tipping the scales at the equivalent of 800 trillion suns, and holding hundreds of galaxies.

Mapping the number of such clusters over the history of the universe can tell researchers how much influence dark energy had on their growth, according to Bradford Benson, a postdoctoral research fellow at the University of Chicago. He is also the lead author of a recent paper that puts additional constraints, based on SPT data, on the models cosmologists use to understand a universe increasingly dominated by dark energy.

It sounds like a disembodied entity that Captain Kirk and company might battle in an episode of Star Trek. Dark energy is the prevalent explanation for the accelerating expansion of the universe. Dark energy appears to counteract the gravitational attraction between galaxies.

In a younger, smaller universe billions of years ago, gravity had a greater influence, allowing galaxy clusters to grow and clump together like dust bunnies on a wood floor. In a study last year using SPT data, lead author Christian L Reichardt, with the University of California, Berkeley, and colleagues found that dark energy accounted for no more than 1.8 percent of the total energy-density of the universe at a time when it was only 400,000 years old. Today, dark energy accounts for more than 70 percent of all the matter and energy in the universe.

"Everything is getting diluted. Dark energy is just sitting there," said Carlstrom, director of the Kavli Institute of Cosmological Physics at the University of Chicago. "In the future, it dominates. Right now it is two-thirds of the energy-density of the universe."

Now, Carlstrom, Benson and their team want to peer back to near the beginning of time, a fraction of a moment after the Big Bang, when the universe expanded exponentially, a theory known as inflation.

During the 2011-12 season, they swapped the telescope's high-tech "camera" purposefully designed to detect the SZ effect with one sensitive to the signature left by cosmic inflation on the pattern of the CMB.

CMB radiation, often referred to as a faint hiss of microwaves, comes from every direction in the sky. It is almost a perfectly uniform plasma, with a temperature of 2.7 degrees above absolute zero on the Kelvin scale.

But it contains "hot" and "cold" spots that are slight irregularities in its near-perfect uniformity, which is known as anisotropy. These spots can tell cosmologists something about the geometry of the universe, the amounts and types of dark matter and energy that make up the cosmos, and even something about the universe's ultimate fate.

The inflation theory holds that the rapid expansion of space-time would generate gravity waves and leave a unique signature when they interact with the plasma. This signature would be a spiral pattern in the polarization of CMB, often referred to as B-mode polarization, which would look like hurricanes in a hypothetical map of the polarization of the CMB.

"Now, we want to do an even more powerful experiment," Carlstrom said.

Switching experiments required more than just upgrading the technology for the telescope receiver. The shielding that prevents interference from the horizon must be augmented. That meant turning the telescope's round 10-meter reflector shield into an octagon by extending the shielding around the dish by about 1 meters.

"We're making a much quieter telescope. Guarding it from the ground, guarding it from the atmosphere, and making sure all the receiver can see is the sky," Carlstrom noted.

The SPT-Pol receiver, for polarization, is a three-year project. While the new experiment will focus on finding the inflation signal, or at least setting new constraints, the SPT will also continue to map galaxy clusters with even more sensitive sensors but on a small pie of the sky.

"We'll go much, much deeper, and do the same kind of science, but much more sensitive than what we have been doing. We're adding more capability; we're not walking away from what we've been doing, we're going much deeper with the dark energy experiment," Carlstrom said.

Other telescopes at the South Pole are also after the B-mode polarization predicted by the theory of inflation, including the Background Imaging of Cosmic Extragalactic Polarization telescope, or BICEP. Far smaller on the ground than the SPT, BICEP can scan the CMB on much larger angular scales.

In contrast, the SPT focuses on smaller angular scales with greater detail, even delving into particle physics, including revealing characteristics about subatomic particles called neutrinos. Another experiment at the South Pole, the IceCube Observatory, buried deep into the ice sheet, is attempting to detect high-energy neutrinos as the pass through the Earth to learn about cosmic events like supernovas.

"One of our goals is to search in complementary [fashion] with BICEP for B-modes," Carlstrom said. "We'll try to measure gravitational waves. At the same time, we'll do this very cool physics experiment figuring out what the total sum of the masses of the different neutrinos are."

Indeed, the SPT has proven itself to be the Swiss Army knife of CMB telescopes.

In addition to mapping galaxy clusters, it has also detected the bright thermal emissions from early star-forming galaxies -- something no one expected to see.

"It's a whole new window on the universe that was discovered with that," Carlstrom said.

Benson said the plan going forward in the years to come would be to also measure more of the dusty, star-generating galaxies of the early universe.

"We can potentially map out the entire star formation history of the universe, from the very first stars to the peak of star formation in the universe billions of years later," he said.

And that's just what the SPT has to say about this universe. Carlstrom explained that the theory of inflation, in one interpretation, assumes a pre-existing "piece" of space-time, something almost inconceivably small with such a high energy density capable of inflating the whole universe.

"It should happen all the time," he said nonchalantly. "Inflation gives you an answer to the question, 'Where did our universe come from?' It comes from some other space-time. People call it the multiverse."

Astronomy at the South Pole truly has reached the final frontier.

"We're thrilled. We're excited. We're just feeding on it," Carlstrom said.

NSF-funded research in this story: John Carlstrom, University of Chicago, Award Nos. 0638937 and 0959620.

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KICP Members: John E. Carlstrom
Scientific projects: South Pole Telescope (SPT)

by Steve Koppes and Ray Villard, The University of Chicago News Office

Thanks to the presence of a natural "zoom lens" in space, University of Chicago scientists working with NASA's Hubble Space Telescope have obtained a uniquely close-up look at the brightest gravitationally magnified galaxy yet discovered.

The imagery offers a visually striking example of gravitational lensing, in which one massive object’s gravitational field can magnify and distort the light coming from another object behind it. Such optical tricks stem from Einstein's theory of general relativity, which describes how gravity can warp space and time, including bending the path that light travels.

In this case, gravity from the galaxy cluster RCS2 032727-132623 bent and amplified the light coming from a much more distant galaxy, 10 billion light-years from Earth. This "gravitational telescope" creates a vast arc of light, as if the distant galaxy had been reflected in a funhouse mirror. The UChicago team reconstructed what the distant galaxy really looks like, using computational tools that reversed the effect of gravitational lensing.

"What's happening here is a manifestation of general relativity," said Michael Gladders, assistant professor in astronomy & astrophysics at UChicago. "Instead of seeing the normal, faint image of that distant source, you see highly distorted, highly magnified, and in this case, multiple images of the source caused by the intervening gravitational mass."

The cosmic lens gave the UChicago team the unusual opportunity to see what a galaxy looked like 10 billion years ago. The reconstructed image of the galaxy revealed regions of star formation glowing like bright points of light. These are much brighter than any star-formation region in Earth's home galaxy, the Milky Way.

'Looking at the nature of dark matter'
In 2006 the Chicago astronomers used the Very Large Telescope in Chile to measure the arc's distance and calculated that the galaxy appears more than three times brighter than previously discovered lensed galaxies. Then last year, Jane Rigby of NASA's Goddard Space Flight Center in Greenbelt, Md., and the Chicago team imaged the arc with the Hubble Space Telescope's Wide Field Camera 3.

Using this gravitational lens as a telescope offers two major scientific opportunities, Gladders said. First, "It gives us a look at that very distant source with a precision and fidelity that we couldn't otherwise achieve," he said.

And second, it provides an opportunity to learn something about the lens-forming mass, which is dominated by dark matter. "It's really a way of looking at the nature of dark matter," Gladders said. Dark matter accounts for nearly 90 percent of all matter in the universe, yet its identity remains one of the biggest mysteries of modern science.

Keren Sharon, a postdoctoral scholar at UChicago's Kavli Institute for Cosmological Physics, led the effort to perform a detailed reconstruction of the lensed galaxy. She and her co-authors, including Gladders, NASA's Rigby and UChicago graduate student Eva Wuyts, published their findings last month in the Astrophysical Journal.

Sharon painstakingly created a computer reconstruction of the gravitational lens, then reverse-engineered the distorted image to determine the distant galaxy's actual appearance. "It's a little bit of an art, but there's a lot of physics in it. That's the beauty of it," Sharon said. "It was a fun puzzle to solve, especially when we had such great data."

Gladders said Sharon is "one of the world experts on exactly how to do this. Combine that degree of finesse with this quality of data, and you get a very nice result. This object now becomes not only the brightest-lensed source known, but because of this analysis, it is also going to be one of the best-understood sources."

Through spectroscopy, the spreading out of light into its constituent colors, the team plans to analyze the distant galaxy's star-forming regions from the inside out to better understand why they are forming so many stars.

The team also has obtained data from one of the twin Magellan Telescopes to help them determine why the galaxy, which is 10 billion light years away, looks so irregular.

"It's not like we have something to compare it to," Sharon said. "We don't know what other galaxies at the same distance look like at this level of detail."

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KICP Members: Michael D. Gladders; Keren Sharon
KICP Students: Eva Wuyts

The Economist

The dark side of the universe
Scientists are trying to understand why the universe is running away from them

AT FIVE tonnes and 520 megapixels, it is the biggest digital camera ever built-which is fitting, because it is designed to tackle the biggest problem in the universe. On February 20th researchers at the Cerro Tololo Inter-American Observatory, which sits 2,200 metres (7,200 feet) above sea level in the Atacama desert of northern Chile, will begin installing this behemoth on a telescope called Blanco. It is the centrepiece of the Dark Energy Survey (DES), the most ambitious attempt yet to understand a mystery as perplexing as any that faces physics: what is driving the universe to expand at an ever greater rate.

It has been known since the late 1920s that the universe is getting bigger. But it was thought that the expansion was slowing. When in 1998 two independent studies reached the opposite conclusion, cosmology was knocked head over heels. Since then, 5,000 papers have been written to try to explain (or explain away) this result. "That's more than one a day," marvels Saul Perlmutter, of the Lawrence Berkeley National Laboratory, who led the Supernova Cosmology Project-one of the studies that was responsible for dropping the bombshell. Last October that work earned Dr Perlmutter the Nobel prize for physics, which he shared with Brian Schmidt and Adam Riess, who led the other study, the High-Z Supernova Search.

Many of those 5,000 papers deal with something that has come to be known as dark energy. One reason for its popularity is that, at one fell swoop, it explains another big cosmological find of recent years. In the early 1990s studies of the cosmic microwave background (CMB), an all-pervading sea of microwaves which reveals what the universe looked like when it was just 380,000 years old, showed that the universe, then and now, was "flat". However big a triangle you draw on it-the corners could be billions of light years apart-the angles in it would add up to 180^o, just as they do in a school exercise book.

That might not surprise people whose geometrical endeavours have never gone beyond such books. But it surprised many physicists. At some scales space is not at all flat: the power of Albert Einstein's theory of general relativity lies in its interpretation of gravity in terms of curved space. Cosmologists were quite prepared for it to be curved at the grandest of scales, and intrigued to discover that it was not.

Dark thoughts
Relativity says that for the universe to be flat, it has to have a very particular density-which in relativity is a measure not just of the mass contained in a certain volume, but also of the energy. The puzzle was that various lines of evidence showed that the universe’s endowment of ordinary matter (the stuff that people, planets and stars are made of) would give it just 4% of that density. Adding in extraordinary matter-"dark matter", not made of atoms, that interacts with the rest of the universe almost only by means of gravity-gets at most an extra 22%. That left almost three-quarters of the critical density unaccounted for. Theorists such as Michael Turner, of the University of Chicago, became convinced that there was something big missing from their picture of the universe.

Whatever it is that is driving the universe's accelerating expansion fits the bill rather well. Add the amount of energy needed to keep cosmic acceleration going to the amount of matter and energy in the universe already accounted for and you have more or less exactly the density of matter and energy needed to make the universe flat. But there is a catch; for the sums to tally, that "dark energy" - Dr Turner is thought to have coined the term - must be very strange stuff indeed. According to Einstein's theory of relativity, energy in the form of radiation has the same sort of gravitational effect as matter does - the photons of which light is made exert a pressure, and this in turn gives rise to a gravitational attraction. In order to drive its acceleration, then, dark energy must instead have a repulsive effect. It must, in other words, exert a negative pressure.

Divide dark energy's pressure (negative) by its energy density (positive) and you get something cosmologists label "w". It is easy to see that w must be negative. Observations made since 1998 suggest that w is pretty close to -1. If it were found to be exactly -1, that would make dark energy something physicists call a cosmological constant. A cosmological constant is the same no matter where in the universe you look - an inherent, unchanging feature of the fabric of creation, however much it expands, twists or ties itself in knots.

The cosmological constant is another thing first dreamed up by Einstein. On realising that the equations of general relativity allowed for the universe’s expansion (or, indeed, contraction), he added a parameter describing just such a constant in order to keep it from doing either. For all his notoriously counterintuitive predictions, an expanding universe was one he was not prepared to countenance, at least not in 1917, when he published his theory. After Edwin Hubble's discovery 12 years later that other galaxies were indeed streaming away from Earth's Milky Way backyard, Einstein dropped the tweak. No doubt miffed that he had not trusted his maths in the first place, he later called the cosmological constant his "biggest blunder".

By then, though, the cosmological constant had been seized upon by quantum theorists, themselves in the midst of turning physics on its head. Quantum theory says that the seemingly empty vacuum of space is, in fact, not empty at all. Instead it is constantly abuzz with "virtual" particles flitting in and out of existence. The energy resulting from all this buzzing - vacuum energy - should be a fixed feature of space - in other words, a cosmological constant.

Stringing it all together
And, in principle, it could also propel the universe's expansion. Thus vacuum energy and dark energy might be the same thing. But this theoretical neatness runs into a practical problem. A naive approach to quantum theory says that vacuum energy should be a whopping 10⁶⁰ to 10¹²⁰ times bigger than dark energy's estimated energy density. Some physicists call this "the worst prediction ever". Working out why vacuum energy is not so vast has been a problem for physics ever since.

Cliff Burgess, from Perimeter Institute for Theoretical Physics in Waterloo, Ontario, and the author of a handful of the 5,000 papers Dr Perlmutter has dug up, thinks he has a solution; the vacuum energy is vast, but it is almost all hidden away in extra spatial dimensions. Unlike the familiar three of length, breadth and height, these extra dimensions are curled up so tightly that they elude detection (though scientists are trying to prise them open in particle accelerators like the Large Hadron Collider near Geneva). Extra dimensions are of interest because string theory, a class of mathematical models based on quantum theory that seeks to describe reality in the most fundamental way, requires that there be at least six of them, maybe more.

What makes Dr Burgess's proposal unusual is that he went out on a limb and suggested that these energy-sapping, curled-up extra dimensions should be as big as a few microns across, gargantuan by string-theory standards. The reason they have not been noticed by chipmakers, virologists and others who pay attention to things on the micron scale, he contends, is that, like dark matter, they are sensitive only to gravity, and relatively oblivious to the other three of nature's fundamental interactions: electromagnetism and the weak and strong nuclear forces. This may sound like a cheap excuse but it makes robust mathematical sense. And it makes predictions; at micron scales the attraction between two masses will no longer depend on the square of the distance between them in the way that physicists since Newton have required it to.

An experiment under way at the University of Washington, led by Eric Adelberger, tests this idea using the world's most sensitive torsion balance, a souped-up version of the kit Henry Cavendish, an English physicist, used to measure gravity directly for the first time in the late 18th century. It consists of a disk with holes around its edge hanging horizontally from a cord, microns above another, similarly perforated plate. When the bottom disk is rotated the material between its holes exerts a tiny gravitational tug on the material between the holes of the top disk, causing it to rotate, albeit only by billionths of a degree. So far, Sir Isaac is winning. Dr Adelberger has confirmed that Newton's predictions are correct down to 44 microns. But the experiment continues, and Dr Burgess is taking bets that Newton's winning streak will not last much longer.

If Dr Burgess is right, vacuum energy and dark energy are the same thing, a cosmological constant, and w is exactly equal to -1. What, though, if it is not? Then dark energy would have to be something that varies in space, time, or both, and is close to -1 today just by coincidence. Names applied to this something else include quintessence, k-essence, phantom energy and a bunch more, depending on which theorist you ask and what properties you think likely. It would be a new fundamental force, one that rears its head only at vast cosmic distances.

An alternative is to monkey with one of the existing forces. Some physicists would rather fiddle with Einstein's theory of relativity, for instance by making gravity weaker at extremely long ranges. This is tricky. It is notoriously hard to modify the equations of general relativity without damaging the theory beyond repair. That is one reason for their enduring appeal. Another is that they have been confirmed time and again by tests that range from minute measurements of bodies circling the solar system to observations of the farthest known light sources, quasars, billions of light years from Earth. Any new theory, then, has its work cut out-which has not, of course, stopped theorists trying.

The more precisely w comes to look like -1, the more enthusiasm there will be for cosmological constant theories, which require that value, and the less enthusiasm there will be for fifth forces and modified gravity, part of the charm of which is that they can work with other values. This is where telescopes like Cerro Tololo come in. Existing data from ground-based and space telescopes put w at between -1.1 and -0.9. DES will aim to narrow the margin of uncertainty down to just 0.01. To do so, it will take 400 one-gigabyte snaps a night for 525 nights over five years (the remaining telescope time will be split between other science projects). And it will use an array of clever techniques to analyse the data.

The first is a time-honoured method borrowed from Dr Perlmutter, Dr Schmidt and Dr Riess and used to study exploding stars called supernovae. These come in different varieties. Some, called type Ia, always explode with almost exactly the same energy. They are, therefore, equally bright. Since brightness decreases in a predictable way with distance, type Ia supernovae make excellent cosmic yardsticks. Since the speed of light is constant, knowing how far away such a "standard candle" is (calculated from its apparent brightness seen from Earth) is to know how long ago it exploded. The rate at which stars and galaxies are moving away from Earth, meanwhile, can be worked out from their redshift. As light travels across space, which is stretching, its wavelength, too, is stretched and its frequency shifts towards the red end of the spectrum. The faster the expansion, the greater the redshift.

What the Supernova Cosmology Project and the High-z Supernova Search both found, and what others have later confirmed, is that distant exploding stars are dimmer, and so farther away, than their redshift implies they should be if the universe has been expanding at a steady clip throughout. The expansion must therefore have sped up recently.

The two groups originally based this conclusion on data from a mere 50-odd supernovae. The number has since grown tenfold, but it still leaves plenty of wriggle room for the cosmological constant to prove, well, not so constant after all. Joshua Frieman, who heads DES, hopes his team will eventually analyse over 4,000 exploding stars, some as far away as 7 billion light years. They exploded when the universe was half its current age and, researchers now reckon, still dominated by the gravity of the matter it contained, which was putting the brakes on expansion. Dark energy, it is thought, revved things up some 5 billion years ago. A better estimate of the time at which one gave way to the other helps determine w.

Music of the spheres
In addition to supernova searches, which will train the telescope at ten patches of the sky where Dr Frieman and his colleagues hope to spot and track the explosions, DES will be scouring one-eighth of the night sky for other clues, using three other methods. These all rely on throwing cartloads of computing power at seemingly random data in order to tease out tiny statistical anomalies.

One method looks for the effects of sound waves which originated in the Big Bang: baryon-acoustic oscillations (BAO). In the Big Bang's primordial soup of particles, known as a baryon-photon fluid, there were density waves like the sound waves in air, though far vaster. When the fluid cooled down enough, though, the baryons (particles from which atomic nuclei are made) and photons parted company. The photons became what is now the CMB; it is the fact that they have had nothing to do with matter since the Big Bang that makes the CMB such a remarkable window into the early universe.

With the photons no longer willing to play, there could be no more baryon-photon fluid. The baryons were stuck in position. Where the oscillations in the fluid had bunched the baryons tightly, they remained bunched; where they had been rarefied they remained sparse. The higher density regions became the seeds of galaxies-and the average separation of those galaxies thus reveals the wavelength of the oscillations in the primordial fluid. That characteristic scale has been stretched out to around 450m light years; measuring it at earlier times is another way to show how quickly the universe has been expanding.

The last two of DES's techniques measure not just rates of expansion, as supernovae and BAO searches do, but also the growth of cosmic structures like clusters of galaxies. Tracking the size and shape of clusters through time gives an idea of the tug-of-war between gravity, pulling them together, and dark energy, pushing them apart. This could help answer the question whether expansion is down to dark energy alone, in which case physicists expect a correlation between results from all four techniques, or to modified gravity, if the last two do not square with the first two.

One way to probe structure is to count the number of clusters of a given mass in a given volume of space at different redshifts. This is harder than it sounds because 85% of the mass is invisible dark matter. But it can be measured indirectly, for instance by looking at how hot clouds of gas get as they are pulled towards the cluster's dark-matter core by its gravity.

Alternatively, the distribution of matter, both dark and humdrum, can be gleaned from the effect it has on light. Relativity requires the path of light to be bent by massive objects. The heavier the object, the more an image of something behind it is warped. Most of the time, this warping is tiny-images of galaxies are typically stretched by 2% or so by the clumps of matter they pass on their way to telescopes on Earth. To complicate matters further, few galaxies are perfectly round to start with, so it is hard to tell whether stretching has taken place by looking at any particular galaxy. Fortunately, light from all the galaxies in a given region of the sky passes by the same clumps of matter on the way to Earth. So galaxies as seen from Earth ought all to be distorted in a preferred direction. Observe enough of them, 300m in DES's case, and a pattern should emerge, allowing astronomers to model the structures responsible for the bending.

Combine all four techniques and a clearer picture of the causes of cosmic acceleration will emerge. That, at least, is the hope. Ofer Lahav from University College, London, who is in charge of DES’s science programme, says the odds are that DES will home in on w being equal to -1—some sort of a cosmological constant.

Saving the best 'til LSST
Other, even more ambitious projects, will strive to increase the precision of the measurement of W. Last year ground was broken on the Large Synoptic Survey Telescope (LSST), a much bigger instrument which will be perched atop Cerro Pachón, 10km (6 miles) from Cerro Tololo. Though its $620m budget awaits final approval from America's National Science Foundation and Department of Energy, scientists hope to have it up and running by 2021. The LSST's mammoth camera will boast 3.2 gigapixels.

Then there are two space telescopes, each with a price tag of $1 billion or so. The European Space Agency plans to launch Euclid in 2019 and NASA hopes to put WFIRST in orbit three years later.

These projects are not solely dedicated to probing the nature of dark energy. LSST, for example, will discover asteroids by the bushel-including some that might be hazardous to Earth. But one way or another it is cosmic expansion that they, and all sorts of other astronomical ventures, will be addressing.

The rub is that no amount of observations can ever pin down the figure for w with perfect accuracy. That would require infinite precision, something impossible to achieve even in an ever-expanding universe. And the whole constant idea falls to pieces if w is even a smidgen off -1.

More than any other scientific problem the cosmic-expansion conundrum presents scientists with an existential quandary. "It could be a 22nd-century problem we stumbled upon in the 20th century," says Dr Turner. Some researchers may begin to feel time would be better spent on other scientific pursuits.

Many astronomers, including Dr Perlmutter, are quietly hoping that as DES and the host of other acronyms come online, they will spring another surprise, like the one that first propelled cosmic acceleration into the limelight in 1998. Whether they do or not, though, dark energy-or whatever else is causing the universe to speed up-is probably too big a conundrum for one generation to crack. It will cause boffins to rack their brains for years to come.

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Related Links:
KICP Members: Joshua A. Frieman; Michael S. Turner
Scientific projects: Dark Energy Survey (DES)

The University of Chicago News Office

Michael Turner, Director of the Kavli Institue of Cosmological Physics, speaks about theories, scientists and the universe.

Video

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Related Links:
KICP Members: Michael S. Turner

by Steve Koppes, The University of Chicago News Office

Main feature by Steve Koppes
Main photo courtesy of NASA, ESA, M.J. Jee and H. Ford (Johns Hopkins University)

Sometimes a scientist can only laugh in the face of a seemingly insurmountable challenge.

Such is the case with cracking the mystery of dark energy and its repulsive gravity, which is causing the expansion of the universe to accelerate.

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"The time is ripe to solve the dark matter problem. Our Physics Frontiers Center hopes to shed critical light on dark matter."
- Prof. Rocky Kolb

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"People don't even get the term 'repulsive gravity' because the defining feature of gravity is that it's attractive," says Michael Turner, director of the Kavli Institute for Cosmological Physics. "What do you mean, repulsive gravity? Do you mean the theory is repulsive?" he jokes.

Turner calls dark energy "the most profound mystery in all of science." Cracking the problem requires collaborations of original thinkers working beyond the limits of current theories. That's why dark energy is one of three cosmological puzzles that the Kavli Institute will tackle over the next five years with $17 million in new funding from the National Science Foundation as a Physics Frontiers Center.

Also high on the institute's research agenda are the riddles of dark matter and cosmic inflation. Along with dark energy, these are the three pillars of modern cosmological theory, "and none of them can be explained with physics that we know," Turner says. "They're all pointing to new physics."

Transforming cosmology
During its first decade as a Physics Frontier Center, the Kavli Institute helped to establish the current cosmological paradigm. Originally called the Center for Cosmological Physics, the Institute was founded in 2001 with a $15 million NSF grant. The Institute is launching its second decade with 21 key collaborators around the country and 15 institutional partners, including Argonne National Laboratory and Fermi National Accelerator Laboratory.

The NSF created the Physics Frontiers Centers program to make significant advances at some of the most important intellectual frontiers in diverse physics subfields, says Joseph Dehmer, director of NSF's division of physics.

"By all measures, this has happened, and the 10 PFCs now operating reflect the extremely high standards of scholarship and synergy hoped for," Dehmer says. "An unexpected and most welcome benefit is that the PFCs act as talent magnets, drawing high levels of talent into physics. Another not unexpected benefit is that the triennial PFC competition constitutes a serious, high-level discussion across the subfields of physics - a rare 'unity of physics' event in an increasingly specialized field."

Argonne is a new partner in the UChicago PFC. Argonne and Kavli Institute scientists will develop large-scale cosmological simulations on the laboratory's supercomputers, as well as sensitive new detectors for the South Pole Telescope, which studies the cosmic microwave background radiation leftover from the birth of the universe. Kavli Institute scientists will investigate the dark energy question with the SPT and the Dark Energy Survey. The latter project, led by Fermilab, will collect data on approximately 300 million galaxies spanning two-thirds the history of the universe in order to measure dark energy with new precision.

New form of matter?
The mystery of dark matter may be easier to solve. Kavli Institute scientists hope to accomplish this feat within the next decade. They suspect that dark matter is made of a new form of matter, something that does not consist of quarks, neutrons or protons.

Dark matter may reveal itself through any or all of three means: direct detection via ground-based detectors at the Chicagoland Observatory for Underground Particle Physics (COUPP), indirect detection in the galaxy halo via satellites, and production of the particles at the Large Hadron Collider at CERN, the European particle physics laboratory.

"Right now, there is confusion - claims of possible detections, counter-claims, and spirited debate - and the time is ripe to solve the dark matter problem. Our PFC hopes to shed critical light on dark matter," says Rocky Kolb, the University's Arthur Holly Compton Distinguished Service Professor in Astronomy & Astrophysics, who leads the PFC's dark matter effort.

Cosmic inflation is a different kind of problem. It has emerged as the most important cosmological concept since the Big Bang theory, but many of its claims have not yet been thoroughly tested. Inflation proposes that the universe expanded extremely rapidly in a tiny fraction of a second after the Big Bang. Such a swift expansion would explain some important questions that Big Bang theory alone has been unable to answer.

"We have some circumstantial evidence that inflation took place, but we'd like to make the case very strongly," says John Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy & Astrophysics. A more direct indication of inflation would be to look for a minute sign of polarization in the cosmic microwave background, the afterglow of the Big Bang.

For the last decade, center scientists, including Carlstrom and the late Bruce Winstein, have been developing a technology capable of measuring this polarization. Now they need to deploy that technology to see what they can find.

The successful Kavli Institute proposal for the Physics Frontiers Center was more than two years in the making and included significant support from the University administration and behind-the-scenes personnel.

Winstein, the Samuel K. Allison Distinguished Service Professor in Physics and founder of the original PFC, also played a big role in developing the proposal for renewed funding. Winstein, who lost a four-year battle with cancer last February, worked on the proposal until his last days, Turner says.

"During the last months of his life, he was parceling out his time only to the most important things, and we got a lot of his time. Our PFC is part of Bruce's legacy."

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Related Links:
KICP Members: John E. Carlstrom; Edward W. Kolb; Michael S. Turner; Bruce D. Winstein
Scientific projects: Chicagoland Observatory for Underground Particle Physics (COUPP); Dark Energy Survey (DES); South Pole Telescope (SPT)

Project Exploration Blog

The importance of scientist trainings and workshops for Project Exploration's work: At the heart of Project Exploration's youth programming is bringing together scientists and young people to work together and engage in authentic science. As we grow our programs and opportunities for youth, we are also diversifying and expanding the cadre of wonderful scientists with whom we work. Project Exploration's commitment to increasing access and equity in science means that we also work with scientists to discuss what effective outreach looks like, how to communicate science to youth, share methods of building personal relationships with young people, and how to design youth-centered activities where students and scientists are engaged in the nature of science.

What's "out there?" How do we count the stars? What is space made of? What role does the moon play in our everyday lives? Why does the sun look like it's moving, when it's not?

These are some of the great questions that a group of professors, graduate students, and post-doc fellows of University of Chicago's Kavli Institute for Cosmological Physics (KICP) came up with during a scientist training on effective outreach.

KICP is one of the foremost national research institutes dedicated to interdisciplinary cosmological physics. The scientists at KICP are studying amazing questions about the universe: What is dark energy? What happened during the first moments of the universe's birth? What clues do high energy particles offer about the universe and its evolution? All of this amazing research happens on Chicago's southside, which is also home to many of the under-resourced schools with whom Project Exploration works. By working with scientists at KICP, Project Exploration youth will have an opportunity to discover, explore, and pursue the fields of astronomy, cosmology, and physics alongside professional scientists in their community.

Randy Landsberg, KICP's Director of Education and Outreach, and Project Exploration have been looking for fruitful ways to work together for some time. With Project Exploration's strategic plan calling for us to double the number of students served and diversify our offerings, astronomy and physics seemed like a perfect way to bring scientists and Project Exploration together.

The training was a great opportunity for KICP scientists to learn about Project Exploration and it's youth-centered programming. After discussing effective instructional strategies, the scientists were ready to start developing their "big ideas" about the work they do. With Brothers4Science starting next week, the male scientists were excited about developing activities and sharing their passion for asking questions about the universe with young boys in the community. Many of the female scientists are developing sessions for Sisters4Science. For example, post-doctoral appointee and KICP Fellow Elise Jennings will be working with Sisters4Science in March on understanding the phases of the moon!

Christopher Greer, a graduate student at KICP who has worked with Project Exploration in the past, said that one of the most interesting questions he once heard was "What is the most wonderous thing you have seen in nature?" These are the types of questions that spark the mind and invite inquiry. We look forward to learning about the wonderous universe together with youth and KICP scientists!

Thank you to Randy Landsberg and Professor Daniel Holz for bringing the training to KICP. A big thank you to the participants of the workshop - we can't wait for your exciting sessions with youth!

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Related Links:
KICP Members: Scott Dodelson; Daniel E. Holz; Elise Jennings; Yuko Kakazu; Claudio Ugalde
KICP Students: Immanuel Buder; Ke Fang; Christopher Greer; Christopher M. Kelso; Jing Zhou

Kavli Foundation

Institute for the Physics and Mathematics of the Universe Receives Major Endowment from The Kavli Foundation, Joining Family of Kavli Institutes

(Originally published by the University of Tokyo)

February 7, 2012

(TOKYO, JAPAN) The University of Tokyo (Todai) announced today the establishment of an endowment by The Kavli Foundation for the Institute for the Physics and Mathematics of the Universe (IPMU).

The Institute, which will now be known as the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), probes the biggest mysteries in modern cosmology: How did the universe begin, and how will it end? What is it made of, and what laws govern its behavior? How did we come to exist? The Institute is seeking answers through collaborative research conducted by a wide range of scientists, including mathematicians, theoretical physicists, experimental physicists and astronomers. Together, they focus on topics such as dark matter and dark energy, which make up nearly 96 percent of the universe but today are completely unknown, and the possibility of a single unified theory that can explain the cosmos at the smallest and largest scales.

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Read a roundtable discussion with the Director and Deputy Directors of the Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, about research at the Institute and plans for the future. Click here.

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"It is a great honor for the University of Tokyo that the world-renowned Kavli Foundation has chosen the Institute for the Mathematics and Physics of the Universe as the recipient of a major donation, and to become the newest member of the Kavli group of research institutes as the Kavli IPMU," said University of Tokyo President Junichi Hamada. "Mr. Kavli's generous donation ensures a secure foundation for the Kavli IPMU today and guarantees that the institute will remain at the forefront of its field tomorrow. In addition, this donation has provided the occasion to reexamine and reform our systems for managing donated funds. Seizing this opportunity, I hope to build on this momentum and redouble our efforts to pursue reform at the University of Tokyo."

Said Daisuke Yoshida, Director-General, Research Promotion Bureau, Ministry of Education, Culture, Sports, Science and Technology (MEXT), "IPMU was established in 2007 and has been supported by the World Premier International Research Center Initiative (WPI) of the Japanese government. The WPI program is designed to promote world-class science in Japan and its international visibility. Within just four years, IPMU has established itself as a world-renowned institute starting from zero. I also congratulate IPMU for receiving wonderful recognition by such an international foundation supporting basic science as The Kavli Foundation. We believe that the prestige associated with the endowment will bring a wider global recognition and help sustain the long-term success of IPMU."

The Kavli IPMU will be the first of the university's Todai Institutes of Advanced Study (TODIAS), an initiative announced last year by President Hamada. The goal of TODIAS is to pursue excellence in academics and research, boost academic diversity, promote world-class science, and strengthen the university's international ties.

"The establishment of the Kavli Institute for the Physics and Mathematics of the Universe is a wonderful development," said Sadanori Okamura, TODIAS director. "Kavli IPMU is presently the only institute under TODIAS, and this generous gift from The Kavli Foundation is a testimony that the Foundation appreciates the high quality of scientists at the Institute, assembled by Director Murayama. As the Kavli IPMU was established by the WPI, which currently limits funding to no more than 10 years, we are extremely grateful this endowment will provide income in perpetuity. This is an important step toward providing the institute a long-term financial base. I also sincerely hope that Kavli's generous gift has many positive effects on the University's efforts to ask for further contributions to the University Fund from the society at large."

The Kavli Foundation, based in Southern California, sponsors research in astrophysics, nanoscience, neuroscience and theoretical physics at institutes across the globe, including China, England, Netherlands, Norway and the United States. Kavli IPMU is The Kavli Foundation's 16th institute, its sixth in astrophysics and third in theoretical physics, and the first to be established in Japan.

"I am very glad to welcome the Kavli IPMU to our community of institutes," said Fred Kavli, Founder and Chairman of The Kavli Foundation. "By bringing together disciplines ranging from mathematics to theoretical and experimental physics, the Institute is certain to inspire creative collaborations that will lead to exciting discoveries about the universe. I also hope that our support of science in Japan can demonstrate that the quest for knowledge has no boundaries, and that finding the answers to some of science's biggest and most fundamental questions itself requires international collaboration."

The Kavli IPMU is comprised of about 200 researchers from 15 fields, with almost half coming from outside Japan. Reflecting its dedication to multi-disciplinary collaboration, the Institute is embodied in a five-story research building at the Kashiwa campus, outside of Tokyo in Chiba prefecture, where researchers from different fields typically alternate offices, and the hallways gradually ramp from floor-to-floor to encourage informal connections.

"We are very excited by the vision for this institute," said Robert W. Conn, President of The Kavli Foundation. "The Kavli IPMU is dedicated to attracting an international body of excellent researchers from many fields to focus on topics of science that are of profound interest to all humankind. This Institute's program also fits with our focus on supporting four areas of science: Astrophysics, Nanoscience, Neuroscience and Theoretical Physics. The Kavli IPMU spans two of these four areas - Astrophysics and Theoretical Physics - and demonstrates that the pursuit of scientific knowledge very often requires collaborative efforts across many disciplines. We have been extraordinarily impressed by the leadership of Todai and IPMU, and wish everyone at the University the very best as they pursue some of the most fundamental scientific questions of our day."

The Kavli IPMU director is Professor Hitoshi Murayama, a particle physicist from the University of California, Berkeley who, like the Institute he leads, works on a wide range of subjects. These include developing strategies for new particle collider experiments, dark matter theory, the genesis of ordinary matter in the universe, the theory of inflation, which postulates the rapid expansion of the universe in the first moments of the Big Bang, and models of physics beyond the standard explanation for the nature of the universe.

Deputy directors include Professor Hiroaki Aihara, a particle physicist who is working on a new survey of distant galaxies to learn about the nature of dark energy, and Professor Yoichiro Suzuki, who is deeply involved in an underground experiment to detect dark matter.

"I'm super-excited about the IPMU becoming a Kavli Institute," Murayama said. "It brings an international visibility to the Institute that will help us recruit the best minds from around the world. Meanwhile, the connection to the other Kavli institutes will boost our collaborative research opportunities."

IPMU was established in the fall of 2007 as part of the World Premier International Research Center Initiative, a program of the Japanese government to promote interdisciplinary science in Japan, its international visibility, and globalization of the Japanese universities. Proposed as part of the University of Tokyo, the IPMU was one of six research proposals around the country that won sponsorship from the Ministry of Education, Culture, Sports, Science and Technology. Other WPI institutes are involved in materials research, cell biology, immunology, nanotechnology, and alternative energy development. IPMU receives funding support from the government and the university, but the Institute must eventually identify other sources of support to become a permanent research center.

"The endowment income will help sustain the research program at the Kavli IPMU beyond the current initiative by the Japanese government," Murayama said. "Now we can press on to attack the most basic and biggest mysteries of the Universe!"

The Kavli IPMU's research spans physics and cosmology from subatomic neutrinos and other fundamental particles to the cosmic web of galaxies that formed from the seeds of density perturbations in the Cosmic Microwave Background - the afterglow energy from the Big Bang that emerged less than 400,000 years after that event nearly 14 billion years ago.

Mathematicians at the Institute are working on, for example, new geometric tools to help string theorists, who propose that the smallest constituents of all matter are vibrating strings of energy, describe their ideas.

Particle physicists, such as Kavli IPMU Deputy Director Aihara, are working with astrophysicists at the Subaru Telescope atop Mauna Kea on the Big Island of Hawaii to study the nature of dark energy, the mysterious force that makes up more than 70 percent of the universe and is causing it to accelerate at an ever increasing rate. Meanwhile, researchers such as Kavli IPMU Deputy Director Suzuki are working on ambitious projects such as XMASS, a stunningly sensitive detector deep underground being designed to detect dark matter, which makes up nearly a quarter of the universe and permeates the cosmos like a scaffold upon which galaxies congregate.

Other researchers at the IPMU have published recent papers on the distribution of dark matter in the universe, vigorous star formation in one of the most distant and oldest galaxies yet seen, the growth of supermassive black holes, and other topics.

Astrophysicist Roger Blandford, director of the Kavli Institute for Particle Astrophysics and Cosmology and Professor at Stanford University in California, said IPMU has accomplished much since it was established less than five years ago. "I am thrilled that IPMU will become the Kavli IPMU," Blandford said. "It has already become an outstanding cosmological research center, and this will allow it to contribute even more to this exciting field. My colleagues and I at the Kavli Institute for Particle Astrophysics and Cosmology look forward to many future collaborations and send our congratulations."

About the University of Tokyo
The University of Tokyo, also known as "Todai," was established in 1877 as the first national university in Japan. As a leading research university, Todai offers courses in essentially all academic disciplines at both undergraduate and graduate levels and conducts research across the full spectrum of academic activity. The university aims to provide its students with a rich and varied academic environment that ensures opportunities for both intellectual development and the acquisition of professional knowledge and skills. The University of Tokyo enrolls 28,000 students, evenly divided between undergraduates and graduates. More than ten percent of all students were from overseas in 2011, and more than 3,300 researchers visited the campus in 2010 for short and extended stays. More than 9,000 of the university's researchers visited partner institutions around the world.

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by Tammy Plotner, Universe Today

Less than a year ago, the Hubble Space Telescope's Wide Field Camera 3 captured an amazing image - a giant lensed galaxy arc. Gravitational lensing produces a natural "zoom" to observations and this is a look at one of the brightest distant galaxies so far known. Located some 10 billion light years away, the galaxy has been magnified as a nearly 90-degree arc of light against the galaxy cluster RCS2 032727-132623 - which is only half the distance. In this unusual case, the background galaxy is over three times brighter than typically lensed galaxies... and a unique look back in time as to what a powerful star-forming galaxy looked like when the Universe was only about one third its present age.

A team of astronomers led by Jane Rigby of NASA's Goddard Space Flight Center in Greenbelt, Maryland are the parties responsible for this incredible look back into time. It is one of the most detailed looks at an incredibly distant object to date and their results have been accepted for publication in The Astrophysical Journal, in a paper led by Keren Sharon of the Kavli Institute for Cosmological Physics at the University of Chicago. Professor Michael Gladders and graduate student Eva Wuyts of the University of Chicago were also key team members.

"The presence of the lens helps show how galaxies evolved from 10 billion years ago to today. While nearby galaxies are fully mature and are at the tail end of their star-formation histories, distant galaxies tell us about the universe's formative years. The light from those early events is just now arriving at Earth." says the team. "Very distant galaxies are not only faint but also appear small on the sky. Astronomers would like to see how star formation progressed deep within these galaxies. Such details would be beyond the reach of Hubble's vision were it not for the magnification made possible by gravity in the intervening lens region."

But the Hubble isn't the only eye on the sky examining this phenomenon. A little over 10 years ago a team of astronomers using the Very Large Telescope in Chile also measured and examined the arc and reported the distant galaxy seems to be more than three times brighter than those previously discovered. However, there's more to the picture than meets the eye. Original images show the magnified galaxy as hugely distorted and it shows itself more than once in the foreground lensing cluster. The challenge was to create a image that was "true to life" and thanks to Hubble's resolution capabilities, the team was able to remove the distortions from the equation. In this image they found several incredibly bright star-forming regions and through the use of spectroscopy, they hope to better understand them.

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Related Links:
KICP Members: Michael D. Gladders; Keren Sharon
KICP Students: Eva Wuyts

by Ray Villard and Jane Rigby, Hubble News Release

Thanks to the presence of a natural "zoom lens" in space, NASA's Hubble Space Telescope got a uniquely close-up look at the brightest "magnified" galaxy yet discovered.

This observation provides a unique opportunity to study the physical properties of a galaxy vigorously forming stars when the universe was only one-third its present age.

A so-called gravitational lens is produced when space is warped by a massive foreground object, whether it is the Sun, a black hole, or an entire cluster of galaxies. The light from more-distant background objects is distorted, brightened, and magnified as it passes through this gravitationally disturbed region.

A team of astronomers led by Jane Rigby of NASA's Goddard Space Flight Center in Greenbelt, Md., aimed Hubble at one of the most striking examples of gravitational lensing, a nearly 90-degree arc of light in the galaxy cluster RCS2 032727-132623. Hubble's view of the distant background galaxy is significantly more detailed than could ever be achieved without the help of the gravitational lens.

The results have been accepted for publication in The Astrophysical Journal, in a paper led by Keren Sharon of the Kavli Institute for Cosmological Physics at the University of Chicago. Professor Michael Gladders and graduate student Eva Wuyts of the University of Chicago were also key team members.

The presence of the lens helps show how galaxies evolved from 10 billion years ago to today. While nearby galaxies are fully mature and are at the tail end of their star-formation histories, distant galaxies tell us about the universe's formative years. The light from those early events is just now arriving at Earth. Very distant galaxies are not only faint but also appear small on the sky. Astronomers would like to see how star formation progressed deep within these galaxies. Such details would be beyond the reach of Hubble's vision were it not for the magnification made possible by gravity in the intervening lens region.

In 2006 a team of astronomers using the Very Large Telescope in Chile measured the arc's distance and calculated that the galaxy appears more than three times brighter than previously discovered lensed galaxies. In 2011 astronomers used Hubble to image and analyze the lensed galaxy with the observatory's Wide Field Camera 3.

The distorted image of the galaxy is repeated several times in the foreground lensing cluster, as is typical of gravitational lenses. The challenge for astronomers was to reconstruct what the galaxy really looked like, were it not distorted by the cluster's funhouse-mirror effect.

Hubble's sharp vision allowed astronomers to remove the distortions and reconstruct the galaxy image as it would normally look. The reconstruction revealed regions of star formation glowing like bright Christmas tree bulbs. These are much brighter than any star-formation region in our Milky Way galaxy.

Through spectroscopy, the spreading out of light into its constituent colors, the team plans to analyze these star-forming regions from the inside out to better understand why they are forming so many stars.

Link to published paper:
Keren Sharon, Michael D. Gladders, Jane R. Rigby, Eva Wuyts, Benjamin P. Koester, Matthew B. Bayliss and L. Felipe Barrientos, SOURCE-PLANE RECONSTRUCTION OF THE BRIGHT LENSED GALAXY RCSGA 032727-132609*, The Astrophysical Journal, Volume 746, Number 2

CONTACT
Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4514

Jane Rigby
NASA Goddard Space Flight Center, Greenbelt, Md.
301-286-1507

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Related Links:
KICP Members: Michael D. Gladders; Keren Sharon
KICP Students: Eva Wuyts

by Maggie McKee, New Scientist

Talk about enfants terribles. Baby pulsars may unleash torrents of the highest energy particles known, explaining the provenance of the ultra-high-energy cosmic rays that hit Earth.

Charged particles with energies of at least 10¹⁹ electronvolts slam into our atmosphere from time to time - since 2008, 5000 have been detected by the Auger observatory in Argentina.

Their source has been a mystery. Pulsars - ultradense stars formed during supernova blasts - are one candidate, but it has not been clear if the particles they shed could make it through the dense shroud of stellar shrapnel that surrounds them.

Now Ke Fang and colleagues at the University of Chicago have modelled these particles and found that they can escape within the first year of a pulsar's life.

At that time, the pulsar's spin, which gradually slows, is still fast enough to shoot out high-energy particles, and the supernova debris has spread out enough to allow those particles to escape. "The most energetic particles may come from the smallest stars," says Fang.

'Violent fellows'
If pulsars are the source of ultra-high-energy cosmic rays, it could explain a puzzling finding by Auger. Unlike the majority of low-energy cosmic rays, ultra-high-energy cosmic rays seem to be made up of the nuclei of heavy atoms, such as iron.

Pulsars - whose cores are made of neutrons - are thought to have charged particles such as iron nuclei in their crusts. When the stars spin, their electromagnetic fields accelerate these heavy, charged particles outwards. Because each iron nuclei has 26 protons, each of which feels the pull of the field, the resulting cosmic rays will be of a higher energy than any single protons thrown out by the pulsar.

"We set out to search for energetic cosmic accelerators that have iron, and [pulsars] seem to be an obvious place," says team member Angela Olinto, also at the University of Chicago.

"Pulsars are certainly violent little fellows," agrees Jim Matthews of Louisiana State University in Baton Rouge, a spokesman for the Auger observatory.

Nearby pulsar
The plot could thicken further, however. Auger doesn't detect cosmic rays directly, but the shower of secondary particles created when these rays slam into the atmosphere. So it's possible that the signals being picked up aren't from iron nuclei but single protons interacting with atmospheric particles in a previously unknown way.

We may one day get a chance to test whether pulsars really are the source of ultra-high-energy cosmic rays, says Matthews.

To date, the highest energy cosmic rays measured by Auger seem to be scattered fairly evenly across the sky, suggesting they originated beyond our galaxy and were deflected by cosmic magnetic fields before they hit Auger's detectors. This makes it impossible to trace them back to a source such as a pulsar.

But if a supernova one day explodes in our galaxy, producing a pulsar, it would be close enough that Auger could trace any cosmic rays back to it. "Then it should just be shining iron nuclei on us," says Matthews.

Read more >>

Related Links:
KICP Members: Angela V. Olinto
KICP Students: Ke Fang
Scientific projects: Pierre Auger Observatory (AUGER)

by Greg Borzo, Arete, The University of Chicago

When quantum mechanics was developed, scientists had no idea that this esoteric branch of physics would ever have any practical application. Today society depends upon it.

"Take away quantum mechanics and you wouldn't have computers, the Internet or modern communication systems that make the information age possible," says Michael Turner, director of the Physics Frontier Center at the University of Chicago's Kavli Institute for Cosmological Physics and professor of astronomy and astrophysics, and physics at the University.

This is just one example of the need for pure "discovery" science, which will continue to power the economy and influence all of society, he adds.

There will be a lot more discovery science going on at the University over the coming years thanks to a recent National Science Foundation grant to KICP's Physics Frontier Center of $3.4 million per year for five years, hopefully longer. About half the money will support fellows and graduate students; about half will fund ongoing research projects, conferences, workshops and visitors; and $300,000 a year will seed new initiatives.

The Center will use the money to continue studying three of the most fundamental questions that cosmologists are asking: What comprises dark matter, the mysterious stuff that holds together our solar system and all other structures in the universe? Was there a period of cosmic "inflation," or exponential expansion, in the first moments of the universe? And what is the nature of dark energy, the puzzling energy that permeates space and is causing the expansion of the universe to speed up?

"We're in the 'dark matter decade' and by 2020 should be able to determine whether dark matter is made of WIMPs," Turner says. "Progress on inflation is less certain, and dark energy may be a 'problem for the ages'."

"The main topics that the Center researches are on the frontier of physics, and the team is well balanced between theorists and experimentalists," says Matthew Christian, co-director of Arete and assistant vice president for research program development in the Office of the Vice President for Research and National Laboratories. "We're going to see some very exciting science coming out of the Center in the next several years."

Center reinvents itself
Created in 2001 with an earlier NSF grant, the Center spent the last decade training scientists and building and operating big projects, including the South Pole Telescope in Antarctica, Chicagoland Observatory for Underground Particle Physics, and the Dark Energy Survey.

"The first ten years were devoted to building these projects, and the next five will be all about getting the science out," Turner says. "To do so, we need to engage scientists all around the world, especially those at the Fermi National Accelerator Laboratory and Argonne National Laboratory."

Since the Center has existed for ten years, Turner realized that winning a new NSF grant was going to be extremely challenging. "NSF could have said, 'the University of Chicago has had our support for ten years; let's give someone else a chance,' especially considering that there were 60 pre-proposals in the running and 11 finalists invited to make oral presentations."

Ultimately, the KICP Center was one of only four or five PFC proposals that NSF funded, and Arete was a big part of securing the grant, Turner says. It read the proposals and gave invaluable feedback, helped interpret NSF reviews, and prepared the team for its oral presentation.

"Now that we have the grant, we'll certainly find other ways to take advantage of what Arete has to offer," he adds.

The Center funds a director of education and outreach, Randall Landsberg, because a big requirement of its grants is education and outreach. Turner finds this work the easiest and the most fun since the Center wrestles with questions that the public is extremely interested in: Where do we come from? Where are we going? Are we alone?

"We like to discuss such issues with students because it gets them interested in pursuing careers in science, technology, engineering and mathematics," he says. "We're the Pied Pipers for STEM careers."

Read more >>

Related Links:
KICP Members: Randall H. Landsberg; Michael S. Turner

by Steve Koppes, The University of Chicago News Office

Roald Amundsen reached the South Pole on Dec. 14, 1911. The following year, Arctic explorer Admiral Robert Peary wondered about the scientific merits of making a continuous year of astronomical observations from the South Pole. So Peary sent a letter to Edwin Frost, director of the University of Chicago's Yerkes Observatory, asking about the idea.

Frost rejected the idea, but his UChicago successors thought differently. In 1986 they established the first in a series of telescopes at the South Pole to take advantage of its high elevation (9,301 feet), its clear, dry atmosphere, and its uninterrupted view of the same patch of sky. UChicago scientists have since become a scientific fixture of the South Pole, which now enters its second century of human activity.

UChicago deployed its first telescopes as part of the Cosmic Background Radiation Anisotropy Experiment (COBRA). The largest COBRA telescope, called Python, recorded measurements of the cosmic microwave background - the big bang's afterglow - that were 10 to 100 times better than any other Earthbound site conducting such studies.

Then came Chicago's South Pole Infrared Explorer (SPIREX), the only telescope in the world that had a continuous view of the crash of Comet Shoemaker-Levy 9 with Jupiter in July 1995.

The Degree Angular Scale Interferometer (DASI), which began operating in 2000, soon recorded slight temperature fluctuations in the cosmic microwave background. DASI's precise measurements enabled cosmologists to verify the theory that ordinary matter, of which humans, stars and galaxies are made, accounts for less than 5 percent of the universe's total mass and energy.

DASI also made the first detection of the much fainter polarization in the cosmic microwave background, which made the cover of the Dec. 19, 2002 issue of Nature.

Succeeding DASI was the South Pole Telescope, which collected its first data in February 2007. SPT studies the mysterious phenomenon of dark energy, which makes the expansion of the universe accelerate.

The South Pole Telescope also will be featured as a Science Bulletin next summer in a high-definition, seven-minute documentary at the American Museum of Natural History in New York City.

Read more >>

Related Links:
KICP Members: John E. Carlstrom
Scientific projects: Degree Angular Scale Interferometer (DASI); South Pole Telescope (SPT)

by Steve Koppes, The University of Chicago News Office

A newly released study from the Energy Policy Institute at the University of Chicago (EPIC) concludes that small modular reactors may hold the key to the future of U.S. nuclear power generation.

"Clearly, a robust commercial SMR industry is highly advantageous to many sectors in the United States," concluded the study, led by Robert Rosner, institute director and the William Wrather Distinguished Service Professor in Astronomy & Astrophysics.

"It would be a huge stimulus for high-valued job growth, restore U.S. leadership in nuclear reactor technology and, most importantly, strengthen U.S. leadership in a post-Fukushima world, on matters of nuclear safety, nuclear security, nonproliferation, and nuclear waste management," the report said.

The SMR report was one of two that Rosner rolled out Thursday, Dec. 1, at the Center for Strategic and International Studies in Washington, D.C. Through his work as former chief scientist and former director of Argonne National Laboratory, Rosner became involved in a variety of national policy issues, including nuclear and renewable energy technology development.

The reports assessed the economic feasibility of classical, gigawatt-scale reactors and the possible new generation of modular reactors. The latter would have a generating capacity of 600 megawatts or less, would be factory-built as modular components, and then shipped to their desired location for assembly.

The U.S. Department of Energy funded the reports through Argonne, which is operated by UChicago Argonne LLC. The principal authors of the report were Rosner and Stephen Goldberg, special assistant to Argonne's director.

The reports followed up a 2004 UChicago study on the economic future of nuclear energy. The 2004 study concluded that the nuclear energy industry would need financial incentives from the federal government in order to build new plants that could compete with coal- and gas-fired plants.

The first report, "Analysis of GW-scale Overnight Costs," updates the overnight cost estimates of the 2004 report. Overnight costs are the estimated costs if you were to build a new large reactor 'overnight,' that is, using current input prices and excluding the cost of financing.

It would now cost $4,210 per kilowatt to build a new gigawatt-scale reactor, according to the new report. This cost is approximately $2,210 per kilowatt higher than the 2004 estimate because of commodity price changes and other factors.

Struggling restart
At the Center for Strategic and International Studies event on Dec. 1, CSIS president and CEO John Hamre said that economic issues have hindered the construction of new large-scale reactors in the United States. The key challenge facing the industry is the seven-to-nine-year gap between making a commitment to build a nuclear plant and revenue generation.

Few companies can afford to wait that long to see a return on the $10 billion investment that a large-scale nuclear plant would require. "This is a real problem," Hamre said, but the advent of the small modular reactor "offers the promise of factory construction efficiencies and a much shorter timeline."

Natural gas would be the chief competitor of nuclear power generated by small modular reactors, but predicting the future of the energy market a decade from now is a risky proposition, Rosner said. "We're talking about natural-gas prices not today but 10, 15 years from now when these kinds of reactors could actually hit the market."

The economic viability of small modular reactors will depend partly on how quickly manufacturers can learn to build them efficiently. "The faster you learn, the better off you are in the long term because you get to the point where you actually start making money faster," Rosner noted.

Small modular reactors could be especially appealing for markets that could not easily accommodate gigawatt-scale plants, such as those currently served by aging, 200- to 400-megawatt coal plants, which are likely to be phased out during the next decade, Rosner said. An unknown factor that will affect the future of these plants would be the terms of any new clean-air regulations that might be enacted in the next year.

An important safety aspect of small modular reactors is that they are designed to eliminate the need for human intervention during an emergency. In some of the designs, Rosner explained, "the entire heat load at full power can be carried passively by thermal convection. There's no need for pumps."

Getting the first modular reactors built will probably require the federal government to step in as the first customer. That is a policy issue, though, that awaits further consideration. "It's a case that has to be argued out and thought carefully about," Rosner said. "There's a long distance between what we're doing right now and actually implementing national policy."

The full reports can be downloaded at the Energy Policy Institute website.

Read more >>

Related Links:
KICP Members: Robert Rosner

by Adam Mann, Wired Science

Sometimes it seems like dark matter is intentionally trying to drive physicists mad.

New research using observations from dwarf galaxies has set a lower limit on the mass of dark matter particles. But the results contradict findings from several previous experiments, which observed dark-matter particles with masses below this threshold.

Dark matter is an invisible substance found throughout the universe that doesn't emit any light. Scientists know that if dark matter exists, then so does anti-dark matter, and putting the two together will cause them to annihilate each other and produce gamma radiation.

"We are looking for this byproduct of the annihilation," said physicist Savvas Koushiappas of Brown University in Providence, Rhode Island, who co-authored one of the papers, which will both be published Dec. 1 in Physical Review Letters.

Using NASA's Fermi Gamma-ray Space Telescope, Koushiappas' team and another group from Stockholm University in Sweden looked at data taken from seven dwarf galaxies - Bootes I, Draco, Fornax, Sculptor, Sextans, Ursa Minor, and Segue 1 - which are ideal targets because they are made up of as much as 99 percent dark matter.

After subtracting out the gamma-ray light from other sources, such as pulsars and supernovas, the teams calculated the portion of gamma radiation that should be due to dark matter annihilation. If the dark matter was lighter, there should be a lot more particles and therefore more radiation. But if the mass were larger, the radiation would not be as plentiful.

The researchers estimated from the amount of radiation that a dark matter particle's mass must be greater than 40 GeV, roughly 40 times the mass of a proton. This is strange because at least three prior experiments here on Earth have claimed to detect particles corresponding to dark matter with a mass between 7 and 12 GeV. Another observation, also using the Fermi telescope, had similarly found evidence for dark matter within this lighter mass range.

The explanation for this discrepancy may be relatively straightforward, however. The new research only imposes a constraint on one method that dark matter and anti-dark matter can annihilate, physicist Juan Collar of the University of Chicago, who leads the Coherent Germanium Neutrino Technology (CoGeNT) experiment that may have detected light dark matter, wrote in an email. This process is not the one favored by the researchers who previously used Fermi to see hints of less massive dark matter in the universe, so the existence of lighter dark matter isn't strictly ruled out, he added.

These underlying assumptions of the different experiments may be the reason for the disagreement, agreed Koushiappas. His team was looking for the most basic dark matter particles, but it is possible that dark matter is more complex than simple models predict.

"This is just a step in the puzzle," said Koushiappas.

Read more >>

Related Links:
KICP Members: Juan I. Collar
Scientific projects: Coherent Germanium Neutrino Technology (CoGeNT)

by Steve Koppes, The University of Chicago News Office

Allen Sanderson invited his audience in the banquet room at Grady's Grille in Homewood one evening last September to treat his presentation as a seminar in economics at the University of Chicago. He welcomed interruptions and even rudeness, but drew the line at throwing bottles across the room.

Sanderson, a senior lecturer in economics, was speaker of the month at the Homewood-Flossmoor Science Pub, a new forum for freewheeling exchange between interested members of the public and researchers of all stripes. The topic on the menu for the evening was "Sports, Statistics, and Economics."

Homewood resident Peter Doran, professor in earth and environmental sciences at the University of Illinois at Chicago, founded the H-F Science Pub after reading an article last January in USA Today.

"It was about a fad sweeping the nation called Science Pubs," he says. "I thought this was a great idea and started looking around for one of the local bars to hold it."

Such meet-ups create a valuable space for people who love science and research to come together as fans, rather than as students or professional colleagues. Organizers say the popular discussions have revealed a broad public appetite for informal events that are both intellectual and fun.

The venue alternates between Grady's Grille in Homewood and the Flossmoor Station Restaurant and Brewery, and routinely draws a capacity crowd of 40 or more. "Homewood-Flossmoor is a natural environment for this, with all the scientists who live in the area from the University of Chicago and the museum campus," Doran notes.

Science events grow in popularity

Doran gave the first talk, on "Human and Robotic science in the McMurdo Dry Valleys of East Antarctica." UChicago is contributing a continual stream of speakers, which began in May with Michael Coates, professor in organismal biology & anatomy at UChicago. Coates passed around a specially preserved dead fish during his humor-laced talk, playfully titled "The Incompleat Angler, or Fishing for Creatures from the Black Lagoon."

Following suit the next month, without the dead fish, was Rocky Kolb, the Arthur Holly Compton Distinguished Service Professor in Astronomy & Astrophysics. Kolb, author of Blind Watchers of the Sky, signed a small stack of his books for one woman after he described "The Dark Side of the Universe" to an appreciative audience.

Still other Science Pub speakers have come from UIC, the American Institute of Steel Construction and Indiana University Northwest.

UChicago alumna Stephanie Levi, PhD'09, began doing science outreach events called Night Lab for the public in 2008 at Schubas Tavern in Chicago's Lakeview neighborhood. A molecular geneticist and cellular biologist, Levi tweets at @scienceissexy and operates a Science is Sexy website. Levi will discuss "Sex and Attraction" Feb. 15 at the Divinity School's Wednesday Community Luncheon program, which offers speakers to the UChicago community in a spirit similar to the Science Pub and Cafe Scientifique. Her previous programs have been featured in the University of Chicago Magazine on coffee science and in a variety of other news outlets.

Public interest in science runs high in the Chicago area, if attendance at these and other events are any indication. Randy Landsberg, outreach director for the Department of Astronomy & Astrophysics and the Kavli Institute for Cosmological Physics, founded a Cafe Scientifique on the North Side in April 2006. The Café draws rave reviews at the Map Room, where it typically meets.

Last Nov. 1, more than 400 people attended Nobel laureate John Mather's UChicago Brinson Lecture. "We were over capacity," says Landsberg, a Brinson Lecture organizer. "Folks were almost literally hanging from the rafters."

On that same night, just a few blocks away at the Harold Washington Public Library, another capacity crowd of more than 400 heard Harvard physics professor Lisa Randall discuss her new book, Knocking on Heaven's Door in an Illinois Science Council event. Talks by visiting scientists in October and April also filled the library's auditorium.

The next H-F Science Pub takes place at 8 p.m. Nov. 29 at Grady's Grille, 18147 Harwood Ave. in Homewood. The speaker will be UChicago's Steven Simon, senior scientist in geophysical sciences, discussing "The Fall, Recovery, and Classification of the Park Forest Meteorite."

The Dec. 20 Science Pub at the Flossmoor Station will feature Kay MacLeod, associate professor in the Ben May Department for Cancer Research at UChicago. Her topic, beginning at 8 p.m., will be "Cancer's Sweet Tooth - How Tumors Acquire and Burn Energy Differently from Normal Tissue."

Read more >>

Related Links:
KICP Members: Edward W. Kolb; Randall H. Landsberg

WBEZ 91.5

Presented The University of Chicago via Chicago Amplified | Nov. 01, 2011

The history of the universe in a nutshell, from the Big Bang to now, and on to the future... John Mather tells the story of how we got here, how the universe began with a Big Bang, how it could have produced an Earth where sentient beings can live, and how those beings are discovering their history.

Mather was project scientist for NASA's Cosmic Background Explorer (COBE) satellite, which measured the spectrum (the color) of the heat radiation from the Big Bang, discovered hot and cold spots in that radiation, and hunted for the first objects that formed after the great explosion. He explains Einstein's biggest mistake, how Edwin Hubble discovered the expansion of the universe, how the COBE mission was built, and how the COBE data support the Big Bang theory. He also shows NASA's plans for the next great telescope in space, the James Webb Space Telescope. It will look even farther back in time than the Hubble Space Telescope, and will peer inside the dusty cocoons where stars and planets are being born today. It is capable of examining Earth-like planets around other stars using the transit technique, and future missions may find signs of life.

John C. Mather is an astrophysicist, cosmologist, and Nobel laureate. He was awarded the 2006 Nobel Prize in Physics for his work on COBE. Mather received his Nobel Prize for the precise determination that the spectrum of the cosmic microwave background radiation is that of a thermal source and the first detection and measurement of the anisotropy. These measurements marked the beginning of the era of precision cosmology. Mather is currently a senior astrophysicist at NASA's Goddard Space Flight Center in Maryland and the Senior Project Scientist for the James Webb Space Telescope, the successor to the Hubble Space Telescope.

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by Steve Koppes, The University of Chicago News Office

Cosmologist John C. Mather will deliver the 2011-2012 University of Chicago Brinson Lecture on "The History of The Universe in a Nutshell: From the Big Bang to Life and the End of Time."

The lecture will begin at 6 p.m. Tuesday, Nov. 1 in the MacLean Ballroom of the School of the Art Institute of Chicago, 112 S. Michigan Ave. Admission is free, and the event is open to the public. Mather’s lecture is co-sponsored by the UChicago and SAIC with support from the Brinson Foundation.

Mather shared the 2006 Nobel Prize in Physics for his work on the Cosmic Background Explorer satellite. COBE’s measurements of the cosmic microwave background radiation marked the first detection of hot and cold spots in the heat radiation from the big bang. Astrophysicists regard these measurements as the beginning of the era of precision cosmology. Mather currently is a senior astrophysicist at NASA's Goddard Space Flight Center in Maryland and the senior project scientist for the James Webb Telescope, the proposed successor to the Hubble Space Telescope.

During his lecture, Mather will explain Albert Einstein’s biggest mistake, how Edwin Hubble discovered the expansion of the universe, how the COBE mission was built and how its data support the big bang theory.

Read more >>

by Steve Koppes, The University of Chicago News Office

Two of the three recipients of the 2011 Nobel Prize in Physics are collaborators on cosmology projects led by the University of Chicago and Fermi National Accelerator Laboratory.

The physics Nobel was awarded on Tuesday, Oct. 4, "for the discovery of the accelerating expansion of the universe through observations of distant supernovae." One half of the prize went to Saul Permutter, a collaborator on the Dark Energy Survey.

The other half of the prize was shared by Adam Riess, a collaborator on the Sloan Digital Sky Survey’s Supernova Survey, and Brian Schmidt, an astronomer at the Australian National University. Riess is a professor of astronomy and physics at Johns Hopkins University and an astronomer at the Space Telescope Science Institute.

"This was expected and well-deserved," said Joshua Frieman, a Fermilab scientist and professor in astronomy & astrophysics at UChicago.

Frieman founded and directs the Dark Energy Survey, a giant digital camera that is scheduled to probe the origin of cosmic acceleration from the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory in Chile.

The SDSS Supernova Survey, which operated from 2005 until 2008, discovered more than 500 type Ia supernovas for cosmological study. Perlmutter is an astrophysicist at the U.S. Department of Energy's Lawrence Berkeley National Laboratory and a professor of physics at the University of California at Berkeley.

Type Ia supernovas are exploding stars that shine with such predictable brightness that they are known as standard candles. This year's Nobel laureates and many other astronomers use them as astronomical measuring devices to help determine the expansion rate of the universe. By comparing a type Ia supernovae at the edge of the known universe to similar ones nearby, scientists can estimate whether the universe will expand forever or eventually collapse back into itself under the force of gravity.

Stephan Meyer, professor in astronomy & astrophysics, collaborated with another Nobel Prize-winning team on the Cosmic Background Explorer, which in 1992 confirmed that the universe was born in a hot big bang.

Read more >>

Related Links:
KICP Members: Joshua A. Frieman; Stephan S. Meyer

by Steve Koppes, The University of Chicago News Office

A $10 million donation from futures trader and University of Chicago alumnus William Eckhardt, SM'70, will enable the Physical Sciences Division to respond rapidly and with flexibility to scholarly opportunities and challenges as they arise.

The donation will add to the division's discretionary funds, which are intended to address priorities as needed, including the recruitment and retention of prominent scholars.

"William Eckhardt has been a champion of scientific research, and an essential supporter of the University's efforts to bring innovative scholars to our campus and help them do their best work," said University President Robert J. Zimmer. "We are very grateful for this important gift."

Eckhardt said that one inspiration for his gift was his understanding that most scientific advances depend on an interplay between theoretical and applied science.

"Theoretical science is one of the glories of scholarship at the University of Chicago, and for me, one of the gratifying aspects of giving to the physical sciences is to be able to support that endeavor. They take theory seriously," he said.

The gift should benefit the division's faculty in many ways in the coming years, said Robert Fefferman, dean of Physical Sciences.

"William Eckhardt has made an historic commitment that will change the future of our division," said Fefferman. "What makes this gift so powerful is the flexibility that I or any dean in Physical Sciences will have in its use. To have a gift of this size directed to discretionary funds is quite rare, and it takes a very special appreciation and understanding of science to do that."

Eckhardt's appreciation for science extends to his hobbies, which include the study of quantum mechanics and the philosophy of time, Fefferman noted. "These are not hobbies that most people have. He has a firm technical grasp of science and mathematics that's rather astounding."

Eckhardt had previously donated $20 million to the division, which prompted the University to name the William Eckhardt Research Center in his honor.

A mixture of theoreticians and experimentalists will make their home in the Eckhardt Center, which will be under construction from late 2011 to late 2014. Moving into the Eckhardt Center will be the Department of Astronomy & Astrophysics, the Kavli Institute for Cosmological Physics, the theoretical physics group of the Enrico Fermi Institute, part of the James Franck Institute and the University’s new Institute for Molecular Engineering.

"We want very much to attract not just excellent faculty members, but faculty members who will change the history of science, and we've done it. We've had historic-level scientists and mathematicians come here, and this latest gift will allow us to continue that effort," Fefferman said.

These scientists and mathematicians include a long list of Nobel laureates in physics and chemistry and of Fields medalists, recipients of the highest honor in mathematics. Two recent examples are Yoichiro Nambu and Ngo Bao Chau. Nambu, the Harry Pratt Judson Distinguished Professor Emeritus in Physics, shared the 2008 Nobel Prize in physics, while Ngo, the Francis and Rose Yuen Distinguished Service Professor in Mathematics, accepted an appointment at UChicago just months before receiving the Fields Medal last year.

Eckhardt's gift will help the Physical Sciences Division move quickly to recruit or retain such talent as the situations arise. Many scientists require precision equipment to conduct their research, and start-up funds to equip their laboratories have increased markedly in recent years. The cost of keeping top-performing, established scientists sought after by other institutions is rising as well.

"Here, with Mr. Eckhardt's gift, we have the ability to draw on resources to respond to the situation," Fefferman said.

Read more >>

Kavli Foundation Newsletter, Vol. 4, Issue 3, 2011

In June, it was announced that a dark-matter experiment had detected a seasonal signal variation similar to two other experiments that used different detectors. The new seasonal variation, recorded by the Coherent Germanium Neutrino Technology (CoGeNT) experiment, is exactly what theoreticians had predicted if dark matter turned out to be what physicists call Weakly Interacting Massive Particles (WIMPs).

Juan Collar of the Kavli Institute for Cosmological Physics, University of Chicago, led the team that detected the seasonal signal variation. In an extended interview, he discusses the significance of the finding and what will be needed to prove the existence of dark matter. "[It] gives you pause, the fact that the same kind of dark matter particle could be behind these three different observations from three very different detectors."

Related Links:
KICP Members: Juan I. Collar
Scientific projects: Coherent Germanium Neutrino Technology (CoGeNT)

by Kadesha Thomas, The University of Chicago News Office

Dovetta McKee believes that every child has the potential to achieve academically, including disadvantaged youths, if given the opportunity and support. As the current director of the University's Office of Special Programs-College Prep, McKee is back where she got her career start in youth development.

From 1992 to 1999, McKee worked side by side with the late Larry Hawkins, who founded the office's landmark program Upward Bound. Hawkins, who was a high school star athlete, turned basketball coach, used sports to hook inner-city students into the academic program. McKee, who managed parent involvement activities, remembers how as many as 700 high school students would fill the programs and visit the University campus.

McKee took on the directorship in 2009 after Hawkins' death that year and now oversees his legacy, shepherding minority students from low-income South Side communities into college by providing a bridge to possibilities.

Between her UChicago stints, McKee was an associate professor at Aurora University, where she helped adults working in child development complete undergraduate degrees. She later became director of special initiatives at Prevention First, a program that partnered with Chicago Public Schools to tackle social issues that hinder academic success, such as neighborhood violence, teen pregnancy and substance abuse.

McKee brings her past experience to tackle some of those same issues and usher her students into college. "A lot of people do not believe that young African Americans can excel academically, and as a result they have very low standards for them," said McKee, who earned a law degree from John Marshall Law School. "People believe the hype; they believe what they see in the media, and the emphasis is always on the negative."

Despite relatively low graduation rates among urban high school students, youths who participate in the OSP-CP programs maintain a 100 percent high school graduation rate, up from 94 percent in 1997. Since 2007, between 85 and 100 percent have enrolled in four-year universities. Before then, the college enrollment rate was nearly 80 percent.

"When the bar is set high, and I have parents who are committed-even sometimes without committed parents-when I have young people who have been encouraged to believe in themselves, they do achieve," McKee said.

The OSP-CP operates throughout the school year, offering Saturday classes and campus tours at colleges and universities. Summer activities focus on math, science, foreign-language study and entrance exam preparation. The OSP-CP partners with the University's Kavli Institute for Cosmological Physics to expose students to scientific research and the University Theater to engage students in the arts. McKee's team also helps students develop soft skills like public speaking and punctuality.

The program's location on the University of Chicago campus reinforces its ability to give students an excellent pre-collegiate experience. "With any new adventure, you're always fearful because of the unknown," McKee explained. "It's imperative that young people from underserved communities see that people who work and learn on college campuses are just like everybody else. They need to know it's possible to cross the bridge and not fall in the river."

Read more >>

CBS Chicago

The head of the University of Chicago Astronomy and Astrophysics Department says it's time to look way beyond low-earth orbit for the nation's next space venture.

As WBBM Newsradio 780's John Cody reports, professor Rocky Kolb says the space shuttle helped keep the pioneering Hubble space telescope operating, but private industry can probably take over that job.

Read more >>

Related Links:
KICP Members: Edward W. Kolb

Kavli Foundation

June 6, 2011

At the White House today, President Barack Obama met in the Oval Office with the seven U.S. recipients of the 2010 Kavli Prizes to recognize and honor their seminal contributions to the three fields for which the Prizes are awarded -- astrophysics, nanoscience and neuroscience.

Joined by the President's science advisor, John P. Holdren, President Obama greeted Kavli Prize Laureates Roger Angel (University of Arizona), Jerry E. Nelson (University of California, Santa Cruz), Donald M. Eigler (IBM Almaden Research Center), James E. Rothman (Yale University), Richard H. Scheller (Genentech), Nadrian C. Seeman (New York University), and Thomas C. Sudhof (Stanford University). Accompanying the laureates were Fred Kavli, Founder and Chairman of The Kavli Foundation; Robert W. Conn, President of The Kavli Foundation; and Wegger Chr. Strommen, the Norwegian Ambassador to the United States.

The Kavli Prizes are a partnership between The Kavli Foundation (U.S.), the Norwegian Academy of Science and Letters and the Norwegian Ministry of Education and Research.

"We are extremely grateful to the President for the honor of this visit, and for his strong and heartfelt commitment to scientific research and discovery," said Fred Kavli. "It reflects the nation's deep support for innovative research that scientists across the country rely upon, including the foundational research discoveries of the 2010 Kavli Laureates."

The Kavli Laureates received their awards for research that made it possible to look more deeply and clearly into the universe, to control matter on the nano scale, and to understand how the brain's nerve cells communicate.

The 2010 Kavli Prize in Astrophysics was awarded to Roger Angel, Jerry E. Nelson and Raymond N. Wilson (European Southern Observatory, Germany) for their contributions to the development of giant telescopes. The size of a telescope's primary mirror determines the light-gathering power and ability to detect and resolve the faintest and most distant objects in the universe. Nelson, Wilson and Angel pioneered the development of a new generation of large optical telescopes with innovations such as precise reflecting mirrors and more sophisticated shaping that has led to an extraordinary range of fundamental discoveries about the cosmos.

The 2010 Kavli Prize in Nanoscience was awarded to Donald M. Eigler and Nadrian C. Seeman for their development of unprecedented methods to control matter on the nanoscale. Eigler demonstrated it was possible to pick up and precisely place individual atoms at will, creating a whole field of quantum engineering. Seeman conceived the idea of using DNA as a building material for nanoscale engineering. Inventing DNA nanotechnology, he pioneered the use of DNA as a non-biological programmable material for a countless number of devices that self-assemble, walk, compute and catalyze. These discoveries promise breakthroughs in future applications in fields ranging from electronics to biology.

The 2010 Kavli Prize in Neuroscience was awarded to James E. Rothman, Richard H. Scheller and Thomas C. Sudhof for discovering the molecular basis of neurotransmitter release. Understanding how nerve cells communicate with one another has been a central problem in modern brain science. Over the past thirty years, Scheller, Sudhof and Rothman have used a creative multidisciplinary set of approaches to elucidate the key molecular events of neurotransmitter release. Moreover, their work has demonstrated that neurotransmitter release represents a special case of the fundamental cell biological process of membrane trafficking.

The Kavli Prize consists of a scroll, a gold medal and a cash award of one million dollars in each field, with the prizes awarded biennially. Kavli Prize recipients are chosen by committees comprised of distinguished international scientists recommended by the Chinese Academy of Sciences, the French Academy of Sciences, the Max Planck Society, the U.S. National Academy of Sciences and The Royal Society. After making their selection for Prize recipients, the recommendations are confirmed by the Norwegian Academy of Science and Letters. The formation of Prize Committees and the selection of prize recipients is independent of The Kavli Foundation - a nonprofit U.S.-based foundation dedicated to advancing science for the benefit of humanity, promoting public understanding of scientific research, and supporting scientists and their work.

The 2010 Kavli Prize Laureates were announced last year and received their awards in a ceremony held in Oslo, Norway. The call for nominations for the 2012 Kavli Prizes occurs this fall.

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by Steve Koppes, The University of Chicago News Office

Josh Frieman, director of the international Dark Energy Survey collaboration, will kick off a new lecture series on current astrophysics with a talk on "The Dark Universe" at 7 p.m. Thursday, June 9 at the Adler Planetarium, 1300 S. Lake Shore Drive in Chicago.

Over the last decade, cosmologists have discovered that only 4 percent of the universe is made of ordinary matter - the atoms and molecules that form stars, planets and people. The other 96 percent is dark, existing in a form totally unlike anything scientists have ever encountered.

Dark matter, which makes up approximately a quarter of the universe, holds galaxies together and is the key ingredient in their formation. The remaining three-quarters of the universe is composed of dark energy, a mysterious force that is causing the expansion of the universe to speed up.

Frieman's presentation will introduce "The Dark Universe," review what scientists have learned about it and describe new experiments and observatories that aim to solve the enigmas of dark matter and dark energy. The presentation will include a virtual full-dome tour of the large-scale universe recently revealed by cosmic sky surveys.

Frieman is a professor in astronomy & astrophysics at the University of Chicago and a senior staff scientist at Fermi National Accelerator Laboratory's Center for Particle Astrophysics. He directs the Dark Energy Survey, a collaboration of more than 120 scientists from 20 institutions on three continents. The collaboration is building a 570-megapixel camera for a telescope in Chile to probe the origin of cosmic acceleration.

Admission is $10 general admission, $5 for Adler members and students. For more information, visit http://www.adlerplanetarium.org/calendar/the-dark-universe-lecture.

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Related Links:
KICP Members: Joshua A. Frieman
Scientific projects: Dark Energy Survey (DES)

by Steve Koppes, The University of Chicago News Office

A dark-matter experiment deep in the Soudan mine of Minnesota now has detected a seasonal signal variation similar to one an Italian experiment has been reporting for more than a decade.

The new seasonal variation, recorded by the Coherent Germanium Neutrino Technology (CoGeNT) experiment, is exactly what theoreticians had predicted if dark matter turned out to be what physicists call Weakly Interacting Massive Particles (WIMPs).

"We cannot call this a WIMP signal. It's just what you might expect from it," said Juan Collar, associate professor in physics at the University of Chicago. Collar and John Orrell of Pacific Northwest National Laboratory, who lead the CoGeNT collaboration, are submitting their results in two papers to Physical Review Letters.

WIMPS might have caused the signal variation, but it also might be a random fluctuation, a false reading sparked by the experimental apparatus itself or even some exotic new phenomenon in atomic physics, Collar said.

Dark matter accounts for nearly 90 percent of all matter in the universe, yet its identity remains one of the biggest mysteries of modern science. Although dark matter is invisible to telescopes, astronomers know it is there from the gravitational influence it exerts over galaxies.

Theorists had predicted that dark matter experiments would detect an annual modulation because of the relative motion of the Earth and sun with respect to the plane of the Milky Way galaxy.

The sun moves in the plane of the galaxy on the outskirts of one of its spiral arms at a speed of 220 kilometers per second (136 miles per second). The Earth orbits the sun at 15 kilometers per second (18.5 miles per second). During winter, Earth moves in roughly the opposite direction of the sun's movement through the galaxy, but during summer, their motion becomes nearly aligned in the same direction. This alignment increases Earth's net velocity through a galactic halo of dark matter particles, whose existence scientists have inferred from numerous astronomical observations.

Like a cloud of gnats
WIMPs would be moving in random directions in this halo, at velocities similar to the sun's. "You find yourself in a situation similar to a car moving through a cloud of gnats," Collar explained. "The faster the car goes, the more gnats will hit the front windshield."

CoGeNT seems to have detected an average of one WIMP particle interaction per day throughout its 15 months of operation, with a seasonal variation of approximately 16 percent. Energy measurements are consistent with a WIMP mass of approximately 6 to 10 times the mass of a proton.

These results could be consistent with those of the Italian DArk MAtter (DAMA) experiment, which has detected a seasonal modulation for years. "We are in the very unfortunate situation where you cannot tell if we are barely excluding DAMA or barely in agreement. We have to clarify that," Collar said.

In particle physics, he further cautioned, agreement between two or three experiments doesn’t necessarily mean much. The pentaquark is a case in point. Early this century, approximately 10 experiments found hints of evidence for the pentaquark, a particle consisting of five quarks, when no other known particle had more than three. But as time went on, new experiments were unable to see it.

"It's just incredible," said UChicago physics Professor Jonathan Rosner. "People still speculate on whether it’s real."

Collar and his colleagues have calculated the probability that their finding is a fluke to be five-tenths of a percent, or 2.8 sigma in particle physics parlance.

"It's not an exact science yet, unfortunately," Collar said. "But with the information we have, the usual set of assumptions that we make about the halo and these particles, their behavior in this halo, things seem to be what you would expect."

Other dark-matter experiments, including Xenon100, have not detected the seasonal signal that CoGeNT and DAMA have reported.

"If you really wanted to see an effect, you could argue that the Xenon100 people don't have the sensitivity to Juan's result," said Rosner, who is not a member of the CoGeNT collaboration. "On the other hand, they've done a number of studies of what their sensitivity is at low energies and they believe they’re excluding this result."

Interrupted by fire
CoGeNT operated from December 2009 until interrupted by a fire in the Soudan mine in March 2011. Fifteen months of data collection is a relatively brief period for a dark-matter experiment. In fact, Collar and his colleagues decided to examine the data now only because the fire had stopped the experiment, at least temporarily.

The fire did not directly affect the experiment, but the CoGeNT team has not been able to examine the detector because of clean-up efforts. The detector may no longer work, or if it does work, it may now have different properties.

"This effect that we're seeing is touch-and-go. It's something where you have to keep the detector exquisitely stable," Collar said. If a single key characteristic of the detector has changed, such as its electronic noise, "We may be unable to look for this modulation with it from now on."

The putative mass of the WIMP particles that CoGeNT possibly has detected ranges from six to 10 billion electron volts, or approximately seven times the mass of a proton. "To look for WIMPs 10 times heavier is hard enough. If they're this light, it becomes a nightmare," Collar said.

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Related Links:
KICP Members: Juan I. Collar; Jonathan L. Rosner
Scientific projects: Coherent Germanium Neutrino Technology (CoGeNT)

Kavli Foundation

KICP's Juan Collar leads a team that detected a signal compatible with dark matter theory. In an interview, he discusses the significance of the finding, what will be needed to prove the existence of dark matter, and how turning to an old technology is helping scientists in the 21st Century.

A DARK MATTER DETECTOR about 700 meters below the ground in a Minnesota mine has recorded a seasonal modulation in staggeringly faint electrical pulses - the possible result of dark matter particles called WIMPs that envelope the Milky Way galaxy and collide with atoms in the detector's germanium crystal.

The finding, by the Coherent Germanium Neutrino Technology, or CoGeNT] experiment at the Soudan mine, is described in a paper posted online by a team of researchers led by Juan Collar of the Kavli Institute for Cosmological Physics (KICP) at the University of Chicago.

The results are consistent with the modulation in signals first recorded more than a decade ago by the DArk MAtter/Large sodium Iodide Bulk for RAre processes (DAMA/LIBRA) experiment at Gran Sasso, Italy. It also appears to match recent but as-yet-unpublished findings by another experiment called CRESST, or the Cryogenic Rare Event Search with Superconducting Thermometers, also at Gran Sasso.

Collar said his experiment is carefully designed to detect the collisions between WIMPs (Weakly Interacting Massive Particles, which are hypothesized by dark matter theory) and atoms in the crystal. "It's sensitive to very low energies, and that's where we got stuck," Collar said of CoGeNT's detection of a modulation in signals. "We're seeing something down there that we don't quite understand yet."

Collar and his colleagues, who have submitted the paper "Search for an Annual Modulation in a P-type Point Contact Germanium Dark Matter Detector" for publication, emphasized that the origin of the signals is unknown, but that the data collected from 442 days of observations "are prima facie congruent when the WIMP hypothesis is examined."

Collar discussed his research, and the meaning of his recent findings, in a conversation with The Kavli Foundation.

A CONVERSATION WITH JUAN COLLAR
THE KAVLI FOUNDATION (TKF): Is your tentative result, which suggests a seasonal variation in the number of particle collisions with the nuclei in your detector, evidence for WIMPs – that is, evidence for dark matter?

JUAN COLLAR: You know, evidence is a big word in particle physics. In principle, one might be tempted to speak the language of evidence, but this whole situation with dark matter is so volatile one must be very cautious. We decided to share our data and publish. The impact is rather large, because our observations seem to agree with what DAMA has seen for about 10 years now. They are also similar to preliminary results from CRESST, another dark matter experiment.

So it's an important result. But evidence? We wouldn't touch that word with a ten-foot pole. There is evidence, perhaps, for a modulation in the data. But for the detection of dark matter? That is something that we’ve stated DAMA shouldn't claim, even after 10 years of very solid observation of a modulation. The origin of this modulation does not necessarily have to be dark matter particles.

TKF: What is unique about your detector in the CoGeNT experiment, and what exactly is it detecting?

COLLAR: When a dark matter particle, a WIMP, strikes the nucleus of an atom in a germanium crystal, the nucleus recoils, striking other nearby atoms and knocking off their electrons. Our detector reads this ionization as an electrical signal. What's special about our detector is that it's optimized to look for light-mass dark matter particles, arguably the best for that particular job.

The reason for this is that most other detectors are designed to detect particles about 100 times the mass of a proton. But if WIMPS are much lighter than that, say just a few times the mass of a proton, then you need a detector with very low electronic noise. You have to be able to distinguish the very tiny energy depositions that are triggered by these collisions, because that's what you expect from lighter particles; they don't pack as much of a punch as something heavier.

That's what CoGeNT detectors are designed for, and that's where they perform very well, dramatically so. They are sensitive to very low energies, and that's where we got stuck. We're observing something down there that we don't quite understand yet. We cannot yet tell you what it is, but of course we can list many possibilities. The low energy events that we end up with - we don't see anything anomalous in them. They look like they're produced by some form of radiation.

TKF: You detected a seasonal modulation in your data after 442 days of observations, and then your experiment was halted in March by a fire in the Soudan mine. Was the CoGeNT detector damaged? If it's OK, will you continue to gather more data to strengthen your result?

COLLAR: It's a pure coincidence, but we started at the expected time for the minimum number of expected WIMP collisions. We started early in December of 2009, that is, we departed from the minimum, went through a full cycle, and on the way into the second cycle we ran out of luck. There was this fire in the mine shaft, and that stopped everything.

We were to some extent lucky. The underground laboratory is pretty large, and our side was untouched by either fire or fire-extinguishing fluid. That's what made much of the mess down there; so much foam had to be injected that it actually pushed the doors open to the laboratory and some experiments were completely covered by it. Our experiment was fine; but the detector went through a thermal cycle. Normally, we keep these devices at ninety degrees Kelvin, which is pretty chilly, and when you warm them up like this the quality of the vacuum inside the detector makes a critical difference. If it's a good vacuum, you should be fine when you turn it on again; if it's a bad vacuum, the detector could be useless for the delicate work we are trying to do. This is why we have analyzed the data collected up until the fire. We have 15 months of observations and we don't know if we'll have another day of good data with this device.

If this detector is not dead and the signal rate starts to decrease again toward next December and then picks up again afterward - the chances of seeing something like that start to become very small, very fast. The opposite side of the coin is, of course, if it doesn't do what I just described. In that case, the modulation we have observed so far may have been just a fluke.

TKF: One possibility is that you're seeing a systematic error, that is, false signals that originate from the detector itself. But if CoGeNT, DAMA and CRESST - all different experiments with different kinds of detectors and different methods - are seeing the same seasonal modulation in collisions, isn't it unlikely that the signal is some kind of systematic effect?

COLLAR: Indeed. Yes, you're right. The targets, or the material that the detectors are made of, are different. Also, each of these experiments collects and reads events differently.

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"[It] gives you pause, the fact that the same kind of dark matter particle could be behind these three different observations from three very different detectors."

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In our detector, particles strike the germanium crystal and produce ionization. In DAMA, particles strike sodium iodine, which is a scintillator material that generates light when radiation impinges on it, and that light is read out by a photomultiplier - an electronic eye of sorts - that turns light into electrical pulses. CRESST, meanwhile, is entirely different. CRESST uses a calcium tungstenate crystal, another scintillating material, but it is also operated as another type of detector called a bolometer, in this case, a hybrid bolometer. It's a device where they read out the light that is produced through scintillation, but also the increase in temperature that is produced by the particle interaction.

So you're perfectly right, it's kind of suspicious that what these three experiments observe can be interpreted as a dark matter particle in common, of the same mass and with the same probability of interaction with different detector materials. That gives you pause, the fact that the same kind of dark matter particle could be behind these three different observations from three very different detectors.

TKF: The CRESST experiment appears to be seeing signals compatible with dark matter. What makes them confident that they are seeing something similar to what CoGeNT is seeing?

COLLAR: They've been exquisitely careful about trying to eliminate other possibilities. Over the last year or so, they have implemented different precautions, and have made different tests of their detector – all to exclude the possibility that what they're observing is a number of possible sources of background radiation. They've been discarding those one after another, and they're now left with about 20 events that they just don't know what to make of. They look like nuclear recoils, particularly affecting the oxygen in the crystal, and they cannot be explained away. They see evidence for 20 events that might be compatible with the same particle that might be producing a modulation in DAMA, or might be producing a modulation in our detector.

TKF: So, because the chance is very tiny that this is some background noise, the odds are higher that these collisions are being caused by dark matter particles, is that correct?

COLLAR: Well, that's not entirely true. The first part of the statement is correct. You can grow convinced that the chances are small that this is due to a background or any other non-exotic process that we can dream up. But it takes a leap of faith to go from there to the next step, claiming that what we are detecting is dark matter. That is actually why the community has been very critical of DAMA. They claim that the chances are tremendously small that their fluctuation is due to some kind of fluke. True. But going from there to stating, ergo it must be dark matter – that's a hard call. But the DAMA collaboration seems not to be detoured by such considerations.

TKF: Could this modulation in collisions also be due to some kind of exotic physics that we don’t yet know about?

COLLAR: Well, exactly. It could be. It's one of three things: It's either dark matter, or it is something perfectly boring, systematic and instrumental – it wouldn't be the first time in physics that we fool ourselves into thinking that something mundane is relevant. This sort of situation typically happens when agreement with other experiments is noticed, and soon after you are obsessed with observations that normally you wouldn't pay any attention to.

Or third, it might be something interesting that's not related to dark matter. For instance, we could be noticing new effects arising from solar neutrino interactions in the detectors, as some phenomenologists are proposing. That would be pretty exciting, a new piece of physics not really related to dark matter. We'd still get to learn something about nature. Of course, the first possibility to consider is some instrumental effect that we have not figured out yet.

TKF: DAMA has claimed that they’ve also detected a seasonal modulation in their data, but other projects such as CDMS-II claim that they are not seeing compatibility with this modulation signal. What do you make of that?

COLLAR: CDMS-II is observing a spectrum of irreducible signals. That is, they've tried their best to reject them but they still remain, and they have essentially the same energy spectrum as ours. The material of their detector is also the same as ours – germanium.

CDMS can only marginally exclude what we are observing, and that is after much trying. I claim that they are not doing an unbiased job, and that they're neglecting important facts. I don't see any contradictions between CDMS-II data and ours. To the contrary, there is quite a good chance that there might be a lot in common between our data and theirs.

TKF: You've been involved in other experiments to detect dark matter particles – namely COUPP, the Chicagoland Observatory for Underground Particle Physics at Fermi National Laboratory. This experiment uses a quartz bell jar or bubble chamber as a detector for WIMPs. But this type of detector was conceived by physicist Donald Glaser in 1952. Why turn to an old technology in the 21st century race to detect dark matter?

The old saying "There's nothing new under the sky" actually applies remarkably well to the field of radiation detection. There are only so many ways you can detect radiation, and we seem to have gone through most of them. If you look at the history of our field, there have been very few important additions to the repertoire of radiation detectors in the last 30 or 40 years. There are instead a lot of variations around the same themes.

I started working with superheated liquids at the University of Paris. In my case, contact was purely coincidental. I was working on something unrelated to dark matter when I ran into a paper in a journal called Health Physics. They were talking about radiation dosimeters used to monitor neutron dose in hospitals, while being extremely insensitive to gamma radiation. I thought, "That sounds like a WIMP detector". I went to my boss in Paris, Georges Waysand, and asked, "What's going on with these detectors?" and he said, "I have no idea." So we decided to look into them. When I came to Chicago we moved to using the same concept in the form of bubble chambers.

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"The old saying "There's nothing new under the sky" actually applies remarkably well to the field of radiation detection. There are only so many ways you can detect radiation, and we seem to have gone through most of them."

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Let me explain something that is unique about the bubble chamber. In DAMA and CoGeNT, at the end of the day we are dealing with electrical pulses. In DAMA you have a flash of light that is invisible to the eye, and there's a photomultiplier that converts it and amplifies it into a small current. All these things are happening very, very close to the electronic noise in these devices. In CoGeNT, it's the same story. We pull the ionization signal out of the crystal and we amplify it. This is done close to the noise of the detector.

But a bubble is a bubble is a bubble. If you started to see an annual modulation in the rate of something that at the end of the day is macroscopic and can be detected via standard photography, there's no concern that there's some electronic noise or anything similar conspiring to give you signals you may mistake for a WIMP.

The whole beauty of the bubble chamber is that it all starts with the microscopic process of radiation interacting with matter. And you don't have to move a finger to amplify it. It's all coming from the fact that the liquid is out of equilibrium. It's an unstable system, and when an episode of microscopic boiling happens because a particle interacted with the fluid, everything that ensues, the formation of visible bubbles, is a spontaneous transition from the microscopic world to macroscopic observables. You don't have to amplify small signals through noisy chains of electronics or anything like it.

TKF: In bubble chamber detectors, WIMP collisions are expected to generate a single bubble, while other, more energetic particles are expected to trigger bubble tracks. Why is that?

COLLAR: When a WIMP strikes a nucleus, that nucleus doesn't go very far at all, whether the detector medium is a liquid or a solid. The distance is of the order of hundreds of angstroms, and not much more. The reason is that the nuclear recoil is pretty heavy. The nucleus slows down rapidly; it bangs around a lot and hits a lot of other nuclei, and it dissipates its energy very, very fast over a very short distance.

That's why when a nuclear recoil happens in a bubble chamber liquid, it produces a seed of nucleation, an episode of very local, microscopically localized high temperature, caused by this nucleus bouncing around and hitting other nuclei. If you were able to stick a thermometer at the point of interaction, it would measure an effective temperature in the hundreds or thousands of degrees.

Under some conditions, you can create a microscopic bubble. Those conditions are met for nuclear recoils because the local heating is very high, precisely because the nucleus doesn't go very far. The recoil track is very short. But for other types of radiation, the energy is deposited over much longer distances. It's the same amount of energy, but it is spread out, and the particle doesn’t heat up the liquid enough locally to produce bubbles. We fine-tune the temperature and pressure of the bubble chamber to be able to detect only bubbles produced by nuclear recoils like those expected from WIMPs, and not the tracks produced by uninteresting known particles.

We catch the bubbles in the act of forming when they are smaller than 1 millimeter. We take short movies, examining the frames in real time every ten milliseconds. The software is looking for a change in the image; essentially you have a motion sensor going, so you catch them as they grow. When you have confirmation that an image change is large enough to be a bubble, then you immediately recompress the liquid so that the whole volume doesn't boil, and you end up with a little movie covering a fraction of a second. In those you can see these bubbles start to grow, start to ascend through the fluid and then shrink back as we recompress the fluid. And then they disappear.

TKF: Getting back to the CoGeNT experiment, now that you've made public this result, what is the next step for you in the search for dark matter?

COLLAR: For about a year now, we've been designing the next generation of CoGeNT detectors, and hopefully they will have lower background noise and an improved ability to perceive smaller signals.

TKF: Is this the same detector model used by CoGeNT, with germanium crystals?

COLLAR: This is the same detector concept, but with a lot of improvements. It's essentially the same thing, but hopefully even better in performance.

TKF: What are your plans for continued studies with bubble chambers?

COLLAR: The bubble chamber, in principle, should allow us to test this hypothesis - that there should be a modulation in the rate of collisions between WIMPs and the nuclei in our detectors. We can make our bubble chamber sensitive to light WIMPs, and we have done that before. We have operated the chamber in conditions where we should be able to see the bubbles produced by these particles - if they exist.

The problem is that there are internal sources of neutrons in our bubble chamber. Some materials inside the bubble chamber are generating – at a very small rate - a neutron every so often. And we have evidence for that, because we see events containing multiple bubbles that can only be neutrons.

We identified where these neutrons are coming from, and we're going to replace those parts of the detector this summer - these sources of internal neutrons in the bubble chamber. After that, we'll attempt to look for light WIMPs with our bubble chambers.

TKF: What are the sources of these internal neutrons inside the bubble chamber?

COLLAR: In this particular case, they seem to be dominated by our ceramic piezos - they are electronic sensors that we use to detect the acoustic emission that accompanies the production of the bubbles. When bubbles form, it's a rather dramatic process. You have a liquid that is out of equilibrium. It's super-heated, so it's a liquid that you've tricked into remaining a liquid when it should be a gas at the pressure and temperature you’ve set.

So, when a bubble forms, it yields quite a release of energy. The bubble expands very fast, and this produces a cracking sound that was described as a "plink" by the inventor of the bubble chamber many years ago – (in 1952, by physicist Donald Glaser at the University of Michigan). He actually used phonograph pickups to detect that sound in bubble chamber prototypes and trigger their photography. In our case, the sound is detected through the ceramic piezo-electric sensors, and we found out that there is enough uranium and thorium in them to produce these neutrons at a very, very low rate. We are getting a neutron essentially every week, and these neutrons start close enough to the active part of the chamber to give us some bubbles.

These piezos have to be replaced, and we already know how to do this. We found better ways to produce those ceramics. There are some inspection windows that need to be replaced as well. Those are the two main sources of internal neutrons that we could find. Everything else we think should be fine as it is.

TKF: So as long as you are eliminating all the known sources of noise, such as the ceramic material that you've identified in your bubble chamber, then hopefully what you're left with is an authentic signal of WIMPs, of dark matter?

COLLAR: Well…

TKF: That would be a leap of logic.

COLLAR: That would be a leap of faith. You would be left wondering, in the case of the bubble chamber, if you have rejected all the possibilities that your signals might be something else - for instance, some other background radiation.

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"I'm going to quote my colleague here in Chicago, (astrophysicist) Rocky Kolb. Rocky says, 'It's going to take a village to discover dark matter,' and I agree with that. It's going to take more than the direct detection community observing these recoils."

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Now, a few months ago, when the signals we have now identified to be these neutrons produced inside the chamber started to show, we had been pretty convinced that we hadn't missed anything. We thought, "These must be WIMPS". And then we saw a triple bubble, which a WIMP cannot produce. WIMPS cannot interact more than once. You're lucky enough to get them to interact at all.

We immediately knew we had this neutron problem, and within a few weeks we knew where they had to be coming from. We measured the radioactivity in the piezos and other materials, and found agreement with the rate of neutron production. We explained away the observed signal.

There is a lesson to be learned there. It teaches you that, not only for bubble chambers but any other WIMP detector, after you clean things up you're always going to be left wondering what else it is that you missed. Particle physics and in particular dark matter searches can be very tricky.

TKF: Another approach on the road toward detecting WIMPs, besides measuring the seasonal modulation, is to measure the direction that a nuclei recoils after a particle collides with it – and the modulation in the direction of recoil over time. That's because according to dark matter theory, WIMPs are expected to strike the Earth from a particular direction in the sky, depending on the time of the day. How far are we from making this kind of measurement, and would it provide stronger evidence for dark matter?

COLLAR: That's actually a technology that nobody has yet - a technology that can see the direction of the recoil. There are small prototypes that researchers have been building, and it is an extremely promising technique.

What we're noticing is just a modulation in the rate of collisions, and that's a lot less complex than detecting a modulation in the direction of the recoil. So right now, what we and everyone else who is trying to detect dark matter have available is technology to look for this annual modulation in rate. That's a poor man's smoking gun, unfortunately.

The day someone observes the modulation in the direction of the recoils – that would be very hard to mimic, and it would be the next step on the road to a discovery. It would be very hard to explain such data as anything else other than dark matter, because there's essentially nothing else in nature that could imitate that.

The problem is that the only way that we know how to spot the direction of a recoil is by stretching the short tracks they make in a solid. They only span on the order of 500 angstroms, so there's no way we could image that in a radiation detector. The solution, then, is to rarify the detector medium, to move to gaseous detectors and to operate them at very low pressure. Then, those tracks - those little tracks that the recoils might produce with a preferred direction if they're coming from WIMPS - they can be stretched to a few millimeters. We have the technologies to image that - barely, but we do.

So, the challenge is that your detector has to use targets that have a very low mass because their density has to be very, very small. At the same time, the detectors must have enough overall mass in order to interact with incoming WIMPs, which have, by definition, a very low probability of striking. And then you end up with enormous devices at a very high cost. One day we may be able to observe this beautiful WIMP signature, but right now the detectors are just small prototypes.

TKF: Let's say eventually you are able to confirm this seasonal modulation in collisions with CoGeNT and with COUPP, and other different experiments show the same thing. And then the day arrives when we can measure the direction of recoils, and we detect a daily modulation in the direction of recoils.

If all these results are replicated with different experiments around the world, which use different materials and different methods, would you feel confident that we have detected WIMPs - that is, dark matter?

COLLAR: I'm going to quote my colleague here in Chicago, (astrophysicist) Rocky Kolb. Rocky says, ‘It's going to take a village to discover dark matter,’ and I agree with that. It's going to take more than the direct detection community observing these recoils. Certainly the directional signature would be fantastic, but I think we’re really far away from getting to that point, if we ever get to that point.

If several experiments of our kind detect the same modulation, that would be tremendous. But personally, I believe you even need a bit more than that. And what else is that little extra?

Well, accelerator experiments are in principle sensitive to the same types of particles that we’re searching. If you can produce man-made WIMPs in accelerator experiments, and they match the properties that we observe in our experiments, that would be fantastic.

On top of anything that the detection community might find, there's a theoretical framework that explains why these particles exist, why they have the mass they have, the probability of interaction that we observe in experiments, etc. This theoretical framework also generates new predictions that you can go out and test.

If those theories are confirmed, at that point, we could say that we did it.

TKF: What are the perils of relying solely on direct detection experiments, without returning to theory to check on what you are seeing?

COLLAR: The problem with just relying on direct detection experiments is the following: we are biased. For instance, we are paying attention to these light WIMPs, but why? Because they are really almost the only thing left that could explain DAMA’s observations. Everything else seems to be excluded, so you start to pay a lot of attention to those.

Now, maybe the CRESST guys are paying more attention to those 20 events than they should, because they're biased by DAMA’s pre-existing results. Same exact thing applies to us and our modulation within CoGeNT. So on and so forth.

There have been plenty episodes in the history of particle physics where a number of experiments have observed the same thing, and then years later an equally large number of experiments found nothing. And in some instances, there was never a good explanation as to why the first batch of experiments saw anything at all in the first place.

You know, things come and go. A few years ago, physicists thought they were observing nuclear structures containing five quarks, the so-called pentaquarks. Eleven experiments had pretty good solid evidence for them, and then many more experiments came along and saw nothing. And now the interest is pretty much dead.

Nobody knows what happened there. We do not have a good explanation as to why these objects were observed in the first place. The evidence just went away. So that's why you should not rely exclusively on direct detection experiments for dark matter, in my opinion.

I am much more conservative than many of my colleagues. Some will tell you that their experiment, on its own, is going to find dark matter, with absolute certainty. Crazy as that sounds.

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Related Links:
KICP Members: Juan I. Collar; Edward W. Kolb
Scientific projects: Chicagoland Observatory for Underground Particle Physics (COUPP); Coherent Germanium Neutrino Technology (CoGeNT)

by Steve Koppes, The University of Chicago News Office

When Angela Olinto communicates with other cosmologists, they often rely on equations to transmit their scientific thoughts quickly. But teaching cosmology to undergraduate non-science majors requires completely different methods.

It challenges your imagination," says Olinto.

"We have the saying that we teach teachers. We learn a lot from these future teachers. We're actually teaching and learning pretty much at the same rate." - Angela Olinto

The Department of Astronomy & Astrophysics does not offer an undergraduate major but provides a variety of service courses for undergraduates who wish to learn about the universe. Olinto has been significantly involved in organizing and teaching these courses.

Cosmology for non-science majors
In 1998, she helped redesign the department's classes for undergraduates from non-science majors. The following year, she helped develop the department's specialization in astrophysics for science majors.

Then in 2008, Olinto helped develop a sequence of three study-abroad courses in astronomy and astrophysics at the University of Chicago Center in Paris. Olinto recently returned from Paris, where she had been teaching a course titled "The Origin of the Universe and How We Know It."

That course is for non-science majors, as are her courses on the "Origin and Evolution of the Universe" and on "European Astronomy & Astrophysics." For science majors, Olinto also has taught the Physics of the Early Universe and the Physics of Galaxies in the Universe.

"These were all new classes, actually, every single one of them," she says.

Olinto approaches the teaching of cosmology to non-science majors with the idea that "everybody should be able to get some of it and that curiosity is really the requirement more than the mathematical skills."

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Related Links:
KICP Members: Angela V. Olinto