Weeks after his death, physicist Stephen Hawking has delivered his last thoughts about the nature of the cosmos, and he says it may be simpler than often believed.
Well, simpler if you understand theoretical physics, anyway. It remains incomprehensible for the rest of us.
A paper that outlines his view, written with Thomas Hertog of the University of Leuven in Belgium before Hawking's death in March, has been published by the Journal of High Energy Physics. Hertog had announced the new theory last year at a conference celebrating Hawking's 75th birthday.
The University of Cambridge, where Hawking worked, announced the publication on Wednesday.
Here's a very simplified version of what it says. First, some background.
Scientists believe our universe sprang into existence with the Big Bang, followed by an unimaginably rapid expansion known as inflation. Within our observable universe, inflation ended long ago.
But some ideas of inflation say it never stops, persisting in other regions of the cosmos forever. This eternal inflation produces a "multiverse," a collection of pocket universes of which our own universe is just one.
There may be an infinite number of these pocket universes. If they're all very different, then how typical is the universe we live in, where scientists make their observations?
That's a key question for understanding the fundamental laws of nature, and finding a way to estimate what types of universes are probable is a big challenge, said physics professor David Kaiser of the Massachusetts Institute of Technology.
Many people have tried to tackle that question, but Hawking approached it from a point of view shaped by his long study of the intersection of quantum theory and gravity, he said.
Hawking's paper suggests that there may be a much smaller range of possibilities for universe types than previous estimates had suggested. So "the behavior of our own, observable universe might not be a rare outlier, but perhaps (be) relatively typical," Kaiser said in an email.
"Naturally," Kaiser said, "this is all rather speculative."
Avi Loeb of the Harvard-Smithsonian Center for Astrophysics called it "a stimulating, but not revolutionary paper."