The Endless Universe : A Brief Introduction 1 PAUL

نویسنده

  • PAUL J. STEINHARDT
چکیده

HROUGHOUT HUMAN HISTORY, there have been three cosmic paradigms commonly invoked to explain the nature of the universe. Each has been embodied in a modern cosmological model based on Einstein’s general theory of relativity. One is the notion of an Unchanging Universe, which underlies Einstein’s static universe model (the first cosmological model proposed after the introduction of General Relativity) and the Steady State Model of Hoyle, Gold, and Bondi. This paradigm has been set aside because of Hubble’s discovery that the universe is expanding and the discovery by Penzias and Wilson of the cosmic microwave background, direct evidence of an earlier hotter and denser epoch. The paradigm of a Created Universe, in which space and time spring from nothingness and steadily evolve, underlies today’s standard model of cosmology, the big bang/inflationary picture (1–3). Although the creation process and the first instants are not well understood, the sequence of events following is well defined and the predictions of the model appear to be in exquisite agreement with current observations. Finally, we come to the Cyclic Universe, the notion that the universe undergoes periodic epochs of evolution followed by a sequence of events that brings the universe back, phoenix-like, to its initial state. The cyclic concept is at least as old as recorded history. For example,

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تاریخ انتشار 2005