Steve Gelbart of Rehovot, one of the world's foremost mathematicians, is a happy man - and that's saying something. A native of Syracuse, NY, Gelbart came on aliya with his wife and three young children in 1983. "In 1977 I received a Sloan Fellowship that allows you to work and study anywhere in the world. My wife was a Francophile and we thought of Paris, but by that time we were getting more interested in things Jewish, so we came to the Hebrew University in Jerusalem. We loved Israel and we stayed," says Gelbart. Ten years ago, the Weizmann Institute expert on the Riemann-Zeta Function suffered a devastating blow that could easily have ended both his his up-beat, positive attitude and his life. Instead it had almost the opposite effect: In many ways, says Gelbart, the near-disaster actually improved his life. The day of the near-tragedy began like any other summer day. "I'd played some tennis," he recalls. "It was a warm day and when we'd finished I felt a little sick - I thought I was just overheated. When it continued, I went to a doctor. He looked me over and said it was probably just a bit of flu, which sounded reasonable enough. I was in great physical shape, no high blood pressure. I worked out, and ran every day. I wasn't overweight and had no medical problems of any kind. So the doctor told me to go home and take it easy, which I did. But that evening, I was working at my desk when I felt a sudden pain in my head. When I started to get up, I just collapsed." Gelbart suffered a massive stroke that left him semi-conscious for several days. "I remember very little of the next few days," he says. "I have some vague memories of feeling very stiff and recall seeing myself floating around. But within a week, although I still couldn't speak, I was able to acknowledge my wife and twin brother - who'd flown in from California. By the third week, I was able to sit in a wheelchair and was then transferred to a rehabilitation center where I spent six weeks." For Gelbart, who, in his 35-year career has earned a reputation as one of the world's primary authorities on "automorphic forms" - a highly complex number theory that combines ideas from algebra, geometry and analysis - having to relearn how to walk and talk could have been a psychological disaster, well beyond all the physical challenges. But it didn't affect Gelbart that way. "I was never discouraged and never depressed," he says. "Not even for a minute. I saw other stroke patients who were bitter and discouraged - I understand that completely. But for me, I didn't feel anything like that. My mind doesn't work that way." Instead, Gelbart credits the stroke for pushing his mind's "happiness meter" all the way. "I was always a happy person. Why? I'm not sure. It might have been my upbringing. My mother was always happy - all her life she suffered from health problems, starting with rheumatic fever when she was just three years old. But she was always happy, positive and upbeat, living life to the fullest. Her father was like that, too. They were just happy people. It was their character, who they were," he says. Gelbart is quick to point out that he's not a "Pollyanna" or one of the fabled cockeyed optimists. "I realize my point of view is unusual," he says. "Most people think that happiness is something you have to strive for, something you work at to attain. But for me, it's just something I am. Is happiness a choice? Possibly. But there are others like me - my son-in-law is another happy person. He always has a smile on his face. When he tells you what happened in his day, he only remembers the good things, never anything that was bad." Gelbart's connection to music was something else that changed after the stroke. "I'd always liked music, but after the stroke I loved it with a passion. My whole family is musical. Both my mother and twin brother played cello, one sister played violin and another sister and I both played piano. My father encouraged us all. As I was recovering, my wife pushed me to get back to music, but playing the piano was difficult because I couldn't make my fingers work right. Then last summer, someone asked, 'What's your favorite instrument?' Of course I replied 'cello.' 'So why don't you play cello?' And then I thought, well, why not? So now I'm taking cello lessons and loving it," he says. Music is more to Gelbart than just notes. "I feel music on so many different levels. It's something my whole body resonates with - I feel the music with every cell. This extreme sensitivity for music isn't entirely unique," Gelbart adds, noting that it's something that happens to a small but significant number of stroke victims. His emotions were also magnified by the stroke. "I spent about two-and-a-half years crying - crying with happiness. Everything moved me to tears, whatever it was. Then one day, that extreme emotionalism also stopped," he says. Today, none of the outward signs of the stroke are obvious, although Gelbart says he still struggles with some things. "I lost almost all my Hebrew and still haven't recovered much of it. When I search for a Hebrew word, my second foreign language, French, comes out instead. Sometimes I make mistakes even in English - maybe I want to say 'carrot,' but 'tomato' is what I say." One thing that hasn't changed is Gelbart's passion for what he calls "the beautiful thing," mathematics. "Mathematics makes you see God at work," he says. "It's a process of uncovering and discovering reality - mathematical reality, the kind of truth that exists forever." Gelbart is now back at work at the Weizmann Institute, teaching, writing and thinking. Traveling and seeking out buildings designed by his favorite architects is another pleasure. "My favorite architects are Moshe Safdie [an Israeli] and [Chinese-born] Leoh Ming Pei. I know where in the world all the buildings they designed are located. I enjoy finding those structures, looking at them and just appreciating their beauty." Even Gelbart's world view has changed. "Now I don't let all the small things bother me - if you let yourself, the bad things will just fill you up. So I simply don't see them. I think of all the good things and ignore the rest." What's a small thing? "Maybe something like politics. I know the general situation and who's who, but I'm not hooked to the news hour by hour." "What happened to me could happen to anyone," Gelbart summarizes. "My idea now is to just live, enjoy and appreciate all that life has to offer. My 60th birthday is coming up and there's going to be a gathering where I'll be able to see lots of my old friends. That's the kind of thing that makes me very happy indeed."