He may be adored for his portrayal of Hawkeye the wisecracking doctor in MASH, but Alan Alda has a second passion: science. Which is why he has written a play, Radiance, about the hounding of Marie Curie

Alan Alda works from an office in midtown Manhattan, around the corner from Grand Central station and in the shadow of the Chrysler Building. “It’s funny,” he says, looking up at the skyscraper while waiting for a cab. “I come here every day and I never saw it from this angle before.”

The veteran actor, now 79, is used to approaching things from unusual angles – it is what he has been doing, forcefully, for most of his career: taking the lessons learned from one area of expertise and applying them to another. So it is that, having just finished appearing nightly on Broadway, opposite Candice Bergen in Love Letters, Alda now has a production up and running at a much smaller venue: the Tabard in west London.

This play, Radiance: The Passion of Marie Curie, explores Alda’s second great enthusiasm: science. It tells the story of Curie’s later years, when the Nobel prize committee tried to prevent her from accepting her prize; and when, after the death of her husband, her affair with another scientist caused a scandal. The woman who discovered polonium and radium, and whose work led to the development of X-rays, is a longtime hero of Alda’s. Over the years, his interest in science has led to him winning two awards from the American Chemical Society, as well as setting up a mission to open up the subject to lay audiences by using the communication skills he learned as an actor.

Facebook Twitter Pinterest ‘Smart people say “I don’t know what that means” all the time’ … Alan Alda. Photograph: Justin Williams/Rex

He runs workshops for doctors and scientists, using improvisation techniques and, above all, his fearlessness about asking “very simple, naive questions based on my ignorance. You realise how much easier it is when somebody says something and you say, ‘I don’t understand’, than it is to guess and fake your way through. I see very smart people say ‘I don’t know what that means’ all the time.”

It is this kind of guileless wisdom that had contributed to Alda’s status as a national treasure in the US – that and the memory of his role as Hawkeye Pierce in the 1970s TV comedy drama MASH, set in a US army hospital in the Korean war. The affection audiences have for him was evident in the box-office returns for Love Letters: when he was brought in halfway through the run, there was a sudden surge in ticket sales. His two memoirs both did well, and he is now at work on another book, this one related to science.

His workshops sell out. The main thing to do, he says, when running improvisations with medical students, is to start with the basics. “The doctor will walk in, not say a word to the patient, and go and wash his hands. And I said, ‘Why didn’t you say hello?’ And he said, ‘Well, we were trained to wash our hands before we do anything else.’ I said, ‘Well, you could say, “I’m going to wash my hands and I’ll be right with you.” Treat them like they’re there.’” Improvisation helps everyone, he says. “It made me more confident with people. It made me trust that if I didn’t know what I was going to say next, something would come.”

Confidence was not something he always had. As a child, Alda’s natural inquisitiveness was crushed by bad teaching. At school, he once asked what he thought was a perfectly reasonable question. As he told the New York Times, when the biology teacher informed the class that crying was a way for the body to get rid of toxins, he asked: “What about the other way – is it good to laugh?” The teacher told him not to be impertinent. “I just felt hurt. I thought, ‘OK, shut up, this is not an environment where you can ask a creative question.’” The one science course he took, chemistry, he failed.

In his mid-20s, however, Alda started reading science journals and came back to the subject. It was an odd reintroduction, which came via an interest in parapsychology. At some point, it struck him that he needed to find out what was true and what was conjecture – and he has been reading about science avidly ever since.

Facebook Twitter Pinterest Alan Alda (right) and Mike Farrell in MASH in 1975 Photograph: Moviestore/Rex

There is not, Alda believes, such a great divide between his hobby and his day job. “I see a lot of connections between science, the way I’ve observed it being done, and actors and writers. There’s a search for something you sense is there and are not sure about. And there’s a rigour to it. The rigour is not so apparent among artists, because it looks like they’re just pulling messages from the blue. But not every colour is just right, not every word or note is useable. They’ve got to be tested in a certain way.” He goes on: “Mathematicians and sometimes physicists prefer proofs that are beautiful. They talk about that all the time, using words like ‘elegant’ and ‘beautiful’. I don’t know if they decide something is true because it’s beautiful – but if it’s true and not beautiful, they don’t like it as much.”

Radiance, which debuted in Los Angeles in 2011, took Alda years to write. Curie wasn’t just the first woman to win a Nobel prize; she was also the first person to win twice. It was the Polish-born scientist’s indefatigable spirit that inspired Alda to keep going. “The press said outrageous things about her – that she was a foreign woman, driven by an infamous desire to have her own way. And the thing they blamed her for was ambition. One hundred years later, that’s what they blamed Hillary Clinton for. The very word – they used that word. A woman can’t appear ambitious. It’s amazing that things haven’t changed that much.”

Provided he can take an afternoon nap, Alda has no problem toiling towards midnight. His schedule for the last week has been typical: a dress rehearsal in New York on Thursday; on Friday morning, shooting a scene for TV crime drama The Blacklist, in which he plays Alan Fitch, assistant director of National Intelligence; then on a plane to Chicago to talk to 2,800 people about communicating science. For all his commitment to the rigours of evidence-based knowledge, sometimes it just comes down to a question of faith. When you’re trying to create something, he says, it often happens when you’re looking the other way. “Your brain is already busy – doing the best it can.”

• Radiance is at the Tabard, London W4, until 28 February. Details: 020-8995 6035, tabardweb.co.uk