For two hours early one October morning in a mostly empty Science Center lecture hall, the tall dean of the little institute on Garden Street sat by the wall and listened. She took notes on a legal pad in an overflowing leather binder. Occasionally she checked her e-mail on a large, vintage BlackBerry with a green monochrome screen.

The dean of Radcliffe, Drew Gilpin Faust, was a quiet observer at the sometimes-contentious Oct. 10 town hall meeting held by a University-wide science planning committee. At the meeting, a handful of Faculty of Arts and Sciences (FAS) professors pushed back against the committee’s proposal to centralize some science teaching and research across the University.

Faust is an observer no more. As Harvard president, she will need to strike a balance between the humanities and the sciences at a time when the rapid expansion of the latter threatens to make the rest of the disciplines feel left behind.

“Science absorbs vast amounts of money and space, and the rest of us who sit in our offices and read books think we would like to have a small fraction of that money and space,” Jennifer L. Hochschild, the Jayne professor of government, said in an interview yesterday.

Among the challenges Faust will face in the coming years, professors across FAS said, defining the place of science in the University may be the most difficult—and the most essential.

Faust’s controversial predecessor, Lawrence H. Summers, came under fire for, among other things, emphasizing science growth at the expense of other fields. Professor of the History of Science Everett I. Mendelsohn said that Summers “had hitched his wagon to the growth of the natural sciences.”

A lot of money is at stake. More than half a billion dollars’ worth of new science buildings are nearing completion behind the Science Center, and billions more are slated to be spent for the planned science-heavy expansion into Allston.

“People are going to watch the budget—where does money go, where do new professorships go,” Mendelsohn said.

Faust, a scholar of the Civil War and the American South, will be the fifth consecutive Harvard president who is not a scientist. While some Harvard observers have wondered whether her credentials measure up to the needs of a university in the process of aggressively expanding research, FAS professors interviewed yesterday praised the way she nurtured science as dean.

“She’s done a good job at bringing scientists into the Radcliffe Institute,” Hochschild said. “The path of least resistance would have been to make that a humanities and social sciences institution.”

When Faust took over Radcliffe in 2001, the school was still trying to redefine itself after more than a century as a women’s college. Now, the Institute for Advanced Study receives about 800 applications every year for 45 to 50 prestigious fellowship positions. This year, about one-third of the spots are occupied by scientists, engineers, and mathematicians.

Venkatesh “Venky” Narayanamurti, the dean of the Division of Engineering and Applied Sciences, said yesterday that he has worked closely with Faust and trusts her leadership.

She may not know “the details of science,” Venky said, but “I think she’s a broad, learned person.”

And Faust’s impeccable credentials in history may allow her to give sciences the support they need while defusing tensions between the disciplines, Venky said.

“Sometimes you almost have to come from a field other than science to help science,” Venky said. “She knows the historians and others will respect her, and she will respect the sciences, too.”

But Faust must do more than chart a path between jealous disciplines, professors said. To make Harvard a great 21st-century university, faculty members said, she needs to help develop new connections between the hard sciences, the social sciences, and the humanities.

“If one gets out of step with the other, you’ll have Harvard becoming a pale shadow of MIT,” Mendelsohn said.

Despite the magnitude of these challenges, professors said they trust Faust’s leadership skills and vision.

“I think she’s ideally suited to create the dialogues and the give and take that will make Allston possible,” Professor of Economics David I. Laibson ’88 said. “I expect she’ll make everyone understand the tradeoffs.”

—Staff writer Lois E. Beckett can be reached at lbeckett@fas.harvard.edu. —Staff writer Anton S. Troianovski can be reached at atroian@fas.harvard.edu.