填空题

All that we really need to plot out the future of our universe are a few good (36) . This does not mean that we can sit down today and (37) the future course of the universe with anything like (38) . There are still too many things we do not know about the way the universe is put together. But we do know exactly what information we need to fill in our knowledge, and we have a (39) good idea of how to go about getting it. Perhaps the best way to think of our present situation is to (40) a train coming into a switchyard (调车场). All of the (41) are set before the train arrives, so that its path is completely determined. Some switches we can see, others we cannot. There is no (42) if we can see the setting of a switch: We can say with (43) that some possible futures will not materialize and others will. At the unseen switches, however, there is no such certainty. (44) .The unseen switches are the true decision points in the future. (45) . When we think about the future of the universe, we can see our "track" many billions of years into the future, but after that there are decision points to be dealt with and possible fates to consider. (46) .