James Isaiah Gabbe films his exploration of China, “Journey with the Giant.” The film is to be screened Wednesday in Cambridge.

After publishing his definitive look at New York’s Union Square in 2010, James Isaiah Gabbe found a bigger subject for his next work: China. All 3.7 million square miles and 1.4 billion people in it.

The film he got out of his studies and travels, “Journey with the Giant,” comes to Cambridge on Wednesday with the filmmaker for a screening and Q&A session.

“Just 30 years ago, China was a third-world Communist dictatorship trapped in economic, political and social blight. Today, the last remaining major communist state, China is the world’s second-largest economy,” Gabbe says. “In a few years, it’s expected to be the largest economy on earth, dwarfing Great Britain, India, Japan and Russia – combined. For the first time in over a century, the U.S. will not be the world’s most powerful nation.”

To explore these issues, Gabbe needed to figure out an approach. Most journalists wouldn’t try this type of documentary, he has said, because they would need permission from the government. But Gabbe, a 1966 alum of Northeastern University, had an advantage: gabbegroup, a public relations and marketing firm he founded in 1980, has an affiliate office in Shanghai, and his knowledge of the the country allowed him to travel and film in 20 locations around the sprawling country under the radar – as a tourist.

From the March premiere of the film at Northeastern:

“Journey with the Giant” enters the daily life of factory workers, teachers, merchants, tourists, clerics and the like, showing the extraordinary scope of change in that vast country and revealing how the Chinese feel about their frenetic new world and the communist party’s autocratic leadership.

The film, which Gabbe calls “an intimate, unvarnished, unsanctioned exploration,” aims to look at China’s growing economic and technological dominance.

“Within the lifetime of most Americans, Pax Americana may only be remembered as a brief interlude, and China could well be the center of our universe,” Gabbe says. “Americans had better pay very close attention … the implications are unprecedented.”

The screening and conversation with Gabbe starts at 6 p.m. Wednesday at the Cambridge Main Library, 449 Broadway.