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

“The chief difference between holograms that mirror AdS interiors and those of inflating universes lies in the nature of the extra dimension that pops out. In the former case the emergent direction is a curved dimension of space. It is the interior depth of AdS. In the case of an expanding universe, the time dimension is emergent. That is, history itself is holo-graphically encrypted.”

“However, the later Stephen went further, much further, and took us from imaginary time to no time at all. Exploiting the holographic properties of gravity, we came to envisage the boundary of the disk as a hologram made of entangled qubits from which the interior spacetime-our past history-projects down. Holographic cosmology builds in a top-down view in which the past is in some sense contingent on the present.”

“To get a grip on its quantum origin, the early Stephen, in the 1980s, conceived of the universe in imaginary time. Thinking in imaginary time, all dimensions behave as directions of space, two of which are shown here. The origin of the universe lies at the center of the disk and it expands outward in the radial (imaginary-time) di-rection. The universe today corresponds to the circular boundary.”

“Even though much remains to be learned before we will be able to recount a black hole's history by reading its ashes—the Hawking radiation-many theorists now agree that there is no longer a real paradox. Moreover, I'd argue that this development is something entirely different. Moving from a single spacetime to emergent spacetimes has truly foundational implications.”

“Einstein showed that gravity is a manifestation of warped spacetime. Holography goes further and postulates that warped spacetime is woven from quantum entanglement.”

“entanglement between the inside and the outside of an evaporating black hole can be thought of as generating a wormhole stretching across the horizon. It is as if the particles of Hawking radiation together with their antiparticle partners behind the horizon collectively sew their own space-time bridge, transforming an old black hole from a hermit kingdom into sort of drive-through.”

“Hawking radiation originates in quantum jitters of fields near the horizon of black holes. These jitters give rise to particle-antiparticle pairs. Whenever the antiparticle falls into the black hole, its partner particle can escape into the distant universe, where it shows up as Hawking radiation emitted by the hole...despite their distance the pairs of particles and antiparticles maintain a quantum mechanical link”

“IT WOULD TAKE much more work in Maldacena's holographic laboratory, and the exploration of many more blind alleys, before theorists finally began to discern the escape route out of an old black hole. As a matter of fact, in the years since Stephen's passing, a new generation of black hole physicists, steeped in holography, have realized that perhaps wormholes are involved.”

“"The moment we say that a black hole is described by Schwarzschild's geometry we have an information loss problem," Stephen told his audience in Dublin. "However, information about the exact state is preserved in a different geometry. The confusion and paradox arose because we thought classically, in terms of a single objective spacetime. But Feynman's sum over geometries allows it to be both geometries at once."”

“if determinism, the probabilistic predictability of the universe on the basis of scientific laws, were to break down in the presence of black holes, how could we be sure it doesn't break down in other situations? How could we be sure of our own history, and our memories? "The past tells us who we are" Stephen noted pointedly. "Without it, we lose our identity." ”