A society that pays for science should also understand it. All too often, however, educators, researchers and science communicators fail to explain science in a manner intelligible to the public. And in fast-moving research areas that are touch papers for controversy, such as human embryonic stem cell research or the genetic modification of animals and plants, more effective ways are needed to communicate breakthroughs and their implications to the population at large.

Alan Alda is a comparatively late developer as a science communicator. A native New Yorker, he spent most of his youth dreaming of starring in film and theater. His big break came through his starring role as trauma surgeon Captain Benjamin Franklin 'Hawkeye' Pierce in the 1970s show M*A*S*H, which became one of the most popular series in US television history. Since then, he has risen to national prominence and assembled a total of 32 Emmy award nominations; in 2007, at the age of 71, he had no less than a New York Times best seller and nominations for an Oscar, an Emmy and a Tony.

But Alda has always been much more than an entertainer. And even though his ambitions weren't always channeled to science—that he did not make greater efforts on a summer chemistry course, taken at the behest of his father who hoped the younger Alda might become a physician, remains a source of personal chagrin—his deep, intellectual curiosity has increasingly attracted him to science. Thus, when in 1993, Graham Chedd and John Angier of Boston-based Chedd-Angier-Lewis Production Company sent Alda a letter proposing that he host and narrate the PBS television series Scientific American Frontiers, he jumped at the chance.

I don't think it's a bad idea for scientists to acknowledge the fear of bioengineered foods and then to distinguish among the fears.

For Chedd and his colleague Angier, who are cofounders of the PBS series NOVA, approaching Alda was something of a gamble. “We knew nothing about Alan at that point, except that he was the sort of person we felt would be good to play the role of traditional host of a series like this,” says Chedd. Today, Alda is sympathetic to their angst and says, “They took a big chance on me doing it. But in the process we discovered an unusual way to present scientists' work, which was a very personal way.”

Alda's modus operandi during Frontiers was to coax explanations from researchers so that he could personally understand the science and most especially its importance. “I didn't know the answers to the questions, and that made for a very spontaneous conversation,” he says. “[Researchers] were encouraged to speak to me as a person, and they became more personal. I would really attempt to hear what the person was telling me and then put that together, and then that would lead to the next question.” Having done live theater from the beginnings of his professional life, Alda's ear for dialog is particularly important. “Anytime a scientist goes into lecture mode, I get them out of it by just asking real questions to bring them back, and then listen,” he says.

Nobel Laureate and Rockefeller University president Paul Nurse has hosted Alda as a speaker and guest and shared a speaking platform with him many times. “He should have been a scientist himself,” he says. “Alan pays attention, and he's interested in what science can tell us about the natural world and ourselves—ranging from molecular biology and high energy atomic physics right through to geology and relativity.” For Nurse, the highest tribute he can offer is that Alda is prepared to tackle difficult topics and disciplines. “He doesn't retreat behind the metaphor, which can at times be useful, but you have to be careful about metaphors because you think you understand things when you don't always.”

Alda is a great proselytizer for the potential of science as a provider of solutions for poverty and hunger. He also spends time visiting US universities each year to teach science students how to give presentations. According to Alda, a major aim is not “to dumb down science.” But he also worries about the tendency of scientists at times to talk down to nonexperts. In the field of genetically modified plants and animals, for instance, Alda believes researchers should address people's concerns straight up. “I think it's important to know what their fears are, and to address them, rather than to just say don't worry and just trust the guys in the white coats,” he says. “I don't think it's a bad idea for scientists to acknowledge the fear of bioengineered foods and then to distinguish among the fears.”

At the moment, Alda is working with Chedd on a new three-part PBS series, The Human Spark (http://www.pbs.org/wnet/humanspark/) that will air sometime next year. The show will explore how humans differ as a species from our closest primate relatives. “Alan and I were struck by the fact that a huge number of scientific disciplines seemed to be circling around the question of what makes us human—everything from genetics to artificial intelligence to psychology and cognitive neuroscience,” says Chedd.

Alda has a good idea of what he'd like to see viewers take away from The Human Spark. “When you come out of a museum and step outside, the world has the same colors, but you see colors, shapes and compositions you didn't see before,” he says. “I think you carry that with you and it gives you a little fresher look. It sets your reset button.” “And I think it happened to me as I was talking to these scientists, and I think it may happen for the audience where we see ourselves in a slightly different way.”