Flickr Famed theoretical physicist Stephen Hawking passed away in March of this year, but his final theory about the Universe has been published today. The study, published in conjunction with former student and frequent collaborator Thomas Hertog, addresses the conflict that arise between quantum mechanics and Einstein’s general relativity theory. From EarthSky.org: Hawking and Hertog’s latest study deals specifically with a subset of Big Bang theory, called eternal inflation. Most modern Big Bang theories incorporate the idea of an inflation, which calls for an exponential expansion of space in the universe’s first fraction of a second. Eternal inflation suggests that some pockets of space keep expanding exponentially forever, while some (like the one we inhabit) don’t.
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Stephen Hawking at NASA - Wikipedia If this theory is an accurate description of the cosmos, then we live in a multiverse consisting of many isolated bubble universes. If it’s true, then our entire known cosmos of galaxies and stars exists inside a sort of bubble, but many other bubbles – forever unknowable – exist outside ours. Some might have laws of physics similar to (or even the same as) ours. Some would operate very differently. The University of Cambridge issued a statement about Hawking’s final study this week. It explained: “The observable part of our universe would then be just a hospitable pocket universe, a region in which inflation has ended and stars and galaxies formed.” Hawking said in one of his last interviews: “The usual theory of eternal inflation predicts that globally our universe is like an infinite fractal, with a mosaic of different pocket universes, separated by an inflating ocean. The local laws of physics and chemistry can differ from one pocket universe to another, which together would form a multiverse. 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.” And indeed, in their new study, Hawking and Hertog say this account of eternal inflation as a theory of the Big Bang is wrong. Hertog said: “We predict that our universe, on the largest scales, is reasonably smooth and globally finite. So it is not a fractal structure.” IFLScience talks about the holographic principle that the physicists used to explain the Universe without relying on Einstein’s relativity theory: Hawking and Hertog approached eternal inflation in a different way. They used string theory, one of the potential ways to reconcile relativity and quantum physics, and they used the holographic principle as well. This states that all the information of our 3D universe can be encoded on a 2D sphere at its boundary. Armed with those, the scientists were able to tweak eternal inflation, turning it into a timeless state, which creates a small range of possible universes with no complicated fractal multiverse. And on top of that, it might be testable. The most interesting thing about this latest study, however, might be its departure from the theorists’ earlier conclusions. Again, from EarthSky: The new study harks back to Hawking’s earlier no boundary theory, which predicted that – if you go back in time to the beginning of the universe – the universe shrinks and closes off like a sphere. The new study is a step away from the earlier work, Hertog explained, and he said: “Now we’re saying that there is a boundary in our past.” What do you think? Are we living in the only Universe there is or are there multi-verses? Here’s Thomas Hertog explaining more: