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The Hunt for Dark Matter: A Conversation with PFC's Juan Collar
September 2, 2011
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."
$10 million gift to enhance faculty support in Physical Sciences Division
September 29, 2011
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.Learn more >>
2011 physics Nobel laureates collaborators on UChicago, Fermilab projects
October 5, 2011
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.Learn more >>
Science pubs create lively intellectual exchange: UChicago speakers help bring informal research discussions to Chicago's suburbs.
December 1, 2011
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 Cafe 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."Learn more >>
New Twist in the Search for Dark Matter
December 2, 2011
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.Learn more >>
South Pole centennial history includes UChicago telescopes
December 14, 2011
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.Learn more >>