Noah Wylie Noah Wylie

Noah Wyle, the star of Steven Spielberg's new TNT alien-invasion series, Falling Skies, is still intimidated by his boss.

"I couldn't say a word," Wyle says of meeting the three-time Academy Award-winning director. "My hands were sweaty. Luckily, he kind of ignored me. In fact he totally ignored me. I still am incredibly intimidated to be around him, to be honest."

VIDEO: First trailer for Steven Spielberg's Falling Skies

Spielberg — who has helmed such films as Schindler's List, E.T., Jaws, Jurassic Park and War of the Worlds — also helped launch the NBC series ER, which skyrocketed Wyle's career.

Since Wyle left ER in 2005, he has appeared in such films as Nothing But the Truth and W, as well as TNT's action-adventure TV movie franchise, The Librarian. Now the 39-year-old actor will get even more physical in Skies, which centers on the aftermath of an alien invasion. 

"This was the most physically demanding work I've ever done in my life," Wyle says. "[ER] had an element of politics and had an emotional element to it, but didn't really have an element of physicality to it like [Falling Skies]. So I thought it was a good challenge as I enter my 40th year. The clock is ticking on how long I can do this sort of thing."

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Besides the physical stunts, the hardest aspect of Falling Skies is keeping the story somewhat believable, Wyle says. "I've never really done anything remotely near the science-fiction drama, so there's a learning curve to it," he says. "The element of specificity and detail has to be so closely paid attention to. As soon as you unravel that line of plausibility, once you part from this being a true 'What if?' scenario, it's like a house of cards that comes tumbling down."

Falling Skies will debut this summer on TNT.