四级练习2011.12.30
[audio]http://sound.yywz123.com/tingbbs/cet4/cet420111230.mp3[/audio]All that we really need to plot out the future of our universe are a few good measurements.This does not mean that we can sit down today and outline the future course of the universe with anything like certainty.(1)_______________________.But we do know exactly what information we need to fill in our knowledge,and we have a pretty good idea of how to go about getting it.Perhaps the best way to think of our present situation is to imagine a train coming into a switchyard.All of the switches are set before the train arrives,so that its path is completely determined.Some switches we can see,others we cannot.There is no doubt if we can see the setting of a switch:we can say with confidence that some possible futures will not be realized and others will.At the unseen switches,however,there is no such certainty about it.We know the train will take one of the tracks leading out, but we have no idea which one.(2)_______________________.When we think about the future of the universe, we can see our many billions of years into the future, but after that there are decision points to be dealt with and possible fates to consider.The goal of science is to reduce the vagueness at the decision points and find the true road that will be followed.
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