Princeton astrophysicist Spergel to show 'baby pictures' of the universe at Bunyan Lecture

By Krista Zala

How old is the universe? Does it stretch on forever? If not, how is it shaped? A telescope a million miles above Earth has detected answers to questions that cosmologists have posed for centuries.

"Cosmology has undergone a revolution from lots of speculation and little data to now knowing the size, shape and likely the fate of the universe," says David Spergel, a theoretical astrophysicist who will deliver the 24th Annual Bunyan Lecture. The Princeton professor's talk, "Taking the Baby Picture of the Universe," will begin at 7:30 p.m. Monday, Nov. 14, at the Braun Auditorium in the Mudd Chemistry Building at 333 Campus Dr. It is free and open to the public.

His research uses sensitive instruments to see what the universe looked like billions of years ago. "It's like taking a baby picture of the universe and using it to tell us a story about its origin and evolution," Spergel says.

In 1982, Spergel graduated with a bachelor's degree in astronomy from Princeton, where undergraduate courses gave him an opportunity to ponder big questions about general relativity, the Big Bang and gravity. He went on to earn master's and doctoral degrees in astronomy from Harvard by 1985. And he's never stopped searching for the answers.

Spergel has spent the last several years focused on the Wilkinson Microwave Anisotropy Probe (WMAP), a telescope that takes pictures of the universe as it looked more than 13 billion years ago. Launched on June 30, 2001, WMAP is a collaborative effort between NASA and six universities. Its first photos show the universe when it was a mere 379,000 years old, comparable to taking a picture of an 80-year-old on the day of her birth.

Astronomers can take pictures of the past because light travels at a finite speed.

"An alien living in a star system 20 light-years away looking at us would see our planet as it was 20 years ago," says Spergel.

What, with leg warmers and bad hair?

"I had more hair then," Spergel says.

Sensitive telescopes can detect galaxy clusters millions of light-years away at the edges of the expanding universe.

Cosmologists discovered years ago that the temperature of the sky is not totally uniform. It varies by only millionths of one degree, but sophisticated instruments can detect these differences. These tiny fluctuations, or anisotropy, reveal information about matter in the early universe that allows cosmologists to ascertain the conditions in which galaxies and other cosmic bodies were born.

Traditional, or optical, telescopes look at light in the visible part of the spectrum. In contrast, WMAP detects microwaves. Named after David Wilkinson, a member of the team who died in 2002, the probe orbits a million miles (1.5 million kilometers) above Earth.

It revolves around the sun in a geosynchronous Earth orbit. Its two telescopes point into deep space and measure temperature variations between two points in the sky. The exposure time for each microwave picture lasts six months. By the time WMAP finishes its mission in 2007, NASA hopes to map the temperature of the known universe.

In 2001, the year of the WMAP launch, Time magazine rated Spergel as one of the best American scientists and the MacArthur Foundation gave him a half-million-dollar "genius" grant. He currently heads the NASA Space Science Advisory Council.

Spergel's public lecture will be followed the next day by a more technical lecture at 4:15 p.m. Tuesday, Nov. 15, at the Hewlett Teaching Center, Room 201. He will discuss the next steps in solving questions about dark energy, dark matter, galaxy formation and the origins of the Big Bang in a talk titled "Cosmology from WMAP and Beyond."

The Bunyan Lecture Series, hosted by the Astronomy Program in the Department of Physics, was created from the estate of the late James T. Bunyan, a member of the Hoover Institution, whose will specified that the lecture series would "inquire into man's changing vision of the cosmos and of human destiny as revealed in the latest discoveries in the fields of astronomy and space exploration."

Krista Zala is a science-writing intern at Stanford News Service.