When Joe Frazier fought Muhammad Ali, the whole world stopped. It was more important than many Super Bowls. Recent events, such as the World Series, could not remotely touch it for public interest, not only in America, but internationally. However, the whole world did not watch those fights.

How huge were the Ali-Frazier fights in 1971, 1974 and 1975? They were too big for home TV. They were too profitable and exclusive for most people to see. Instead, what was called Theater TV showed their ’71 “Fight of the Century” in 750 locations and grossed $30 million. The whole country cared passionately, but less than 1 percent of the population saw it live.

The vast majority of fans, like me, listened to Ali-Frazier, all three of their fights, on radio. And that primitive form of communication, with the action sometimes only recreated by an announcer — “We have round three now. Ali started quickly, landing several jabs, but Frazier countered in mid-round with a combination that made the champ cover up . . .” only added to the drama, the tension and the importance of the moment.

Neither before, nor since, have I been as tense during a sports event as I always was when Frazier fought Ali — and you knew you wouldn’t be able to see it on home TV (on “Wide World of Sports”), sometimes for weeks. That was the hook for promoters such as Don King. That’s how they could charge Super Bowl ticket prices to watch a TV feed in an auditorium. The “Thrilla in Manila” wasn’t broadcast on national TV until January 11, ’76, though it was fought October 1, ’75. Now that is delayed gratification.

Many paid the theater TV price, but a lot more, like me, didn’t. So, the mass experience of the Ali-Frazier bouts was both unique in its own day and almost forgotten now. In at least one fight, during rounds you heard commercials and second-hand analysis by people who weren’t even there. Then you’d hear, “Okay, folks . . .” or some such transition as the news arrived that “Ali has been knocked down . . .”

And, depending on whom you rooted for — and everybody cared deeply, because Frazier and Ali were symbols of the time on several levels — your heart jumped and you thought, “How badly is he hurt?” It was awful not to know. And it was better, too. The mystery added another layer of tension.

The idea of being reduced to radio or re-creation — in an era when “up close and personal” had arrived and instant replay, slow motion and multiple cameras angles of the NFL were routine — was like being thrown backward in time. It felt almost as retro then as it would today, both frustrating and fascinating. For the most important entertainment event on the planet, we’ll never have anything like that experience again.

You felt like you were no longer living in the ’70s with a man on the moon but, rather, back in the 1930s, like my grandfather listening to Joe Louis on the radio. Except, back then, he got a live, blow-by-blow account. You might as well have been sitting home in Rome waiting for news of how Caesar and the boys were doing on their road trip to Gaul to meet the Goths.

You wouldn’t even see color photos for days until the next Sports Illustrated came out. The most important sports event of the age came to you, for weeks, by word-of-mouth accounts. Oh, to be sure, there was status in having actually seen it live in a theater. Former Post sports editor George Solomon recalls that “everybody” went to see those Ali-Frazier fights; so what if you paid perhaps $50 at venues such as the Washington Hilton with mink coats on display. (Even Frazier wore a mink coat then.)

But the math is simple: Close to 99 percent of the public did not pay up and, like me, waited for “Wide World of Sports” — a five-week delay in ’74.

In the Post sports department, we phone-answering underlings encircled boxing writer Dave Brady on his return to give us the first-hand dope.

We forget the pace at which the times change and, sometimes, the catalysts that provoke progress. Frazier, who died Monday of liver cancer, was far more than Ali’s perfect foil. He was, among other things, one of the two essential characters for a battle so monumental — 26-0 vs. 31-0 in ‘71 — that it changed the way an entire industry thought about potential profits.

That $30 million gross in ’71 opened eyes, then the Frazier-Ali rematch in ’74 was bigger. Yet millions of us felt like radio clowns, our TVs useless to us as we were shut out, or priced out, of the biggest event we could imagine. Capitalism rushed into the vacuum.

The third Ali-Frazier fight in ’75 was the first major satellite feed presented by Home Box Office — back when about four people actually got HBO. TBS flickered to life in ’76, then CNN in ’80. With hindsight, the big theater grosses for the first two Frazier-Ali classics documented the scale of profit potential and influenced the shape and pace of the arrival of cable TV.

In a way, limited and expensive access probably helped to make the Frazier-Ali trilogy more thrilling and mysterious. Our imaginations and our hearts were engaged even as our eyes were shut out. Waiting, sometimes weeks, to see the real thing only made it seem more important.

For several years, I was The Post’s local fight writer, in the D.C. Armory where the winner’s purse wouldn’t cover the dental bills. Eventually, I covered Sugar Ray Leonard and others. Frazier was often around on the big fight nights. Whether joking, telling a story or turning bitter at times, he had the imperial certainty in his bearing of the rare champion who knows that he will never be forgotten. No account of boxing can ever leave him out.

But, every time, I was stunned at how normal Frazier looked, almost small. Smokin’ Joe, a giant in my mind, was so much bigger on the radio.