KICP in the News, 2009

Cosmologists aim to observe first moments of universe
The University of Chicago News Office, February 16, 2009
by Steve Koppes, The University of Chicago News Office

During the next decade, a delicate measurement of primordial light could reveal convincing evidence for the popular cosmic inflation theory, which proposes that a random, microscopic density fluctuation in the fabric of space and time gave birth to the universe in a hot big bang approximately 13.7 billion years ago.

Among the cosmologists searching for these weak signals will be John Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy & Astrophysics at the University of Chicago. Carlstrom operates the South Pole Telescope (SPT) with a team of scientists from nine institutions in their search for evidence about the origins and evolution of the universe.

Now on their agenda is putting cosmic inflation theory to its most stringent observational test so far. The test: detecting extremely weak gravity waves, which Einstein's theory of general relativity predicts that cosmic inflation should produce.

"If you detect gravity waves, it tells you a whole lot about inflation for our universe," Carlstrom said. It also would rule out various competing ideas for the origin of the universe. "There are fewer than there used to be, but they don't predict that you have such an extreme, hot big bang, this quantum fluctuation, to start with," he said. Nor would they produce gravity waves at detectable levels.

Carlstrom and his colleague Scott Dodelson will be on panel of cosmologists discussing these and related issues on Monday, Feb. 16 at the American Association for the Advancement of Science annual meeting in Chicago. Their session, "Origins and Endings: From the Beginning to the End of the Universe," will meet from 9:30 a.m. to 12:30 p.m. at the Hyatt Regency Hotel.

Fellow panelists will include Alan Guth of the Massachusetts Institute of Technology. In 1979, Guth proposed the cosmic inflation theory, which predicts the existence of an infinite number of universes. Unfortunately, cosmologists have no way of testing this prediction.

"Since these are separate universes, by definition that means we can never have any contact with them. Nothing that happens there has any impact on us," said Dodelson, a scientist at Fermi National Accelerator Laboratory and a Professor in Astronomy & Astrophysics at the University of Chicago.

But there is a way to probe the validity of cosmic inflation. The phenomenon would have produced two classes of perturbations. The first, fluctuations in the density of subatomic particles happen continuously throughout the universe, and scientists have already observed them.

"Usually they're just taking place on the atomic scale. We never even notice them," Dodelson said. But inflation would instantaneously stretch these perturbations into cosmic proportions. "That picture actually works. We can calculate what those perturbations should look like, and it turns out they are exactly right to produce the galaxies we see in the universe."

The second class of perturbations would be gravity waves—Einsteinian distortions in space and time. Gravity waves also would get promoted to cosmic proportions, perhaps even strong enough for cosmologists to detect them with sensitive telescopes tuned to the proper frequency of electromagnetic radiation.

"We should be able to see them if John's instruments are sensitive enough," Dodelson said.

Carlstrom and his associates are building a special instrument, a polarimeter, as an attachment to the SPT, to search for gravity waves. The SPT operates at submillimeter wavelengths, between microwaves and the infrared on the electromagnetic spectrum.

Cosmologists also use the SPT in their quest to solve the mystery of dark energy. A repulsive force, dark energy pushes the universe apart and overwhelms gravity, the attractive force exerted by all matter. Dark energy is invisible, but astronomers are able to see its influence on clusters of galaxies that formed within the last few billion years.

The SPT detects the cosmic microwave background (CMB) radiation, the afterglow of the big bang. Cosmologists have mined a fortune of data from the CMB, which represent the forceful drums and horns of the cosmic symphony. But now the scientific community has its ears cocked for the tones of a subtler instrument—gravitational waves—that underlay the CMB.

"We have these key components to our picture of the universe, but we really don't know what physics produces any of them," said Dodelson of inflation, dark energy and the equally mysterious dark matter. "The goal of the next decade is to identify the physics."


Related Links:
KICP Members: John E. Carlstrom; Scott Dodelson
Scientific projects: South Pole Telescope (SPT)
Evalyn Gates, Eyeing the universe through Einstein's telescope
The University of Chicago News Office, February 23, 2009
by Steve Koppes, The University of Chicago News Office

Scientists are harnessing the cosmos as a scientific "instrument" in their quest to determine the makeup of the universe.

The University of Chicago's Evalyn Gates calls the instrument "Einstein's telescope." The instrument is actually the phenomenon of gravitational lensing, which acts as a sort of natural telescope. Gates's recently published book, Einstein's Telescope: The Hunt for Dark Matter and Dark Energy in the Universe, explains how it works.

Although based on Albert Einstein's general theory of relativity, the effect is easily demonstrated. Look at a light through the bottom of a wine glass, Gates recommends, and see the resulting light distortion.

"Einstein's telescope is using the universe itself as a lens through which we can seek out galaxies that would otherwise be too faint to be seen," says Gates, Assistant Director of the University's Kavli Institute for Cosmological Physics.

Einstein's First Inklings
Long ago Einstein recognized the potential existence of gravitational lensing, a consequence of his theory of general relativity. According to general relativity, celestial objects create dimples in space-time that bend the light traveling from behind.

Einstein realized that the gravitational influence of a foreground star could theoretically bend the light of another star sitting almost directly far beyond it, producing two images of the background star.

"Gravitational lensing magnifies things as well as making multiple images and distorting the shape of images, so you can actually use it as a magnifying glass," Gates explains.

But, assuming that the effect would be too weak to detect, Einstein immediately dismissed its significance. "What he didn't anticipate, among other things, were the incredible leaps forward in telescope technology," Gates says.

Seeing the Invisible
Astronomers now use gravitational lensing to look for dark matter and the imprint of dark energy, two of the greatest modern scientific mysteries.

Dark energy, which acts in opposition to gravity, is the dominant force in the universe.

"We can't see dark energy directly by any means, but we're looking for how it has sculpted the matter distribution of the universe over the past few billion years, since it's been the dominant factor, and also how it has affected the rate at which the Universe is expanding" Gates says.

And gravitational lensing is essentially the only method astronomers have for tracing out the web of dark matter that pervades the Universe, and determining how dark energy has impacted the evolution of this web. "It's really hot scientifically," she says.

Like dark energy, dark matter is also invisible. It accounts for most of the matter in the universe, but exactly what it is remains unknown. Scientists only know that dark matter differs significantly from normal matter (which is essentially composed of protons and neutrons) that dominates everyday life.

"What we're made of is just about five percent of everything that's in the universe," Gates says.

A Look into Galaxies Past
Scientists also use galaxy clusters as gravitational lenses to probe 13 billion years back into the history of the universe. "They're seeing some of the very first galaxies," she says.

Gravitational lensing offers astrophysicists a tool comparable to magnetic resonance imaging and computing tomography, which have provided health professionals with unprecedented new views of the human body.

"Gravitational lensing is going to allow us to image the universe in ways that wouldn't have been possible even 50 years ago," she says.

During the 20th century, quantum mechanics and general relativity radically altered scientists' view of the universe, Gates says. Investigations of dark matter and dark energy may do likewise.

"It may lead us to another revolution in our understanding of the most fundamental aspects of the universe, time, matter, and energy."


Related Links:
KICP Members: Evalyn I. Gates
'Around the World in 80 Telescopes' webcast to include South Pole Telescope
The University of Chicago News Office, April 2, 2009
by Steve Koppes, The University of Chicago News Office

The South Pole Telescope (SPT), which the University of Chicago operates with eight partner organizations, will be among the observatories taking part in a 24-hour live Webcast titled "Around the World in 80 Telescopes."

The event is part of 100 Hours of Astronomy, the cornerstone project of the International Year of Astronomy 2009 (IYA2009). The United Nations proclaimed IYA2009 on Dec. 20, 2007, to help citizens of the world rediscover their place in the universe.

The 100-hour astronomy marathon will consist of more than 1,500 public outreach events in more than 130 countries from April 2 to 5. The SPT live video webcast is scheduled to begin at 2:25 a.m. CDT Saturday, April 4.

Serving as webcast spokesmen will be Ross Williamson, a research scientist at the University of Chicago, and Erik Shirokoff, a graduate student at the University of California, Berkeley. To view the webcast, visit, or

Taking advantage of the exceptionally clear, dry and stable atmosphere at the South Pole, the 10-meter SPT is mapping large areas of sky for clues about the mysterious phenomenon know as dark energy. A repulsive force, dark energy pushes the universe apart and overwhelms gravity, the attractive force that all matter exerts.

Other participants in Around the World in 80 Telescopes include Gemini North and Keck in Hawaii, the Anglo-Australian Telescope, telescopes in the Canary Islands, the South African Large Telescope, Chilean observatories such as the Magellan Telescope at Las Campanas Observatory, and the Hubble Space Telescope.


Related Links:
KICP Members: John E. Carlstrom
Scientific projects: South Pole Telescope (SPT)
Class probes nexus of science and policy: Rocky Kolb helped teach a 10-week class called Science, Technology, and Policy
The University of Chicago News Office, April 26, 2009
by Sarah Galer, The University of Chicago News Office

Christine Kolb focuses on urban policy and public resource allocation at the Harris School of Public Policy Studies. And although her career interests lie in urban issues, the second-year graduate student's childhood made her a firm believer in the importance of introducing policy students to science issues.

"I grew up with dinner conversations about inadequate federal funding of science or how policymakers were not aware of what science is, what it accomplishes, and why it’s important," she says, referring to her father, Edward "Rocky" Kolb, the Chair of Astronomy & Astrophysics and the Arthur Holly Compton Distinguished Service Professor. "There is a chasm between the policy that regulates and funds science, and the process of science - what science must do."

Christine's passion for science and policy piqued the curiosity of Robert Michael, the Eliakim Hastings Moore Distinguished Service Professor Emeritus in the Harris School, for whom she is a teaching assistant. An idea started to germinate between them for a class that would combine the two disciplines, which had never been explored at the Harris School.

The result was a 10-week offering called Science, Technology, and Policy - an innovative, non-credit, elective created to expose public policy students to science policy.

"Rocky decided that he wanted students in policy to know more science, and I have 125 students of policy," explains Michael. "It did not take a rocket scientist to figure out that all we had to do is get the two of them together."

Genesis of the Class
When Kolb first spoke with Michael, he lamented how woefully little policy staffers on Capitol Hill knew about science and how he wished that would change.

"We, as political scientists, haven't taken advantage of the complementarity with physical science," says Michael, founding Dean of the Harris School. "Now that we are maturing, it is appropriate for our school to make ties with the physical sciences."

Kolb was one of the distinguished science experts to present weekly briefings at the Winter Quarter class. Other speakers included Kennette Benedict, Executive Director and Publisher of The Bulletin of the Atomic Scientists, who discussed nuclear proliferation; Robert Rosner, Director of Argonne National Laboratory, who discussed energy policy; and Leon Lederman, Nobel laureate and Fermilab Director Emeritus, who briefed the students on science education.

"What a great idea to have a class that would address this, especially because the leadership of the University has a science background, with a mathematician (President Robert Zimmer) and a physicist (Provost Thomas Rosenbaum)," Christine Kolb says.

And even though it was a noncredit obligation, the class was very popular with students.

"Students don't come to the University of Chicago for the weather or for the grades," says Michael. "They come for the knowledge."
'How the other half lives'

Kolb, as the scientist on the teaching team, hopes the success of the class will lead to the creation of a similar one for physical science students to learn about public policy.

"It is important to know a little about how the other half lives," he says.

He became interested in teaching the class for just this reason: to make students aware, as he succinctly put it, of "the policy of science and the science of policy."

The class signals the Harris School's expanding reach beyond the social sciences, all while remaining grounded in the policy tools that the Harris School teaches all of its students.

"From an institutional perspective, Science, Technology, and Policy reinforces the approach to policy taught at Harris," says Christine Kolb. However, "in order to fully understand policy you need to know about the economy, and if innovation from science and technology drives 50 percent of our economy, we need to know about those fields."


Related Links:
KICP Members: Edward W. Kolb
QUIET team to deploy new gravity-wave probe in June
The University of Chicago News Office, May 15, 2009
by Steve Koppes, The University of Chicago News Office

A tiny fraction of a second following the big bang, the universe allegedly experienced the most inflationary period it has ever known.

During this inflationary era, space expanded faster than the speed of light. It sounds crazy, but it fits a variety of cosmological observations made in recent years, said University of Chicago physicist Bruce Winstein.

"Theorists take it to be true, but we have to prove it," said Winstein, the Samuel K. Allison Distinguished Service Professor in Physics at the University of Chicago. "It needs a real test, and that test is whether or not gravity waves were created."

Winstein and his Chicago associates are part of the international QUIET (Q/U Imaging ExperimenT; the Q and U stand for radiation parameters called Stokes parameters) collaboration that has devised such a test.

QUIET's goal: detect remnants of the radiation emitted at the earliest moments of the universe, when gravity waves rippled through the very fabric of space-time itself.

The intensive gravitational fields that existed at these earliest moments, according to Einstein, produced gravity waves that alternatively compressed and expanded space, first in one direction, then another. The cosmic microwave background (CMB) radiation—the afterglow of the big bang—may still carry a faint signature of those gravitational waves, nearly 14 billion years after their creation.

Seeking ethereal quarry
Other collaborations, including the South Pole Telescope (SPT), seek the same ethereal quarry with different techniques. The University of Chicago's Kavli Institute of Cosmological Physics supports both projects.

"No one can say what the best approach is right now," Winstein said, "but we need a variety of attacks on this important problem, and ours is different from most of the others. It's very exciting to be in this game."

At stake is the potential elucidation of new physics, that which falls outside the scope of the standard model. This model, a set of theories that describes the behavior of matter and energy in the universe, cannot explain how points in the sky too far away to have ever been in contact have almost exactly the same temperature. A validation of inflation would solve that problem.

"If we see these gravity waves, they have been called the smoking gun of inflation," Winstein said.

The QUIET experiment began operating last October with an antenna array that contains 19 detectors. Since then, QUIET collaborators at the Jet Propulsion Laboratory in California have produced 91 detectors sensitive to the radiation at a higher frequency.

Over the past several months, the Chicago collaboration has assembled and calibrated these 91 detectors in the basement of the Laboratory for Astrophysics and Space Research.

Winstein's team has tested each detector, adjusting 10 critical voltages for each to yield the best performance. Correctly optimized voltages can improve detector performance by a large factor, Winstein said, making it possible to observe in one day what would have otherwise required a week. This newer, more sensitive array will begin operating in June.

High and dry operation
The QUIET experiment operates in Chile's Atacama Desert, at an altitude of 17,000 feet. "It's very dry, and that's important because this microwave radiation gets absorbed by water vapor," Winstein explained. "And we observe day and night, 10 to 11 months a year."

Observations will continue at least until the end of this year. The team must keep its detectors at a chilling minus 253 degrees Celsius (minus 423 degrees Fahrenheit, close to absolute zero) to boost the odds of detecting the extremely weak gravity-wave signals. These signals would be so weak that electronic noise could easily drown them out.

"One way to eliminate electronic noise is to get your detector very, very cold," said QUIET's Allison Brizius, a graduate student in physics. "The colder it gets, the quieter it gets, the better it can pick up a signal."

The QUIET experiment must both detect and amplify the signal, which puts out only about a billionth of a volt.

"We have to be very careful with such small signals not to introduce any other noise," Winstein said. "We've demonstrated that this technology works, and we're proposing to mass-produce these modules, nearly 2,000 of them."

Winstein comes from a particle physics background, a veteran of 30 years of experimental research at Fermi National Accelerator Laboratory, which also plays a role in QUIET. As a particle physicist, he was exploring physics at the highest energies that an accelerator could then achieve.

Now, as a cosmological physicist probing the CMB, he stands on the brink of reaching nearly to the Planck scale, the highest energies that the universe can create. The CMB, he said, is "probably our best handle on the overall structure of the universe and how it was born."

Related links:

* Bruce Winstein
* QUIET's home page
* The South Pole Telescope and gravity waves


Related Links:
KICP Members: Bruce D. Winstein
Scientific projects: Q/U Imaging ExperimenT (QUIET)
Bruce Winstein discusses the QUIET experiment, which will explore physics at ultra-high energies generated at the birth of the universe (video)
The University of Chicago News Office, May 15, 2009
Astronomer Michael Gladders named 2009 Cottrell Scholar
The University of Chicago News Office, June 30, 2009
by Steve Koppes, The University of Chicago News Office

The Research Corporation for Science Advancement has named the University of Chicago's Michael Gladders a 2009 Cottrell Scholar. Each of the 10 new Cottrell Scholars will receive a $100,000 grant.

Cottrell award recipients are chosen both for the quality of their scientific research and their dedication to teaching. The awards are named for Frederick Gardner Cottrell, whose generosity made the Research Corporation possible, and whose invention of the electrostatic precipitator was an early environmental innovation that reduced pollution from smokestacks.

Gladders, an Assistant Professor in Astronomy & Astrophysics, is constructing the largest-ever catalog of distance groups and clusters of galaxies. The formation of these objects over cosmic time is driven by dark matter and dark energy, and these catalogs will be used to test the properties of these engimatic but dominant components of the universe. He plans to use emerging technologies to bring this new astronomical research into the University's classrooms.

He will incorporate data from an extensive imaging survey of the faint sky into advanced computer programs for teaching and visualization, enhancing the capabilities of these desktop planetaria. Based on these and other new tools, Gladders will create new computerized astronomy labs for use in undergraduate courses.

Founded in 1912, the Research Corporation of Tucson, Ariz., is an advocate for the sciences and a major funder of scientific innovation and research in U.S. colleges and universities.


Related Links:
KICP Members: Michael D. Gladders
Aiming High: The Search for Ultra High-Energy Cosmic Rays
American Museum of Natural History Science Bulletin, July 10, 2009
American Museum of Natural History Science Bulletin

The history of cosmic ray research is a story of scientific adventure. For nearly a century, cosmic ray researchers have climbed mountains, soared in hot air balloons, and traveled to the far corners of the Earth in the quest to understand these energetic particles from space. They have solved some scientific mysteries - and revealed many more. With each passing decade, scientists have discovered higher-energy and increasingly more rare cosmic rays. The Pierre Auger Project is the largest scientific enterprise ever conducted to search for the unknown sources of the highest-energy cosmic rays ever observed.


Related Links:
Scientific projects: Pierre Auger Observatory (AUGER)
Evalyn Gates on Cosmic Magnification
Discover, July 21, 2009

Scientists like to argue, contra Walt Whitman, that understanding something increases our appreciation of its beauty, rather than detracting from it. The image below, as Evalyn Gates explains, is a perfect example. Evalyn is an astronomer at the University of Chicago, and the author of a great new book on the science of gravitational lensing, Einstein's Telescope: The Hunt for Dark Matter and Dark Energy in the Universe (Amazon, Barnes & Noble, Powell's). This post is an introduction to how gravitational lensing gives us some of the most visually arresting and scientifically informative images in all of astronomy.


Related Links:
KICP Members: Evalyn I. Gates
O'Hare Airport exhibit provides portal to cosmos
The University of Chicago News Office, July 29, 2009
by Steve Koppes, The University of Chicago News Office

Visitors to Chicago's O'Hare International Airport this summer may find themselves taking an unplanned "journey" into the cosmos.

"From Earth to the Universe," an exhibit of 56 astronomical images, is on display through the end of the year at O'Hare. Scientists at the University of Chicago's Kavli Institute for Cosmological Physics contributed four of the images.

Two of the Chicago images come from Earth, and two are from space:

* A detector of the Pierre Auger Observatory sitting in the shadow of the Andes Mountains of South America. James Cronin, University Professor in Physics Emeritus, co-founded the Auger Observatory, which is dedicated to the study of rare, ultra-high-energy cosmic rays.
* The South Pole Telescope (SPT) in silhouette against the southern night sky and the aurora australis (southern lights). John Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy & Astrophysics, leads the SPT collaboration.
* Supercomputer simulation of the evolving, large-scale structure in the distribution of galaxies. Andrey Kravtsov, Associate Professor in Astronomy & Astrophysics, performed the simulations.
* A mosaic of galaxy clusters producing the gravitational lensing effect. Michael Gladders, Assistant Professor in Astronomy & Astrophysics, took the images, which display how the gravity of massive clusters bends light, producing arc-like images of distant galaxies behind the clusters.

The exhibit spans 1,000 feet of wall space in a tunnel connecting Terminals 2 and 3 and the Chicago Transit Authority bus stop. Curated by the Adler Planetarium and Astronomy Museum, the exhibit is part of a yearlong celebration of the 400th anniversary of the telescope, the International Year of Astronomy.


Related Links:
KICP Members: John E. Carlstrom; James W. Cronin; Michael D. Gladders; Andrey V. Kravtsov
Scientific projects: South Pole Telescope (SPT)
University of Chicago announces new Director of Office of Special Progams - Key Partner for KICP Space Explorers Program
The University of Chicago News Office, November 4, 2009
QUaD: High-precision measurements confirm cosmologists' standard view of universe
The University of Chicago News Office, November 5, 2009
The University of Chicago News Office

An international team that includes the University of Chicago has unveiled a detailed picture of the seeds of structures in the universe. These measurements of the cosmic microwave background (CMB) - a faintly glowing relic of the hot, dense, young universe-put limits on proposed alternatives to the standard model of cosmology and provide further support for that model, confirming that dark matter and dark energy make up 95 percent of everything in existence, while ordinary matter makes up just five percent.

"When I first started in this field, some people were adamant that they understood the contents of the universe quite well," said Sarah Church of the Kavli Institute for Particle Astrophysics and Cosmology at SLAC and Stanford. "But that understanding was shattered when evidence for dark energy was discovered. Now that we again feel we have a very good understanding of what makes up the universe, it's extremely important for us to amass strong evidence using many different measurement techniques that this model is correct, so that this doesn’t happen again." Church co-leads the team, along with Clem Pryke of UChicago's Kavli Institute for Cosmological Physics and Walter Gear of Cardiff University in Wales.

In a paper published in the Nov. 1 issue of the Astrophysical Journal, QUaD researchers release detailed maps of the cosmic microwave background. The researchers focused their measurements on variations in the CMB's temperature and polarization to learn about the distribution of matter in the early universe. Polarization is an intrinsic extra "directionality" to all light rays that is at right angles to the light ray's direction of travel. Although most light is unpolarized-consisting of light rays with an equal mix of all polarizations-the reflection and scattering of a light ray can create polarized light. This property of light is exploited by polarized sunglasses, which block some of the polarized light to reduce glare on sunny days.

The light from the early universe was initially unpolarized but became polarized when it struck moving matter in the very early universe. By creating maps of this polarization, the QUaD team was able to investigate not just where the matter existed, but also how it was moving.

"These new polarization measurements from QUaD are the most sensitive ever made and are the result of huge team effort over more than five years," said Clem Pryke of the University of Chicago.

The QUaD results very closely match the temperature and polarization predicted by the existence of dark matter and dark energy in the standard cosmological model, offering further experimental confirmation that the model is correct. These findings also limit the possibilities of alternative models reinforcing the view that researchers are on the right track, and need to learn more about the strange nature of dark energy and dark matter if they are to fully understand the workings of the universe.

"Microwave background observations are about the most technically challenging in contemporary astrophysics and cosmology," said KIPAC Director Roger Blandford. "It is wonderful to see such solid measurements and such a clear confirmation of the theory."

The QUaD (QUEST at DASI) project utilizes the Q U Extra-galactic Survey Telescope (QUEST) instrument at the South Pole that was installed on the mechanical structure from a previous experiment called DASI (Degree Angular Scale Interferometer)..

The principal members of the QUaD collaboration are the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University and the Department of Energy's SLAC National Accelerator Laboratory, the Kavli Institute for Cosmological Physics at the University of Chicago, the California Institute of Technology, the Jet Propulsion Laboratory, Cardiff University (United Kingdom), University of Edinburgh (United Kingdom) and Maynooth College (Ireland).


Related Links:
KICP Members: Clement L. Pryke
Scientific projects: QUaD
Seeing the unseen: A cosmic lens on dark matter
The University of Chicago News Office, December 17, 2009
by Steve Koppes, The University of Chicago News Office

Observing dark matter, the unseen stuff that makes up most of the universe, takes some ingenuity. Michael Gladders has a few creative suggestions.

This mysterious matter is called "dark" because it doesn't interact with light. But astronomers can observe its giant fingerprints across the cosmos in the distortions it causes, as gravity from huge clusters of galaxies and dark matter bend nearby light on its way toward Earth.

Gladders will take a new tack by seeking answers among the most massive objects in the universe-galaxy clusters. The huge tug of gravity from any immense distant object can become a sort of lens, altering light waves like a pair of reading glasses. Gladders' research focuses on that effect, called gravitational lensing. If he knows what to expect without the distortion, he can calculate whatever was making it happen.

"Gravity almost acts like an optic, or a lens, would," said Gladders, Assistant Professor in Astronomy. "The gravity in this case is caused by the mass of huge clusters of galaxies, which are mostly dark matter."

Dark matter has baffled physicists and astronomers since the 1930s, when its presence was inferred by calculations to explain the motions of the galaxies within galaxy clusters. While no one yet understands dark matter, there are plenty of competing theories, and Gladders plans to help sort them out.

"We will ask how the lens acts to distort the background images in the sky,' he said. "Then we can say, 'This is what you'd expect given this amount of dark matter.' At a minimum you eliminate some of the competing models, and perhaps one will come to the fore."

Gladders tests the strength of gravitational lenses, much like an optometrist can calculate the prescription for a pair of eyeglasses. The goal is to find just the right kind of clusters. "Clusters are rare," Gladders said. "And those that exhibit lensing are even rarer, and really hard to find."

To search for galaxy clusters that act as gravitational lenses, Gladders combs through large galaxy catalogs for the sometimes subtle high densities in the galaxy distribution that mark the clusters. The largest such source catalog is the Sloan Digital Sky Survey, which contains information on some 250 million objects.

The second-largest catalog is Gladders' own Red-Sequence Cluster Survey, comprising roughly 150 million objects, some of them more than a million times fainter than the faintest objects visible by naked eye.

Gladders will reduce this list of suspects to the approximately 50,000 most-promising galaxy clusters. The task then is to generate a list of the few hundred gravitational lenses lurking in this vast data set. "These are visually spectacular objects," Gladders said. "They have a real discovery aspect to them."

Gladders is a regular at the world's top observatories. He has visited the Magellan telescopes at Las Campanas Observatory, in the remote Andean foothills of Chile, more than 30 times. Getting there is a privilege and a feat, taking months of preparation. So when his last visit overlapped his teaching of the "Astronomy and Astrophysics of Stars" class at Chicago, Gladders simply lectured from Chile via the Internet.

He was able to share with students the joy of doing astronomy 18 hours a day, on three or four hours of sleep and lots of coffee, running the telescope, taking data, modifying the program. "When it's cloudy one night, you have to figure how to get two nights of work done the next night," he said.

"I still enjoy it, the fascinating moments on a mountaintop, in a control room, with banks of computers. There's a mystical quality to the experience, staring at the night sky, figuring out deep questions you've been asking for years. As I prioritize things, that ranks above almost anything else."

Born in Southampton, England, Gladders studied briefly at the University of Victoria in Canada, before being expelled for poor grades. "This can teach students that sometimes you can fall down and get back up," he said.

He worked at geophysics for the oil industry in Calgary until he was readmitted to college. He moved on to a Ph.D. at the University of Toronto, and became a fellow at the Carnegie Observatories in Pasadena, Calif., before joining the University of Chicago faculty.

Gladders now is helping to acquire the big samples that astronomers need for robust tests of their models. "A few years ago the total known sample of lenses was just a few handfuls of objects," he said. "We are now finding hundreds of these objects.'

As to direct measurement, Gladders said, some astronomers have high hopes for the Large Hadron Collider, the new accelerator under the Swiss-French border. "The LHC may reveal the 'dark matter particle.'


Related Links:
KICP Members: Michael D. Gladders