Al Owski’s Reviews > On the Origin of Time: Stephen Hawking's Final Theory > Status Update

“observership in quantum cosmology isn't a mere afterthought or an anthropic post-selection principle acting in a giant preexisting multiverse, but an agency operating at a deeper level, an indispensable part of the continual process through which physical reality—and physical theory, we argue—come about.”

“The universe we see around us, this branch of reality, is the collective result of innumerable such environmental acts of observation. Having registered and built upon countless chance outcomes, over a period of billions of years, each contributing a few bits of information to our branch of history, this is how the world around us has acquired its specificity.”

“AT THE LEVEL of experience...every act of observing amounts to some sort of pruning of the branching tree of possible futures. A measurement situation in quantum theory is like a fork in the road, where history divides into two or more separate branches. In the experience of any given ob-server, at such branching points, only one of the branches survives. More precisely, on each branch, only that branch survives.”

“de Finetti in 1974 wrote: "My thesis… is...probability does not exist… only subjective probabilities exist, the degree of belief in the occurrence of an event attributed by a given person at a given instant and with a given set of information."…Throughout our lives, most of us gain confidence in subjective probabilities because we find that results we deem likely happen often, and those that we don't happen rarely.”

“Everett's framework, in which probabilities wiggle their way into quantum theory in a more subtle…way, much like the way probability enters our thinking in day-to-day life. Whether we ponder the weather, the lottery, or the shape of the next gravitational wave passing through planet Earth, we all use subjective probabilities all the time to quantify our uncertainty in situations where we have incomplete knowledge.”

“Everett himself said he sought somehow to bridge the positions of Einstein and Bohr. He claimed their differences were a matter of perspective and described his scheme as "objectively deterministic, with probability appearing at the subjective level." This is an interesting point. In the early Copenhagen formulation of quantum mechanics, probabilities were axiomatic and fundamental.”

“Everett pulled down Bohr's wall separating the quantum microworld from the classical macroworld. His key idea was to take the math behind quantum mechanics seriously and to apply it to everything. Suppose there is no collapse, he suggested, but only a single universal wave function that includes observers and everything else, evolving gently and smoothly...”

“Niels Bohr, on the other hand, who had a background in philosophy as well as mathematics, had a profound intuition that quantum mechanics was consistent. Bohr took seriously the central tenet of quantum mechanics that observership—the very questions we ask of nature—affects how nature manifests itself. "No phenomenon is a real phenomenon until it is an observed phenomenon," he held.”

“To Einstein, the probabilistic nature of quantum mechanics signaled that the theory was incomplete, that there had to be a deeper-lying framework that permitted an objectively real description of physical reality, regardless of any acts of observation. "The [quantum] theory produces a good deal but hardly brings us closer to the secret of the Old One," he wrote to Bohr. "I am convinced...He does not play dice"”

“[Stephen:] The history of the universe depends on the question you ask. Good night.”