From: Earl Wajenberg <[EMAIL PROTECTED]> Date: Mon, 29 Apr 2002 10:26:44 -0500 To: Discussions <[EMAIL PROTECTED]> Subject: The Pulsating Universe Again (and again, and...)
Before the big bang Copyright (C) 2002 Scripps Howard News Service Science Magazine Sacramento Bee By EDIE LAU, Sacramento Bee (April 27, 2002 11:06 a.m. EDT) - If the universe was created by a big bang, which is the prevailing view of science, what happened before that? And how will it all end? These nagging questions are not addressed by the big-bang theory, but now there's a model of the universe that offers an answer. It goes like this: The universe expands and pauses, expands and pauses endlessly, so that time neither begins nor ends. "It gets rid of the problem of explaining a creation. ... The universe has been around forever," said Paul Steinhardt, a Princeton University astrophysicist, who, with Neil Turok at Cambridge University, proposes a cyclic universe model in a paper published online Friday by the journal Science. Using exotic concepts in modern physics, the ambitious model liberally rearranges certain ideas in big-bang theory. One implication is that the bang wasn't all that big. The cyclic model says, for example, that galaxies formed out of forces that existed before the bang. For a culture such as ours, which marks history by linear time - past, present and future - the idea of timeless time is mind-bending. But as Steinhardt noted, other cultures, notably the ancient Hindus, saw the universe as cyclic. Western astrophysicists in the 1930s put forth similar "oscillatory" models of the universe. The model described Friday recycles some old ideas and incorporates new concepts, including the notion of the universe having extra dimensions. "I think it will make a splash," said Daniel Cebra, an experimental physicist at the University of California-Davis, involved in a project reconstructing the first moments after the presumed big bang. "Steinhardt is a big name in this field, so what he says people listen to pretty seriously." Andreas Albrecht, a UC Davis cosmologist, said the idea needs more development to be persuasive, but called it "very stimulating and fun." Stimulating more thinking on the fundamental form of the universe was the reason Steinhardt began scouting for a new model. In earlier years, Steinhardt - along with Albrecht and others - developed a piece of the standard model of the universe known as inflation. Inflation theory says that a period of extremely fast expansion followed the cosmic boom that gave rise to the universe. Inflation then gave way to more sedate growth, the era we're thought to be in today. "One way of exploring my confidence in the (inflation) model is (seeing) whether or not we can come up with something else," Steinhardt said. "We decided to see ... just how far we could get. I'm as surprised as anyone just how far we have gone." Described very simply, the cyclic model works this way: The big bang is not the start of time, but rather, a bridge to an earlier era of contraction. Coming after is the usual formation of matter and radiation. The slow expansion lasts trillions of years. Eventually, the matter and radiation are so diluted that the universe becomes virtually empty. The expansion ends. During this period of stagnant growth, the dynamics of the universe change, such that energy rebuilds to fuel another bang. What is the change? This is where even Steinhardt agrees that the model gets quite strange. Borrowing from a branch of physics known as string theory, the cosmologists propose that the universe as we know it is really a surface in a higher-dimensional space. In Steinhardt's words: "We're stuck like flies on fly paper to move only in our own dimension." In his cyclic model, there is a second surface, like the second piece of bread in a sandwich, that we can't touch, feel or see. The surfaces are called membranes, or "branes" for short. The branes can move in two ways: They can stretch, remaining a fixed distance apart; and they can smash together and come apart again. They cannot be smashed together at the same time they're being stretched. Matter and radiation cause branes to stretch. When they have stretched so far that the universe is emptied of its matter and radiation, the branes smash together. The collision of surfaces creates more matter and radiation. The cycle begins anew. By Albrecht's analysis, the collision is a weak point in the model. "The (mathematical) equations they're using don't include any detail about the inside of the branes, so to speak," he said. "So they just have to make a wish basically, and say, I hope that when they collide, it comes out in this particular way."
