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Witnesses to a meteor in Australia in 1978 claimed to have heard strange noises as it streaked overhead. Yet, given that the meteor was 30 kilometers up, if these sounds had come directly from the meteor, people on the ground could not have heard them until almost a minute after the meteor had disappeared. Physicist Colin Keay hypothesized that the light given off by a meteor’s trail must be accompanied by invisible electromagnetic radiation in the form of very low frequency (VLF) radio waves. Such waves, which travel at the speed of light, would reach the observer when the meteor itself came into view.
Subsequent experiments in a soundproof chamber showed that many things can act as transducers to convert VLF waves into audible vibrations. Aluminum foil, thin wires, pine needles, or dry hair all responded to a VLF field. VLF waves induce small charges in such objects, thereby causing them to vibrate in time with the waves’ oscillation. This transducer effect would explain why some people heard the noises while others close by heard nothing. Those who heard sounds were simply nearer to transducers. It could also explain why attempts to record meteor sounds have failed: scientists carefully place their microphones away from possible sources of interference.
[填空 ]真题1300题 -8954
Having an intense and long-standing culture of (i)_____, the company understandably has a reputation as the supreme corporate (ii)_____. But even by these standard, the degree of secrecy surrounding the company’s most recent research is (iii)_____.
[阅读&逻辑 ]经典真题300篇 -8953
According to the passage, the “shifting-baseline syndrome” is a result of which of the following?
[阅读&逻辑 ]经典真题300篇 -8952
Which of the following is an assumption on which the argument depends?
[阅读&逻辑 ]经典真题300篇 -8951
According to the passage, Sinodonty and Sundadonty differ from one another in that Sinodonty
[阅读&逻辑 ]经典真题300篇 -8950
The passage implies that Turner’s conclusion regarding the origins of most Native American populations is based in part on which of the following findings?
[阅读&逻辑 ]经典真题300篇 -8949
In the argument given, the two highlighted portions play which of the following roles?
[阅读&逻辑 ]经典真题300篇 -8948
In the context in which it appears, “appreciation of” most nearly means
[阅读&逻辑 ]经典真题300篇 -8947
According to the passage, critics approach Jane Austen’s work in biographical or historical ways for which of the following reasons?
[阅读&逻辑 ]经典真题300篇 -8946
Which of the following can be inferred regarding the case of Baker v. Carr?
[阅读&逻辑 ]经典真题300篇 -8945
The author of the passage uses the analogy of the archaeology most probably in order to
[阅读&逻辑 ]经典真题300篇 -8944
It can be inferred that the author of the passage would agree with which of the following claims about The Cry?
[阅读&逻辑 ]经典真题300篇 -8943
The passage presents which of the following as evidence in favor of Fielding and Collier’s having collaborated in writing The Cry?
[阅读&逻辑 ]经典真题300篇 -8942
Which of the following, if true, most strongly supports the proposed explanation?
[阅读&逻辑 ]经典真题300篇 -8941
Which of the following most logically completes the argument?
[阅读&逻辑 ]经典真题300篇 -8940
The primary purpose of the passage is to
[阅读&逻辑 ]经典真题300篇 -8939
Which of the following, if true, most logically completes the argument?
[阅读&逻辑 ]经典真题300篇 -8938
Which of the following can be inferred about the studies mentioned in the highlighted portion of the passage?
[阅读&逻辑 ]经典真题300篇 -8937
In the context in which it appears, “ordered” most nearly means
[阅读&逻辑 ]经典真题300篇 -8936
According to the passage, which of the following statements about ant interactions is true?
[阅读&逻辑 ]经典真题300篇 -8935
The author of the passage mentions conservatives in the highlighted sentence primarily in order to