Raise your hand if you are aware that Don Imus is retiring this week after 50 years on the radio.

It is possible many of you had not heard this. I did not hear about it until I received a press release from CBS News some time last week in advance of this past weekend’s edition of “CBS Sunday Morning.”

The news release announced that Imus would be seen on the show in a farewell interview conducted by Anthony Mason. And so he was. You can watch the segment here.

Imus’ decision to retire did make news for a day or so back in January, following a tweet from his radio show. But like so many media milestones today, the news did not seem to resonate or spread, or even sustain itself for more than a 24-hour (or less) news cycle.

There was a time when the concept of a world without Don Imus on the radio was unthinkable. This week, that world suddenly becomes very thinkable. Imus is scheduled to have his last broadcast Thursday morning (March 29). After that, “Imus in the Morning” will be no more.

His retirement has more to do with the aging process than the relative strength or popularity of his radio show today. As noted in the “Sunday Morning” piece, Imus is 77 and battling emphysema.

He seemed exhausted, but he has long seemed that way. Given the lifestyle he maintained for many years, not to mention the early hours of a job that required him to talk for four or more hours every day, it is surprising that Don Imus lasted this long.

All those years in the public arena, airing his opinions on every subject and issue known to mankind for five decades, must have been exhausting.

Most of Imus’ 50 years on the radio unfolded in the era before the Internet changed and flattened all media. A guy like Imus, heard on more than a hundred radio stations every morning, held enormous power — or so it seemed at the time.

In the “CBS Sunday Morning” piece, a 1997 cover of Time magazine was shown featuring “The Most Influential People in America.” Imus was one of them. So were Rosie O’Donnell, Tiger Woods, Madeleine Albright and “Dilbert” cartoonist Scott Adams.

Was there really a time when Rosie O’Donnell and “Dilbert” were influential? Apparently, there was. Time magazine was influential too in 1997, but not anymore.

In the era before the Internet, personalities seemed bigger. Restricted only to the “big” media prevalent at the time — TV, radio, newspapers and national magazines — the pool of so-called “influencers” (a term coined in the Internet era, not before it) was smaller.

Since there were fewer of them, and the circulation of their media platforms (viewership, readership, listenership) was so much higher than any comparable media today, their influence was more acutely felt.

Who has such influence today? Rachel Maddow? Sean Hannity? Maybe they have some, but their audiences are much smaller. And their viewership is made up of people who already agree with them. They are preaching to niche choirs.

Except for the national, communal experience of watching the Super Bowl on a winter Sunday, there is no mass media anymore — at least not in the way we once understood the term.

Media personalities such as Don Imus were lucky to work in the era they worked in. Everybody knew who they were. For better or worse, their most outrageous utterances made news because people — a mass amount of them — cared about what they said.

Media personalities today will never know the joys of mass popularity of the kind enjoyed by Imus and his radio peers — a short list that includes Rush Limbaugh and Howard Stern.

Those of us old enough to remember Imus and his era should thank him for a job well done. There will never be another one like him.