> According to Hawking's "no-boundary proposal," before the Big Bang, when the entire universe was compressed into a single, infinitely small point, there was no directional time as we experience it. Time was a closed, boundary-free thing, like a sphere without edges. ...
> Scientists later determined that this proposal implied something strange: that the multiverse is infinite, with endless, uncountable parallel universes existing alongside our own....
This is the first time I'd heard of that proposal. It rings true to me (I know—naturalness is another word for the truthiness fallacy) in the sense that the outer reality needs to transcend time and therefore—if our universe is time-bound—contain infinite time-bound sub-universes whose origination and final fate are not externally bound by time. Or perhaps the "no-boundary proposal" is just a succinct way of saying that!
> That wild situation presented a number of problems for science, most significantly that it rendered most basic scientific ideas about the multiverse impossible to test. ...
> "Hawking was not satisfied with this state of affairs," Hertog told Live Science in March. "'Let's try to tame the multiverse,' he told me a year ago. So, we set out to develop a method to transform the idea of a multiverse into a coherent, testable scientific framework."
This reminds me of Einstein's discomfort with true unpredictability—"God does not play dice"—how he helped lay the foundations for quantum mechanics but never fully accepted it himself because it was too weird (as I understand it—I'm a rather poor historian).
> Hawking's final paper suggests a framework for understanding the universe that would render the multiverse finite, countable and subject to meaningfully engagement via the tools of science.