With ratings-challenged NBC struggling to find its feet as the broadcast network world shifts and rolls beneath it, and with broadcast television itself being regularly lamented as having one foot in the grave and the other on slippery ground, one might be tempted to think the Peacock might as well fold its tail feathers for good.

But there is a center of gravity to the NBC universe, and it is every weeknight, right after your local news – “The Tonight Show.” On Monday, that center shifts from its longtime home in Los Angeles (aka “beautiful downtown Burbank”) to its ancestral home of New York, where it launched with host Steve Allen in 1954.

After the departure of host Jay Leno (again) following a 22-year run – briefly interrupted by a failed experiment with Conan O’Brien in 2009-10 – “The Tonight Show Starring Jimmy Fallon” makes its debut from Studio 6B at 30 Rockefeller Plaza in Manhattan.

NBC is hoping that injecting new blood into its most venerable franchise will help the network get its mojo back. It might even be counting on a friendly ghost or two.

Studio 6B is same space where Jack Paar was host of “The Tonight Show” from 1957 to ’62, and where Johnny Carson did the first third of his run, from 1962 to ’72 (he stayed until 1992, when Leno came in). Lorne Michaels of “Saturday Night Live” fame comes in as executive producer of the new iteration, with Josh Lieb as producer.

“There’s that great feeling,” said Lieb, “of bringing it back to where the show came from, to the studio where Paar and Carson were. It gives us a little more impetus to feel like we have something to live up to. In a good way, the halls echo with the legends.”

With Seth Meyers replacing him as host of the “Tonight” companion show, “Late Night,” the 39-year-old Fallon, a new father of a 7-month-old daughter, brings his house band, the Roots and announcer Steve Higgins, along with his skills as a comic, an interviewer and a song-and-dance man.

“In a way,” said Lieb, “it’s the closest thing to a real variety show that’s on TV today.”

Speaking to assembled TV reporters in Pasadena, Calif., in January, Fallon pointed out that he was happy in his later-night slot and made the point of telling Leno.

“After the whole Conan-Jay thing went down,” he said, “I was following Jay. He was back at 11:30. I called up Jay, and I said, ‘Hey, I just want to let you know that I’m not gunning for your position at all. I’m very happy at 12:30, 7:00 a.m., wherever they put me on. I’m just not gunning for this. I’m very happy here.’

“So he goes, ‘I appreciate that.’ I said, ‘And when eventually you decide to step down, let’s do it the right way.’ And he said, ‘Yeah, of course.’ You just felt it was different from then on.

“We talk to each other every couple weeks, always giving me advice, all the way up till now. He called me and said, ‘I think this is going to be the year.’ And I said, ‘All right.’ And he goes, ‘I’d love for you to be the next guy. I think you’re going to be great.’ ”

The logo for the revamped “Tonight Show” features a full moon, but that’s not the only iconic nighttime symbol that was in Fallon’s mind.

“Why not bring it back to New York?” he said. “What’s going to happen? What’s the worst that can happen? It’s just a beautiful city. I think of New York, I think of nighttime. I just think it’s the perfect place, where it should be.

Announced guests for the first show are Will Smith and U2.