Before he passed away in March, renowned physicist Stephen Hawking had published more than 230 articles on the birth of the universe, black holes and quantum mechanics. But, ten days before his death, Hawking finished his final theory on the origin of the universe  – now published posthumously – and it offers an interesting departure from earlier ideas about the nature of the “multiverse.”

As PBS reports, the new report, co-authored by Belgian physicist Thomas Hertog, counters the longstanding idea that the universe will expand for eternity.

If you asked an astrophysicist today to describe what happened after the Big Bang, he would likely start with the concept of “cosmic inflation.” Cosmic inflation argues that right after the Big Bang — we’re talking after a teeny fraction of a second — the universe expanded at breakneck speed like dough in an oven.

But this exponential expansion should create, due to quantum mechanics, regions where the universe continues to grow forever and regions where that growth stalls. The result would be a multiverse, a collection of bubblelike pockets, each defined by its own laws of physics.

“The local laws of physics and chemistry can differ from one pocket universe to another, which together would form a multiverse,” Hertog said in a statement. “But I have never been a fan of the multiverse. If the scale of different universes in the multiverse is large or infinite the theory can’t be tested.”

Along with being difficult to support, the multiverse theory, which was co-developed by Hawking in 1983, doesn’t jibe with classical physics, namely the contributions of Einstein’s theory of general relativity as they relate to the structure and dynamics of the universe.

“As a consequence, Einstein’s theory breaks down in eternal inflation,” Hertog said.

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