We live in an expanding universe. So do the Avengers, X-Men and Fantastic Four — until May, that is, when that will change.

In a recent news conference at Midtown Comics in New York City, Marvel Comics officials decreed the end of not only the Marvel Comics Universe, which has been building on itself in a more-or-less linear fashion since the early 1960s, but also of the "Ultimate Universe," an alternate dimension Marvel has been exploring since 2000 in books like "Ultimate Spider-Man" (currently starring a black/Hispanic kid named Miles Morales) and "The Ultimates" (a warped mirror version of the Avengers).

The plan, Editor-in-Chief Axel Alonso said, is that the two universes will "slap together" in a book called "Secret Wars." No, not the "Secret Wars" of 1984 or the "Secret Wars II" of 1985, which were born of a toy line. Nor is it the "Secret War" of 2004, which is a different animal altogether.

This "Secret Wars," according to Alonso, is the "endcap" of the Marvel Universe launched by Stan Lee and Jack Kirby 54 years ago in "Fantastic Four" No 1. And whatever comes after will be different.

The mechanism for doing this has been an ongoing story line in the flagship Avengers titles for the past year or so. Here's the plot:

Somewhere in the multiverse, the Avengers learned in 2013, something had gone awry in the barriers between dimensions. So now an infinite number of universes are plowing into ours, one by one, always with the Earths of each universe the breach point. So the Avengers have been struggling for a way to stop these "incursions," as they are called. But all they've managed to do so far is survive — by destroying each invading Earth. That's not very heroic, but it does reset the clock for the next incursion, by which time, the heroes hope, they will find a way to change the rules.

It turns out, according to Marvel Executive Editor Tom Brevoort, "they won't." In "Secret Wars" No. 1 in May, the Ultimate Universe is the one invading, and the heroes of both worlds fail to stop the collision. At which point, most Marvel titles will be canceled, because Marvel Earth will be no more. Instead, what we have left is Battleworld.

"Battleworld, essentially, is the detritus that's left over after the destruction of the Marvel Universe and the Ultimate Universe," Brevoort said. "And it is the little melting pot in which the new Marvel Universe will be created, will be fermented. All the little bits and pieces and dribs and drabs, all the little sections of Earths that were within those incursion zones, all those little areas where it has intersected, all those little areas have remained and will be fused into a single, gigantic organism, which is Battleworld. In which various characters will live their lives and contend with this new situation and will set up all of the building blocks and all of the bedrock of what the new Marvel Universe will be from that point going forward."

To create this new Earth, Marvel has mined its rich history and used famous story lines from its past. For example, a 1992 Hulk story called "Future Imperfect" imagined a future world where an ancient Hulk called the Maestro ruled a nuclear-irradiated world with an iron fist. That is represented by a tract of land on Battleworld called "Dystopia." The two Iron Man stories called "Armor Wars," in which Tony Stark flew around the world illegally destroying his technology wherever it was being used by bad guys, is represented by "Technopolis." And so forth.

"Secret Wars" will run eight issues, but with the old Marvel Universe gone, what else will Marvel publish? A lot, as it turns out, in three umbrella categories:

Last Days: Books with this trade dress will focus on what certain characters — some of whom will probably not survive the transition — do in the last eight hours before the end of the world.

Battleworld: These books are a macro look at the new reality, with stories covering how the zones deal with one another.

Warzones: These books will be smaller, human-level stories about individual characters or opponents.

Of course, with the popularity of the Marvel movies, one must wonder why they're rocking the boat. Why do all this? And the answer is the same one it always is: To sell a lot of comic books. But what about the movies and TV shows? Will they change to reflect this new reality?

The only answers are to be found by reading the comics themselves, beginning with "Secret Wars" No. 0, a prologue that will be one of Marvel's offerings on Free Comic Book Day 2015 (May 2). After that, both "Secret Wars" Nos. 1 and 2 ship the same month.