With Airbus’ giant A380 airliner about to take to the skies, you might think planes could not get much bigger-and you would be right. For a given design, it turns (1) , there comes a point where the wings become too heavy to generate (2) lift to carry their own weight. (3) a new way of designing and making materials could (4) that problem. Two engineers (5) University College London have devised all innovative way to customise and control the (6) of a material throughout its three-dimensional structure.
In the (7) of a wing, this would make possible a material that is dense, strong and load-bearing at one end, close to the fuselage, (8) the extremities could be made less dense, lighter and more (9) . It is like making bespoke materials, (10) you can customise the physical properties of every cubic millimetre of a structure.
The new technique combines existing technologies in a(n) (11) <
A. as
B. since
C. because
D. so long as
Assuming that the engineering problems could be overcome, the production of a time machine could open up a Pandora’s box of causal paradoxes. Consider, for example, the time traveler who visits the past and murders his mother when she was a young girl. How do we make sense of this If the girl dies, she cannot become the time traveler’s mother. But if the time traveler was never born, he could not go back and murder his mother.
Paradoxes of this kind arise when the time traveler tries to change the past, which is obviously impossible. But that does not prevent someone from being a part of the past.
Suppose the time traveler goes back and rescues a young girl from murder, and this girls grows up to become his mother. The causal loop is now self-consistent and no longer paradoxical. Causal consistency might impose restrictions on what a time traveler is able to do, but it does not rule out time travel per second.
Even if time travel isn’t st
A. the speed of time travel
B. the relationship between people
C. the destination of time travel
D. the length of time travel
（用户名：22；账套：705；操作日期：2014年1月31日）打开考生文件夹下的“资产负债表.rep”，完成下列操作后，将报表以原文件名进行保存。设置E9单元格的计算公式。
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