Just forty years ago, the first human being ventured off the planet. In the intervening decades, humans have refined the art of surviving in space. We can simulate an atmosphere, recycle water and freeze dry food. But so far we lack the know-how to fake gravity, the constant pull of our home planet on our bones, our blood and our brain.

In "I was a Spaceman," Alan Alda meets with Dr. Jerry M. Linenger, a NASA astronaut who, in 1997, spent five months aboard the Russian space station Mir. Two hundred miles above the Earth, Linenger found himself battling fire, radiation and a fear of falling into the great void of space.

Linenger undergoes pre-flight training in Russia

Each day of his voyage, he became a bit more of a "spaceman," and increasingly adapted to weightlessness. But his body paid a price. Upon returning to Earth, he found he'd lost 13 percent of his bone mass -- tantamount to a pretty serious case of osteoporosis. Yet in spite of everything, for Linenger his months off the planet formed a profound and life-changing experience.

In "The Frontiers Profile," Linenger recounts these adventures and more to Alan Alda as they talk about life aboard Mir.

For more on this topic, see the web feature:
Life at Zero G