Today’s cosmologists have a tougher task, because the universe as we now know it isn’t ageless and unmoving: They have to explain the emergence of time’s arrow within a dynamic, relativistic universe that apparently began some 14 billion years ago in the fiery conflagration of the big bang. More often than not the explanation involves ‘fine-tuning’—the careful and arbitrary tweaking of a theory’s parameters to accord with observations.
Tentative new work from Julian Barbour of the University of Oxford, Tim Koslowski of the University of New Brunswick and Flavio Mercati of the Perimeter Institute for Theoretical Physics suggests that perhaps the arrow of time doesn’t really require a fine-tuned, low-entropy initial state at all but is instead the inevitable product of the fundamental laws of physics. Barbour and his colleagues argue that it is gravity, rather than thermodynamics, that draws the bowstring to let time’s arrow fly. Their findings were published in October in Physical Review Letters. (Identification of a Gravitational Arrow of Time 29/10/2014)
The team’s conclusions come from studying an exceedingly simple proxy for our universe, a computer simulation of 1,000 pointlike particles interacting under the influence of Newtonian gravity. They investigated the dynamic behavior of the system using a measure of its "complexity," which corresponds to the ratio of the distance between the system’s closest pair of particles and the distance between the most widely separated particle pair. The system’s complexity is at its lowest when all the particles come together in a densely packed cloud, a state of minimum size and maximum uniformity roughly analogous to the big bang. The team’s analysis showed that essentially every configuration of particles, regardless of their number and scale, would evolve into this low-complexity state. Thus, the sheer force of gravity sets the stage for the system’s expansion and the origin of time’s arrow, all without any delicate fine-tuning to first establish a low-entropy initial condition.
από το www.scientificamerican.com 8/12/2014
σχετικά:
DOES TIME EXIST? Perimeter Institute, Waterloo, June 6,2014
to Julian Barbour’s web site www.platonia.com
"The time-without-time foundation of classical physics entails a relatively small adjustment to our conceptions, but is likely to have a profound effect in a quantum theory of the universe. This is because significant parts of classical physics, above all time, are carried over unchanged into quantum theory. If our ideas about time in classical physics are wrong, surprises can be expected in a quantum theory of the universe. As of now, little can be said about this with certainty because no such theory yet exists. The very idea could even be wrong. Nevertheless, candidate theories have been proposed. The one I favour seems initially impossible: the quantum universe is static. Nothing happens; there is being but no becoming. The flow of time and motion are illusions."
από το J. Barbour's "THE NATURE OF TIME"
Tentative new work from Julian Barbour of the University of Oxford, Tim Koslowski of the University of New Brunswick and Flavio Mercati of the Perimeter Institute for Theoretical Physics suggests that perhaps the arrow of time doesn’t really require a fine-tuned, low-entropy initial state at all but is instead the inevitable product of the fundamental laws of physics. Barbour and his colleagues argue that it is gravity, rather than thermodynamics, that draws the bowstring to let time’s arrow fly. Their findings were published in October in Physical Review Letters. (Identification of a Gravitational Arrow of Time 29/10/2014)
The team’s conclusions come from studying an exceedingly simple proxy for our universe, a computer simulation of 1,000 pointlike particles interacting under the influence of Newtonian gravity. They investigated the dynamic behavior of the system using a measure of its "complexity," which corresponds to the ratio of the distance between the system’s closest pair of particles and the distance between the most widely separated particle pair. The system’s complexity is at its lowest when all the particles come together in a densely packed cloud, a state of minimum size and maximum uniformity roughly analogous to the big bang. The team’s analysis showed that essentially every configuration of particles, regardless of their number and scale, would evolve into this low-complexity state. Thus, the sheer force of gravity sets the stage for the system’s expansion and the origin of time’s arrow, all without any delicate fine-tuning to first establish a low-entropy initial condition.από το www.scientificamerican.com 8/12/2014
σχετικά:
DOES TIME EXIST? Perimeter Institute, Waterloo, June 6,2014
to Julian Barbour’s web site www.platonia.com
"The time-without-time foundation of classical physics entails a relatively small adjustment to our conceptions, but is likely to have a profound effect in a quantum theory of the universe. This is because significant parts of classical physics, above all time, are carried over unchanged into quantum theory. If our ideas about time in classical physics are wrong, surprises can be expected in a quantum theory of the universe. As of now, little can be said about this with certainty because no such theory yet exists. The very idea could even be wrong. Nevertheless, candidate theories have been proposed. The one I favour seems initially impossible: the quantum universe is static. Nothing happens; there is being but no becoming. The flow of time and motion are illusions."
από το J. Barbour's "THE NATURE OF TIME"
και στη γλώσσα μου να ήταν δημοσιευμένο θα δισκολευόμουν να το παρακολουθήσω,
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