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To: PatrickHenry

Noted physicists have speculated that in a collapsing universe, "time" would run backwards, reversing the cause-effect relationships that we experience.


888 posted on 08/21/2005 6:31:30 AM PDT by GregoryFul
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To: GregoryFul
Noted physicists have speculated that in a collapsing universe, "time" would run backwards, reversing the cause-effect relationships that we experience.

Yes. But Hawking, for one, has rejected the idea:

As I said, I thought at first that the no boundary condition did indeed imply that disorder would decrease in the contracting phase. I was misled partly by the analogy with the surface of the earth. If one took the beginning of the universe to correspond to the North Pole, then the end of the universe should be similar to the beginning, just as the South Pole is similar to the North. However, the North and South Poles correspond to the beginning and end of the universe in imaginary time. The beginning and end in real time can be very different from each other. I was also misled by work I had done on a simple model of the universe in which the collapsing phase looked like the time reverse of the expanding phase. However, a colleague of mine, Don Page, of Penn State University, pointed out that the no boundary condition did not require the contracting phase necessarily to be the time reverse of the expanding phase. Further, one of my students, Raymond Laflamme, found that in a slightly more complicated model, the collapse of the universe was very different from the expansion. I realized that I had made a mistake: the no boundary condition implied that disorder would in fact continue to increase during the contraction. The thermodynamic and psychological arrows of time would not reverse when the universe begins to recontract, or inside black holes.
Source: A brief history of time, chapter 9.
890 posted on 08/21/2005 9:45:46 AM PDT by PatrickHenry (Felix, qui potuit rerum cognoscere causas. The List-O-Links is at my homepage.)
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