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 strictly paradoxical, it is certainly weird. Consider the time traveler who leaps ahead a year and reads about a new mathematical theorem in a future edition of Scientific American. He notes the details, returns to his own time and teaches the theorem to a student, who then writes it up for Scientific American. The article is, of course, the very one that the time traveler reads. The question then arises: Where did the information about the theorem come from? Not from the time traveler, because he read it, but not from the student either, who learned it from the time traveler. The information seemingly came into existence from nowhere, reasonlessly.
The bizarre consequences of time travel have led some scientists to reject the notion outright. Stephen W. Hawking of the University of Cambridge has proposed a "Chronology protection conjecture," which would outlaw causal loops. Because the theory of relativity is known to permit causal loops, chronology protection would require some other factors to intercede to prevent travel into the past. What might this factor be? One suggestion is that quantum processes will come to the rescue. The existence of a time machine would allow particles to loop into their own past. Calculations hint that the ensuring disturbance would become self-reinforcing, creating a runaway surge of energy that would wreck the wormhole.
The first paragraph intends to show ______.
A.the time machine in the future would be feasible
B.the time machine in the future is just like the Pandora's ox
C.the time machine in the future is still doubtful
D.the time machine in the future might cause murder
第1题
井下供电网路中,()应装设局部接地极。
A.低压电力电缆接线盒
B.高压电力电缆接线盒
C.低压配电点
D.采区变电所
E.移动变电站
F.检漏继电器
G.装有电气设备的硐室
第4题
A. 采区变电所(包括移动变电站和移动变压器)。
B. 装有电气设备的硐室和单独装设的高压电气设备。
C. 煤电钻综保、照明信号综保
D. 无低压配电点的采煤机工作面的运输巷、回风巷、集中运输巷_胶带运输巷_以及由变电所单独供电的掘进工作面,至少应分别设置1个局部接地极。
E. 连接高压动力电缆的金属连接装置。
F . F、低压配电点或装有3台以上电气设备的地点。
第5题
A.采区变电所(包括移动变电站和移动变压器)
B.装有电气设备的硐室和单独装设的高压电气设备
C.低压配电点或装有3台以上电气设备的地点
D.无低压配电点的采煤工作面的运输巷、回风巷、胶带运输巷以及由变电所单独供电的掘进工作面,至少应分别设置1个局部接地极
E.连接高压动力电缆的金属连接装置
第6题
井下主接地极装设在()
A.井底车场水仓中
B.中央井下变电所内
C.井下采区变电所内
D.采区工作面
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