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Altre immaginiEditore: The American Physical Society], [Brookhaven, NY, 1983
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Aggiungi al carrelloFirst edition. HAWKING'S NO-BOUNDARY PROPOSAL: HOW THE UNIVERSE COULD HAVE ARISEN FROM NOTHING. First edition, very rare offprint, and Hawking's own file copy, of this famous paper describing the 'no-boundary proposal' for the origin of the universe. "Stephen sought to understand the whole universe in scientific terms. As he sai…d famously, 'My goal is simple. It is a complete understanding of the universe' . From 1982 onwards, Stephen concentrated his efforts on the deeper puzzle of the boundary conditions required to bring about inflation and the probability of them coming about . The singularity theorems proved by Stephen, Penrose and others showed conclusively that the classical Einstein equation implied that the universe began in a hot Big Bang. But the singularity theorems also showed that the beginning could not be described by a classical space-time geometry obeying the Einstein equation with three space directions and one time direction at each point. Rather, they showed something more sweeping: the classical Einstein equation breaks down at the Big Bang and, along with that, the notion that it could be described by a classical space-time . [it was therefore necessary to try] to describe the quantum birth of the universe. Stephen first put forward a proposal along these lines at a conference in the Vatican in 1981, where he suggested that the universe began with a regular Euclidean geometry having four space dimensions which made a quantum transition to a Lorentzian geometry with three space dimensions and one time dimension that we have today. To put this idea on a solid footing required a quantum state-a wave function of the universe" (Carr et al.). "'Murray Gell-Mann used to ask me,' Hartle said, referring to the late Nobel Prize-winning physicist, 'if you know the wave function of the universe, why aren't you rich?'" (Wachover). "Because one is using Euclidean space-times, in which the time direction is on the same footing as directions in space, it is possible for space-time to be finite in extent and yet to have no singularities that formed a boundary or edge. Space-time would be like the surface of the earth, only with two more dimensions . the quantum theory of gravity has opened up a new possibility, in which there would be no boundary to space-time and so there would be no need to specify the behavior at the boundary. There would be no singularities at which the laws of science broke down, and no edge of space-time at which one would have to appeal to God or some new law to set the boundary conditions for space-time. One could say: 'The boundary condition of the universe is that it has no boundary.' The universe would be completely self-contained and not affected by anything outside itself. It would neither be created nor destroyed, it would just BE" (Hawking). "The scientific importance of the no-boundary proposal is not just as a successful theory of the origin of the basic structure of the universe-it has also had a significant effect on how we think about the universe and our place in it" (Carr et al.). We are not aware of any other copy of this offprint having appeared on the market. Provenance: the estate of Professor Stephen Hawking (1942-2018). "In 1981, many of the world's leading cosmologists gathered at the Pontifical Academy of Sciences, a vestige of the coupled lineages of science and theology located in an elegant villa in the gardens of the Vatican. Stephen Hawking chose the august setting to present what he would later regard as his most important idea: a proposal about how the universe could have arisen from nothing" (Wachover). At that time the standard theory of the origin of the universe was the 'Big Bang' model. This had apparently been confirmed by the discovery of the cosmic microwave background by Arno Penzias and Robert Wilson in 1965. But the Big Bang theory had some problems. Not only was there the question of what happened before the Big Bang, but the theory predicted a universe that was not nearly as smooth and uniform as ours. In 1980, the cosmologist Alan Guth realized that the Big Bang's problems could be fixed with an add-on: an initial, exponentially fast expansion known as cosmic inflation lasting some 10-33 seconds, which would have rendered the universe smooth and flat before expansion resumed at a slower rate allowing gravity to create the relatively few inhomogeneities we see in the current universe. Inflation quickly became the leading theory of our cosmic origins. Yet problems remained: inflation requires extremely specific initial conditions, and the question becomes, why were the initial conditions just those required to make the expansion theory work? In his Vatican lecture, "Hawking proposed a solution to the problem of initial conditions: there is no beginning at all. According to the record of the Vatican conference, the Cambridge physicist, then 39 and still able to speak with his own voice, told the crowd, "There ought to be something very special about the boundary conditions of the universe, and what can be more special than the condition that there is no boundary?" "The 'no-boundary proposal,' which Hawking and his frequent collaborator, James Hartle, fully formulated in a 1983 paper [offered here], envisions the cosmos having the shape of a shuttlecock. Just as a shuttlecock has a diameter of zero at its bottommost point and gradually widens on the way up, the universe, according to the no-boundary proposal, smoothly expanded from a point of zero size. Hartle and Hawking derived a formula describing the whole shuttlecock - the so-called 'wave function of the universe' that encompasses the entire past, present and future at once - making moot all contemplation of seeds of creation, a creator, or any transition from a time before. 'Asking what came before the Big Bang is meaningless, according to the no-boundary proposal, because there is no notion of time available to refer to,' Hawking said in another lecture at the Pontifical Acade.
