He and his roommate last year shared the exact same birthday, but had absolutely nothing in common. Since then, he says, he has not believed the stars at a person's birth determine his or her personality.

The Expert

Shea, who has a degree in the history and science of astrology from the University of Massachusetts, teaches classes in astrology at the Seven Stars bookshop in Harvard Square and predicts clients' futures from their star charts.

He says his belief in astrology grew over the time he studied the practice. He says he is "able to tell more than chance what a person's sun sign is," and can shed light on personalities and past histories from star charts.

"I've been right a number of times, and I know it's not based on chance," he says.

Kathleen I. Finnegan, who prepares star charts for patrons at Seven Stars, says the persistance of the ancient practice of astrology is good proof of its effectiveness.

"Over 8,000 years of humanity observing things, they've been able to come up with pretty good ideas of what happens, say, when Mars is an Aries," she says.

As an example, Finnegan, 40, offers her intuition throughout her life that she would never have children. When she discovered her star chart had "Saturn moving backwards in the sky in the fifth House," which meant that she was extremely unlikely to become a parent, her belief in astrology was confirmed.

"Basically, the birth chart is a physical map of the heavens, the places the planets are in relation to each other." she says. "Because there is no one else born at the same exact time, it's unique."

But Harvard professors dispute the astrologers' claims and dismiss the use of the stars to predict personality and the future as groundless.

"It's like a religion more than anything else," says Professor of Astronomy Robert P. Kirshner, who chairs the Astronomy department. "There's no evidence that astrology predicts the world better than chance."

And Assistant Professor of the History of Science William R. Newman, who teaches a class on the history of the occult sciences, says the astrological predictions are not legitimate.

"I think the answer is very simply no," Newman says of the practice's validity. "There is no scientific basis."

But salespeople at bookshops specializing in the occult say despite the academics' skepticism, they have seen no slacking off of demand for astrology books and readings.

"Some people really believe it determines your life," says a salesperson at Arsenic and Old Lace, a bookshop with a large stock of resources on the occult.