HARVARD GAZETTE ARCHIVES

Matias Zaldarriaga: 'By looking at this radiation, we can actually see a picture of the universe 400,000 years after the big bang.' (Staff photo Rose Lincoln/Harvard News Office)

Zaldarriaga, named professor of astronomy in July, is an expert in cosmology, which is the study of the origins and evolution of the universe.

A theoretical astrophysicist, Zaldarriaga is trying to understand the faint cosmic whispers of the big bang, that split-second explosion of inconceivable violence when all matter was hurled outward on a journey that would form the universe around us - somewhere between 10 billion and 20 billion years ago.

The period from the big bang to about 400,000 years later, when radiation called the "cosmic microwave background" was formed, is the focus of Zaldarriaga's research.

The cosmic microwave background radiation is thought to be a very faint echo of the big bang, and researchers believe that it provides a window back into time. By studying it, astronomers are seeking to understand conditions 400,000 years after the universe was created.

"By looking at this radiation, we can actually see a picture of the universe 400,000 years after the big bang," Zaldarriaga said.

What they see is that the cosmic microwave background radiation is nearly evenly dispersed throughout the universe. That means that astronomers examining it from Earth see very much the same thing no matter what part of the sky they look at.

But they don't see exactly the same thing wherever they look.

Measurements in the past decade or so have detected slight variations in the cosmic microwave background that researchers believe are the first signs of the clumping of matter in the universe that eventually led to the formation of galaxies, stars, and planets.

"We're seeing early stages of the process of formation of objects in the universe," Zaldarriaga said.

Zaldarriaga's own work has shed significant light on the cosmic microwave background. As a doctoral student, Zaldarriaga developed an algorithm to calculate variations in the cosmic microwave background that has become a standard tool in the field.

"Matias ... is a recognized leader in theoretical cosmology and is clearly one of the top young scientists of his generation," said Astronomy Department Chair Lars Hernquist. "He is an emerging superstar in the field of cosmology and will be an important contributor to Harvard for many years to come."

Scientists believe that matter in the initial ball right after the big bang occurred was very nearly uniformly distributed. Since then, matter has become organized into galaxies, stars, planets and other bodies, but how those initial differences were created is a question that still intrigues researchers.

Zaldarriaga has focused recent attention on the first second of creation, in a period called inflation, when the original ball of matter began to rapidly expand, probably unevenly. Signs of that uneven expansion are likely reflected in the slight variations in the cosmic microwave background and ultimately in the makeup of the universe today.

"The universe is not homogenous, it changes from place to place. We'd like to know how that came about," Zaldarriaga said.

Zaldarriaga came to Harvard in 2003 from New York University (NYU) as an associate professor of astronomy and physics. He had been an assistant professor at NYU since 2001. He received his doctoral degree from the Massachusetts Institute of Technology in 1998 and his bachelor's degree in 1994 from the University of Buenos Aires in his native Argentina.

The question of the universe's creation and how it reached its present form has intrigued Zaldarriaga since his college days, when as an undergraduate in physics, he wrote his senior thesis inspired by the measurements coming from the Cosmic Background Explorer satellite, or COBE, which first detected the variations in the cosmic microwave background.

"I got into it and just couldn't leave," Zaldarriaga said. "It's just very exciting."

alvin_powell@harvard.edu

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