ALDA ONSTAGE.(The Talk of the Town)(Alan Alda )

Alan Alda was still going strong last week, just before the end of his four-month run in the revival of David Mamet's 1984 Pulitzer Prize-winning play "Glengarry Glen Ross."

"Maybe I'm supposed to show some wear and tear with the eight shows a week, but this is a great play, and I love acting," he said, an hour before curtain in his tiny dressing room. "This is my ecstasy."

His room was bereft of the usual show-biz memorabilia; instead, it was decorated like a study--leather armchair, small sofa with white woollen throw, a Kandinsky print, and a framed countryside photograph taken by Arlene Alda, his wife of forty-eight years. No posted photos of her or of their three daughters and seven grandchildren; no clippings of Alda as Captain Hawkeye Pierce in "m*a*s*h" or, recently, as Senator Vinick in "The West Wing" or Senator Brewster in the movie "The Aviator"; no glossies of Emmy or Golden Globe honors.

"On the stage, here and now, you have final cut," he said. "I'm free to make it different every night. It's the act of imagination that involves the whole brain and the whole body. It's a wonderful feeling. Mamet has told people that this production of the play is the best of all."

Without abandoning his exuberant tone, Alda recalled an epiphany he had a couple of years ago in Chile, where he had emergency surgery for intestinal blockage. As the host of the PBS series "Scientific American Frontiers," he had gone to a mountaintop observatory, to interview astronomers about dark energy in the universe. "I was also trying to find out what Einstein meant when he said gravity is curved space," Alda said. "Instead of finding out why I couldn't picture the fourth dimension, I found out that I now had another chance at life, and, from that moment on, it was clear to me that I would do exactly what I wanted to do. So the first thing I did was a lovely little three-character play at the small Bay Street Theatre, in Sag Harbor, not far from where we live. I didn't need a big audience. I was on the stage. And I was enjoying the pure pleasure of acting."

Alda's birth name is Alphonso D'Abruzzo. "Same as my father's name. We took the first two letters of the first and last names and put them ...